A family of transmission gearing arrangements provides a plurality of forward speed ratios and one or more reverse speed ratios by selective engagement of shift elements in various combinations. An input and an output are provided. Three planetary gear sets are located at an offset position relative to the input axis and the output axis. Axis transfer gears are provided to transfer rotational energy from the input to one of the planetary gear sets, and from one of the planetary gear sets to the output.

TECHNICAL FIELD

The present disclosure generally relates to automatic transmission for motor vehicles. More specifically, the present disclosure relates to an arrangement of gears, clutches, and the interconnections among them in a power transmission.

BACKGROUND

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. Typically, a transmission has a housing mounted to the vehicle structure, an input driven by an engine crankshaft, often via a launch device such as a torque converter, and an output driving the vehicle wheels, often via a differential assembly which permits the left and right wheel to rotate at slightly different speeds as the vehicle turns. In front wheel drive vehicles with transverse mounted engines, the engine crankshaft axis is typically offset from the axle axis.

A common type of automatic transmission utilizes a collection of clutches and brakes. Various subsets of the clutches and brakes are engaged to establish the various speed ratios. A common type of clutch utilizes a clutch pack having separator plates splined to a housing and interleaved with friction plates splined to a rotating shell. When the separator plates and the friction plates are forced together, torque may be transmitted between the housing and the shell. Typically, a separator plate on one end of the clutch pack, called a reaction plate, is axially held to the housing. A piston applies axial force to a separator plate on the opposite end of the clutch pack, called a pressure plate, compressing the clutch pack. The piston force is generated by supplying pressurized fluid to a chamber between the housing and the piston. For a brake, the housing may be integrated into the transmission case. For a clutch, the housing rotates. As the pressurized fluid flows from the stationary transmission case to the rotating housing, it may need to cross one or more interfaces between components rotating at different speeds. At each interface, seals direct the flow from an opening in one component into an opening in the interfacing component.

SUMMARY

According to one embodiment, a transmission comprises an input configured to rotate about an input axis, and an output configured to rotate about an output axis. A third axis transfer gear is fixed to the input. A fourth axis transfer gear is configured to rotate about the output axis and in continuous meshing engagement with the third axis transfer gear. A second simple planetary gear set includes a second sun gear, a second carrier, and a second ring gear is fixedly coupled to the output. A third simple planetary gear set includes a third sun gear, a third carrier, and a third ring gear fixedly coupled to the fourth axis transfer gear. A second shift element is configured to selectively couple the second sun gear to the third carrier. A third shift element is configured to selectively hold the third sun gear against rotation. A fourth shift element is configured to selectively hold the second carrier against rotation. A sixth shift element is configured to selectively couple the second sun gear to the third sun gear. A first axis transfer gear is fixed to the input, and a second axis transfer gear is configured to rotate about the output axis and in continuous meshing engagement with the first axis transfer gear.

According to one or more embodiment, the transmission further comprises a fifth shift element configured to selectively couple the second carrier to the second axis transfer gear.

According to one or more embodiment, the transmission further comprises a first simple planetary gear set having a first sun gear fixedly coupled to the second sun gear, a first carrier fixedly coupled to the output, a first ring gear, and a first shift element configured to selectively couple the first ring gear to the third carrier.

According to one or more embodiment, the transmission further comprises a first simple planetary gear set having a first sun gear, a first carrier fixedly coupled to the output, a first ring gear fixedly coupled to the second carrier, and a first shift element configured to selectively couple the first sun gear to the third carrier.

According to one or more embodiment, the transmission further comprises a first simple planetary gear set having a first sun gear, a first carrier, and a first ring gear, and a first shift element configured to selectively couple the first carrier to the output.

According to one or more embodiment, the transmission further comprises a first simple planetary gear set having a first sun gear, a first carrier, and a first ring gear fixedly coupled to the third carrier, and a first shift element configured to selectively couple the first sun to the second sun.

