Hybrid drivetrain having active torsional vibration damping, and method for carrying out the active torsional damping

Abstract

A drivetrain having an active torsional vibration damping and a method for carrying out the active torsional vibration damping, having an internal combustion engine being affected by torsional vibrations and having a crankshaft, a torsional vibration damper that is operatively connected to the crankshaft and has at least one operating point of low vibration isolation of the torsional vibrations and has a primary inertial mass associated with the crankshaft and an inertial mass associated with a gear input shaft of a gearbox, the inertial mass being rotatable relatively and limitedly with respect to the primary inertial mass against the action of a spring device. The drivetrain also includes an electric motor having a rotating mass operatively connected to the gearbox input shaft, and a control unit, the spring device being formed by linear springs, the rotating mass of the electric motor being designed as a secondary inertial mass.

Claims

1. A method for carrying out an active torsional vibration damping in a drivetrain having a combustion engine subject to torsional vibrations, the drivetrain comprising a torsional vibration damper that is operationally connected to a crankshaft of the combustion engine, a primary inertial mass arranged on the crankshaft, an electric machine operationally coupled to a transmission input shaft of a transmission, the electric machine having a rotor forming a secondary inertial mass assigned to the transmission input shaft, a spring device coupling the primary inertial mass and the secondary inertial mass to be relatively and limitedly rotatable with respect to each other, and a control unit for regulating an output torque of the electric machine to a compensation torque that compensates for a disturbance torque subject to torsional vibration which occurs at at least one operating point, the method comprising the steps of: receiving data from at least one sensor; determining a differential angle of rotation between the primary inertial mass and the secondary inertial mass based on the data; calculating the disturbance torque of the drivetrain based on predetermined parameters and the differential angle of rotation; determining the compensation torque based on the disturbance torque; imprinting the compensation torque onto a memory to be used by the electric machine; and, using the rotor of the electric machine to implement the compensation torque to the drivetrain.

2. The method as recited in claim 1, wherein the at least one operating point represents an idling of the combustion engine, while an idling regulation of the combustion machine occurs by means of the electric machine, in that a regulator regulates the compensation torque to maintenance of a mean idling speed of the crankshaft.

3. The method as recited in claim 1, wherein the at least one operating point represents the occurrence of jerking or load reversal vibrations, where a regulator regulates the compensation torque to a compensation of rotational nonuniformities of the secondary inertial mass.

4. The method as recited in claim 1, wherein the at least one operating point represents a starting of the combustion engine, where a regulator regulates a differential speed of rotation between the primary and secondary inertial masses to zero.

5. The method as recited in claim 1, wherein the step of receiving data from at least one sensor comprises: receiving a first set of information from a first sensor operatively arranged before the primary inertial mass.

6. The method as recited in claim 5, wherein the first sensor is operatively arranged in the combustion engine.

7. The method as recited in claim 1, wherein the primary inertial mass, the secondary inertial mass and the spring device form a torsional vibration damper.

8. The method as recited in claim 7, wherein the spring device is formed of linearly formed springs distributed around a circumference of the torsional vibration damper.

9. The method as recited in claim 7, wherein the step of receiving data from at least one sensor comprises: receiving a first set of information from a first sensor operatively arranged before the primary inertial mass; and, receiving a second set of information from a second sensor operatively arranged after the torsional vibration damper.

10. The method as recited in claim 1, wherein the step of imprinting the compensation torque onto a memory to be used by the electric machine comprises: obtaining at least one parameter from the at least one sensor; creating one or more torque characteristic maps based on at least one parameter; and, storing the one or more torque characteristic maps onto the memory to be used by the electric machine.

11. The method as recited in claim 10, wherein the one or more torque characteristic maps are: developed empirically or using a simulation of the hybrid drivetrain; and, adapted continuously to changes occurring in the drivetrain.

12. The method as recited in claim 1, wherein the step of determining a differential angle of rotation between the primary inertial mass and the secondary inertial mass based on the data comprises: receiving a signal from the at least one sensor; determining an upper dead-center position of one or more cylinders of the combustion engine based on the signal; and, determining the phase position of the crankshaft based on the upper dead-center position.

