Abstract:
A planetary gear arrangement having at least three rotatable members with intermeshing gears and a primary torque path defined therein. At least one active friction damper is disposed between two of the planetary gear members, for example, a sun gear and a ring gear. The active damper is selectively operable to apply frictional engagement between the two members with which it is interconnected to establish a controlled secondary torque path therebetween. The active damper is effective to reduce gear lash changes between the gear members of a planetary assembly.

Description:
TECHNICAL FIELD 
     This invention relates to friction damping elements and, more particularly, to friction damping elements disposed within a planetary gear arrangement. 
     BACKGROUND OF THE INVENTION 
     Planetary systems have a plurality of meshing gear interfaces. Each of these gear meshes has a lash quantity built in for manufacturing purposes mostly. Therefore, during operation, the lash, which is the distance between the meshing gear teeth while they are in mesh, can reverse from being a driving tooth engagement to a driven tooth engagement. For example, the sun gear therein provides a driving arrangement to the planet pinions, which then provide a driving arrangement to the ring gear. However, should the torque or driving force at the sun gear be reversed and/or allowed to coast, the driving connection between the gear teeth will be reversed. That is, the ring gear will begin to drive the pinion gear and the pinion gear will drive the sun gear. Thus, the side of the tooth of each respective gear has reversed and has driving and driven capabilities. 
     It is known to put an active friction type damper between two shafts in a countershaft type transmission to reduce the gear rattle or lash change between the gear members on the input shaft, the output shaft, and the countershaft. In these arrangements, it is proposed to put the damper between the input shaft and the output shaft, which are coaxially aligned and supported one within the other. Such an arrangement is shown in U.S. Pat. No. 6,477,909 issued to Gilbert et al. on Nov. 12, 2002. This patent is assigned to the assignee of the present application. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved planetary gear arrangement having a friction damping interface between two members of the planetary gearset. 
     In one aspect of the present invention, an active damper mechanism is placed between the sun gear member of the planetary gearset and the ring gear member of the planetary gearset. 
     In another aspect of the present invention, a selectively active damper is placed between the ring gear member of a planetary gearset and the carrier member of a planetary gearset. 
     In yet another aspect of the present invention, an active damper is disposed within an all wheel drive transfer planetary gear arrangement. 
     In yet still another aspect of the present invention, the all wheel drive planetary gear arrangement has an input carrier member, a front output sun gear, a rear output sun gear, and pinion gears intermeshing with each other and with respective ones of the sun gears, and wherein an active damper mechanism is disposed between the input carrier and the front output sun gear. 
     In a yet still another aspect of the present invention, an active damper is disposed within the all wheel drive transfer planetary gear arrangement between the input carrier and the rear output sun gear. 
     In a further aspect of the present invention, active damper mechanisms can be positioned between the intermeshing planet pinion gears and/or between the output sun gear and one of the pinion gears meshing therewith. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a planetary gearset incorporating the present invention. 
         FIG. 2  is an exploded view of the planetary gearset shown in  FIG. 1  depicting an active damper mechanism between various members of the planetary gearset. 
         FIG. 3  is a schematic representation of a planetary gearset used in an all wheel drive transfer planetary gear arrangement and incorporating the present invention. 
         FIG. 4  is a view taken along line  4 — 4  of  FIG. 3 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there is seen in  FIG. 1  a planetary gear arrangement  10  including a sun gear member  12 , a ring gear member  14 , and a planet carrier assembly member  16 . The planet carrier assembly member  16  includes a planet carrier member  18  having rotatably mounted thereon a plurality of pinion gears  20 , which are disposed in meshing relationship with both the sun gear member  12  and the ring gear member  14 . 
     As is well known, when the sun gear member  12  rotates in the direction of Arrow A, the ring gear member  14  will rotate in the direction of Arrow B. Also, when the ring gear member  14  rotates in the direction of Arrow C, the sun gear member  12  will rotate in the direction of Arrow D. During normal transmission operation, the sun gear member  12  will be rotating in the direction of Arrow A to drive the ring gear member  14  in the direction of Arrow B. At sometime during the operation, the planetary gear arrangement  10  may change from a driving planetary gearset to a coasting planetary gearset in which case the ring gear member  14  may rotate in the direction of Arrow C and thereby driving the sun gear member  12  in the direction of Arrow D. 
