Hybrid powertrain and gear change procedure

Abstract

Hybrid drive train (10) for a motor vehicle (11), comprising: - an internal combustion engine (12) for providing internal combustion engine drive power; - a multi-step transmission (16) having a transmission input (46) and a transmission output (48), wherein the transmission input (46) is connected to the internal combustion engine (12) and wherein the multi-step transmission (16) is designed to establish a plurality of different forward gear stages (1 - 4; 1 - 7); and - an electric machine (14) for providing electric motor drive power; characterized in that the electric machine (14) is connected to the transmission output (48) via a further multi-step transmission (26), the further multi-step transmission (26) having at least two gear stages (I, II), the drive train (10) being designed for front-transverse installation in a motor vehicle (11), respective output shafts of the electric machine (14) and of the internal combustion engine (12) being directed towards one another and the electric machine (14) at least partially overlapping with the differential (18) in the direction of its longitudinal axis, and the multi-step transmission (16) and the further multi-step transmission (26) being arranged in the axial direction between the internal combustion engine (12) and the electric machine (14).

Description

[0001] The invention relates to a hybrid drive train for a motor vehicle, comprising an internal combustion engine for providing internal combustion engine drive power, a multi-step transmission with a transmission input and a transmission output, wherein the transmission input is connected to the internal combustion engine and wherein the multi-step transmission is designed to establish a plurality of different forward gear stages, and an electric machine for providing electromotive drive power.

[0002] Furthermore, the present invention relates to a motor vehicle with such a hybrid drive train.

[0003] Hybrid drivetrains for motor vehicles are known in various designs. In some hybrid drivetrains, an electric motor is connected to a transmission input. Such hybrid drivetrains allow the electric motor to be used for boosting or for purely electric drive. In this case, all forward gears of the multi-step transmission can be used in electric drive mode. However, in this case, the electric motor cannot be used to provide traction assistance during gear changes. This is possible with hybrid drivetrains in which the electric motor is connected to the output of the multi-step transmission. In this case, purely electric drive can only be achieved with a single gear ratio.In addition, stationary charging (using the electric machine as a generator to charge an electrical energy storage device when the vehicle is stationary) is generally not possible.

[0004] Hybrid powertrains are also known in which the multi-step transmission is designed as a dual-clutch transmission. Such transmissions, in and of themselves, enable gear changes without interrupting traction. For example, it is known to connect an electric motor to one of the two sub-transmissions of such a dual-clutch transmission, usually at the transmission input. However, such hybrid powertrains are very complex, and some functions are performed twice.

[0005] From the document DE 197 47 265 A1 a hybrid drive train is known in which no separate gear set for reversing is provided in the multi-stage transmission, so that reversing is only possible via an electric motor.

[0006] The document DE 10 2005 048 938 A1 discloses a hybrid drive train with a dual-clutch transmission, wherein an electric machine can be effectively connected to both a first and a second transmission input shaft via an additionally provided transmission.

[0007] Document EP 1 972 481 A1 discloses a hybrid drivetrain in which a first gearshift sub-transmission has an input shaft and an output shaft, with odd gear ratios, for example, being assigned to the first sub-transmission. Furthermore, the drivetrain includes a second gearshift sub-transmission with an input shaft and an output shaft, with even gear ratios, for example, being assigned to this sub-transmission. The input shaft of the first gearshift sub-transmission can be coupled to the combustion engine via a starting clutch. The input shaft of the second gearshift sub-transmission is drive-connected to the electric motor. Furthermore, the two input shafts can be connected to one another in a rotationally fixed manner via a clutch unit.

[0008] Finally, from the document DE 196 12 690 C1 a drive train with an automated manual transmission is known, which is designed as a group transmission with a first transmission group and a downstream second transmission group.

[0009] DE 10 2011 077 594 A1 shows a solution in which the electric machine is coupled or can be coupled to a "first transmission device" via the first torque input, and the internal combustion engine is coupled or can be coupled to a "second transmission device" of the torque superposition device via the second torque input. The transmission devices are each coupled on the output side to the torque output, i.e., are kinematically connected, and a clutch is provided by means of which torque can be transmitted from the first torque input to the second torque input, or vice versa. At least one, preferably both transmission devices have at least two alternatively selectable transmission ratios or transmission stages.

