Electro-hydraulic control system for a dual clutch transmission

This application claims the benefit of U.S. Provisional Application No. 61/297,490, filed on Jan. 22, 2010, which is hereby incorporated in its entirety herein by reference.

The invention relates to a control system for a dual clutch transmission, and more particularly to an electro-hydraulic control system having a plurality of solenoids and valves operable to actuate a plurality of actuators within the dual clutch transmission.

A typical multi-speed, dual clutch transmission uses a combination of two friction clutches and several dog clutch/synchronizers to achieve “power-on” or dynamic shifts by alternating between one friction clutch and the other, with the synchronizers being “pre-selected” for the oncoming ratio prior to actually making the dynamic shift. “Power-on” shifting means that torque flow from the engine need not be interrupted prior to making the shift. This concept typically uses countershaft gears with a different, dedicated gear pair or set to achieve each forward speed ratio. Typically an electronically controlled hydraulic control circuit or system is employed to control solenoids and valve assemblies. The solenoid and valve assemblies actuate clutches and synchronizers to achieve the forward and reverse gear ratios.

While previous hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within transmissions 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 dual clutch transmission.

A hydraulic control system for a dual clutch transmission includes a plurality of pressure and flow control devices and logic valves in fluid communication with a plurality of clutch actuators and with a plurality of synchronizer actuators. The clutch actuators are operable to actuate a plurality of torque transmitting devices and the synchronizer actuators are operable to actuate a plurality of synchronizer assemblies. Selective activation of combinations of the pressure control solenoids and the flow control solenoids allows for a pressurized fluid to activate at least one of the clutch actuators and synchronizer actuators in order to shift the transmission into a desired gear ratio.

In one example of the hydraulic control system, the hydraulic control system includes an electric pump and an accumulator that provide a pressurized hydraulic fluid.

In another example of the hydraulic control system, the hydraulic control system includes one pressure control device and two flow control devices operable to actuate the dual clutch.

In yet another example of the hydraulic control system, the hydraulic control system includes two pressure control devices, two flow control devices, and two logic valves operable to actuate the plurality of synchronizer assemblies.

Further features, 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.

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 schematic diagram of an exemplary dual clutch transmission having a hydraulic control system according to the principles of the present invention; and

FIGS. 2A-C are schematic diagrams of an embodiment of a hydraulic control system for a dual clutch transmission according to the principles of the present invention.

With reference to FIG. 1 , an exemplary dual clutch automatic transmission incorporating the present invention is illustrated and generally designated by the reference number 10 . The dual clutch transmission 10 includes a typically cast, metal housing 12 which encloses and protects the various components of the transmission 10 . The housing 12 includes a variety of apertures, passageways, shoulders and flanges which position and support these components. While the housing 12 is illustrated as a typical rear wheel drive transmission, it should be appreciated that the transmission 10 may be a front wheel drive transmission or a rear wheel drive transmission without departing from the scope of the present invention. The transmission 10 includes an input shaft 14 , an output shaft 16 , a dual clutch assembly 18 , and a gear arrangement 20 . The input shaft 14 is connected with a prime mover (not shown) such as an internal combustion gas or Diesel engine or a hybrid power plant. The input shaft 14 receives input torque or power from the prime mover. The output shaft 16 is preferably connected with a final drive unit (not shown) which may include, for example, propshafts, differential assemblies, and drive axles. The input shaft 14 is coupled to and drives the dual clutch assembly 18 . The dual clutch assembly 18 preferably includes a pair of selectively engageable torque transmitting devices including a first torque transmitting device 22 and a second torque transmitting device 24 . The torque transmitting devices 22 , 24 are preferably dry clutches. The torque transmitting devices 22 , 24 are mutually exclusively engaged to provide drive torque to the gear arrangement 20 .

