Patent Publication Number: US-2004045389-A1

Title: Rotating housing and gear assembly

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of Invention  
       [0002] The subject invention relates to a rotating housing having a press fit internal gear.  
       [0003] 2. Description of the Related Art  
       [0004] Automotive transmissions commonly include one way clutch assemblies having a gear housing rotatably coupled to a shaft. The rotating housing fixedly supports an internal ring gear for rotating the housing about the shaft. One way clutch rotating housing and internal ring gear assemblies are often made of a single steel component, typically manufactured by machining or flow forming a steel forging. Alternately, an internal ring gear is sometimes welded by laser, or electron beam, to a stamped, machined or flow formed housing. These methods of production are expensive and provide for a final product which is excessively heavy. Putting an internal spline on the housing and an external spline on the ring gear has been proposed and once the two parts are joined, a c-clip is used to prevent the ring gear from coming out of the housing. This solution has the draw back of being difficult to hold the ring gear tightly and in a precise location. In addition torque reversals can cause the ring gear to click against the housing causing an objectionable noise in some applications, for example in an automobile transmission.  
       [0005] There are basically three existing solutions to design the product. For example, FIGS. 1, 1 a  and  1   b  show an aluminum rotating housing  103  with a steel gear  104  and a c-clip  105 . The housing  103  has an internal spline  114 , which is either machined or produced by flow forming or stamping. The forged and machined or powder metal steel gear  104  has an external spline  115 , which fits in the splined part of the aluminum rotating housing  103 . A c-clip  105  holds the steel gear  104  in place. The splines of both the steel gear  104  and the aluminum housing  103  need to be manufactured within tight tolerances, and hence high cost, otherwise the gear  104  will slightly rotate in relation to the housing  103  when torque is applied and produce a clicking noise.  
       [0006] Another possibility to secure the position of the gear to the aluminum housing is shown in FIGS. 2, 2 a  and  2   b . The aluminum housing  203  has various shaped stamped openings or slots  216  which are cast or machined into the wall of the housing  203 . A steel gear  204  includes protrusions or castellations  217  of corresponding shape and position as the openings  216  in the housing  203 . When the parts are assembled, the protrusions  217  will fit into the openings  216  of the housing  203  and torque can be transferred from the gear  204  to the housing  203 . A c-clip  205  retains the gear  204  in the housing  203  and prevents the gear  204  from moving in the axial direction relative to the housing  203 . But, if the protrusions  217  of the steel gear  204  or the openings  216  of the housing  203  are not manufactured within tight tolerances, the gear  204  will rotate slightly in relation to the housing  203  and produce a clicking noise once torque is applied thereto.  
       [0007] Finally, FIG. 3 shows yet another design approach of making the housing  303  and gear  304  in one piece out of steel. A one piece housing  303  can be flow formed or stamped, but typically needs extensive machining operations, particularly to form the gear teeth, which make it an expensive assembly. Also, since the one piece assembly is made entirely of steel, it will be heavier than a two piece aluminum housing and steel gear.  
       SUMMARY OF THE INVENTION  
       [0008] According to one aspect of the invention there is provided a housing and gear assembly comprising a cylindrical housing having an inner cylindrical wall and a center bore for rotatably mounting the housing on an elongated shaft. An internal ring gear having a plurality of internal gear teeth, an external circumferential wall and a plurality of spaced apart broach teeth projecting radially outwardly from the external wall is provided for cutting engagement with the internal wall of the housing as the ring gear is press fit into the housing to fixedly and rotationally secure the ring gear to the housing. A c-clip is used as a safety retainer to prevent the ring gear from backing out of its installed or assembly position.  
