Abstract:
In the present invention, an improved planetary gearset which reduces the amount of vibration transferred from the planetary gearset to a housing. The present invention is a new way to interface the ring gear of a planetary gearset with the housing by incorporating a series of lugs around the ring gear and adjusting the number of lugs and the size and the shape of the lugs. The distribution of these lugs affects the sound levels transferred from the planetary gearset. Additionally, multiple rows of lugs can also be strategically arranged on one ring gear to gain further noise and vibration improvement.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to reducing the amount of vibration transferred from the ring gear of a planetary gearset to the housing used to support the ring gear. 
       BACKGROUND OF THE INVENTION 
       [0002]    A planetary gearset is a popular system widely used in many types of applications for speed and torque transfer. Numerous efforts have been made to reduce vibration, and therefore noise emitted by the planetary gear system during operation. However, there have been few published studies aimed at reducing the vibration levels through optimizing the interface between the planetary gearset and any supporting components. Planetary gearsets are commonly supported by grounding the ring gear of the planetary gearset to some type of housing. The housing is commonly part of a transfer case or transmission. The main problem occurs when the planetary gearset rotates. As this occurs, vibration is transferred from the planetary gearset to the housing of the transfer case (or transmission). This vibration is often transferred through other various components of the vehicle. Therefore, there exists a need for an improvement in the planetary gearset which would reduce vibration transferred through a transfer case, or transmission, and other vehicle components. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention is an improved planetary gearset which reduces the amount of vibration transferred from the planetary gearset to a housing. This reduction in vibration is accomplished through a new way of interfacing the ring gear of a planetary gearset with a housing by incorporating a series of lugs around the ring gear, as well as adjusting the number of lugs, the size, and the shape. The distribution of these lugs affects the vibration transferred from the planetary gearset to the housing. Additionally, multiple rows of lugs can also be strategically arranged on one ring gear to gain further noise and vibration improvement. The present invention is also directed to a vibration reduction planetary gearset having a sun gear mounted on an input shaft, at least one planetary gear in mesh with the sun gear, a ring gear surrounding and in mesh with the planetary gear, and a housing having at least one recess where the housing is used for receiving the ring gear. The present invention also has at least one lug fixed to and circumscribing the ring gear for locating the ring gear in the recess of the housing. When the ring gear is positioned in the housing such that the lug is received by the recess, it reduces the amount of vibration transferred from the sun gear and the planetary gear to the ring gear. This will result in a reduction in the amount of vibration transferred to the housing. 
         [0004]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0006]      FIG. 1  is a sectional side view of a transfer case incorporating a planetary gearset, according to the present invention; 
           [0007]      FIG. 2  is a front plan view of a planetary gearset with the housing removed to better display the series of lugs circumscribing the ring gear, according to the present invention; 
           [0008]      FIG. 3  is a front plan view of one embodiment of a ring gear for reducing vibration, according to the present invention; 
           [0009]      FIG. 4  is a front plan view of another embodiment of a ring gear for reducing vibration, according to the present invention; 
           [0010]      FIG. 5  is a perspective view of a ring gear incorporating a first row of lugs and a second row of lugs, according to the present invention; 
           [0011]      FIG. 6  is a perspective view of a ring gear having a first type of helical lugs circumscribing the ring gear, according to the present invention; 
           [0012]      FIG. 7  is a perspective view of a ring gear incorporating a second type of helical lugs circumscribing the ring gear, according to the present invention; 
           [0013]      FIG. 8  is a partial top view of a ring gear having the second type of helical lugs which also demonstrates the load applied to an individual helical lug, according to the present invention; 
           [0014]      FIG. 9  is a sectional perspective view of a ring gear having a first row of lugs and a second row of lugs, where the first row of lugs is of one height, and the second row of lugs is at another height, according to the present invention; 
           [0015]      FIG. 10  is a second perspective view of a ring gear having a first row of lugs and a second row of lugs, where the first row of lugs is at one height, and the second row of lugs is at another height, according to the present invention; and 
           [0016]      FIG. 11  is a side plan view of a ring gear incorporating a square lug, a triangle lug, a circular lug, a half-triangle lug and an involute spline lug, according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0018]    Referring to  FIGS. 1 and 2 , a planetary gearset having lugs for reducing vibration according to the present invention is shown at  10 . The gearset  10  includes a sun gear  12  mounted to an input shaft  14 . The input shaft  14  is rotationally supported by an input bearing  16 . Surrounding the sun gear  12  is a series of planetary gears  18 , which are in mesh with the sun gear  12 , and a ring gear  20 . Circumscribing the ring gear  20  is a plurality of lugs  22  which are used to locate the ring gear  20  in a housing  24 . The housing  24  includes a series of corresponding recesses  26  for receiving the lugs  22 , thereby holding the ring gear  20  in a permanent fixed position in the housing  24 . The planetary gears  18  are typically connected to a carrier  28  through the use of stub shafts  30 , and the carrier  28  is selectively connected to an output shaft  32 . The housing  24  has a first groove  34  for receiving the ring gear  20 . Holding the ring gear  20  in place in the first groove  34  is a snap ring  36  located in a second groove  38 . 