The gear arrangement 20 includes a plurality of gear sets, indicated generally by reference number 26 , and a plurality of shafts, indicated generally by reference number 28 . The plurality of gear sets 26 includes individual intermeshing gears that are connected to or selectively connectable to the plurality of shafts 28 . The plurality of shafts 28 may include layshafts, countershafts, sleeve and center shafts, reverse or idle shafts, or combinations thereof. It should be appreciated that the specific arrangement and number of the gear sets 26 and the specific arrangement and number of the shafts 28 within the transmission 10 may vary without departing from the scope of the present invention. In the example provided, the transmission 10 provides seven forward gears and a reverse gear.

The gear arrangement 20 further includes a first synchronizer assembly 30 A, a second synchronizer assembly 30 B, a third synchronizer assembly 30 C, and a fourth synchronizer assembly 30 D. The synchronizer assemblies 30 A-D are operable to selectively couple individual gears within the plurality of gear sets 26 to the plurality of shafts 28 . Each synchronizer assembly 30 A-D is disposed either adjacent certain single gears or between adjacent pairs of gears within adjacent gear sets 26 . Each synchronizer assembly 30 A-D, when activated, synchronizes the speed of a gear to that of a shaft and a positive clutch, such as a dog or face clutch. The clutch positively connects or couples the gear to the shaft. The clutch is bi-directionally translated by a shift rail and fork assembly (not shown) within each synchronizer assembly 30 A-D.

The transmission also includes a transmission control module 32 . The transmission control module 32 is preferably an electronic control device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The transmission control module 32 controls the actuation of the dual clutch assembly 18 and the synchronizer assemblies 30 A-D via a hydraulic control system 100 according to the principles of the present invention.

Turning to FIGS. 2A-C , the hydraulic control system 100 is operable to selectively engage the dual clutch assembly 18 and the synchronizer assemblies 30 A-D by selectively communicating a hydraulic fluid 102 from a sump 104 to a plurality of shift actuating devices, as will be described in greater detail below. The sump 104 is a tank or reservoir preferably disposed at the bottom of the transmission housing 12 to which the hydraulic fluid 102 returns and collects from various components and regions of the automatic transmission 10 . The hydraulic fluid 102 is forced from the sump 104 via a pump 106 . The pump 106 is driven by an electric motor or combustion engine (not shown) or any other type of prime mover. The pump 106 may be, for example, a gear pump, a vane pump, a gerotor pump, or any other positive displacement pump. The pump 106 includes an inlet port 108 and an outlet port 110 . The inlet port 108 communicates with the sump 104 via a suction line 112 . The outlet port 110 communicates pressurized hydraulic fluid 102 to a supply line 114 . The supply line 114 is in communication with a spring biased blow-off safety valve 116 , a pressure side filter 118 , and a spring biased check valve 120 . The spring biased blow-off safety valve 116 communicates with the sump 104 . The spring biased blow-off safety valve 116 is set at a relatively high predetermined pressure and if the pressure of the hydraulic fluid 102 in the supply line 114 exceeds this pressure, the safety valve 116 opens momentarily to relieve and reduce the pressure of the hydraulic fluid 102 . The pressure side filter 118 is disposed in parallel with the spring biased check valve 120 . If the pressure side filter 118 becomes blocked or partially blocked, pressure within supply line 114 increases and opens the spring biased check valve 120 in order to allow the hydraulic fluid 102 to bypass the pressure side filter 118 .

The pressure side filter 118 and the spring biased check valve 120 each communicate with an outlet line 122 . The outlet line 122 is in communication with a second check valve 124 . The second check valve 124 is in communication with a main supply line 126 and is configured to maintain hydraulic pressure within the main supply line 126 . The main supply line 126 supplies pressurized hydraulic fluid to an accumulator 130 and a main pressure sensor 132 . The accumulator 130 is an energy storage device in which the non-compressible hydraulic fluid 102 is held under pressure by an external source. In the example provided, the accumulator 130 is a spring type or gas filled type accumulator having a spring or compressible gas that provides a compressive force on the hydraulic fluid 102 within the accumulator 130 . However, it should be appreciated that the accumulator 130 may be of other types, such as a gas-charged type, without departing from the scope of the present invention. Accordingly, the accumulator 130 is operable to supply pressurized hydraulic fluid 102 back to the main supply line 126 . However, upon discharge of the accumulator 130 , the second check valve 124 prevents the pressurized hydraulic fluid 102 from returning to the pump 106 . The accumulator 130 , when charged, effectively replaces the pump 106 as the source of pressurized hydraulic fluid 102 , thereby eliminating the need for the pump 106 to run continuously. The main pressure sensor 132 reads the pressure of the hydraulic fluid 102 within the main supply line 126 in real time and provides this data to the transmission control module 32 . Accordingly, the transmission control module 32 can operate the pump 106 based on real-time conditions of the accumulator 130 .

