drive unit for a vehicle

Abstract

The invention relates to a drive unit (1) for a vehicle (100) comprising an electric machine (2) with a rotor shaft (3), a transmission (4) with at least a first shaft (5) and a switching element (6) arranged radially inside the rotor shaft (3), an elastic spring element (7) arranged on the switching element (6), and a guide element (8) arranged spatially between the rotor shaft (3), the elastic spring element (7), and the switching element (6), and configured to guide the switching element (6) in the rotor shaft (3) during a switching operation, wherein the switching element (6) is configured to connect at least the first shaft (5) to the rotor shaft (3) in a rotationally fixed manner in a first switching position in order to feed a drive power of the electric machine (2) into the transmission (4), wherein the elastic spring element (7) is configured toto center the switching element (6) in the rotor shaft (3) when the electrical machine (2) is not under load and to enable a compensating movement of the switching element (6) in the rotor shaft (3) when the electrical machine (2) is under load.

Description

The invention relates to a drive unit for a vehicle comprising an electric machine and a transmission having a shift element. The invention further relates to a vehicle having such a drive unit.For example, DE 10 2019 205 747 A1 discloses a drive train with a transmission, comprising an input shaft, a first output shaft, a second output shaft, a first planetary gear set and a second planetary gear set connected to the first planetary gear set. The planetary gear sets each include a plurality of elements. The transmission further comprises a third planetary gear set comprising three elements and two shift elements. A first shift element is designed to block the third planetary gear set by connecting two of its elements in a rotationally fixed manner. A second shift element is configured to fix a first element of the third planetary gear set to the torque-proof component.It is generally known that a switching element which couples two shafts to one another can rattle during rotation in a load-free state of the shafts on account of a tilting in the toothed engagement. As soon as a load, in particular a torque, is introduced, the shifting element is braced and centered via the tooth meshings, so that no rattling occurs any longer.The object of the present invention is to provide an alternative drive unit with a transmission and a shifting element for a vehicle. In particular, a rattle of the switching element in a load-free state is to be prevented. The object is achieved by a drive unit having the features of independent claim 1. advantageous embodiments are the subject matter of the dependent claims, the following description and the figures.A drive unit for a vehicle according to the invention comprises an electric machine having a rotor shaft, a gear mechanism having at least one first shaft and a switching element which is arranged radially inside the rotor shaft, an elastic spring element which is arranged on the switching element, and a guide element which is arranged spatially between the rotor shaft, the elastic spring element and the switching element and is configured to guide the switching element in the rotor shaft during a switching operation, wherein the switching element is configured to connect at least the first shaft to the rotor shaft in a rotationally fixed manner in a first switching position in order to feed a drive power of the electric machine into the gear mechanism, wherein the elastic spring element is configured to center the switching element in the rotor shaft in a no-load state of the electric machine and to enable a compensating movement of the switching element in the rotor shaft in a state of the electric machine under load. For example, the elastic spring element is designed as a quad ring, i.e. as a round cord ring with a substantially square cross-sectional area.In other words, the elastic spring element has a spring-elastic effect and, by elastic deformation, on the one hand, allows the switching element to be centered in the rotor shaft in a no-load state of the electric machine and, on the other hand, allows a compensating movement of the switching element in the rotor shaft in a state of the electric machine under load. In particular, the spring element is prestressed between the guide element and the switching element, so that it can elastically deform under the action of force. This results in an alignment of the switching element with respect to the rotor shaft, so that the switching element cannot tilt and thus also cannot rattle in the no-load state. In the no-load state of the electric machine, the electric machine is essentially not energized and thus does not generate any drive power, but is dragged along by the first shaft by the rotationally fixed connection via the shifting element to the first shaft.The guide element, which is preferably made of a plastic with good sliding properties, comes to bear directly against the rotor shaft and is supported both on the spring element and on the switching element. This not only reduces wear on the spring element, but also the friction between the switching element and the rotor shaft during a switching process.According to a preferred embodiment, the guide element comes to bear at least partially, in particular temporarily, against the rotor shaft, against the elastic spring element and against the switching element, wherein the elastic spring element comes to bear