Use of a wrap-around clutch for torque transmission between electric motors in a hybrid transmission

Abstract

Hybrid transmission (1) with a first drive shaft (2) which is assigned to a first electric machine (3), and with a second drive shaft (4) which is assigned to a second electric machine (5), wherein a clutch (6) is provided for connecting the first drive shaft (2) to the second drive shaft (4) in a torque-transmitting manner, wherein the clutch (6) is designed as a wrap-around clutch (7), characterized in that the wrap-around clutch (7) is arranged radially inside a rotor (17) of the first electric machine (3) and surrounds the second drive shaft (4).

Description

[0001] The invention relates to a hybrid transmission, such as a DHT / dedicated hybrid transmission, a TwinDrive, or a multi-mode unit, with a first drive shaft associated with a first electric motor and a second drive shaft associated with a second electric motor. A clutch is provided for connecting the first drive shaft and the second drive shaft in a torque-transmitting manner. Electric machines can also be referred to as e-machines and can be used as generators or electric motors.

[0002] Many manufacturers are currently developing so-called multimode DHTs. Some of these have only one (single) gear when operating in parallel with an internal combustion engine. There is a discernible trend towards providing DHTs that have (at least / exactly) two gears when the internal combustion engine is operating. Typically, there is a separate drive shaft for the internal combustion engine, to which the rotor of a first electric motor is also connected. Since a second electric motor is often used, this also has an additional shaft parallel / parallel to the aforementioned drive shaft in the state of the art. For this purpose, additional intermediate and auxiliary shafts are used that are also parallel to the axis of both drive shafts. However, this is relatively complex.While one gear can be used for the second electric motor and two gears for the first electric motor and the internal combustion engine, such a transmission unfortunately has a relatively high number of gears, which is costly. Improvements to this are desirable. Such an improvement is particularly desirable for hybrid transmissions.

[0003] Hybrid vehicles, especially plug-in hybrid vehicles, combine locally emission-free driving with low fuel consumption in hybrid mode and a high degree of driving pleasure. Furthermore, stricter legal requirements will continue to drive battery capacity and, with increasing performance, electric power. This results in new challenges regarding package integration and the overall design of such powertrains. The high cost of electrical components continues to create a need to utilize all opportunities for technical simplification.

[0004] The still relatively low overall production volumes for hybrid vehicles have led to the electric drive being primarily arranged in a P2 configuration between the combustion engine and transmission, with the classic drivetrain components remaining largely unchanged. Rising production expectations mean that the optimization of the overall system is increasingly becoming a priority. This includes the possibility of simplifying the mechanical transmission component, for example, by eliminating the reverse gear, and instead using at least one electric motor integrated into the transmission to provide the full range of functions. Such transmission concepts are referred to as dedicated hybrid transmissions or "Dedicated Hybrid Transmissions" (DHT).

[0005] Dedicated hybrid transmissions can be derived from familiar transmission concepts, such as dual-clutch transmissions, torque converter planetary transmissions, continuously variable transmissions (CVTs), or automated manual transmissions. The electric motor becomes part of the transmission, and its connection can be established via various transmission shafts. In addition to parallel (or serial) hybrid modes, one or more power-split operating modes can also be created in combination with a planetary transmission.

[0006] Known variants in this regard can be found, for example, on the Internet page https: / / schaeffler-events.com / kolloquium / lecture / h6 / index.html, which contains a publication on the applicant's colloquium from 2018.

[0007] A hybrid transmission in the form of a DHT is also known from the prior art, for example from DE 10 2019 130 882 B3. Therein, a manual transmission for a motor vehicle is disclosed with at least one drive shaft via which torque can be introduced, wherein between the drive shaft and an output shaft used for torque transfer, a first intermediate shaft and a second intermediate shaft are integrated into the torque flow depending on a switching position of coupling elements such that the torque is guided via the first intermediate shaft and / or the second intermediate shaft, wherein the coupling elements connect gears to the drive shaft of the first intermediate shaft, the second intermediate shaft and / or the output shaft during torque transmission, and wherein the gears are arranged in three axially spaced-apart gear planes.

[0008] Drive devices for motor vehicles are also known in this field from DE 10 2019 131 754 B3.

[0009] Many multimode DHTs are currently under development. These enable serial, parallel, and electric operation. However, it has been shown that efficiency can still be increased in purely electric operation. This also aims to reduce wear and take into account the negative impact of inertia on fuel consumption.

