Method for operating an internal combustion engine

Abstract

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.

Description

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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of an internal combustion engine having two final controlling devices for influencing a flow cross-section of an intake duct.

FIG. 2 shows a diagram in which characteristic curves of position sensors of a final controlling device from FIG. 1 are plotted.

FIG. 3 shows a flow chart of a method for operating the two final controlling devices in FIG. 1.

FIG. 4 shows a flow chart of a method for identifying a defective position sensor of one of the final controlling devices in FIG. 1.

FIG. 5 shows a flow chart of a method for performing a function test of one of the final controlling devices in FIG. 1.

FIG. 6 shows a representation of the process scheme in FIG. 3 in greater detail.

DETAILED DESCRIPTION

An internal combustion engine is labeled in its entirety with reference numeral 10 in FIG. 1. It is used to drive a motor vehicle (not shown). Internal combustion engine 10 has two cylinder banks 12a and 12b, each of which has four cylinders and four combustion chambers 14a through 14d and 14c through 14h. These cylinder banks 12a and 12b are positioned relative to each other in the shape of a vee. The internal combustion engine 10 shown in FIG. 1 is therefore a V8-engine.

Combustion air is supplied to cylinders 14 of internal combustion engine 10 via an intake duct, an intake manifold 16 in this case. An air filter 18 is provided at the end of intake manifold 16 facing away from combustion chambers 14. Downstream of air filter 18, intake manifold 16 is divided into two control sections 20a and 20b which are parallel to each other. One final controlling device 22a and 22b, 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 section 20a and/or 20b, as explained below in greater detail.

An intake manifold divider 24 is provided in intake manifold 16 downstream of control sections 20a and 20b, the intake manifold divider dividing intake manifold 16 into two intake manifold sections 26a and 26b, each allocated to one cylinder bank 12a and 12b, respectively. A manifold 28a and/or 28b further divides the air stream among the individual combustion chambers 14a through 14d and 14e through 14h.

Final controlling devices 22a and 22b are identical in design. For the sake of simplicity, the design of only final controlling device 22a will be discussed in greater detail below: It includes a final controlling element 30a configured as a throttle valve, which is movable into any position by an activating device 32a. A fully closed position of throttle valve 30a is defined by a “lower mechanical” stop 34a. A stop is also provided for the fully open position, although it is not shown in the figure. Two springs 36a and 38a act on throttle valve 30a, by way of which throttle valve 30a is brought into a neutral position (the “limp-home air position”) if activating device 32a is 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 valve 30a is detected by two position sensors 40a and 42a; in this case, they are potentiometers, one each of which is coupled to a throttle valve. As shown in FIG. 2, the characteristic curves of position sensors 40a and 42a, which link a signal voltage u1a (position sensor 40a) and u2a (position sensor 42a) with an angle iw, are mirror images of each other.

Position sensors 40a and 42a supply corresponding signals to a control and regulating system 44, which outputs corresponding triggering signals to the activating device 32a. 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 valve 30a. In this process, only one single setpoint value is generated in a setpoint value generator 46 for both final controlling devices 22a and 22b in the control and regulating system, namely as a function of the position of a gas pedal 48, among other things. The total air mass flowing through intake duct 16 is detected by an HFM sensor 50, which also delivers corresponding signals to control and regulating system 44.

The operation of an internal combustion engine 10 will now be explained in greater detail with reference to FIG. 3:

The use of a single setpoint value wdks for activating throttle valves 30a and/or 30b is identical for both final controlling devices 22a and/or 22b. For the sake of simplicity, only the procedure for final controlling device 22a and/or throttle valve 30a will therefore be described below.

Setpoint variable wdks is supplied to a block 52a, to which an actual value iwa is also supplied, by an actual value generator 54a. In turn, voltage signals u1a and u2a, which are provided by potentiometers 40a and 42a, are supplied to the actual value generator. To this end, the current and mirror-symmetric characteristic curves of position sensors 40a and 42a are stored in actual value generator 54a. The characteristic curves are generated in a manner described in greater detail below.