against the guide element and against the switching element. In a no-load state of the electric machine, the guide element comes to bear, for example, only on the spring element and on the rotor shaft, since the spring element is substantially not compressed, but rather is prestressed only between the switching element and the guide element. In contrast, in a state of the electric machine under load, the guide element comes to bear, for example, against the spring element, against the switching element and against the rotor shaft, wherein the spring element is compressed by the guide element.A "rotor shaft" is understood in the present case to mean a component which is connected in a rotationally fixed manner to the rotor of the electric machine, in particular a clutch component which is arranged between the shift element and the rotor, or a shaft which is arranged between the shift element and the rotor. A "shaft" is understood in the sense of the invention to mean a rotatable component of the transmission, via which respective associated components of the transmission are connected to one another in a rotationally fixed manner or via which such a connection can be produced when one of the shift elements is actuated. The respective shaft can connect the components to one another axially or radially or also both axially and radially. Thus, the respective shaft can also be present as an intermediate piece, via which a respective component is connected, for example, radially. The term "shaft" does not exclude that the components to be connected can be embodied in one piece. In particular, two or more shafts connected to one another in a rotationally fixed manner can be formed in one piece.According to a preferred embodiment, the guide element and the elastic spring element are arranged at least partially in a circumferential groove on the switching element. The groove preferably has a first encircling depression which is configured to at least partially accommodate the guide element, and a second encircling depression which is arranged within the first encircling depression and is configured to at least partially accommodate the spring element. Accordingly, the groove consists of two circumferential channels. In particular, the guide element protrudes at least partially radially out of the first depression or the first channel of the groove in order to contact the rotor shaft. In particular, the spring element protrudes at least partially radially out of the second depression or the second channel of the groove in order to contact the guide element. For example, the groove is formed outside a toothed section on the shift element. In particular, the groove is formed axially adjacent to a single toothing section on the shifting element and thus only adjoins a toothing section on one side.According to a preferred embodiment, the guide element and the elastic spring element are designed as a composite ring. Consequently, the guide element and the elastic spring element are combined to form a common component, as a result of which in particular the mounting on the switching element is simplified. The composite ring thus implements two functions, namely on the one hand the elastic spring function in order to center the switching element in the rotor shaft in a no-load state of the electric machine and to enable a compensating movement of the switching element in the rotor shaft in a state of the electric machine under load, and a guide function for guiding the switching element in a low-wear manner during a switching process within the rotor shaft. For example, the guide element and the elastic spring element are connected to one another in a materially integral manner.According to a preferred embodiment, the elastic spring element is formed from an elastomer and has a restoring force which is greater than the sum of a weight force and an imbalance force of the switching element in order to center a center of mass of the switching element in the rotor shaft. The weight force of the shift element corresponds substantially to the mass of the shift element, wherein the imbalance force is dependent on a rotational speed of the shift element. Through deaxation of the switching element with respect to the rotor shaft, an imbalance arises which is intended to be compensated by means of the spring element in a load-free state of the electric machine by centering the switching element with respect to the rotor shaft. In particular, the elastic spring element and the guide element are arranged eccentrically on the switching element.A "shifting element" is understood to mean a shiftable device which, in a closed state, connects two shafts or one shaft and a stationary component to one another in a rotationally fixed manner and, in an open state, decouples the two shafts or the shaft and the stationary component from one another. Two shafts can then rotate relative to each other. According to a preferred embodiment, the shifting element is designed as a form-fitting shifting element. For example, a form-fitting shifting element is designed as a claw clutch. By means of positively locking shift elements, the efficiency of the transmission can be increased on account of reduced drag losses. In particular, form-locking shift elements are more compact and efficiency-optimized and have a cost advantage compared to frictionally engaging shift elements.According to a preferred embodiment, the shifting element is designed as a sliding sleeve with several shifting positions and is axially displaceable by an actuator into