[0010] Electric motors as such are known from US 10 128 705 B2 and its European counterpart, EP 3 465 889 B1. These typically comprise a housing, a stator having stator windings coupled to the housing, a rotor having a rotor shaft and rotor windings, at least two rotor main bearings coupling the rotor shaft to the housing, wherein they comprise at least two rotor main bearings, a first electrical resistance between the rotor shaft and the housing; and a rotor discharge bearing coupling the rotor shaft to the housing, wherein the rotor discharge bearing has a second electrical resistance between the rotor shaft and the housing, wherein the second electrical resistance is smaller than the first electrical resistance in order to conduct a rotor discharge through the rotor discharge bearing.What is special about this European patent is that a rotor main bearing of the at least two rotor main loads has a first load; and the rotor unloading bearing has a second load which is greater than the first load, whereby a lubricant film separating the moving components of the rotor unloading bearing has a smaller thickness than a lubricant film separating the moving components from the stationary components of the rotor main bearing.

[0011] Hybrid transmissions typically use wet clutches to connect a first drive shaft to a second drive shaft, each of which is assigned to an electric motor. However, this often generates high axial forces and requires these for adjustment. Furthermore, a rather cumbersome actuation unit is required, which also has to provide pressure. All of this typically requires additional installation space, which is undesirable.

[0012] Furthermore, a hybrid transmission is known from WO 2018 / 227 310 A1, which can be read as the preamble of claim 1.

[0013] It is the object of the present invention to avoid or even eliminate the disadvantages known from the prior art.

[0014] According to the invention, this object is achieved by a hybrid transmission according to claim 1.

[0015] Wrap-around clutches already exist in a completely different technical field. For example, DE 10 2009 054 672 A1 deals with roll stabilization and uses a wrap-around clutch. This document discloses a device for roll stabilization of a vehicle. A wrap-around clutch is used. This remote prior art discloses a device with a stabilizer that is designed at least in part as a torsion bar and is connected on both sides via stabilizer arms to wheel guides of a wheel axle of the vehicle. At least one locking device is provided, with which at least one region of the stabilizer can be at least partially locked with respect to a vehicle body, wherein the locking device is designed as a wrap-around clutch.

[0016] Fortunately, the surprising use of a wrap-around clutch in this hybrid transmission application has now made it possible to present a space-saving solution with low actuation and axial forces. The very compact arrangement of the two electric motors above or inside each other also makes it possible to create a rotor-integrated solution. The wrap-around clutch is used instead of a wet clutch. The unit is housed below or inside the rotor of the electric motor to save space. Actuation can be implemented, for example, using a friction device such as a friction cone. This results in very low axial forces, and the actuation unit can also be implemented electrically.The belt clutch connects a traction machine, i.e., a second electric motor (E-machine), with a first electric motor (E-machine), which acts as a generator, and with an internal combustion engine in such a way that all operating points and driving situations can be covered by the transmission. The belt clutch is actuated, for example, using a sliding sleeve and a friction cone. The sliding sleeve, for example, is actuated axially using an actuator.

[0017] Advantageous embodiments are claimed in the subclaims and are explained in more detail below.

[0018] The belt clutch is arranged radially and preferably axially within a rotor of the first electric machine and surrounds the second drive shaft.

[0019] It has proven effective to position the second drive shaft concentrically to and within the first drive shaft. This allows for a space-saving arrangement of the two electric motors.

[0020] The overall structure is particularly space-saving when the belt clutch is arranged radially and preferably axially within both rotors of the first electric machine and the second electric machine.

[0021] An advantageous embodiment is also characterized in that the first drive shaft is connected to an internal combustion engine in a certain operating state.

[0022] An advantageous embodiment is also characterized in that in an operating state a differential gear is connected to the second drive shaft in a torque-transmitting manner.

[0023] Different actuators can be used if an actuating unit is assigned to the belt clutch, which is of a mechanical or electrical nature.

[0024] In this context, it is advantageous to have a sliding sleeve which is arranged and dimensioned in such a way that, when the actuating unit is activated, the second drive shaft is increasingly held in place by a spring, the spring being switchably connected to the first drive shaft in a fixed / fixable manner. The spring is permanently connected to the second drive shaft, with increasing twisting of the spring, i.e. an increasingly smaller winding, leading to a tighter contact of the spring against the outer surface of the second drive shaft, whereby greater torques can be transmitted. Strip springs or wire springs have proven to be effective springs. This enables lower actuating forces and space-saving rotor integration. A rotor with a transverse interference fit over a larger diameter is desirable.

[0025] In detail, it is advantageous if the sliding sleeve is designed to displace a friction element, such as a friction cone, towards a counter friction element, preferably at an end of the spring on the sliding sleeve side, wherein the counter friction element is then attached to the spring or is formed by it.

[0026] It has proven to be effective if the sliding sleeve is connected to the first drive shaft in a movable but non-rotatable manner, for example via a toothing.