The main supply line 126 is channeled through a heat sink 134 used to cool the controller 32 , though it should be appreciated that the heat sink 134 may be located elsewhere or removed from the hydraulic control system 100 without departing from the scope of the present invention. The main supply line 126 supplies pressurized hydraulic fluid 102 to three pressure control devices including a clutch pressure control device 136 , a first actuator pressure control device 140 , and a second actuator pressure control device 141 .

The clutch pressure control device 136 is preferably an electrically controlled variable force solenoid having an internal closed loop pressure control. Various makes, types, and models of solenoids may be employed with the present invention so long as the clutch pressure control device 136 is operable to control the pressure of the hydraulic fluid 102 . The clutch pressure control device 136 includes an inlet port 136 A that communicates with an outlet port 136 B when the clutch pressure control device 136 is activated or energized and includes an exhaust port 136 C that communicates with the outlet port 136 B when the clutch pressure control device 136 is inactive or de-energized. Variable activation of the clutch pressure control device 136 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 136 A to the outlet port 136 B. The internal closed loop pressure control provides pressure feedback within the solenoid to adjust the amount of flow to the outlet port 136 B based on a particular current command from the controller 32 , thereby controlling pressure. The inlet port 136 A is in communication with the main supply line 126 . The outlet port 136 B is in communication with an intermediate line 142 . The exhaust port 136 C is in communication with the sump 104 , or an exhaust backfill circuit (not shown).

The intermediate line 142 communicates the hydraulic fluid 102 from the clutch pressure control device 136 to a first clutch flow control device 144 , to a first pressure limit control valve 146 , to a second clutch flow control device 160 , to a second pressure limit control valve 162 , and to mode valve control solenoid 174 . The first clutch flow control device 144 is preferably an electrically controlled variable force solenoid that is operable to control a flow of the hydraulic fluid 102 from the first clutch flow control device 144 in order to actuate the first torque transmitting device 22 , as will be described in greater detail below. The first clutch flow control device 144 includes an inlet port 144 A that communicates with an outlet port 144 B when the first clutch flow control device 144 is energized to a current greater than a null point current (i.e., the zero forward/reverse flow point for the given current) and includes an exhaust port 144 C that communicates with the outlet port 144 B when the first clutch flow control device 144 is de-energized to a current less than the null point current. Variable activation of the first clutch flow control device 144 regulates or controls the flow of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 144 A to the outlet port 144 B. The inlet port 144 A is in communication with the intermediate line 142 . The outlet port 144 B is in communication with a first clutch supply line 148 and a flow restriction orifice 150 . The exhaust port 144 C is in communication with the sump 104 or an exhaust backfill circuit (not shown). The first pressure limit control valve 146 is disposed in parallel with the first clutch flow control solenoid 144 and is in communication with the first clutch supply line 148 . If pressure within the first clutch supply line 148 exceeds a predetermined value, the first pressure limit control valve 146 opens to relieve and reduce the pressure.