the respective shifting position. For example, the actuator can axially displace the sliding sleeve from a first switching position into a second switching position, wherein at least one of the switching positions is provided for the introduction of a drive power. In particular, one of a plurality of shift positions can be a neutral position for decoupling the rotor shaft. For example, one of a plurality of shift positions may be a gear position. In particular, the sliding sleeve has a neutral position axially between two gear positions. The sliding sleeve preferably has form-fitting claws which, in the respective gear position, interact in a form-fitting manner with a respective corresponding claw toothing in order to set a rotationally fixed connection between two shafts or a shaft and a stationary component.According to a preferred embodiment, a shift fork of the actuator is arranged at a first axial end section of the sliding sleeve, wherein a first toothed section for engagement on the first shaft is arranged at a second axial end section of the sliding sleeve, wherein a second toothed section for engagement on the rotor shaft is arranged at a third section of the sliding sleeve arranged between the first and the second axial end section. In particular, the second toothed section has an increased toothed play on account of a deposit in the toothing, wherein the elastic spring element centers the switching element in the rotor shaft in a no-load state of the electric machine and compensates for this toothed play. For example, the third section is arranged eccentrically on the sliding sleeve.According to a preferred embodiment, the drive unit further comprises a second shaft, wherein a third toothed portion is provided on the sliding sleeve for engagement on the second shaft and is arranged at an intermediate portion between the second axial end portion and the third portion of the sliding sleeve. For example, the first and the second toothed section are arranged on an outer circumferential surface of the sliding sleeve, wherein the third toothed section is arranged on an inner circumferential surface of the sliding sleeve. In particular, the engagement of the shift fork of the actuator takes place on the outer circumferential surface of the shift element.According to a preferred embodiment, the rotor shaft is rotatably mounted on a stationary component via a first bearing, wherein the first shaft is rotatably mounted on the stationary component via a second bearing. For example, the stationary component is a housing or a component which is connected to the housing in a rotationally fixed manner and is thus fixed in a stationary manner. The first bearing is supported on the housing in particular by an inner ring, wherein the second bearing is supported on the housing by an outer ring. The switching element, the rotor shaft and the first shaft are arranged coaxially with respect to one another, wherein the deaxation is also dependent on the coaxiality tolerances of the shafts to be connected. These coaxiality tolerances must also be taken into account in the design of the elastic spring element.A vehicle according to the invention comprises at least one drive unit according to the invention. The above definitions and statements regarding technical effects, advantages and advantageous embodiments of the drive unit according to the invention also apply analogously to the vehicle according to the invention.An advantageous embodiment of the invention is shown in the drawings, wherein the same or similar elements are provided with the same reference numerals. The following are shown: FIG. 1 is a greatly abstract schematic view of a vehicle having a drive axle that includes a drive unit according to the invention; and FIG. 2 shows a greatly abstract schematic view of the drive unit according to the invention.FIG. 1 shows a vehicle 100 having a first axle 101 with two vehicle wheels R 1, R 2 and a second axle 102 with two vehicle wheels R 3, R 4. In the present case, the first axle 101 is designed as a rear drive axle of the vehicle 100 and is equipped with a drive unit 1 according to the invention. The drive unit 1 comprises an electric machine 2, which is configured to generate a drive power, and a transmission 4. The drive unit 1 is arranged transversely to the vehicle longitudinal direction and is operatively connected to the vehicle wheels R 1, R 2 of the first axle 101 in a drive-effective manner. In the present case, no further drive unit is arranged on the second axle 102, that is to say on the front axle of the vehicle 100, as a result of which costs, weight and installation space are saved. Alternatively, the drive unit 1 may be disposed on the front axle of the vehicle 100 instead of on the rear axle. To implement an all-wheel drive system, a further drive unit can be arranged on the second axle 102 and be connected in a drive-effective manner to the vehicle wheels R 3, R 4 of this axle 102.FIG. 2 shows the drive unit 1 according to FIG. 1. the electric machine 2 has a rotor 19 which is connected to a shift unit 6 of the transmission 4 via a rotor shaft 3, and a stator. The rotor shaft 3 is designed in the present case as a coupling body between the switching element 6 and the rotor 19. The shifting element 6 is designed as a sliding sleeve. The transmission 4 further comprises a first shaft 5 and a second shaft 18. The rotor shaft 3, the switching element 6 and the first and second shafts 5, 18 are arranged coaxially with respect to one another, wherein the switching element 6 is