     During this interchange of rotational torque transmission, the intermeshing gear teeth between the sun gear member  12  and the pinion gears  20  and also between the ring gear member  14  and the pinion gears  20  will be transferred from one side of the teeth to the other. Since the teeth of meshing gears cannot be continuously in contact with both sides, some lash is built into the system to permit the reversal of torque through the planetary gearset. However, the lash condition can produce a noise relationship, which is not desirable. 
     To accommodate this situation in the present invention, an active friction damper  22  is disposed, as seen in  FIG. 2 , to engage the sun gear member  12  and the ring gear member  14 . When the torque reversal or drive reversal occurs within the planetary gear arrangement  10 , the friction damper  22  is activated such that the ring gear member  14  and sun gear member  12  have a slipping frictional component generated therebetween, which reduces the speed or the velocity at which the lash condition changes from a sun gear drive condition to a ring gear drive condition thereby reducing the noise which might otherwise occur. 
     Also shown in  FIG. 2  is an active friction damper  24 , which is disposed between the ring gear member  14  and the planet carrier member  18 . The damper in this position can also be activated during a torque reversal within the system to eliminate the gear interface noise that might be generated during such torque reversal. It is possible in assemblies to use one of the friction dampers either  22  or  24 , or to incorporate both of the friction dampers  22  and  24 . Preferably, the friction dampers are controlled by a conventional electronic control unit (ECU), not shown, which is sensitive to the operating condition of the transmission and also the operating condition of the engine. 
     During certain operating conditions, the ECU will issue electronic signals to the damper  22  and/or the damper  24  to cause energization of the dampers just during the time period that a noise is most likely to occur. These conditions might occur with engine throttle position change, gear ratio change within the transmission, or a number of other conditions. Each of these conditions is known to the ECU, which generally includes a conventional programmable digital computer to provide the speed necessary for the actuation of the devices within the transmission. The construction and operation of these mechanisms, such as the ECU, is well known within the art of transmission design and construction. 
     The active dampers  22  and  24  are operable to apply a frictional drag torque between the two components that they contact. The level or amount of drag torque applied is not capable of rendering the two components to rotate in unison, it merely retards any rapid relative rotational changes between the two, which eliminates the lash noise that might otherwise occur. 
       FIGS. 3 and 4  depict schematically and diagrammatically a planetary differential generally designated  40 . The planetary differential  40  includes an input planet carrier assembly member  42 , a first output sun gear  44 , and a second output sun gear  46 . The planet carrier assembly member  42  includes a planet carrier assembly member  47  having side plates  48  and  50  that are interconnected through extensions  52 . A pair of meshing pinion gears  54  and  56  is rotatably supported on pins  58  and  60 , respectively. The pins  58  and  60  are secured to the side plates  48  and  50 . The pinion gears  54  and  56  mesh with the sun gears  44  and  46 , respectively. 
     The side plate member  48  can be operatively connected with the sun gear member  44  through an active damper  62  and the side plate member  50  can be operatively connected with the sun gear member  46  through an active damper  64 . The active damper  62  is effective to control rapid speed changes between the sun gear  44  and the planet carrier assembly member  47 , which will, of course, reduce gear lash noise between the pinion gears  54  and the sun gear  44 . 
     The active damper  64  is effective when operated to reduce rapid velocity changes between the side plate  50  and the sun gear  46  thereby reducing the gear lash noises between the sun gear  46  and the pinion gear  56 . It is also possible to position active dampers between the pinion gears  54  and  56  and the planet carrier side plates  48  and  50 . Activation of these friction dampers will reduce or eliminate lash noise between the meshing pinion gears  54  and  56 . 
     In view of the above description, it will now be evident to those skilled in the art that the active dampers may be placed either singularly or in combination between various members of the planetary gear arrangement to accommodate the reduction in lash noise which can occur during various operating conditions such as throttle changes of the engine or ratio changes at the transmission.