Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority of Korean Patent Application Number 10-2012-0124150 filed Nov. 5, 2012 the entire contents of which application is incorporated herein for all purposes by this reference. 
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates, in general, to an automatic transmission, and more particularly, to the structure of a multi-stage automatic transmission which is disposed in a vehicle and can provide a plurality of transmission gear ratios. 
     2. Description of Related Art 
     In general, the multi-stage transmission mechanism of an automatic transmission is realized by combining a plurality of planet gears and friction elements. Because a vehicle having more excellent power performance and fuel efficiency can be realized when more shift ranges can be realized, studies on automatic transmissions which can realize more shift ranges are constantly underway. 
     In addition, even at the same shift range, the endurance, power transfer efficiency, size and the like of a gear train vary depending on the way that the plurality of planet gears and the friction numbers are combined. Therefore, attempts to invent a gear train structure which is stronger, consumes less power and is more compact have been made and are currently underway. 
     In addition, when a plurality of shift ranges are provided, at a viewpoint of shift control, whether or not a shift gear operation condition for disabling one friction element and enabling the other friction element during sequential shifting to the adjacent shift range is satisfied, and whether or not the shift ratio and range ratio between adjacent shift gears are of suitable levels, are two conditions gaining interest as distinctive functions in the field of gear trains. In addition, attempts to invent a gear train structure which satisfies such functions are underway. 
     The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     SUMMARY OF INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention is intended to propose a multi-stage automatic transmission in which planet gear mechanisms, external gears and friction elements are combined in order to realize nine forward gears and one rearward gear having excellent operating conditions for friction elements and superior shift range ratios, thereby achieving excellent power performance and fuel efficiency. 
     Various aspects of the present invention provide for a multi-stage automatic transmission which includes an input shaft; an output shaft disposed parallel to the input shaft; a first planet gear mechanism coaxially disposed on the input shaft, the first planet gear mechanism having two rotary elements which are connected to the input shaft so as to engage with and disengage from the input shaft; a second planet gear mechanism connected to the first planet gear mechanism via a plurality of pairs of external gears, the second planet gear mechanism being connected to the output shaft; the plurality of pairs of external gears for transferring power between one rotary element of the rotary elements of the second planet gear mechanism that is connected to neither the first planet gear mechanism nor the output shaft and the input shaft; a plurality of power engaging/disengaging members for switching power transmission via the plurality of pairs of external gears between the rotary elements of the second planet mechanism and the input shaft; and a restraint member capable of halting the movement of one rotary element of the rotary elements of the second planet gear mechanism which is connected to neither the first planet gear mechanism nor the output shaft. 
     In the multi-stage automatic transmission according to various aspects of the present invention, the planet gear mechanisms, the external gears and the friction elements are combined in order to realize nine forward gears and one rearward gear having excellent operating conditions for friction elements and superior shift range ratios, thereby achieving excellent power performance and fuel efficiency. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
         FIG. 2  is a table showing exemplary operation modes according to the present invention. 
         FIG. 3  is a lever diagram in which the structure of the transmission of  FIG. 1  is shown. 
         FIG. 4  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
         FIG. 5  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
         FIG. 6  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
         FIG. 7  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
         FIG. 8  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
         FIG. 9  is a configuration view showing an exemplary multi-stage automatic transmission according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Referring to  FIG. 1  to  FIG. 9 , a multi-stage automatic transmission according to various embodiments of the present invention includes an input shaft  10 , an output shaft  20 , a first planet gear mechanism PG 1 , a second planet gear mechanism PG 2 , a plurality of pairs of external gears, a plurality of power engaging/disengaging members and a restraint member. Here, the output shaft  20  is disposed parallel to the input shaft  10 . The first planet gear mechanism PG 1  is coaxially disposed on the input shaft  10 , and has two rotary elements which are connected to the input shaft  10  so as to engage with and disengage from the input shaft  10 . The second planet gear mechanism PG 2  is connected to the first planet gear mechanism PG 1  via the pairs of external gears, and is connected to the output shaft  20 . The plurality of pairs of external gears can transfer power between one rotary element of the rotary elements of the second planet gear mechanism PG 2  that is connected to neither the first planet gear mechanism PG 1  nor the output shaft  20  and the input shaft  10 . The plurality of power engaging/disengaging members can switch power transmission via the pairs of external gears between the rotary elements of the second planet mechanism PG 2  and the input shaft  10 . The restraint member can halt the movement of one rotary element of the rotary elements of the second planet gear mechanism PG 2  which is connected to neither the first planet gear mechanism PG 1  nor the output shaft  20 . 
     The multi-stage automatic transmission which realizes nine forward gears and one rearward gear is constructed of a combination of two planet gear mechanisms, five pairs of external gears and six friction elements which are disposed between the parallel input and output shafts  10  and  20 . 
     Here, the friction element is a term that comprehensively includes the power engaging/disengaging member and the restraint member. 
     According to various embodiments, one rotary element of the first planet gear mechanism PG 1  that is connected to the input shaft  10  such that the rotary element can engage with and disengage from the input shaft  10  is connected to the rotary element of the second planet gear mechanism PG 2  via a pair of external gears  51  and  52 . A first brake C 5  which can halt the rotation of the rotary elements connected to the first pair of external gears  51  and  52  is also provided. 