         [0019]    The sun gear  12  and the carrier  28  can be selectively coupled to the output shaft  32  through the use of a dog clutch  40 . The dog clutch  40  is able to slide along the rail  42  through the use of an actuator (not shown). The dog clutch  40  is connected to a sleeve  44 . The sleeve  44  has a set of teeth  46  which are engageable with either a set of corresponding teeth  48  on the carrier  28 , or a set of corresponding teeth  50  on the sun gear  12 . The sleeve  44  also has a set of teeth  52  which are splined to a set of corresponding teeth  53  on the output shaft  32 . The connection between the teeth  52  on the sleeve  44  and the teeth  53  on the output shaft  32  allows the sleeve  44  to slide along the output shaft  32 , while still transferring rotational force. 
         [0020]    During normal operation, the input shaft  14  drives the sun gear  12 , which in turn causes the planetary gears  18  to also rotate. It should also be noted that the input to the gearset  10  could be to the carrier  28 , and the output can be the sun gear  12 . The ring gear  18  is prevented from rotating inside the housing  24  by the lugs  22 . 
         [0021]    When the dog clutch  40  is moved to a position where the teeth  46  on the sleeve  44  are engaged with the set of corresponding teeth  48  on the carrier  28 , the gearset will operate in a low-speed, high-torque mode. Rotational force will be transferred from the input shaft  14  to the sun gear  12 ; the sun gear  12  will rotate and transfer this rotational force to the planetary gears  18 . Some of this force from the planetary gears  18  is transferred to the ring gear  20 . As the planetary gears  18  rotate, the carrier  28  will rotate as well; this in turn will cause the sleeve  44  and therefore the output shaft  32  to rotate. Because of the rotational force from the sun gear  12  being transferred through the planetary gears  18  and carrier  28  before being transferred to the output shaft  32 , the output shaft  32  will rotate at a slower speed, but will transfer a higher amount of rotational force compared to the input shaft  14 . This provides a high-torque, low-speed mode in which a vehicle incorporating the present invention can use the transfer case for towing or other applications requiring a high-torque output. 
         [0022]    When the dog clutch  40  is moved into a position where the teeth  46  are engaged with the set of corresponding teeth  50  on the sun gear  12 , speed and rotational force will be transferred directly from input shaft  14  through the sun gear  12  to the sleeve  44  and to the output shaft  32 . The ratio in this mode between input to output will be one-to-one. 
         [0023]    As all of the gears in the gearset  10  rotate, vibrations are generated throughout the entire gearset  10 , and are transferred to the housing  24 . The vibration will occur whether the dog clutch  40  is engaged with the sun gear  12  or the carrier  28 . The lugs  22  function not only to hold the ring gear  20  in a stationary position within the housing  24 , but also to reduce the vibrations transferred from the gearset  10  to the housing  24 . The vibrations transferred to the housing  24  occur with a specific frequency, behaving similar to a sinusoidal wave pattern, with the amplitude and frequency dependent upon the speed of rotation of the sun gear  12  and planetary gears  20 . 
