Gear train for a 6-speed automatic transmission used in vehicles

Abstract: A gear train for 6-speed automatic transmissions used in vehicles includes a compound planetary gear set, realized through combining first and second planetary gear sets in a radial direction, the second simple planetary gear set being enclosed by a ring gear of the first simple planetary gear set, the ring gear able to act as a sun gear for the second simple planetary gear set, and having five operational elements. A clutch assembly is mounted between at least three of the five operational elements of the compound planetary gear set and an input shaft, and operates to select the operational elements to be input elements. A brake assembly is mounted between at least three of the five operational elements of the compound planetary gear set and a transmission housing, and operates to select the operational elements to be reaction elements.

Description: The present invention relates to a gear train for a 6-speed automatic transmission used in vehicles. More particularly, the invention relates to a gear train for a 6-speed automatic transmission utilizing a compound planetary gear set consisting of planetary gear sets combined radially, the automatic transmission thereby having a short length and a simple construction. Generally, automatic transmission systems for vehicles are provided with a transmission control unit which automatically controls shift ratios according to changes in a running condition of the vehicle. The typical transmission control unit controls a plurality of friction elements provided in a gear train to either operative or inoperative states to select one of the three essential elements of the planetary gear set (a sun gear, a ring gear and a planetary carrier) to be an input element, one to be a reaction element, and one to be an output element, thereby controlling an output number of revolutions. There are different kinds of compound planetary gear systems used in automatic transmission systems including a Ravigneaux-type, a Simpson type, and a 2 Simpson-type compound planetary gear system. Also, the above compound planetary gear systems, so as to allow for use as a shifting means for vehicles, have a structure in which planetary carriers of a first simple planetary gear set are connected to a planetary carrier of a second simple planetary gear set, a structure where the planetary and ring gear are connected through the sun gear, or a structure in which the planetary carriers of the first simple planetary gear set and a ring gear of the second planetary gear set are directly connected to each other, namely, a structure wherein two planetary gear sets are connected in a direction of an axle. However, in the typical automatic transmission, as a length of the system in the direction of the axle is increased, mounting becomes difficult, especially when applying the automatic transmission of a front-wheel-drive vehicle in which the engine is mounted in a transverse direction, and, as a result, much time and effort must go into shortening the automatic transmission in the designing process. Further, when the output power of a large output power engine is not sufficiently utilized, the typical automatic transmission has a poor fuel consumption ratio, power efficiency, and driving performance. Therefore, to efficiently use the engine power, increasing the shift ratio has been proposed. However, in the typical automatic transmission, as only one input element should be selected, at least two planetary gear sets must be provided, thereby increasing costs for manufacturing and complicating the construction. US-A-4 229 996 discloses a gear train for an automatic transmission according to the preamble of claim 1, comprising a compound planetary gear set having five operational elements, a clutch assembly, and a brake assembly mounted between two of the five operational elements of the compound planetary gear set and a transmission housing. The present invention has been made in an effort to solve the above problems. It is an object of the present invention to provide a gear train for a 6-speed automatic transmission used in vehicles which, by utilizing a compound planetary gear set consisting of planetary gear sets combined radially, the automatic transmission has a short length and a simple construction, and by increasing shift ranges, output of the engine can be more efficiently used than in the prior art. To achieve the above object, the present invention provides a gear train for a 6-speed automatic transmission used in a vehicle. A compound planetary gear set is realized through combining first and second planetary gear sets in a radial direction, the second simple planetary gear set being positioned around a ring gear of the first simple planetary gear set, the ring gear able to act as a sun gear for the second simple planetary gear set, and having five operational elements. A clutch assembly, mounted between at least three of the five operational elements of the compound planetary gear set and an input shaft, operates such that it selects the operational elements to be input elements. A brake assembly, mounted between at least three of the five operational elements of the compound planetary gear set and a transmission housing, operates such that it selects the operational elements to be reaction elements. According to another feature of the present invention, the clutch assembly includes: a first clutch interposed between a sun gear of the first simple planetary gear set and the input shaft; a second clutch interposed between the ring of the first simple planetary gear set and the input shaft; and a third clutch interposed between a planetary carrier of the second simple planetary gear set and the input shaft. According to still another feature of the present invention, the clutch assembly includes: a first clutch interposed between the ring gear of the second simple planetary gear set and the input shaft; a second clutch interposed between the ring gear of the first simple planetary gear set and the input shaft; and a third clutch interposed between a planetary carrier of the first simple planetary gear