Abstract: A planetary gear train of an automatic transmission for a vehicle may include an input shaft to receive an engine torque, an output shaft to output a shifted torque, a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element, a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element, a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element, a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element, and six control elements for selectively interconnecting the rotation elements and a transmission housing.

Abstract: Nine or more forward speeds and at least one reverse speed are achieved by a planetary gear train of an automatic transmission for a vehicle including an input shaft, an output shaft, four planetary gear sets respectively having three rotation elements, and six control elements for selectively interconnecting the rotation elements and a transmission housing.

Abstract: Nine or more forward speeds and at least one reverse speed are achieved by a planetary gear train of an automatic transmission for a vehicle including an input shaft, an output shaft, four planetary gear sets respectively having three rotation elements, and six control elements for selectively interconnecting the rotation elements and a transmission housing.

Abstract: A planetary gear train of an automatic transmission for a vehicle may include an input shaft to receive torque of an engine, an output shaft to output changed torque of the engine, a first planetary gear set including first, second, and third rotation elements, a second planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set including seventh, eighth, and ninth rotation elements, and a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements.

Abstract: A hybrid transmission includes a first planetary gear set and a second planetary gear set. The first planetary gear set is constituted of a complex planetary gear train connected to an input element, a motor/generator, and a first clutch, and has four or more rotation elements. The first rotation element of the first planetary gear set is selectively connected to the input element and the first clutch is installed to selectively stop rotation of a third rotation element of the first planetary gear set. The fourth rotation element of the first planetary set is selectively connected to the motor/generator. The second planetary gear set is connected to an output element, and has four or more rotation elements.

Abstract: A method of controlling a DCT (double clutch transmission) of a vehicle to conduct a series of downshifting operations from a preceding gear to a subsequent gear via a current gear in response to deceleration of the vehicle may include slip-controlling, continuously, a clutch which has been in an engaged state in the preceding gear, at least until a shift gear of the subsequent gear is engaged, wherein the slip-controlling includes maintaining the engaged state of the clutch with the current gear.

Abstract: A double clutch powertrain for a vehicle makes smooth starting of the vehicle and smooth gear shifting possible despite using a dry type double clutch and makes regenerative braking and power generation possible when the vehicle decelerates, thus improving the driving characteristics of the vehicle, and enhancing the fuel efficiency of the vehicle.

Abstract: A hybrid transmission includes a first planetary gear set and a second planetary gear set. The first planetary gear set is constituted of a complex planetary gear train connected to an input element, a motor/generator, and a first clutch, and has four or more rotation elements. The first rotation element of the first planetary gear set is selectively connected to the input element and the first clutch is installed to selectively stop rotation of a third rotation element of the first planetary gear set. The fourth rotation element of the first planetary set is selectively connected to the motor/generator. The second planetary gear set is connected to an output element, and has four or more rotation elements.

Abstract: Disclosed herein is a gear train of a multi-step transmission for a vehicle, which can shift gears among nine forward speeds and one reverse speed. The gear train realizes a desired level of multi-step change gear ratios and has a reduced number of sets of planetary gears to reduce the volume and length of the transmission, thus realizing a compact structure, thereby facilitating the installation of the transmission in the vehicle.

Abstract: A gear train apparatus in a multistage transmission may include input and output shafts, a complex planetary gear device concentrically mounted with regard to the output shaft and having four rotary components including one rotary component coupled to the output shaft, first to third pairs of external gears, first to third clutches, a train of external gears, a fourth clutch and first and second brakes.

Abstract: A gear train apparatus in a multistage transmission may include input and output shafts, a complex planetary gear device concentrically mounted with regard to the output shaft and having four rotary components including one rotary component coupled to the output shaft, first to third pairs of external gears, first to third clutches, a train of external gears, a fourth clutch and first and second brakes.

Abstract: Disclosed herein is a gear train of a multi-step transmission for a vehicle, which can shift gears among nine forward speeds and one reverse speed. The gear train realizes a desired level of multi-step change gear ratios and has a reduced number of sets of planetary gears to reduce the volume and length of the transmission, thus realizing a compact structure, thereby facilitating the installation of the transmission in the vehicle.