Block 52a contains a position controller for throttle valve 30a, which is designed as a PID controller. Errors in the triggering circuit are also diagnosed in block 52a, however. The position controller contained in block 52a outputs 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 block 52a, 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 sensors 40a and 42a are supplied to actual value generator 54a. Actually, however, only signal u1a from position sensor 40a is normally used to generate the actual value; actual angle iwa is thus equal to value iw1a obtained from the characteristic curve. Signal u2a from position sensor 42a is used to check signal u1a from position sensor 40a and is used when signal u1a has been recognized as being erroneous. This check takes place specifically as follows (see FIG. 4):

After a start block 56, the absolute value of the difference between actual values iw1a and iw2a is formed in 58; the difference is obtained from voltage signals u1a and u2a from position sensors 40a and 42a. If this amount is less than a limiting value G1, that is, if both position sensors 40a and 42a indicate positions of throttle valve 30a that are essentially identical, it is assumed that the signals which were supplied are correct. In this case, signal u1a from position sensor 40a and the corresponding characteristic curve are used to form actual value iwa, and the process jumps back to the input of block 58 (i.e., this check is carried out continually). The basis thereof is the consideration that it is unlikely that both position sensors 40a and 42a indicate an identical position of the throttle valve 30a if an error occurs, despite their having characteristic curves which run in opposite directions.

If the result of block 58 is “no,” however, total air mass mHFM which flows through intake duct 16 is first determined in block 60 based on the signal from HFM sensor 50. Furthermore, air mass m40b flowing through control section 20b is determined from voltage signal u1b from position sensor 40b which is allocated to second throttle valve 30b, which has not yet been discussed explicitly (an angle is first determined from signal u1b, and from this, the corresponding mass flow m40b is then determined). It is assumed here that it is unlikely that position sensors 40b and 42b of second final controlling device 22b also 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 section 20a. Furthermore, the corresponding air masses miw1a and miw2a (one of which must be erroneous, based on the results of the query in block 58) are determined from signals u1a and u2a of position sensors 40a and 42a and the positions (angles) of throttle valve 30a determined from the signals.

A check is now run in block 62 to determine which of the two air masses miw1a or miw2a determined based on signals u1a and u2a best 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 miw1a determined based on signal u1a of position sensor 40a is greater than the difference between correct air mass ma and air mass miw2a determined based on signal u2a of position sensor 42a. If the answer in block 62 is “yes,” this means that sensor 40a is supplying an erroneous signal (block 64). If the answer in block 62 is “no,” this means that position sensor 42a is supplying an erroneous signal (block 66). In the first case, the characteristic curve of position sensor 42 and/or value iw2a is used immediately to form actual value iwa. The procedure ends in block 68.

As mentioned above, the characteristic curves used in actual value generator 54a are updated continually. To this end, the current slopes of the characteristic curves and the voltage values of a defined position of throttle valve 30a are repeatedly made available to actual value generator 54a. They are made available in a learning and test block 70a. In the learning and test block, activating device 32a is activated in certain operating situations of internal combustion engine 10 in such a way that throttle valve 30a definitely rests against stop 34. An operating situation of this type is present, for instance, when the operator turns on the ignition of internal combustion engine 10 but the engine does not start right away.

When throttle valve 30a rests against stop 34, the corresponding voltage values of position sensors 40a and 42a are detected and stored. Activating device 32a is then de-energized, so that throttle valve 30a moves into the neutral position defined by the two clamping devices 36a and 38a, and the voltage values of the two position sensors 40a and 42a are 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 block 52a to enable the most precise pilot control of throttle valve 30a possible.

Another test is carried out in learning and test block 70a. For example, if an error is detected in an actual value amplification, the operational reliability of springs 36a and 38a is checked, and throttle valve 30a is checked for smoothness of movement and/or “sticking”. The latter will now be explained with reference to FIG. 5:

After a start block 72, the two throttle valves 30a and 30b are moved into a defined position POS1 in block 74. In block 76, the signals from position sensors 40a and 42a and/or 40b and 42b are used to check whether the two throttle valves 30a and 30b have reached position POS1. If they have not, activation of activating devices 32 and/or 32b continues. It may be assumed that, due to manufacturing differences, throttle valves 30a and 30b do not reach position POS1 absolutely simultaneously. In the current method, however, in block 78, activating devices 32a and 32b are not de-energized (block 78) until the “slower” of the two throttle valves 30a or 30b has reached position POS1.

Time t1 is detected for throttle valve 30a and time t2 is detected for throttle valve 30b, the time being the period of time that elapses until the particular throttle valve 30a or 30b reaches the neutral position (also referred to as the “limp-home air position”) defined by springs 36a and 38a. The corresponding time values t1 and t2 are detected in block 80 of FIG. 5.

A check is carried out in block 82 to determine whether the detected time values t1 and t2 are less than a limiting value G2. If one of the time values t1 or t2 reaches at least limiting value G2, this means that the corresponding throttle valve 30a or 30b does not move as smoothly as desired, or that one of the springs 36 or 38 is broken. A corresponding error message ERR1 or ERR2 is therefore generated in block 84. If the answer in block 82 is “yes,” however, another check is carried out in block 82 to determine whether the absolute value of the difference between times t1 and t2 is less than a limiting value G3. In this manner, wear on one side of a throttle valve 30a or 30b may be detected. Depending on the result of the query in block 86, an error message ERR3 is generated in block 88, or the process jumps to End block 90.