The first clutch supply line 148 is in fluid communication with an inlet/outlet port 152 A in a first clutch piston assembly 152 . The first clutch piston assembly 152 includes a single acting piston 154 slidably disposed in a cylinder 156 . The piston 154 translates under hydraulic pressure to engage the first torque transmitting device 22 , shown in FIG. 1 . When the first clutch flow control device 144 is activated or energized above the null point, a flow of pressurized hydraulic fluid 102 is provided to the first clutch supply line 148 . The flow of pressurized hydraulic fluid 102 is communicated from the first clutch supply line 148 to the first clutch piston assembly 152 where the pressurized hydraulic fluid 102 translates the piston 154 , thereby engaging the first torque transmitting device 22 . When the first clutch flow control solenoid 144 is de-energized below the null point, the inlet port 144 A is closed and hydraulic fluid from the cylinder 156 passes from the outlet port 144 B to the exhaust port 144 C and into the sump 104 or an exhaust backfill circuit (not shown), thereby disengaging the first torque transmitting device 22 . The translation of the piston 154 is monitored by a position sensor 157 .

The second clutch flow control device 160 is preferably an electrically controlled variable force solenoid that is operable to control a flow of the hydraulic fluid 102 from the second clutch flow control device 160 in order to actuate the second torque transmitting device 24 , as will be described in greater detail below. The second clutch flow control device 160 includes an inlet port 160 A that communicates with an outlet port 160 B when the second clutch flow control device 160 is energized to a current greater than the null point current and includes an exhaust port 160 C that communicates with the outlet port 160 B when the second clutch flow control device 160 is de-energized below the null point current. Variable activation of the second clutch flow control device 160 regulates or controls the flow of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 160 A to the outlet port 160 B. The inlet port 160 A is in communication with the intermediate line 142 . The outlet port 160 B is in communication with a second clutch supply line 164 and a flow restriction orifice 166 . The exhaust port 160 C is in communication with the sump 104 or an exhaust backfill circuit (not shown). The second pressure limit control valve 162 is disposed in parallel with the second clutch flow control solenoid 160 and is in communication with the second clutch supply line 164 . If pressure within the second clutch supply line 164 exceeds a predetermined value, the second pressure limit control valve 162 opens to relieve and reduce the pressure. The translation of the piston 170 is monitored by a position sensor 167 .

The second clutch supply line 164 is in fluid communication with an inlet/outlet port 168 A in a second clutch piston assembly 168 . The second clutch piston assembly 168 includes a single acting piston 170 slidably disposed in a cylinder 172 . The piston 170 translates under hydraulic pressure to engage the second torque transmitting device 24 , shown in FIG. 1 . When the second clutch flow control device 160 is activated or energized to a current greater than the null point, a flow of pressurized hydraulic fluid 102 is provided to the second clutch supply line 166 . The flow of pressurized hydraulic fluid 102 is communicated from the second clutch supply line 166 to the second clutch piston assembly 168 where the pressurized hydraulic fluid 102 translates the piston 170 , thereby engaging the second torque transmitting device 24 . When the second clutch flow control solenoid 160 is de-energized a current less than the null point, the inlet port 160 A is closed and hydraulic fluid from the cylinder 172 passes from the outlet port 160 B to the exhaust port 160 C and into the sump 104 , thereby disengaging the second torque transmitting device 24 .

The first and second actuator pressure control devices 140 and 141 are operable to selectively provide flows of pressurized hydraulic fluid 102 through first and second actuator flow control devices 178 , 180 and through first and second valve assemblies 182 , 184 in order to selectively actuate a plurality of synchronizer shift actuators. The synchronizer actuators include a first synchronizer actuator 186 A, a second synchronizer actuator 186 B, a third synchronizer actuator 186 C, and a fourth synchronizer actuator 186 D.

For example, the first actuator pressure control device 140 is preferably an electrically controlled variable force solenoid having an internal closed loop pressure control. Various makes, types, and models of solenoids may be employed with the present invention so long as the first actuator pressure control device 140 is operable to control the pressure of the hydraulic fluid 102 . The first actuator pressure control device 140 includes an inlet port 140 A that communicates with an outlet port 140 B when the first actuator pressure control device 140 is activated or energized and includes an exhaust port 140 C that communicates with the outlet port 140 B when the first actuator pressure control device 140 is inactive or de-energized. Variable activation of the first actuator pressure control device 140 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 140 A to the outlet port 140 B. The internal closed loop pressure control provides pressure feedback within the solenoid to adjust the amount of flow to the outlet port 140 B based on a particular current command from the controller 32 , thereby controlling pressure. The inlet port 140 A is in communication with the main supply line 126 . The outlet port 140 B is in communication with an intermediate line 188 . The exhaust port 140 C is in communication with the sump 104 or an exhaust backfill circuit (not shown).