[0010] FR 2 811 395 A1 shows a hybrid drive train for a motor vehicle with: - an internal combustion engine and a multi-step transmission with a transmission input and a transmission output, wherein the transmission input is connected or connectable to the internal combustion engine, and an electric machine, wherein the electric machine is connected to the transmission output via a further multi-step transmission, wherein the further multi-step transmission has at least two gear stages, wherein the drive train is designed for front-transverse installation in a motor vehicle, wherein respective output shafts of the electric machine (and of the internal combustion engine (12)) are directed towards one another and the electric machine at least partially overlaps with a differential in the direction of its longitudinal axis.

[0011] Further examples are known from the documents DE 199 81 968 B4, DE 10 2010 030 573 A1, DE 10 2011 014 703 A1, WO 2010 / 070 707 A1 and DE 101 33 695 A1.

[0012] Against the above background, it is an object of the invention to provide an improved hybrid drive train and a motor vehicle equipped therewith.

[0013] The above object is achieved in the hybrid drive train mentioned at the outset in that the electric machine is connected to the transmission output via a further stepped transmission, wherein the further stepped transmission has at least two gear stages, wherein the drive train is designed for front-transverse installation in a motor vehicle, wherein respective output shafts of the electric machine and of the internal combustion engine are directed towards one another and the electric machine at least partially overlaps with a differential in the direction of its longitudinal axis and the stepped transmission and the further stepped transmission are arranged in the axial direction between the internal combustion engine and the electric machine.

[0014] Furthermore, the above object is achieved by a motor vehicle with such a hybrid drive train.

[0015] With the hybrid drivetrain according to the invention, the combustion engine can be operated with all forward gears of one multi-step transmission. The electric motor can drive the vehicle solely with the different gear ratios of the other multi-step transmission.

[0016] The one multi-step transmission can be designed with a single transmission input, thus being implemented in the manner of an automated manual transmission. Complex dual-clutch arrangements or transmission input shaft arrangements with an inner and a hollow shaft, as in a dual-clutch transmission, are not necessary in the hybrid drive train according to the invention.

[0017] Preferably, an output of the additional multi-step transmission is identical to the transmission output of the one multi-step transmission. Thus, purely combustion engine-based driving operation can be established via the one multi-step transmission. Purely electric motor-based driving operation can be established via the additional multi-step transmission. Furthermore, drive power can be summed at the transmission output, enabling a drive mode in which drive power is provided by both the combustion engine and the electric motor. It is also possible to perform gear changes in the one multi-step transmission, with the electric motor providing tractive power to bridge the interruption in tractive power that would otherwise occur.

[0018] As a result, the hybrid drivetrain can be operated very comfortably.

[0019] The transmission input can, for example, be a transmission input shaft. The transmission output can, for example, be connected to a differential that distributes the drive power between two drive shafts. The drive shafts can, for example, be connected to driven wheels of the motor vehicle. However, the driven shafts can also be connected to a first or second axle of the motor vehicle.

[0020] In general, it is therefore possible to implement a hybrid powertrain with high functionality and a comparatively simple basic structure, allowing for many functions in a small space. The powertrain can also be lightweight and have low friction losses, allowing the powertrain to be implemented with low fuel consumption.

[0021] In general, with the drive train according to the invention, it is also possible to provide drive power via the one step transmission during gear shifts in the further step transmission in purely electric driving mode by means of the combustion engine in order to reduce an interruption in tractive force in purely electric driving mode.

[0022] This drivetrain features a cost-effective package. Furthermore, very simple and minimal components can be used. The multi-step transmission and the additional multi-step transmission are preferably designed as conventional countershaft transmissions with a transmission input shaft and a transmission output shaft. The individual gear ratios of the multi-step transmissions can be implemented by gear sets and associated clutches, which can be implemented, for example, as synchronous clutches, in particular as locking synchronous clutches.

[0023] A transmission input shaft of one multi-step transmission is preferably offset parallel to the transmission output shaft of the first multi-step transmission. Similarly, a transmission input shaft of the further multi-step transmission, which is preferably aligned coaxially with a motor shaft of the electric machine, is offset parallel to a transmission output shaft of the further multi-step transmission. The transmission output shafts of the multi-step transmissions can be realized by a single shaft or by a coaxial shaft arrangement.

