Coupling unit for the reversible coupling of a drive side with an output side of a drive train

Abstract

Coupling unit for reversibly coupling a drive side (2) with an output side (3) of a drive train, comprising a linearly displaceable switching sleeve (8) which is mounted on a drive element (4) of the drive side (2) and can be moved from a decoupling position via an output element (6) of the output side (3) into a coupling position in which the switching sleeve connects the drive element (4) and the output element (6) in a rotationally fixed manner, wherein an actuator (10) is provided for moving the switching sleeve (8), which has a linearly displaceable piston (13) and a switching rod (17) coupled to the piston (13) and coupled to the switching sleeve (8), as well as a displacement sensor (34) comprising a sensor (35) via which a sensor element (40) arranged on the switching rod (17) and movable with it relative to the sensor (35) can be detected, wherein the sensor element (40) is arranged axially at the end of the switching rod (17),or that the sensor element (40) is mounted on the switching rod (17), wherein the sensor element (40) is covered with a protective cover (41).

Description

The invention relates to a coupling unit for the reversible coupling of a drive side with an output side of a drive train. Such a coupling unit, often also called a "disconnect unit," is used, for example, in the drive systems of a motor vehicle, such as a drive axle, which can also be an electric axle, often called an e-axle. The coupling unit serves to reversibly couple a drive side, where torque is applied, with an output side, to which the torque is to be transmitted and where it is forwarded. It can, for example, be arranged between a drive unit and an intermediate shaft to couple an output of the drive unit, i.e., the drive side, with the input of the intermediate shaft, i.e., the output side.An arrangement between such an intermediate shaft and a differential is also conceivable, in which case the intermediate shaft, at which the torque from the drive is applied, represents the drive side, while the differential, to which the torque is transmitted, represents the output side. The coupling unit can therefore be integrated into such a drive train at different positions. The coupling unit is switchable in order to establish and disengage a torque-tight coupling between the drive and output sides via a controllable switching device, i.e., an actuator. Such a coupling unit connects two toothed elements on the drive and output sides. This means that an externally toothed drive element, for example, a first gear, is arranged on the drive side, while an externally toothed output element, for example, a second gear, is provided on the output side. These are reversibly connected via a coupling element. Such a coupling element is typically in the form of a linearly displaceable shift sleeve, which sits on the drive element (i.e., is located on the drive side) and engages with the external teeth of the drive element via its internal teeth. An actuator allows the shift sleeve to be moved along the external teeth of the drive element and slid over the output element to couple the drive and output sides, so that the internal teeth of the shift sleeve also engage with the external teeth of the output element.The drive element and the driven element are then rotationally fixed to each other via the shift sleeve which encompasses them both and connects them via the gear mesh, so that the torque present on the drive side can be transmitted to the driven side. When the shift sleeve is moved from the drive element onto the output element, tooth-to-tooth contact can occur between the internal teeth of the shift sleeve and the external teeth of the output element. This means that the end face of the internal teeth of the shift sleeve runs against the end face of the external teeth of the output element if the teeth are not gapped at the moment of engagement. This leads, firstly, to a corresponding stress on the entire shifting system, since the actuator continuously applies an axial sliding force to the shift sleeve. Secondly, the engagement process is delayed until the teeth are gapped and the internal teeth are engaged with the external teeth, with this sliding process occurring at the actuating speed generally controlled by the actuator.In this state, the switching sleeve is therefore neither in one nor the other distinguished position that it must assume during operation and in which the respective functions (decoupling, coupling) are defined. For example, the state of the art is cited in CN 2 03 793 128 U, DE 10 2019 219 963 A1 and US 2016 / 0 101 689 A1. The invention is based on the problem of specifying an improved coupling unit. To solve this problem, a coupling unit for the reversible coupling of a drive side with an output side of a drive train with the features of claim 1 is provided according to the invention.In particular, a coupling unit for the reversible coupling of a drive side with an output side of a drive train is provided, comprising a linearly displaceable switching sleeve which sits on a drive element of the drive side and can be moved from a decoupling position via an output element of the output side into a coupling position in which the switching sleeve connects the drive element and the output element in a rotationally fixed manner, wherein an actuator is provided for moving the switching sleeve, which has a linearly displaceable piston and a switching rod coupled to the piston, which is connected to the switching sleeve, as well as a displacement sensor system comprising