According to another embodiment, a transmission comprises an input, an output, and first, second, third, fourth, fifth, sixth, and seventh shafts. A third gearing arrangement is configured to fixedly impose a linear speed relationship among third shaft, the fourth shaft, the output, and the second shaft. A fourth gearing arrangement is configured to fixedly impose a linear speed relationship among fifth shaft, the sixth shaft, and the seventh shaft. A second shift element configured to selectively couple the third shaft to the sixth shaft. A fourth shift element is configured to selectively hold the fourth shaft against rotation. A sixth shift element configured to selectively couple the third shaft to the fifth shaft.

According to yet another embodiment, a transmission comprises an input, an output, and first, third, fourth, fifth, sixth, and seventh shafts. A fourth gearing arrangement is configured to fixedly impose a linear speed relationship among third shaft, the fourth shaft, and the output. A fifth gearing arrangement is configured to fixedly impose a linear speed relationship among fifth shaft, the sixth shaft, and the seventh shaft. A second shift element is configured to selectively couple the third shaft to the sixth shaft. A third shift element is configured to selectively hold the fifth shaft against rotation. A fourth shift element is configured to selectively hold the fourth shaft against rotation. A sixth shift element is configured to selectively couple the third shaft to the fifth shaft.

DETAILED DESCRIPTION

A gearing arrangement is a collection of rotating elements and shift elements configured to impose specified speed relationships among the rotating elements. Some speed relationships, called fixed speed relationships, are imposed regardless of the state of any shift elements. Other speed relationships, called selective speed relationships, are imposed only when particular shift elements are fully engaged. A linear speed relationship exists among an ordered list of rotating elements when i) the first and last rotating element in the group are constrained to have the most extreme speeds, ii) the speeds of the remaining rotating elements are each constrained to be a weighted average of the first and last rotating element, and iii) when the speeds of the rotating elements differ, they are constrained to be in the listed order, either increasing or decreasing. The speed of an element is positive when the element rotates in one direction and negative when the element rotates in the opposite direction. A discrete ratio transmission has a gearing arrangement that selectively imposes a variety of speed ratios between an input shaft and an output shaft.

A group of rotating elements are fixedly coupled to one another if they are constrained to rotate as a unit in all operating conditions. Rotating elements can be fixedly coupled by spline connections, welding, press fitting, machining from a common solid, or other means. Slight variations in rotational displacement between fixedly coupled elements can occur such as displacement due to lash or shaft compliance. One or more rotating elements that are all fixedly coupled to one another may be called a shaft. In contrast, two rotating elements are selectively coupled by a shift element when the shift element constrains them to rotate as a unit whenever it is fully engaged and they are free to rotate at distinct speeds in at least some other operating condition. A shift element that holds a rotating element against rotation by selectively connecting it to the housing is called a brake. A shift element that selectively couples two or more rotating 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 rotating elements are coupled if they are either fixedly coupled or selectively coupled.

An element is a transmission input if it is adapted to be fixedly coupled to either a power source or the output of a launch device. A power source may be, for example, an internal combustion engine or an electric motor. A launch device may be, for example, a torque converter or a launch clutch. The input may be coupled to the power source or launch device via a damper designed to absorb torsional vibrations. An element is a transmission output if it is adapted to transmit power to components outside the transmission such as vehicle wheels. There may be a fixed speed ratio other than 1:1 between the output element and the driven component.

An example transmission is schematically illustrated inFIG. 1. In this transmission, input10rotates about an input axis and is driven by the engine, preferably via a launch device such as a torque converter or launch clutch. Output12rotates about an output axis and transmits rotational torque out of the transmission and towards a differential, for example. An additional gear or sprocket (not shown) transmits power from the output to the differential which is located on a third axis.

Various lay shafts or axis transfer gears may be provided. For example, a first axis transfer gear16is fixed to the input10and configured to rotate about the input axis. A second axis transfer gear17is configured to rotate about the output axis and is in continuous meshing engagement with the first axis transfer gear16. The first and second axis transfer gears16,17form a gearing arrangement to transfer the rotation of the input10to another axis offset from the input axis. The first and second axis transfer gears16,17may be of different diameters and may each include a different number of gear teeth to transfer rotational energy from the first axis transfer gear16to the second axis transfer gear17while altering the rotational speed. Alternatively, this function may be provided by other types of gearing arrangements such as a chain and sprockets.

