Abstract:
An axial setting device comprising two plates ( 24, 29 ) which are relatively rotatable and coaxially supported relative to one another and between which balls are guided in pairs of ball grooves ( 34, 39 ) in the plates ( 24, 29 ), with the depth of said pairs of ball grooves ( 34, 39 ) being circumferentially variable; of the plates ( 24, 29 ), one is axially supported and one is axially displaceable against the elastic returning forces of spring means; at least one of the plates ( 24, 29 ) is drivable via a driveline by a driving motor ( 11 ). Within the driveline, between the driving motor ( 11 ) and the drivable plates ( 24, 29 ), there is inserted a switching coupling ( 83 ).

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to an axial setting device comprising two plates which are relatively rotatable and coaxially supported relative to one another and between which balls are guided in pairs of ball grooves in the plates, with the depth of the pairs of ball grooves being circumferentially variable. One of the plates is axially supported and one is axially displaceable against elastic returning forces of a spring mechanism. At least one of the plates is drivable via a driveline by a driving motor.  
         BACKGROUND OF THE INVENTION  
         [0002]    One rotatingly driven plate can, at the same time, constitute the axially displaceable one, but this would be an exception. Normally, the supported plate is rotatingly driven and the axially displaceable plate which, in turn, is supported via the balls on the supported plate is held in a rotationally fast way.  
           [0003]    For actuating the axial setting device, the driving motor is driven in a first direction of rotation. The at least one plate coupled to the driving motor via reduction stages of the driveline is rotated, and the displaceable plate, which, in turn, axially supports itself on the axially supported plate is axially displaced against elastic returning forces of the spring mechanism.  
           [0004]    The balls which, in pairs of ball grooves, rest against end stops and which, at the same time, are positioned there in the deepest groove portions are caused, by the relative rotation of the plates relative to one another, to move towards flatter groove portions, as a result of which the plates push each other away from one another.  
           [0005]    If the driving motor is driven in the opposite direction or deenergised, the elastic returning force of the spring mechanism acting on the displaceable plate causes the latter to be pushed back and the at least one rotatingly drivable plate is rotated backwards, either actively by the driving motor or due to the effect of the spring mechanism by way of the balls in the ball grooves until the balls in their pairs of ball grooves simultaneously abut the end stops. As a result of the balls abutting the ends of the ball grooves, the rotating masses of this system, i.e. the rotatable one of the plates, the gears of the driveline and the motor shaft of the driving motor with the rotor mass are stopped abruptly.  
           [0006]    The elastic deformation of the motor shaft caused by stopping the rotating masses so abruptly can lead to tooth fracture at the pinion or at the gear set because the force impact points in the toothings move outwards due to the bending of the motor shaft, as a result of which the pinion or the gear set are subjected to loads which can exceed the design loads.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore an object of the present invention to provide a design which is capable of accommodating in a damage-free way the momentum generated as a result of the rotating masses being braked when the balls abut the ends of the ball grooves. The objective is achieved in that the present invention provides a switching coupling inserted between the driving motor and the drivable one of the plates.  
           [0008]    The switching coupling of the present invention ensures that at least the motor shaft with the rotor mass, and possibly also further masses of the driveline, are disconnected from the abutting drivable plate in the sense that the de-energised motor or, optionally, the electrically braked motor can continue to rotate without there being mechanical overloads. In this context, it should be taken into account that, as a rule, the object is to achieve the quickest possible return movement, irrespective of whether such a return movement is effected actively by the driving motor or, if the driving motor is de-energized, merely by the returning force of the spring mechanism and by the ramp effect of the ball grooves.  
           [0009]    According to a first embodiment, the switching coupling is effectively incorporated between a motor shaft of the driving motor and a coupling shaft. According to a second embodiment, the switching coupling is effectively inserted between two gearwheels of an intermediate shaft of the driveline, of which one is connected to the intermediate shaft in a rotationally fast way, with the other one being rotatably supported on the intermediate shaft. According to a third embodiment, the switching coupling is inserted between the drivable one of the plates and a gearwheel or tooth segment serving for driving the drivable one of the plates. The reduction in the masses to be braked and thus in the momentum when the balls abut the groove ends becomes more effective from embodiment to embodiment.  
           [0010]    According to a first method according to the present invention for returning purposes, the driving motor, from the start, is disconnected from the device by the switching coupling in accordance with the invention. The rotatable plate is turned back from the axially displaceable plate by the above-mentioned functions of the spring mechanism and ball grooves. When the rotatable plate abuts, the disconnected motor shaft with the rotor mass can continue to rotate freely, and the way in which the motor shaft is eventually braked is not significant. The motor shaft is kept completely free from the delaying momentum of the rotatingly drivable plate.  
           [0011]    According to a second method, the device is actively returned by the driving motor, in which case the axially displaceable plate only axially follows the rotatingly driven plate. When the stops are reached and when the rotatingly drivable plate is stopped, the motor shaft with the rotor mass and, optionally, further parts of rotational masses of the driveline can simultaneously be disconnected by the inventive switching coupling.  
