Abstract:
An actuating mechanism for axial setting purposes, comprising three discs which are supported co-axially relative to an axis and of which a central disc is rotatable relative to the two outer discs, between the central disc and each of the outer discs, there are arranged sets of balls, the balls each run in pairs of circumferential grooves in the faces of the central disc and of one of the outer discs facing one another, the circumferential grooves comprise a circumferentially variable depth whose extension is such that, over the entire relative angle of rotation, the first outer disc moves axially from a first end position via a central position into a second end position which deviates from said first end position, and the second outer disc moves axially from a first end position via a second end position deviating therefrom back into the first end position.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to an actuating mechanism for axial setting purposes, comprising three discs which are supported co-axially relative to an axis and of which a central disc is rotatable relative to the two outer discs. Between the central disc and each of the outer discs, there are arranged sets of balls. The balls each run in pairs of circumferential grooves in the faces of the central disc and of one of the outer discs facing one another. The circumferential grooves comprise a circumferentially variable depth.  
           [0002]    Furthermore, the invention relates to an intermediate axle drive for vehicles driven by several axles.  
         BACKGROUND OF THE INVENTION  
         [0003]    Actuating mechanisms of the foregoing type are known from DE 39 28 816 C2 and DE 40 07 506 C1 and from DE 41 06 503 C1 wherein the two outer discs are provided for alternately opening and closing two friction couplings in a manual gearbox whose gear-wheels can be coupled in a force-locking way to an associated shaft by means of the friction couplings.  
           [0004]    From the publication “Integrated Transfer Case” by K. Lippitsch, submitted at the conference “Tagung Allradtechnik” (Conference Four-wheel Technology) taking place from Feb. 10, 11, 2000 in “Haus der Technik e.V.”, there is known an intermediate axle drive concerning a two-stage gearbox and a central differential with one locking coupling. The locking coupling is actuated by a ball ramp mechanism with two co-axially supported discs, whereas the two stage drive is switched by a switching claw which can be actuated via an electromagnetic axial setting device.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to provide a setting mechanism of the initially named type which can be used for setting processes of different kinds, such as in intermediate axle drives.  
           [0006]    The present invention provides an actuating mechanism of the foregoing type wherein, over the entire relative angle of rotation, the first outer disc moves axially from a first end position via a central position into a second end position which deviates from the first end position, and the second outer disc moves axially from a first end position via a second end position deviating therefrom back into the first end position.  
           [0007]    Furthermore, the present invention provides an intermediate axle drive for a vehicle driven by several axles, comprising a two-stage gearbox and a follow-up central differential with a locking coupling. The intermediate axle gearbox comprises an actuating mechanism for axial setting purposes comprising three discs which are supported co-axially relative to an axis and of which a central disc is rotatable relative to the two outer discs. Between the central disc and each of the outer discs, there are arranged sets of balls, the balls each run in pairs of circumferential grooves iii the faces of the central disc and of one of the outer discs facing one another. The circumferential grooves comprise a circumferentially variable depth whose extension is such that, over of the entire relative angle of rotation, the first outer disc moves axially from a first end position via a central position into a second end position which deviates from the first end position. The second outer disc moves axially from a first end position via a second end position deviating therefrom back into the first end position. The first outer disc is connected by means of a shift fork to a gearshift sleeve for the two-stage gearbox and the second outer disc acts on a pressure plate of the locking coupling of the central differential.  
           [0008]    In this way, it is possible to provide a device which, by means of standard rotary driving means, can achieve two different setting functions.  
           [0009]    The central disc can be driven by a rotary drive and the outer discs can be held in a rotationally fast way in a housing, or the central disc can be held in a rotationally fast way in a housing and the outer discs can be driven synchronously by the rotary drive. Finally, by making use of a stage which reverses the direction of rotation, it is not impossible for the central disc and the outer discs to be driven simultaneously in opposite directions of rotation by the rotary drive.  
           [0010]    With regard to a preferred use as an actuating mechanism for a two-stage gearbox and a locking coupling in an intermediate axle differential, the first outer disc, for example, over a first range of the angle of rotation, holds, without changing, its first end position; and over a second range of the angle of rotation, is axially transferred into the second end position; and, over a third range of the angle of rotation, holds, without changing, the second end position. The second outer disc, over the first range of the angle of rotation, changes from its first end position into the second end position; over the second range of the angle of rotation, holds, without changing, the second end position; and, over the third range of the angle of rotation, axially changes back from the second end position into the first end position.  
           [0011]    In this way, the available relative range of rotation is divided into three. Thus, in a central range of rotation, the locking coupling of the differential drive is opened, with the two-stage gearbox being shifted from the first stage into the second stage, whereas in the two end ranges of the range of rotation, the gear stage as shifted is retained, and the locking coupling of the central differential is going to be progressively closed.  
