Abstract:
A power train of an automatic transmission includes an input shaft connected to a torque converter; an output gear; a transmission case; a first planetary gear set including a first operating member fixedly connected to the input shaft, a second operating member fixedly connected to the transmission case, and a third operating member; a second planetary gear set including a fourth operating member selectively connected to the third operating member, a fifth operating member selectively connected to the input shaft, second or third operating members, a sixth operating member selectively connected to the input shaft or transmission case, a seventh operating member selectively connected to the transmission case, and an eighth operating member acting as an output element, wherein the second planetary gear set outputs ten forward speeds and two reverse speeds; and a plurality of friction members selectively connecting the operating members, input shaft, or transmission case.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2007-0082376, filed in the Korean Intellectual Property Office on Aug. 16, 2007, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    (a) Field of the Invention 
         [0003]    The present invention relates to a power train of an automatic transmission for a vehicle. More particularly, the present invention relates to a power train of an automatic transmission for a vehicle which realizes ten forward speeds and two reverse speeds. 
         [0004]    (b) Description of the Related Art 
         [0005]    A typical shift mechanism of an automatic transmission utilizes a combination of a plurality of planetary gear sets. A power train of such an automatic transmission that includes the plurality of planetary gear sets changes rotating speed and torque received from a torque converter of the automatic transmission, and accordingly changes and transmits the changed torque to an output shaft. 
         [0006]    It is well known that when a transmission realizes a greater number of shift speeds, speed ratios of the transmission can be more optimally designed and therefore a vehicle can have better fuel mileage and better performance. For that reason, an automatic transmission that enables more shift speeds is under constant investigation. 
         [0007]    In addition, with the same number of speeds, features of a power train such as durability, efficiency in power transmission, and size depend a lot on the layout of combined planetary gear sets. Therefore, designs for a combining structure of a power train are also under constant investigation. 
         [0008]    Usually, development of a power train using planetary gear sets does not include devising a wholly new type of planetary gear set. To the contrary, it involves how single/double pinion planetary gear sets are combined, and how clutches, brakes, and one-way clutches are disposed to the combination of planetary gear sets such that required shift speeds and speed ratios are realized with minimal power loss. 
         [0009]    For a manual transmission, too many speeds cause a driver the inconvenience of excessive manual shifting. However, for an automatic transmission, a transmission control unit automatically executes shifting by controlling the operation of the power train, and therefore more speeds usually implies more merits. 
         [0010]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention has been made in an effort to provide a power train of an automatic transmission for a vehicle, which includes two planetary gear sets, five clutches, and two brakes, and realizes ten forward speeds and two reverse speeds. 
         [0012]    According to an exemplary embodiment of the present invention, a power train of an automatic transmission for a vehicle obtains a shift speed by combining two elements of five clutches and two brakes, and can shift by connecting or releasing one element. 
         [0013]    Thus, a power train of an automatic transmission for a vehicle according to an exemplary embodiment of present invention may be easily controlled and shift feel may be enhanced. 
         [0014]    A power train of an automatic transmission for a vehicle according to an exemplary embodiment of present invention may include: an input shaft connected to a torque converter; an output gear; a transmission case; a first planetary gear set that includes a first operating member fixedly connected to the input shaft, a second operating member fixedly connected to the transmission case, and a third operating member outputting a reduced speed by an operation of the first operating member and the second operating member; a second planetary gear set that includes a fourth operating member selectively connected to the third operating member, a fifth operating member selectively connected to the input shaft and selectively connected to the second operating member or selectively connected to the third operating member, a sixth operating member selectively connected to the input shaft or selectively connected to the transmission case, a seventh operating member selectively connected to the transmission case, and an eighth operating member always acting as an output element, wherein the second planetary gear set outputs ten forward speeds and two reverse speeds to the output gear; and a plurality of friction members selectively connecting the operating members, the input shaft, or the transmission case. 
         [0015]    The plurality of friction members may includes a first clutch selectively connecting the fourth operating member and the third operating member, a second clutch selectively connecting the fifth operating member and the third operating member, a third clutch selectively connecting the fifth operating member and the input shaft, a fourth clutch selectively connecting the sixth operating member and the input shaft, a fifth clutch selectively connecting the fifth operating member and the second operating member, a first brake selectively connecting the sixth operating member and the transmission case, and a second brake selectively connecting the seventh operating member and the transmission case. 
