Electronic transmission range selection for a continuously variable transmission

A hydraulic control system for a continuously variable transmission (CVT) of a motor vehicle includes a source of pressurized hydraulic fluid that communicates with an electronic transmission range selection (ETRS) subsystem. The ETRS subsystem may include one or more mode valves, a park servo, and a park mechanism. A pressure regulator subsystem is configured to provide a pressurized hydraulic fluid. The ETRS subsystem is in downstream fluid communication with the pressure regulator subsystem and has first and second outputs. The ETRS subsystem has an electronically-activated mode control valve in communication with the mode valve. The mode control valve is operable to move the mode valve between a first position and a second position. The ETRS subsystem is configured to selectively communicate pressurized hydraulic fluid to the forward clutch for the CVT through the first output and to the reverse clutch through the second output.

TECHNICAL FIELD

The present disclosure relates to an electro-hydraulic control system for a continuously variable transmission.

INTRODUCTION

A typical continuously variable transmission (CVT) includes a hydraulic control system that is employed to provide cooling and lubrication to components within the CVT and to actuate torque transmitting devices, such as drive clutches or torque converter clutches, and belt pulley positions. The conventional hydraulic control system typically includes a main pump that provides a pressurized fluid, such as oil, to a plurality of valves and solenoids within a valve body. The main pump is driven by the engine of the motor vehicle. The valves and solenoids are operable to direct the pressurized hydraulic fluid through a hydraulic fluid circuit to various subsystems including lubrication subsystems, cooler subsystems, torque converter clutch control subsystems, and pulley actuator subsystems that include actuators configured to engage the torque transmitting devices and the pulleys that move the belt of the CVT. The pressurized hydraulic fluid delivered to the pulleys is used to position the belt relative to input and output variators in order to obtain different pulley ratios.

While previous hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within CVTs which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness, is essentially constant. Accordingly, there is a need for an improved, cost-effective hydraulic control system for use in a hydraulically actuated CVT.

SUMMARY

A hydraulic control system with clutch control for a CVT is provided. The hydraulic control system includes a pressure regulator subsystem configured to provide pressurized hydraulic fluid, and an electronic range selection subsystem configured to selectively communicate the pressurized hydraulic fluid to the forward clutch and the reverse clutch. The electronic range selection subsystem may include two mode valves, wherein each mode valve is independently actuatable. In some forms, the mode valves are moveable, and confirmation of their position can be measured, prior to flowing pressurized hydraulic fluid to the mode valves. In addition, a clutch fault valve may be provided to provide pressurized hydraulic fluid to the electronic range selection subsystem in the case of a default.

In one form, which may be combined with or separate from other forms disclosed herein, a hydraulic control system for a propulsion system of a motor vehicle is provided, where the propulsion system has a continuously variable transmission, a forward clutch, and a reverse clutch. The hydraulic control system includes a pressure regulator subsystem configured to provide a pressurized hydraulic fluid. An electronic range selection subsystem is provided in downstream fluid communication with the pressure regulator subsystem and has first and second outputs. The electronic range selection subsystem has a mode valve and an electronically-activated mode control valve in communication with the mode valve. The mode control valve is operable to move the mode valve between a first position and a second position. The electronic range selection subsystem is configured to selectively communicate pressurized hydraulic fluid to the forward clutch through the first output and to the reverse clutch through the second output. A first pulley valve is provided and is configured to regulate fluid pressure to a primary pulley. The first pulley valve is actuatable by an electronically-activated primary pulley control valve. A second pulley valve is configured to regulate fluid pressure to a secondary pulley. The secondary pulley valve is actuatable by an electronically-activated secondary pulley control valve.

In another form, which may be combined with or separate from the other forms disclosed herein, a hydraulic control system for a propulsion system of a motor vehicle is provided, wherein the propulsion system has a continuously variable transmission, a forward clutch, and a reverse clutch. The hydraulic control system includes a pressure regulator subsystem configured to provide a pressurized hydraulic fluid and an electronic range selection subsystem in downstream fluid communication with the pressure regulator subsystem. The electronic range selection subsystem has first and second outputs, a first mode valve, and an electronically-activated first mode control valve in communication with the first mode valve. The first mode control valve is operable to move the first mode valve between a first position and a second position. The electronic range selection subsystem also has a second mode valve and an electronically-activated second mode control valve in communication with the second mode valve. The second mode control valve is operable to move the second mode valve between a first position and a second position. The electronic range selection subsystem is configured to selectively communicate pressurized hydraulic fluid to the forward clutch through the first output and to the reverse clutch through the second output. The electronic range selection subsystem has a range enablement valve configured to supply pressurized hydraulic fluid to the first and second mode valves. The range enablement valve is actuatable independently of the first and second mode valves.