           [0012]    The central range for shifting between the two gear stages is divided up in such a way that within the axial shifting movement, there is additionally provided a central range in which a neutral position between the two gear stages is retained, without being changed, over a certain range of the angle of rotation of the discs. The respective position as set or the coupling condition can be recorded by a sensor at the central disc or at an element of the rotary drive of the disc.  
           [0013]    The differential drive can, for example, be a planetary drive whose input shaft carries the web with the planetary gears, whose sun gear is connected to a first output shaft and whose hollow gear is positioned on a hollow shaft which rotates with the first output shaft and which, via an intermediate gear, drives a second output shaft. The locking device can be a multi-plate clutch which is effective between the web and hollow gear and which can be loaded via a pressure plate and an axial bearing by the second disc.  
           [0014]    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  
       [0015]    For a more complete understanding of this invention, reference should now be made to the embodiment illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0016]    In the drawings:  
         [0017]    [0017]FIG. 1 shows a longitudinal section through an intermediate axle differential with an inventive actuating mechanism for axial setting purposes.  
         [0018]    [0018]FIG. 2 shows a schematic diagram of the intermediate axle differential according to FIG. 1.  
         [0019]    [0019]FIG. 3 shows parts of the actuating mechanism for axial setting purposes according to FIGS. 1 and 2 in an exploded view.  
         [0020]    [0020]FIG. 4, in a path-angle diagram, shows how the mechanism according to FIGS.  1  to  3  functions.  
         [0021]    [0021]FIG. 5 is a first view of the central one of the discs, as seen from the first outer disc.  
         [0022]    [0022]FIG. 6 is a view of the first outer disc, as seen from the central disc.  
         [0023]    [0023]FIG. 7 is a second view of the central one of the discs, as seen from the second outer disc.  
         [0024]    [0024]FIG. 8 is a view of the second outer disc, as seen from the central disc. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    [0025]FIG. 1 shows an intermediate axle differential drive whose drive housing  11  comprises a cover  12  with a passage and a second cover  13  with a passage and bearing portions. The drive housing  11  comprises two housing halves  16 ,  17 . In the housing, there is supported an input shaft  14 , an intermediate shaft  15  and two output shafts  29 ,  30 . The input shaft  14  and the intermediate shaft  15  form a two-stage gearbox  21  which can be made to engage in two different reduction stages by way of two pairs of gearwheels  22 ,  23 ,  24 ,  25  of different sizes, each of which are permanently engaged. The gearwheels  22 ,  24  are permanently coupled to the input shaft  14  in a rotationally fast way. The gearwheels  23 ,  25  which are rotatably supported on the intermediate shaft  15  can, via a gearshift sleeve  49 , be alternately coupled to a gearshift sleeve carrier  37  which is secured in a rotationally fast way between the gear wheels  23 ,  25  on the intermediate shaft  15 . Between its two positions of engagement with one of the gearwheels  23 ,  25 , the gearshift sleeve  49  can be moved into a neutral position which is indicated in the drawing. Both gearwheels  23 ,  25  rotate freely relative to the intermediate shaft  15 . The intermediate shaft  15  drives the two output shafts  29 ,  30  via a lockable planetary drive  71 . Directly on the intermediate shaft  15  there is positioned the web  72  of the planetary drive, into which web  72  there are inserted journals  73  which rotatably support planetary gears  74 . The planetary gears engage a sun gear  75  which is secured on the first output shaft  29 . Furthermore, the planetary gears engage a hollow gear  76  which is produced so as to be integral with a hollow shaft  77  which is rotatably supported in the housing  11  by ball bearings  67 ,  68 . The hollow shaft  77  carries a pinion  78  which engages an intermediate gear  79  which, in turn, engages a pinion  80  on the second output shaft  30 . A multi-plate clutch  81  is effectively arranged between the web  72  and the hollow gear  76  of the planetary drive  71 . Outer coupling plates  85  are positioned in a coupling carrier  84  formed on to the hollow gear  76  and rotate therewith. Inner coupling plates  83  are positioned on a sleeve  82  which is formed on to the web  72  and rotates therewith. If the multi-plate clutch  81  is in the open condition, the planetary drive  71  acts as an open differential drive. The web  72  with the planetary gears  74  is driven by the intermediate shaft  15 , with the planetary gears  74  driving the sun gear  75  and the hollow gear  76  at identical rotational speeds and with a torque distribution which corresponds to the ratio of the diameters of same, i.e. with an uneven torque distribution. Differences in the rotational speeds between the sun gear  75  and the hollow gear  78  and thus between the first output shaft  29  and the second output shaft  30  can be offset by rotating the planetary gears  74  on their journals  73 . If the multi-plate clutch  81  is closed, the differential effect is blocked in that the hollow gear  76  is coupled to the web  72 . As a result, the planetary gears  74  are held by the journals  73  in the hollow gear, so that the sun gear  75  is driven via the stationary planetary gears  74  at the same rotational speed as the hollow gear  76  by the web  72 . The hollow shaft  77  is thus coupled to the first output shaft  29 . The second output shaft  30  is thus driven via the gearwheel chain  78 ,  79 ,  80  at a fixed transmission ratio relative to the first output shaft  29  by the intermediate shaft  15 .  
