Abstract:
The present disclosure is a multi-stage transmission for a vehicle that has at least ten forward shifting stages and one reverse shifting stage. The multi-stage transmission has a relatively small number of parts and a simple configuration such that an engine may be operated at desired operation, thereby providing an improvement in the fuel efficiency of the vehicle, and the engine may be operated more quietly, thereby improving the quietness of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Korean Patent Application No. 10-2015-0027959, filed on Feb. 27, 2015, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present disclosure generally relates to a multi-stage transmission for a vehicle. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Recent rising oil prices have driven car manufacturers worldwide into competition to improve fuel efficiency. In addition, great efforts have been made to reduce the weight and improve the fuel efficiency of engines based on a variety of techniques such as downsizing, and similar measures. 
     Meanwhile, among methods utilized for transmissions equipped in vehicles to improve fuel efficiency, there is a method allowing an engine to operate at more efficient operation points using a multi-stage transmission, thereby improving the fuel efficiency and allowing an engine to operate in a relatively low RPM (revolutions per minute) range. 
     However, as the number of shifting stages of a transmission increases, the number of internal parts constituting the transmission also increases. This may lead to undesirable effects, such as the reduced mountability and transfer efficiency, and the increased cost and weight of the transmission. 
     SUMMARY 
     The present disclosure provides a multi-stage transmission for a vehicle that has at least ten forward shifting stages and one reverse shifting stage with a relatively small number of parts, and a simple configuration such that an engine may be operated at desired operation points, thereby providing an improvement in the fuel efficiency of the vehicle, and the engine may be operated more quietly, thereby improving the quietness of the vehicle. 
     According to one form of the present disclosure, there is provided a multi-stage transmission for a vehicle including: an input shaft; an output shaft; first through fourth planetary gear devices disposed between the input shaft and the output shaft to transmit rotary force. Each of the first through fourth planetary gear devices has three rotary elements, and at least six shifting elements connected to the rotary elements of the planetary gear devices. A first rotary element of the first planetary gear device stays connected to a third rotary element of the fourth planetary gear device, a second rotary element of the first planetary gear device stays connected to the input shaft and variably connected to a first rotary element of the second planetary device and a third rotary element of the third planetary device, respectively, a third rotary element of the first planetary gear device stays connected to a second rotary element of the second planetary gear device. The second rotary element of the second planetary gear device stays connected to a first rotary element of the third planetary gear device, and a third rotary element of the second planetary gear device stays connected to a second rotary element of the third planetary gear device. The first rotary element of the third planetary gear device is installed to be selectively fixable by one of the at least six shifting elements, and the second rotary element the third planetary gear device stays connected to a first rotary element of the fourth planetary gear device. The first rotary element of the fourth planetary gear device is installed to be selectively fixable by another of the at least six shifting elements. A second rotary element of the fourth planetary gear device stays connected to the output shaft, and the third rotary element of the fourth planetary gear device is installed to be fixable by further another of the at least six shifting elements. 
     According to the present disclosure, as set forth above, the multi-stage transmission for a vehicle can realize at least ten forward shifting stages and one reverse shifting stage with a relatively small number of parts and a simple configuration such that the engine may be operated at optimum operation points, thereby maximizing an improvement in the fuel efficiency of the vehicle, and the engine may be operated more quietly, thereby improving the quietness of the vehicle. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms, given by way of example, references being made to the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating the configuration of a multi-stage transmission for a vehicle according to in one form of the present disclosure; and 
         FIG. 2  illustrates an operation mode table of the transmission shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     Referring to  FIGS. 1 and 2 , a multi-stage transmission for a vehicle according to one form of the present disclosure may include an input shaft “IN”; an output shaft “OUT”; a first through fourth planetary gear devices “PG 1 ”, “PG 2 ”, “PG 3 ” and “PG 4 ” disposed between the input shaft “IN” and the output shaft “OUT” to transmit rotary force. Each of the first through fourth planetary gear devices, PG 1 , PG 2 , PG 3  and PG 4 , has three rotary elements, and at least six shifting elements, e.g. clutches CL 1 -CL 6 , connected to the rotary elements of the first through fourth planetary gear devices, PG 1 -PG 4 . 
     A first rotary element S 1  of the first planetary gear device PG 1  is variably connected (i.e. is selectively, intermittently connected) to a third rotary element R 4  of the fourth planetary gear device PG 4 . A second rotary element C 1  of the first planetary gear device PG 1  stays connected to the input shaft IN, and variably connected to a first rotary element S 2  of the second planetary gear device PG 2  and a third rotary element R 3  of the third planetary gear device PG 3 , respectively. A third rotary element R 1  of the first planetary gear device PG 1  stays connected to a second rotary element C 2  of the second planetary gear device PG 2 . 
     The second rotary element C 2  of the second planetary gear device PG 2  stays connected to a first rotary element S 3  of the third planetary gear device PG 3 , and a third rotary element R 2  of the second planetary gear device PG 2  stays connected to a second rotary element C 3  of the third planetary gear device PG 3 . 
     The first rotary element S 3  of the third planetary gear device PG 3  is installed to be selectively fixable by one shifting element of the at least six shifting elements and the second rotary element C 3  of the third planetary gear device PG 3  stays connected to a first rotary element S 4  of the fourth planetary gear device PG 4 . 
     The first rotary element S 4  of the fourth planetary gear device PG 4  is installed to be selectively fixable by another rotary element of the at least six shifting elements. A second rotary element C 4  of the fourth planetary gear device PG 4  stays connected to the output shaft OUT. The third rotary element R 4  of the fourth planetary gear device PG 4  is installed to be selectively fixable by further another shifting element of the at least six shifting elements. 
