Abstract:
In an electromagnetically actuated dual clutch-brake combination ( 8 ), a drive input shaft ( 2 ) can be optionally engaged in drive connection with a first drive output shaft ( 4 ) or with a second drive output shaft ( 6 ). The second drive output shaft ( 6 ) is associated with an electromagnetic brake ( 52 ), which is provided in order to immobilize the second drive output shaft ( 6 ), whereas the first drive output shaft ( 4 ) can still be connected to the drive input shaft ( 2 ) by an electromagnetic clutch ( 28, 32 ). The electromagnetic dual clutch-brake combination is suitable for controlling a variable longitudinal differential lock and a shiftable range gear system of an all-wheel distributor gearbox, with only a single electric motor.

Description:
This application claims priority from German Application Serial No. 103 02 506.5 filed Jan. 23, 2003. 
   FIELD OF THE INVENTION 
   The invention concerns an electromagnetically actuated dual clutch-brake combination. 
   BACKGROUND OF THE INVENTION 
   Such an electromagnetic dual clutch-brake combination is used for the optional drive connection of a drive input shaft to a first or to a second drive output shaft. Depending on the shift condition of the dual clutch-brake combination, a single electric motor coupled to the drive input shaft can drive the first drive output shaft or the second one. 
   A dual clutch-brake combination of the type described is disclosed in DE 100 58 199 A1. 
   Such a dual clutch-brake combination can be used in the drive train of an all-wheel vehicle with range shifting between a fast and a slow operating range and a variable longitudinal differential lock. In the vehicle&#39;s drive train a shiftable, two-stage range gear system is arranged after the main gearbox, such that the first stage corresponds to the slow drive range and the second stage to the fast range. The range gear system comprises a shift element in the form of a claw or disk clutch or a synchromesh, which can, be actuated by the first drive output shaft of the dual clutch-brake combination via an actuation mechanism. When the second drive output shaft of the dual clutch-brake combination is rotating, then depending on the rotation direction, a disk clutch is closed further or opened further, which depending on its degree of closure transfers a certain torque between the two drive axles of the vehicle. If the disk clutch is fully closed, the front and rear axle differentials are driven at the same speed. 
   The dual clutch-brake combination according to DE 100 58 199 A1 thus enables a single electric motor optionally to shift the two-stage range gear system or to actuate the variable longitudinal differential lock. The drive input shaft of this dual clutch-brake combination can be braked to rest by an electromagnetic brake. A static torque exerted on the drive input shaft by the electric motor can even be maintained when the electric motor is not under load in that the brake is applied before the electric motor is turned off. The electric motor is unloaded and the overall consumption of electrical energy is reduced. A frequently encountered driving situation on difficult ground is to start with a closed longitudinal differential lock in the slow driving range. When the vehicle has reached a certain speed, a shift to the fast driving range is necessary. If a dual clutch-brake combination such as that described in DE 100 58 199 A1 is used, the driving range can only be shifted if the variable longitudinal differential lock is opened briefly. 
   Accordingly, the purpose of the invention is to indicate a dual clutch-brake combination with which a shift of the range gear system can take place, while the torque transferred by the variable longitudinal differential lock between the drive axles remains unchanged even during the range shift. 
   This objective is achieved by an electromagnetically actuated dual clutch-brake combination. 
   SUMMARY OF THE INVENTION 
   The second drive output shaft of the dual clutch-brake combination, which is provided for the actuation of the clutch of the longitudinal differential lock, is connected rotationally fast to a brake armature which brakes the second drive output shaft when the brake magnet coil is energized with electric current. When the clutch armature connected rotationally fast to the drive input shaft is in its first shift position, in which it is connected to the first drive output shaft in positive torque transmission, an electric motor connected to the drive input shaft can be used to shift the range gear system from the slow to the fast driving range or vice-versa, so long as the second drive output shaft is firmly braked. Thus even during the shifting of the range gear system optimal traction is ensured by the blocked longitudinal distributor. 
   In an advantageous embodiment of the invention the clutch armature has at one end a friction surface which in the first shift position of the clutch armature is pressed against an opposite friction surface of a first flange fixed on the first shaft. 
   In a further embodiment of the invention the clutch armature has a hollow cylindrical area with internal gear teeth which, in the second shift position, engage with the drive gear teeth of a second flange arranged on the second drive output shaft. In this second shift position the clutch armature is held by passive restoring means such as an elastic spring or a permanent magnet. The passive restoring means do not need to exert any large axial force on the clutch armature. Yet, the frictional torque transmission by means of the drive gear teeth enables high torques to be transferred. The axial force exerted on the clutch armature by the magnetic coil of the clutch in the first shift position is large enough for the required torque to be transferred even by the friction surfaces. 