set and the input shaft. According to still yet another feature of the present invention, the clutch assembly for transmitting engine power to the compound planetary gear set includes: a first clutch interposed between the sun gear of the first simple planetary gear set and the input shaft; a second clutch interposed between the planetary carrier of the first simple planetary gear set and the input shaft; and a third clutch interposed between the ring gear of the first simple planetary gear set and the input shaft. According to still yet another feature of the present invention, the clutch assembly includes: a first clutch interposed between the ring gear of the second simple planetary gear set and the input shaft; a second clutch interposed between the planetary carrier of the second simple planetary gear set and the input shaft; and a third clutch interposed between the ring gear of the first simple planetary gear set and the input shaft. According to still yet another feature of the present invention, the brake assembly includes: a first brake interposed between the ring gear of the first simple planetary gear set and a transmission housing; a second brake interposed between the planetary carrier of the second simple planetary gear set and the transmission housing; and a third brake interposed between the ring gear of the second simple planetary gear set and the transmission housing. According to still yet another feature of the present invention, the brake assembly includes: a first brake interposed between the ring gear of the first simple planetary gear set and the transmission housing; a second brake interposed between the planetary carrier of the first simple planetary gear set and the transmission housing; and a third brake interposed between the sun gear of the first simple planetary gear set and the transmission housing. According to still yet another feature of the present invention, the brake assembly includes: a first brake interposed between the ring gear of the second simple planetary gear set and the transmission housing; a second brake interposed between the sun gear of the first simple planetary gear set and the transmission housing; a third brake interposed between the planetary carrier of the first simple planetary gear set and the transmission housing; and a fourth brake interposed between the ring gear of the first simple planetary gear set and the transmission housing. According to still yet another feature of the present invention, the brake assembly includes: a first brake interposed between the sun gear of the first simple planetary gear set and the transmission housing; a second brake interposed between the ring gear of the second simple planetary gear set and the transmission housing; a third brake interposed between the planetary carrier of the second simple planetary gear set and the transmission housing; and a fourth brake interposed between the ring gear of the first simple planetary gear set and the transmission housing. According to still yet another feature of the present invention, multi-plate clutches are used for the clutches forming the clutch assembly, and band brakes are used for the brakes forming the brake assembly. According to still yet another feature of the present invention, the clutch assembly is comprised of a plurality of clutches which are disposed between the sun gear and the ring gear of the first simple planetary gear set, and the planetary carrier of the second simple planetary gear set, and the input shaft, respectively, such that they can selectively act as input elements; and the brake assembly is comprised of a plurality of brakes which are disposed between the ring gear of the first simple planetary gear set, the planetary carrier and the ring gear of the second simple planetary gear set, and the transmission housing, respectively, such that they can selectively act as reaction elements. According to still yet another feature of the present invention, the clutch assembly is comprised of a plurality of clutches which are disposed between the planetary carrier and the ring gear of the first simple planetary gear set, and the ring gear of the second simple planetary gear set, and the input shaft, respectively, such that they can selectively act as input elements; and the brake assembly is comprised of a plurality of brakes which are disposed between the ring gear, the planetary carrier and the sun gear of the first simple planetary gear set, and the transmission housing, respectively, such that they can selectively act as reaction elements. According to still yet another feature of the present invention, the clutch assembly is comprised of a plurality of clutches which are disposed between the sun gear, the planetary carrier and the ring gear of the first simple planetary gear set, and the input shaft, respectively, such that they can selectively act as input elements; and the brake assembly is comprised of a plurality of brakes which are disposed between the sun gear, the planetary carrier and the ring gear of the first simple planetary gear set, and the transmission housing, respectively, such that they can selectively act as reaction elements. According to still yet another feature of the present invention, the clutch assembly is comprised of a plurality of clutches which are disposed between the ring gear of the first simple planetary gear set, and the planetary carrier and the ring gear of the second simple planetary gear set, and the input shaft, respectively, such that they can selectively act as input elements; and the brake assembly is comprised of a plurality of brakes which are disposed between the sun gear and the ring gear of the first simple planetary gear set, and the ring gear and the planetary carrier of the second simple planetary gear set, and the transmission housing, respectively, such that they can selectively act as reaction elements. 