Patent Application
20180298990
This disclosure related to the field of automotive transmissions. More particularly, the disclosure relates to a carrier assembly adapted for fixation to a shaft and a ring gear.
Many vehicles are used over a wide range of vehicle speeds, including both forward and reverse movement. Some types of engines, however, are capable of operating efficiently only within a narrow range of speeds. Consequently, transmissions capable of efficiently transmitting power at a variety of speed ratios are frequently employed. When the vehicle is at low speed, the transmission is usually operated at a high speed ratio such that it multiplies the engine torque for improved acceleration. At high vehicle speed, operating the transmission at a low speed ratio permits an engine speed associated with quiet, fuel efficient cruising.
A carrier includes first and second plates and an outer shell. The first plate defines a set of slots. The outer shell has a first end rigidly fixed to the first plate and a series of axial teeth formed at a second end. The outer shell may have a first thickness adjacent to the first plate and a second, greater thickness at the axial teeth. The axial teeth define a snap ring groove. The second plate has a set of tabs inserted into the slots. The first and second plates are adapted to support opposite ends of a series of planet gear shafts. For example, each plate may define opposing holes to support opposite ends of the planet gear shafts. The outer shell may define windows aligned with the holes through which planet gears may be inserted during assembly.
A transmission includes first and second gearsets, each having a sun gear, a ring gear, and a carrier. A carrier of the first gearset has an outer shell with an open end terminating in a first set of axial teeth. A ring gear of the second gearset has a second series of axial teeth interleaved with the first set of axial teeth. A snap ring may be inserted into a groove defined in the first and second sets of axial teeth. The first carrier may also include first and second plates. The first plate may be rigidly fixed to the outer shell and may define a set of slots. The second plate may have a set of tabs inserted into the slots. The first and second plates may be adapted to support opposite ends of a set of planet gear shafts. An output element may be splined to an orifice defined in the second plate.
A method of assembling a transmission includes inserting tabs of a first plate into slots of a second plate, meshing a first set of axial teeth with a second set of axial teeth, and inserting a snap ring. The first and second plates form a carrier. The first set of axial teeth is part of an outer shell fixed to the second plate. The second set of axial teeth are fixed to a ring gear. The intermeshing teeth rotationally fix the ring gear to the carrier. The snap ring is inserted into a groove formed in the axial teeth and axially fixes the ring gear to the carrier. An output element may be inserted into a splined aperture in the first plate. Planet gears may be assembled to the carrier by inserting each planet gear through a window in the outer shell, inserting a planet gear shaft through the planet gear and through holes in the first and second plates, an securing the shaft to one of the plates.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
A group of rotatable elements are fixedly coupled to one another if they are constrained to rotate at the same speed about the same axis in all operating conditions. Rotatable elements may be fixedly coupled by, for example, spline connections, welding, press fitting, or machining from a common solid. Slight variations in rotational displacement between fixedly coupled elements may occur such as displacement due to lash or shaft compliance. In contrast, two rotatable elements are selectively coupled by a shift element when the shift element constrains them to rotate at the same speed about the same axis whenever the shift element is fully engaged and the rotatable elements are free to rotate at distinct speeds in at least some other operating condition. A shift element that selectively holds a rotatable element against rotation by selectively connecting it to the housing is called a brake. A shift element that selectively couples two or more rotatable elements to one another is called a clutch. Shift elements may be actively controlled devices such as hydraulically or electrically actuated clutches or brakes or may be passive devices such as one way clutches or brakes. Two rotatable elements are coupled if they are either fixedly coupled or selectively coupled.
The transaxle of
Sun gear 46 is fixedly coupled to turbine shaft 12. Ring gear 38 and carrier 52 are fixedly coupled to output element 14. Ring gear 28, carrier 42, and ring gear 58 are mutually fixedly coupled. Carrier 22 is fixedly coupled to sun gear 36. Carrier 32 is fixedly coupled to ring gear 48. Turbine shaft 12 is selectively coupled to ring gear 28 by clutch 60. Sun gear 26 is selectively coupled to turbine shaft 12 by clutch 62 and selectively held against rotation by brake 64. Carrier 22 and sun gear 36 are selectively held against rotation by brake 66. One way brake 68 permits carrier 32 to rotate in one direction but prevents rotation in the opposite direction. Brake 70 selectively holds carrier 32 against rotation in either direction. Finally, brake 72 selectively holds sun gear 56 against rotation.
As shown in Table 2, engaging the shift elements in specified combinations establishes eight forward speed ratios and one reverse speed ratio between turbine shaft 12 and output element 14. An X indicates that the shift element is required to establish the speed ratio. When the gear sets have tooth numbers as indicated in Table 1, the speed ratios have the values indicated in Table 2. In 1st gear, the transmission transfers power from turbine shaft 12 to first sprocket 14 but one way brake 68 overruns to prevent transfer of power in the opposite direction. The M1 state has the same speed ratio as 1st gear, but is capable of transferring power in either direction.
At 110, the carrier itself is assembled by inserting the tabs 84 of second plate 82 into the slots 86 of first plate 80. These tabs are then permanently fixed in some manner such as welding. At 112, the planet gears 54 are assembled to the carrier 52. Prior to installation of the planet gears into the carrier, the roller bearings may be inserted into a cage which is inserted into the hollow planet gears. Then, the planet gears and bearings are inserted through windows 100 into position. Planet shafts are inserted through hole 88, the roller bearings, and hole 90, from either direction. The planet shafts are then fixed, for example, by snap rings. At 114, the output element 14 is attached to carrier 52 at the splined aperture 92.
At 116 and 118, ring gear 38 is attached to carrier 52. This may occur before or after the planet gears are installed and before or after the output element is installed. At 116, the axial teeth of ring gear 38 are meshed with the axial teeth 98 of carrier 52. Then, at 118, snap ring 98 is inserted into the groove formed in the axial teeth.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