In yet another form, a hydraulic control system for a propulsion system of a motor vehicle is provided, wherein the propulsion system has a continuously variable transmission, a forward clutch, and a reverse clutch. The hydraulic control system includes a pressure regulator subsystem configured to provide a pressurized hydraulic fluid and an electronic range selection subsystem in downstream fluid communication with the pressure regulator subsystem. The electronic range selection subsystem has first and second outputs, a first mode valve, and an electronically-activated first mode control valve in communication with the first mode valve. The first mode control valve is operable to move the first mode valve between a first position and a second position. The electronic range selection subsystem also has a second mode valve and an electronically-activated second mode control valve in communication with the second mode valve. The second mode control valve is operable to move the second mode valve between a first position and a second position. The electronic range selection subsystem is configured to selectively communicate pressurized hydraulic fluid to the forward clutch through the first output and to the reverse clutch through the second output. The electronic range selection subsystem has a range enablement valve configured to supply pressurized hydraulic fluid to the first and second mode valves. The hydraulic control system has a primary clutch pressure regulation valve and a clutch default valve in fluid communication with the primary clutch pressure regulation valve. The clutch default valve is actuatable by a normally high control solenoid.

Additional features may be provided, including but not limited to the following: a second mode valve; an electronically-activated second mode control valve in communication with the second mode valve; the second mode control valve being operable to move the second mode valve between a first position and a second position; a range enablement valve configured to supply pressurized hydraulic fluid to the first and second mode valves; the range enablement valve being actuatable independently of the first and second mode valves; a primary clutch pressure regulation valve; a clutch default valve in fluid communication with the primary clutch pressure regulation valve; the clutch default valve being actuatable by a normally high solenoid control valve; the clutch default valve being configured to supply pressured hydraulic fluid to the electronic range selection subsystem upon default; the hydraulic control system being configured to default into a forward drive mode if a default occurs while the forward clutch is in the forward drive mode; a clutch control solenoid valve configured to actuate the primary clutch pressure regulation valve; the clutch control solenoid valve being normally high; the electronic range selection subsystem being configured to communicate pressurized hydraulic fluid to the reverse clutch through the second output when the first mode valve is in the first position and the second mode valve is in the second position; and the electronic range selection subsystem being configured to communicate pressurized hydraulic fluid to the forward clutch through the first outlet when the first mode valve is in the second position and the second mode valve is in the first position.

Further additional features may be provided, including but not limited to the following: a torque converter control valve connected to a torque converter clutch and a cooler subsystem; the torque converter control valve being moveable between an apply position configured to communicate pressurized hydraulic fluid to an apply side of the torque converter clutch and a release position configured to communicate pressurized hydraulic fluid with a release side of the torque converter clutch and with the cooler subsystem; a torque converter clutch pressure regulator valve; a torque converter clutch control solenoid valve; the torque converter clutch pressure regulator valve being disposed downstream of the torque converter clutch control solenoid valve and the pressure regulator subsystem and upstream of the torque converter control valve; and the torque converter clutch pressure regulator valve being configured to regulate a pressure of hydraulic fluid supplied by the pressure regulator subsystem and provided to the torque converter control valve based on an output from the torque converter clutch control solenoid valve.

Still further additional features may be provided, including but not limited to the following: the hydraulic control system having a park mode and an out-of-park mode of operation; a park servo in downstream fluid communication with the first mode valve and the second mode valve; the park servo being moveable between a park position and an out-of-park position; the park servo being actuatable by a park control solenoid valve that is moveable between a first position and a second position; a park lock mechanism mechanically coupled to the park servo; the park servo being configured to mechanically move the park lock mechanism to place the hydraulic control system in the park mode when the first mode valve is in the first position, the second mode valve is in the first position, and the park control solenoid valve is in the first position; and the park servo being configured to move the park lock mechanism to place the transmission in the out-of-park mode when at least one of the first mode valve, the second mode valve, and the park control solenoid valve is in the second position.

Further aspects, advantages, and areas of applicability will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.

DESCRIPTION

With reference toFIG. 1, a motor vehicle is illustrated and generally indicated by reference number5. The motor vehicle5is illustrated as a passenger car, but it should be appreciated that the motor vehicle5may be any type of vehicle, such as a truck, van, sport-utility vehicle, etc. The motor vehicle5includes an exemplary propulsion system10. It should be appreciated at the outset that while a rear-wheel drive propulsion system has been illustrated, the motor vehicle5may have a front-wheel drive propulsion system without departing from the scope of the present invention. The propulsion system10generally includes an engine12interconnected with a transmission14.

The engine12may be a conventional internal combustion engine or an electric engine, hybrid engine, or any other type of prime mover, without departing from the scope of the present disclosure. The engine12supplies a driving torque to the transmission14through a torque converter16. The torque converter16includes a torque converter clutch18that, when applied or engaged, mechanically couples the output of the engine12to the input of the transmission14.

