Patent Application
20150087464
The present disclosure relates to automatic transmissions and more particularly to a two mode continuously variable transmission.
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A continuously variable transmission (“CVT”) typically includes a belt and pulley system that operatively couples a rotary power source, such as an engine or electric motor, to a double gear final drive unit. The belt and pulley system generally includes first and second pairs of pulley cones having a torque transmitting belt or chain extending between the cone pairs. Each pulley cone pair includes an axially stationary pulley member and an axially movable pulley member. Each movable pulley member is axially adjustable with respect to the stationary pulley member by a hydraulic system. The hydraulic system provides primary and secondary hydraulic pressures to the respective movable pulley members to adjust the running radius of the first and second pulley cone pairs which in turn controls the output/input ratio of the continuously variable transmission. Movement of the cones steplessly or continuously varies the ratio of an input speed to an output speed. With the continuously variable transmission, small but effective ratio changes can be attained. This is in contrast to a fixed gear ratio unit where any ratio changes are step values.
CVT axial length and mass significantly impact its power density and efficiency. Accordingly, there is a constant need for improved CVT designs that minimize axial length and mass while providing sufficient performance characteristics.
A two mode CVT is provided that for a motor vehicle. The two mode CVT includes a speed change device connected to a pulley and belt assembly. The pulley and belt assembly is also connected to a planetary gear set arrangement. The planetary gear set arrangement generally includes two planetary gear sets, one brake and two clutches. The planetary gear set arrangement is connected to a final drive unit.
In another aspect of the present invention, a transmission for a motor vehicle is provided having a transmission input member, a transmission output member, a continuously variable unit, a first transfer gear, a second transfer gear, a planetary gear set assembly, a first clutch, a second clutch, a brake, whereby torque is transferred from the input member to the output member through selective engagement of one of the first clutch and the second clutch thereby selectively connecting the second pulley to the planetary gear set assembly.
In yet another aspect of the present invention, the continuously variable unit has a first pulley, a second pulley and an endless member wrapped around the first pulley and the second pulley.
In yet another aspect of the present invention, the first transfer gear is connected for common rotation with the input member.
In yet another aspect of the present invention, the second transfer gear is in mesh with the first transfer gear and connected for common rotation with the first pulley of the continuously variable unit.
In yet another aspect of the present invention, the planetary gear set assembly has first, second, third and fourth members.
In yet another aspect of the present invention, the first clutch selectively connects the second pulley to the first member of the planetary gear set assembly.
In yet another aspect of the present invention, the second clutch selectively connects the second pulley to the fourth member of the planetary gear set assembly.
In yet another aspect of the present invention, the brake selectively connects the third member of the planetary gear set assembly to a stationary member.
In still another aspect of the present invention, the planetary gear set assembly includes a first planetary gear set and a second planetary gear set. The first planetary gear set has a sun gear connected for common rotation to a sun gear of the second planetary gear set and a carrier member connected for common rotation to the ring gear of the second planetary gear set. The first clutch is connected to the ring gear of the first planetary gear set, the second clutch is connected to the sun gear of the first planetary gear set and the brake is connected to carrier member of the second planetary gear set and the output member is connected for common rotation to the ring gear of the second planetary gear set.
In still another aspect of the present invention, the planetary gear set assembly has a first planetary gear set and a second planetary gear set. The first planetary gear set has a carrier member connected for common rotation to a carrier member of the second planetary gear set and the carrier member of the second planetary gear set has a first and a second set of pinion gears. The first set of pinion gears intermesh with the sun gear of the first planetary gear set and the second set of pinions. The second set of pinions intermesh with the ring gear of the second planetary gear set and the first set of pinion gears. The first clutch is connected to the sun gear of the first planetary gear set, the second clutch is connected to the sun gear of the second planetary gear set and the brake is connected to carrier member of the first planetary gear set. The output member is connected for common rotation to the ring gear of the second planetary gear set.