The intermediate line 188 communicates pressurized hydraulic fluid 102 from the first actuator pressure control device 140 to a first flow control device 178 and the first valve assembly 182 . The first flow control device 178 is preferably an electrically controlled variable force solenoid. Various makes, types, and models of solenoids may be employed with the present invention so long as the first flow control device 178 is operable to control the flow of the hydraulic fluid 102 . The first flow control device 178 includes an inlet port 178 A that communicates through an adjustable hydraulic orifice or restriction with an outlet port 178 B when the first flow control device 178 energized to a current greater than the null point current and includes an exhaust port 178 C that communicates with the outlet port 178 B when the first flow control device 178 is de-energized to a current less than the null point current. Variable activation of the first flow control device 178 regulates or controls the flow of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 178 A to the outlet port 178 B and from outlet port 178 B to exhaust port 178 C. The inlet port 178 A is in communication with the intermediate line 188 . The outlet port 178 B is in communication with an intermediate line 190 which communicates with the first valve assembly 182 . The exhaust port 178 C is in communication with the sump 104 or an exhaust backfill circuit (not shown).

The first valve assembly 182 is operable to selectively direct the pressurized hydraulic fluid 102 flows from the first pressure control device 140 and the first actuator flow control device 178 to the first synchronizer actuator 186 A and to the second synchronizer actuator 186 B, as will be described in greater detail below. The first valve assembly 182 includes a first inlet port 182 A, a second inlet port 182 B, a first outlet port 182 C, a second outlet port 182 D, a third outlet port 182 E, a fourth outlet port 182 F, a plurality of exhaust ports 182 G, and a control port 182 H. The first inlet port 182 A is in communication with the intermediate line 190 . The second inlet port 182 B is in communication with the intermediate line 188 . The first outlet port 182 C is in communication with a synchronizer supply line 192 . The second outlet port 182 D is in communication with a synchronizer supply line 194 . The third outlet port 182 E is in communication with a synchronizer supply line 196 . The fourth outlet port 182 F is in communication with a synchronizer supply line 198 . The exhaust ports 182 G are in ultimately in communication with the sump 104 or an exhaust backfill circuit (not shown). The control port 182 H is in communication with a control line 200 that communicates with the control device 174 . The valve control device 174 is preferably an on-off solenoid that is normally closed. However, it should be appreciated that other types of solenoids and other control devices may be employed without departing from the scope of the present invention, such as pressure control solenoids.

The first valve assembly 182 further includes a valve spool 202 slidably disposed within a valve body or bore 204 . The valve spool 202 is moveable between at least two positions by a biasing member 206 and by fluid flow channeled from the control device 174 via control line 200 . The biasing member 206 is preferably a spring and acts on an end of the valve spool 202 to bias the valve spool 202 to the first position or de-stroked position. When the control device 174 is energized or activated a flow of the hydraulic fluid 102 is communicated to the control port 182 H via control line 200 and into a control chamber 191 of valve assembly 182 . The hydraulic fluid 102 acts on an end of the valve spool 202 to move the valve spool 202 and compress biasing member 206 to place valve spool 202 in the second position or stroked position. A supply of pressurized hydraulic fluid is provided to the control device 174 via intermediate fluid line 142 when the clutch pressure control device 136 is energized or opened.