[0024] The additional multi-step transmission can also be used to operate the electric motor as a generator during combustion engine operation, for example, to charge a battery. The drive power is then diverted via the additional multi-step transmission.

[0025] Furthermore, it is possible to completely decouple the electric motor in purely combustion engine operation. In this case, all the clutches of the other multi-step transmission can be set to neutral, i.e., disengaged. Similarly, the combustion engine can also be decoupled in purely electric operation by disengaging all the clutches of one multi-step transmission.

[0026] During overrun or braking, the electric motor can also operate in a recuperative mode.

[0027] The hybrid drive train according to the invention is suitable for installation in a front-transverse design as well as for installation in a longitudinal design in a motor vehicle.

[0028] The above task is thus completely solved.

[0029] The above-mentioned clutches can be implemented as claw clutches, but are particularly designed as synchronous clutches and, particularly preferably, as clutches with locking synchronization.

[0030] Proven components from the field of manual step transmissions can be used here.

[0031] In this case, two gears are preferably available for operating the electric motor. Therefore, purely electric operation can also be achieved over a wide speed range. A suitable gear ratio can also be selected for generator operation.

[0032] Finally, in the embodiment according to the invention, the combustion engine is rigidly connected to the transmission input.

[0033] In this case, the hybrid drivetrain can be implemented compactly and with few components. In this embodiment, starting can be achieved, for example, via the electric motor. Reversing can also be achieved via the electric motor.

[0034] Accordingly, it is also preferred if no separate reverse gear set is provided in the first transmission group. In an alternative embodiment, however, a separate reverse gear set can be provided in the first transmission group.

[0035] In an alternative embodiment not according to the invention, the internal combustion engine is connected to the transmission input via a starting clutch.

[0036] The starting clutch can, for example, be a dry friction clutch and is preferably operated automatically.

[0037] In this context, it is understood that the clutches present in the drive train are also preferably operated automatically.

[0038] According to the embodiment, the drive train is designed for front-transverse installation in a motor vehicle, with respective output shafts of the electric machine and the internal combustion engine directed towards each other.

[0039] In this embodiment, the multi-step transmission and the further multi-step transmission are arranged in the axial direction between the combustion engine and the electric machine, resulting in a compact design.

[0040] A longitudinal axis of the combustion engine (crankshaft) is aligned coaxially with a longitudinal axis of the electric machine (motor shaft).

[0041] This also allows a radially compact design to be realized.

[0042] Furthermore, it is advantageous that the electric machine at least partially overlaps with a differential in the direction of its longitudinal axis.

[0043] This also contributes to an axially compact design.

[0044] Overall, it is advantageous if all clutches of the multi-step transmission and the further multi-step transmission are arranged on a coaxial shaft arrangement of the multi-step transmission and the further multi-step transmission.

[0045] In the embodiment, this is a single transmission output shaft.

[0046] Furthermore, it is generally advantageous if the transmission output is connected to a differential via a drive wheel set arrangement.

[0047] It is advantageous if the drive wheel set arrangement has one or two wheel sets.

[0048] With a single gear set for the drive wheel arrangement, a fixed ratio is established between the transmission output and the differential. When using two gear sets, the ratio can be changed in the manner of a range transmission or an overdrive transmission.

[0049] Overall, it is also advantageous if the multi-step transmission, the transmission input of which is connected or connectable to the combustion engine, has fewer than six forward gears, in particular fewer than five forward gears.

[0050] Since the electric motor in the hybrid drive train can be used over a wide operating range, and since the electric motor can provide a traction-assisting torque during gear changes, five or four forward gears may be sufficient to cover the full speed range of the motor vehicle, particularly with a sufficiently large spread, as is otherwise common in passenger vehicles that have six, seven, or more gears. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the present invention.

[0051] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. They show: Fig. 1 a schematic representation of the embodiment of a hybrid drive train according to the invention; and Fig. 2 a schematic representation of a further embodiment of a hybrid drive train not according to the invention.

[0052] In Fig. Figure 1 schematically illustrates an embodiment of a drive train according to the invention and is generally designated 10. The drive train 10 serves to drive a motor vehicle 11, for example in the form of a passenger car.