In still another aspect of the present invention, the planetary gear set assembly includes a first planetary gear set and a second planetary gear set. The first planetary gear set has a carrier member connected for common rotation to a ring gear of the second planetary gear set and a ring gear of the first planetary gear set is connected for common rotation to a carrier member of the second planetary gear set. The first clutch is connected to the sun gear of the first planetary gear set, the second clutch is connected to the sun gear of the second planetary gear set and the brake is connected to carrier member of the first planetary gear set and ring gear of the second planetary gear set. The output member is connected for common rotation to the carrier member of the second planetary gear set.
In still another aspect of the present invention, the planetary gear set assembly has a first planetary gear set and a second planetary gear set in a stacked arrangement. The first planetary gear set and a second planetary gear set share a common member. The common member functions as a ring gear in the first planetary gear set and functions as a sun gear in the second planetary gear set. Additionally, the first planetary gear set and a second planetary gear set share a common carrier member having a first pinion gear that intermeshes with the sun gear of the first planetary gear set and the common member and a second pinion gear that intermeshes with the ring gear of the second planetary gear set and the common member. The first clutch is connected to the common member, the second clutch is connected to the sun gear of the first planetary gear set and the brake is connected to ring gear of the second planetary gear set. The output member is connected for common rotation with the common carrier member.
In still another aspect of the present invention, the planetary gear set assembly includes a first planetary gear set and a second planetary gear set. The first planetary gear set has a carrier member connected for common rotation to a carrier member of the second planetary gear set and a ring gear of the first planetary gear set is connected for common rotation to a ring gear of the second planetary gear set. The first clutch is connected to the ring gear of the first planetary gear set and ring gear of the second planetary gear set, the second clutch is connected to the sun gear of the first planetary gear set and the brake is connected to sun gear of the second planetary gear set. The output member is connected for common rotation to the carrier member of the first and second planetary gear sets.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and is not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
With reference to
The transmission 14 is a variable diameter pulley or sheave drive continuously variable transmission (CVT). The transmission 14 includes a typically cast, metal housing 16 which encloses and protects the various components of the transmission 14. The housing 16 includes a variety of apertures, passageways, shoulders and flanges which position and support these components. Generally speaking, the transmission 14 includes a transmission input shaft 20 and a transmission output shaft 22. Connected between the transmission input shaft 20 and the transmission output shaft 22 is a speed change device 23, a pulley assembly 24, and a gearbox 26 that cooperate to provide forward and reverse speed or gear ratios between the transmission input shaft 20 and the transmission output shaft 22. The transmission input shaft 20 is functionally interconnected with the engine 12 through the starting device 15 and receives input torque or power from the engine 12. The transmission output shaft 22 is preferably connected with a final drive unit 28. The transmission output shaft 22 provides drive torque to the final drive unit 28. The final drive 28 unit may include a differential, axle shafts, and road wheels (not shown).
The transmission input shaft 20 is connected to the speed change device 23. The speed change device 23, as well as the various gearbox 26 arrangements described below, are illustrated in a lever diagram format. A lever diagram is a schematic representation of the components of a mechanical device such as meshing gear sets or planetary gear sets. Each individual lever represents a planetary gear set or meshed gear pair. The three basic mechanical components of the planetary gear are each represented by a node while the gear pairs are represented by a node and the rotation change represented by a node fixed to ground. Therefore, a single lever contains three nodes. In a planetary gear set, one node represents the sun gear, one the planet gear carrier, and one the ring gear. In a meshed gear pair, one node represents a first gear, one a second gear, and the third the rotational direction change between the meshed gears. In some cases, two levers may be combined into a single lever having more than three nodes (typically four nodes). For example, if two nodes on two different levers are interconnected through a fixed connection they may be represented as a single node on a single lever. The relative length between the nodes of each lever can be used to represent the ring-to-sun ratio of each respective gear set. These lever ratios, in turn, are used to vary the gear ratios of the transmission in order to achieve an appropriate ratios and ratio progression. Mechanical couplings or interconnections between the nodes of the various planetary gear sets are illustrated by thin, horizontal lines and torque transmitting devices such as clutches and brakes are presented as interleaved fingers. Further explanation of the format, purpose and use of lever diagrams can be found in SAE Paper 810102, “The Lever Analogy: A New Tool in Transmission Analysis” by Benford and Leising which is hereby fully incorporated by reference.