         [0024]      FIG. 2  shows a side view of the planetary gearset  10  with the housing  24  removed to better display the lugs  22 . As can bee seen in  FIG. 2 , the lugs  22  circumscribe the ring gear  20 . Different types of applications can generate various types of vibrations, and the number, size, shape, and position of the lugs  22  is chosen to reduce the vibration transferred to the housing  24  based on the type of application where the housing  24  having the lugs  22  is being used. Also, other factors have to be taken into account when choosing the proper amount of lugs  22  for the design. Any number of lugs  22  can be used; as few as nine lugs  22  will show improvement in reducing the vibration between the housing  24  and the gearset  10 . The more lugs  22  that are used, the greater the improvement in reduction of vibration. 
         [0025]    One embodiment of a ring gear  20  incorporating lugs  22  according to the present invention is shown in  FIG. 3 . The ring gear  20  in this embodiment has eighteen lugs  22  spaced in specific positions around the ring gear  20 . The lugs  22  will absorb the vibration transferred from the ring gear  20  to the housing  24 . 
         [0026]    Initially, as more lugs  22  are added, the space between the corresponding recesses  26  will continuously decrease. Another embodiment of a ring gear  20  incorporating lugs  22  according to the present invention is shown in  FIG. 4 . The ring gear  20  in  FIG. 4  has thirty-six lugs  22 , which are equally spaced around the ring gear  20 . Because more lugs  22  have been added, the space between the lugs  22  is reduced, and the space between the recesses  26  is reduced as well. 
         [0027]    In another embodiment, multiple rows of lugs  22  can be strategically arranged on one ring gear  20  to gain further noise and vibration improvement. This achieves the same result as having the same number of lugs  22  spaced in a single row around the ring gear  20 . Referring to  FIG. 5 , the ring gear  20  is shown having a first row of lugs generally shown at  54  and a second row of lugs generally shown at  56 . The first row of lugs  54  and the second row of lugs  56  both have lugs  22  which are the same type of lugs  22  used in the prior embodiments previously discussed. However, the first row of lugs  54  is offset from the second row of lugs  56 , providing for a greater reduction in vibration. The advantage with this embodiment is that multiple rows allow for the same reduction in vibration compared to a single row having the same total number of lugs  22  as the multiple rows because there is a larger area which is used for absorbing vibration as compared to a ring gear  22  which has a single row of lugs  22 . Additionally, because the lugs  22  are arranged in rows, the spacing between the individual lugs  22  is greater, allowing for the housing to be manufactured with greater ease. 
         [0028]    Additional rows can be added, such as a third row of lugs  22  and a fourth row of lugs  22 , but increasing the number of rows presents similar problems seen with increasing the number of lugs  22  in a single row. As more rows are added, each row is offset from each of the prior rows, and the ring gear  20  becomes more costly and difficult to manufacture. 
         [0029]    An embodiment showing a variation of the shape of the lugs  20  is shown in  FIG. 6 .  FIG. 6  shows a series of helical lugs  58  circumscribing the ring gear  20 . Each helical lug  58  has a flat surface  60 , and an angled surface  62 . The flat surface  60  is similar in shape compared to the lugs  22  seen in the previous embodiments. The ring gear  20  in  FIG. 6  is inserted into the housing  24  in a similar manner as the ring gear  20  in previous the embodiments, with the exception that the recesses  26  in the housing  24  would be different in order to receive the helical lugs  58 . 
         [0030]    It should also be noted that the ring gear  20  in  FIG. 6  also has helical gear teeth  64 . The helical gear teeth  64  would be used with planetary gears having corresponding helical gear teeth. The purpose of having the helical lugs  58  serves two functions. The first function is that the angled surface  62  provides a larger surface area for absorbing vibration between the ring gear  20  and the housing  24 . The second function relates to the helical gear teeth  64 , which will be described later. 
         [0031]    Another type of helical lug design is shown in  FIG. 7 . The ring gear  20  in  FIG. 7  has another type of helical lug  66 . These helical lugs  66  have a first helical surface  68 , similar to the angled surface  62  on the helical lug  58 , but also have a second helical surface  70 . The helical lugs  66  having a first helical surface  68  and a second helical surface  70  have an even greater surface area for absorbing vibration. 