         [0016]    The first planetary gear set may be a double pinion planetary gear set that includes the first sun gear, the first planet carrier, and the first ring gear as an operating member. 
         [0017]    The first sun gear may be the first operating member, the first planet carrier may be the second operating member, and the first ring gear may be the third operating member. 
         [0018]    The second planetary gear set may be a compound planetary gear set in a combination of two double pinion planetary gear sets that share a pinion gear in common, and may include the second sun gear, the third sun gear, the second planet carrier, the second ring gear, and the third ring gear as operating elements. 
         [0019]    The second sun gear may be the fourth operating member, the third sun gear may be the fifth operating member, the second planet carrier may be the sixth operating member, the third ring gear may be the seventh operating member, and the second ring gear may be the eighth operating member. 
         [0020]    The first planetary gear set and the second planetary gear set may be disposed in a sequence of the first planetary gear set and the second planetary gear set from the torque converter, the first, second, and fifth clutches and the first brake may be disposed between the first planetary gear set and the second planetary gear set, and the third and fourth clutches and the second brake may be disposed opposite to the side of the torque converter with respect to the first planetary gear set and the second planetary gear. 
         [0021]    The power train of an automatic transmission according to an exemplary embodiment of the present invention may include two planetary gear sets, five clutches, and two brakes, and may realize ten forward speeds and two reverse speeds. 
         [0022]    The power train of an automatic transmission according to an exemplary embodiment of the present invention may be combined to obtain a shift speed by two elements of five clutches and two brakes, and can shift by connecting or releasing one element. Thus, a power train of an automatic transmission for a vehicle according to an exemplary embodiment of present invention may be easily controlled and shift feel may be enhanced. 
         [0023]    The above features and advantages of the present invention will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated in and form a part of this specification, and the following Detailed Description of the Invention, which together serve to explain by way of example the principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0025]      FIG. 1  is a schematic diagram showing a power train according to an exemplary embodiment of the present invention. 
           [0026]      FIG. 2  is an operational chart of a power train according to an exemplary embodiment of the present invention. 
           [0027]      FIG. 3  is a shift diagram of a power train according to an exemplary embodiment of the present invention. 
       
    
    
       [0028]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
         [0029]    In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0030]    Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is 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. 
         [0031]      FIG. 1  is a schematic diagram showing a power train according to an exemplary embodiment of the present invention. 
         [0032]    A power train according to an exemplary embodiment of the present invention includes a first and second planetary gear sets PG 1  and PG 2  that are disposed on an input shaft  20  that is connected to a torque converter TC. 
         [0033]    The first planetary gear set PG 1  is a double pinion planetary gear set that includes a first sun gear S 1 , a first ring gear R 1 , and a first planet carrier PC 1 . 
         [0034]    The second planetary gear set PG 2  is a compound planetary gear set in a combination of two double pinion planetary gear sets that share a pinion gear in common, and includes the second sun gear S 2 , the third sun gear S 3 , the second planet carrier PC 2 , the second ring gear R 2 , and the third ring gear R 3  as operating elements. 
         [0035]    The first planetary gear set PG 1  and the second planetary gear set PG 2  are disposed in a sequence of the first planetary gear set PG 1  and the second planetary gear set PG 2  from the torque converter TC. 
         [0036]    The power train according to an exemplary embodiment of the present invention is provided with first, second, third, fourth, and fifth clutches C 1 , C 2 , C 3 , C 4 , and C 5  and first and second brakes B 1  and B 2  as operating elements, and connects or releases each operating element according to requested shifting. 
         [0037]    The first sun gear S 1  is always fixedly connected to the input shaft  20 . 
         [0038]    The first carrier PC 1  is always fixedly connected to a transmission case  10 . 
         [0039]    The second sun gear S 2 , interposing the first clutch C 1 , is selectively connected to the first ring gear R 1 . 
         [0040]    The third sun gear S 3 , interposing the second, third, and fifth clutches C 2 , C 3 , and C 5 , is selectively connected to the first ring gear R 1 , the input shaft  20 , and the first carrier PC 1  respectively. 
         [0041]    The second carrier PC 2 , interposing the fourth clutch C 4 , is selectively connected to the input shaft  20 , or interposing the first brake B 1 , is selectively connected to the transmission case  10 . 
         [0042]    The third ring gear R 3 , interposing the second brake B 2 , is connected to the transmission case  10 . 
         [0043]    The second ring gear R 2  is connected to an output gear  30 . 