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 schematic diagram of a gear train according to a first embodiment of the present invention; FIG. 2 is an operational chart of friction elements in each shift range according to a first embodiment of the present invention; FIG. 3 is a view for explaining an operation of the first embodiment of the present invention through a lever analogy method; FIG. 4 is a schematic diagram of a gear train according to a second embodiment of the present invention; FIG. 5 is a schematic diagram of a gear train according to a third embodiment of the present invention; FIG. 6 is an operational chart of friction elements in each shift range according to a third embodiment of the present invention; and FIG. 7 is a schematic diagram of a gear train according to a fourth embodiment of the present invention. Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Referring to FIG. 1, power generated from an engine 2 passes through a torque converter 4 to realize torque conversion, and is then inputted to a compound planetary gear set 6, thereby accomplishing shifting. In the above, by a selective operation of a clutch assembly including a plurality of clutches 8, 10 and 12, the compound planetary gear set 6 receives an input through at least one element thereof, and by a selective operation of a brake assembly including a plurality of brakes 14, 16 and 18, at least one element thereof acts as a reaction element in all drive ranges excluding a forward fourth speed range. The torque converter 4 for converting the torque generated from the engine 2 includes a pump impeller 18 directly connected to a crankshaft of the engine 2 and rotating, a turbine runner 22 mounted opposing the pump impeller 18, thereby rotating together therewith through gushing oil, and a stator 24 disposed between the pump impeller 20 and the turbine runner 22 and changing a flow of oil, thereby increasing a rotary power of the pump impeller 20. Accordingly, when the engine rotates, the oil charged in the torque converter 4 gushes through the pump impeller 20 and is supplied to the turbine runner 22, thereby driving the turbine runner 22, and then flows into the stator 24. Further, the oil flowed into the stator 24 is redirected repeatedly to the pump impeller 20. Here, a difference appears in the rotary power of the turbine runner 22 given to the stator 24 by a rotation of the stator 24 and that of the pump impeller 20 thereby accomplishing torque conversion. Also, the compound planetary gear set 6 receiving power from the torque converter 4 is aligned on a rear side of an input shaft 26 connected to the turbine runner 22 of the torque converter 4. The compound planetary gear set 6 is constituted by combining first and second simple planetary gear sets 28 and 30 in a radial direction. The second simple planetary gear set 30 is enclosed by a ring gear 32 of the first simple planetary gear set 28, and this ring gear 32 is able to act as a sun gear for the second simple planetary gear set 30. Therefore, the compound planetary gear set 6 possesses five operating elements comprising the sun gear 34, the planetary carrier 36 and ring gear of the first simple planetary gear set 28, and the planetary carrier 38 and ring gear 40 of the second simple planetary gear set 30. Operating as a clutch assembly for transmitting engine power, the first clutch 8 is interposed between the input shaft 26 and the sun gear 34 of the first simple planetary gear set 28, the second clutch 10 is interposed between the input shaft 26 and the ring gear 32 of the first simple planetary gear set 28, and the third clutch 12 is interposed between the input shaft 26 and the planetary carrier 38 of the second simple planetary gear set 30. As a result of the above, through the selective operation of the clutches 8, 10 and 12, elements connected to these clutches are selectively, or two of them are simultaneously, made to operate as input elements. Also, forming the brake assembly, the first brake 14 is interposed between the ring gear 32 of the first simple planetary gear set 28 and a transmission housing 42, the second brake 16 is interposed between the planetary carrier 38 of the second simple planetary gear set 30 and the transmission housing 42, and the third brake 18 is interposed between the ring gear 40 of the second simple planetary gear set 30 and the transmission housing 42 to allow the above elements to selectively operate as reaction elements. An output gear 44 is disposed at an end portion of the planetary carrier 36 of the first simple planetary gear set 28 to allow it to operate as an output element. Multi-plate clutches can be used for the first, second and third clutches 8, 10 and 12 forming the clutch assembly, and band brakes can be used for the first, second and third brakes 14, 16 and 18 forming the brake assembly. As shown in the friction element operational chart of FIG. 2, in the gear train of the present invention structured as above, friction elements are operated to realize shifting. The shift process will be explained hereinafter using the operation chart of FIG. 2 and the lever analogy diagram of FIG. 3. In the lever analogy shown in FIG. 3, a first node N1 indicates the sun gear 34 of the first simple planetary gear set 28, a second node N2 indicates the planetary carrier 36 of the first simple planetary gear set 28, a third node N3 indicates the ring gear 32 of the first simple planetary gear set 28, a fourth node N4 indicates the planetary carrier 38 of the second simple planetary gear set 30, and a fifth node N5 indicates the ring gear 40 of the second simple planetary gear set 30. In the operational process of a forward first speed, the first clutch 8 and the first brake 14 are controlled to operate. When this happens, the power of the input shaft 26 which is rotated through the driving force received from the engine 2 makes the sun gear 34 of the first simple planetary gear set 28 operate as an input element through the operation of the first clutch 8, and, at the same time, the ring gear 32 of the first simple planetary gear set 28 acts as a reaction element through the operation of the first brake 14. Through the above operation, first speed shifting is realized, and through the planetary carrier 36 of the first simple planetary gear set 28, output is realized. Referring to FIG. 3, with regard to the shift process of a first speed, a line connecting the second node N2 