Transmission with dual clutch actuation assembly

A vehicle transmission includes an input member, an output member, a plurality of gear sets, first and second clutches, first and second actuators, and first and second bearings. The plurality of gear sets is disposed between the input member and the output member. The first and second clutches are selectively engaged to rotationally couple first and second pairs of the plurality of gear sets. The first and second actuators each have a stationary cylinder bore and a piston disposed in the stationary cylinder bore, where the pistons are substantially rotationally stationary. The first bearing is disposed between the first clutch and the nonrotating piston of the first actuator and the second bearing is disposed between the second clutch and the nonrotating piston of the second actuator.

TECHNICAL FIELD

The present disclosure relates to transmissions, and more particularly to transmissions having clutch actuation assemblies with multiple hydraulic pistons.

BACKGROUND

Automatic transmissions provide a plurality of forward and reverse speeds or gear ratios by selectively actuating one or more brakes or clutches. A concentric slave cylinder assembly having concentric piston rings is often used to actuate two clutches that are located near each other, such as in a dual clutch transmission have two input shafts that each provide a subset of the available gear ratios. Each of the two input shafts is selectively coupled to an engine by use of one of these clutches. The radial stacking of the pistons results in a high linear speed of the outer actuator piston. To accommodate the high linear speed of the outer piston, bearings having high losses and rotating pistons are often used in the concentric slave cylinder assembly. The rotating seals used to accommodate rotating pistons have unfavorable fluid leakage characteristics and the high loss bearings contribute to in higher spin losses in the transmission. Thus, there is a need for a new and improved clutch actuation assembly that has improved bearing loss and fluid leakage characteristics.

SUMMARY

A vehicle transmission includes an input member, an output member, a plurality of gear sets, first and second clutches, first and second actuators, and first and second bearings. The plurality of gear sets is disposed between the input member and the output member. The first and second clutches are selectively engaged to rotationally couple first and second pairs of the plurality of gear sets. The first and second actuators each have a stationary cylinder bore and a piston disposed in the stationary cylinder bore, where the pistons are substantially rotationally stationary. The first bearing is disposed between the first clutch and the nonrotating piston of the first actuator and the second bearing is disposed between the second clutch and the nonrotating piston of the second actuator.

In another aspect of the present invention, the first actuator and the second actuator are axially separated and at least partially aligned in a radial direction.

In yet another aspect of the present invention, a diameter of the nonrotating piston of the first actuator is substantially the same as a diameter of the nonrotating piston of the second actuator.

In yet another aspect of the present invention, the plurality of gear sets includes four planetary gear sets.

In yet another aspect of the present invention, the vehicle transmission further includes first, second, third, and fourth brakes.

In yet another aspect of the present invention, the vehicle transmission further includes an interconnecting member continuously connecting a first rotary member and a seventh rotary member. The plurality of gear sets further includes first, second, third, and fourth planetary gear sets. The first and a second planetary gear set each have a first, a second, and a third member. Each of the first, second, and third members is included in one of the first rotary member, a second rotary member, a third rotary member, and a fourth rotary member, and two of the members of the first planetary gear set are directly separately connected with two of the members of the second planetary gear set to form the first and the second rotary members and the fourth rotary member is directly connected to the input member. The third and a fourth planetary gear set each have a first, a second, and a third member. Each of the first, second, and third members is included in one of a fifth rotary member, a sixth rotary member, the seventh rotary member, and an eighth rotary member. Two of the members of the third planetary gear set are directly separately connected with two of the members of the fourth planetary gear set to form the fifth and sixth rotary members and the sixth rotary member is directly connected to the output member.

In yet another aspect of the present invention, the first clutch is selectively engageable to connect the fourth rotary member with the fifth rotary member.

In yet another aspect of the present invention, the second clutch is selectively engageable to connect the fourth rotary member with the eighth rotary member.

In yet another aspect of the present invention, the first brake is selectively engageable to connect the third rotary member with a stationary member.

In yet another aspect of the present invention, the second brake is selectively engageable to connect the second rotary member with the stationary member.

In yet another aspect of the present invention, the third brake is selectively engageable to connect the first rotary member, the interconnecting member, and the seventh rotary member with the stationary member.

In yet another aspect of the present invention, the fourth brake is selectively engageable to connect the fifth rotary member with the stationary member.

