Drive unit for a hybrid vehicle

Abstract

Drive unit (115) for a hybrid vehicle (100), comprising - an electric drive machine (125) with a housing-fixed stator (130) and a rotatably arranged rotor (135) thereto, - a transmission input shaft (145), - a rotor hub (155) which is rotationally fixed to the rotor (135) and torque-transmittingly coupled to the transmission input shaft (145), wherein the rotor hub (155) is radially centered on the transmission input shaft (145) via two axially spaced centering points (210, 215), - a damper shaft (225), - a housing-mounted bearing shield (240), - a housing-mounted centering plate (260), - a first radial bearing (220) arranged between the rotor hub (155) and the damper shaft (225), - a second radial bearing (230) located between the damper shaft (225) and the transmission input shaft (145), and - a third radial bearing (235) located between the bearing shield (240) and the damper shaft (225).

Description

[0001] The present invention relates to a drive unit for a hybrid vehicle and to a hybrid vehicle with such a drive unit.

[0002] Drive systems for hybrid vehicles require precise coaxial alignment of rotating components to limit imbalance forces and radially acting magnetic forces of electric drive motors. Insufficient radial guidance can lead to radial deflections and angular deviations, which impair the air gap between the rotor and stator and can negatively affect efficiency as well as noise and vibration behavior.

[0003] Precise axial positioning can also be important, for example, to maintain a specified distance between a speed sensor and a sensor ring, and to prevent axial protrusions. Insufficient axial support can cause relative movements and increase tolerance chains, making it more difficult to maintain clearances and creepage distances.

[0004] Drive arrangements are known from the prior art in which a rotor is connected to a gearbox input shaft via a rotor hub and bearing points are provided for radial and axial support. However, under operating load, the support may be insufficiently stiff or not adequately defined, particularly if radial forces are not introduced into a housing via clearly defined bearing points or if the torque application is spatially decoupled from the radial guidance.

[0005] One object of the invention is to provide a drive device in which a rotor hub and a gearbox input shaft are radially and axially defined and rigidly guided in order to reduce radial deflections and angular deviations of the rotating components and to promote stable coaxial alignment even under load. The invention achieves this object by means of the subject matter of the independent claims. Dependent claims describe preferred embodiments.

[0006] According to a first aspect of the invention, a drive device for a hybrid vehicle comprises an electric drive machine with a housing-fixed stator and a rotor rotatably arranged therein; a transmission input shaft; a rotor hub which is rotationally fixed to the rotor and torque-transmittingly coupled to the transmission input shaft, wherein the rotor hub is radially centered on the transmission input shaft via two axially spaced centering points; a damper shaft; a housing-fixed bearing shield; a housing-fixed centering plate; a first radial bearing arranged between the rotor hub and the damper shaft; a second radial bearing arranged between the damper shaft and the transmission input shaft; and a third radial bearing arranged between the bearing shield and the damper shaft.

[0007] The drive unit is a unit comprising at least the electric drive motor, the transmission input shaft, and the rotor hub bearings, and is designed to provide drive torque in a hybrid vehicle. It can be part of the hybrid vehicle's powertrain or constitute the powertrain.

[0008] The electric drive motor has a stator that is supported on the housing in a rotationally and axially fixed manner, and a rotor that is rotatably arranged relative to it. The rotor rotates about an axis of rotation and is rotationally fixed to the rotor hub, so that the rotor and rotor hub rotate together. The rotor hub is coupled to the gearbox input shaft in such a way that a drive torque can be introduced into the gearbox input shaft. The torque-transmitting coupling can be positive-locking and / or friction-locking.

[0009] The gearbox input shaft is designed as the input shaft of a gearbox and serves to introduce drive torque supplied by the electric drive motor into the gearbox. The gearbox is designed to transmit drive power between an input side and an output side, thereby providing a gear ratio.

[0010] The centering elements ensure a coaxial alignment of the rotor hub relative to the transmission input shaft. The axial distance between the two centering elements effectively limits any tilting play of the rotor hub on the transmission input shaft. This effect is amplified as the distance between the centering elements increases. The centering elements are preferably designed as cylindrical centering surfaces on the transmission input shaft with corresponding cylindrical inner surfaces on the rotor hub, or more specifically, as centering shoulders on the transmission input shaft with corresponding bore sections on the rotor hub forming a clearance or transition fit. The centering elements are preferably arranged axially between the bearing shield and the centering plate. The rotor can also be arranged axially between the bearing shield and the centering plate. The housing-mounted bearing shield serves as a bearing support against the housing.The housing-mounted centering plate forms a further reference element that is fixed relative to the housing.