       [0009] The resulting assembly is a light weight rotating housing and ring gear due to the cast aluminum housing. In addition, the ring gear is fixed tightly, accurately and permanently in position. Since the ring gear is the broach tool, the fit is tight and no clicking will occur between the ring gear and the housing during torque reversals. Finally, the assembly is inexpensive as the cast aluminum housing and ring gear can each be produced inexpensively and assembly is simple and can be done in a press machine. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
     [0011]FIG. 1 is a partial cross-sectional side view of a prior art rotating housing and internal ring gear;  
     [0012]FIG. 1 a  is a perspective view of the prior art ring gear of FIG. 1;  
     [0013]FIG. 1 b  is a perspective view of the prior art housing of FIG. 1;  
     [0014]FIG. 2 is partial cross-sectional side view of another prior art rotating housing and internal ring gear;  
     [0015]FIG. 2 a  is a perspective view of the ring gear of FIG. 2;  
     [0016]FIG. 2 b  is a perspective view of the housing of FIG. 2;  
     [0017]FIG. 3 is partial cross-sectional side view of yet another prior art one piece rotating housing and gear;  
     [0018]FIG. 4 is an end view of an internal ring gear press fit into a rotating housing according to one aspect of the subject invention;  
     [0019]FIG. 5 is a side view of the housing and gear assembly of FIG. 4;  
     [0020]FIG. 6 is a cross-sectional view taken along line A-A of FIG. 5;  
     [0021]FIG. 7 is a perspective view of the housing and gear assembly of FIG. 4; and  
     [0022]FIG. 8 is a partially exploded view of the housing and gear assembly of FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0023] Referring to FIGS.  4 - 8 , the subject invention includes a rotating housing and internal ring gear assembly. The assembly includes an elongated shaft I for rotatably supporting a housing  3 . A bushing  2  is seated between the shaft  1  and housing  3  for limiting friction between the rotating housing  3  and the shaft  1 . The housing  3  is preferably made of aluminum, but could also be made of magnesium, plastic or other cast, molded or forged material without varying from the scope of the invention. The housing  3  is generally cylindrical and includes an inner cylinder wall  6  and center bore  7  for receiving the shaft  1  and bushing  2  therethrough. The assembly further includes a powder metal ring gear  4  having an internal spline or set of gear teeth  8  and an external circumferential wall  9 . A plurality of equally spaced apart external broach teeth  10  project radially outwardly from the external wall  9  for engagement with the inner wall  6  of the housing  3 . A cavity or trough  11  is recessed in the external circumferential wall  9  immediate adjacent one end of the teeth  10 . Finally, a pilot rim  12  extends around the lower portion of the external wall  9  for aligning and guiding the gear  4  into the housing  3 .  
     [0024] In assembly, the ring gear  4  is axially aligned with the center of the housing  3  within the perimeter of the inner cylinder wall  6 . The rotating housing  3  needs to have a specific inner diameter for the distance where the gear  4  is positioned to ensure a close fit between the parts. The gear  4  is pressed axially into the housing  3  and the pilot rim  12  aligns, centers and guides the gear  4  between the inner wall  6  of the housing  3 . Once properly aligned, the gear  4  is continued to be press fit axially into the housing  3  whereby the broach teeth  10  cut through and into the inner wall  6  of the housing  3 . The material or chips cut out of the housing  3  by the broach teeth  10  are collected in the trough  11  so as to not interfere with the fit between the gear  4  and housing  3  or the function of the gear teeth  8  or rotation of the housing  3  about the shaft  1 . Once the gear  4  is fully pressed into the housing  3 , a c-clip  5  is positioned in a channel  13  formed in the inner wall  6  to further retain the gear  4  within the housing  3 . Therefore, in operation, the rotational torque will be transferred from the gear  4  via the external broach teeth  10  to the rotating housing  3 .  
     [0025] It should be appreciated that the gear  4  may be of any other material, such as titanium, so long as it is harder than the housing  3  so that the broach teeth  10  will cut into the housing  3  during assembly. Additionally, an external gear with internal broach teeth could be used whereby the housing would retain the external gear. Further, an internal or external splined ring could also be used in place of the gear.  
     [0026] The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.  
     [0027] Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practised other than as specifically described.