Patent Publication Number: US-2023145280-A1

Title: Shifting device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appin. No. PCT/DE2021/100335 filed Apr. 13, 2021, which claims priority to DE 10 2020 112 345.0, filed May 7, 2020, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a shifting device for a drivetrain of a motor vehicle. 
     BACKGROUND 
     DE 10 2014 217 066 A1 discloses a clutch for a switchable all-wheel drive, in which two aligned drive shafts are connected to one another by a clutch part that enables an interlocking connection between the two drive shafts. The clutch has a shifting element in the form of a shift fork, with which a clutch part that is displaceable in the axial direction is displaced in such a way that the interlocking connection between the two drive shafts is established. 
     A coupling assembly for a drivetrain of a motor vehicle is known from WO 2011/098 595 A1, which comprises at least one clutch that is arranged on a rotating shaft in order to selectively couple the rotating shaft to a drive element of the drivetrain. The coupling assembly further comprises at least one actuating device for actuating the clutch. The actuating device is designed to selectively bring an engagement section into engagement with a threaded section rotating with the shaft in order to bring about a relative movement of the engagement section and the threaded section along the axis of the rotating shaft and thereby to actuate the clutch in the axial direction. 
     SUMMARY 
     It is an object of the present application to provide an improved shifting device for a drivetrain of a motor vehicle. 
     A shifting device is provided for a drivetrain of a motor vehicle, comprising a housing, in which a first and a second drive shaft are rotatably mounted, wherein the first and second drive shaft are arranged coaxially with respect to one another so that they have a common axis of rotation, and a shiftable clutch device, which is arranged between the first and the second drive shaft, wherein the clutch device has an open shift position, in which the first drive shaft is freely rotatable relative to the second drive shaft, and the clutch device has a closed shift position in which the first drive shaft is connected for conjoint rotation with the second drive shaft via the clutch device, wherein a control element which is displaceable in the direction of the axis of rotation of the drive shafts is provided and, depending on its displacement position, shifts the clutch device to the open or closed shift position, wherein the control element is formed by a sliding sleeve, which surrounds at least one of the two drive shafts, wherein a gear element is provided on an outer circumference of the sliding sleeve. 
     A particularly simple and cost-effective control element can be realized by the sliding sleeve, which enables particularly advantageous actuating accuracy due to its stability. The sleeve shape preferably extends from the gear element all the way to the section of the actuating element that introduces the actuating forces into the clutch device. The gear element arranged on the outer circumference of the sliding sleeve can be provided, for example, only on a partial section of the sliding sleeve or alternatively also over the entire circumference of the sliding sleeve. 
     It is also advantageous if at least one bearing element is provided, which enables a displacement movement of the control element in the direction of the axis of rotation of the drive shafts and prevents the control element from rotating about the axis of rotation. The bearing element can ensure that the control element can reliably switch the clutch device both into the open and into the closed shift position. Furthermore, this mounting reliably prevents the control element from rotating with the rotational movement of the drive shaft. Multiple bearing elements are preferably provided, for example precisely two bearing elements, which are arranged in such a way that they support the control element at opposite points. 
     It is further proposed that the bearing element is formed by a pin which is immovably mounted in the housing and engages in a receptacle of the control element. By configuring the bearing element as a pin, it can be manufactured particularly cost-effectively. In order to achieve the desired mounting, the bearing element is preferably oriented in the direction of the axis of rotation. Further bearing elements for preventing unwanted movements can thus advantageously be omitted. 
     It is further proposed that the receptacle for the control element is open radially outward. As a result, a simpler and more cost-effective structure of the control element can be realized. Furthermore, incorporation of the control element into the bearing element during assembly is made easier. The receptacle is preferably designed in such a way that the bearing element is surrounded by a fork-like extension of the control element. Due to the fork-like extensions, the control element bears against the bearing element in the radial direction so that it can be reliably prevented from turning. 
     It is also proposed that the gear element of the control element is formed by an outer toothing. An easily accessible gear element can be realized by the outer toothing. The outer toothing is preferably configured to be in engagement with a pinion shaft. The outer toothing is preferably designed like the outer toothing in the manner of a toothed rack. A rotation of the pinion shaft then causes the outer toothing to be advanced so that the control element is also moved in the direction of the axis of rotation. 
     It is further proposed that the clutch device is formed by a dog clutch, with each drive shaft being connected for conjoint rotation with a dog clutch element. By displacing at least one of the dog clutch elements in the direction of the axis of rotation, the dog clutch makes it possible to establish a rotationally fixed connection via an interlocking connection. 
     According to an advantageous embodiment, two undercuts are provided on the base between two dogs of the dog clutch, the tangential extension of said undercuts corresponding to at least 10% of the tangential spacing between the adjacent dogs. For example, the tangential extension is at least 20% of the tangential spacing, further for example 30% of the tangential spacing. With a correspondingly large radius of the undercuts, the dogs can be produced by milling, so that simple and cost-effective production is made possible. The radius of the undercuts preferably corresponds to the radius of the milling machine with which the dogs are manufactured. The undercuts preferably have a constant radius and extend in the radial direction, i.e., are oriented perpendicular to the axis of rotation. 
