# Patent

## Title
Multi-speed transmission having three planetary gear sets

## Abstract

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.

## Background
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
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
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.
Further objects, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.



DRAWINGS
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
FIG. 1 is a lever diagram of an embodiment of an eight speed transmission according to the present invention;
FIG. 2 is a diagrammatic illustration of an embodiment of an eight speed transmission according to the present invention; and
FIG. 3 is a truth table presenting the state of engagement of the various torque transmitting elements in each of the available forward and reverse speeds or gear ratios of the transmission illustrated in FIGS. 1 and 2.



DETAILED DESCRIPTION
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring now to FIG. 1, an embodiment of an eight speed transmission 10 is 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 transmission 10 includes an input shaft or member 12, a first planetary gear set 14 having three nodes: a first node 14A, a second node 14B and a third node 14C, a second planetary gear set 16 having three nodes: a first node 16A, a second node 16B and a third node 16C and a third planetary gear set 18 having three nodes: a first node 18A, a second node 18B and an output shaft or member 22.
The input member 12 is coupled to the first node 16A of the second planetary gear set 16. The output member 22 is coupled to the third node 18C of the third planetary gear set 18. The first node 14A of the first planetary gear set 14 is coupled to the third node 16C of the second planetary gear set 16. The second node 14B of the first planetary gear set 14 is coupled to the first node 18A of the third planetary gear set 18.
A first clutch 26 selectively connects the first node 16A of the second planetary gear set 16 with the second node 18B of the third planetary gear set 18. A second clutch 28 selectively connects the second node 16B of the second planetary gear set 16 with the second node 18B of the third planetary gear set 18. A third clutch 30 selectively connects the second node 16B of the second planetary gear set 16 to second node 14B of the first planetary gear set 14 and the first node 18A of the third planetary gear set 18. A first brake 32 selectively connects the third node 16C of the second planetary gear set 16 and the first node 14A of the first planetary gear set 14 to a stationary member or transmission housing 50. A second brake 34 selectively connects the third node 14C of the first planetary gear set 14 to the stationary member or transmission housing 50. A third brake 36 selectively connects the second node 18B of the third planetary gear set 18 to a stationary member or transmission housing 50.
Referring now to FIG. 2, a stick diagram presents a schematic layout of the embodiment of the eight speed transmission 10 according to the present invention. In FIG. 2, the numbering from the lever diagram of FIG. 1 is 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 set 14 includes a sun gear member 14C, a ring gear member 14A and a planet gear carrier member 14B that rotatably supports a first set of planet gears 14D (only one of which is shown) and a second set of planet gears 14E (only one of which is shown). The sun gear member 14C is connected for common rotation with a first shaft or interconnecting member 42. The ring gear member 14A is connected for common rotation with a second shaft or interconnecting member 44. The planet carrier member 14B is connected for common rotation with a third shaft or interconnecting member 46. Each of the planet gears 14D are configured to intermesh with both the sun gear member 14C and planet gears 14E. Each of the planet gears 14E are configured to intermesh with both the ring gear member 14A and the planet gears 14D.
The planetary gear set 16 includes a sun gear member 16A, a ring gear member 16C and a planet gear carrier member 16B that rotatably supports a set of planet gears 16D (only one of which is shown). The sun gear member 16A is connected for common rotation with a fourth shaft or interconnecting member 48 and with input member 12. The ring gear member 16C is connected for common rotation with the second shaft or interconnecting member 44. The planet carrier member 16B is connected for common rotation with the fifth shaft or interconnecting member 52. Each of the planet gears 16D are configured to intermesh with both the sun gear member 16A and the ring gear member 16C.
The planetary gear set 18 includes a sun gear member 18A, a ring gear member 18C and a planet gear carrier member 18B that rotatably supports a set of planet gears 18D (only one of which is shown). The sun gear member 18A is connected for common rotation with third shaft or interconnecting member 46. The ring gear member 18C is connected for common rotation with output shaft or member 22. The planet carrier member 18B is connected for common rotation with a sixth shaft or interconnecting member 54 and with an seventh shaft or interconnecting member 56. Each of the planet gears 18D are configured to intermesh with both the sun gear member 18A and the ring gear member 18C.
The input shaft or member 12 is continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output shaft or member 22 is continuously connected with the final drive unit or transfer case (not shown).
The torque-transmitting mechanisms or clutches 26, 28 and 30 and brakes 32, 34 and 36 allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. For example, the first clutch 26 is selectively engageable to connect the fourth shaft or interconnecting member 48 and input member 12 with the sixth shaft or interconnecting member 54. The second clutch 28 is selectively engageable to connect the fifth shaft or interconnecting member 52 with the seventh shaft or interconnecting member 54. The third clutch 30 is selectively engageable to connect the third shaft or interconnecting member 46 with the fifth shaft or interconnecting member 52. The first brake 32 is selectively engageable to connect the second shaft or interconnecting member 44 with the stationary element or the transmission housing 50 in order to restrict the member 44 from rotating relative to the transmission housing 50. The second brake 34 is selectively engageable to connect the first shaft or interconnecting member 42 with the stationary element or the transmission housing 50 in order to restrict the member 42 from rotating relative to the transmission housing 50. The third brake 36 is selectively engageable to connect the seventh shaft or interconnecting member 56 with the stationary element or the transmission housing 50 in order to restrict the member 56 from rotating relative to the transmission housing 50.
Referring now to FIG. 2 and FIG. 3, the operation of the embodiment of the eight speed transmission 10 will be described. It will be appreciated that transmission 10 is capable of transmitting torque from the input shaft or member 12 to the output shaft or member 22 in 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 clutch 26, second clutch 28, third clutch 30, first brake 32, second brake 34 and third brake 36), as will be explained below. FIG. 3 is 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 transmission 10. An example of the gear ratios that may be obtained using the embodiments of the present invention are also shown in FIG. 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 clutch 30, second brake 34 and third brake 36 are engaged or activated. The third clutch 30 connects the third shaft or interconnecting member 46 with the fifth shaft or interconnecting member 52. The second brake 34 connects the first shaft or interconnecting member 42 with the stationary element or the transmission housing 50 in order to restrict the member 42 from rotating relative to the transmission housing 50. The third brake 36 connects the seventh shaft or interconnecting member 56 with the stationary element or the transmission housing 50 in order to restrict the member 56 from rotating relative to the transmission housing 50. Likewise, the eight forward ratios are achieved through different combinations of clutch and brake engagement, as shown in FIG. 3.
It will be appreciated that the foregoing explanation of operation and gear states of the eight speed transmission 10 assumes, 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.
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.