The transmission14is preferably a continuously variable transmission and has a typically cast, metal housing19which encloses and protects the various components of the transmission14. The housing19includes a variety of apertures, passageways, shoulders and flanges which position and support these components. Generally speaking, the transmission14includes a transmission input shaft20and a transmission output shaft22. Disposed between the transmission input shaft20and the transmission output shaft22is a powerflow arrangement24of gears, clutches, and pulleys. The transmission input shaft20is functionally interconnected with the engine12via the torque converter16and receives input torque or power from the engine12. The transmission output shaft22is preferably connected with a final drive unit26which includes, for example, propshaft28, differential assembly30, and drive axles32connected to wheels33. The transmission input shaft20is coupled to and provides drive torque to the powerflow arrangement24.

The powerflow arrangement24generally includes a forward clutch34, a reverse clutch or brake36, and a pulley assembly38. The powerflow arrangement24may also include a plurality of gear sets, a plurality of shafts, and additional clutches or brakes. The plurality of gear sets may include individual intermeshing gears, such as planetary gear sets, that are connected to or selectively connectable to the plurality of shafts through the selective actuation of the plurality of clutches/brakes. The plurality of shafts may include layshafts or countershafts, sleeve and center shafts, reverse or idle shafts, or combinations thereof. The forward clutch34is selectively engageable to initiate a forward drive mode while the reverse clutch or brake36is selectively engageable to initiate a reverse drive mode. The pulley assembly38is a continuously variable unit that includes a chain or belt wrapped between a primary pulley and a secondary pulley (not shown). Translation of the pulleys correlates to movement of the belt or chain which continuously varies the output or pulley ratio of the transmission14.

The transmission14includes a transmission control module40. The transmission control module40is preferably an electronic control device having a preprogrammed digital computer or processor, control logic or circuits, memory used to store data, and at least one I/O peripheral. The control logic includes or enables a plurality of logic routines for monitoring, manipulating, and generating data and control signals. The transmission control module40controls the actuation of the forward clutch34, the reverse clutch or brake36, the pulley assembly38, and the torque converter clutch18via a hydraulic control system100. In another example, the transmission control module40is an engine control module (ECM), or a hybrid control module, or any other type of controller.

The hydraulic control system100is disposed within a valve body101that contains and houses via fluid paths and valve bores most of the components of the hydraulic control system100. These components include, but are not limited to, pressure regulation valves, directional valves, solenoid control valves, etc. The valve body101may be attached to a bottom of the transmission housing19in rear-wheel drive transmissions or attached to a front of the transmission housing19in front-wheel drive transmissions, by way of example. The hydraulic control system100is operable to selectively engage the clutches/brakes34,36,18and to provide cooling and lubrication to the transmission14by selectively communicating a hydraulic fluid from a sump102under pressure from either an engine driven pump103or an accumulator (not shown). The pump103may be driven by the engine12or by an auxiliary engine or electric motor.

With reference toFIGS. 2A-2B, a portion of the hydraulic control system100is illustrated. The hydraulic control system100generally includes a plurality of interconnected or hydraulically communicating subsystems including an electronic transmission range selection (ETRS) control subsystem104, a pressure regulator subsystem106, an actuator feed subsystem108, and a torque converter clutch control subsystem110. The hydraulic control system100may also include various other subsystems or modules, such as a lubrication subsystem, without departing from the scope of the present disclosure.

The pressure regulator subsystem106is operable to provide and regulate pressurized hydraulic fluid, such as transmission oil, throughout the hydraulic control system100. The pressure regulator subsystem106draws hydraulic fluid from the sump102. The sump102is a tank or reservoir preferably disposed at the bottom of the transmission housing19to which the hydraulic fluid returns and collects from various components and regions of the transmission14. The hydraulic fluid is forced from the sump102and communicated throughout the hydraulic control system100via the transmission fluid pump103. The transmission fluid pump103may be, for example, a gear pump, a vane pump, a gerotor pump, or any other positive displacement pump. The pressure regulator subsystem106may also include an alternate source of hydraulic fluid that includes an auxiliary pump140preferably driven by an electric engine, motor, battery, or other prime mover (not shown), or an accumulator. The auxiliary pump140may be included to provide line pressure in, for example, start/stop applications, if desired. The hydraulic fluid from the transmission fluid pump103is controlled by a pressure regulator valve112. The pressure regulator valve112regulates the pressure of the hydraulic fluid from the transmission fluid pump103and feeds pressurized hydraulic fluid to a converter feed line114. The pressure regulator subsystem106may also include various other valves and solenoids without departing from the scope of the present disclosure.

For example, the line pressure regulator valve includes ports112A-E, numbered consecutively from left to right inFIG. 2B. Port112A communicates with a line pressure signal line113from a line pressure control solenoid valve134. Port112B communicates with the converter feed line114. Ports112C and112F communicate with line pressure126. Port112D communicates with a bypass circuit119. Port112E is an exhaust port. The pressure regulator valve112further includes a spool valve121slidably disposed within a bore123formed in the valve body101. The spool valve121is moveable against a biasing member125, such as a coiled spring, to control line pressure.

