Method for torque control of an internal combustion engine, and internal combustion engine

Abstract

A method for torque control of an internal combustion engine includes a pressure sensor that is associated with at least one, but at the most two cylinders of the internal combustion engine, whereby an cylinder internal pressure for the cylinder associated with the pressure sensor is detected. The method carries out an adjustment of injection characteristics for the injectors allocated to the individual cylinders of the internal combustion engine by way of a method which is independent from the detected cylinder pressure. A torque control for the internal combustion engine is performed based on the detected cylinder pressure.

Claims

1. An internal combustion engine having a plurality of cylinders, wherein: at least one pressure sensor is assigned to between one and two of said plurality of cylinders; said internal combustion engine having an engine control unit, said engine control unit implementing a series of steps, said series of steps comprising: detecting an internal cylinder pressure for said between one and two cylinders of said internal combustion engine using said at least one pressure sensor; adjusting a number of injectors assigned to a number of said plurality of cylinders of said internal combustion engine to be equal in regard to their injection behavior independently from said detected internal cylinder pressure; and performing a torque control of said internal combustion engine on the basis of said detected internal cylinder pressure.

2. The internal combustion engine according to claim 1, wherein: said internal combustion engine is designed as a V-engine, having two V-shaped cylinder banks arranged at an angle relative to each other, each cylinder bank including precisely one cylinder to which a pressure sensor is assigned.

3. The internal combustion engine according to claim 1, wherein: a pressure sensor is assigned to precisely one cylinder of said internal combustion engine.

4. A method for torque control of an internal combustion engine, including the steps of: assigning at least one pressure sensor to between one and two cylinders of said internal combustion engine; detecting an internal cylinder pressure for said between one and two cylinders of said internal combustion engine using said at least one pressure sensor; adjusting a number of injectors assigned to a number of cylinders of said internal combustion engine to be equal in regard to their injection behavior independently from said detected internal cylinder pressure; and performing a torque control of said internal combustion engine on the basis of said detected internal cylinder pressure.

5. The method according to claim 4, wherein: said internal combustion engine being a V-engine, said V-engine having two cylinder banks arranged at an angle relative to each other, each of said cylinder banks having exactly one cylinder to which one pressure sensor is assigned.

6. The method according to claim 4, wherein: exactly one pressure sensor is used.

7. The method according to claim 4, wherein: said step of adjusting a number of injectors assigned to a number of cylinders of said internal combustion engine to be equal in regard to their injection behavior further comprises the sub-steps of: turning off one of said number of injectors; capturing a crank angle signal from said internal combustion engine; converting said crank angle signal into a frequency range using a discrete Fourier transformation; capturing and storing an amount of a harmonic of the 0.5th order of said Fourier transformation of said crank angle signal; assigning said amount to said turned off injector; turning on said turned off injector; performing each previous sub-step in a sequential manner for each injector of said internal combustion engine; creating a mean value of said stored amounts over all of said injectors; and correcting a control of said injectors based on a deviation of said amount from said mean value assigned to an injector that is to be corrected.

8. The method according to claim 4, further comprising the steps of: calculating for each said injector a differential amount as a difference from an amount assigned to each said injector which is detected and stored when all of said injectors are turned on and an amount when said injector is turned off; and using said differential amounts assigned to each said injector as basis for creating a mean value and also for a correction.

9. The method according to claim 4, wherein: control of said number of injectors is corrected, in that an energizing duration for each of said number of injectors is adjusted.

10. The method according to claim 9, wherein: said energizing duration for each of said number of injectors is adjusted such that an energizing duration differential is added onto a current energizing duration, said energizing duration differential being calculated according to the following formula:
BD[i]=(MWamount[i])*K, wherein: BD[i] signifies said energizing duration differential for an injector [i]; MW signifies a mean value calculated from differential amounts between amounts of a harmonic of the 0.5th order that are assigned to each of said number of injectors; amount[i] is a determined differential amount for injector [i]; and K is a constant; said formula being used under condition BD[i]=0.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing, wherein:

(2) FIG. 1 illustrates a flow chart showing one embodiment of the method for injector equalization.

(3) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring now to FIG. 1, the method starts in step 1, after which in step 3 a number of the cylinders of the internal combustion engine is initially identified. The embodiment of the method illustrated in the drawing provides that exactly one injector is assigned to each cylinder. Therefore, the number of cylinders is consistent with the number of injectors. It is nevertheless possible in another embodiment of the method that the internal combustion engine includes more than one injector per cylinder. In this case, the number of injectors may be identified in step 3, not the number of cylinders. In step 3 a running variable i is also defined and initialized, whereby it may be assigned value of 0.

