Wheel decoupling device for a motor vehicle

Abstract

Wheel decoupling device (1) for a motor vehicle, comprising a drive element (4), a driven element (5), a shift sleeve (6) slidably arranged and rotationally fixed to the drive element (4) and the driven element (5), and an actuating device (7) acting on the shift sleeve (6), wherein in a decoupling state of the actuating device (7) the drive element (4) and the driven element (5) are rotationally decoupled from each other and in a coupled state of the actuating device (7) the shift sleeve (6) positively and rotationally connects the drive element (4) and the driven element (5) to each other, wherein the actuating device (7) further comprises a ramp system (8) and the ramp system (8) is designed such thatthat when an adjusting gear (9) is rotated, a sliding ring (10) axially fixed to the switching sleeve (6) is displaced axially between a first position corresponding to the decoupling state and a second position corresponding to the coupling state, characterized in that the switching sleeve (6) has a sleeve area (15) with a toothing (16) of constant diameter, wherein this toothing (16) is positively connected in the direction of rotation in the second position to both a mating toothing (17a) of the drive element (4) and to a mating toothing (17b) of the output element (5).

Description

The invention relates to a wheel decoupling device for a motor vehicle, that is, a device for selectively decoupling / coupling a wheel / wheel hub of a motor vehicle from / to a drive shaft. The invention also relates to a drive unit with this wheel decoupling device. The object of the invention is to provide a decoupling device located as close as possible to the tires in order to enable efficient operation of a motor vehicle, in particular optimal coasting operation. The decoupling device should therefore be as compact as possible and at the same time be controllable quickly and precisely. This is achieved according to the invention by the subject matter of claim 1. A wheel decoupling device for a motor vehicle is claimed, comprising a drive element, a driven element, a shift sleeve slidably arranged and rotationally fixed to the drive element and the driven element, and an actuating device that acts on the shift sleeve in an adjusting manner. In a coupled state of the actuating device, the drive element and the driven element are rotationally decoupled from each other, and in a decoupling state of the actuating device, the shift sleeve connects the drive element and the driven element to each other in a positively locking rotational manner (in the direction of rotation) and is rotationally fixed.The actuating device further comprises a ramp system, wherein the ramp system is designed such that when an adjusting gear (of the actuating device) is rotated, a sliding ring (of the actuating device) supported axially fixed on the shift sleeve is moved axially between a first position corresponding to the decoupling state and a second position corresponding to the coupling state. This provides a positive-locking wheel decoupling device that requires minimal installation space and can therefore be integrated directly into or near a wheel hub of a motor vehicle, saving space. This allows a wheel of the vehicle to be decoupled during operation, which significantly increases efficiency, especially when the vehicle is coasting. Further advantageous embodiments are claimed in the dependent claims and are explained in more detail below. Therefore, it is also advantageous if the adjusting gear and / or the sliding ring have a ramp contour that rises in the circumferential / rotational direction. This allows the ramp system to be designed as compactly as possible. Furthermore, to ensure the least wear-prone operation of the ramp system, it is advantageous if the adjusting gear and the sliding ring are indirectly supported against each other in the axial direction by at least one, preferably several, rolling elements arranged in the circumferential direction, for example shaped as balls. It is also advantageous if at least one rolling element rests directly against a ramp contour of the adjusting gear and / or a ramp contour of the sliding ring. This keeps the design of the actuating device as simple as possible. If the shift sleeve is pre-tensioned into the first position, preferably by means of a (first, mechanical) spring unit, a “normally-stay” disconnect function for decoupling the drive train is implemented directly at the wheels using easily manufactured means. If the sliding ring is supported on the shift sleeve by means of a (second, mechanical) spring unit, the ramp system is in turn subjected to a certain axial preload force, which further reduces wear. Therefore, it is advantageous if the shift sleeve is elastically / resiliently / flexibly pre-tensioned into the second position / axially in the direction of the second position by means of the (second, mechanical) spring unit, and if the sliding ring is elastically / resiliently / flexibly supported on the shift sleeve. The (second, mechanical) spring unit preferably comprises at least one wave spring. A further preferred feature is an axial thrust bearing located between the sliding ring and the shift sleeve. This ensures defined compliance in the event of tooth-to-tooth contact (between the teeth of the shift sleeve and the mating teeth of the output element). An elastic / springy / compliant preload of the switching sleeve into the first position / axially in the direction of the first position is advantageously achieved directly by means of the (first, mechanical) spring unit. If the adjusting gear is axially fixed to a housing, preferably by means of an axial bearing, the actuating device is stably mounted in the housing. It is also advantageous if the shift sleeve has a sleeve section with a toothed section of constant diameter, preferably designed as internal teeth, which, in the second position, is positively engaged in the direction of rotation with both a mating toothed section of the drive element and a mating toothed section of the driven element. This allows the shift sleeve to be kept as simple as possible in its design. If the adjusting gear is driven by an electric actuator, the wheel decoupling device is operated as efficiently as possible during the operation of the motor vehicle. Furthermore, the invention relates to a drive unit for a motor vehicle, comprising a drive shaft (preferably designed as an output of a tripod), a wheel hub and a wheel decoupling device according to the invention, which is received in a steering knuckle, according to at least one of the embodiments described above, wherein the drive element of the wheel decoupling device is connected to the drive shaft or is formed directly by the drive shaft and the output element of the wheel decoupling device is connected to the wheel hub or is formed directly by the wheel hub. In other words, according to the invention, a wheel disconnection unit (wheel decoupling device) is designed by means of which the wheel is disconnected or connected to the rest of the drivetrain depending on the respective driving operation of the motor vehicle. By moving a shift sleeve, the drive-side gearing (first mating gear) of the tripod is positively connected to the driven-side gearing (second mating gear) of the hub. The axial displacement of the shift sleeve is achieved by a ramp system, which converts a rotary movement into an axial movement. The ramp system consists of an adjusting gear, balls (rolling elements), and an axially displaceable ramp (sliding ring). The raceways of the balls can be designed according to the required travel distance. The invention will now be explained in more detail below using figures. Figure 1 shows a longitudinal section of a wheel decoupling device according to the invention in a preferred embodiment, wherein the wheel decoupling device is already installed in a drive unit of a motor vehicle having a steering knuckle and is arranged in a decoupling state / open state; Figure 2 shows a longitudinal section of the wheel decoupling device according to Figure 1, wherein the wheel decoupling device is arranged in a coupling state / closed state; and Figure 3 shows a perspective view of a drive unit having a wheel decoupling device according to Figure 1, wherein an actuator actuating the wheel decoupling device is also shown. The figures are purely schematic and serve solely to illustrate the invention. The same elements are identified by the same reference symbols. Figure 1 shows a detailed view of a wheel decoupling device 1 according to the invention. The wheel decoupling device 1 is a decoupling device in the sense of a coupling / disconnecting coupling for separating a wheel / a wheel hub 2, which is non-rotatably connected to the wheel of the motor vehicle, from the adjacent rotating components of the drive train, here a drive shaft 3. The wheel decoupling device 1 is therefore installed directly between the drive shaft 3 and the wheel hub 2 of a motor vehicle. The drive shaft 3 is further designed as a component (output / a component facing the wheel) of a driveshaft, namely a tripod. Furthermore, it can be seen that a housing 14 of the