Method for ascertaining an accuracy of a torque transmitted by a belt-driven starter generator of an internal combustion engine to the internal combustion engine

Abstract

A method for ascertaining an accuracy of a torque transmitted by a belt-driven starter generator of an internal combustion engine to the internal combustion engine, the method being similar to a learning operation or a calibration of the actual torque of the starter generator with respect to a setpoint torque, includes: in an idling instance of the internal combustion engine, controlling the belt-driven starter generator to transmit a specified test torque to the internal combustion engine and decreasing the torque of the internal combustion engine by the specified test torque; determining and evaluating a speed variable, which is a function of a speed of the internal combustion engine; and deducing the torque accuracy from the evaluated speed variable.

Claims

1. A method for controlling a belt-driven starter generator of an internal combustion engine, the method comprising: in an idling instance of the internal combustion engine: controlling, by a processor, the belt-driven starter generator to provide to the internal combustion engine a specified test torque; and controlling, by the processor, the internal combustion engine to decrease an actual torque of the internal combustion engine by the specified test torque; determining, by a processor, a speed variable that is a function of a speed of the internal combustion engine resulting from the controlling of the belt-driven starter generator and of the internal combustion engine by the processor; evaluating, by the processor, the speed variable; deducing, by the processor and from the evaluation, a torque accuracy at which the belt-driven starter generator provides torque to the internal combustion engine relative to setpoints specified by the processor; and based on the deduced torque accuracy, the processor controlling the belt-driven starter generator.

2. The method of claim 1, wherein the deduced torque accuracy is insufficient and the controlling based on the deduced torque accuracy includes correcting the torque transmitted by the belt-driven starter generator.

3. The method of claim 1, wherein in the course of the evaluation of the speed variable, it is determined if one of: the speed of the internal combustion engine remains constant and if the speed of the internal combustion engine deviates from a specified reference value.

4. The method of claim 3, wherein, in the course of the evaluation of the speed variable, it is determined that one of the speed of the internal combustion engine does not remain constant and the speed of the internal combustion engine deviates from the specified reference value, responsive to which determination an insufficient torque accuracy is deduced.

5. The method of claim 1, wherein a statistical evaluation of a plurality of determined speed variables is carried out.

6. The method of claim 5, wherein a time series analysis of the plurality of determined speed variables is carried out.

7. The method of claim 1, wherein the evaluated speed variable is checked for plausibility with the aid of statistical functions.

8. The method of claim 1, wherein the speed of the internal combustion engine is determined as a speed variable and is evaluated.

9. A non-transitory computer-readable medium on which are stored instructions that are executable by a processor and that, when executed by the processor, cause the processor to perform a method for controlling a belt-driven starter generator of an internal combustion engine, the method comprising: in an idling instance of the internal combustion engine: controlling the belt-driven starter generator to provide to the internal combustion engine a specified test torque; and controlling the internal combustion engine to decrease an actual torque of the internal combustion engine by the specified test torque; determining a speed variable that is a function of a speed of the internal combustion engine resulting from the controlling of the belt-driven starter generator and of the internal combustion engine by the processor; evaluating the speed variable; deducing, from the evaluation, a torque accuracy at which the belt-driven starter generator provides torque to the internal combustion engine relative to setpoints specified by the processor; and based on the deduced torque accuracy, controlling the belt-driven starter generator.

10. A device for controlling a belt-driven starter generator of an internal combustion engine, the device comprising: processing circuitry interfacing with the belt-driven starter generator and with the internal combustion engine, wherein the processing circuitry is configured to: in an idling instance of the internal combustion engine: control the belt-driven starter generator to provide to the internal combustion engine a specified test torque; and control the internal combustion engine to decrease an actual torque of the internal combustion engine by the specified test torque; determine a speed variable that is a function of a speed of the internal combustion engine resulting from the controlling of the belt-driven starter generator and of the internal combustion engine by the processor; evaluate the speed variable; deduce, from the evaluation, a torque accuracy at which the belt-driven starter generator provides torque to the internal combustion engine relative to setpoints specified by the processor; and based on the deduced torque accuracy, control the belt-driven starter generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a belt drive of a motor vehicle, which includes an internal combustion engine and a belt-driven starter generator and which is configured to implement a method according to an example embodiment of the present invention.

(2) FIG. 2 is a flowchart that illustrates a method according to an example embodiment of the present invention.

(3) FIG. 3 schematically shows graphs of torques of an internal combustion engine and of a belt-driven starter generator, plotted versus time, as well as graphs of a speed of an internal combustion engine, plotted versus time, which can be determined in the course of execution of a method according to an example embodiment of the present invention.

DETAILED DESCRIPTION

(4) In FIG. 1, a belt drive of a motor vehicle is schematically represented and denoted by 100. An internal combustion engine 110 of the motor vehicle includes a crankshaft, which is connected to a driven crankshaft wheel 150 in a rotatably fixed manner. Driven crankshaft wheel 150 takes the form of a belt pulley, for example.

