Patent Publication Number: US-2005132835-A1

Title: Transfer driven gear

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority of Korean Application No. 10-2003-0093220, filed Dec. 18, 2003, the disclosure of which is incorporated herein by reference.  
     FIELD OF THE INVENTION  
      Generally, the present invention relates to a transfer driven gear. More particularly, the present invention relates to the transfer driven gear which has smaller weight and reduced deformation in a heat treatment.  
     BACKGROUND OF THE INVENTION  
      Generally, an automatic transmission has a mid-shaft for transferring torque converted by a shift-ratio of a main shift-range to a differential which is a final decelerating apparatus. For this purpose, a transfer gear set, which is a first decelerating apparatus, is utilized. However, this weight of the transfer gear set and deformation that can occur during the heat treatment used while making the transfer gear set, affects performance and quality of the automatic transmission.  
      As shown in  FIGS. 1 and 2 , a parking gear  11  is additionally manufactured on the transfer driven gear (forging type) and the parking gear  11  makes the transfer driven gear heavier too.  
      As described, the performance and quality of the transfer driven gear are greatly affected by the deformation during a heat treatment process.  
      On the other hand, a twist is occurred throughout the whole conventional transfer driven gear  10  because an air trap is occurred in a part A during the heat treatment process.  
      The twist is a cause of noise and a reduction of strength because the twist affects an array of the transfer driven gear.  
      The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.  
     SUMMARY OF THE INVENTION  
      Embodiments of the present invention provide a transfer driven gear having non-limiting advantages of reduced weight and reduced deformation which may be occurred in a heat treatment process.  
      An exemplary transfer driven gear according to an embodiment of the present invention includes: a shaft-hole formed in a center thereof; a plurality of gear teeth formed on an outer circumference thereof; and a rib formed between the shaft-hole and the gear teeth, wherein at least one air exhausting hole is formed on the rib such that air overheated during a heat treatment process is exhausted through the at least one air exhausting hole.  
      In a further embodiment, the transfer driven gear includes: a parking gear formed on one side of the rib; and the at least one air exhausting hole is formed as a plurality of holes, wherein at least one of the plurality of air exhausting holes is formed inside of the parking gear and at least one of the plurality of air exhausting holes is formed outside of the parking gear.  
      In another further embodiment, on the transfer driven gear the at least one air exhausting hole is formed as a plurality, and the plurality of air exhausting holes are radially formed.  
      In another further embodiment, on the transfer driven gear a parking gear is formed on one side of the rib and grooves for reducing weight are formed on an inner surface of the parking gear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention:  
       FIG. 1  is a perspective view showing a scheme of the transfer driven gear according to an embodiment of the present invention; and  
       FIG. 2  is a sectional view along line A-A of  FIG. 1  according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      An embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.  
      As shown in  FIGS. 1 and 2 , a transfer driven gear  20  may include: a shaft-hole  21  formed in a center thereof for an receiving a shaft; a plurality of gear teeth  22  formed on an outer circumstance thereof; and a rib  23  formed between the shaft-hole  21  and the gear teeth  22 . The transfer driven gear  20  is installed in a transfer gear set for transferring a torque converted by a shift-ratio of a main shift-range to a differential which is a final decelerating apparatus.  
      At least one air exhausting hole  24  is formed on the rib  23  such that air overheated during heat treatment is exhausted through the at least one air exhausting hole  24 . The heat treatment process is for manufacturing the transfer driven gear  20  and is a heating and cooling treatment for changing a metal tissue and quality of the transfer driven gear  20 .  
      Because the heat treatment process will be understood by persons having ordinary skill in this technical field, further explanation of the same is omitted.  
      In one embodiment, a parking gear  31  may be formed on one side of the rib  23 . In this case, the at least one air exhausting hole  24  is formed as a plurality of holes, wherein at least one of the plurality of air exhausting holes  24  is formed inside of the parking gear  31 . At least one of the plurality of air exhausting holes  24  is also formed outside of the parking gear  31 .  
      The parking gear  31  is used for parking a vehicle. It will be well understood by persons having ordinary skill in this technical field as to how the parking gear functions, so further explanation of the same is omitted.  
      As shown in  FIG. 1 , the at least one air exhausting hole  24  is preferably formed as a plurality, and the plurality of air exhausting holes  24  are radially formed but the location and number of the air exhausting holes  24  are not limited.  
      In an alternative embodiment, grooves  25  for reducing weight of the transfer driven gear  20  may be formed on an inner surface  30  of the parking gear  31  of the transfer driven gear  20 . The grooves  25  are preferably formed into a half circle type but other shapes may be used.  
      Performance of a transfer driven gear  20  according to an embodiment of the present invention is described hereinafter.  
      According to an embodiment of the present invention, a motivation for the present invention is to provide a high-quality automatic transmission by improving the transfer driven gear which greatly affects a performance and quality of an automatic transmission. Thus, one advantage of the present invention is to prevent twist throughout the whole transfer driven gear  20  resulting from air that might otherwise be trapped at B, under rib  23 , during the heat treatment process.  
      The air exhausting holes  24  for exhausting overheated air are formed in the rib  23  of the transfer driven gear  20 . Therefore, the air trap in the part B does not occur. In addition, the weight of the transfer driven gear  20  can be reduced by enlarging a size of the air exhausting holes  24  to a scope that does not affect strength of the transfer driven gear  20 .  
      In this case, a noise problem, which is one of the most important things in transmission development, can be solved. That is, a main cause of the noise problem is the twist occurring throughout the whole of transfer driven gear  20  after the heat treatment process. The noise problem can be solved because a lesser deformation in the heat treatment process makes a more uniform shape of the gear teeth  22  according to an embodiment of the present invention.  
      The grooves  25  which are formed in the parking gear  31  are enlarged to a size that does not affect a strength of the parking gear  31 .  
      The transfer driven gear  20  may be manufactured by forging, therefore the present invention may be realized only by a simple modification of a die-casting metallic pattern without raising the manufacturing costs.  
      As described above, the transfer driven gear advantages according to an embodiment of the present invention are described hereinafter.  
      A noise problem may be solved because a deformation by heat treatment is reduced, drivability is improved, and a weight is reduced by grooves of a parking gear and air exhausting holes for preventing a deformation during heat treatment process.  
      In addition, damping and intercepting parts for reducing noises can be reduced because of noise reduction.  
      While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.