For example, the speed change device 23 includes a first node 23A, a second node 23B, and a third node 23C. The first node 23A is coupled to the transmission input shaft 20. The second node 23B is fixed to ground representing a change in rotational direction. The third node 23C is coupled to a first transfer shaft or member 29 that is connected to the pulley assembly 24. The first node 23A preferably represents a first gear while the third node 23C preferably represents a second gear meshed with the first gear. The gears may be co-planar or partially axially offset. In a preferred embodiment, the speed change device 23 is an overdrive speed change device 23 that increases the speed of the first transfer shaft 29 relative to the transmission input shaft 20 while decreasing the torque. In a second preferred embodiment, the speed change device 23 is an underdrive speed change device 23. In a third preferred embodiment, the speed change device 23 acts as a direct drive coupling member with no relative speed change.
The pulley assembly 24 includes a first pulley or sheave pair 30 and a second pulley or sheave pair 32. The first pulley 30 includes a first truncated conical sheave or member 30A and second truncated conical sheave or member 30B in axial alignment with the first truncated conical sheave 30A. The second sheave 30B is directly connected for rotation with the first transfer member 29 and may be integrally formed with the first transfer member or shaft 29. The first sheave 30A is moveable axially relative to the second sheave 30B by a hydraulic control system (not shown) or other actuating system. It should be appreciated that the sheaves 30A and 30B may be axially switched without departing from the scope of the present invention.
The second pulley 32 includes a first truncated conical sheave or member 32A and second truncated conical sheave or member 32B in axial alignment with the first truncated conical sheave 32A. The second sheave 32B is directly connected for rotation with a second transfer shaft or member 34 or may be integrally formed with the second transfer shaft 34. The first sheave 32A is moveable axially relative to the second sheave 32B by a hydraulic control system (not shown) or other actuating system. It should be appreciated that the sheaves 32A and 32B may be axially switched without departing from the scope of the present invention.
A torque transmitting belt or chain 36 having a V-shaped cross section is mounted between the first pulley pair 30 and the second pulley pair 32. It should be appreciated that other types of belts, including positive engagement devices, may be employed without departing from the scope of the present invention. Drive torque communicated from the transmission input shaft 20 is transferred via friction between the sheaves 30A and 30B and the belt 36. The ratio of the input pulley 30 to the output pulley 32 is adjusted by varying the spacing between the sheaves 30A and 30B and between the sheaves 32A and 32B. For example, to change the ratio between the pulleys 30 and 32, the axial distance between sheaves 30A and 30B may be reduced by moving sheave 30A towards sheave 30B while simultaneously the axial distance between sheave 32A and 32B may be increased by moving sheave 32A away from sheave 32B. Due to the V-shaped cross section of the belt 36, the belt 36 rides higher on the first pulley 30 and lower on the second pulley 32. Therefore the effective diameters of the pulleys 30 and 32 change, which in turn changes the overall gear ratio between the first pulley 30 and the second pulley 32. Since the radial distance between the pulleys 30 and 32 and the length of the belt 36 is constant, the movement of the sheaves 30A and 32A must occur simultaneously in order to maintain the proper amount of tension on the belt 36 to assure torque is transferred from the pulleys 30, 32 to the belt 36.
The pulley assembly 24 transfers torque to the gearbox 26 via the second transfer shaft 34. The gearbox 26 comprises one of several planetary gear set transmissions or arrangements, as will be described in greater detail below. The gearbox 26 outputs torque from the pulley assembly 26 to the transmission output shaft 22 and then to the final drive unit 28.