The pressure regulator valve112regulates the flow and/or pressure of the transmission fluid to a primary pulley valve122, a secondary pulley valve124, and/or for one or more other actuators/functions, such as the torque converter16and other valves within the hydraulic control system100. The pressure regulator valve112may also provide fluid from the transmission fluid pump103for cooling and lubrication. One output pressure of the pressure regulator valve112may be referred to as a line pressure126.

The transmission fluid pump103outputs transmission fluid to the pressure regulator valve112through a first fluid path116, and the transmission fluid pump103also outputs the transmission fluid to a switching valve118via a second fluid path120. The switching valve has a spool127slidably disposed within a bore129, which is biased into a first position by a biasing member131, such as a spring.

When the switching valve118is open (in a second position), the transmission fluid flows from the transmission fluid pump103through the switching valve118to the pressure regulator valve112. In various implementations, the switching valve118may be integrated within the transmission fluid pump103. When the switching valve118is closed (in a first position), the second fluid path120is connected back to pump suction.

When the switching valve118is in the closed position, or the first position, the switching valve118blocks transmission fluid flow through the second fluid path120and connects the second path120to pump suction, so that the transmission fluid pump103pumps transmission fluid to the pressure regulator valve112only through the first fluid path116, and the transmission fluid pump103operates in a partial (e.g., half) mode operation. Since the transmission fluid pump103is driven by the engine12, a fuel efficiency increase (i.e., a fuel consumption decrease) of the engine12may be realized (relative to full mode operation) during operation in the partial mode as the transmission fluid pump103imposes a lesser torque load on the engine12.

When the switching valve118is in the open position, or the second position, pressurized hydraulic fluid is provided to the spool127through the signal line133to compress the spool127against the spring131, and the transmission fluid pump103operates in a full mode operation. The switching valve118enables transmission fluid flow through the second fluid path120when in the open position, so that the transmission fluid pump103pumps transmission fluid to the pressure regulator valve112through both of the first fluid path116and the second fluid path120.

The switching valve118may be controlled to transition from the closed position to the open position under various circumstances. For example only, the switching valve118may be transitioned from the closed position to the open position when a rate of change of the target ratio between the input and output shafts20,22is greater than a predetermined value. In another example, the switching valve118may be transitioned from the open position to the closed position when a rate of change of the target ratio between the input and output shafts20,22is less than a predetermined value.

The actuator feed subsystem108provides hydraulic fluid to various control devices or actuators, such as solenoids, throughout the hydraulic control system100. The actuator feed subsystem108includes a feed limit valve115that controls or limits the pressure of hydraulic fluid supplied to the actuators. For example, the feed limit valve115is configured to provide fluid to a binary solenoid control valve132, a line pressure control solenoid control valve134, a primary pulley solenoid control valve136, a secondary pulley solenoid control valve138, a TCC control solenoid control valve142, a clutch control solenoid control valve144, a first mode solenoid control valve146, and/or a second mode solenoid control valve148. Each of the solenoid control valves132,134,136,138,142,144,146,148may be, for example, VBS or VFS valves that may be normally high or normally low. In one example, each of the solenoid control valves132,134,136,138,144may be normally high, and each of the solenoid control valves142,146,148may be normally low. Each of the solenoid control valves132,134,136,138,142,144,146,148may be electrically-activated. In other examples, the control valves132,134,136,138,142,144,146,148may be another type of control valve that does not include a solenoid, and which may be electrically-activated.

The primary pulley valve122, controlled and actuated by the electrically-activated primary pulley solenoid control valve136, regulates the flow (and pressure) of the transmission fluid to the primary pulley34. For example, the primary pulley valve122may be opened to increase the flow/pressure of the transmission fluid to the primary pulley34to expand the primary pulley34and change the pulley ratio of the primary pulley34. The primary pulley valve122may be closed to decrease the flow/pressure of the transmission fluid to the primary pulley34to contract the primary pulley34and change the pulley ratio of the primary pulley34. An output pressure of the primary pulley valve122may be referred to as a primary pulley pressure128.

The secondary pulley valve124, controlled and actuated by the electrically-activated secondary pulley solenoid control valve138, regulates the flow (and pressure) of the transmission fluid to the secondary pulley36. For example, the secondary pulley valve124may be opened to increase the flow of the transmission fluid to the secondary pulley36to expand the secondary pulley36and change the pulley ratio of the secondary pulley36. The secondary pulley valve124may be closed to decrease the flow of the transmission fluid to the secondary pulley36to contract the secondary pulley36and change the pulley ratio of the secondary pulley36. An output pressure of the secondary pulley valve124may be referred to as a secondary pulley pressure130.

The torque converter clutch control subsystem110controls the engagement of the torque converter clutch18and cooling of the torque converter16. The torque converter clutch control subsystem110generally includes a torque converter clutch (TCC) fault valve150, a TCC pressure regulation valve152, a torque converter control valve154, and the TCC solenoid control valve142.