         [0044]    The first, second, and fifth clutches C 1 , C 2 , and C 5  and first brake  131  are disposed between the first planetary gear set PG 1  and the second planetary gear set PG 2 , and the third and fourth clutches C 3  and C 4  and the second brake B 2  are disposed opposite to the side of the torque converter TC. 
         [0045]    The power train according to an exemplary embodiment of the present invention operates clutches and brakes as shown in  FIG. 2 , and realizes ten forward speeds and two reverse speeds. 
         [0046]    That is, in the first forward speed the first clutch C 1  and the first brake B 1  are operated, and in the second forward speed the first clutch C 1  and the second brake B 2  are operated. In the third forward speed the first clutch C 1  and the fifth clutch C 5  are operated, and in the fourth forward speed the first clutch C 1  and the second clutch C 2  are operated. In the fifth forward speed the first clutch C 1  and the third clutch C 3  are operated, and in the sixth forward speed the first clutch and the fourth clutch C 4  are operated. In the seventh forward speed the third clutch C 3  and the fourth clutch C 4  are operated, and in the eighth forward speed the second clutch C 2  and the fourth clutch C 4  are operated. In the ninth forward speed the fourth clutch C 4  and the fifth clutch C 5  are operated, and in the tenth forward speed the fourth clutch C 4  and the second brake B 2  are operated. In the first reverse speed the second clutch C 2  and the first brake B 1  are operated, and in the second reverse speed the second clutch C 2  and the second brake B 2  are operated. 
         [0047]    The power train according to an exemplary embodiment of the present invention has eight operational elements as shown in  FIG. 3 . 
         [0048]    A first node N 1  is the first sun gear S 1 , a second node N 2  is the first ring gear R 1 , a third node N 3  is the first carrier PC 1 , a fourth node N 4  is the third sun gear S 3 , a fifth node N 5  is the third ring gear R 3 , a sixth node N 6  is the second carrier PC 2 , a seventh node N 7  is the second ring gear R 2 , and an eighth node N 8  is the second sun gear S 2 . 
         [0049]    Hereinafter, referring  FIG. 3 , shifting operation of the power train according to an exemplary embodiment of the present invention will be explained. 
         [0050]    The first clutch C 1  and the first brake B  1  are operated in the first forward speed. 
         [0051]    While the first sun gear S 1  of the first node N 1  receives the input speed, the third node N 3  operates as fixed element by connection to transmission case  10  and the sixth node N 6  operate as fixed element by engagement of the first brake B 1  and the second sun gear S 2  is connected by engagement of the first clutch C 1  with the first ring gear R 1  and rotates at the same speed as the first ring gear R 1 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 1 , and the shifting to the first forward speed is realized. 
         [0052]    The first clutch C 1  and the second brake B 2  are operated in the second forward speed. 
         [0053]    While the first sun gear S 1  of the first node N 1  receives the input speed, the third node N 3  operates as fixed element by connection to transmission case  10  and the fifth node N 5  operate as fixed element by engagement of the second brake B 2  and the second sun gear S 2  is connected by engagement of the first clutch C  1  with the first ring gear R 1  and rotates at the same speed as the first ring gear R 1 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 2 , and the shifting to the second forward speed is realized. 
         [0054]    The first clutch C 1  and the fifth clutch C 5  are operated in the third forward speed. 
         [0055]    While the first sun gear S 1  of the first node N 1  receives the input speed by engagement of the first clutch C 1 , the third node N 3  and the fourth node N 4  operate as fixed elements by engagement of the fifth clutch C 5 , and the second sun gear S 2  is connected with the first ring gear R 1  and rotates at the same speed as the first ring gear R 1 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 3 , and the shifting to the third forward speed is realized. 
         [0056]    The first clutch C 1  and the second clutch C 2  are operated in the fourth forward speed. 
         [0057]    While the first sun gear S 1  of the first node N 1  receives the input speed, the third node N 3  operates as a fixed element, and the second sun gear S 2  and the third sun gear S 3  are connected with the first ring gear R 1  by engagement of the first clutch C 1  and the second clutch C 2  respectively and rotate at the same speed as the first ring gear R 1 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 4 , and the shifting to the fourth forward speed is realized. 
         [0058]    The first clutch C 1  and the third clutch C 3  are operated in the fifth forward speed. 
