HYBRID DRIVE HAVING AN INTERNAL COMBUSTION ENGINE WITH REDUCED DRAG TORQUE

Abstract

A hybrid drive for a vehicle includes an electric machine, an internal combustion engine, and a transmission with a transmission input shaft. The electric machine and the internal combustion engine are coupled to the transmission input shaft such that the electric machine and the internal combustion engine cannot be decoupled.

Claims

1.-11. (canceled)

12. A hybrid drive for a vehicle; comprising: an electric machine; an internal combustion engine; and a transmission with a transmission input shaft; wherein the electric machine and the internal combustion engine are coupled to the transmission input shaft such that the electric machine and the internal combustion engine cannot be decoupled.

13. The hybrid drive according to claim 12, wherein: the transmission has a wet space as part of an oil circuit of the transmission; and the electric machine is coupled to the transmission input shaft in the wet space of the transmission.

14. The hybrid drive according to claim 12 further comprising a damping system for damping torsional oscillations; wherein a crankshaft of the internal combustion engine is coupled to the transmission input shaft via the damping system; and wherein the electric machine is coupled to the transmission input shaft such that in a purely electric operating mode of the hybrid drive the crankshaft of the internal combustion engine is driven by the electric machine via the damping system.

15. The hybrid drive according to claim 12, wherein: the transmission has a clutch, wherein with the clutch the transmission input shaft can be decoupled from an output shaft of the transmission and/or from the transmission; and the electric machine is coupled to the transmission input shaft upstream of the clutch with respect to the output shaft of the transmission.

16. The hybrid drive according to claim 12, wherein the electric machine is coupled to the transmission input shaft via a spur gear stage in a fixed manner and/or such that the electric machine cannot be decoupled.

17. The hybrid drive according to claim 12, wherein the electric machine is coupled to the transmission input shaft via a chain in a fixed manner and/or such that the electric machine cannot be decoupled.

18. The hybrid drive according to claim 12, wherein the electric machine has an operating voltage and/or a rated voltage of 70V or less.

19. The hybrid drive according to claim 12, wherein: the transmission is a double clutch transmission; the transmission has a first clutch which is configured to couple the transmission input shaft to a first component transmission of the transmission; the transmission has a second clutch which is configured to couple the transmission input shaft to a second component transmission of the transmission; and the transmission has one or more shift elements for coupling the first component transmission or the second component transmission to an output shaft of the transmission.

20. The hybrid drive according to claim 12 further comprising a control unit configured to determine that an output shaft of the transmission is to be driven by the electric machine but not by the internal combustion engine and to bring about one or more drag-torque-reducing measures in order to reduce a drag torque which is brought about on the transmission input shaft by the internal combustion engine.

21. A vehicle, comprising: the hybrid drive according to claim 12.

22. The vehicle according to claim 21, wherein the vehicle has an axle which is driven by the hybrid drive and wherein the electric machine of the hybrid drive is disposed parallel to the axle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 shows an exemplary hybrid drive of a vehicle with a double-clutch transmission;

[0022] FIG. 2 shows further details of the double-clutch transmission illustrated in FIG. 2; and

[0023] FIG. 3 shows an optimized connection of the electric machine of a hybrid drive to a double-clutch transmission.

DETAILED DESCRIPTION OF THE DRAWINGS

[0024] As stated at the beginning, the present document is concerned with providing a hybrid drive which is optimized for operation with an internal combustion engine with reduced drag torque. In this context, FIG. 1 shows a block diagram of an exemplary hybrid drive 100 for a vehicle. A hybrid drive 100 comprises an internal combustion engine 101 and an electric machine 102 which can be used individually or together to generate a drive torque for the vehicle. The internal combustion engine 101 and the electric machine 102 are arranged in such a way that the torques generated by the respective drive motor are added together to form an overall drive torque which is transmitted, for example, via a transmission 104 and an output shaft 108 of the transmission 104 to one or more wheels 109 of the vehicle. The electric energy for the operation of the electric machine 102 can be stored in an electrical energy store 110.

[0025] The vehicle and/or the hybrid drive 100 also comprise a control unit 111 (e.g., an engine control unit) which is configured to determine a requested overall drive torque. The requested overall drive torque can be specified by a driver of the vehicle by means of an accelerator pedal and/or by means of a setting of the transmission 104, for example. For example, a driver can activate the accelerator pedal to request an increased overall drive torque. The control unit 111 can be configured to divide the requested overall drive torque into a first torque (for the internal combustion engine 101) and into a second torque (for the electric machine 102). In other words, the control unit 111 can be configured to operate the internal combustion engine 101 and the electric machine 102 as a function of a requested overall drive torque.

[0026] In the example illustrated in FIG. 1, the hybrid drive 100 comprises a double-clutch transmission 104 which has a first clutch 105 which is configured to couple the transmission input shaft 107 of the transmission 104 to a first input shaft 115 to form a first component transmission 125 of the transmission 104 or to decouple it therefrom. Furthermore, the transmission 104 has a second clutch 106 which is configured to couple the transmission input shaft 107 of the transmission 104 to a second input shaft 116 to form a second component transmission 126 of the transmission 104 or to decouple it therefrom. The transmission input shaft 107 can be coupled directly or indirectly (e.g., via a two-mass flywheel) to the internal combustion engine 101, in particular to the crankshaft of the internal combustion engine 101.