wheel decoupling device 1 is directly received / integrated into a steering knuckle 19 of a wheel suspension. The following terms axial / radial and circumferential direction denote different directions, which are to be understood in relation to a central axis of rotation 23. The axis of rotation 23 forms the axis of rotation of the wheel hub 2 and the drive shaft 3. Axial direction refers to a direction along / parallel to the axis of rotation 23, radial direction to a direction perpendicular to the axis of rotation 23, and circumferential direction to a direction along a circle concentric with the axis of rotation 23. The wheel decoupling device 1 is shown in Fig. 1 in a decoupling / open state and in Fig. 2 in a coupling / closed state. The wheel decoupling device 1 is designed as a positive-locking coupling. The wheel decoupling device 1 has a shift sleeve 6 which is displaceable relative to an end of the drive shaft 3, designated as the drive element 4, and an end of the wheel hub 2, designated as the output element 5. The shift sleeve 6 has internal teeth 16 which mesh with mating teeth 17a, 17b of the drive element 4 and the output element 5 and can be positively locked to them in a rotationally fixed manner. As shown in Fig. 1, the shift sleeve 6 is shifted into a first position corresponding to the decoupling state, in which its teeth 16 are only in mesh with the first mating teeth 17a of the drive element 4, but are disengaged from the second mating teeth 17b of the output element 5. This first position is supported by a first spring unit 13, which will be described in more detail below. In a second position corresponding to the coupled state, the shift sleeve 6 is axially shifted relative to the first position to such an extent that the teeth 16 are in rotationally fixed, positive-locking contact with both the first mating teeth 17a and the second mating teeth 17b. In the coupled state / second position, the shift sleeve 6 thus connects the drive element 4 and the output element 5 in a rotationally fixed manner. It should also be noted that the toothing 16 of the switching sleeve 6 has a constant (inner) diameter. Therefore, the mating toothing 17a, 17b preferably also have the same (outer) diameter. An actuating device 7 is provided for actuating / moving the switching sleeve 6 between its first and second positions. The actuating device 7 has a ramp system 8. The ramp system 8 further comprises an adjusting gear 9 and a sliding ring 10. In addition, the ramp system 8 has several circumferentially distributed rolling elements 12, which are in this case shaped as balls. The adjusting gear 9 is axially engaged / supported against the sliding ring 10 via the rolling elements 12. A comparison of Figures 1 and 2 shows that both the adjusting gear 9 and the sliding ring 10 form ramp contours 11a, 11b, which directly form the raceway for the rolling elements 12. Each ramp contour 11a, 11b rises continuously along its circumferential extent. The ramp contours 11a, 11b rise in opposite directions in a circumferential direction. The ramp contours 11a, 11b are therefore designed as spindle-shaped / helical tracks. The ramp contours 11a, 11b are aligned such that when the adjusting gear 9 is rotated in a first direction relative to the sliding ring 10, the rolling elements 12 roll along the ramp contours 11a, 11b, thereby pushing the sliding ring 10 away from the adjusting gear 9. When the adjusting gear 9 is rotated in the opposite direction in a second direction, the sliding ring 10 is again moved back towards the adjusting gear 9. This results in the corresponding decoupling or coupling state of the wheel coupling device 1 by rotating the adjusting gear 9. The sliding ring 10 is also mounted on the housing 14 in a rotationally fixed manner. It can also be seen that the sliding ring 10 is supported on the side facing away from the adjusting gear 9 / the rolling element 12 on the switching sleeve 6. For this purpose, the sliding ring 10 is supported radially outside the sleeve area 15, which has the teeth 16, by means of a (first) axial bearing 24a and a (second) spring unit 25 on the switching sleeve 6. The shift sleeve 6 is spring-loaded relative to the housing 14 in the axial direction opposite to the sliding ring 10. For this purpose, a further (first) spring unit 13 is provided, which serves to press the shift sleeve 6 with an axial preload in the direction of the adjusting gear 9. Regarding the two spring units 13 and 25, it should be noted that they can be designed differently in principle. In this version, the first spring unit 13 has several wave