           [0012]    Other advantages and features of the invention will also become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0014]    In the drawings:  
         [0015]    [0015]FIG. 1 shows an inventive device in a first embodiment with a switching coupling arranged on the shaft of the driving motor.  
         [0016]    [0016]FIG. 2 shows the driving motor with the switching coupling according to FIG. 1 in the form of a detail.  
         [0017]    [0017]FIG. 3 shows the inventive device in a second embodiment with a switching coupling on an intermediate shaft.  
         [0018]    [0018]FIG. 4 shows the switching coupling on the intermediate shaft in the form of a detail.  
         [0019]    [0019]FIG. 5 shows an inventive device in a third embodiment with a switching coupling arranged in the drive of the first ramp plate.  
         [0020]    [0020]FIG. 6 shows the drive of the first ramp plate in the form of an enlarged detail. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    [0021]FIGS. 1 and 2 will be described jointly below. They show a first axial setting device in accordance with an embodiment of the invention in a mounted condition. A driving motor  11  is shown as provided with a motor shaft  12  and with a motor housing  13  in which the motor shaft  12  is supported twice. A coupling housing  81  in which there is supported a coupling shaft  82  is fixed to the motor housing  13 . A first plate  84  of an electromagnetic switching coupling  83  is secured to the motor shaft  12  by way of a feather key  85 . A second plate  86  of the electromagnetic switching coupling  83  is secured to the coupling shaft  82  by way of a feather key  87 . On the coupling shaft  87  there is secured by way of a pin  16  a shaft journal  14  which forms a driving pinion  15 . The coupling housing  81  is inserted into a centering bore  51  in a housing wall  52 . The free end of the shaft journal  14  is supported by a needle bearing  21  in a housing wall  54 . A bearing journal  18  is inserted into a further bore  53  in the housing wall  52 . On the bearing journal  18 , there is rotatably supported a sleeve pinion  19  by way of two needle bearings  41 ,  42 . A larger gearwheel  20  which, by way of its gear rim, engages the pinion  15  is pressed on to the sleeve pinion  19 . The sleeve pinion  19 , in turn, engages a tooth segment  22  which is firmly connected to a first plate  24  of the setting device. By way of a needle bearing  23 , the plate  24  is rotatably supported on a projection of a cover  25  on which it is axially supported by way of an axial bearing  26 , a plate  27  and a securing ring  28 . The plate  24  cooperates with a further plate  29  which is slidingly supported on a projection of the plate  24  and which is supported on the cover  25  by way of an axial bearing  30  and a plate  31  via pressure springs  33 . The plate  31  acts on pressure pins  32  inserted into the pressure springs  33 . The pressure pins  32  form the direct setting members of the device. The surfaces of the plates  24 ,  29 , which face one another, are provided with pairs of grooves  34 ,  39  whose depth varies across the circumference and in which there run balls  35  held in a ball cage  36 . The plate  29  comprises a radial projection  37  with a guiding claw  38 . The guiding claw  38  slides in a longitudinally displaceable way on a holding pin  40  which is firmly inserted into a bore  55  in a housing wall  56  and which, in this way, holds the axially displaceable plate  29  in a rotationally fast way.  
         [0022]    [0022]FIGS. 3 and 4 will be described jointly below. They show a second embodiment of an axial setting device in accordance with the invention in a mounted condition. A driving motor  11  is shown to be provided with a motor shaft  12  and with a motor housing  13  in which the motor shaft  12  is supported twice. The motor housing  13  is inserted into a centering bore  51  in a housing wall  52 . On the motor shaft  12 , there is secured by way of a pin  16 , a shaft journal  14  which forms a driving pinion  15 . A bearing journal  18  is inserted into a further bore  53  in the housing wall  52 . A sleeve pinion  19  is rotatably supported on the bearing journal  18  by way of two needle bearings  41 ,  42 . A larger gearwheel  20  is rotatably supported on the sleeve pinion  19 . Furthermore, an electromagnetic switching coupling  83  is positioned on the sleeve pinion  19 . A first plate  84  of an electromagnetic switching coupling  83  is secured by pins  90 ,  91  on the gearwheel  20 , with a second plate  86  of the electromagnetic switching coupling  83  being secured by a feather key  87  on the sleeve pinion  19 . The gearwheel  20 , by way of its gear rim, engages the pinion  15 . The sleeve pinion  19 , in turn, engages the tooth segment  22  which is firmly connected to a first plate  24  of the setting device. By way of a needle bearing  23 , the plate  24  is rotatably supported on a projection of a cover  25  on which it is axially supported by way of an axial bearing  26 , a plate  27  and a securing ring  28 . The plate  24  cooperates with a further plate  29  which is slidingly supported on a projection of the plate  24  and which, by way of an axial bearing  30  and a disc  31 , is supported via pressure springs  33  on the cover  25 . The plate  31  acts on pressure pins  32  which are positioned in the pressure springs  33 . The pressure pins  32  form the direct setting members of the device. The surfaces of the plates  24 ,  29 , which face one another, are provided with pairs of grooves  34 ,  39  whose depth varies across the circumference and in which there run balls  35  held in a ball cage  36 . The plate  29  comprises a radial projection  37  with a guiding claw  38 . The guiding claw  38  slides in a longitudinally displaceable way on a holding pin  40  which is firmly inserted into a bore  55  in a housing wall  56  and which, in this way, holds the axially displaceable plate  29  in a rotationally fast way.  