[0027] The invention is explained in more detail below with the aid of a drawing. A first embodiment of a hybrid transmission according to the invention is described. Shown are: Fig. 1 a schematic layout sketch of a hybrid transmission according to the invention, Fig. 2 a longitudinal section through the belt coupling, as in the embodiment according to Fig. 1 is inserted, and Fig. 3 an isometric view of the wrap-around coupling Fig. 2,

[0028] The figures are merely schematic and serve only to clarify the invention. The same elements are designated by the same reference numerals.

[0029] In Fig. Figure 1 shows a first embodiment of a hybrid transmission 1 according to the invention. A first drive shaft 2 is associated with a first electric motor / electric machine 3. There is also a second drive shaft 4 associated with a second electric motor / electric machine 5. An internal combustion engine is designated by reference numeral 19.

[0030] There is a clutch 6, which is designed as a wrap-around clutch 7. The wrap-around clutch is actuated via an actuating unit 8. The actuating unit 8 has a sliding sleeve 9. The sliding sleeve 9 is axially displaced by an actuator 10.

[0031] As especially in the Fig. 2, the belt clutch 7 has a spring 11. The spring 11 is connected at a first end 12 to the second drive shaft 4. A counter friction element 14 is present at the second end 13 of the spring 11. The counter friction element 14 has a conical outer surface. When the sliding sleeve 9 moves, a friction surface 15 of a friction element / friction cone 20 can be moved towards this conical outer surface. When the two surfaces come into contact, friction is generated, which leads to an increasing twisting of the spring 11, with the result that (more) torque can be transmitted from the first drive shaft 2 to the second drive shaft 4. For actuation by means of the actuator 10, the sliding sleeve 9 has a coupling point 16. The coupling point 16 can be designed as a groove, channel, groove, trough, hole, blind hole, or through hole.

[0032] The spring 11 is arranged radially and axially within a rotor 17 of the first electric machine 3.

[0033] With recourse to Fig. 1, it should be explained that the second electric machine 5, unlike the first electric machine 3, is not designed as an internal rotor, but as an external rotor, so that the corresponding rotor 18 is arranged entirely outside the radially and axially nested electric motor package. A differential gear 21 is used to transfer the torque. In recuperation mode or when starting the internal combustion engine 19 via one of the electric machines 5 and / or 3, the torque curve is also vice versa to the "normal" torque curve described in detail above. This is also desired.

[0034] The Fig. 3 is mainly used to visualize the ribbon-like nature of spring 11. List of reference symbols 1 hybrid transmission 2 first drive shaft 3 first electric machine / first electric machine 4 second drive shaft 5 second electric motor / second electric motor 6 Clutch 7 Wrap-around clutch 8 Actuating unit 9 Sliding sleeve 10 Actuator 11 spring 12 first end of the spring 13 second end of the spring 14 Counter friction element 15 Friction surface 16 coupling point 17 Rotor of the first electric motor 18 Rotor of the second electric motor 19 Internal combustion engine 20 Friction element / friction cone 21 differential gear

Claims

[1] Hybrid transmission (1) with a first drive shaft (2) which is assigned to a first electric machine (3), and with a second drive shaft (4) which is assigned to a second electric machine (5), wherein a clutch (6) is provided for connecting the first drive shaft (2) to the second drive shaft (4) in a torque-transmitting manner, wherein the clutch (6) is designed as a wrap-around clutch (7), characterized by that the belt clutch (7) is arranged radially inside a rotor (17) of the first electric machine (3) and surrounds the second drive shaft (4). [2] Hybrid transmission (1) according to claim 1, characterized by that the second drive shaft (4) is arranged concentrically to and within the first drive shaft (2). [3] Hybrid transmission (1) according to claim 1 or 2, characterized bythat the belt clutch (7) is arranged radially inside both rotors (17, 18) of the first electric machine (3) and the second electric machine (5). [4] Hybrid transmission (1) according to one of claims 1 to 3, characterized by that the first drive shaft (2) is connected to an internal combustion engine (19) in an operating state. [5] Hybrid transmission (1) according to one of claims 1 to 4, characterized by that in an operating state a differential gear (21) is connected to the second drive shaft (4) in a torque-transmitting manner. [6] Hybrid transmission (1) according to one of claims 1 to 5, characterized by that an actuating unit (8) is assigned to the belt clutch (7), which is of a mechanical or electrical nature. [7] Hybrid transmission (1) according to claim 6, characterized bythat a sliding sleeve (9) is provided which is arranged and dimensioned such that, upon activation of the actuating unit (8), it causes the second drive shaft (4) to be increasingly held in place by a spring (11). [8] Hybrid transmission (1) according to claim 7, characterized by that the sliding sleeve (9) is designed to displace a friction element (20) onto a counter friction element (14) on the spring (11).

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