to a point on a line L1 connecting a first input speed line S1, inputted at the first node N1, to the third node N3, acting as the reaction element, becomes a first speed output line D1. Therefore, an output number of rotations becomes much smaller than an input number of rotations, and a reduction in speed is realized through a first speed shift ratio. In the above first speed state, if vehicle speed and throttle opening are increased, a transmission control unit disengages the first brake 14 and operates the second brake 16. As a result, starting from the input state as in the first speed, by the operation of the second brake 16, the planetary carrier 38 of the second simple planetary gear set 30 operates as a reaction element, and second speed shifting is realized. Referring to FIG. 3, with regard to the shift process of a second speed, a line connecting the second node N2 to a point on a line L2 connecting a first input speed line S1, inputted at the first node N1, to the fourth node N4, acting as the reaction element, becomes a second speed output line D2, realizing output having a higher speed than the first speed. In the above second speed state, if vehicle speed and throttle opening are increased, the transmission control unit disengages the second brake 16 and operates the third brake 18. As a result, starting from the input state of the second speed, by the operation of the third brake 18, the ring gear 40 of the second simple planetary gear set 30 operates as a reaction element, and third speed shifting is realized. Referring to FIG. 3, with regard to the shift process of a third speed, a line connecting the second node N2 to a point on a line L3 connecting a first input speed line S1, inputted at the first node N1, to the fifth node N5, acting as the reaction element, becomes a third speed output line D3, realizing output having a higher speed than the second speed. In the above third speed state, if vehicle speed and throttle opening are increased, the transmission control unit disengages the third brake 18 and operates the second clutch 10. As a result, starting from the input state of the third speed, by the operation of the second clutch 10, the ring gear 32 of the first simple planetary gear set 28 operates as an input element. Accordingly, second input is realized, and as there comes to be two input elements, fourth speed shifting is realized. Referring to FIG. 3, with regard to the shift process of a fourth speed, a line connecting the second node N2 acting as an output element to a point on a line L4 connecting a first input speed line S1, inputted at the first node N1, to the second speed line S2 of the third node N3, acting as an input element, becomes a fourth speed output line D4. In the above fourth speed state, if vehicle speed and throttle opening are increased, the transmission control unit disengages the first clutch 8, operating in the fourth speed, and operates the third brake 18. As a result, starting from the input state through the ring gear 32 of the first simple planetary gear set 28, by the operation of the third brake 18, as the ring gear 40 of the second simple planetary gear set 30 operates as a reaction element, fifth speed shifting is realized. Referring to FIG. 3, with regard to the shift process of a fifth speed, a line connecting the second node N2, acting as an output element, to a point on a line L5 connecting a second input speed line S2 of the third node N3 to the fifth node N5, acting as a reaction element, becomes a fifth speed output line D5. Namely, in the above fifth speed, an overdrive state occurs wherein output speed is faster than input speed. In the above fifth speed state, if vehicle speed and throttle opening are increased, the transmission control unit disengages the third brake 18, operating in the fifth speed, and operates the second brake 16. As a result, starting from the input state through the ring gear 32 of the first simple planetary gear set 28, by the operation of the second brake 16, as the planetary carrier 38 of the second simple planetary gear set 30 operates as a reaction element, sixth speed shifting is realized. Referring to FIG. 3, with regard to the shift process of a sixth speed, a line connecting the second node N2, acting as an output element, to a point on a line L6 connecting the second input speed line S2 of the third node N3 to the fourth node N4, acting as a reaction element, becomes a sixth speed output line D6. Also, in the above sixth speed, an overdrive state occurs wherein output speed is faster than input speed. If a driver changes a selector lever to a reverse R range, the third clutch 12 and the first brake 14 are controlled to be engaged. When the above happens, input is realized through the planetary carrier 38 of the second simple planetary gear set 30 through the operation of the third clutch 12, and, through the operation of the first brake 14, the ring gear 32 of the first simple planetary gear set 28 comes to operate as a reaction element to realize reverse R shifting. Also, output is realized through the planetary carrier 36 of the first simple planetary gear set 28. Referring to FIG. 3, a line connecting the second node N2 to a point on a line L7 connected to the third node N3, acting as reaction element, becomes a reverse speed output line R. Referring now to FIG. 4, there is shown a schematic diagram of a gear train according to a second embodiment of the present invention. In the second embodiment, clutches forming the clutch assembly for transmitting the power of the engine 2 to the compound planetary gear set 6 is differently connected to brakes forming the brake assembly than in the first embodiment. Namely, the first clutch 8 is interposed between the input shaft 26 and the ring gear 40 of the second simple planetary gear set 30, the second clutch 10 is interposed between the input shaft 26 and the ring gear 32 of the first simple planetary gear set 28, and the third clutch 12 is interposed between the input shaft 26 and the planetary carrier 36 of the first simple planetary gear set 28. As a result, through the selective operation of the clutches 8, 10 and 12, one or two of the