a sensor by which a sensor element arranged on the switching rod, which is movable with the rod relative to the sensor, can be detected. The invention provides for the integration of a displacement sensor into the actuator or the positioning mechanism, which enables the precise determination of the movement path and thus the position of the switching rod. Since the position of the switching rod directly indicates the position of the switching sleeve, the sleeve position can be determined and recorded very accurately in this way, whether the switching sleeve is in the decoupling position, in which it only sits on the drive element, in the coupling position, in which it has a defined coupling position, in which it connects the drive element to the driven element in a rotationally fixed manner, or in any intermediate position, for example, in axial contact with the drive element's gearing. The actuator, preferably a hydraulic actuator, has a piston that is linearly displaceable within a suitable cylinder housing. The piston is coupled to the switching rod, which in turn is coupled to the switching sleeve, also known as a sliding sleeve, for example via a switching fork or similar device. When the actuator is actuated and the piston is axially displaced, the switching rod and, consequently, the switching fork are also axially displaced. The switching fork then engages the switching sleeve, sliding it over the output element and coupling it. The actuator has a suitable sensor for detecting this movement or change in position, as well as a sensor element arranged on the switching rod.The sensor and sensor element interact, meaning that the sensor can detect the movable sensor element and thus precisely determine its position. The position of the sensor element, in turn, uniquely indicates the position of the switching rod, and this, in turn, uniquely indicates the position of the switching sleeve. The displacement sensor system also includes a control and / or processing unit, which performs the corresponding position detection or evaluation and, if necessary via further connected control and / or processing units, the activation of corresponding functions or operating states associated with the detected positions. In this way, the exact position of the sleeve can be determined. This, in turn, allows for precise determination of whether a decoupling position is present, enabling and controlling an operation associated with this position, such as vehicle coasting, or whether a coupling position is present, allowing torque transmission from the drive to the driven side, which is essential for active torque transmission for propulsion purposes. Position detection thus allows for the reliable detection of the corresponding stable states and the precise engagement state of the shift sleeve. Intermediate positions, i.e., quasi-unstable states with no corresponding operating states, can also be reliably detected. The sensor is advantageously mounted on the outside of the actuator housing, and the sensor element is mounted on a section of the switching rod protruding from the housing. This design simplifies the sensor's placement, as it does not need to be installed inside the housing. Mounting the sensor element on a section of the switching rod protruding from the housing is also advantageous, as it allows the entire position sensor assembly to be located outside the housing. Preferably, the sensor can be arranged on a cover that axially closes the housing. The actuator has a corresponding housing component that essentially defines the housing and is axially closed by a suitable cover. The housing component contains the piston and, optionally, a cylinder insert made of a metal sheet, and similar components. The cover is a separate component that closes the housing. Arranging the sensor on the cover allows, if desired, for the sensor to be pre-mounted there and installed together with the cover, or for the sensor to be subsequently attached to the housing. The sensor can be housed in a sensor casing, which is either inserted into a recess formed by the lid or attached to the lid. This means that the sensor itself, the actual sensing component, is enclosed in a suitable housing where it is adequately protected. The lid can, for example, have a corresponding recess for this casing, meaning that it has a suitable recess geometry that allows for a positive-locking fit of the sensor casing. Alternatively, the sensor casing can be directly mounted and attached to the lid, for example, axially. If the sensor housing is placed in a receptacle on the lid, this receptacle can be formed on the end face of the lid. Alternatively, such a receptacle can also be provided in a bore on the lid through which the switching rod extends, with the sensor located in the bore, i.e., within the receptacle. The sensor housing, positioned in the radial receptacle on the bore side, can, for example, be glued in place. In any case, the magnetic element would have to be located nearby. Another mounting option, as described, is on the end face of the lid. For this purpose, the sensor housing can have a mounting section by which it is axially fixed to the lid, preferably by means of a mounting screw that secures the lid to a housing component. The sensor housing is thus placed axially on the lid and can be fixed accordingly via the mounting section.The cover is preferably secured using a mounting screw, which is already used to fix it to the housing component. Gluing it on would also be conceivable. If the sensor or sensor housing is mounted axially onto the cover, the sensor housing can advantageously be