Multi-speed transmission having three planetary gear sets

A transmission is provided having an input member, an output member, three planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices include clutches and brakes.

FIELD

The invention relates generally to a multiple speed transmission having a plurality of planetary gear sets and a plurality of torque transmitting devices and more particularly to a transmission having eight or more speeds, three planetary gear sets and a plurality of torque transmitting devices.

BACKGROUND

A typical multiple speed transmission uses a combination of friction clutches, planetary gear arrangements and fixed interconnections to achieve a plurality of gear ratios. The number and physical arrangement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need for new and improved transmission configurations which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness and improved packaging, primarily reduced size and weight, is essentially constant. Accordingly, there is a need for an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member, three planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices are for example clutches and brakes.

In another embodiment of the transmission, the transmission has an input member, an output member, first, second, and third planetary gear sets. Each of the planetary gear sets has a sun gear, carrier and ring gear members. The input member is continuously interconnected to the sun gear member of the second planetary gear set and the output member is continuously interconnected to the ring gear member of the third planetary gear set.

Moreover, a first interconnecting member continuously interconnects the first member of the first planetary gear set with the third member of the second planetary gear set. A second interconnecting member continuously interconnects the second member of the first planetary gear set with the first member of the third planetary gear set.

Additionally, a first torque transmitting mechanism is selectively engageable to interconnect the first member of the second planetary gear set with the second member of the third planetary gear set. A second torque transmitting mechanism is selectively engageable to interconnect the second member of the second planetary gear set with the second member of the third planetary gear set. A third torque transmitting mechanism is selectively engageable to interconnect the second member of the second planetary gear set with at least one of the second member of the first planetary gear set and the first member of the third planetary gear set. A fourth torque transmitting mechanism is selectively engageable to interconnect at least one of the first member of the first planetary gear set and the third member of the second planetary gear set with the stationary element. A fifth torque transmitting mechanism is selectively engageable to interconnect the third member of the first planetary gear set with the stationary element. A sixth torque transmitting mechanism is selectively engageable to interconnect the second member of the third planetary gear set with the stationary element. The torque transmitting mechanisms are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

Thus, it is an object of the present invention to provide a transmission having at least eight forward speeds and at least one reverse.

It is further an object of the present invention to provide a transmission having three planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices.

DETAILED DESCRIPTION

Referring now toFIG. 1, an embodiment of an eight speed transmission10is illustrated in a lever diagram format. A lever diagram is a schematic representation of the components of a mechanical device such as an automatic transmission. Each individual lever represents a planetary gear set wherein the three basic mechanical components of the planetary gear are each represented by a node. Therefore, a single lever contains three nodes: one for the sun gear, one for the planet gear carrier, and one for the ring gear. 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.

The transmission10includes an input shaft or member12, a first planetary gear set14having three nodes: a first node14A, a second node14B and a third node14C, a second planetary gear set16having three nodes: a first node16A, a second node16B and a third node16C and a third planetary gear set18having three nodes: a first node18A, a second node18B and an output shaft or member22.

The input member12is coupled to the first node16A of the second planetary gear set16. The output member22is coupled to the third node18C of the third planetary gear set18. The first node14A of the first planetary gear set14is coupled to the third node16C of the second planetary gear set16. The second node14B of the first planetary gear set14is coupled to the first node18A of the third planetary gear set18.

A first clutch26selectively connects the first node16A of the second planetary gear set16with the second node18B of the third planetary gear set18. A second clutch28selectively connects the second node16B of the second planetary gear set16with the second node18B of the third planetary gear set18. A third clutch30selectively connects the second node16B of the second planetary gear set16to second node14B of the first planetary gear set14and the first node18A of the third planetary gear set18. A first brake32selectively connects the third node16C of the second planetary gear set16and the first node14A of the first planetary gear set14to a stationary member or transmission housing50. A second brake34selectively connects the third node14C of the first planetary gear set14to the stationary member or transmission housing50. A third brake36selectively connects the second node18B of the third planetary gear set18to a stationary member or transmission housing50.

Referring now toFIG. 2, a stick diagram presents a schematic layout of the embodiment of the eight speed transmission10according to the present invention. InFIG. 2, the numbering from the lever diagram ofFIG. 1is carried over. The clutches and couplings are correspondingly presented whereas the nodes of the planetary gear sets now appear as components of planetary gear sets such as sun gears, ring gears, planet gears and planet gear carriers.

