Patent Abstract:
A planetary gear structure includes a carrier, a plurality of pinion shafts each inserted into a bore in the carrier, and a stopper plate arranged between a pair of the pinion shafts to hold the pinion shafts without any revolutions on its own axis.

Full Description:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2003-090914 filed on Mar. 28, 2003, the entire content of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention generally relates to a planetary gear structure. More particularly, the present invention pertains to a stopper plate of a planetary gear structure for holding pinion shafts. 
   BACKGROUND OF THE INVENTION 
   An example of a known planetary gear structure is disclosed in Japanese Utility Model No. 2508622. This known planetary gear structure is constructed to fit a plurality of pinion shafts within a carrier. 
     FIGS. 4–7  illustrate an example of a known planetary gear structure  11  which is adapted to be assembled within a transmission. The planetary gear structure  11  includes a single stopper plate  106  which holds six pinion shafts  101  within a carrier  100 . Each of the pinion shafts  101  has a slit  103  so as to engage with the stopper plate  106 . The stopper plate  106  has three projecting portions  107 , each of which is arranged on the outer circumference of the stopper plate  106  so that adjacent projecting portions  107  are spaced apart from one another at equal angular intervals. Each of the projecting portions  107  is engaged with a bore  108  of the carrier  100  as shown in  FIG. 6  for fixing the stopper plate  106  against rotation after assembly. Here, the carrier  100  is attached to a housing  12  of the transmission. 
   To fix the pinion shafts  101  with the carrier  100 , each of the pinion shafts  101  is inserted into a respective receiving bore. Then, the stopper plate  106  is rotationally positioned so that the stopper plate  106  is near the predetermined pinion shafts  101 . This condition is shown by the broken line position in  FIG. 5 . Further, the stopper plate  106  is rotated in the counter-clockwise direction so that the slit  103  of each pinion shaft  101  engages or receives a portion of the stopper plate  106 . This condition is shown by the solid line position in  FIG. 5 . At that time, the projecting portions  107  are also engaged with the carrier  100 . 
   A purpose of the pinion shafts  101  is not only to rotatably support the pinions, but also to lubricate the oil-supplying passages  4 ,  5 . The lubricating oil is supplied to a bearing supporting the pinions, engagement portions between the pinion and a sun gear, engagement portions between the pinion and a ring gear, and engagement portions between the pinions. Therefore, the purpose of the stopper plate  106  for holding pinion shafts  101  is not only to fix the pinion shafts  101  to the carrier  100 , but also to prevent the pinion shafts from rotating on their respective axes and allow the openings of the oil-supplying passages to be appropriately positioned. 
   However, with the planetary gear structure  11  shown in  FIGS. 4–7 , because all of the pinion shafts  101  are fixed to the carrier  100  by way of the single stopper plate  106 , it is necessary that the position arrangements of the pinion shafts  101  be simultaneously done. Thus, the assembling time of the pinion shafts  101  is relatively long and the working thereof is somewhat troublesome. Further, because the stopper plate  106  is formed as a single piece, the fabrication of the stopper plate  106  can be relatively complicated. 
   SUMMARY OF THE INVENTION 
   According to one aspect, a planetary gear structure provided in a vehicle transmission comprises a carrier possessing a plurality of circumferentially spaced apart bores, a plurality of pinion shafts each adapted to receive a pinion gear, and at least three stopper plates. Each of the pinion shafts is positioned in one of the bores in the carrier so that the pinion shafts are circumferentially spaced apart from one another. The stopper plates are separate and spaced apart from one another, and are positioned between adjoining pairs of the pinion shafts. Each of the stopper plates engages two different ones of the pinion shafts to rotationally fix the pinion shafts against rotation relative to the carrier. 
   According to another aspect, a planetary gear structure comprises a carrier provided with a plurality of circumferentially spaced apart bores, a plurality of pinion shafts and a plurality of stopper plates. Each of the pinion shafts is adapted to receive a pinion gear and is positioned in one of the bores in the carrier so that the pinion shafts are circumferentially spaced apart from one another. The pinion shafts are each provided with a slit. The stopper plates are separate from one another and arranged between adjoining pairs of the pinion shafts. Each of the stopper plates engages the slit in two of the pinion shafts to fix the pinion shafts against rotation relative to the carrier. 
   In accordance with another aspect, a planetary gear structure comprises a carrier having a cylindrical portion, a plurality of pinion shafts mounted in the carrier along an axial direction of the cylindrical portion, and a stopper plate arranged between a pair of the pinion shafts so as to fix each of the pinion shafts against revolution about its own respective axis. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawing figures in which like reference numerals designate like elements. 
       FIG. 1  is an elevational view of one embodiment of the disclosed planetary gear structure according to the present invention. 
       FIG. 2  a cross-sectional view of the planetary gear structure taken along the section line II—II in  FIG. 1 . 
       FIG. 3  is an elevational view of another embodiment of the disclosed planetary gear structure according to the present invention. 
       FIG. 4  is a cross-sectional view of a transmission with a known planetary gear structure. 
       FIG. 5  is an elevational view of the planetary gear structure shown in  FIG. 4 . 
       FIG. 6  is a cross-sectional view of the planetary gear structure shown in  FIG. 5  taken along the section line VI—VI in  FIG. 5 . 
       FIG. 7  a cross-sectional view of the planetary gear structure shown in  FIG. 5  taken along the section line VII—VII in  FIG. 5 . 
   