arranged radially inside the rotor shaft 3 and the first shaft 5. In the present shift position, the shift element 6 connects the first shaft 5 to the rotor shaft 3 in order to feed a drive power of the electric machine 2 into the transmission 4 when the electric machine 2 is energized.An elastic spring element 7 and a guide element 8 are arranged in a circumferential groove 9 on the switching element 6, wherein the guide element 8 is arranged spatially between the rotor shaft 3, the elastic spring element 7 and the switching element 6 and is configured to guide the switching element 6 in the rotor shaft 3 during a switching process. For this purpose, the guide element 8 is formed from a plastic ring with good sliding properties. Furthermore, the elastic spring element 7 is configured to center the switching element 6 in the rotor shaft 3 in a no-load state of the electric machine 2, i.e. when the electric machine does not generate a drive power, and to enable a compensating movement of the switching element 6 in the rotor shaft 3 in a state of the electric machine 2 being under load, i.e. when the electric machine 2 generates a drive power.In the present case, the groove 9 has a first encircling depression which at least partially accommodates the guide element 8, and a second encircling depression which is arranged within the first encircling depression and at least partially accommodates the spring element 7. The groove 9 therefore consists of two circumferential channels, namely a first channel for the guide element 8 and a second channel for the spring element 7. in particular, the guide element 8 protrudes radially partially from the first depression or the first channel of the groove 9 in order to contact the rotor shaft 3. Furthermore, the spring element 7 partially protrudes radially out of the second depression or the second channel of the groove 9 in order to contact the guide element 8.The guide element 8 is configured to come to bear against the rotor shaft 3, against the elastic spring element 7 and against the switching element 6, wherein the elastic spring element 7 is configured to come to bear against the guide element 8 and against the switching element 6. In a no-load state of the electric machine 2, the guide element 8 comes to bear only on an outer circumferential surface of the spring element 7 and on an inner circumferential surface of the rotor shaft 3, since the spring element 7 is substantially not compressed, but rather is elastically prestressed only between the guide element 8 and the switching element 6. In contrast, in a state of the electric machine 2 under load, the guide element 8 comes to bear not only on the outer circumferential surface of the spring element 7 and on the inner circumferential surface of the rotor shaft 3, but also on the outer circumferential surface of the switching element, in particular radially in the groove 9, since the spring element 7 is compressed to the maximum. Due to the radial support of the guide element 8 in the groove 9, the spring element 7 cannot be compressed any further and is thereby protected from damage due to over-compression, i.e. from over-deformation.The guide element 8 and the elastic spring element 7 are preferably designed as a composite ring, i.e. as a component, as a result of which the mounting on the switching element 6 is simplified. The shifting element 6 is designed as a sliding sleeve with several shifting positions and is axially displaceable by an actuator 10 into the respective shifting position. In the present case, the sliding sleeve has three switching positions. According to the first shift position, in which the sliding sleeve is located in the present case, the first shaft 5 and the rotor shaft 3 are connected in a rotationally fixed manner via the sliding sleeve and rotate at a common rotational speed. When the sliding sleeve is axially displaced by the actuator 10, the first shaft 5 and the rotor shaft 3 are decoupled from one another, wherein the sliding sleeve is then present in a neutral position and is only connected to the rotor shaft 3 in this second switching position. If the sliding sleeve is displaced further axially by the actuator 10, the second shaft 18 and the rotor shaft 3 are connected to one another in a rotationally fixed manner and rotate at a common rotational speed, wherein the sliding sleeve is then present in a third switching position.For axial displacement of the sliding sleeve, a shifting fork 11 of the actuator 10 engages a first axial end section 12 of the sliding sleeve. A first toothed portion for engagement with the first shaft 5 is arranged at a second axial end portion 13 of the sliding sleeve. A second toothed section for engagement on the rotor shaft 3 is arranged on a third section 14 of the sliding sleeve arranged between the first and the second axial end section 12, 13. A third toothed portion on the sliding sleeve, which is provided for engagement on the second shaft 15, is arranged at an intermediate portion between the second axial end portion 13 and the third portion 14 of the sliding sleeve. The groove 9 with the composite ring is formed eccentrically and axially adjacent to the second toothed section on the sliding sleeve. The sliding sleeve extends parallel to a rotational axis 20 from the actuator 10 through the rotor shaft 3 to the first shaft 5.The rotor shaft 3 is rotatably mounted via a first bearing 16 on a stationary component designed as a housing 21, wherein the first shaft 5 is rotatably mounted on the stationary component via a second bearing 