13. A method for carrying out an active torsional vibration damping in a drivetrain having a combustion engine subject to torsional vibrations, the drivetrain comprising a torsional vibration damper that is operationally connected to a crankshaft of the combustion engine, a primary inertial mass arranged on the crankshaft, an electric machine operationally coupled to a transmission input shaft of a transmission, the electric machine having a rotor forming a secondary inertial mass assigned to the transmission input shaft, a spring device coupling the primary inertial mass and the secondary inertial mass to be relatively and limitedly rotatable with respect to each other, and a control unit for regulating an output torque of the electric machine to a compensation torque that compensates for a disturbance torque subject to torsional vibration which occurs at at least one operating point, the method comprising the steps of: receiving data from one or more sensors; determining a differential speed of rotation between the primary and secondary inertial masses based on the data; calculating the disturbance torque based on the differential speed of rotation; determining the compensation torque based on the disturbance torque; imprinting the compensation torque onto a memory to be used by the electric machine; and, using the rotor of the electric machine to implement the compensation torque to the drivetrain.

14. A method for active torsional vibration damping comprising: providing a drivetrain comprising: a combustion engine including a crankshaft with a primary inertial mass; a transmission input shaft drivingly engaged with an electric machine including a secondary inertial mass; a torsional vibration damper, including a plurality of linearly formed springs arranged around a circumference, the torsional vibration damper operatively arranged in a torque path between the crankshaft and the transmission input shaft to permit limited relative rotation of the secondary inertial mass relative to the primary inertial mass; and, a control unit; the method comprising: exciting the drivetrain with torsional vibrations from the combustion engine; selecting an operating point of lesser vibration isolation; determining a disturbance torque T.sub.dyn at the operating point of lesser vibration isolation in the torque path after the torsional vibration damper; calculating a compensation torque T.sub.harm to compensate for the disturbance torque; and, applying the compensation torque T.sub.harm to the drivetrain with the electric machine.

15. The method for active torsional vibration damping as recited in claim 14, wherein the control unit comprises a P controller for regulating rotation of the second inertial mass to determine the compensation torque T.sub.harm.

16. The method for active torsional vibration damping as recited in claim 14, wherein: the drivetrain includes at least one sensor; the sensor is used to determine the disturbance torque T.sub.dyn; and, the disturbance torque T.sub.dyn is represented by a torque amplitude characteristic map and a torque phase characteristic map stored in the control unit.

17. The method for active torsional vibration damping as recited in claim 14, wherein: the drivetrain includes an upper dead-center position sender for the combustion engine; and, the upper dead-center position sender is used to determine a phase pattern of the disturbance torque T.sub.dyn.

18. The method for active torsional vibration damping as recited in claim 14, wherein: the operating point of lesser vibration isolation is at an idle speed of the combustion engine; the compensation torque T.sub.harm is determined to maintain a mean idle speed of the crankshaft; and, using the electric machine to apply the compensation torque T.sub.harm to the drivetrain regulates the idle speed of the combustion engine.

19. The method for active torsional vibration damping as recited in claim 14, wherein: the operating point of lesser vibration isolation includes jerking or load reversal vibrations; and, the compensation torque T.sub.harm is determined to compensate for rotational nonuniformities of the secondary inertial mass.

20. The method for active torsional vibration damping as recited in claim 14, wherein: the operating point of lesser vibration isolation is selected during a starting of the combustion engine; and, the compensation torque T.sub.harm is determined to maintain a zero differential rotational speed between the primary inertial mass and the secondary inertial mass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:

(2) FIG. 1 is a schematic view of a hybrid drivetrain for active torsional vibration damping;

(3) FIG. 2 is a vibration model of the drivetrain of FIG. 1; and,

(4) FIG. 3 is a flowchart showing an example method of carrying out active torsional vibration damping in the drivetrain of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(5) At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspects.

(6) Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and, as such, may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims.

(7) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described.

(8) FIG. 1 shows a schematic view of hybrid drivetrain 1 with torsional vibration damper 2, whose primary inertial mass 3 is connected to crankshaft 13 of a combustion engine (not shown) and is driven thereby. Secondary inertial mass 4 is at the same time rotor 14 of electric machine 5, which is situated effectively at the output of torsional vibration damper 2. Inertial masses 3, 4 of torsional vibration damper 2 are situated so that they are rotatable relative to each other, contrary to the effect of spring device 6 and friction device 7. Coil springs 8 depicted in the form of their characteristic curves are of short and linear design, and are positioned around the circumference. Because of the short and linear design of coil springs 8, the moment of friction of friction device 7 is advantageously small. The output part of torsional vibration damper 2 in the form of secondary inertial mass 4 is coupled with transmission 10 by means of frictionally and torsionally elastic transmission input shaft 9. Transmission 10 in turn is coupled vibrationally with vehicle body 11 through the attachment of the latter, and for example, by means of the torsionally elastic and frictionally affected drive shaft(s) 12. This forms a vibration system having natural frequencies which can be excited by power train vibrations, and can thus cause noise loading and mechanical loading of the vehicle and its components.