   An embodiment of the invention, advantageous from the design standpoint is characterized in that the second flange is axially stepped, with the drive gear teeth formed on the radially outer step and with an annular disk spring attached to the radially inner step, which connects the brake armature rotationally fast and axially movably to the second flange. 
   The second flange can be fixed as a separate component on the second drive output shaft or, in an advantageous design, it can be made as one piece with the second flange. 
   A favourable arrangement of the functional elements is achieved when the second drive output shaft and the second flange have a through-going hollow space in the area of their rotation axis, through which the first drive output shaft passes. 
   The dual clutch-brake combination according to the invention is particularly appropriate for the control of an all-wheel distributor gearbox  70  for a vehicle  72  with several driveable axles  74 ,  76 , with a variable longitudinal differential lock  78  and an at least two-stage shiftable range gear system  80  arranged after a main gearbox T of the vehicle  72 . The longitudinal differential lock  78  of the all-wheel distributor gearbox  70  comprises a clutch  77  which, depending on the degree of its closure, transfers a torque between the two driveable axles  74 ,  76 , of the vehicle  72 . The longitudinal differential lock  78  of the all-wheel distributor gearbox  70  comprises a clutch  77  which, depending on the degree of its closure, transfers a torque between the two driveable axles  74 ,  76 , of the vehicle  72 . The range gear system  80  comprises a shift element  82  such that the said shift element  82  of the range gear system  80  can be actuated directly or via an actuation mechanism by the first drive output shaft  4  of the dual clutch-brake combination  8 . The degree of closure of the clutch  82  of the longitudinal differential lock  78  can be varied by a rotation of the second drive output shaft  6 . 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
       FIG. 1  is a section through a dual clutch-brake combination in a first shift position; 
       FIG. 2  is a section through a dual clutch-brake combination in a second shift position, and 
       FIG. 3  is a diagrammatic representation of the vehicle drive train. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a drive input shaft  2  of a dual clutch-brake combination  8 , a first drive output shaft  4 , and a second drive output shaft  6 . The input shaft  2  is engaged with the drive output shaft  10  of an electric motor (not shown), which is held in rotationally fixed connection by a keyway joint  12 . The drive shaft  2  and the two drive output shafts  4 ,  6  are axially fixed by bearings  14 ,  16 , but mounted so that they can rotate in a two-part housing  18 ,  20  of the dual clutch-brake combination  8 . On the first drive output shaft  4  is arranged a flange  24 , which has at its outer circumference a shoulder  22  whose end face forms a friction surface  24 , which is provided in order to cooperate with an opposing friction surface  26  of the clutch armature  28 . The clutch armature  28  is connected to a flange  30  of the drive input shaft  2  by an annular disk spring (not shown), rotationally fixed but able to move axially. In the shift position (shown in  FIG. 1 ), a magnetic coil  32  of the clutch is energized with current. Accordingly, the armature moves so that the magnetic circuit establishes contact between the friction surfaces  24 ,  26  of the flange  21  and the clutch armature  28 . Thus, when the magnetic coil of the clutch is switched on, the clutch armature  28  is pressed against the flange  21  so that by virtue of the friction surfaces  24 ,  26  a torque is exerted by the clutch armature  28  connected to the drive input shaft  2  on the flange  21  connected to the first drive output shaft  4 . On its side facing towards the magnetic coil of the clutch, the clutch armature  28  has a hollow cylindrical section which encloses the outer circumference of the magnetic coil  32  of the clutch with a small radial clearance. When the magnetic coil  32  of the clutch is switched off, the armature is moved by an annular disk spring  34  (shown in  FIG. 2 ) toward the right as seen in  FIG. 2 , into its second shift position, and held there. In this shift position, the friction surfaces  24  and  26  of the flange  20  and the clutch armature  28  are axially separated, so no torque is transferred between the drive input shaft and the first drive output shaft. However, in this second shift position, inner gear teeth  36  present in a hollow cylindrical area  38  of the clutch armature  28  are engaged with drive gear teeth  40  formed on the outer circumference of a flange  42  connected to the second drive output shaft  6 . The flange  42  connected to the second drive output shaft  6  is axially stepped, such that the drive gear teeth  40  are formed on a radially outer step  44  and an annular disk spring  48  is attached to a radially inner step  46 , which connects a brake armature  50  of an electromagnetic brake  52  rotationally fast, but axially movably to the second drive output shaft  6 . The brake armature  50  is attracted by a magnet element  54  of the electromagnetic brake  52  when a brake magnet coil  56  is energized with current. The electromagnetic brake  52  can be actuated independently of the electromagnetic clutch, so that all four shift conditions can be implemented. In particular, it is possible, first, when the clutch magnet coil  32  is switched off, to impose a given torque on the second drive output shaft  6  by means of the input electric motor, which determines the torque transmission in the variable longitudinal differential lock of a distributor gearbox of a vehicle. If the electromagnetic brake  52  is now switched on, this torque is still applied statically to the second drive output shaft  6  even when the clutch magnet coil  32  is energized with current and the connection between the clutch armature  28  and the second output shaft  6  is disengaged. The electric motor can then be used to activate the first drive output shaft  4 , by which the range shift between a slow-drive range and a fast-drive range is brought about. 