When the valve spool 202 is in the de-stroked position, the first inlet port 182 A is in communication with the second outlet port 182 D, the second inlet port 182 B is in communication with the fourth outlet port 182 F, and the first and third outlet ports 182 C, 182 E are in communication with the exhaust ports 182 G. When the valve spool 202 is in the stroked position, as shown in FIG. 2B , the first inlet port 182 A is in communication with the first outlet port 182 C, the second inlet port 182 B is in communication with the third outlet port 182 E, and the second and fourth outlet ports 182 D, 182 F are in communication with the exhaust ports 182 G. Accordingly, when the valve control device 174 is opened, pressurized hydraulic fluid 102 flows from the first pressure control device 140 and a variable flow of hydraulic fluid 102 flows from the first flow control device 178 to the second synchronizer actuator 186 B. When the valve control device 174 is closed, pressurized hydraulic fluid 102 flows from the first pressure control device 140 and a variable flow of hydraulic fluid 102 flows from the first flow control device 178 to the first synchronizer actuator 186 A.

The second actuator pressure control device 141 is preferably an electrically controlled variable force solenoid having an internal closed loop pressure control. Various makes, types, and models of solenoids may be employed with the present invention so long as the second actuator pressure control device 141 is operable to control the pressure of the hydraulic fluid 102 . The second actuator pressure control device 141 includes an inlet port 141 A that communicates with an outlet port 141 B when the second actuator pressure control device 141 is activated or energized and includes an exhaust port 141 C that communicates with the outlet port 141 B when the second actuator pressure control device 141 is inactive or de-energized. Variable activation of the second actuator pressure control device 141 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 141 A to the outlet port 141 B. The internal closed loop pressure control provides pressure feedback within the solenoid to adjust the amount of flow to the outlet port 141 B based on a particular current command from the controller 32 , thereby controlling pressure. The inlet port 141 A is in communication with the main supply line 126 . The outlet port 141 B is in communication with an intermediate line 210 . The exhaust port 141 C is in communication with the sump 104 or an exhaust backfill circuit (not shown).

The intermediate line 210 communicates pressurized hydraulic fluid 102 from the second actuator pressure control device 141 to the second flow control device 180 and the second valve assembly 184 . The second flow control device 180 is preferably an electrically controlled variable force solenoid. Various makes, types, and models of solenoids may be employed with the present invention so long as the second flow control device 180 is operable to control the flow of the hydraulic fluid 102 . The second flow control device 180 includes an inlet port 180 A that communicates through an adjustable hydraulic orifice or restriction with an outlet port 1808 when the second flow control device 180 is energized to a current above the null point current and includes an exhaust port 180 C that communicates with the outlet port 180 B when the second flow control device 180 is de-energized below the null point current. Variable activation of the second flow control device 180 regulates or controls the flow of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 180 A to the outlet port 180 B and from outlet port 180 B to exhaust port 180 C. The inlet port 180 A is in communication with the intermediate line 210 . The outlet port 180 B is in communication with an intermediate line 212 which communicates with the second valve assembly 184 . The exhaust port 180 C is in communication with the sump 104 .

The second valve assembly 184 is operable to selectively direct the pressurized hydraulic fluid 102 flows from the second pressure control device 141 and the second actuator flow control device 180 to the third synchronizer actuator 186 C and to the fourth synchronizer actuator 186 D, as will be described in greater detail below. The second valve assembly 184 includes a first inlet port 184 A, a second inlet port 184 B, a first outlet port 184 C, a second outlet port 184 D, a third outlet port 184 E, a fourth outlet port 184 F, a plurality of exhaust ports 184 G, and a control port 184 H. The first inlet port 184 A is in communication with the intermediate line 212 . The second inlet port 184 B is in communication with the intermediate line 210 . The first outlet port 184 C is in communication with a synchronizer supply line 214 . The second outlet port 184 D is in communication with a synchronizer supply line 216 . The third outlet port 184 E is in communication with a synchronizer supply line 218 . The fourth outlet port 184 F is in communication with a synchronizer supply line 220 . The exhaust ports 184 G are in communication with the sump 104 or an exhaust backfill circuit (not shown). The control port 184 H is in communication with the control line 200 that communicates with the control device 174 .