(5) In a retrieval step 5, the current value of the running variable i is compared with the number of cylinders that are identified in step 3. For the sake of illustration, it is assumed that the running variable is initialized with a value of 0, so that value 0 of running variable i is also assigned to the first injector for which the method is performed. In another embodiment, the running variable may be initialized with another value, for example value 1. Accordingly, in retrieval step 5, if running variable i is initialized with value 0, it is verified whether the value of the running variable is less than the number of cylinders identified in step 3. If this is the case, the method proceeds to a step 7 where the injector to which the current value of running variable i is assigned is turned off.

(6) Subsequently in step 9 an amount or differential amount of the harmonic of the 0.5.sup.th order of the Fourier transformation of the crank angle signal is captured and stored and assigned to the turned off injector. In step 11 the value of running variable i is increased by one. At the same time, the turned off injector is turned on again. The method returns then to retrieval step 5 where it is again verified whether the now current value of running variable i is still less than the number of cylinders. In this manner a loop 13 is cycled a number of times until an amount or differential amount has been captured for all injectors in step 9, sequentially one after the other. A value of running variable i that is consistent with the number of cylinders reduced by one is thereby assigned to the last injector. Therefore, after capture of the amount or differential amount for the last injector in step 9, the value of the running variable is increased to a value which is consistent with the number of cylinders. If this is detected in retrieval step 5 the method proceeds on to step 15.

(7) Here, the value of running variable i is again initialized, and in particular with the herein discussed embodiment of the method set to 0. In a subsequent step 17 a mean value is created from the captured and stored amounts or differential amounts for the individual injectors. The method subsequently enters into retrieval step 19 where it is again verified whether the actual value of running variable i is less than the number of cylinders identified in step 3. If this is the case the method proceeds to step 21 where a correction in the control of the injector to which the current value of running variable i is assigned is performed. This may occur on the basis of a differential amount relating to an amount determined for the normal operation of the internal combustion engine assigned to the only turned off injector, as well as on the basis of a mean value of the differential amounts for the individual injectors. An energizing duration for the injector may be adjusted, whereby an energizing duration difference is added to the actual current energizing duration. The energizing duration difference may thereby be calculated according to the aforementioned equation (1), and applied according to the aforementioned conditions (2).

(8) In subsequent step 23 the value of running variable i is again increased by one. The method then reverts to retrieval step 19, so that a loop 25 is realized. This loop is again cycled through until a correction has been performed for all injectors, or respectively until the value of running variable i in retrieval step 19 is consistent for the first time with the number of cylinders identified in step 3. This is because in the selected embodiment of the method, wherein running variable i is initialized with 0, a value is assigned to the last injector that is to be corrected which, compared to the number of cylinders is reduced by one. If, in retrieval step 19 the value of running variable i is for the first time identical to the number of cylinders identified in step 3, then the method concludes in a step 27. The correction of the energizing duration in step 21 for the cylinder to which the current value of running variable i is assigned is preferably only performed if a deviation of the amount or a differential amount from the median value exceeds a predetermined threshold value. Otherwise no correction for the injector is performed and the method proceeds to step 23.

(9) The process may be iterated, in other words returns, if applicable after a predefined waiting period, from step 27 to step 1, wherein this iteration or respectively a loop provided between steps 27 and 1 which is not shown in the drawing is cycled until the deviations of the individual amounts or differential amounts for the individual injectors from the mean value are smaller than a predefined threshold value. It is hereby possible that this threshold value is identical to the threshold value which is selected for the decision whether a correction of an individual injector is to be performed. It is however also possible, as a condition to stop iteration of the entire process, to provide a threshold value that deviates from this threshold value which can be larger or smaller than the threshold value for the correction of the individual injectors.

(10) Overall it is shown that with the assistance of the method for injector equalization, a very precise equalization of injectors, in particular in larger engines and especially during running operation under load or no-load operation, is readily possible, so that the individual injectors inject substantially the same amount of fuel. For this reason pre-injection and/or after-injection are also possible in the internal combustion engine. In regard to torque control it has been shown that this can be performed simply and cost effectively, in that at most two, and possible only one cylinder pressure sensor is used. Due to the reliable equalization of the injectors it is possible to bring peak pressures of the cylinders closer to a maximum permissible limit, resulting in greater engine efficiency without the risk of damaging the engine. This has a positive effect on the life span of the internal combustion engine. In torque adjustment a torque of the internal combustion engine is determined preferably on the basis of the captured internal cylinder pressure. This is compared with a load-point dependent predefined target torque and adjusted by way of a control algorithm, by increasing the fuel amounts injected by the injectors if the actual torque deviates downward from the target torque, and whereby the injected fuel amounts are decreased if the actual torque deviates upward from the desired target torque. In doing so, the target torques for the internal combustion engine are recorded in a characteristic diagram for all load points.

(11) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.