[0027] The first input shaft 115 and the second input shaft 116 are typically coaxial with respect to one another. In particular, the first input shaft 115 can be a solid shaft which is encircled by the second input shaft 116 which is embodied as a hollow shaft. The first input shaft 115 can be coupled to the output shaft 108 via the first component transmission 125 and a gear speed which is set therein. Furthermore, the second input shaft 115 can be coupled to the output shaft 108 via the second component transmission 126 and a gear speed which is set therein. For example, the uneven gear speeds (e.g., 1, 3, 5, etc.) can be provided by the first component transmission 125, and the even gear speeds (e.g., 2, 4, 6, etc.) by the second component transmission 126. The first and/or second component transmissions 125, 126 typically have one or more shifting elements 103 by means of which the different gear speeds of the respective component transmission 125, 126 can be engaged in an automated fashion and/or by means of which the respective component transmission 125, 126 can be placed in a neutral position (without a gear speed engaged). In a neutral position the input shaft 115, 116 of a component transmission 125, 126 is typically decoupled from the output shaft 108.

[0028] In the example illustrated in FIG. 1, the electric machine 102 of the hybrid drive 100 can be coupled only to one of the two component transmissions 125, 126 or connected to only one of the two component transmissions 125, 126. In particular, the electric machine 102 can be or is coupled directly to the input shaft 115, 116 by one of the two component transmissions 125, 126. Furthermore, the electric machine 102 is arranged in such a way that coupling to the input shaft 115, 116 of the respective other component transmission 125, 126 is possible only via the clutches 105, 106.

[0029] FIG. 2 shows further details of the double-clutch transmission 104 which is illustrated in FIG. 1 and has an electric machine 102 which is connected only to the second component transmission 126 of the double-clutch transmission 104. In particular, the electric machine 102 is arranged downstream of the clutches 105, 106 of the double-clutch transmission 104 (which are also referred to as starter elements) so that at least for some of the gear speeds a coupling of the electric machine 102 to the output shaft 108 of the transmission 104 is possible only by closing both clutches 105, 106.

[0030] On the other hand, the electric machine 102 is arranged or connected upstream of the output-side shifting elements 103.

[0031] The connection of the electric machine 102 illustrated in FIGS. 1 and 2 in a purely electric operating mode of the hybrid drive 100 is disadvantageous, since shifting processes are possible only with interruption of the tractive force and/or by means of assistance from a service break of the vehicle. This has adverse effects on the comfort and/or on the energy efficiency of the hybrid drive 100.

[0032] FIG. 3 shows a hybrid drive 100 in which the electric machine 102 is fixedly coupled to the transmission input shaft 107 of the transmission 104. In particular, the electric machine 102 can be connected between the damping system 201 for reducing torsional oscillations (in particular from the two-mass flywheel) and upstream of the starter element 105, 106 (i.e., upstream of the double clutch). It is therefore possible for there to be an efficient and comfortable connection of the electric machine 102. In particular, in this way it is possible to efficiently and comfortably avoid interruptions in the tractive force during shifting processes in the purely electric operating mode.

[0033] The connection of the electric machine 102 can be carried out with a chain 303 or by means of a spur gear stage in the wet space 307 of the transmission 104. In particular, a gearwheel 302 which is coupled to a gearwheel 304 of the transmission 104 via a chain 303 in a fixed fashion and/or such that it cannot be decoupled can be arranged on the drive axle 301 of the electric machine 102, wherein the gearwheel 304 is fixedly coupled to the transmission input axle 107 and/or to the primary side 305 of the transmission 104 or is directly connected to the transmission input axle 107 via a toothed engagement of one or more spur gear stages.

[0034] The connection between the damping system 201 for reducing torsional oscillations and the starter element 105, 106 forces the coupling to the transmission input shaft 107 to take place in a region in which the irregularity of the rotational speed is already alleviated by the damping system 201, so that this region is advantageous in terms of technical design criteria and in terms of criteria of the acoustics of the vehicle. Furthermore, the connection in the wet space 307 of the transmission 104 permits a common oil circuit to be used for the transmission 104 for the purpose of cooling and lubricating the connection of the electric machine 102.

[0035] The electric machine 102 can be arranged axis-parallel to a driven axle of a vehicle, in a way which is efficient in terms of installation space.

[0036] The electric machine 102 therefore has a connection to the transmission input shaft 107 which cannot be decoupled, causing the internal combustion engine 101 to be entrained in the purely electric operating mode. In order to reduce the drag torque of the internal combustion engine 101, it is possible to implement one or more drag-torque-reducing measures. For example, one or more cylinders of the internal combustion engine 101 can be switched off. The drag torque which is brought about by the internal combustion engine 101 in the purely electric operating mode can therefore be reduced.

[0037] On the other hand, the entraining of the internal combustion engine 101 in the purely electric operating mode is advantageous, since the entraining efficiently permits prompt re-activation of the internal combustion engine 101 to be brought about. In other words, the entraining of the internal combustion engine 101 makes an efficient changeover possible between the different operating modes (purely electric operating mode and operation with a portion provided by an internal combustion engine) of a hybrid drive 100.

[0038] The present invention is not limited to the exemplary embodiments shown. In particular it is to be noted that the description and the figures are intended to represent only the principle of the provided devices and systems.