[0053] The drive train 10 comprises a first drive motor in the form of an internal combustion engine (or in the form of a fuel cell engine) 12 and a second drive motor 14 in the form of an electric machine. The two drive motors 12, 14 are each designed to provide drive power for driving the motor vehicle 11.

[0054] Furthermore, the drive train 10 includes a multi-step transmission 16, which is preferably designed as a countershaft. An unspecified output of the multi-step transmission 16 is connected to a differential 18, by means of which the drive power can be distributed to two drive shafts 20L, 20R. The drive shafts 20L, 20R are preferably connected to driven wheels of the motor vehicle 11. Alternatively, it is possible for the drive shafts 20L, 20R to be connected to two driven axles of the motor vehicle 11.

[0055] The internal combustion engine 12 is connected to an input of the multi-step transmission 16 via a starting clutch 22. The starting clutch 22 can be designed, for example, as a dry friction clutch, but can also be designed as a wet clutch (e.g., a multi-plate clutch).

[0056] The electric machine 14 is connected to the input of a further multi-step transmission 26. The further multi-step transmission group 26 contains a plurality of different gear ratios, each of which can be alternatively switched into the power flow. In the present case, the second multi-step transmission 26 has a first gear ratio I and a second gear ratio II. The first gear ratio I can be switched into the power flow by means of a first clutch 32 of the further multi-step transmission 26. The second gear ratio II can be switched into the power flow by means of a second clutch 34. Accordingly, the electric machine 14 can drive the motor vehicle 11 via the first gear ratio I when the clutch 32 is switched on, or via the second gear ratio II when the clutch 34 is switched on.

[0057] The first step transmission 16 includes a plurality of gear ratios, the number preferably being greater than the number of gear ratios of the further step transmission.

[0058] The first step transmission 16 has four ratios, which are Fig. 1 are labeled 1, 2, 3, 4, corresponding to respective gear stages 1 to 4. The first gear ratio 1 can be switched into the power flow by means of a third shift clutch intermediate circuit 36. The second gear ratio 2 is assigned a fourth shift clutch 38. The third gear ratio 3 is assigned a fifth shift clutch 40. The fourth gear ratio 4 is assigned a sixth shift clutch 42.

[0059] The shift clutches 32 to 42 are all arranged on a transmission output shaft extending from the internal combustion engine 12 to the electric machine 14. A transmission input shaft 46 of one multi-step transmission 16 is aligned parallel thereto and coaxial with a crankshaft of the internal combustion engine 12. Similarly, an input shaft 50 of the further multi-step transmission 26 is arranged offset parallel to the transmission output shaft 48, specifically coaxially aligned with a motor shaft of the electric machine 14.

[0060] The transmission output shaft 48 is connected to an input member of the differential 18 via a single drive gear set 52.

[0061] The differential overlaps in the axial direction with the electric machine 14. The clutch 22 is provided optionally, so that the drive train 10 can also be realized without the friction clutch 22, wherein the transmission input shaft 46 is rigidly connected to the crankshaft.

[0062] If the multi-step transmission 16 includes a reverse gear ratio R (not shown), the motor vehicle 11 can be driven in reverse by means of the internal combustion engine 12. If such a ratio is not included in the multi-step transmission 16, the vehicle 11 can be driven in reverse exclusively by means of the electric motor 14.

[0063] The clutches 36-42 of the multi-step transmission 16 can be designed as claw clutches, but are preferably designed as synchronous clutches, in particular as locking synchronous clutches. Multi-step transmissions of this design generally only allow gear changes with an interruption in traction.

[0064] The drivetrain 10 enables purely combustion engine driving via the one multi-step transmission 16, which in this case has four gears. Interruptions in tractive force can be at least partially compensated for by the electric motor 14. During driving, the electric motor 14 can be decoupled via the shift clutches 32, 34. Furthermore, the drivetrain enables purely electric driving via the additional multi-step transmission 26. The combustion engine can be decoupled by disengaging the shift clutches 36 to 42. When shifting between gear ratios I-II of the additional multi-step transmission 26, a "filling torque" can be provided via the combustion engine 12 if necessary.

[0065] Finally, a hybrid operating mode is possible, in which both the internal combustion engine 12 and the electric motor 14 provide drive torque. During internal combustion engine operation, it is possible to operate the electric motor 14 as a generator to charge a battery.