(9) To be able to keep the design of the construction space small and the mechanical complexity of the torsional vibration damper simple in the form of spring device 6 in hydraulic drivetrain 1, for example, with combustion engines having hard-to-damp torsional vibrations, such as two-cylinder or three-cylinder engines, for example, another residual vibration, not brought about by torsional vibration damper 2, waiting at secondary inertial mass 4, in the form of a dynamic disturbance torque dependent on the angle of rotation, occurs by means of an active torsional vibration damping brought about by means of electric machine 5.

(10) The torque progressions of drivetrain 1 for this can be seen from FIG. 2. In one embodiment, a control strategy to compensate for the torsional vibrations remaining after torsional vibration damper 2 is determined at transmission input shaft 9 by means of the relationship of compensation torque T.sub.harm of electric machine 5 to the sum of the other occurring torques such as damper torque T.sub.damp at the input of primary inertial mass 3, disturbance torque T.sub.dyn of secondary inertial mass 4 from mass moment of inertia J.sub.sec of secondary inertial mass 4, its change of angle of rotation d in time interval dt according to the equation
T.sub.dyn=J.sub.sec*d/dt
corresponding to the dynamic torque, and output torque T.sub.ips. In this case, the mass moment of inertia J.sub.sec results from the mass moment of inertia of secondary inertial mass 4 and the mass moment of inertia of rotor 14 of electric machine 5.

(11) After solving the equation of total torque T.sub.sum
T.sub.sum=T.sub.harm+T.sub.damp+T.sub.ipsT.sub.dyn
the compensation torque turns out to be
T.sub.harmT.sub.dampT.sub.ips+T.sub.dyn.

(12) Compensation torque T.sub.harm is applied phase-selectively to disturbance torque T.sub.dyn of electric machine 5, generated dependent on angle of rotation .sub.motor of crankshaft 13, to secondary inertial mass 4. Since the time pattern of summed torque T.sub.sum cannot be determined, we take recourse to phase-selective characteristic maps, which are laid out depending on parameters which are known or which can be determined from sensor data, such as speeds of rotation, accelerations, torques and the like. Signals from one or more senders are used by preference as representative parameters for determining the upper dead-center position of one or more cylinders of the combustion engine. To determine a differential angle of crankshaft 13 and rotor 14 of electric machine 5, the sensor such as a differential angle sensor of electric machine 5 is used, which is intended for detecting the angle of rotation of rotor 14 for commutating electric machine 5.

(13) It has been found that in a real environment of drivetrain 1 a rotational angle deviation smaller than 10, in particular, smaller than 6, resulting from time delay, is advantageous for active torsional vibration damping, for example, of a four-cylinder engine. This means that for disturbance torque T.sub.dyn within an angular shift of 10 or 6 a phase-selective response of compensation torque T.sub.harm should be imprinted on secondary inertial mass 4. Based on the example of a four-cylinder engine and damping of a vibration order equal to two with a crankshaft speed of 3000 rpm, a sampling frequency of 10 kHz has therefore proven to be advantageous. This corresponds to a phase angle of 3.6.

(14) Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.

LIST OF REFERENCE NUMERALS

(15) 1 drivetrain 2 torsional vibration damper 3 primary inertial mass 4 secondary inertial mass (rotor) 5 electric machine 6 spring device 7 friction device 8 coil spring 9 transmission input shaft 10 transmission 11 vehicle body 12 drive shaft 13 crankshaft 14 rotor 15a additional damping element 15b additional damping element 15c additional damping element T.sub.damp damper torque T.sub.harm compensation torque T.sub.ips output torque T.sub.sum summed torque T.sub.dyn disturbance torque .sub.motor angle of rotation d angle of rotation dt time interval J.sub.sec mass moment of inertia CE combustion engine CU control unit S sensor S2 sensor