For example, the planetary gear set14includes a sun gear member14C, a ring gear member14A and a planet gear carrier member14B that rotatably supports a first set of planet gears14D (only one of which is shown) and a second set of planet gears14E (only one of which is shown). The sun gear member14C is connected for common rotation with a first shaft or interconnecting member42. The ring gear member14A is connected for common rotation with a second shaft or interconnecting member44. The planet carrier member14B is connected for common rotation with a third shaft or interconnecting member46. Each of the planet gears14D are configured to intermesh with both the sun gear member14C and planet gears14E. Each of the planet gears14E are configured to intermesh with both the ring gear member14A and the planet gears14D.

The planetary gear set16includes a sun gear member16A, a ring gear member16C and a planet gear carrier member16B that rotatably supports a set of planet gears16D (only one of which is shown). The sun gear member16A is connected for common rotation with a fourth shaft or interconnecting member48and with input member12. The ring gear member16C is connected for common rotation with the second shaft or interconnecting member44. The planet carrier member16B is connected for common rotation with the fifth shaft or interconnecting member52. Each of the planet gears16D are configured to intermesh with both the sun gear member16A and the ring gear member16C.

The planetary gear set18includes a sun gear member18A, a ring gear member18C and a planet gear carrier member18B that rotatably supports a set of planet gears18D (only one of which is shown). The sun gear member18A is connected for common rotation with third shaft or interconnecting member46. The ring gear member18C is connected for common rotation with output shaft or member22. The planet carrier member18B is connected for common rotation with a sixth shaft or interconnecting member54and with an seventh shaft or interconnecting member56. Each of the planet gears18D are configured to intermesh with both the sun gear member18A and the ring gear member18C.

The input shaft or member12is continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output shaft or member22is continuously connected with the final drive unit or transfer case (not shown).

The torque-transmitting mechanisms or clutches26,28and30and brakes32,34and36allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. For example, the first clutch26is selectively engageable to connect the fourth shaft or interconnecting member48and input member12with the sixth shaft or interconnecting member54. The second clutch28is selectively engageable to connect the fifth shaft or interconnecting member52with the seventh shaft or interconnecting member54. The third clutch30is selectively engageable to connect the third shaft or interconnecting member46with the fifth shaft or interconnecting member52. The first brake32is selectively engageable to connect the second shaft or interconnecting member44with the stationary element or the transmission housing50in order to restrict the member44from rotating relative to the transmission housing50. The second brake34is selectively engageable to connect the first shaft or interconnecting member42with the stationary element or the transmission housing50in order to restrict the member42from rotating relative to the transmission housing50. The third brake36is selectively engageable to connect the seventh shaft or interconnecting member56with the stationary element or the transmission housing50in order to restrict the member56from rotating relative to the transmission housing50.

Referring now toFIG. 2andFIG. 3, the operation of the embodiment of the eight speed transmission10will be described. It will be appreciated that transmission10is capable of transmitting torque from the input shaft or member12to the output shaft or member22in at least eight forward speed or torque ratios and at least one reverse speed or torque ratio with triple overdrive. Each forward and reverse speed or torque ratio is attained by engagement of one or more of the torque-transmitting mechanisms (i.e. first clutch26, second clutch28, third clutch30, first brake32, second brake34and third brake36), as will be explained below.FIG. 3is a truth table presenting the various combinations of torque-transmitting mechanisms that are activated or engaged to achieve the various gear states. An “X” in the box means that the particular clutch or brake is engaged to achieve the desired gear state. An “O” represents that the particular torque transmitting device (i.e. a brake or clutch) is on or active, but not carrying torque. Actual numerical gear ratios of the various gear states are also presented although it should be appreciated that these numerical values are exemplary only and that they may be adjusted over significant ranges to accommodate various applications and operational criteria of the transmission10. An example of the gear ratios that may be obtained using the embodiments of the present invention are also shown inFIG. 3. Of course, other gear ratios are achievable depending on the gear diameter, gear teeth count and gear configuration selected.

To establish a reverse gear, the third clutch30, second brake34and third brake36are engaged or activated. The third clutch30connects the third shaft or interconnecting member46with the fifth shaft or interconnecting member52. The second brake34connects the first shaft or interconnecting member42with the stationary element or the transmission housing50in order to restrict the member42from rotating relative to the transmission housing50. The third brake36connects the seventh shaft or interconnecting member56with the stationary element or the transmission housing50in order to restrict the member56from rotating relative to the transmission housing50. Likewise, the eight forward ratios are achieved through different combinations of clutch and brake engagement, as shown inFIG. 3.

It will be appreciated that the foregoing explanation of operation and gear states of the eight speed transmission10assumes, first of all, that all the clutches not specifically referenced in a given gear state are inactive or disengaged and, second of all, that during gear shifts, i.e., changes of gear state, between at least adjacent gear states, a clutch engaged or activated in both gear states will remain engaged or activated.