[0011] The damper shaft can be part of a damper assembly, which in particular comprises a damper and a damper hub. The damper is designed to dampen torsional vibrations in the drive unit during operation, thereby reducing excitation and load peaks.

[0012] The radial guidance of the rotating components is achieved via at least three radial bearings at defined bearing locations. The first radial bearing is located between the transmission input shaft and the damper shaft and limits radial relative movement between these two rotating components. The second radial bearing is located between the damper shaft and the housing-mounted bearing shield and guides the damper shaft radially relative to the housing, allowing operational radial forces, particularly radial rotor forces, to be transferred into the housing. The third radial bearing is located between the rotor hub and the damper shaft and limits relative movement between the rotor side and the damper side. This prevents tilting and misalignment of the damper side, especially the damper shaft.

[0013] Radially acting forces, which can arise during operation particularly due to imbalance, radially acting magnetic forces of the electric drive motor, or excitations from the drive train, are thereby introduced into the housing via clearly defined bearing points. This reduces radial deflections and angular deviations, and the coaxial alignment specified by the centering elements can be maintained stably even under load.

[0014] The arrangement combines a coaxially defined, dual centering of the rotor hub on the transmission input shaft with a rigid, defined radial support via three radial bearings that guide the transmission input shaft to the damper shaft, the damper shaft to the housing, and the rotor hub to the damper side. This allows for increased radial accuracy and rigidity of the arrangement, limiting radial deflections and angular deviations, and introducing operational radial forces into the housing via defined load paths.

[0015] Preferably, the second radial bearing is arranged radially inside the third radial bearing. A radial arrangement exists when the second radial bearing has a smaller effective bearing diameter in its radial cross-section than the third radial bearing. This allows for a compact and simultaneously tilt-resistant bearing architecture in which the damper shaft is guided radially and stabilized relative to the bearing shield.

[0016] Preferably, each radial bearing is designed as a needle roller bearing. A needle roller bearing uses needles as rolling elements, thus enabling high radial load capacity with a small radial footprint. The needle roller bearing design, particularly as a needle sleeve, can be implemented for only the first radial bearing, only the second radial bearing, only the third radial bearing, or for two or all radial bearings. This facilitates precise radial guidance while requiring minimal installation space.

[0017] Furthermore, the drive unit preferably comprises a first axial bearing arranged between the rotor hub and the centering plate. An axial bearing is understood to be a bearing designed to transmit axial forces. The first axial bearing is designed to transmit axial rotor forces to the centering plate, thereby providing a defined axial support path and limiting the axial position of the rotor relative to housing-fixed reference elements.

[0018] Furthermore, the drive unit preferably includes a second axial bearing arranged between the rotor hub and the damper shaft. This second axial bearing is designed to transmit axial rotor forces to the damper side, thereby reducing axial relative movements between the rotor hub and the damper shaft and providing defined axial support for the rotor side.

[0019] Furthermore, the drive unit preferably includes a third axial bearing arranged between the damper shaft and the bearing shield. This third axial bearing is designed to transmit axial forces from the damper side to the housing-mounted bearing shield, thereby ensuring a defined axial force transfer into the housing.

[0020] In one embodiment, the second axial bearing is arranged radially inside the third axial bearing. The second axial bearing has a smaller effective bearing diameter in its radial cross-section than the third axial bearing. This allows for a compact axial support architecture in which axial forces are transmitted in stages across several radial planes.

[0021] The respective axial bearing can be designed as a needle roller bearing, analogous to the radial bearings. The needle roller bearing design can be applied to only the first axial bearing, only the second axial bearing, only the third axial bearing, or to two or all axial bearings. This supports the defined axial support path with a minimal installation space requirement.

[0022] In one embodiment, each centering element comprises a cylindrical centering surface on the transmission input shaft and a corresponding cylindrical inner surface on the rotor hub. The cylindrical surfaces enable a very tight-tolerance centering fit, and depending on the design, a rolling bearing for radial guidance between the rotor hub and the transmission input shaft may be omitted.

