Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive
Reexamination Certificate
1999-10-29
2001-01-23
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
C475S275000, C475S271000, C475S330000, C475S284000, C475S325000
Reexamination Certificate
active
06176802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an automatic transmission that is installed in a vehicle and, more particularly, to arrangement of various components of a speed-change mechanism of a gear train of the transmission.
2. Description of Related Art
Demands for a multi-stage design have been placed on automatic transmissions not only to secure driveability but also to improve fuel consumption, which is indispensable to the conservation of energy. In order to satisfy such demands, the number of clutches and brakes and the number of speed-change elements per speed-change stage of a gear train need to be further reduced. Hence, U.S. Pat. No. 5,106,352 proposes a gear train that employs a planetary gear set composed of a minimum possible number of speed-change elements and establishes six forward speeds and one backward speed by means of three clutches and two brakes for operating the planetary gear set. In the gear train according to the patent, three clutches are used to suitably input an engine output rotation and a decelerated rotation thereof to a planetary gear set composed of four speed-change elements of the transmission as two different rotations, and two brakes are used to control stopping of two speed-change elements. In this manner, the gear train achieves six multi-staged speeds.
The six-speed automatic transmission of the aforementioned related art necessitates, as its feature, two clutches for transmitting an input that has been decelerated through a reduction planetary gear to two different speed-change elements of the planetary gear set respectively. Although this structure makes it possible to obtain favorable gear ratios of six speeds, it is necessary to secure torque capacities of the two clutches and power transmitting members thereof, namely, a high-torque transmission system for the purpose of transmitting a torque that has been amplified through deceleration.
Further, because of a characteristic of the gear train, the two clutches for inputting decelerated rotation rotate at a high speed at a certain speed-change stage. Therefore, the rigidity of the two clutches must be further increased not only to transmit a high torque but also to stand high-speed rotation. In this respect, according to the structure of the related art, since the two clutches for inputting of decelerated rotation are arranged on one side of the planetary gear set, a member coupling one of the clutches to the planetary gear set passes through an outer space of the other clutch. If such a member is arranged on the outer space of the other clutch, the centrifugal force resulting from high-speed rotation further increases. The rigidity of the member coupling one of the clutches to the planetary gear set needs to be further enhanced, which causes an increase in size and weight.
If the high-torque transmitting member that rotates together with the planetary gear set becomes long and heavy, the inertia torque increases correspondingly. Therefore, the speed-change controllability deteriorates and speed-change shock may be caused.
The invention has been made in consideration of such circumstances. It is an object of the invention to provide a vehicular automatic transmission wherein the enlargement of the mechanism resulting from a multi-staged design is averted and the speed-change controllability is enhanced through reduction in weight and size of a high-torque transmission system by an ingenious arrangement of two clutches for inputting of decelerated rotation with respect to a planetary gear set.
SUMMARY OF THE INVENTION
The invention has been made in consideration of such circumstances. It is an object of the invention to provide a vehicular automatic transmission wherein the enlargement of the mechanism resulting from a multi-staged design is averted and the speed-change controllability is enhanced through reduction in weight and size of a high-torque transmission system by using an ingenious arrangement of two clutches for inputting decelerated rotation with respect to a planetary gear set.
In order to achieve the above-stated object, according to the invention, there is provided a vehicular automatic transmission comprising a planetary gear set receiving a decelerated rotation and a non-decelerated rotation as inputs and outputting a plurality of speed-change rotations, a reduction planetary gear arranged axially in juxtaposition with the planetary gear set, an input shaft passing through an inner side of the planetary gear set, and first and third clutches coupling the input shaft to two different speed-change elements of the planetary gear set respectively through the reduction planetary gear in an engageable and disengageable manner, wherein the reduction planetary gear and the third clutch are arranged on one side of the planetary gear set and the first clutch is arranged on the other side of the planetary gear set.
With this structure, the first and third clutches are arranged on opposed sides of the planetary gear set. The length of transmission members extending from the first and third clutches to the speed-change elements of the planetary gear set can be minimized. Thereby the high-torque transmitting member that rotates together with the planetary gear set can be shortened, so that the transmission can be reduced in weight. Also, because the inertia can be decreased greatly, the speed-change controllability is enhanced.
In the aforementioned structure, it is advantageous to adopt a structure wherein an output element of the reduction planetary gear passes through the inner space of the planetary gear set and is connected to the first clutch.
According to this structure, the output member of the reduction planetary gear is connected to the first clutch through the inner space of the planetary gear set, whereby compact coupling can be realized. Also, as the high-torque transmitting member is not enlarged in diameter, the centrifugal force is reduced and the overall weight can be reduced correspondingly. Also, because the inertia can be made small, the speed-change controllability is enhanced.
Moreover, in the aforementioned structure, it is advantageous to adopt a structure wherein the planetary gear set is equipped with at least four speed-change elements, wherein the first speed-change element is connected to the reduction planetary gear by the first clutch in an engageable and disengageable manner, wherein the second speed-change element is connected to the reduction planetary gear by the third clutch in an engageable and disengageable manner and can be engaged to a transmission casing by first engage means, wherein the third speed-change elements is connected to the input shaft by a second clutch in an engageable and disengageable manner and can be engaged to the transmission casing by second engage means, and wherein the fourth speed-change element is connected to an output member.
According to this structure, the six-speed automatic transmission achieving the aforementioned effect can be realized with a small number of speed-change elements.
Further, in the aforementioned structure, it is advantageous to adopt a structure wherein a clutch drum of the first clutch is arranged such that an opening side thereof faces the planetary gear set and is connected to an output member of the reduction planetary gear.
According to this structure, the clutch drum of the first clutch is connected to the output member of the reduction planetary gear, so that the clutch drum of the first clutch can be arranged on the input shaft without the intervention of other components. Thus, the number of seal rings that are required to prevent leakage of the oil passage for supplying a hydraulic pressure to the hydraulic servo within the drum can be reduced.
Further, in the aforementioned structure, it is advantageous to adopt a structure wherein a frictional member of the third clutch is arranged on an outer space of the reduction planetary gear and wherein a clutch drum of the third clutch is connected to an input member for the planetary gear set.
Further, acc
Gotou Kenji
Hayabuchi Masahiro
Inagaki Tomochika
Kasuya Satoru
Nishida Masaaki
Aisin Aw Co. Ltd.
Marmor Charles A
Oliff & Berridg,e PLC
Waddell Tisha D.
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