[0066] However, stationary charging is not possible with this hybrid powertrain. Furthermore, starting the combustion engine using the electric motor 14 is not possible, so a separate starter / generator is preferably provided for this purpose. Alternatively, the combustion engine can only be switched on from electric driving mode. In this case, a starter is not necessary.

[0067] The drive train 10 is designed for installation in a front-transverse configuration in a motor vehicle.

[0068] In Fig. 2, a further embodiment of a hybrid drive train not according to the invention is schematically shown and generally designated 10. The drive train 10' of the Fig. 2 generally corresponds to the functionality of Fig. 1. Identical elements are therefore provided with the same reference numerals. The drive train 10 represents a variant of the drive train 10 in which the drive train is installed in a longitudinal design in a motor vehicle 11. Here, the internal combustion engine 12 and the one multi-step transmission 16 are arranged in the region of a first axle (for example, the front axle) of the motor vehicle 11. The electric machine 14 and the further multi-step transmission 16 are arranged in the region of a second axle (for example, the rear axle) of the motor vehicle 11, i.e. in the region of the axle on which the differential 18 is also arranged. The second axle is therefore a driven axle. However, the first axle can also be an additional drive axle via a power take-off unit.

[0069] The transmission output shaft 48 of one multi-step transmission 16 is connected to a cardan shaft 60, which connects the axles to one another. The transmission output shaft 48' of the further multi-step transmission 26 is also connected to the cardan shaft 60 and is preferably coaxially aligned therewith or forms part of the cardan shaft 60. The cardan shaft 60 and the transmission output shaft 48' are connected to the differential 18 via an angular gear.

[0070] This design allows the center of gravity to be improved in favor of the second axle. Furthermore, the installation of conventional drivetrains without hybrid expansion can be retained in the first axle area. The load and stress on the individual components (drive shaft and transmission) are reduced.

[0071] The functioning of the drive train 10 of the Fig. 2 corresponds to that of the drive train 10 of the Fig. 1, as described above.

[0072] The drivetrains can be implemented cost-effectively. No friction clutch, or only a complex one in the form of a starting and disengaging clutch 22, is required. Furthermore, the number of shafts and the number of clutches are very small. Nevertheless, the full functionality of a hybrid drivetrain can be realized. For example, the electric motor 14 can be used for boosting.

[0073] Generator operation to increase the load point is also feasible. Finally, recuperation is also possible.

[0074] The gearset arrangements of the drivetrains described above are each implemented as spur gearsets. Alternatively, the gearset arrangements can also be designed as planetary gears.

Claims

[1] Hybrid drive train (10) for a motor vehicle (11), comprising: - an internal combustion engine (12) for providing internal combustion engine drive power; - a multi-step transmission (16) having a transmission input (46) and a transmission output (48), wherein the transmission input (46) is connected to the internal combustion engine (12) and wherein the multi-step transmission (16) is designed to establish a plurality of different forward gear stages (1 - 4; 1 - 7); and - an electric machine (14) for providing electric motor drive power; characterized by , that the electric machine (14) is connected to the transmission output (48) via a further multi-step transmission (26), the further multi-step transmission (26) having at least two gear stages (I, II), the drive train (10) being designed for front-transverse installation in a motor vehicle (11), respective output shafts of the electric machine (14) and of the internal combustion engine (12) being directed towards one another and the electric machine (14) at least partially overlapping with the differential (18) in the direction of its longitudinal axis, and the multi-step transmission (16) and the further multi-step transmission (26) being arranged in the axial direction between the internal combustion engine (12) and the electric machine (14). [2] Hybrid powertrain according to claim 1, characterized by that all clutches (32 - 42) of the multi-step transmission and the further multi-step transmission are arranged on a coaxial shaft arrangement (48) of the multi-step transmission (16) and the further multi-step transmission (26). [3] Hybrid powertrain according to one of claims 1-2, characterized by that the transmission output (48) is connected to a differential via a drive wheel set arrangement (52). [4] Hybrid powertrain according to claim 3, characterized by that the drive wheel set arrangement (52) has one or two wheel sets. [5] Hybrid powertrain according to one of claims 1-4, characterized by that the multi-step transmission (16), the transmission input (46) of which is connected to the internal combustion engine (12), has fewer than 6 forward gear stages, in particular fewer than 5 forward gear stages.

Images