The second valve assembly 184 further includes a valve spool 222 slidably disposed within a valve body or bore 224 . The valve spool 222 is moveable between at least two positions by a biasing member 226 and by fluid flow channeled from the control device 174 via control line 200 . The biasing member 226 is preferably a spring and acts on an end of the valve spool 222 to bias the valve spool 222 to the first position or de-stroked position. When the control device 174 is energized or activated a flow of the hydraulic fluid 102 is communicated to the control port 184 H via control line 200 and into a control chamber 227 of valve assembly 184 . The hydraulic fluid 102 acts on an end of the valve spool 222 to move the valve spool 222 and compress biasing member 226 to place valve spool 222 in the second position or stroked position.

When the valve 222 is in the de-stroked position, the first inlet port 184 A is in communication with the second outlet port 184 D, the second inlet port 184 B is in communication with the fourth outlet port 184 F, and the first and third outlet ports 184 C, 184 E are in communication with the exhaust ports 184 G. When the valve 222 is in the stroked position, as shown in FIG. 2C , the first inlet port 184 A is in communication with the first outlet port 184 C, the second inlet port 184 B is in communication with the third outlet port 184 E, and the second and fourth outlet ports 184 D, 184 F are in communication with the exhaust ports 184 G. Accordingly, when the valve control device 174 is opened, pressurized hydraulic fluid 102 flows from the second pressure control device 141 and a variable flow of hydraulic fluid 102 flows from the second flow control device 180 to the fourth synchronizer actuator 186 D. When the valve control device 174 is closed, pressurized hydraulic fluid 102 flows from the second pressure control device 141 and a variable flow of hydraulic fluid 102 flows from the second flow control device 180 to the third synchronizer actuator 186 C.

The synchronizer actuators 186 A-D are preferably two-area piston assemblies operable to each engage or actuate a shift rail in a synchronizer assembly, but can be three-area piston assemblies without departing from the scope of the present invention. For example, the first synchronizer actuator 186 A is operable to actuate the first synchronizer assembly 30 A, the second synchronizer actuator 186 B is operable to actuate the second synchronizer assembly 30 B, the third synchronizer actuator 186 C is operable to actuate the third synchronizer assembly 30 C, and the fourth synchronizer actuator 186 D is operable to actuate the fourth synchronizer assembly 30 D.

The first synchronizer actuator 186 A includes a piston 230 A slidably disposed within a piston housing or cylinder 232 A. A detent spring 231 A biases the piston 230 A in a first engaged position, a second engaged position and in a neutral position. The piston 230 A presents two separate areas for pressurized hydraulic fluid to act upon. The piston 230 A engages or contacts a finger lever, shift fork, or other shift rail component 233 A of the first synchronizer assembly 30 A. The first synchronizer actuator 186 A includes a fluid port 234 A that communicates with a first end 235 A of the piston 230 A and a fluid port 236 A that communicates with an opposite second end 237 A of the piston 230 A having a smaller contact area than the first end 235 A. Fluid port 234 A is in communication with the synchronizer supply line 194 and fluid port 236 A is in communication with the synchronizer supply line 198 . Accordingly, the pressurized hydraulic fluid 102 communicated from the first actuator pressure control device 140 enters the first synchronizer actuator 186 A through the fluid port 236 A and contacts the second end 237 A of the piston 230 A and the flow of hydraulic fluid 102 from the first flow control device 178 enters the first synchronizer actuator 186 A through the fluid port 234 A and contacts the first end 235 A of the piston 230 A. The difference in the force generated by the pressure of the hydraulic fluid 102 delivered to fluid port 236 A from the first actuator pressure control device 140 and the hydraulic fluid 102 delivered to fluid port 234 A from the first flow control device 178 moves the piston 230 A between various positions. By controlling the flow of hydraulic fluid 102 from the first flow control device 178 , the piston 234 A is actuated between the various positions. Each position in turn corresponds to a position of the shift rail of the first synchronizer assembly 30 A (i.e., engaged left, engaged right, and neutral). A fork position sensor 240 A may be included to communicate to the controller 32 the position of the shift fork 233 A.