     The first planetary gear device PG 1 , the second planetary gear device PG 2 , the third planetary gear device PG 3  and the fourth planetary gear device PG 4  are sequentially arranged along the axial direction of the input shaft IN and the output shaft OUT. 
     The first rotary element S 3  of the third planetary gear device PG 3  is installed to be selectively fixable to a transmission case CS by means of a third clutch CL 3  from among the at least six shifting elements. The first rotary element S 4  of the fourth planetary gear device PG 4  is installed to be selectively fixable to the transmission case CS by means of a fourth clutch CL 4  from among the at least six shifting elements. The third rotary element R 4  of the fourth planetary gear device PG 4  is installed to be selectively fixable to the transmission case CS by means of a fifth clutch CL 5  from among the at least six shifting elements. 
     Therefore, the third clutch CL 3 , the fourth clutch CL 4  and the fifth clutch CL 5  function as brakes, respectively, such that the first rotary element S 3  of the third planetary gear device PG 3 , the first rotary element S 4  and the third rotary element R 4  of the fourth planetary gear device PG 4  may be converted to rotatable state or restrained state not to be rotated by means of the operations of the third clutch CL 3 , the fourth clutch CL 4  and the fifth clutch CL 5 , respectively. 
     The other shifting elements, from among the at least six shifting elements, are configured to constitute variable connection structures between the rotary elements of the planetary gear devices. 
     Specifically, a first clutch CL 1 , from among the at least six shifting elements, forms a variable connection structure between the second rotary element C 1  of the first planetary gear device PG 1  and the first rotary element S 2  of the second planetary gear device PG 2 . A second clutch CL 2 , from among the at least six shifting elements, forms a variable connection structure between the second rotary element C 1  of the first planetary gear device PG 1  and the third rotary element R 3  of the third planetary gear device PG 3 . A sixth clutch CL 6 , from among the at least six shifting elements, forms a variable connection structure between the first rotary element S 1  of the first planetary gear device PG 1  and the third rotary element R 4  of the fourth planetary gear device PG 4 . 
     According to this form, the first rotary element S 1 , the second rotary element C 1  and the third rotary element R 1  of the first planetary gear device PG 1  are a first sun gear, a first carrier and a first ring gear, respectively. The first rotary element S 2 , the second rotary element C 2  and the third rotary element R 2  of the second planetary gear device PG 2  are a second sun gear, a second carrier and a second ring gear, respectively. The first rotary element S 3 , the second rotary element C 3  and the third rotary element R 3  of the third planetary gear device PG 3  are a third sun gear, a third carrier and a third ring gear, respectively. The first rotary element S 4 , the second rotary element C 4  and the third rotary element R 4  of the fourth planetary gear device PG 4  are a fourth sun gear, a fourth carrier and a fourth ring gear, respectively. 
     The multi-stage transmission for a vehicle configured as above may also be presented as follows. 
     Specifically, the multi-stage transmission for a vehicle according to the present invention includes the first to fourth planetary gear devices PG 1  to PG 4  each having the three rotary elements; the six shifting elements configured to variably provide frictional force; and eight rotary shafts connected to the rotary elements of the first to fourth planetary gear devices. 
     Hence, from among the eight rotary shafts, the first rotary shaft RS 1  is the input shaft IN directly connected to the second rotary element C 1  of the first planetary gear device PG 1 . The second rotary shaft RS 2  is directly connected to the first rotary element S 1  of the first planetary gear device PG 1 . The third rotary shaft RS 3  is directly connected to the third rotary element R 4  of the fourth planetary gear device PG 4 . The fourth rotary shaft RS 4  is directly connected to the third rotary element R 1  of the first planetary gear device PG 1 , the second rotary element C 2  of the second planetary gear device PG 2  and the first rotary element S 3  of the third planetary gear device PG 3 . The fifth rotary shaft RS 5  is directly connected to the first rotary element S 2  of the second planetary gear device PG 2 . The sixth rotary shaft RS 6  is directly connected to the third rotary element R 2  of the second planetary gear device PG 2 , the second rotary element C 3  of the third planetary gear device PG 3  and the first rotary element S 4  of the fourth planetary gear device PG 4 . The seventh rotary shaft RS 7  is the third rotary element R 3  of the third planetary gear device PG 3 . The eighth rotary shaft RS 8  is the output shaft OUT directly connected to the second rotary element C 4  of the fourth planetary gear device PG 4 . 
     In addition, from among the six shifting elements, the first clutch CL 1  is disposed between the first rotary shaft RS 1  and the fifth rotary shaft RS 5 . The second clutch CL 2  is disposed between the first rotary shaft RS 1  and the seventh rotary shaft RS 7 . The third clutch CL 3  is disposed between the fourth rotary shaft RS 4  and the transmission case CS. The fourth clutch CL 4  is disposed between the sixth rotary shaft RS 6  and the transmission case CS. The fifth clutch CL 5  is disposed between the third rotary shaft RS 3  and the transmission case CS. The sixth clutch CL 6  is disposed between the second rotary shaft RS 2  and the third rotary shaft RS 3 . 
     As set forth above, the multi-stage transmission for a vehicle according to the present disclosure includes the four simple planetary gear devices and the six shifting elements that realize the ten forward shifting stages and the one reverse shifting stage according to the operation mode table as illustrated in  FIG. 2 . Since the multi-stage shifting stages of ten shifting stages can be embodied based on a relatively small number of parts and a simple configuration, the multi-stage transmission for a vehicle can contribute to the improved fuel efficiency and quietness of a vehicle, improving the marketability of the vehicle.