The TCC fault valve150includes ports150A-E, numbered consecutively from left to right inFIG. 2A. Ports150A and150B are exhaust ports that communicate with the sump102or an exhaust backfill circuit (not shown). Port150C is connected to the torque converter control valve154via a fluid line156. Port150D is connected to and receives pressurized hydraulic fluid from the converter feed line114. Port150E is connected to the TCC solenoid control valve142via a signal line158. The TCC fault valve150further includes a spool valve160slidably disposed within a bore161formed in the valve body101. The spool valve160is moveable between a boost position with the spool valve160moved to the left as shown inFIG. 2A, and a failsafe position with the spool valve160moved to the right. A biasing member164, such as a coiled spring, biases the spool valve160to the failsafe position. Hydraulic fluid from the TCC solenoid control valve142, via signal line158, moves the spool valve160to the boost position. In the boost position, port150B communicates with port150C and port150D is closed off. In the failsafe position, port150C communicates with port150D, and port150B is closed off.

The TCC pressure regulation valve152regulates hydraulic fluid pressure communicated to the torque converter control valve154. The TCC pressure regulation valve152includes fluid ports152A-E, numbered from left to right inFIG. 2B. Port152A is connected to the signal line158. Fluid port152B is connected to and receives hydraulic fluid from the actuator feed line117. Ports152C and152E are connected to a fluid line166. Port152D is an exhaust port. A regulation valve168is positioned within the TCC pressure regulation valve152. The regulation valve168regulates the pressure of hydraulic fluid communicated from port152B to port152C, and therefore to the torque converter control valve154via fluid line166. The regulation valve168is positioned by a pressure signal sent from the TCC solenoid control valve142via port152A. The TCC solenoid control valve142commands a fluid pressure by sending pressurized hydraulic fluid to port152A to act on the regulation valve168. Simultaneously, hydraulic fluid from port152C feeds back on the regulation valve168via port152E and acts on the opposite side of the regulation valve168. Pressure balance between the commanded pressure from the TCC solenoid control valve142, pressure within the fluid line166, and a spring170is achieved as the regulation valve168moves and allows selective communication between ports152B and152C.

The torque converter control valve154controls the engagement of the torque converter clutch18within the torque converter16. The torque converter control valve154includes ports154A-I, numbered consecutively from left to right inFIG. 2A. Port154A is connected to the signal line158. Port154B is connected to the fluid line156. Port154C is connected to a TCC release line172. The TCC release line172communicates with a blow-off valve174and with a release side of the torque converter clutch18. Ports154D and154E communicate with parallel branches114A and114B of the converter feed line114. Port154F communicates with a cooler line176. The cooler line176communicates with a cooler178and a filter180disposed in series with one another. The cooler178reduces a temperature of hydraulic fluid flowing through the filter180, as is known in the art. A blow-off valve182is disposed in parallel with the filter180. Hydraulic fluid from the cooler178and filter180communicate through a lubrication circuit184with the sump102. Port154G is connected to a TCC apply line186. The TCC apply line186communicates with an apply side of the torque converter clutch18. Port154H communicates with the TCC pressure regulator valve152via fluid line166. Port154I communicates with fluid line188, which will be described in further detail below.

The torque converter control valve154includes a spool valve190slidably disposed within a bore192formed in the valve body101. The spool valve190is moveable between an apply position with the spool valve190moved to the right as shown inFIG. 2A, and a release position with the spool valve190moved to the left. A biasing member194, such as a coiled spring, biases the spool valve190to the release position. Hydraulic fluid from the TCC control solenoid valve142, via signal line158, moves the spool valve190to the apply position. In the release position, ports154B,154E, and154H are blocked, port154C communicates with port154D, and port154F communicates with port154G. In the apply position, port154B communicates with port154C, port154D is blocked, port154E communicates with port154F, and port154G communicates with port154H.

The TCC control solenoid valve142is configured to control the position of the TCC pressure regulator valve152and to move the TCC fault valve150. The TCC control solenoid valve142is preferably a normally low solenoid, as stated above. The TCC control solenoid valve142is in electrical communication with the transmission control module40.

The ETRS control subsystem104controls the forward and reverse clutches34,36and a park control valve268. Generally, the ETRS control subsystem104converts electronic input for a requested range selection (Drive, Reverse, Park) into hydraulic and mechanical commands. The mechanical commands include engaging and disengaging a park mechanism114.