         [0032]    The ring gear  20  shown in  FIG. 7  also has helical gear teeth  64 , similar to the embodiment shown in  FIG. 6 . The angle of the helical gear teeth  64  and the angled surface  62  of the helical lugs  58  are angled in opposite directions of one another. Similarly, the first helical surface  68  and the second helical surface  70  of the helical lugs  66  in  FIG. 7  are also positioned at the opposite angle as the helical gear teeth  64 . As the planetary gears  20  having corresponding helical gear teeth rotate in the ring gear  20  shown in  FIG. 6  or  7 , a force is exerted on each of the helical gear teeth  64  in both  FIGS. 6 and 7 . Referring to  FIG. 8 , this force exerted on each of the helical lugs  58 , 66  is a tangential force  72 . Note that the helical lug  66  is shown in  FIG. 8 , but the loading applied to the helical lug  66  is applied to the helical lug  58  shown in  FIG. 6  in the same manner. This tangential force  72  is translated tangentially to the outside diameter of the ring gear  20 . This tangential force  72  results in two different forces applied to each helical lug  66 . The first force is a normal force  74  which is applied perpendicularly to the first helical surface  68  of each helical lug  66 ; the second force is translated as an axial force  76  which is translated parallel to the surface of the helical gear teeth  58 . 
         [0033]    A sun gear  12  used with a ring gear  18  according to the embodiment shown in  FIG. 6  or  7  would also have corresponding helical gear teeth to mesh with the helical gear teeth on the planetary gears. This type of gearset would have several thrust forces in the axial direction that would be balanced by the system. These forces are shown in  FIG. 1 . There are thrust forces  78  which would cause the sun gear  12  and hence the input shaft  14  to be driven away from the planetary gears  18 . These thrust forces  78  in the axial direction from the helical grooves on the sun gear  12  would be balanced by the input bearing  16 . There are also thrust forces  80  in the axial direction applied to the sun gear  12  and the ring gear  20  from the planetary gears  18 ; these thrust forces  80  are equal and opposite and cancel each other out. There are also thrust forces  82  in the axial direction applied from the ring gear  20  which are balanced by the snap ring  36 . The snap ring  36  can also absorb vibrations as they are transferred through the gearset  10 . The snap ring  36  is made of a softer material compared to the ring gear  20  and the other components, allowing for it to provide additional absorption of vibrations. 
         [0034]    One common advantage of both types of helical lugs  58 , 66  is that not only is there greater surface area for absorbing vibration, but as the planetary gears  18  having helical gear teeth rotate in the ring gear  20  also having helical gear teeth, the ring gear  20  will move axially in the housing  24  as vibration is transferred from the ring gear  20  to the housing  24 . This movement of the ring gear  20  will be very slight, approximately the distance between the lugs  58 , 66  on the ring gear  20  and the recesses in the housing  24 . This distance can vary, depending on the tolerances between the housing  24  and the ring gear  20 . The slight axial movement as the ring gear  20  absorbs vibration will cause some friction between the helical lugs  58 , 66  and their corresponding recesses in the housing  24 . Transferring this friction into heat is another way for vibration to be absorbed into the system. 
         [0035]    Another embodiment of the present invention is shown in  FIGS. 9 and 10 . The ring gear  20  in  FIGS. 9 and 10  has a first row of lugs generally shown at  54  and a second row of lugs generally shown at  56 , similar to what is also shown in  FIG. 5 . These rows  54 , 56  are also staggered, but different from  FIG. 5  is the added feature that the first row of lugs  54  is at a first height  84 , and the second row of lugs  56  is at a second height  86 . Arranging the first row of lugs  54  and the second row of lugs  56  in this manner increases the effect of phasing the first row of lugs  54  and the second row of lugs  56 . In this embodiment, the first row of lugs  54  set at the first height  84 , which is taller than the second height  86 , is installed in the housing  24  first, with the second row of lugs  56  having the second height  86  installed in the housing such that the second row of lugs  56  rests against the snap ring  34 . 
         [0036]      FIG. 10  shows a ring gear  20  having other various types of lug designs.  FIG. 10  shows that the lugs  22  could be in the form of a square  88 , triangle  90 , circle  92 , half-triangle  94 , or an involute spline  96 . The lugs  22  can also take the form of any type of polygon, and be suited to any type of application. 
         [0037]    The present invention is not limited to use for a transfer case. The present invention also includes use for any number of applications requiring the use of a planetary gearset, where a ring gear is to be held stationary. 
         [0038]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.