L-shaped, with a first leg forming the mounting section and a second leg forming a retaining section for the sensor, extending along the switching rod. Viewed from the side, the sensor housing is therefore L-shaped and is screwed to the cover with its first leg, for example, using the mounting screw. The design is such that the second leg, which forms the retaining section on which the actual sensor is located, extends as close as possible to the switching shaft and along its length. In this case, the magnetic element must again be positioned accordingly on the switching shaft. The sensor element itself can be arranged on the shift rod in various ways. According to the invention, it can be arranged axially at the end of the shift rod, i.e., attached to it in line with the shift rod, preferably by gluing. In this case, since the shift shaft extends at least through the bore on the cover side, the sensor element is necessarily located somewhat away from the cover, so an L-shaped sensor housing should be used in this case. Alternatively, according to the invention, the sensor element can also be mounted on the shift rod, i.e., arranged on the outer circumference of the shift rod. It can be a local element or a circumferential ring that runs around the entire shift shaft. The sensor element can be attached in a variety of ways, regardless of where it is arranged, for example by gluing, screwing, crimping, or clamping, etc. Furthermore, according to the invention, it is advantageous if the sensor element is provided with a protective cover, for example, a protective cap for an axially terminal sensor element or a protective ring or the like for a sensor element arranged on the outside of the switching shaft. This protects the potentially somewhat sensitive sensor element, as it is covered. Various components based on different measurement principles can be used as sensors and sensing elements. A Hall sensor and a magnetic element are preferred. Such a measurement setup or displacement sensor allows for very precise and simple position determination. However, other sensor types, such as optical sensors, are also conceivable. Furthermore, the invention relates to a drive train, in particular of a motor vehicle, comprising a drive element and an output element as well as a coupling unit reversibly coupling these as described above. The invention is explained below with reference to exemplary embodiments and the drawings. The drawings are schematic representations and show: Fig. 1 a schematic representation of a coupling unit according to the invention, and Fig. 2 a perspective sectional view of the actuator of the coupling unit with mounted displacement sensor. Fig. 1 shows a schematic representation of a coupling unit 1 according to the invention, which can also be referred to as a coupling device, and which serves to couple a drive side 2, where a torque is applied or present, with an output side 3, to which the torque is to be transmitted and where it is further distributed. A drive element 4 is provided on the drive side 2, which has external teeth 5. The drive element 4 is, for example, a gear or an externally toothed shaft. On the output side 3, an output element 6 is provided, which has external teeth 7. This output element 6 can also be a gear, an externally toothed shaft, or the like. The external teeth 5 and 7 are linear radial teeth with the same pitch and radius. To couple the drive element 4 to the output element 6 in a rotationally fixed manner, a shift sleeve 8 is provided, which is axially displaceable. It has internal teeth 9, with which, in the decoupling position shown in Fig. 1, it fully engages the external teeth 5 of the drive element 4. This means that in the decoupling position, the shift sleeve 8 is coupled only to the drive element 4. Torque transmission to the output element 6 is not possible in this position.However, if torque transmission is required, the shift sleeve 8 must be axially displaced and slid over the output element 6, specifically its external teeth 7, so that the internal teeth 9 of the shift sleeve 8 are pushed into the external teeth 7 and mesh with them. Simultaneously, the engagement of the internal teeth 9 with the external teeth 5 remains, so that the drive element 4 and the output element 6 are rotationally fixedly coupled via the shift sleeve 8. To effect this movement of the switching sleeve 8, an actuator 10 is provided, which is a hydraulic actuator. It has a housing 11 in which a cylindrical insert 12, formed from a sheet metal part, is received. This insert forms a guide cylinder and contains a piston 13. The housing 11 is closed axially by a cover 14. Within the cylinder insert 12, the piston 13 is axially displaceable by means of a hydraulic fluid. For this purpose, a first pressure chamber 15 is provided, which is located between the piston 13 and the cover 14. On the opposite side, a second pressure chamber 16 is located between the piston 13 and the end wall of the insert 12. To seal the pressure chambers 15 and 16 on the piston side as well, two sealing elements 32 and 33 are provided on the piston 13. These elements provide a seal to the switching rod 17 on one side and to the cylinder insert 12 on the other.Depending on which pressure chamber 15, 16 the hydraulic fluid is injected into, the piston is moved in one direction or the other. Furthermore, a switching rod 17 is provided, which extends through the housing 11 and is guided to it in a sealed manner via corresponding sealing elements 18, 19. The switching rod 17 is axially movable, for which purpose it is coupled to the piston 13. For this purpose, two axial