The ETRS control subsystem104includes a range enablement valve194, a clutch default valve204, and first and second mode valves206,208. The range enablement valve194includes fluid ports194A-D. Fluid port194A is in communication with the line pressure signal line113. Fluid port194B is in communication with the actuator feed line117. Fluid port194C communicates with a range feed line196. Fluid port194D is an exhaust port that communicates with the sump102or an exhaust backfill circuit. The range enablement valve194further includes a spool valve198slidably disposed within a bore200. When pressurized fluid is supplied through the signal line113, fluid pressure acts upon the spool valve198through the fluid port194A and moves the spool valve198against a spring202into a stroked or enabled position, by way of example. The spool valve198is actuated to a de-stroked position by the spring202. When the spool valve198is stroked, the fluid port194B communicates with the fluid port194C. When the spool valve198is in the de-stroked position, the fluid port194B is blocked. The range enablement valve194is configured to cut off hydraulic fluid to the clutches34,36and to a park assembly203until a safe mode valve position is achieved with the first and second mode valves206,208.

The range feed line196communicates with the clutch default valve204and with the first mode valve206. The clutch default valve204has fluid ports204A-E, numbered from left to right inFIG. 2A. Fluid port204A is in communication with the signal line133. Fluid ports204B and204E are exhaust ports that communicate with the sump102or an exhaust backfill circuit. Fluid port204C communicates with a fluid line188. Fluid port204D communicates with range feed line196. The clutch fault valve204further includes a spool valve210slidably disposed within a bore212. When pressurized hydraulic fluid is supplied through the signal line133, fluid pressure acts upon the spool valve210through the fluid port204A and moves the spool valve210against a spring214into a stroked or enabled position, by way of example. The spool valve210is actuated to a de-stroked position by the spring214. When the spool valve210is stroked, the fluid port204C communicates with the fluid port204D, bringing fluid line188into communication with the range feed line196. When the spool valve210is in the de-stroked position, the fluid port204D is blocked, and the fluid port204C communicates with exhaust (fluid port204B). The clutch default valve204provides a secondary means of activating the clutches34,36, for “limp home protection,” which is described in greater detail below.

The primary clutch pressure regulation valve is generally designated at216. The primary clutch pressure regulation valve216is configured to drive the forward and reverse clutches through the mode valves206,208. The primary clutch pressure regulation valve216regulates hydraulic fluid pressure communicated to the mode valves206,208. The primary clutch pressure regulation valve216has fluid ports A-E, numbered from left to right inFIG. 2A. Port216A is connected to a signal line218that is actuatable by the clutch control solenoid valve144. Port216B communicates with the fluid line188, which is also in communication with the clutch fault valve204and the torque converter control valve154, as explained above. Ports216C and216E communicate with a feed line220to the first mode valve206. Fluid port216D communicates with the range enable fluid line196.

A regulation valve222is positioned within the primary clutch pressure regulation valve216. The regulation valve222regulates the pressure of hydraulic fluid communicated from port216B to port216C, and therefore to the first mode valve206. The regulation valve222is positioned by a pressure signal sent from the clutch control solenoid valve144via fluid line218to port216A. Simultaneously, pressurized hydraulic fluid from port216C feeds back on the regulation valve222via port216E and acts on the opposite side of the regulation valve222. Pressure balance between the commanded pressure from the clutch control solenoid144, pressure within the fluid line220, and a spring224is achieved as the regulation valve222moves and allows selective communication between ports216C and216E.

The first and second mode valve assemblies206,208communicate in series with one another and with the range enablement valve194. The first mode valve206includes ports206A-M, numbered consecutively from left to right. Ports206B, D, H, L, and M are exhaust ports that communicate with the sump102or an exhaust backfill circuit. Ports206A communicates with a drive clutch actuation and feedback line226. Port206C communicates with a first mode signal line228that is pressured by electronic actuation of the first mode solenoid valve146. Port206E communicates with an out-of-park feed line230. Port206F communicates with the range enable feed line196. Port206G communicates with a return-to-park fluid line232. Port206I communicates with a fluid line234. Port206J communicates with the first mode valve feed line220. Port206K communicates with a reverse feed line236.

The first mode valve assembly206further includes spool valves238A and238B slidably disposed within a bore240. The spool valves238A,238B are actuated by the hydraulic fluid provided through lines228and226. A biasing spring239is disposed on the right end of the spool valve238B, which biases the spool valves238A,238B to the left in the orientation ofFIG. 2A. The spool valves238A,238B are moveable between a first position (as shown inFIG. 2A), and a second position in which the spool valve238A is moved to the right in the orientation ofFIG. 2A. In the first position, port206E communicates with port206D and is exhausted; port206F communicates with port206G; port206I communicates with port206H and is exhausted; and port206J communicates with port206K, connecting fluid line220with reverse feed line236. To move the first mode valve assembly206from the first position to the second position, signal line fluid from fluid line228fills up area242, causing the spool valve238A to move to the right. In the second position, fluid port206E communicates with fluid port206F such that the range enable line196communicates with the out-of-park feed line230; fluid port206G communicates with fluid port206H and is exhausted; fluid port206I communicates with fluid port206J, thereby connecting the forward feed line234to the fluid line220; and fluid port206K communicates with fluid port206L and is exhausted.