         [0026]    The setting mechanism  31  causes the multi-plate clutch  81  to be opened as well as closed; it also causes the two-stage gearbox  21  to be shifted between a first gear stage  22 / 23 , a neutral position and a second gear stage  24 / 25 . The mechanism  31  comprises a central disc  32  which is rotatable via a tooth segment  33  by a rotary drive (not shown) relative to the intermediate shaft  15 , a first outer disc  34  which, via a driving head  35  engaging a shifting rod  36  supported in the housing, is supported in a rotationally fast way relative to the housing, as well as a second outer disc  38  which, via a driving claw  39 , is held in a rotationally fast way relative to the housing on a holding pin  40  inserted into the housing. Between the central disc  32  and the first outer disc  34  there are effective balls  43  which run in first ball grooves  42  in the central disc  32  and in second ball grooves  44  in the first outer disc  34 . Between the central disc  32  and the second outer disc  38 , there are effective second balls  47  which run in third ball grooves  46  in the central disc  32  and in fourth ball grooves  48  in the second outer disc  38 . As a result of the shape of the ball grooves which will be explained in greater detail below, a rotation of the central disc  32  relative to the first outer disc  34  can result in an axial displacement of the first outer disc  34  and thus in an axial displacement of a shifting yoke  50 . The shifting yoke  50  is positioned on the shifting rod  36  and is fixed on the shifting rod  36  between pairs of supporting springs  58  and securing rings  59  in an axially resilient way and by means of a bolt  51  in a rotationally fast way. At one end, the shifting rod  36  is supported on a pressure spring  60  in the housing  11  and at its other end it comprises three engaging notches  53  which can co-operate with an engaging ball  54  supported on the pressure spring  52  in three shifted positions. Via the shifting rod  36 , the pressure spring  60  holds the discs  34 ,  32 ,  38  and the balls  43 ,  47  in contact with one another and effects the return of the setting mechanism  31 . The three shifted positions correspond to the two transmission stages and the neutral position of the two-stage gearbox. The shape of the ball grooves, furthermore, ensures that a rotation of the central disc  32  relative to the second outer disc  38  results in an axial displacement of the latter second outer disc which, via an axial bearing  55  and a pressure ring  56 , acts on the multi-plate clutch  81  which is supported on a supporting disc  57  and is able to open or close same in the two outer positions. The input shaft  14  is supported in the housing  11  by means of rolling-contact bearings  64 ,  65 . Furthermore, the intermediate shaft  15  is supported by a ball bearing  66  and held in the planetary gears  74 . The hollow shaft  77  is supported by ball bearings  67 ,  68  in the housing and cover  13  respectively. The output shaft  29  is supported by needle bearings  61 ,  62  in the hollow shaft  77  and the second output shaft  30  is supported by ball bearings  69 ,  70  in the housing and cover  13  respectively.  
         [0027]    [0027]FIG. 2 shows a schematic diagram of the drive assembly according to FIG. 1 with its respective parts. FIG. 2 shows how the two-stage gearbox  21 , the multi-plate clutch  81  and the planetary drive  71  are associated with one another and how they cooperate with the shafts  14 ,  15 ,  29 ,  30 . However, the setting device  31  is eliminated altogether in FIG. 2. Any parts which are identical with the ones in FIGS.  1  have been given the same reference numbers. The illustration of the two-stage gearbox  21  explains in which way a displacement of the gearshift sleeve  49  by means of the shifting yoke  50  on the gearshift sleeve carrier  37  effects a change between the transmission stage low (gearwheels  22 ,  23  effective because the gearwheel  23  is coupled to the gearshift sleeve carrier  37 ) and the transmission stage high (gearwheels  24 ,  25  effective because the gearwheel  25  is coupled to the gearshift sleeve carrier  37 ). When the multi-plate clutch  81  is open, the planetary drive  71  is an open differential drive which permits differences in rotational speeds between the output shaft  29  towards the rear axle and the output shaft  30  towards the front axle. When the multi-plate clutch  81  is closed, the planetary drive  71  rotates in the form of a block and the first output shaft  29  and the hollow shaft  77  and thus also the second output shaft  30  are driven at identical rotational speeds.  