(5) Internal combustion engine 110 is connected to a belt-driven starter generator 130 via a belt 120, for example, via a ribbed v-belt, so as to be able to transmit a torque. Belt 120 engages, in particular, in a force-locked and/or form-locked manner, with driven crankshaft wheel 150 and with a drive wheel 131 of starter generator 130. Drive wheel 131 is connected to a rotor of starter generator 130 in a rotatably fixed manner. Internal combustion engine 110 can be connected by belt 120 to further components 160, such as fans or coolant pumps. In addition, a belt tensioner 140 can be provided, in order to pretension belt 120.

(6) A control unit 170 is configured to control internal combustion engine 110 and starter generator 130. In particular, control unit 170 is configured to implement a method according to an example embodiment the present invention, which method is schematically represented in FIG. 2.

(7) In this context, the motor vehicle can be operated regularly in road traffic. In step 201, internal combustion engine 110 is idled, for example, because the motor vehicle comes to a stop at a red light or is parked. During idle, the engine speed can be 700 rpm (idling speed).

(8) In step 202, a test torque of, e.g., 1 Nm is specified by control unit 170. Control unit 170 controls starter generator 130, in order that it transmit the specified test torque to the internal combustion engine via belt 120.

(9) In step 203, control unit 170 controls internal combustion engine 110, in order to reduce its torque by the specified test torque of 1 Nm.

(10) If the torque actually transmitted by starter generator 130 to internal combustion engine 110 corresponds to the specified test torque, then the engine speed should remain at least substantially constant at the idling speed of 700 rpm. If the torque actually transmitted (actual torque) and the specified test torque (setpoint torque) differ from one another, for example, due to aging and/or wear effects or material and manufacturing tolerances, then the engine speed changes.

(11) In step 204, the speed of internal combustion engine 110 is therefore determined as a speed variable. In step 205, the determined engine speed is evaluated. In this context, it is checked, in particular, if the engine speed remains constant at the value of the idling speed of 700 rpm, or if the engine speed decreases or increases. From this, a torque accuracy of the torque transmitted by starter generator 130 to internal combustion engine 110 is deduced.

(12) If the speed remains constant, then, in step 206, it is deduced that the torque accuracy is sufficiently high. If the speed decreases or increases, then the torque actually transmitted and the specified test torque differ from each other. In this case, it is concluded, in step 207, that the torque accuracy is not sufficiently high. In this case, then, in step 208, a correction of the torque transmitted by starter generator 130 is carried out. In this context, for example, the specified test torque is changed iteratively until the speed of internal combustion engine 110 remains constant and the torque accuracy is, consequently, sufficiently high.

(13) In addition, a correction factor can be defined, which indicates how sharply the torque actually transmitted deviates from the specified test torque. For example, a quotient from the test torque, at which the engine speed remains constant, divided by the test torque that was specified according to step 202, is designated as a correction factor. In the future, this correction factor may be taken into account in the control of starter generator 130.

(14) The method is aborted, in particular, if in steps 201 through 204, the engine speed changes on the basis of a driver request (e.g., drive off). In all cases, both in response to termination and in response to sufficient or insufficient torque accuracy, the method for ascertaining the torque accuracy is repeated, as soon as the motor vehicle is idled again, which is indicated by reference character 209. The engine speed, which is determined in specific step 204 and evaluated, can be stored in a storage area of control unit 170 and used for a time series analysis. In this manner, implausible measured values occurring due to uncontrollable boundary conditions can be detected with the aid of statistical functions and ignored.

(15) Graphs, which can be determined in the course of execution of the method according to an example embodiment of the present invention, are represented in FIG. 3. Three graphs are represented in each of FIGS. 3a through 3c. In each instance, torque M.sub.E of internal combustion engine 110, plotted versus time t, is represented in the upper graph. In each instance, torque M.sub.RSG of starter generator 130, plotted versus time t, is represented in the middle graph. In each instance, speed N of internal combustion engine 110, which is determined according to step 204, is plotted versus time t in the lower graph.

(16) At time t.sub.0, in each instance, torque M.sub.RSG of starter generator 130 is increased by test torque M according to step 202, and in each instance, torque M.sub.E of internal combustion engine 110 is reduced by test torque M of 1 Nm in accordance with step 203.

(17) The case, in which the torque actually transmitted and specified test torque M match and the torque accuracy is sufficiently high, and which is analogous to step 206, is represented in FIG. 3a. In this context, speed N of internal combustion engine 110 is also constant after time t.sub.0 and remains at idling speed N.sub.0 of 700 rpm.

(18) The case, in which the torque actually transmitted is less than specified test torque M, and which is analogous to step 207, is represented in FIG. 3b. Consequently, the torque accuracy is insufficient. In this case, speed N of internal combustion engine 110 decreases after time t.sub.0. The case, in which the torque actually transmitted is greater than specified test torque M, and which is analogous to step 207, is represented in FIG. 3c. In this instance, the torque accuracy is insufficient, as well. In this case, speed N of internal combustion engine 110 increases after time t.sub.0.