stops 20, 21 are provided on the switching rod 17, which are realized via two retaining rings 24, 25 received in respective grooves 22, 23. The piston 13 is slightly axially displaceable between these axial stops 20, 21. This axial displacement is possible against a spring element 26, which is designed as a wave spring, disc spring, or corresponding spring assembly and is received in an annular recess 27 of the piston. The spring element 26 is supported on one side by the piston 13 or the bottom of the recess 27 (see Fig. 1), and on the other side by the axial stop 20 or a support disc 28 supported by the snap ring 24. When a fluid is forced into the pressure chamber 15, the piston 13 is moved to the left until the spring element 26 abuts the support disc 28, unless this is already the case. The shift rod 17 is further connected to a driver 29, for example a shift fork, which in turn is connected to the shift sleeve 8 via a corresponding positive engagement. The shift sleeve 8, which rotates with the drive element 4, has, for example, a circumferential annular projection 30 that engages in a corresponding receiving groove 31 on the shift fork 29. Starting from the decoupling position shown in Fig. 1, in which the drive element 4 is not coupled to the output element 6, a torque-resistant coupling is to be achieved, the hydraulic fluid is forced into the pressure chamber 15. The piston 13 moves to the left. The switching rod 17 is carried along with it, after the spring element 26 is supported against the axial stop 20 and the piston 13 runs against the spring element 26. If the external teeth 5, 7 are in the gap position, the switching sleeve 8 can easily be pushed over the external teeth 7, or the internal teeth 9 can be engaged with the external teeth 7. The hydraulic actuation continues until the coupling position is reached, in which the piston 13, for example, runs into a left stop position at the bottom of the cylinder insert 12. If the external teeth 5 and 7 are not aligned, the internal teeth 9 of the shift sleeve inevitably run against the end face of the external teeth 7 of the output element 6, thus creating an axial stop. In this case, while the hydraulic fluid continues to be forced under pressure into the pressure chamber 15, the piston 13 is pushed axially further, although no further axial displacement of the shift rod 17 is possible due to the stop. However, the piston 13 can still move due to its axial play or axial mobility, and simultaneously the spring element 26 is compressed, generating a restoring force. The spring element 26 therefore acts as an energy storage device. This dampens the stop movement, as damping or compliance is integrated into the actuating system via the spring element 26, thus reducing the component load in this actuating system.At the same time, the spring element 26 acts as an energy storage device, as mentioned. As soon as the movement of the drive element 4 relative to the output element 6 results in a situation where the external teeth 5 and 7 are aligned again, and consequently the internal teeth 9 can be engaged with the external teeth 7, the spring element 26 suddenly relaxes and, in doing so, propels the shift rod and, via this shift sleeve 8, towards the output element 6, thus pushing the shift sleeve 8 over the output element 6 and engaging the teeth 7 and 9. This process occurs faster due to the use of the energy stored in the spring element 26 than it could be achieved solely through the hydraulic actuation of the piston 13 with a rigid connection between the piston 13 and the shift rod 17. In the coupled position, the piston 13 no longer needs to be pressurized, since the actuator is a bidirectional actuator and, due to the use of corresponding axial gears, the arrangement remains in the engaged coupled position. No additional energy is required to maintain this position. If the coupled position is to be released, i.e., the shift sleeve 8 is to be pushed back, the fluid is forced into the second pressure chamber 16, so that the piston 13, and with it the shift rod 17 along with the shift sleeve 8, is pushed back to the right and the gear engagement of the shift sleeve 8 with the output element 6 is released. To precisely detect the switching position of the sliding sleeve 8, i.e., to obtain exact knowledge of which defined state has been assumed, a displacement sensor 34 is provided on the actuator 10. This sensor serves to precisely determine the movement path and position of the switching rod 17, whereby the position of the switching rod 17 correlates with the position of the switching sleeve 8, so that it can be precisely determined whether the final decoupling position, the final coupling position, or an unstable intermediate position is present. Depending on this information, corresponding functions can then be controlled or suppressed on the vehicle side. The displacement sensor 34 includes a control and / or processing unit (not shown in detail) via which the corresponding position detection or evaluation takes place. The displacement sensor comprises a sensor 35, which is housed in a suitable sensor housing 36. The sensor housing 36 is L-shaped, as shown in Figures 1 and 2. It has a first leg 37, which forms a mounting section by which the sensor housing 36 is axially mounted onto the cover 14. The cover 14 is screwed to the housing 11 as part of it by means of several mounting screws 38. As the figures show, the sensor housing 36 is also axially screwed to the housing 11 by means of such a mounting screw 38. The sensor housing 36 further comprises a second leg 39, which projects axially and runs closely