Similar to the first and second axis transfer gears16,17, a third axis transfer gear18may also be fixed to the input and in continuous messing engagement with a fourth axis transfer gear19. The third and fourth axis transfer gears18,19also cooperate to transfer rotation of the input10to the output axis. The first axis transfer gear16and third axis transfer gear18may also be of different diameters to enable a range of various rotational speeds being created from multiple sets of axis transfer gears. Additional sets of axis transfer gears may also be provided.

The transmission ofFIG. 1utilizes three simple planetary gear sets20,30, and40. A simple planetary gear set is a type of fixed gearing arrangement, although the term “gearing arrangement” may refer to one or more simple planetary gear sets. A planet carrier22rotates about a central axis and supports a set of planet gears24such that the planet gears rotate with respect to the planet carrier. External gear teeth on the planet gears mesh with external gear teeth on a sun gear26and with internal gear teeth on a ring gear28. The sun gear26and ring gear28are supported to rotate about the same axis as the carrier22. Gear sets30and40are structured similarly to gear set20, and each includes respective planet carriers32,42, planet gears34,44, sun gears36,46, and ring gears38,48.

A simple planetary gear set, such as gear set20, imposes a fixed speed relationship. The speed of the carrier is constrained to be between the speed of the sun gear and the speed of the ring gear. More specifically, the speed of the carrier is a weighted average of the speed of the sun gear and the speed of the ring gear with weighting factors determined by the number of teeth on each gear. Similar speed relationships are imposed by other types of fixed gearing arrangements that may be implemented in other exemplary embodiments of the present disclosure. For example, a double pinion planetary gear set constrains the speed of the ring gear to be a weighted average between the speed of the sun gear and the speed of the carrier.

The combination of axis transfer gears16and17may be referred to as a first gearing arrangement. The combination of axis transfer gears18and19may be referred to as a second gearing arrangement. The planetary gear sets20,30and40may be referred to as third, fourth and fifth gearing arrangements, respectively.

A suggested ratio of gear teeth for each planetary gear set and axis transfer gear set is listed in Table 1, below.

In the transmission ofFIG. 1, sun gear26is fixedly coupled to sun gear36. Carrier22is fixedly coupled to ring gear38and to the output12. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Several shift elements such as clutches and brakes are utilized throughout the transmission to selectively couple various elements of the planetary gear sets and/or selectively hold the various elements against rotation. For example, ring gear28is selectively coupled to carrier42by clutch60. Sun gears26,36are selectively coupled to carrier42by clutch62. Sun gear46and carrier32are selectively held against rotation by brakes64,66, respectively. Clutch68selectively couples input10to carrier32through the gearing ratio provided by axis transfer gears16and17; axis transfer gear16may be fixed to input10while axis transfer gear17is selectively coupled to carrier32via clutch68, or alternatively, axis transfer gear16is selectively coupled to input10via clutch68while axis transfer gear17is fixed to carrier32. Sun gears26,36are selectively coupled to sun gear46by clutch70.

One or more rotating elements that are all fixedly coupled to one another may be called a shaft. For example, a first shaft extends between axis transfer gear17and clutch68. A second shaft extends between ring gear28and clutch60. A third shaft extends between sun gears26,36and clutches62,70. A fourth shaft extends between carrier32and brake66, clutch68. A fifth shaft extends between sun gear46and brake64, clutch70. A sixth shaft extends between carrier42and clutches60,62. A seventh shaft extends between ring gear48and axis transfer gear19.

Gear sets20and30collectively impose a fixed linear speed relationship among the third shaft, the fourth shaft, the output shaft, and the second shaft. A similar linear speed relationship among four shafts may be imposed by other types of gearing arrangements. In particular, any two planetary gear sets with two elements of the first gear set fixedly coupled to two elements of the second gear set will impose such a relationship.