[0023] Preferably, the rotor hub and the transmission input shaft are coupled via a drive gear for torque transmission. A drive gear is understood to be a gear connection through which torque can be transmitted from the rotor hub to the transmission input shaft.

[0024] Preferably, the drive teeth are arranged axially adjacent to one of the two centering points, and in particular, directly adjacent to it. By arranging the drive teeth axially in close proximity to one of the centering points, the torque application is spatially coupled to the radial guidance of the rotor hub. This reduces lateral forces and tilting moments resulting from the torque transmission, thereby promoting a more stable coaxial alignment of the rotor hub and the gearbox input shaft. Consequently, eccentricities and the resulting imbalance forces can be reduced, and a more uniform load distribution in the gear connection can be achieved.

[0025] The drive teeth can be located on a section of the transmission input shaft that has a comparatively large outer diameter. This allows the transmissible loads to be increased.

[0026] According to one embodiment, the drive unit further comprises an internal combustion engine and a disconnect clutch, wherein the disconnect clutch is configured to transmit a drive torque from the internal combustion engine to the transmission input shaft via the drive teeth when in the closed state. This allows the drive teeth to be used to transmit a combined torque from the electric drive motor and the internal combustion engine, depending on the switching state of the disconnect clutch.

[0027] According to one embodiment, the drive unit further comprises a first fluid transfer point for supplying pressurized oil to the disconnect coupling and a second fluid transfer point for performing dynamic pressure equalization of the disconnect coupling, wherein the two fluid transfer points are arranged axially between the two centering elements. Each fluid transfer point forms an interface for transferring fluid, in particular pressurized oil, between components moving relative to each other.

[0028] By arranging the two fluid transfer points axially between the two centering elements, a compact integration can be achieved in the area of ​​the centering coupling between the rotor hub and the gearbox input shaft.

[0029] At least one channel for dynamic pressure equalization can be fluidically connected to a radial gap between the rotor hub and the transmission input shaft. At least one channel for supplying pressure oil to the disconnect clutch can be fluidically connected to a fluid channel inside the transmission input shaft.

[0030] According to one embodiment, the fluid transfer points each comprise at least one substantially radially extending channel arranged on the rotor hub. A substantially radially extending channel is understood to be a channel whose main extent runs transversely to the axis of rotation.

[0031] According to a second aspect of the invention, a hybrid vehicle comprises a drive device according to the first aspect of the invention, wherein the drive device is configured to transmit a drive torque to a wheel of the hybrid vehicle.

[0032] The drive unit is integrated into the hybrid vehicle's powertrain, allowing the drive torque provided by the drive unit to be transmitted to at least one driven wheel via the aforementioned transmission and a downstream output arrangement. This enables a compact and integrable drive topology in which an electric drive is integrated into the vehicle's powertrain and wheel torque usable for driving can be generated.

[0033] An optional differential can be provided to split the drive torque on the transmission output side between two output shafts, so that two wheels of the hybrid vehicle can be driven.

[0034] The invention will now be described in more detail with reference to the attached figures, in which: Fig. 1 a highly schematic representation of a hybrid vehicle with a drive system according to the invention; and Fig. 2 a longitudinal section view of a part of the drive unit according to Fig. 1 represents.

[0035] Fig. Figure 1 shows a highly schematic representation of a hybrid vehicle 100 with two axles 105 and 110, wherein a drive unit 115 or drive train is effectively arranged on the first axle 105 to rotate the wheels 120 of the axle 105. The drive unit 115 is designed as a hybrid drive axle and comprises an electric working machine 125 with a stator 130 and a rotor 135, a gearbox 140 with a gearbox input shaft 145, and an optional differential 150, which distributes the drive power converted by the gearbox 140 to the two wheels 120 of the first axle 105. The rotor 135 is rotationally fixed to a rotor hub 155, which in turn is connected to the gearbox input shaft 145 to transmit torque.

[0036] Furthermore, the drive unit 115 comprises an internal combustion engine 160 and a disconnecting clutch 165, wherein the disconnecting clutch 165 is configured to transmit a drive torque of the internal combustion engine 160 to the transmission input shaft 145 when closed.

[0037] Fig. Figure 2 shows a longitudinal section view of part of the drive unit 115 according to Fig. 1. The illustration shows, in particular, the bearing arrangement of the rotor 135 of the electric drive motor 125 within a housing 200 and its torque-transmitting coupling to the gearbox input shaft 145 via the rotor hub 155. The rotor hub 155 is torque-transmittingly coupled to the gearbox input shaft 145 by means of a first drive tooth 205. Thus, the rotor 135 is rotationally fixed to the gearbox input shaft 145 via the rotor hub 155.