springs. The second spring unit 25 has one wave spring. However, in other versions, other mechanical springs, such as coil springs, disc springs, or spring assemblies, can also be used for the first spring unit 13 and / or the second spring unit 25. The first spring unit 13 is supported on the shift sleeve 6 by means of a (second) axial bearing 24b. For clarity, the first spring unit 13 is shown in Fig. 2 with a reduced number of wave springs compared to Fig. 1. Furthermore, a further (third) axial bearing 24c is provided on one side of the adjusting gear 9 facing away from the switching sleeve 6. The adjusting gear 9 is supported on the housing 14 by means of this (third) axial bearing 24c. In conjunction with Fig. 3, which depicts a complete drive unit 20, it should be noted that the adjusting gear 9 is preferably adjustable via a worm gear 21 which can be driven by an electric actuator 18. The actuator 18 is designed as a purely electric actuator 18 (rotary motor). The worm gear 21 preferably engages directly with a toothing of the adjusting gear 9, which is not shown in detail for clarity. With regard to the housing 14, it should also be noted, in light of Fig. 1, that it preferably consists of two parts 29a, 29b, which are joined together in a connection area 22. Here, it is again advantageous if a seal 26, for example in the form of an O-ring, is provided in the connection area 22 / contact area of ​​both parts of the housing 14. A corresponding static seal 27 can also be provided between the axle journal 19 and the housing 14. Furthermore, a radial shaft seal 28 is preferably provided radially between the housing 14 and the drive element 4. In other words, in the wheel decoupling device according to the invention, switching / adjusting this device involves moving a switching sleeve 6 by means of a ramp geometry (ramp contours 11a, 11b). In particular, a return spring (first spring unit 13) is provided for quickly bridging the frictional connection of the wheel decoupling device 1 near the tire. A return spring (second spring unit 25) also serves to center the ramp unit (ramp system 8). The return spring (first spring unit 13) for the decoupling / disconnecting function can also be a disc spring, a spring assembly, or a coil spring. The subject of the application is a wheel decoupling device 1 (in English, "Disconnect Unit (DCU)"), which is integrated directly into the drivetrain between the drive shaft 3 and the hub (wheel hub 2). Depending on the driving conditions, the wheel decoupling device 1 disconnects or connects the wheel to the rest of the drivetrain. By moving the shift sleeve 6, the drive-side gearing (first mating gear 17a) of the tripod is positively engaged with the driven-side gearing (second mating gear 17b) of the hub. The axial displacement of the shift sleeve 6 is achieved by a ramp system 8, which converts a rotational movement into an axial movement. The ramp system 8 consists of an adjusting gear 9, balls (rolling elements 12), and an axially displaceable ramp (sliding ring 10). The raceways (ramp contours 11a, 11b) The balls can be designed according to the required travel distance. The ramp system 8 is actuated by an electric motor (actuator 18) with a worm gear 21, which engages with the adjusting gear 9. The axially displaceable ramp is fixed against rotation in the housing 14 of the wheel decoupling device 1 by a toothed connection. When the adjusting gear 9 is actuated, the balls are displaced axially due to the helical raceways. The rotationally fixed bearing of the ramp results in its axial displacement. The adjusting gear 9 is centered by the pressure angle, which is why no separate radial bearing is necessary. The relative movement of the adjusting gear 9 to the housing 14 is compensated by an axial needle bearing (third axial bearing 24c). In the open position, the shift sleeve 6 engages only with the drive-side teeth (first mating teeth 17a) of the tripod. When the wheel decoupling device 1 is closed, the shift sleeve 6 is displaced in proportion to the axial movement of the ramp. The relative movement between the ramp and the shift sleeve 6 is compensated by a further thrust bearing / thrust needle bearing (first thrust bearing 24a). A wave spring (second spring unit 25) is integrated between the thrust bearing (first thrust bearing 24a) and the shift sleeve 6 to ensure defined compliance in the event of tooth-to-tooth contact. The ramp system 8 requires an axial preload, which is achieved via a wave spring assembly (first spring unit 13). The wave spring (first spring unit 13) is positioned in the housing 14 and connected to the