   DETAILED DESCRIPTION 
     FIGS. 1 and 2  illustrate one version of the disclosed planetary gear structure according to the present invention. This disclosed version is a double-pinion type of planetary gear structure which can be used in a vehicle transmission. As shown in  FIG. 1 , the planetary gear structure generally comprises a carrier  10 , six pinion shafts  1  and three stopper plates  6 . The carrier  10  possesses an inner circumferential wall  10   a  and an outer circumferential wall  10   b . The outer circumferential wall  10   b  is formed in the shape of a cylindrical portion within the carrier  10 . Both the pinion shafts  1  and the stopper plates  6  are located between the inner circumferential wall  10   a  and the outer circumferential wall  10   b.    
   Each of the stopper plates  6  is arranged between a respective pair of adjacent pinion shafts  1  as shown in  FIG. 1 . Each of the stopper plates  6  possesses two side portions  6   a ,  6   b  positioned at oppositely located portions of the plate. Both side portions  6   a ,  6   b  extend along the radial direction of the cylindrical portion. Each of the stopper plates  6  also possesses an inner end portion  6   c  and an outer end portion  6   d . Once again, these inner and outer end portions are positioned at oppositely located portions of the plate. The stopper plates  6  can be positioned and dimensioned so that the inner end portion  6   c  contacts the inner circumferential wall  10   a  of the carrier  10  while the outer end portion  6   d  contacts the outer circumferential wall  10   b  when the stopper plates  6  are inserted into the carrier  10 . 
   The planetary gear structure also comprises a plurality of pinions  2 . Each of the pinions  2  is rotatably supported by a respective one of the pinion shafts  1 . Each of the pinion shafts  1  has a slit  3  that faces the respective stopper plates. Further, each of the pinion shafts  1  has oil passages  4 ,  5 . The oil passage  4  extends in the axial direction of the pinion shaft  1  while the oil passage  5  extends in the radial direction of the pinion shaft. Each of the pinion shafts  1  is assembled and adjusted so that openings of the oil passages  4 ,  5  face a specified portion where lubricating oil is necessary, for example the engagement portion between the pinion  2  and a sun gear or the engagement portion between the pinion  2  and a ring gear. 
   The assembly of the pinion shafts  1  into the carrier  10  with the stopper plate  6  can be carried out as follows. At first, the side portion  6   a  of one of the stopper plates  6  is inserted into the slit  3  of one of the pinion shafts  1 , and the opposite side portion  6   b  of that stopper plate  6  is inserted into the slit  3  of another one of the pinion shafts  1  to form a sub-assembly. Each of the other two stopper plates  6  is similarly inserted into the slits  3  of another pair of pinion shafts  1  to produce two other sub-assemblies. Each of the resulting sub-assemblies, in which the stopper plate  6  is sandwiched by two pinion shafts  1 , is arranged into the carrier  10 . That is, the two pinion shafts  1  of each respective sandwiched sub-assembly are inserted into respective bores in the carrier. When the stopper plates  6  are dimensioned in the manner described above, the inner end portion  6   c  of each stopper plate  6  contacts the inner circumferential wall  10   a  of the carrier  10  while the outer end portion  6   d  of each stopper plate  6  contacts the outer circumferential wall  10   a  of the carrier  10 . In this way, the stopper plates  6  are sandwiched between the circumferential walls  10   a ,  10   b  and are thus arranged within the carrier  10 . In the illustrated embodiment, the pairs of pinion shafts forming a sub-assembly are spaced apart at equal angular intervals as shown in  FIG. 1 . 
   According to this embodiment, each of the stopper plates  6  holds a pair of pinion shafts  1  for fixing the pinion shafts against rotation about their respective axes and relative to the carrier. Because the carrier  10  comprises three stopper plates  6 , a total of six pinion shafts  1  can be appropriately positioned relative to the carrier  10  by the stopper plates  6 . Further, because each of the stopper plates  6  is supported by a pair of the pinion shafts  1  and the circumferential walls  10   a ,  10   b  of the carrier  10 , each of the stopper plates  6  cannot readily move in either the radial direction of the cylindrical portion of the carrier  10  or in the peripheral direction thereof. Thus, the arrangement of the stopper plates  6  is well-balanced. Therefore, compared to the known planetary gear structure described above, the assembly of the pinion shafts  1  and the plates  6  is easier and the assembly time is shortened. Further, as the shape and size of the plates  6  is relatively simple and small, the weight of the planetary gear system is reduced as is the cost associated with forming the plates  6 . 
     FIG. 3  illustrates another version of the disclosed planetary gear structure according to the present invention. This planetary gear structure is a single-pinion type of planetary gear structure which can be used in a vehicle transmission. As shown in  FIG. 3 , a carrier  20  has a cylindrical portion. Three pinion shafts  21  are arranged at equal angular intervals relative to one another and are located within the cylindrical portion. Each of the pinion shafts  21  has a pair of slits  23 ,  23 , positioned so that the pinion shafts, viewed from the end, are symmetrical about a plane extending along the length of the shaft and extending midway between the two slits. The planetary gear structure also includes three stopper plates  26 , with each stopper plate being arcuate in shape and extending over a portion of the circumferential extent of the carrier. Each stopper plate  26  is arranged between two adjoining pinion shafts  21 . More specifically, one side portion of each stopper plate  26  is positioned in the slit  23  of one pinion shaft  21  while the opposite side portion of each stopper plate  26  is positioned in the slit  23  in the adjoining pinion shaft  21 . 
   The assembly of this version of the disclosed planetary gear structure involves positioning each of the stopper plates between two adjacent pinion shafts, thus forming a sub-assembly with three pinion shafts and three stopper plates. This sub-assembly can then be assembled to the carrier by inserting the pinion shafts in the respective bores of the carrier. 
   The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.

Technology Classification (CPC): 5