         [0023]    [0023]FIGS. 5 and 6 will be described jointly below. They show a third embodiment of an axial setting device in accordance with the invention in a mounted condition. A driving motor  11  is shown to be provided with a motor shaft  12  and with a motor housing  13  in which the motor shaft  12  is supported twice. The motor housing  13  is inserted into a centering bore  51  in a housing wall  52 . On the motor shaft  12  there is secured by way of a pin  16   a  shaft journal  14  which forms a driving pinion  15 . A bearing journal  18  is inserted into a further bore  53  in the housing wall  52 . A sleeve pinion  19  is rotatably supported on the bearing journal  18  by way of two needle bearings  41 ,  42 . A larger gearwheel  20  is pressed on to the sleeve pinion  19  and, by way of its rim gear, engages the pinion  15 . The sleeve pinion  19 , in turn, engages a gearwheel  22  which, via a switching coupling  83 , can be connected to a first plate  24  of the setting device. A first plate  84  of the electromagnetic switching coupling  83  is firmly connected to the gearwheel  22 , and a second plate  86  of the electromagnetic switching coupling  83  is welded to the first plate  24  of the setting device. The first plate  84  of the switching coupling and the plate  24  are rotatably supported via a needle bearing  23 ,  23 ′ each on a projection of a cover  25  on which they are axially supported by way of an axial bearing  26 , a plate  27  and a securing ring  28 . The plate  24  cooperates with a further plate  29  which is slidingly supported on a projection of the plate  24  and which, by way of an axial bearing  30  and a disc  31 , is supported via pressure springs  33  on the cover  25 . The plate  31  acts on pressure pins  32  which are positioned in the pressure springs  33 . The pressure pins  32  form the direct setting members of the device. The surfaces of the plates  24 ,  29 , which face one another, are provided with pairs of grooves  34 ,  39  whose depth varies across the circumference and in which there run balls  35  held in a ball cage  36 . The plate  29  comprises a radial projection  37  with a guiding claw  38 . The guiding claw  38  slides in a longitudinally displaceable way on a holding pin  40  which is firmly inserted into a bore  55  in a housing wall  56  and which, in this way, holds the axially displaceable plate  29  in a rotationally fast way.  
         [0024]    The following applies to all three embodiments:  
         [0025]    When the driving motor  11  is driven for the purpose of positively setting the device, the electric switching coupling  83  is energised and thus closed. Driving the driving motor  11  thus causes the plate  24  to rotate, with the balls  35  moving from deeper ball groove regions to flatter ball groove regions in both plates, the result being that the second plate  29  is axially displaced on the projection of the plate  24  against the returning force of the springs  33 . The cover  25  normally forms part of the clutch carrier of a locking clutch, such as a locking clutch for locking a differential drive. According to first variant for returning the device, the driving motor  11  is driven in the opposite direction of rotation, so that the plate  24  is rotated in such a way that the balls move from the flatter ball groove regions into the deeper ball groove regions. The plate  29  follows axially under the influence of the pressure springs  33  until the balls reach the end stops in the ball grooves which, at the same time, form the deepest ball groove regions. The abrupt braking of the plate  24  and thus of the gearwheel  20 , which happens as a result, can therefore be prevented from affecting the driving motor  11 , as the electric switching coupling is opened at the same time, so that the rotor mass which constitutes the largest percentage of mass can continue to rotate freely. According to a further variant for returning the device, the electric switching coupling  83  is opened at the very start, in which case the plate  29  is returned entirely under the influence of the pressure springs  33 , which plate  29  then forces the plate  24  to rotate in the opposite direction of rotation in that the balls run from the flatter ball groove regions into the deeper ball groove regions. When the balls reach the end stops in the ball grooves which, at the same time, form the deepest ball groove regions, the rotor mass of the electric motor  11  has already been disconnected from the rotational masses of the setting device. The driving motor is normally a frequency-modulated electric motor but other types of electric motors are also contemplated by the present invention. In the first embodiment, the rotor mass, during the return movement, continues to rotate freely. In the second embodiment, the motor mass includes the gearwheels  15 ,  20  and in the third embodiment, it additionally includes the mass of the gearwheel  22 .  
         [0026]    From the foregoing, it can be seen that there has been brought to the art a new and improved axial setting device and switch coupling. While the invention has been described in connection with one or more embodiments, it should be understood that the invention is not limited to those embodiments. Thus, the invention covers all alternatives, modifications, and equivalents as may be included in the spirit and scope of the appended claims.