     It is further proposed that the housing be made in two parts, with a first housing part having a cylindrical outer contour and a second housing part having a mounting flange with at least one fastening means, the outer radius of the mounting flange being larger than the outer radius of the cylindrical outer contour of the first housing part. This structure of the housing enables the shifting device to be installed in a space-saving manner. In the assembled state, the first housing part with the cylindrical outer contour can be inserted into a transmission housing, which is not part of this application. The fastening means on the mounting flange, which is associated with the second housing part, also enables reliable and stable fastening to the transmission housing. Multiple fastening means are preferably provided, which are arranged uniformly on the circumference of the fastening flange. 
     It is further proposed that the control element is mounted on a section of the drive shaft so that it can be displaced in the direction of the axis of rotation, with the second housing part having an access opening via which the control element can be actuated. By assigning the access opening to the second housing part, an advantageous functional separation of the housing can be realized. The first housing part is designed to save space so that it can protrude into the transmission housing in the assembled state. The second housing part, on the other hand, assumes the fastening function on the transmission housing and creates the conditions for being able to actuate the actuating element. Preferably, the access opening is arranged in the half of the second housing part that faces the first housing part. 
     It is also proposed that the clutch device is arranged entirely in the first housing part. This results in an even more advantageous separation of functions, because it has been shown that the clutch device can be accommodated in the first housing part in a space-saving manner. In this case, the control element extends from the second into the first housing part, so that the clutch device can still be controlled from the second housing part. 
    
    
     
       BRIEF SUMMARY OF THE DRAWINGS 
       The present disclosure is explained below by means of preferred embodiments with reference to the attached figures. In the figures: 
         FIG.  1    shows a sectional view of a shifting device; 
         FIG.  2    shows a perspective view of a shifting device; 
         FIG.  3    shows a side view of a shifting device; 
         FIG.  4    shows a front view of a second housing part of a shifting device with a control element and a bearing element; 
         FIG.  5    shows a perspective view dog clutch element; 
         FIG.  6    is a side view of a dog clutch element; 
         FIG.  7    shows a detailed view of a dog clutch element. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a shifting device  1  with a first drive shaft  3  and a second drive shaft  4 , which can be connected for conjoint rotation with one another via a clutch device  6 . 
     The second drive shaft  4  comprises two partial shafts which are connected to one another for conjoint rotation via a toothing  9 . The second drive shaft  4  is mounted at one end in a receptacle  25  of the first drive shaft  3  and opposite a housing  2  via a ball bearing  23 . The first drive shaft  3  is mounted within the housing  2  by a ball bearing  24  and by an extension of the second drive shaft  4 , which projects into the receptacle  25  of the first drive shaft  3 . The first and second drive shafts  3  and  4  are oriented coaxially with one another and therefore rotate about a common axis of rotation  5 . 
     One end of each of the first and second drive shafts  3  and  4  protrudes from the housing  2 . In the assembled state, the first drive shaft  3  can then be connected for conjoint rotation with a differential transmission, for example, and the second drive shaft  4  to a drive wheel, for example, or vice versa. 
     The clutch device  6  is provided at the mutually facing ends of the first and second drive shafts  3 ,  4  and comprises a first dog clutch element  12  associated with the first drive shaft  3  and a second dog clutch element  13  associated with the second drive shaft  4 . The clutch device  6  can be shifted into an open shift position in which the first drive shaft  3  and the second drive shaft  4  are not connected for conjoint rotation with one another. Furthermore, the clutch device  6  can be switched into a closed shift position in which the first drive shaft  3  is connected for conjoint rotation with the second drive shaft  4 . The clutch device  6  is controlled by means of a control element  7 , which is mounted on the second drive shaft  4  in an axially displaceable manner, i.e., in the direction of the axis of rotation  5 . In this embodiment, the control element  7  is designed as a sliding sleeve, the sleeve shape extending from a gear element  8  to the point at which the control forces are introduced into the clutch device  6 . 
     The gear element  8  has a toothing in the manner of a toothed rack, so that the gear element  8  can be displaced together with the control element  7  in the direction of the axis of rotation  5 . The gear element  8  can be driven, for example, via a pinion shaft, which is not shown in  FIG.  1   , so that an advance of the control element  7  in the direction of the axis of rotation  5  results from a rotational movement of the pinion shaft. 
     The movement of the control element  7  is transmitted to the second dog clutch element  13  via an axial ball bearing  28 . The axial ball bearing  28  ensures that at most a minimal torque is transmitted to the control element  7  as a result of any rotational movement of the second dog clutch element  13 . The clutch device  6  can thus be switched into a closed or open shift position by means of the control device  7 . By moving the control element  7  in the direction of the axis of rotation  5  towards the first dog clutch element  12 , the second dog clutch element  13  in a closed shift position can be interlockingly connected to the first dog clutch element  12 . By moving the control element  7  in the opposite direction, the clutch device  6  can be shifted into an open shift position in which the dog clutch elements  12  and  13  are not engaged with one another. The control element  7  also has an extension  26  which extends outwards in the radial direction and which comes into contact with the housing  2  in the open shift position so that an end position of the control element  7  is fixed. 