adjacent to and along the switching rod 17. This means that the actual sensor 35, which is, for example, a Hall sensor, is located very close to the switching rod 17. A sensor element 40 is arranged on the switching rod 17. In the example shown, this sensor element is a magnetic element axially attached to the end face of the switching rod 17 and extending the switching rod 17. It is covered by a protective cover 41, in this case a protective cap. The magnetic element 40 can be attached by gluing, screwing, or similar fastening methods, just as the sensor 35 can be glued or cast into the sensor housing 36, or similarly. Sensor 35 is capable of precisely determining the position of sensor element 40 relative to it, so that even the slightest movement of the switching rod 17 can be detected with high accuracy. The control and / or processing unit, as described (but not shown), communicates with sensor 35 and receives its signals, which are then evaluated for precise position determination. Based on this evaluated displacement, movement, or position data, it can then be precisely determined whether the switching rod 17, and consequently also the sliding sleeve 8, is in the decoupling position, the coupling position, or an intermediate position, for example, in an axial stop on the output element 6 as described above. This precise position knowledge, in turn, is indicative of the control of any position-related functions. The figures show an embodiment in which the sensor 35 is arranged outside the housing 11, as is the sensor element 40. Depending on the sensor size, it would also be conceivable to arrange the sensor 35, for example, in a radial receptacle formed on the inner circumference of the bore in the cover 14 through which the switching shaft runs, and to glue it in place there. The sensor 35 would then be positioned extremely close to the switching rod 17, on which the sensor element 40 would then naturally be arranged in a different position, namely along a longitudinal section of the switching rod 17. In this case, the sensor element could be a small magnetic element that is received or glued into a recess on the outside of the switching rod 17, or a ring or similar element that surrounds the switching rod and may be received in a groove. Reference symbol list 1 Coupling unit 2 Drive side 3 Output side 4 Drive element 5 External toothing 6 Output element 7 External toothing 8 Shift sleeve 9 Internal toothing 10 Actuator 11 Housing 12 Cylinder insert 13 Piston 14 Cover 15 Pressure chamber 16 Pressure chamber 17 Shift rod 18 Sealing element 19 Sealing element 20 Axial stop 21 Axial stop 22 Groove 23 Groove 24 Retaining ring 25 Retaining ring 26 Spring element 27 Recess 28 Support washer 29 Driver 30 Ring projection 31 Shift fork 32 Sealing element 33 Sealing element 34 Position sensor 35 Sensor 36 Sensor housing 37 First leg 38 Mounting screw 39 Second leg 40 Sensor element 41 Protective cover

Claims

Coupling unit for reversibly coupling a drive side (2) with an output side (3) of a drive train, comprising a linearly displaceable switching sleeve (8) which is mounted on a drive element (4) of the drive side (2) and can be moved from a decoupling position via an output element (6) of the output side (3) into a coupling position in which the switching sleeve connects the drive element (4) and the output element (6) in a rotationally fixed manner, wherein an actuator (10) is provided for moving the switching sleeve (8), which has a linearly displaceable piston (13) and a switching rod (17) coupled to the piston (13) and coupled to the switching sleeve (8), as well as a displacement sensor (34) comprising a sensor (35) via which a sensor element (40) arranged on the switching rod (17) and movable with it relative to the sensor (35) can be detected, wherein the sensor element (40) is arranged axially at the end of the switching rod (17),or that the sensor element (40) is mounted on the switching rod (17), wherein the sensor element (40) is covered with a protective cover (41). Coupling unit according to claim 1, characterized in that the sensor (35) is arranged on the outside of a housing (11) of the actuator (10) and the sensor element (40) is arranged on a section of the switching rod (17) projecting from the housing (11). Coupling unit according to claim 2, characterized in that the sensor (35) is arranged on a cover (14) which axially closes the housing (11). Coupling unit according to claim 3, characterized in that the sensor (35) is received in a sensor housing (36), wherein the sensor housing (36) is inserted into a receptacle formed on the cover (14) or is attached to the cover (14). Coupling unit according to claim 4, characterized in that the cover (14) has a bore through which the switching rod (17) extends, wherein the sensor (35) is arranged in the bore, or wherein the sensor housing (36) has a fastening section by which it is axially fixed to the cover (14), preferably by means of a fastening screw (38) by means of which the cover (14) is fastened to a housing component. Coupling unit according to claim 5, characterized in that the sensor housing (36) is L-shaped and has a first leg (37) forming the fastening section and a second leg (39) forming a holding section for the sensor (35), which extends along the switching rod (17). Coupling unit according to claim one of the preceding claims, characterized in that the sensor element (40) is a magnetic element and the sensor (35) is a Hall sensor. Powertrain, in particular of a motor vehicle, with a coupling unit (1) according to one of the preceding claims.

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