As shown in Table 2 below, engaging shift elements in combinations of three establishes eleven forward speed ratios and two reverse speed ratios between input10and output12. 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.

While an 11-speed transmission is exemplified in Table 2 along with the description provided above, it should be understood that a 5-speed transmission can be achieved by removing, for example, clutch70. Other such alterations to the 11-speed transmission are contemplated, and the 11-speed configuration is merely exemplary.

Various other transmissions are illustrated inFIGS. 2-7and are described below. These transmissions may utilize the suggested ratio of gear teeth for the planetary gear sets as provided in Table 1 above. These transmissions may also utilize the shift schedule provided in Table 2 above to result in a transmission having eleven forward speed ratios and two reverse speed ratios.

In the transmission ofFIG. 2, sun gear26is fixedly coupled to sun gear36. Ring gear28is fixedly coupled to carrier42. Ring gear38is fixedly coupled to output12. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Carrier22is selectively coupled to ring gear38and to the output12by clutch60. Sun gears26,36are selectively coupled to carrier42by clutch62. Sun gear46and carrier32are selectively held against rotation by brakes64and66, respectively. Carrier32is selectively coupled to the second axis transfer gear17by clutch68. Sun gears26,36are selectively coupled to sun gear46by clutch70.

In the transmission ofFIG. 3, carrier22is fixedly coupled to ring gear38and to output12. Ring gear28is fixedly coupled to carrier42. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Sun gear26is selectively coupled sun gear36by clutch60. Sun gear36is selectively coupled to carrier42and ring gear28by clutch62. Sun gear46is selectively held against rotation by brakes64. Carrier32is selectively held against rotation by brake66, and is selectively coupled to the second axis transfer gear17by clutch68. Sun gear36is selectively coupled to sun gear46by clutch70.

In the transmission ofFIG. 4, carrier22is fixedly coupled to ring gear38and to output12. Ring gear28is fixedly coupled to carrier32. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Sun gear26is selectively coupled to carrier42by clutch60. Sun gear36is selectively coupled to carrier42by clutch62. Sun gear46is selectively held against rotation by brake64. Carrier32and ring gear28are selectively held against rotation by brake66, and selectively coupled to the second axis transfer gear17by clutch68. Sun gear36is selectively coupled to sun gear46by clutch70.

In the transmission ofFIG. 5, sun gear26is fixedly coupled to carrier42. Ring gear28is fixedly coupled to carrier32. Ring gear38is fixedly coupled to output12. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Carrier22is selectively coupled to output12and ring gear38by clutch60. Sun gear36is selectively coupled to carrier42and sun gear26by clutch62. Sun gear46is selectively held against rotation by brake64. Carrier32is selectively held against rotation by brake66, and is selectively coupled to the second axis transfer gear17by clutch68. Sun gear36is selectively coupled to sun gear46by clutch70.

In the transmission ofFIG. 6, sun gear26is fixedly coupled to carrier42. Carrier22is fixedly coupled to ring gear38and to output12. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Ring gear28is selectively coupled to carrier32by clutch60. Sun gear36is selectively coupled to sun gear26and carrier42by clutch62. Sun gear46is selectively held against rotation by brake64. Carrier32is selectively held against rotation by brake66, and is selectively coupled to the second axis transfer gear17by clutch68. Sun gear36is selectively coupled to sun gear46by clutch70.

In the transmission ofFIG. 7, a Ravigneaux gear set80is illustrated. The Revigneaux gear set80includes two sun gears86,87, a single planet carrier82, and two sets of planetary gears84,85and one ring gear88meshing with the outermost of the planetary gears85. In this example, ring gear88is fixedly coupled to the output12. Ring gear48is fixedly coupled to the fourth axis transfer gear19.

Sun gear86is selectively coupled to carrier42by clutch60. Sun gear87is selectively coupled to carrier42by clutch62. Sun gear46is selectively held against rotation by brake64. Carrier82is selectively held against rotation by brake66, and is selectively coupled to the second axis transfer gear17by clutch68. Sun gear87is selectively coupled to sun gear46by clutch70.