Abstract: A method of controlling a DCT (double clutch transmission) of a vehicle to conduct a series of downshifting operations from a preceding gear to a subsequent gear via a current gear in response to deceleration of the vehicle may include slip-controlling, continuously, a clutch which has been in an engaged state in the preceding gear, at least until a shift gear of the subsequent gear is engaged, wherein the slip-controlling includes maintaining the engaged state of the clutch with the current gear.

Abstract: An automatic transmission includes six forward speeds and a reverse speed and includes first and second clutches, first, second, and third brakes, and first, second, and third planetary gear sets. An oil pressure control system of the transmission includes a first clutch and second brake controller allowing the first clutch to receive a fastening pressure in fourth, fifth, and sixth speeds, allowing the second brake to receive a fastening pressure in first speed and reverse, and allowing an operation state of the first clutch to be sustained upon operation of the first clutch; a second clutch controller allowing the second clutch to receive a fastening pressure in third and fifth speeds and reverse; a first brake controller allowing the first brake to receive a fastening pressure in second and sixth speeds; and a third brake controller allowing the third brake to receive a fastening pressure in first through fourth speeds.

Abstract: A pressure control system of an automatic transmission includes a control-pressure regulating valve, a path switching valve, and a coupling-pressure regulating valve. The path switching valve selectively outputs a control pressure or a line pressure, so that the coupling-pressure regulating valve regulates a coupling pressure based on the control pressure during gear shifting, and regulates the coupling pressure based on the line pressure after completion of the gear shifting.

Abstract: A hydraulic control system of an automatic transmission that precisely control is operating hydraulic pressure supplied to a frictional element during shifting and can eliminate oil leak under a maximum operating hydraulic pressure. The hydraulic control system controls a hydraulic pressure generated by a hydraulic pump to from an operating hydraulic pressure for a frictional element selectively operating at each shift ratio. A hydraulic line is configured such that the operating hydraulic pressure of the frictional element is controlled by a pressure control valve and a switching valve that are controlled by a solenoid valve. An exhaust hydraulic line of the pressure control valve is connected to an exhaust hydraulic line of the switching valve such that the exhaust hydraulic line of the pressure control valve can be controlled by a switching of the switching valve.

Abstract: Durability and power transmission efficiency are enhanced in a six-speed powertrain of an automatic transmission by a scheme that includes first to fourth planetary gearsets respectively having operational elements of a sun gear, a ring gear, and a carrier, in which the operational elements of the planetary gearsets are wisely interconnected therebetween or with an input shaft or the transmission case directly or via a clutch or a brake.

Abstract: Durability and power transmission efficiency are enhanced in a six-speed powertrain of an automatic transmission by a scheme that includes: a first planetary gear set having operational elements of a first sun gear, a first ring gear, and a first carrier; a second planetary gear set having operational elements of a second sun gear, a second ring gear, and a second carrier; a third planetary gear set having operational elements of a third sun gear, a third ring gear, and a third carrier; an input shaft; at least one output gear; and a transmission case. The first sun gear is fixedly connected to the second sun gear. The second carrier is fixedly connected to the third ring gear. The third sun gear always acts as an input element by being fixedly connected to the input shaft. At lease one operational element of the third carrier and the first ring gear always acts as an output element by being fixedly connected to the at least one output gear.

Abstract: Durability and power transmission efficiency are enhanced in a six-speed powertrain of an automatic transmission by a scheme that includes first to fourth planetary gear sets respectively having operational elements of a sun gear, a ring gear, and a carrier, in which the operational elements of the planetary gear sets are wisely interconnected therebetween or with an input shaft or the transmission case directly or via a clutch or a brake.

Abstract: An automatic transmission includes six forward speeds and a reverse speed and includes first and second clutches, first, second, and third brakes, and first, second, and third planetary gear sets. An oil pressure control system of the transmission includes a first clutch and second brake controller allowing the first clutch to receive a fastening pressure in fourth, fifth, and sixth speeds, allowing the second brake to receive a fastening pressure in first speed and reverse, and allowing an operation state of the first clutch to be sustained upon operation of the first clutch; a second clutch controller allowing the second clutch to receive a fastening pressure in third and fifth speeds and reverse; a first brake controller allowing the first brake to receive a fastening pressure in second and sixth speeds; and a third brake controller allowing the third brake to receive a fastening pressure in first through fourth speeds.