Multi-speed transmission having stacked planetary gear sets

#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, two planetary gear set assemblies and a plurality of torque transmitting devices.

#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 sets 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.

#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 a nine speed transmission according to the present invention;

#FIG. 2 is a diagrammatic illustration of an embodiment of a nine speed transmission according to the present invention;

#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 a nine or more 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. 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.

#The transmission 10 includes an input shaft or member 12, a first planetary gear set 14, a second planetary gear set 16, a third planetary gear set 18, a fourth planetary gear set 20 and an output shaft or member 22. The lever of the first planetary gear set 14 has three nodes: a first node 14A, a second node 14B and a third node 14C. The lever of the second planetary gear set 16 has three nodes: a first node 16A, a second node 16B and a third node 16C. The lever of the third planetary gear set 18 has three nodes: a first node 18A, a second node 18B and a third node 18C. The lever of the fourth planetary gear set 20 has three nodes: a first node 20A, a second node 20B and a third node 20C.