         [0059]    While the first sun gear S 1  of the first node N 1  and the third sun gear S 3  of the fourth node N 4  receive the input speed, the third node N 3  operates as a fixed element. The second sun gear S 2  is connected with the first ring gear R 1  by engagement of the first clutch C 1  and rotates at the same speed as the first ring gear R 1 , and the third sun gear S 3  is connected with the input shaft  20  by engagement of the first clutch C 3  and rotates at the same speed as the input shaft  20 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 5 , and the shifting to the fifth forward speed is realized. 
         [0060]    The first clutch C 1  and the fourth clutch C 4  are operated in the sixth forward speed. 
         [0061]    While the first sun gear S 1  of the first node N 1  and the second carrier PC 2  of the sixth node N 6  receive the input speed, the third node N 3  operates as a fixed element. The second sun gear S 2  is connected with the first ring gear R 1  by engagement of the first clutch C 1  and rotates at the same speed as the first ring gear R 1 , and the second carrier PC 2  is connected with the input shaft  20  by engagement of the fourth clutch C 4  and rotates at the same speed as the input shaft  20 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 6 , and the shifting to the sixth forward speed is realized. 
         [0062]    The third clutch C 3  and the fourth clutch C 4  are operated in the seventh forward speed. 
         [0063]    The third sun gear S 3  of the fourth node N 4  and the second carrier PC 2  of the sixth node N 6  receive the input speed. The third sun gear S 3  and the second carrier PC 2  are connected with the input shaft  20  by engagement of the third clutch C 3  and the fourth clutch C 4  respectively, and rotate at the same speed as the input shaft  20 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 7 , and the shifting to the seventh forward speed is realized. 
         [0064]    The second clutch C 2  and the fourth clutch C 4  are operated in the eighth forward speed. 
         [0065]    While the first sun gear S 1  of the first node N  1  and the second carrier PC 2  of the sixth node N 6  receive the input speed, the third node N 3  operates as a fixed element. The third sun gear S 3  is connected with the first ring gear R 1  by engagement of the second clutch C 2  and rotates at the same speed as the first ring gear R 1 , and the second carrier PC 2  is connected with the input shaft  20  by engagement of the fourth clutch C 4  and rotates at the same speed as the input shaft  20 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 8 , and the shifting to the eighth forward speed is realized. 
         [0066]    The fourth clutch C 4  and the fifth clutch C 5  are operated in the ninth forward speed. 
         [0067]    While the second carrier sun gear PC 2  of the sixth node N 6  receives the input speed by engagement of the fourth clutch C 4 , the third node N 3  and the fourth node N 4  operate as fixed elements by engagement of the fifth clutch C 5 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 9 , and the shifting to the ninth forward speed is realized. 
         [0068]    The fourth clutch C 4  and the second brake B 2  are operated in the tenth forward speed. 
         [0069]    While the second carrier sun gear PC 2  of the sixth node N 6  receives the input speed by engagement of the fourth clutch C 1 , the fifth node N 5  operates as a fixed element by engagement of the second brake B 2 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed D 10 , and the shifting to the tenth forward speed is realized. 
         [0070]    The second clutch C 2  and the first brake B 1  are operated in the first reverse speed. 
         [0071]    While the first sun gear S 1  of the first node N 1  receives the input speed, the third node N 3  operate as fixed elements by connection to the transmission case  10  and the sixth node N 6  operate as fixed elements by engagement of the first brake B 1 , and the third sun gear S 3  is connected with the first ring gear R 1  by engagement of the second clutch C 2  and rotates at the same speed as the first ring gear R 1 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed R- 1 , and the shifting to the first reverse speed is realized. 
         [0072]    The second clutch C 2  and the second brake B 2  are operated in the second reverse speed. 
         [0073]    While the first sun gear S 1  of the first node N 1  receives the input speed, the third node N 3  operate as fixed elements by connection to the transmission case  10  and the fifth node N 5  operate as fixed elements by engagement of the second brake B 2 , and the third sun gear S 3  is connected with the first ring gear R 1  by engagement of the second clutch C 2  and rotates at the same speed as the first ring gear R 1 . In this case, according to cooperative reaction of the first planetary gear set PG 1  and the second planetary gear set PG 2 , the output element of the seventh node N 7  rotates at a speed R- 2 , and the shifting to the second reverse speed is realized. 
         [0074]    The forgoing 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 embodiment 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 technical spirit and scope of the present invention be defined by the Claims appended hereto and their equivalents.