[0038] The rotor hub 155 is radially centered on the transmission input shaft 145 by means of two axially spaced centering elements 210, 215. The first drive teeth 205 are arranged axially directly adjacent to the second centering element 215. Each centering element 210, 215 consists of a cylindrical centering surface or outer surface of the transmission input shaft 145 and a corresponding cylindrical inner surface of the rotor hub 155. In the illustrated embodiment, the rotor hub 155 is centered directly radially on the transmission input shaft 145.

[0039] The first drive gear 205 is designed to transmit a total torque, whereby in a closed state the in Fig. In the disconnect coupling 165 shown, in addition to the drive torque of the electric drive motor 125, a drive torque of the internal combustion engine 160 can also be transmitted to the transmission input shaft 145.

[0040] The radial support of rotor forces is achieved at least via the radial bearings described below. The rotor hub 155 is guided radially relative to a damper shaft 225 by a first radial bearing 220. The first radial bearing 220 is arranged to limit relative movements between the rotor side and the damper side. The damper shaft 225 is radially supported relative to the transmission input shaft 145 by a second radial bearing 230 and is rotatably mounted to it. The second radial bearing 230 is arranged radially within a third radial bearing 235, the third radial bearing 235 radially supporting the damper shaft 225 relative to a housing-fixed bearing shield 240. In this embodiment, the radial bearings 220, 230, and 235 are each designed as needle bearings, in particular as needle roller bearings. This bearing arrangement enables compact and simultaneously tilt-resistant radial guidance along defined load paths.

[0041] The damper shaft 225 is connected to a damper hub 245 via a second drive tooth 242 in a rotationally fixed manner, and the damper hub 245 is operatively connected to a damper 250.

[0042] The damper shaft 225, the transmission input shaft 145 and the rotor hub 155 are arranged coaxially to a rotation axis 252.

[0043] The axial support of rotor forces is achieved at least via the thrust bearings described below. A first thrust bearing 255, arranged between the rotor hub 155 and a housing-mounted centering plate 260, is shown, as well as a second thrust bearing 265, arranged between the rotor hub 155 and the damper shaft 225. The second thrust bearing 265 is arranged radially within a third thrust bearing 270, which is located between the damper shaft 225 and the bearing shield 240. The thrust bearings 255, 265, and 270 are each designed as needle bearings, in particular as needle sleeves. This stepped bearing arrangement enables a defined axial force transmission along several radially offset support planes.

[0044] The centering elements 210, 215 are arranged axially between the bearing shield 240 and the centering plate 260. A first fluid transfer point 275 for supplying pressurized oil to the disconnecting clutch 165 and a second fluid transfer point 277 for dynamic pressure equalization are provided axially between the two centering elements 210, 215. The first fluid transfer point 275 comprises a first channel 280 formed on the rotor hub 155, extending substantially radially, which fluidically connects the disconnecting clutch 165 to a supply channel 285 formed in the transmission input shaft 145. The second fluid transfer point 277 comprises two further channels 290, 295 formed on the rotor hub 155, extending substantially radially, which fluidically connect the disconnect coupling 165 with a radial gap between the transmission input shaft 145 and an axial section of the rotor hub 155.By arranging both fluid transfer points 275, 277 between the centering elements 210, 215, a compact integration within the torque-free coupling zone of the rotor hub 155 is possible. Reference sign 100 hybrid vehicles 105 first axis 110 second axis 115 Drive unit 120 wheel of the hybrid vehicle 125 electric work machine 130 Stator 135 Rotor 140 gearbox 145 Gearbox input shaft 150 Differential 155 Rotor hub 160 internal combustion engine 165 Disconnect coupling 200 cases 205 first drive gear 210 first centering 215 second centering 220 first radial bearing 225 Damper shaft 230 second radial bearing 235 third radial bearing 240 Storage sign 242 second drive gear 245 damper hub 250 dampers 252 Rotation axis 255 first axial bearing 260 centering plate 265 second axial bearing 270 third axial bearing 275 first fluid transfer point 277 second fluid transfer point 280 first channel 285 Supply channel 290 second channel 295 third channel

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