In yet another aspect of the present invention, the third member of the first planetary gear set and the third member of the second planetary gear set form the first rotary member, the second member of the first planetary gear set and the second member of the second planetary gear set form the second rotary member, the first member of the first planetary gear set forms the third rotary member, the first member of the second planetary gear set forms the fourth rotary member, the third member of the third planetary gear set and the third member of the fourth planetary gear set form the fifth rotary member, the second member of the third planetary gear set and the second member of the fourth planetary gear set form the sixth rotary member, the first member of the third planetary gear set forms the seventh rotary member, and the first member of the fourth planetary gear set forms the eighth rotary member.

In yet another aspect of the present invention, the first members of the first, second, third, and fourth planetary gear sets are sun gears, the second member of the first planetary gear set and the second member of the second planetary gear set are combined to form a single ring gear, the second member of the third planetary gear set and the third member of the fourth planetary gear set are ring gears, the third member of the first planetary gear set and the third member of the second planetary gear set are combined to form a single carrier member, and the third member of the third planetary gear set and the second member of the fourth planetary gear set are carrier members.

A clutch actuation assembly includes a first piston assembly and a second piston assembly. The first piston assembly includes a piston, an apply member, and a bearing. The second piston assembly includes a piston, an apply member, and a bearing. The piston of the first piston assembly is axially separated from and at least partially aligned with the piston of the second piston assembly in a radial direction.

In another aspect of the present invention, the bearing members are disposed between the respective apply member and piston of the first and second piston assemblies at an inner radial portion of the piston members.

In yet another aspect of the present invention, the apply members are rotationally coupled with and axially translatable through a hub of the first and second clutches.

In another embodiment of the present invention, a transmission having four planetary gear sets representable by a first lever and a second lever each having four nodes is provided. The transmission includes a first clutch and a second clutch each selectively connectable between an input member and a node of the second lever. The transmission includes a clutch actuation assembly to actuate the first and second clutches. The clutch actuation assembly includes a first piston assembly and a second piston assembly. The first piston assembly includes a piston, an apply member, and a bearing. The second piston assembly includes a piston, an apply member, and a bearing. The piston of the first piston assembly is axially separated from and at least partially aligned with the piston of the second piston assembly in a radial direction.

In another embodiment of the present invention, a transmission having and input and first, second, third, and fourth planetary gear sets each having a sun gear, a carrier member, and a ring gear is provided. The transmission includes a first clutch selectively engageable to rotationally couple the input member with the carrier member of the third planetary gear set and a second clutch selectively engageable to rotationally couple the input member with the sun gear of the fourth planetary gear set. The clutch actuation assembly includes a first piston assembly and a second piston assembly. The first piston assembly includes a piston, an apply member, and a bearing. The second piston assembly includes a piston, an apply member, and a bearing. The piston of the first piston assembly is axially separated from and at least partially aligned with the piston of the second piston assembly in a radial direction.

DESCRIPTION

Referring now toFIG. 1A, an embodiment of a nine 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 with three nodes represents a planetary gear set wherein the three basic mechanical components of the planetary gear set are each represented by a node. Therefore, the three nodes of a three node lever each represent one of a sun gear, a planet gear carrier, and a 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 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. If the device is a brake, one set of the fingers is grounded. Furthermore, multiple gear sets sharing common connections may be combined into a lever having more nodes. For example, two three-node gear sets that share two common connections may be combined into a single four node lever. 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 member12and a first lever11that represents a combination of a first planetary gear set and a second planetary gear set. Thus, two fixed connections are present between the components of the first and second planetary gear set. The first lever11includes a first node A, a second node B, a third node C, and a fourth node D. A second lever13represents a combination of a third planetary gear set and a fourth planetary gear set. Thus, two fixed connections are present between the components of the third and fourth planetary gear set. The second lever13includes a first node E, a second node F, a third node G, and a fourth node H. The first node A of the first lever11is connected for common rotation with the input shaft or member12. The second node F of the second lever13is connected for common rotation with an output shaft or member22. The third node C of the first lever11is connected for common rotation with the fourth node H of the second lever13.

A first clutch26selectively connects the first node A of the first lever11with the third node G of the second lever13. A second clutch28selectively connects the first node A of the first lever11with the first node E of the second lever13. The first and second clutches26,28are actuated by a dual clutch actuation assembly29, as will be described below.