The second mode valve assembly208generally includes ports208A-L. Fluid port208A communicates with a second mode signal line244that is pressurized by electronic actuation of the second mode solenoid valve148. Ports208B,208F,208I, and208L are exhaust ports that communicate with the sump102or an exhaust backfill circuit. Port208C communicates with a reverse out-of-park feed line246. Port208D communicates with the fluid line232. Port208E communicates with a return-to-park feed line248. Port208G communicates with the forward feed line234. Port208H communicates with the drive clutch actuation and feedback line226, which is connected to a forward clutch actuation circuit249configured to actuate the forward clutch34. Port208J communicates with a reverse clutch actuation line250that is connected to a reverse clutch actuation circuit252configured to actuate the reverse clutch36.

The second mode valve assembly208includes one or more spool valve254slidably disposed within a bore256. The spool valve254is moveable between a first position and a second position. In the first position (shown inFIG. 2A), port208C communicates with port208B and is exhausted; port208D communicates with port208E, thereby connecting fluid line232with return-to-park feed line248; port208G communicates with port208H, thereby connecting forward feed line234with the drive clutch actuation and feedback line226; and port208J communicates with port208I and is exhausted. Port208K is blocked. A biasing spring255is disposed on the right end of the spool valve254, which biases the spool valve254to the left in the orientation ofFIG. 2A.

To move the spool valve254to the second position (to the right in the configuration ofFIG. 2A), fluid is fed through signal line244to port208A, which is accomplished by energizing (or deenergizing) solenoid valve148. In the second position, port208C communicates with port208D, thereby connecting the fluid line232with the reverse out-of-park feed line246; port208E communicates with port208F and is exhausted; port208G is closed off; port208H communicates with port208I and is exhausted; and port208J communicates with port208K, thereby connecting the reverse feed line236with the reverse clutch actuation line250.

Therefore, when the first mode valve206is in the “stroked” position, or second position, while the second mode valve208remains in the “destroked” position, or first position, the transmission is in “Drive,” which is a forward drive mode. When the first mode valve206is in the “destroked” position, or first position, while the second mode valve208is in the “stroked” position, or second position, the transmission is in “reverse.”

The first mode valve assembly206may include one, two, or more position sensors260, and the second mode valve assembly208may include one, two, or more position sensors262, by way of example, which are configured to determine the position of the spools238A,254within the mode valves206,208, respectively.

A check valve264may be connected to fluid lines230and246. The check valve264includes three ports264A-C. Port264A is connected to the reverse out-of-park feed line246. Port264B is connected to the forward out-of-park feed line230. Port or outlet264C is connected to an out-of-park (OOP) fluid line266. The check valve264closes off whichever of the ports264A and264B is delivering the lower hydraulic pressure and provides communication between the outlet port264C and whichever of the ports264A and264B has or is delivering higher hydraulic pressure.

The return-to-park feed line248and the OOP fluid line266each communicate with a Park actuation valve268, which may be a servo valve. The Park actuation valve268includes ports268A and268B, each located on either side of a piston270. The piston270is mechanically coupled to the park mechanism114, which may include a park pawl configured to engage a park gear (not shown). Port268A communicates with the OOP fluid line266, and port268B communicates with the return-to-park fluid line248. The piston270moves upon contact by the pressurized hydraulic fluid supplied by one of the fluid lines266,248, thereby mechanically disengaging or engaging the park mechanism114. A bias spring returns the piston270back to park without hydraulic assistance.

The park mechanism114is connected with an out-of-park (OOP) solenoid272, also referred to as a park inhibit solenoid assembly (PISA). The OOP solenoid272is actuatable to mechanically prevent the park mechanism114from engaging during an engine stop-start event (i.e. when the vehicle is intended to be mobile during an automatic engine stop). The OOP solenoid272may also be used to hold the park servo valve268disengaged when it is desirable to operate out of Park at other times (such as in Neutral).

The park actuation valve assembly268may also include one, two, or more position sensors within a position switch assembly269, by way of example, which are configured to determine the position of the park mechanism114.

As noted above, the ETRS subsystem104feeds pressurized hydraulic fluid to the forward clutch actuation circuit249and/or the reverse clutch actuation circuit252via the clutch regulation line220and either the drive clutch actuation and feedback line226or the reverse clutch actuation line250. The drive clutch actuation and feedback line226also feeds back to the first mode valve206at port206A to latch the first mode valve206in the second position, or the “1” position, therefore latching the transmission14in the forward drive mode.

Referring toFIG. 3, each of the mode valves206,208and the OOP solenoid272are moveable between a first position, indicated by a “0” inFIG. 3, and a second position, indicated by a “1” inFIG. 3. Depending on the position of each of the mode valves206,208and the OOP solenoid272, the transmission may be in (forward) drive, reverse, park, or neutral. For example, when each of the mode valves206,208and the OOP solenoid272are in the first position, or the “0” position, the transmission14is in park. When each of the mode valves206,208is in the first position, or the “0” position, but the OOP solenoid272is in the second position, or the “1” position, the transmission14is in neutral. In addition, when each of the mode valves206,208is in the second position, or the “1” position, the transmission14is also in neutral, regardless of whether the OOP solenoid272is in the “0” or “1” position.