     The first planet gear mechanism PG 1  is configured as a double pinion planet gear mechanism, in which a first linear gear  41  and a first carrier  43  are connected to the input shaft  10  such that they can engage with and disengage from the input shaft  10 . The first carrier  43  is connected to the input shaft  10  via a first clutch C 1  such that it can engage with and disengage from the input shaft  10 . The first linear gear  41  is connected to the input shaft  10  via a second clutch C 2  such that it can engage with and disengage from the input shaft  10 . 
     In addition, the second planet gear mechanism PG 2  is configured as a single pinion planet gear mechanism. A second carrier  102  of the second planet gear mechanism PG 2  is connected to the first carrier  43  of the first planet gear mechanism PG 1  via the first pair of external gears  51  and  52 . A second ring gear  103  of the second planet gear mechanism PG 2  is connected to the output shaft  20 , and is connected to a first ring gear  42  of the first planet gear mechanism PG 1  via a second pair of external gears  61  and  62 . 
     One rotary element of the rotary elements of the second planet gear mechanism PG 2  which is connected to neither the first planet gear mechanism PG 1  nor the output shaft  20  is a second linear gear  101 . The pairs of external gears between the second linear gear  101  and the input shaft  10  include a third pair of external gears  71  and  72  which are linearly disposed between the input shaft  10  and the second linear gear  101 , a fourth pair of external gears  81  and  82 , and a fifth pair of external gears  91  and  92  which are disposed parallel to the third pair of external gears  71  and  72  and the fourth pair of external gears  81  and  82 . 
     The above described configuration is common to various embodiments of the present invention. 
     With reference to  FIG. 1 , the power engaging/disengaging members may include a third clutch C 3  which is disposed between the input shaft  10  and the third pair of external gears  71  and  72  and a fourth clutch C 4  which is disposed between the input shaft  10  and the fifth pair of external gears  91  and  92 . The restraint members are configured as a second brake C 6  which is directly coupled to the second linear gear  101 . 
     With reference to  FIG. 4 , the power engaging/disengaging members may include a third clutch C 3  which is disposed between the input shaft  10  and the third pair of external gears  71  and  72  and a fourth clutch C 4  which is disposed between the fifth pair of external gears  91  and  92  and the second linear gear  101 . The restraint members are configured as a second brake C 6  which is directly coupled to the second linear gear  101 . 
     With reference to  FIG. 5 , the power engaging/disengaging members may include a third clutch C 3  which is disposed between the fourth pair of external gears  81  and  82  and the second linear gear  101  and a fourth clutch C 4  which is disposed between the input shaft  10  and the fifth pair of external gears  91  and  92 . The restraint members are configured as a second brake C 6  which is directly coupled to the second linear gear  101 . 
     With reference to  FIG. 6 , the power engaging/disengaging members may include a third clutch C 3  which is disposed between the fourth pair of external gears  81  and  82  and the second linear gear  101  and a fourth clutch C 4  which is disposed between the fifth pair of external gears  91  and  92  and the second linear gear  101 . The restraint members are configured as a second brake C 6  which is directly coupled to the second linear gear  101 . 
     In addition, the first brake C 5  can be connected to the first carrier  43  of the first planet gear mechanism PG 1  which is connected to the first pair of external gears  51  and  52 . This configuration is commonly provided in various embodiments except for that shown in  FIG. 7 . 
     With reference to  FIG. 7 , the first brake C 5  may be connected to the second carrier  102  of the second planet gear mechanism PG 2  which is connected to the first pair of external gears  51  and  52 . That is, the first brake C 5  can be configured such that it is connectable to any element which is connected to the pair of external gears  51  and  52  so as to transfer power. 
     With reference to  FIG. 8 , the power engaging/disengaging members may include a third clutch C 3  which is disposed between the input shaft  10  and the third pair of external gears  71  and  72  and a fourth clutch C 4  which is disposed between the input shaft  10  and the fifth pair of external gears  91  and  92 . The restraint members are configured as a second brake C 6  which is directly connected between the fourth clutch C 4  and the fifth pair of external gears  91  and  92 . 
     With reference to  FIG. 9 , the power engaging/disengaging members may include a third clutch C 3  which is disposed between the input shaft  10  and the third pair of external gears  71  and  72  and a fourth clutch C 4  which is disposed between the input shaft  10  and the fifth pair of external gears  91  and  92 . The restraint members are configured as a second brake C 6  which is directly connected between the third clutch C 3  and the third pair of external gears  71  and  72 . 
     The various embodiments discussed herein, which are configured as above, may realize first to ninth forward shift gears and one rearward gear depending on the operation mode table shown in  FIG. 2 . As apparent from the operation mode table, the operating condition for disabling one friction element and enabling the other friction element during sequential shifting to the adjacent gear is satisfied, and the shift ranges between adjacent gears are set to be suitable. 
     For reference, each block in which one of numbers  4  to  10  is written as shown in the figures presents a section which corresponds to one lever in the lever diagram in  FIG. 3 . 
     For convenience in explanation and accurate definition in the Appended claims, the terms forward or rearward, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

Technology Category: 2