A first brake30selectively connects the fourth node D of the first lever11to a stationary member or a transmission housing40. A second brake32selectively connects the second node B of the first lever11to the stationary member or transmission housing40. A third brake34selectively connects the third node C of the first lever11and the fourth node H of the second lever13to the stationary member or transmission housing40. A fourth brake36selectively connects the third node G of the second lever13to the stationary member or transmission housing40. In the example provided the clutches26,28and brakes30,32,34,36are friction clutches each having first friction members interleaved with second friction members. It should be appreciated that other torque transmitting mechanisms, such as dog clutches, selectable one-way clutches, and bands may be incorporated without departing from the scope of the present invention.

Referring now toFIGS. 1A and 1B, wherein like numbers refer to like components, a transmission10′ is represented by an example of a three node lever diagram that corresponds to the four node diagram ofFIG. 1A. The lever diagram of the transmission10′ has four levers each with three nodes. Each of the three node levers represents a planetary gear set having a sun gear, a ring gear, and a planetary gear carrier. In the example provided, a first gear set11A and a second gear set11B have two continuous connections between each other so that they can be represented by the first lever11ofFIG. 1A. A third gear set13A and a fourth gear set13B have two continuous connections between each other so that they can be represented by the second lever13ofFIG. 1A.

Referring now toFIG. 2, a stick diagram presents a schematic layout of an embodiment of a nine speed transmission100according to the present invention. More specifically, the schematic diagram ofFIG. 2is an example of a planetary gear set configuration according to the four node lever diagram describing the transmission10ofFIG. 1and like numbers refer to like components. The clutches, brakes, and couplings are correspondingly presented whereas the nodes of the levers11,13are now represented by components of planetary gear sets such as sun gears, ring gears, planet gears and planet gear carriers. For example, the first lever11ofFIG. 1is now represented by a first planetary gear set114and a second planetary gear set116that are combined to form a planetary gear set assembly127. The second lever13is now represented by interconnected planetary gear sets120,121. Planetary gear set assembly127includes sun gear members114B/116B and116A, a ring gear member118A, and a planet gear carrier member114A that rotatably supports a first set of planet gears129(only one of which is shown) and a second set of planet gears131(only one of which is shown). The planet gears129are long pinion gears that have a first end129aand a second end129b. The planet gears129are each configured to intermesh with both the sun gear member114B/116B at the first end129aand intermesh with the ring gear member118A and the second set of planet gears131at the second end129b. The second set of planet gears131are each configured to intermesh with both the sun gear member116A and the first set of planet gears129. The sun gear member114B/116B is coupled to an interconnecting member or shaft132. The ring gear member118A is coupled to an interconnecting member of shaft134. The planet carrier member114A is coupled to an interconnecting member or shaft136and an interconnecting member or shaft138. Sun gear member116A is connected for common rotation with the input shaft12and an interconnecting member or shaft140.

Planetary gear set120includes a sun gear member120A, a ring gear member120C, and a planet gear carrier member120B that rotatably supports a plurality of planet gears120D (only one of which is shown). The sun gear member120A is connected for common rotation with the interconnecting member138. The carrier member120B is connected for common rotation with an interconnecting member or shaft142and an interconnecting member or shaft144. The ring gear member120C is connected for common rotation with an interconnecting member or shaft146. The planet gears120D are each intermeshed with both the sun gear member120A and the ring gear member120C.

Planetary gear set121includes a sun gear member121A, a ring gear member121C, and a planet gear carrier member121B that rotatably supports a plurality of planet gears121D (only one of which is shown). The sun gear member121A is connected for common rotation with an interconnecting member or shaft148. The carrier member121B is connected for common rotation with the interconnecting member146and the output shaft22. The ring gear member121C is connected for common rotation with the interconnecting member144. The planet gears121D are each intermeshed with both the sun gear member121A and the ring gear member121C.

The first clutch26selectively connects the interconnecting member140with the interconnecting member142. The second clutch28selectively connects the interconnecting member140with the interconnecting member148. The first brake30selectively connects the interconnecting member132to the housing40in order to restrict rotation of the member132. The second brake32selectively connects the interconnecting member134to the housing40in order to restrict rotation of the member134. The third brake34selectively connects the interconnecting member136with the housing40in order to restrict rotation of the member136. The fourth brake36selectively connects the interconnecting member144with the housing40in order to restrict rotation of the member144.

Referring now toFIG. 3, a truth table presenting the various combinations of torque transmitting mechanisms that are activated or engaged to achieve the various gear states of transmission100is shown. 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 transmission100. 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.