In fact, when either or both of the mode valves206,208is placed in the second position, or the “1” position, the range state of the transmission14does not depend on the position of the OOP solenoid272. Thus, when the first mode valve206is in the first position, or the “0” position, and the second mode valve208is in the second position, or the “1” position, the transmission14is in reverse, regardless of the position of the OOP solenoid272. Similarly, but reversed, when the first mode valve206is in the second position, or the “1” position, and the second mode valve208is in the first position, or the “0” position, the transmission14is in drive, or the forward drive mode, regardless of the position of the OOP solenoid272.

Each of the mode valves206,208has its own dedicated solenoid actuator valve146,148. Thus, each of the mode valves206,208can be moved independently of, and prior to, enabling the mode valves206,208with the range enable valve194. Each of the mode valves206,208may be enabled independently of the position of the range enable valve194. Therefore, each mode valve206,208may be moved and its position confirmed by its respective position sensor260,262prior to providing pressurized hydraulic fluid to the clutch pressure regulation valve216, the clutch actuation circuits249,252, and the park mechanism114.

In the event of a default or loss of power to the transmission controller, the hydraulic system100defaults to drive as long as the transmission14is in drive when the default occurs. The range enable valve194feeds the clutch default valve204, the clutch regulator valve216, and the mode 1 valve206. The clutch control solenoid144(that controls the feed line218to the primary clutch regulation valve216) is normally high. Accordingly, in an event that the clutch control solenoid144loses power, the solenoid144will cause the primary clutch regulation valve216to continue to feed the first mode valve206. Further, the binary solenoid valve132is also normally high and continues to allow the feed line133to provide the signal pressure to the clutch default valve204, which actuates the clutch default valve204to connect the feed line188with the enablement feed line196to provide feed pressure ultimately to the forward clutch actuation circuit249, because the first mode valve206is latched in the engaged “1” position by the drive feedback line226and therefore the pressured fluid from the enablement feed line196is connected to the OOP line230through ports206E and206F to keep the transmission14out of park. Thus, the clutch default valve194provides for “limp home protection” so that a driver is not immediately stranded upon a default or loss of power.

Thus, in the forward drive mode of operation, the hydraulic control system100defaults to drive. In park, reverse, or neutral, the hydraulic system100defaults to park. More particularly, the first mode valve206is in its first position “0” instead of its second position “1.” Therefore, the first mode valve206has the drive feed line234exhausted. Accordingly, in the event of a default, the drive feed line234does not feed the forward clutch actuation circuit249. In park, the second mode valve208is also in its first “0” position.

In the event of a loss of power or default while in reverse, the first mode valve134is in the first “0” position with the drive feed line234exhausted and not feeding pressure to the forward clutch actuation circuit249, but the second mode valve208is in the second “1” position, feeding reverse line236fluid to the reverse clutch actuation circuit252; however, because the mode valve control solenoids146,148are normally low, and the second mode valve208is not latched in the second position, the second mode valve208will return to the first “0” position upon a loss of power. As such, even though the range enablement feed line196is pressurized upon default, the range enablement feed line196is merely connected ultimately to the return-to-park feed line248to return the transmission14to park. The park engagement mechanism114may be configured to ratchet along the park gear if the vehicle5is traveling above a certain speed, such as 5 mph, to slow down the vehicle5before bringing the vehicle5to a stop if a default occurs while the hydraulic control system100is in reverse.

Neutral follows a similar scheme as park and reverse. In neutral low, the first and second mode valves206,208are in the first “0” position, and the OOP solenoid272is in an energized “1” position. Once the OOP solenoid272loses power, it reverts to the deenergized “0” position, and referring toFIG. 3, the configuration for park is then achieved, which each of the valves206,208,272being in the “0” position. In neutral high, where the first and second mode valves206,208are in the second “1” position and the OOP solenoid valve272is in the “0” deenergized state, park is achieved upon default because the first mode valve206does not latch when the second mode valve208is in the second “1” position. (Instead, the clutch actuation drive line226is exhausted through port208I.) Accordingly, upon default, both of the mode valves206,208return to the first “0” position, and with the OOP solenoid272also being in the first “0” position, park is achieved, as shown inFIG. 3.

It should be appreciated that other orifice and check ball arrangements can be used without departing from the scope of present invention, including a single orifice for fill and exhaust, or filling through a single orifice and exhausting through two orifices. Likewise while individual fluid lines have been described, it should be appreciated that fluid lines, flow paths, passageways, etc., may contain other shapes, sizes, cross-sections, and have additional or fewer branches without departing from the scope of the present disclosure.