elements connected to them are made to operate as input elements. In addition, forming the brake assembly, the first brake 14 is interposed between the ring gear 32 of the first simple planetary gear set 28 and the transmission housing 42, the second brake 16 is interposed between the planetary carrier 36 of the first simple planetary gear set 28 and the transmission housing 42, and the third brake 18 is interposed between the sun gear 34 of the first simple planetary gear set 28 and the transmission housing 42 to allow the above elements to selectively operate as reaction elements, and the output gear 44 is disposed at an end portion of the planetary carrier 38 of the second simple planetary gear set 30 to allow it to operate as an output element. In the gear train of the second embodiment structured as above, the clutches and the brakes are operated, as shown in the operational chart of FIG. 2, to realize shifting. In the forward first speed, the first clutch 8 and the first brake 14 are controlled to operate. When this happens, the power of the input shaft 26 which rotates by the engine 2 makes the ring gear 40 of the second planetary gear set 30 operate as an input element, and, at the same time, the ring gear 32 of the first simple planetary gear set 28 to act as a reaction element by the operation of the first brake 14. Through the above operations, first speed shifting is realized, and through the planetary carrier 38 of the second simple planetary gear set 30, output is realized. If vehicle speed and throttle opening are increased in the above first speed state, the transmission control unit disengages the first brake 14 and operates the second brake 16. As in the first speed input state, reaction elements are realized by the operation of the second brake 16 through the planetary carrier 36 of the first simple planetary gear set 28, and second speed shifting is realized. If vehicle speed and throttle opening are increased in the above second speed state, the transmission control unit disengages the second brake 16 and operates the third brake 18. As in the second speed input state, reaction elements are realized by the operation of the third brake 18 through the sun gear 34 of the first simple planetary gear set 28, and the third speed shifting is realized. If vehicle speed and throttle opening are increased in the above third speed state, the transmission control unit disengages the third brake 18 and operates the second clutch 10. When the above operations are performed, input elements are realized by the operation of the second clutch 10 in the third speed input state through the ring gear 32 of the first simple planetary gear set 28 whereby second input is realized, and as there comes to be two input elements, fourth speed shifting is realized. If vehicle speed and throttle opening are increased in the above fourth speed state, the transmission control unit disengages the first clutch 8, operating in the fourth speed, and controls the third brake 18 to operate. When the above operations are performed, reaction elements are realized by the operation of the third brake 18, in the input state through the ring gear 32 of the first simple planetary gear set 28, and through the sun gear 34 of the first simple planetary gear set 28, thereby realizing fifth speed shifting. In the fifth speed, an overdrive state is realized in which output speed is faster that input speed. If vehicle speed and throttle opening are increased in the above fifth speed state, the transmission control unit disengages the third brake 18, operating in the fifth speed, and controls the second brake 16 to operate. When the above is performed, by the operation of the second brake in the input state through the ring gear 32 of the first simple planetary gear set 28, the planetary carrier 36 of the first simple planetary gear set 28 operates as a reaction element thereby realizing sixth speed shifting. An overdrive state occurs in the above sixth speed as in the fifth speed. Also, if the driver changes the selector lever to a reverse R range, the transmission control unit controls the third clutch 12 and the first brake 14 to operate. When the above is performed, input is realized through the planetary carrier 36 of the first simple planetary gear set 28 by the operation of the third clutch 12, and, at the same time, by the operation of the first brake 14, the ring gear 32 of the first simple planetary gear set 28 operates as a reaction element to realize reverse shifting, and output is realized through the planetary carrier 38 of the second simple planetary gear set 30. Referring to FIG. 5, there is shown a schematic diagram of a gear train according to a third embodiment of the present invention. In the third embodiment, clutches forming the clutch assembly for transmitting the power of the engine 2 to the compound planetary gear set 6 is differently connected to brakes forming the brake assembly than in the first embodiment, and, at the same time, one brake is additionally disposed therein. Namely, the first clutch 8, forming the clutch assembly for transmitting the power of the engine 2 to the compound planetary gear set 6, is interposed between the input shaft 26 and the sun gear 34 of the first simple planetary gear set 28, the second clutch 10 is interposed between the input shaft 26 and the planetary carrier 36 of the first simple planetary gear set 28, and the third clutch 12 is interposed between the input shaft 26 and the ring gear 32 of the first simple planetary gear set 28. As a result, through the selective operation of the clutches 8, 10 and 12, one or two of the elements connected to the clutches are made to operate as input elements. In addition, forming the brake assembly, the first brake 14 is interposed between the ring gear 40 of the second simple planetary gear set 30 and the transmission housing 42, the second brake 16 is interposed between the sun gear 34 of the first simple planetary gear set 28, the third brake 18 is interposed between the planetary carrier 36 of the first simple planetary gear set 28, and the fourth brake 46 is interposed between the ring gear 32 of the first simple planetary