Referring now toFIG. 4, wherein like reference numbers refer to like components, a cross sectional view of the dual clutch actuator assembly29is shown in the transmission100. It should be appreciated that the clutch actuator assembly29may be incorporated in other transmissions without departing from the scope of the present invention. The clutch actuator assembly29includes a first piston assembly202and a second piston assembly204for actuating the first and second clutches26,28. The first piston assembly202is axially separated from and at least partially aligned with the second piston assembly204in a radial direction.

The first piston assembly202includes a piston210, an apply member212, a bearing214, a spring215, and a cylinder216. The piston210is disposed in the cylinder216formed in a separating member217connected to a stationary housing member218. The separating member217projects radially outward from the housing member218near an axial midpoint of the housing member218. The piston210seals against the cylinder216and forms a hydraulic chamber220in combination with the separating member217for actuation of the first piston assembly202. The apply member212rotates with a hub221of the clutches26,28that is rotationally coupled with the input member12. The apply member212includes a first end222adjacent the piston210and a second end224adjacent the first clutch26. The second end224slides axially through an opening in the hub221to compress or release the clutch26. The bearing214is disposed between the first end222of the apply member212and an inner radial portion of the piston210to allow relative rotation between the stationary piston210and the rotating apply member212. The spring215is disposed between the apply member212and the hub221to bias the apply member212away from the clutch26.

The second piston assembly204includes a piston230, an apply member232, a bearing234, a spring235, and a cylinder236. The piston230opposes a back side of the separating member217and the piston230is substantially aligned with the piston210along a radial direction from an axis of the transmission100. Additionally, the bearing234is disposed at a radial distance from the axis of the transmission that is substantially similar to that of the bearing214. The piston230is disposed in the cylinder236that is formed in the stationary housing member218. The piston230seals against the cylinder236and forms a hydraulic chamber240in combination with the housing member218for actuation of the second piston assembly204. The apply member232rotates with the hub221of the clutches26,28and includes a first end242adjacent the piston230and a second end244adjacent the second clutch28. The second end244slides axially through an opening in the hub221to compress or release the clutch28. The bearing234is disposed between the first end242of the apply member232and an inner radial portion of the piston230to allow relative rotation between the stationary piston230and the rotating apply member232. In the example provided, the bearing234is a low loss thrust ball type bearing. The spring235is disposed between the apply member232and the hub221to bias the apply member232away from the clutch28.

Because the second piston assembly204is axially separated from the first piston assembly202, the piston230has a large cross section without interfering with the piston210to allow reduced pressure requirements for a given torque requirement of the clutch28. Additionally, the bearing234is disposed relatively close to an axis of rotation of the transmission100. Accordingly, the linear speed difference between the apply member232and the piston230is reduced relative to radially stacked concentric slave cylinders, and therefore the piston210may remain non-rotating and may include non-rotating seals to provide favorable hydraulic fluid leakage characteristics from the chamber240.

Referring now toFIGS. 2 and 4, the operation of the clutch actuation assembly29will be described. When actuation of the first clutch26is desired, a pressurized hydraulic fluid is directed to the chamber220. The hydraulic fluid presses the piston210away from a base of the cylinder216. The piston210presses the first end222of the apply member212through the bearing214. The second end224of the apply member212compresses the first clutch26to rotationally couple the hub221and input member12to the carrier member of the planetary gear set120. To release the clutch26and allow rotation between the input member12and the carrier member of the planetary gear set120, the hydraulic fluid is evacuated from the chamber220and the spring215presses the apply member212and the piston210away from the clutch26.

When actuation of the second clutch28is desired, a pressurized hydraulic fluid is directed to the chamber240. The hydraulic fluid presses the piston230away from a base of the cylinder236. The piston230presses the first end242of the apply member232through the bearing234. The second end244of the apply member232compresses the second clutch28to rotationally couple the hub221and input member12to the sun gear of the planetary gear set121. To release the clutch28and allow rotation between the input member12and the sun gear of the planetary gear set121, the hydraulic fluid is evacuated from the chamber240and the spring235presses the apply member232and the piston230away from the clutch28.

The present invention provides several beneficial attributes. For example, the assembly provides beneficial spin loss characteristics and a low loss bearing is incorporated due to the low linear speed of the outer bearing. Additionally, the stationary pistons employ non-rotating seals to provide favorable oil leakage characteristics and hydraulic pressure requirements.