17. The first bearing 16 is supported with an inner ring on the housing 21, wherein the second bearing 17 is supported with an outer ring on the housing 21. The switching element 6, the rotor shaft 3 and the first shaft 5 are arranged coaxially with respect to one another, wherein a deaxation of the switching element 6 also depends on the coaxiality tolerances of these shafts. The elastic spring element 7 is formed from an elastomer with a spring-elastic effect and thereby enables an elastic deformation in order to center the switching element 6 in the rotor shaft 3 in a no-load state of the electric machine 2 and to enable a compensating movement of the switching element 6 in the rotor shaft 3 in a state of the electric machine 2 being under load. This results in an alignment of the switching element 6 with respect to the rotor shaft 3, so that the switching element 6 cannot tilt and thus also cannot rattle in the load-free state. In particular, the spring element 7 has a restoring force which is greater than the sum of a weight force and an imbalance force of the switching element 6, in order to center the center of mass of the switching element 6 in the rotor shaft 3. As soon as a load is introduced into the switching element 6, a controlled compression of the spring element 7 and a compensating movement of the switching element 6 in the rotor shaft 3 take place via the guide element 8.Reference numerals denote reference numerals1 Drive unit 2 Electric machine 3 Rotor shaft 4 Transmission 5 First shaft 6 Shifting element 7 Elastic element 8 Guide element 9 Groove 10 Actuator 11 Shifting fork 12 First axial end section of the sliding sleeve 13 Second axial end section of the sliding sleeve 14 Third section of the sliding sleeve 15 Fourth section of the sliding sleeve 16 First bearing 17 Second bearing 18 Second shaft 19 Rotor 20 Rotational axis 21 HousingReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2019 205 747 A1

[0002]

Claims

Drive unit (1) for a vehicle (100) comprising an electric machine (2) having a rotor shaft (3), a gear mechanism (4) having at least one first shaft (5) and a switching element (6) arranged radially inside the rotor shaft (3), an elastic spring element (7) arranged on the switching element (6), and a guide element (8) arranged spatially between the rotor shaft (3), the elastic spring element (7) and the switching element (6) and configured to guide the switching element (6) in the rotor shaft (3) during a switching operation, wherein the switching element (6) is configured to connect at least the first shaft (5) to the rotor shaft (3) in a rotationally fixed manner in a first switching position in order to feed a drive power of the electric machine (2) into the gear mechanism (4), wherein the elastic spring element (7) is configured to guide the switching element (6) during a switching operation, in a no-load state of the electric machine (2) to center the switching element (6) in the rotor shaft (3) and in a state of the electric machine (2) under load to enable a compensating movement of the switching element (6) in the rotor shaft (3).Drive unit (1) according to claim 1, wherein the guide element (8) and the elastic spring element (7) are arranged at least partially in a circumferential groove (9) on the switching element (6).Drive unit (1) according to one of the preceding claims, wherein the guide element (8) comes to bear at least partially on the rotor shaft (3), on the elastic spring element (7) and on the switching element (6), wherein the elastic spring element (7) comes to bear on the guide element (8) and on the switching element (6).Drive unit (1) according to one of the preceding claims, wherein the guide element (8) and the elastic spring element (7) are designed as a composite ring.Drive unit (1) according to one of the preceding claims, wherein the shift element (6) is designed as a sliding sleeve with a plurality of shift positions and can be axially displaced into the respective shift position by an actuator (10).Drive unit (1) according to claim 5, wherein a shift fork (11) of the actuator (10) is arranged at a first axial end section (12) of the sliding sleeve, wherein a first toothing section for engagement on the first shaft (5) is arranged at a second axial end section (13) of the sliding sleeve, wherein a second toothing section for engagement on the rotor shaft (3) is arranged at a third section (14) of the sliding sleeve arranged between the first and the second axial end section (12, 13).Drive unit (1) according to claim 6, further comprising a second shaft (15), wherein a third toothed portion is provided on the sliding sleeve for engagement on the second shaft (15) and is arranged on an intermediate between the second axial end portion (13) and the third portion (14) of the sliding sleeve.Drive unit (1) according to one of the preceding claims, wherein the rotor shaft (3) is rotatably mounted on a stationary component via a first bearing (16), wherein the first shaft (5) is rotatably mounted on the stationary component via a second bearing (17).Drive unit (1) according to one of the preceding claims, wherein the elastic spring element (7) is formed from an elastomer and has a restoring force which is greater than the sum of a weight force and an imbalance force of the switching element (6) in order to center a center of mass of the switching element (6) in the rotor shaft (3).Vehicle (100) comprising at least one drive unit (1) according to one of the preceding claims.

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