Turning now to
The transmission output shaft or member 22 is continuously coupled to node 50B, 52A. A brake 56 selectively connects the node 52B of the second planetary gear set 52 with the stationary element or transmission housing 16. A first clutch 58 selectively connects the node 50A of the first planetary gear set 50 with the second transfer shaft 34. A second clutch 60 selectively connects the combined node 50C, 52C of the first and second planetary gear sets 50 and 52 with second transfer shaft 34.
Turning now to
With specific reference to
Planetary gear set 52 includes a ring gear member 52A, a planet carrier member 52B and a sun gear member 52C. The ring gear member 52A is connected for common rotation with the second shaft or interconnecting member 64 and output member or shaft 22. The planet carrier member 52B is connected for common rotation with a fifth shaft or interconnecting member 70 and rotatably supports a set of planet gears 52D (only one of which is shown). The planet gears 52D are each configured to intermesh with the ring gear member 52A and the sun gear member 52C. The sun gear member 52C is connected for common rotation with the fourth shaft or interconnecting member 68.
Moreover, torque-transmitting mechanisms including brake 56 and clutches 58 and 60 are provided to allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. The torque-transmitting mechanisms are friction, dog or synchronizer type mechanisms or the like. For example, the brake 56 is selectively engageable to connect the fifth shaft or interconnecting member 70 with the transmission housing 16 in order to restrict relative rotation of the member 70 and therefore the carrier member 52B. The first clutch 58 is selectively engageable to connect the second transfer shaft 34 with the first shaft or interconnecting member 62 and the ring gear 50A. The second clutch 60 is selectively engageable to connect the second transfer shaft 34 with the third shaft or interconnecting member 66 and the sun gear 50C.
With specific reference to
Planetary gear set 80 includes a carrier member 80B and a sun gear 80C. The planet carrier member 80B is connected for common rotation with a first shaft or interconnecting member 84 and a second shaft or interconnecting member 86 and rotatably supports a set of planet gears 80D (only one of which is shown). The planet gears 80D are each configured to intermesh with the sun gear member 80C. The sun gear member 80C is connected for common rotation with a third shaft or interconnecting member 88.
Planetary gear set 82 includes a ring gear member 82A, a planet carrier member 82B and a sun gear member 82C. The ring gear member 82A is connected for common rotation with output member or shaft 22. The planet carrier member 82B is connected for common rotation with the second shaft or interconnecting member 86 and rotatably supports a first set of planet gears 82D (only one of which is shown) and a second set of planet gears 82E (only one of which is shown). The first set of planet gears 82D are each configured to intermesh with the sun gear member 82C and the second set of planet gears 82E. The second set of planet gears 82E are each configured to intermesh with the ring gear member 82A and the first set of planet gears 82D. The sun gear member 82C is connected for common rotation with the fourth shaft or interconnecting member 90.
Gearbox 26A further includes torque-transmitting mechanisms including brake 92 and clutches 94 and 96 are provided to allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. The brake 92 is selectively engageable to connect the first shaft or interconnecting member 84 with the transmission housing 16 in order to restrict relative rotation of the member 84 and therefore the carrier members 80B and 82B. The first clutch 94 is selectively engageable to connect the second transfer shaft 34 with the third shaft or interconnecting member 88 and the sun gear 80C. The second clutch 96 is selectively engageable to connect the second transfer shaft 34 with the fourth shaft or interconnecting member 90 and the sun gear 82C.
With specific reference to
With specific reference to
Accordingly, first clutch 58 is selectively engageable to connect the second transfer shaft 34 with the first shaft or interconnecting member 122 and the common member 116. The second clutch 60 is selectively engageable to connect the second transfer shaft 34 with the third shaft or interconnecting member 126 and the sun gear 114C. The brake 56 is selectively engageable to connect the second shaft or interconnecting member 124 with the transmission housing 16 in order to restrict relative rotation of the member 124 and therefore ring gear 112A.
With specific reference to
Referring now to
The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
This application claims the benefit of U.S. Provisional Application No. 61/881,078 filed Sep. 23, 2013. The disclosure of the above application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61881078 | Sep 2013 | US |