       FIG.  2    shows a perspective view of the shifting device  1 , in which a division of the housing  2  can be seen. The housing  2  has a mounting flange  20  with fastening means  21 , via which the shifting device  1  can be fastened to a transmission housing, which is not part of this application. A plurality of fastening means  21  are preferably provided so that a stable and reliable connection to the transmission housing is possible. The fastening means  21  are preferably formed by bores in the mounting flange  20  so as to make simple fastening possible, for example using bolts or screws. 
     The housing  2  is divided into a first housing part  17  and a second housing part  19 . The first housing part  17  has a cylindrical outer contour  18  so that the first housing part  17  can be inserted into a likewise cylindrical receptacle of a transmission housing and can be stored there. In the mounted state, the first housing part  17  protrudes so far into the transmission housing that the mounting flange  20  comes to rest on the transmission housing. The second housing part  19  then includes the part of the housing  2  with the mounting flange  20 , which protrudes from the transmission housing. 
       FIG.  3    shows a side view of the shifting device  1 , from which it can be seen that the radial extension of the cylindrical outer contour  18  is less than that of the second housing part  19  with the mounting flange  20 . As a result, the shifting device  1  can be mounted in a transmission housing in a space-saving manner. This space-saving design also results from the advantageous division that the clutch device  6  is arranged in the first housing part  17  and the section of the control element  7  with the gear element  8  in the second housing part  19 ; see also  FIG.  1   . 
     Access is provided via an access opening  22  to drive the gear element  8  of the control element  7 ; this takes place, for example, via a pinion shaft (not shown), which is operatively connected to the transmission element  8  formed by an outer toothing. In the installed state, the pinion shaft is oriented perpendicular to the station axis  5 . 
       FIG.  4    shows a front view of the second housing part  19 . It can be seen that the mounting flange  20  has a planar contact surface that bears against a transmission housing in the mounted state. Furthermore,  FIG.  4    shows the mounting of the control element  7  in the second housing part  19 . Two bearing elements  10  which are oriented parallel to the axis of rotation  5  are provided for the displaceable mounting of the control element  7 . The bearing elements  10  are formed by pins, which are immovably mounted in the housing  2 . The control element  7  has two sections, each of which forms a receptacle  11  for the bearing element  10 . The bearing element  10  is surrounded by the receptacle  11  in the manner of a fork so that the control element  7  is secured in the radial direction and cannot twist. This is advantageous because, despite the axial ball bearing  25 , a torque about the axis of rotation  5  can act on the control element  7  when the second dog clutch element  13  rotates. However, a movement of the control element  7  relative to the bearing element  8  in the direction of the axis of rotation  5  remains possible. The receptacles  11  are each open radially outwards. 
       FIG.  5    shows a perspective view of the second dog clutch element  13 , in which dogs  15  and a base  14  arranged therebetween them alternate and an undercut  16  is provided in each case at the transition between the base  14  and the dog  15 . Furthermore, the second dog clutch element  13  comprises an internal toothing  27  via which the second dog clutch element  13  is connected for conjoint rotation with the second drive shaft  4 . 
       FIG.  6    shows a side view of the second dog clutch element  13 , showing the design of the undercuts  16  more clearly. 
     A detailed view of the undercuts  16  can be seen in  FIG.  7   . In this case, b corresponds to the tangential spacing between two adjacent dogs  15 . The tangential extension of the undercut  16  is marked with a and corresponds to at least 10% of the tangential spacing between the dogs  15 . The dogs  15  or the base  14  can thus be produced in a simple manner using a milling process. Since a milling machine with a constant radius is advantageously used for production, the tangential extension a of the undercut  16  in the radial direction also remains constant. Since the tangential extension b of the base  14  decreases radially inwards, i.e., in the direction of the axis of rotation  5  (see also  FIG.  5   ), the tangential extension c of the planar surface of the base  14  also decreases radially inwards. 
     The design of the second dog clutch element  13 , in particular the dogs  15 , of the base  14  and the undercuts  16  and the internal toothing  27  can naturally also be transferred to the first dog clutch element  12  in a corresponding manner. 
     LIST OF REFERENCE SIGNS 
     
         
           1  Shifting device 
           2  Housing 
           3  First drive shaft 
           4  Second drive shaft 
           5  Axis of rotation 
           6  Clutch device 
           7  Control element 
           8  Gear element 
           9  Toothing 
           10  Bearing element 
           11  Receptacle (of the control element) 
           12  First dog clutch element 
           13  Second dog clutch element 
           14  Base (between dogs) 
           15  Dogs 
           16  Undercut 
           17  First housing part 
           18  Cylindrical outer contour 
           19  Second housing part 
           20  Mounting flange 
           21  Fastening means 
           22  Access opening 
           23  Ball bearing 
           24  Ball bearing 
           25  Receptacle 
           26  Extension 
           27  Inner toothing 
           28  Axial ball bearing 
         a Tangential extension (undercuts) 
         b Tangential extension (base) 
         c Tangential extension (planar surface of the base)