     FIG. 1  shows a drive input shaft  2  of a dual clutch-brake combination  8 , a first drive output shaft  4 , and a second drive output shaft  6 . The input shaft  2  is engaged with the drive output shaft  10  of an electric motor  66 , which is held in rotationally fixed connection by a keyway joint  12 . The drive shaft  2  and the two drive output shafts  4 ,  6  are axially fixed by bearings  14 ,  16 , but mounted so that they can rotate in a two-part housing  18 ,  20  of the dual clutch-brake combination  8 . On the first drive output shaft  4  is arranged a flange  21 , which has at its outer circumference a shoulder  22  whose end face forms a friction surface  24 , which is provided in order to cooperate with an opposing friction surface  26  of the clutch armature  28 . The clutch armature  28  is connected to a flange  30  of the drive input shaft  2  by an annular disk spring (not shown), rotationally fixed but able to move axially. In the shift position (shown in  FIG. 1 ), a magnetic coil  32  of the clutch is energized with current. Accordingly, the armature moves so that the magnetic circuit establishes contact between the friction surfaces  24 ,  26  of the flange  21  and the clutch armature  28 . Thus, when the magnetic coil of the clutch is switched on, the clutch armature  28  is pressed against the flange  21  so that by virtue of the friction surfaces  24 ,  26  a torque is exerted by the clutch armature  28  connected to the drive input shaft  2  on the flange  21  connected to the first drive output shaft  4 . On its side facing towards the magnetic coil of the clutch, the clutch armature  28  has a hollow cylindrical section which encloses the outer circumference of the magnetic coil  32  of the clutch with a small radial clearance. When the magnetic coil  32  of the clutch is switched off, the armature is moved by an annular disk spring  34  (shown in  FIG. 2 ) toward the right as seen in  FIG. 2 , into its second shift position, and held there. In this shift position, the friction surfaces  24  and  26  of the flange  20  and the clutch armature  28  are axially separated, so no torque is transferred between the drive input shaft and the first drive output shaft. However, in this second shift position, inner gear teeth  36  present in a hollow cylindrical area  38  of the clutch armature  28  are engaged with drive gear teeth  40  formed on the outer circumference of a flange  42  connected to the second drive output shaft  6 . The flange  42  connected to the second drive output shaft  6  is axially stepped, such that the drive gear teeth  40  are formed on a radially outer step  44  and an annular disk spring  48  is attached to a radially inner step  46 , which connects a brake armature  50  of an electromagnetic brake  52  rotationally fast, but axially movably to the second drive output shaft  6 . The brake armature  50  is attracted by a magnet element  54  of the electromagnetic brake  52  when a brake magnet coil  56  is energized with current. The electromagnetic brake  52  can be actuated independently of the electromagnetic clutch, so that all four shift conditions can be implemented. In particular, it is possible, first, when the clutch magnet coil  32  is switched off, to impose a given torque on the second drive output shaft  6  by means of the input electric motor  66 , which determines the torque transmission in the variable longitudinal differential lock  78  of a distributor gearbox  70  of a vehicle  72 . If the electromagnetic brake  52  is now switched on, this torque is still applied statically to the second drive output shaft  6  even when the clutch magnet coil  32  is energized with current and the connection between the clutch armature  28  and the second output shaft  6  is disengaged. The electric motor  66  can then be used to activate the first drive output shaft  4 , by which the range shift between a slow-drive range and a fast-drive range is brought about. 
   REFERENCE NUMERALS 
   
       
         2  drive input shaft 
         4  first drive output shaft 
         6  second drive output shaft 
         8  dual clutch-brake combination 
         10  engine shaft 
         12  keyway connection 
         14  bearing 
         16  bearing 
         18  housing component 
         20  housing component 
         21  flange 
         22  collar 
         24  friction surface 
         26  friction surface 
         28  clutch armature 
         30  flange 
         32  clutch magnet coil 
         34  annular disk spring 
         36  inner gear teeth 
         38  hollow cylindrical area 
         40  drive gear teeth 
         42  flange 
         44  area 
         46  area 
         48  annular disk spring 
         50  brake armature 
         52  electromagnetic brake 
         54  magnet element 
         56  magnet coil 
         58  area 
         60  bearing 
         62  bearing 
         64  bearing