gear set 28 to allow the above elements to selectively operate as reaction elements, and the output gear 44 is disposed at an end portion of the planetary carrier 38 of the second simple planetary gear set 30 to allow it to operate as an output element. In the gear train of the third embodiment structured as above, the friction elements are operated, as shown in the operational chart of FIG. 6, to realize shifting. In the forward first speed, the first clutch 8 and the first brake 14 are controlled to be operated. When this is done, the power of the input shaft 26 which rotates by the engine 2 makes the sun gear 34 of the first simple planetary gear set 28 operate as an input element by the operation of the first clutch 8, and, at the same time, the ring gear 40 of the second simple planetary gear set 30 to act as a reaction element by the operation of the first brake 14. Through the above operations, first speed shifting is realized, and through the planetary carrier 38 of the second planetary gear set 30, output is realized. If vehicle speed and throttle opening are increased in the above first speed state, the transmission control unit disengages the first clutch 8 and operates the second clutch 10. When this is done, an input element is changed to the planetary carrier 36 of the first simple planetary gear set 28 according to the operation of the second clutch 10, and second speed shifting is realized. If vehicle speed and throttle opening are increased in the above second speed state, the transmission control unit disengages the second clutch 10 and operates the third clutch 12. When this is done, an input element is changed to the ring gear 32 of the first simple planetary gear set 28 according to the operation of the third clutch 12, and a third speed shifting is realized. In the above third speed state, if vehicle speed and throttle opening are further increased, the transmission control unit disengages the first brake 14 and operates the first clutch 8. When the above is done, reaction force is released in the third speed input state, and the sun gear 34 of the first simple planetary gear set 28 operates as an input element, whereby second input is realized, and as there comes to be two input elements, fourth speed shifting is realized. If vehicle speed and throttle opening are further increased in the above fourth speed state, the transmission control unit disengages the first clutch 8, operating in the fourth speed, and controls the second brake 16 to operate. When the above is performed, input is realized through the ring gear 32 of the first simple planetary gear set 28, and by the operation of the second brake 16, the sun gear 34 of the first simple planetary gear set 28 operates as a reaction element to realize fifth speed shifting. Also, in the above fifth speed, an overdrive state occurs wherein output speed is faster than input speed. If vehicle speed and throttle opening are further increased in the above fifth speed state, the transmission control unit disengages the second brake 16, operating in the fifth speed, and controls the third brake 18 to operate. When the above is performed, by the operation of the third brake 18 in the input state through the ring gear 32 of the first simple planetary gear set 28, the planetary carrier 36 of the first simple planetary gear set 28 operates as a reaction element thereby realizing sixth speed shifting. An overdrive state occurs in the above sixth speed as in the fifth speed. Also, if the driver changes the selector lever to a reverse R range, the transmission control unit controls the first clutch 8 and the fourth brake 46 to operate. When the above is performed, input is realized through the sun gear 34 of the first simple planetary gear set 28 by the operation of the first clutch 8, and, at the same time, by the operation of the fourth brake 46, the ring gear 32 of the first simple planetary gear set 28 operates as a reaction element to realize reverse shifting, and output is realized through the planetary carrier 38 of the second simple planetary gear set 30. Referring to FIG. 7, there is shown a schematic diagram of a gear train according to a fourth embodiment of the present invention. Clutches forming the clutch assembly are differently connected to brakes forming the brake assembly than in the third embodiment. Namely, the first clutch 8 of the clutch assembly for transmitting the power of the engine 2 to the compound planetary gear set 6, is interposed between the input shaft 26 and the ring gear 40 of the second simple planetary gear set 30, the second clutch 10 is interposed between the input shaft 26 and the planetary carrier 38 of the second simple planetary gear set 30, and the third clutch 12 is interposed between the input shaft 26 and the ring gear 32 of the first simple planetary gear set 28. As a result, through the selective operation of the clutches 8, 10 and 12, one or two of the elements connected to the clutches are made to operate as input elements. In addition, forming the brake assembly, the first brake 14 is interposed between the sun gear 34 of the first simple planetary gear set 28 and the transmission housing 42, the second brake 16 is interposed between the ring gear 40 of the second simple planetary gear set 30, the third brake 18 is interposed between the planetary carrier 38 of the second simple planetary gear set 30, and the fourth brake 46 is interposed between the ring gear 32 of the first simple planetary gear set 28 to allow the above elements to selectively operate as reaction elements, and the output gear 44 is disposed at an end portion of the planetary carrier 36 of the first simple planetary gear set 28 to allow it to operate as an output element. In the gear train of the fourth embodiment structured as in the above, the friction elements are operated, as shown in the operational chart of FIG. 6, to realize shifting. In the forward first speed, the first clutch 8 and the first brake 14 are controlled to be operated. When this is done, the power of the input shaft 26 which rotates by the engine 2 makes the ring gear 40 of the second simple planetary gear set 30 operate as an input