         [0028]    [0028]FIG. 3 shows several of the functional parts of the axial setting device  31  in an exploded view, with the reference numbers being the same as before. The central disc  32  with the tooth segment  33  cooperates via a reduction stage  93  with the driving pinion  92  of a drive  91  (not shown in detail). The reduction stage  93  comprises two gearwheels  94 ,  95 . It can be seen that the first outer disc  34 , the second outer disc  38 , the axial bearing  55 , the pressure ring  56 , the plates  83 ,  85  and the supporting ring  57  of the multi-plate clutch  81  are arranged co-axially relative to the central disc  32 . The sets of balls  43 ,  47  are arranged between the discs. The ball grooves in the discs will be described in greater detail below.  
         [0029]    Two diagrams in FIG. 4 show the settable path S 34  of the first outer disc at the bottom and the displacement path S 38  of the second outer disc at the top as a function of the angle of rotation α32 of the central disc. Because of the shape of the grooves  42 ,  44  between the central disc  32  and the first outer disc  34 , the setting path S 34 , starting from the central position 0° of the central disc  32 , on both sides, comprises a central gradient range I which drops linearly from a central setting path MID( 34 ) on one side as far as a minimum setting path 0( 34 ) and which, on the other side, linearly rises to a maximum setting path MAX( 34 ). As a result, when the discs  32 ,  34  rotate relatively to one another, the shifting yoke  50  and the gearshift sleeve  49 , in a first direction of rotation, are moved into engagement with the first transmission stage  22 / 23  and, in a second direction of engagement, with a second transmission stage  24 / 25 . As soon as the shifting yoke  50  has reached these positions, the axial path S 34  of the first outer disc  34  no longer changes when the central disc  32  continues to rotate because a neutral gradient range II follows in one direction of rotation and a neutral gradient range III follows in the other direction of rotation. Because of the shape of the grooves between the central disc  32  and the second outer disc  38 , the setting path S 38 , starting from the central position 0° of the central disc  32 , in a central range which is identical to the above-mentioned central range, at a minimum setting path 0( 38 ), comprises a non-effective neutral gradient range IV in both directions, which neutral gradient range IV corresponds to an open friction clutch  81 . As soon as in one direction of rotation of the central disc  32 , one of the transmission stages.  22 / 23 ,  24 / 25  is engaged completely, there additionally follow, with a further relative rotation, the gradient ranges V and VI in both directions, with the setting path rising linearly, as a result of which the friction clutch  81  is closed in each of the two stages at a constant rate. The maximum settable path MAX( 38 ) corresponds to the completely closed friction clutch  81 .  
         [0030]    As indicated by the lettering, there exists a central range of rotation around the central position °0 in which the clutch is permanently fully open and in which the two-stage gearbox is switched between the low transmission stage (low gear) and the high transmission stage (high gear); furthermore, there exist two end ranges in which one of the transmission stages is engaged and in which the friction clutch is going to be progressively closed.  
         [0031]    [0031]FIGS. 5 and 6 show the central disc  32  in a first view A-A and the first outer disc  34  in view B-B. It can be seen that, for rotating purposes, the central disc  32  comprises the tooth segment  33  and that the first outer disc  34  comprises the driving head  35 . Both discs can be seen to comprise three identically designed circumferentially extending ball grooves  42 ,  44  which, if mounted as specified, extend in opposite directions relative to one another. The ball grooves each comprise a central range 42I, 44I with a continuously changing depth which, in the case of rotation, lead to a displacement of the shifting claw, as well as two adjoining ranges 42II, 44II of a smaller depth and 42III, 44III of a greater depth which, if rotation continues, leave the shifting claw in the position it has reached and thus leave the shifted gear stage unchanged.  
         [0032]    [0032]FIGS. 7 and 8 show the central disc  32  with the tooth segment  33  on the circumference in view C-C and, in the view D-D, the second outer disc  38  with the driving claw  39  at the circumference, which two discs  32 ,  38  each comprise three ball grooves which correspond to one another. Each one of the ball grooves  46 ,  48  comprises a central portion 46IV, 48IV whose depth remains unchanged and which do not have a setting effect, as well as end portions 46V, 46VI, 48V, 48VI of a decreasing depth and thus of increasing setting paths.  
         [0033]    From the foregoing, it can be seen that there has been brought to the art a new and improved actuating mechanism for an axial setting device. 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.