switching sleeve 6 via a further axial bearing / axial needle bearing (second axial bearing 24b). When the switching sleeve 6 is opened by the actuator 18, the wave spring assembly (first spring unit 13) relaxes and pushes the switching sleeve 6 back into its initial state (decoupling state). The wheel decoupling device 1 is completely enclosed and thus protected against ingress of environmental media and leakage of lubricants. The housing 14 is mounted on the wheel axle at several mounting points, which are not shown for clarity. The housing 14 is sealed against the tripod with a dynamic seal (radial shaft seal 28). A static O-ring seal (static seal 27) is installed opposite the steering knuckle 19. Due to the mounting, the housing 14 is split in the area of ​​the mounting points. The flange connection (connection area 22) of the housing 14 is also sealed with an O-ring (seal 26). Reference symbol list 1 Wheel decoupling device 2 Wheel hub 3 Drive shaft 4 Drive element 5 Output element 6 Shift sleeve 7 Actuating device 8 Ramp seal 9 Adjusting gear 10 Sliding ring 11a Ramp contour of the adjusting gear 11b Ramp contour of the sliding ring 12 Rolling element 13 First spring unit 14 Housing 15 Sleeve area 16 Toothing 17a First mating toothing 17b Second mating toothing 18 Actuator 19 Steering knuckle 20 Drive unit 21 Worm gear 22 Connection area 23 Axle of rotation 24 Thrust bearing 25 Second spring unit 26 Seal 27 Static seal 28 Radial shaft seal 29a First part of the housing 29b Second part of the housing

Claims

Wheel decoupling device (1) for a motor vehicle, comprising a drive element (4), a driven element (5), a shift sleeve (6) slidably arranged and rotationally fixed to the drive element (4) and the driven element (5), and an actuating device (7) acting on the shift sleeve (6), wherein in a decoupling state of the actuating device (7) the drive element (4) and the driven element (5) are rotationally decoupled from each other and in a coupled state of the actuating device (7) the shift sleeve (6) positively and rotationally connects the drive element (4) and the driven element (5) to each other, wherein the actuating device (7) further comprises a ramp system (8) and the ramp system (8) is designed such thatthat when an adjusting gear (9) is rotated, a sliding ring (10) axially fixed to the switching sleeve (6) is displaced axially between a first position corresponding to the decoupling state and a second position corresponding to the coupling state, characterized in that the switching sleeve (6) has a sleeve area (15) with a toothing (16) of constant diameter, wherein this toothing (16) is positively connected in the direction of rotation in the second position to both a mating toothing (17a) of the drive element (4) and to a mating toothing (17b) of the output element (5). Wheel decoupling device (1) according to claim 1 , characterized in that the adjusting gear (9) and / or the sliding ring (10) have a ramp contour (11a, 11b) rising in the circumferential direction. Wheel decoupling device (1) according to claim 1 or 2, characterized in that the adjusting gear (9) and the sliding ring (10) are indirectly supported against each other in the axial direction via at least one rolling element (12). Wheel decoupling device (1) according to claim 3, characterized in that the at least one rolling element (12) bears directly against a ramp contour (11a, 11b) of the adjusting gear (9) and / or the sliding ring (10). Wheel decoupling device (1) according to one of claims 1 to 4, characterized in that the switching sleeve (6) is pre-tensioned in the first position. Wheel decoupling device (1) according to one of claims 1 to 5, characterized in that the sliding ring (10) is supported on the shift sleeve (6) by means of a spring unit (13). Wheel decoupling device (1) according to one of claims 1 to 6, characterized in that the adjusting gear (9) is axially fixedly supported on a housing (14). Wheel decoupling device (1) according to one of claims 1 to 7, characterized in that the adjusting gear (9) is driven by means of an electric actuator (18). Drive unit (20) for a motor vehicle, comprising a drive shaft (3), a wheel hub (2) and a wheel decoupling device (1) received in a steering knuckle (19) according to one of claims 1 to 8, wherein the drive element (4) of the wheel decoupling device (1) is connected to the drive shaft (3) or is formed directly by the drive shaft (3) and the output element (5) of the wheel decoupling device (1) is connected to the wheel hub (2) or is formed directly by the wheel hub (2).

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