element by the operation of the first clutch 8, and, at the same time, the sun gear 34 of the first simple planetary gear set 28 to act as a reaction element by the operation of the first brake 14. Through the above operations, first speed shifting is realized, and through the planetary carrier 36 of the first simple planetary gear set 28, output is realized. If vehicle speed and throttle opening are increased in the above first speed state, the transmission control unit disengages the first clutch 8 and operates the second clutch 10. When this is done, an input element is changed to the planetary carrier 38 of the second simple planetary gear set 30 according to the operation of the second clutch 10, and second speed shifting is realized. If vehicle speed and throttle opening are increased in the above second speed state, the transmission control unit disengages the second clutch 10 and operates the third clutch 12. When this is done, an input element is changed to the ring gear 32 of the first simple planetary gear set 28 according to the operation of the third clutch 12, and third speed shifting is realized. In the above third speed state, if vehicle speed and throttle opening are increased, the transmission control unit disengages the first brake 14 and operates the first clutch 8. When the above is done, reaction force is released in the third speed input state, and the ring gear 40 of the second simple planetary gear set 30 operates as an input element, whereby second input is realized, and as there comes to be two input elements, fourth speed shifting is realized. If vehicle speed and throttle opening are further increased in the above fourth speed state, the transmission control unit disengages the first clutch 8, operating in the fourth speed, and controls the second brake 16 to operate. When the above is performed, input is realized through the ring gear 32 of the first simple planetary gear set 28, and by the operation of the second brake 16, the ring gear 40 of the second simple planetary gear set 30 operates as a reaction element to realize fifth speed shifting. In the above fifth speed, an overdrive state occurs wherein output speed is faster than input speed. If vehicle speed and throttle opening are further increased in the above fifth speed state, the transmission control unit disengages the second brake 16, operating in the fifth speed, and controls the third brake 18 to operate. When the above is performed, input is realized through the ring gear 32 of the first simple planetary gear set 28, and by the operation of the third brake 18, the planetary carrier 38 of the second simple planetary gear set 30 operates as a reaction element to realize sixth speed shifting. If a driver changes a selector lever to a reverse R range, the transmission control unit controls the first clutch 8 and the fourth brake 46 to operate. When the above happens, input is realized through the ring gear 40 of the second simple planetary gear set 30 by the operation of the first clutch 8, and, at the same time, by the operation of the fourth brake 46, the ring gear 32 of the first simple planetary gear set 28 comes to operate as a reaction element to realize reverse R shifting. Also, output is realized through the planetary carrier 36 of the first simple planetary gear set 28. In the above second to fourth embodiments, as in the first embodiment, multi-plate clutches are used for the first to third clutches 8, 10 and 12 forming the clutch assembly, and band brakes are used for the first to fourth brakes 14, 16, 18 and 46 forming the brake assembly. In the gear train of the present invention structured as above, by utilizing a compound planetary gear set consisting of planetary gear sets combine radially, it is possible to design an automatic transmission having a short length and a simple construction. Further, by increasing shift ranges through 6 forward drive ranges and 1 rearward range, output of the engine can be more efficiently used than in the prior art. Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the scope of the present invention, as defined in the appended claims.

Claims: A gear train for an automatic transmission used in a vehicle, comprising: a compound planetary gear set (6), realized through combining first and second simple planetary gear sets (28, 30) in a radial direction, the second simple planetary gear set (30) being positioned around a ring gear (32) of the first simple planetary gear set (28), the ring gear (32) acting as a sun gear for the second simple planetary gear set (30), and having five operational elements (32, 34, 36, 38, 40); a clutch assembly (8, 10, 12), mounted between at least three of the five operational elements of the compound planetary gear set (6) and an input shaft (26), and operating to select the operational elements to be input elements; and characterized by : a brake assembly (14, 16, 18), mounted between at least three of the five operational elements of the compound planetary gear set (6) and a transmission housing (42), and operating to select the operational elements to be reaction elements, such that a 6-speed automatic transmission is realized. The gear train of claim 1, wherein said clutch assembly includes: a first clutch (8) interposed between a sun gear (34) of the first simple planetary gear set (28) and the input shaft (26); a second clutch (10) interposed between the ring gear (32) of the first simple planetary gear set (28) and the input shaft (26); and a third clutch (12) interposed between a planetary carrier (38) of the second simple planetary gear set (30) and the input shaft (26). The gear train of claim 1, wherein said clutch assembly includes: a first clutch (8) interposed between the ring gear (40) of the second simple planetary gear set (30) and the input shaft (26); a second clutch (10) interposed between the ring gear (32) of the first simple planetary gear set (28) and the input shaft (26); and a third clutch (12) interposed between a planetary carrier (36) of the first simple planetary gear set (28) and the input shaft (26). The gear train of claim 1, wherein said clutch assembly for transmitting engine power to the