As shown in FIG. 3, the different error states which are generated in the tests carried out in blocks 54a and 70a (and for throttle valve 30b in blocks 54b and 70b) are supplied to a response block 92. Depending on the type of error which is present, corresponding response procedures react1, react2, etc. (block 94) are implemented in response block 92. Identical error types occurring in the two final controlling devices 22a and 22b are gated in block 92 using a logical “or.” If the error is present in only one final controlling device 22a or 22b, 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 valves 30a and 30b are being brought into the neutral position, or that internal combustion engine 10 has been brought to a standstill because fuel supply or fuel injection has been switched off.

As further shown in FIG. 6, a separate status memory 94a or 94b is provided for each final controlling device 22a and/or 22b, in which current status information regarding final controlling devices 22a and 22b and their components, e.g., final controlling elements 30, activating devices 32, springs 26 and 28, and position sensors 40 and 42 are stored. The two status memories 94a and 94b may be read out using a corresponding diagnostic tool during service of internal combustion engine 10.

Claims

1. A method for operating an internal combustion engine, comprising: supplying a combustion air to at least one combustion chamber via at least one intake duct that includes at least two parallel control sections to each of which one final controlling device is allocated, and by which the flow cross-section of the particular control section is able to be influenced; and activating at least two final controlling devices based on one single setpoint variable.

2. The method as recited in claim 1, wherein each final controlling device has its own closed-loop position control to which the same setpoint variable is supplied.

3. The method as recited in claim 2, wherein 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 a plausibility of signals from the position sensors is monitored.

4. The method as recited in claim 3, further comprising: if an error occurs, determining which of the position sensors is defective by forming one value each for a partial air-mass flow from the signals of the position sensors of all final controlling devices; and checking for plausibility the determined values for the partial air-mass flow with reference to a value for a measured total air-mass flow.

5. The method as recited in claim 1, wherein: the final controlling devices each include one clamping device, each of which is able to hold the final controlling element of a respective final controlling device in a neutral position, and an activating device which is able to move the final controlling element out of the neutral position, to perform a function test, the activating devices of the final controlling devices are activated in such a way that the final controlling elements move into a test position when the final controlling elements are in the test position, activation is ended and a period of time required for the final controlling elements to move from the test position into the neutral position is detected.

6. The method as recited in claim 5, wherein the function test is carried out in separate test blocks for each final controlling device, the test blocks being coordinated with each other.

7. The method as recited in claim 1, wherein, in certain operating situations of the internal combustion engine, instantaneous properties of a final controlling device are detected independently of another final controlling device and are made available for the activation.

8. The method as recited in claim 1, wherein status information about a final controlling device and its components is stored independently of another final controlling device.

9. The method as recited in claim 1, wherein error information is evaluated jointly for all final controlling devices and corresponding responses are triggered.

10. The method as recited in claim 9, wherein identical error information of the final controlling devices is gated using a logical “or.”

11. A computer program that when executed results in a performance of the following: supplying a combustion air to at least one combustion chamber via at least one intake duct that includes at least two parallel control sections to each of which one final controlling device is allocated, and by which the flow cross-section of the particular control section is able to be influenced; and activating at least two final controlling devices based on one single setpoint variable.

12. An electrical memory medium for at least one of a control and regulating system of an internal combustion engine, the electrical memory medium storing a computer program that when executed results in a performance of the following: supplying a combustion air to at least one combustion chamber via at least one intake duct that includes at least two parallel control sections to each of which one final controlling device) is allocated, and by which the flow cross-section of the particular control section is able to be influenced; and activating at least two final controlling devices based on one single setpoint variable.

13. A control and/or regulating system for an internal combustion engine programmed to execute the following steps: supplying a combustion air to at least one combustion chamber via at least one intake duct that includes at least two parallel control sections to each of which one final controlling device) is allocated, and by which the flow cross-section of the particular control section is able to be influenced; and activating at least two final controlling devices based on one single setpoint variable.

14. An internal combustion engine, comprising: a control and/or regulating system for an internal combustion engine programmed to execute the following steps: supplying a combustion air to at least one combustion chamber via at least one intake duct that includes at least two parallel control sections to each of which one final controlling device) is allocated, and by which the flow cross-section of the particular control section is able to be influenced; and activating at least two final controlling devices based on one single setpoint variable.