## Claims

1. A transmission comprising:
an input member;
an output member;
first, second, and third planetary gear sets each having a sun gear member, a ring gear member and a carrier member, wherein 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;
a first interconnecting member continuously interconnecting the ring gear member of the first planetary gear set with the ring gear member of the second planetary gear set;
a second interconnecting member continuously interconnecting the carrier member of the first planetary gear set with the sun gear member of the third planetary gear set; and
six torque transmitting mechanisms each selectively engageable to interconnect at least one of the sun gear members, ring gear members and carrier members with at least another of the sun gear members, ring gear members, carrier members and a stationary element, and
wherein the torque transmitting mechanisms are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

2. The transmission of claim 1 wherein a first of the six torque transmitting mechanisms is selectively engageable to interconnect the sun gear member of the second planetary gear set with the carrier member of the third planetary gear set.

3. The transmission of claim 2 wherein a second of the six torque transmitting mechanisms is selectively engageable to interconnect the carrier member of the second planetary gear set with the carrier member of the third planetary gear set.

4. The transmission of claim 3 wherein a third of the six torque transmitting mechanisms is selectively engageable to interconnect the carrier member of the second planetary gear set with at least one of the carrier member of the first planetary gear set and the sun gear member of the third planetary gear set.

5. The transmission of claim 4 wherein a fourth of the six torque transmitting mechanisms is selectively engageable to interconnect at least one of the ring gear member of the first planetary gear set and the ring gear member of the second planetary gear set with the stationary element.

6. The transmission of claim 5 wherein a fifth of the six torque transmitting mechanisms is selectively engageable to interconnect the sun gear member of the first planetary gear set with the stationary element.

7. The transmission of claim 6 wherein a sixth of the six torque transmitting mechanisms is selectively engageable to interconnect the carrier member of the third planetary gear set with the stationary element.

8. The transmission of claim 1 wherein three of the torque transmitting mechanisms are brakes for connecting a plurality of the sun gear members, ring gear members and carrier members to the stationary element and three of the torque transmitting mechanisms are clutches for connecting a set of the sun gear members, ring gear members and carrier members to another set of the sun gear members, ring gear members and carrier members.

9. A transmission comprising:
an input member;
an output member;
first, second, and third planetary gear sets each having sun gear member, a ring gear member and a carrier member
a first interconnecting member continuously interconnecting the ring gear member of the first planetary gear set with the ring gear member of the second planetary gear set;
a second interconnecting member continuously interconnecting the carrier member of the first planetary gear set with the sun gear member of the third planetary gear set;
a first torque transmitting mechanism selectively engageable to interconnect the sun gear member of the second planetary gear set with the carrier member of the third planetary gear set;
a second torque transmitting mechanism selectively engageable to interconnect the carrier member of the second planetary gear set with the carrier member of the third planetary gear set;
a third torque transmitting mechanism selectively engageable to interconnect the carrier member of the second planetary gear set with at least one of the carrier member of the first planetary gear set and the sun gear member of the third planetary gear set;
a fourth torque transmitting mechanism selectively engageable to interconnect at least one of the ring gear member of the first planetary gear set and the ring gear member of the second planetary gear set with the stationary element;
a fifth torque transmitting mechanism selectively engageable to interconnect the sun gear member of the first planetary gear set with the stationary element; and
a sixth torque transmitting mechanism selectively engageable to interconnect the carrier member of the third planetary gear set with the stationary element,
wherein the torque transmitting mechanisms are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

10. The transmission of claim 9 wherein 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.

11. A transmission comprising:
an input member;
an output member;
first, second, and third planetary gear sets each having a sun gear member, a carrier member and a ring gear member, wherein 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;
a first interconnecting member continuously interconnecting the ring gear member of the first planetary gear set with the ring gear member of the second planetary gear set;
a second interconnecting member continuously interconnecting the carrier member of the first planetary gear set with the sun gear member of the third planetary gear set;
a first torque transmitting mechanism selectively engageable to interconnect the sun gear member of the second planetary gear set with the carrier member of the third planetary gear set;
a second torque transmitting mechanism selectively engageable to interconnect the carrier member of the second planetary gear set with the carrier member of the third planetary gear set;
a third torque transmitting mechanism selectively engageable to interconnect the carrier member of the second planetary gear set with at least one of the carrier member of the first planetary gear set and the sun gear member of the third planetary gear set;
a fourth torque transmitting mechanism selectively engageable to interconnect at least one of the ring gear member of the first planetary gear set and the ring gear member of the second planetary gear set with the stationary element;
a fifth torque transmitting mechanism selectively engageable to interconnect the sun gear member of the first planetary gear set with the stationary element; and
a sixth torque transmitting mechanism selectively engageable to interconnect the carrier member of the third planetary gear set with the stationary element,
wherein the torque transmitting mechanisms are selectively engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.