compound planetary gear set includes: a first clutch (8) interposed between the sun gear (34) of the first simple gear set (28) and the input shaft (26); a second clutch (10) interposed between the planetary carrier (36) of the first simple planetary gear set (28) and the input shaft (26); and a third clutch (12) interposed between the ring gear (32) of the first simple planetary gear set (28) and the input shaft (26). The gear train of claim 1, wherein said clutch assembly includes: a first clutch (8) interposed between the ring gear (40) of the second simple planetary gear set (30) and the input shaft (26) ; a second clutch (10) interposed between the planetary carrier (38) of the second simple planetary gear set (30) and the input shaft (26); and a third clutch (12) interposed between the ring gear (32) of the first simple planetary gear set (28) and the input shaft (26). The gear train of claim 1, wherein said brake assembly includes: a first brake (14) interposed between the ring gear (32) of the first simple planetary gear set (28) and a transmission housing (42); a second brake (16) interposed between the planetary carrier (38) of the second simple planetary gear set (30) and the transmission housing (42); and a third brake (18) interposed between the ring gear (40) of the second simple planetary gear set (30) and the transmission housing (42). The gear train of claim 1, wherein said brake assembly includes: a first brake (14) interposed between the ring gear (32) of the first simple planetary gear set (28) and the transmission housing (42); a second brake (16) interposed between the planetary carrier (36) of the first simple planetary gear set (28) and the transmission housing (42); and a third brake (18) interposed between the sun gear (34) of the first simple planetary gear set (28) and the transmission housing (42). The gear train of claim 1, wherein said brake assembly includes: a first brake (14) interposed between the ring gear (40) of the second simple planetary gear set (30) and the transmission housing (42); a second brake (16) interposed between the sun gear (34) of the first simple planetary gear set (28) and the transmission housing (42); a third brake (18) interposed between the planetary carrier (36) of the first simple planetary gear set (28) and the transmission housing (42); and a fourth brake (46) interposed between the ring gear (32) of the first simple planetary gear set (28) and the transmission housing (42). The gear train of claim 1, wherein said brake assembly includes: a first brake (14) interposed between the sun gear (34) of the first simple planetary gear set (28) and the transmission housing (42); a second brake (16) interposed between the ring gear (40) of the second simple planetary gear set (30) and the transmission housing (42); a third brake (18) interposed between the planetary carrier (38) of the second simple planetary gear set (30) and the transmission housing (42); and a fourth brake (46) interposed between the ring gear (32) of the first simple planetary gear set (28) and the transmission housing (42). The gear train of claim 1, wherein multi-plate clutches are used for the clutches forming said clutch assembly, and band brakes are used for the brakes forming said brake assembly. The gear train of claim 1, wherein said clutch assembly comprises a plurality of clutches disposed between the sun gear (34) and the ring gear (32) of the first simple planetary gear set (28), and the planetary carrier (38) of the second simple planetary gear set (30), and the input shaft (26), respectively, such that they can selectively act as input elements; and said brake assembly comprises a plurality of brakes disposed between the ring gear (32) of the first simple planetary gear set (28), the planetary carrier (38) and the ring gear (40) of the second simple planetary gear set (30), and the transmission housing (42), respectively, such that they can selectively act as reaction elements. The gear train of claim 1, wherein said clutch assembly comprises a plurality of clutches which are disposed between the planetary carrier (36) and the ring gear (32) of the first simple planetary gear set (28), and the ring gear (40) of the second simple planetary gear set (30), and the input shaft (26), respectively, such that they can selectively act as input elements; and said brake assembly comprises a plurality of brakes which are disposed between the ring gear (32), the planetary carrier (36) and the sun gear (34) of the first simple planetary gear set (28), and the transmission housing (42), respectively, such that they can selectively act as reaction elements. The gear train of claim 1, wherein said clutch assembly comprises a plurality of clutches which are disposed between the sun gear (34), the planetary carrier (36) and the ring gear (32) of the first simple planetary gear set (28), and the input shaft (26), respectively, such that they can selectively act as input elements; and said brake assembly comprises a plurality of brakes which are disposed between the sun gear (34), the planetary carrier (36) and the ring gear (32) of the first simple planetary gear set (28), and the transmission housing (42), respectively, such that they can selectively act as reaction elements. The gear train of claim 1, wherein said clutch assembly comprises a plurality of clutches which are disposed between the ring gear (32) of the first simple planetary gear set (28), and the planetary carrier (38) and the ring gear (40) of the second simple planetary gear set (30), and the input shaft (26), respectively, such that they can selectively act as input elements; and said brake assembly comprises a plurality of brakes which are disposed between the sun gear (34) and the ring gear (32) of the first simple planetary gear set (28), and the ring gear (40) and the planetary carrier (38) of the second simple planetary gear set (30), and the transmission housing (42), respectively, such that they can selectively act as reaction elements.

Inventors: PARK DONG HOON, PARK, DONG HOON
Applicants: HYUNDAI MOTOR CO LTD, HYUNDAI MOTOR COMPANY
Application year: 1997
Main classification: F16H3
IPC codes: F16H3