The second synchronizer actuator 186 B includes a piston 230 B slidably disposed within a piston housing or cylinder 232 B. A detent spring 231 B biases the piston 230 B in a first engaged position, a second engaged position and in a neutral position. The piston 230 B presents two separate areas for pressurized hydraulic fluid to act upon. The piston 230 B engages or contacts a finger lever, shift fork, or other shift rail component 233 B of the second synchronizer assembly 30 B. The second synchronizer actuator 186 B includes a fluid port 234 B that communicates with a first end 235 B of the piston 230 B and a fluid port 236 B that communicates with an opposite second end 237 B of the piston 230 B having a smaller contact area than the first end 235 B. Fluid port 234 B is in communication with the synchronizer supply line 192 and fluid port 236 B is in communication with the synchronizer supply line 196 . Accordingly, the pressurized hydraulic fluid 102 communicated from the first actuator pressure control device 140 enters the second synchronizer actuator 186 B through the fluid port 236 B and contacts the second end 237 B of the piston 230 B and the flow of hydraulic fluid 102 from the first flow control device 178 enters the second synchronizer actuator 186 B through the fluid port 234 B and contacts the first end 235 B of the piston 230 B. The difference in the force generated by the pressure of the hydraulic fluid 102 delivered to fluid port 236 B from the first actuator pressure control device 140 and the hydraulic fluid 102 delivered to fluid port 234 B from the first flow control device 178 moves the piston 230 B between various positions. By controlling the flow of hydraulic fluid 102 from the first flow control device 178 , the piston 230 B is actuated between the various positions. Each position in turn corresponds to a position of the shift rail of the second synchronizer assembly 30 B (i.e., engaged left, engaged right, and neutral). A fork position sensor 240 B may be included to communicate to the controller 32 the position of the shift fork 233 B.

The third synchronizer actuator 186 C includes a piston 230 C slidably disposed within a piston housing or cylinder 232 C. A detent spring 231 C biases the piston 230 C in a first engaged position, a second engaged position and in a neutral position. The piston 230 C presents two separate areas for pressurized hydraulic fluid to act upon. The piston 230 C engages or contacts a finger lever, shift fork, or other shift rail component 233 C of the third synchronizer assembly 30 C. The third synchronizer actuator 186 C includes a fluid port 234 C that communicates with a first end 235 C of the piston 230 C and a fluid port 236 C that communicates with an opposite second end 237 C of the piston 230 C having a smaller contact area than the first end 235 C. Fluid port 234 C is in communication with the synchronizer supply line 216 and fluid port 236 C is in communication with the synchronizer supply line 220 . Accordingly, the pressurized hydraulic fluid 102 communicated from the second actuator pressure control device 141 enters the third synchronizer actuator 186 C through the fluid port 236 C and contacts the second end 237 C of the piston 230 C and the flow of hydraulic fluid 102 from the second flow control device 180 enters the third synchronizer actuator 186 C through the fluid port 234 C and contacts the first end 235 C of the piston 230 C. The difference in the force generated by the pressure of the hydraulic fluid 102 delivered to fluid port 236 C from the second actuator pressure control device 141 and the hydraulic fluid 102 delivered to fluid port 234 C from the second flow control device 180 moves the piston 230 C between various positions. By controlling the flow of hydraulic fluid 102 from the second flow control device 180 , the piston 234 C is actuated between the various positions. Each position in turn corresponds to a position of the shift rail of the third synchronizer assembly 30 C (i.e., engaged left, engaged right, and neutral). A fork position sensor 240 C may be included to communicate to the controller 32 the position of the shift fork 233 C.

The fourth synchronizer actuator 186 D includes a piston 230 D slidably disposed within a piston housing or cylinder 232 D. A detent spring 231 D biases the piston 230 D in a first engaged position, a second engaged position and in a neutral position. The piston 230 D presents two separate areas for pressurized hydraulic fluid to act upon. The piston 230 D engages or contacts a finger lever, shift fork, or other shift rail component 233 D of the fourth synchronizer assembly 30 D. The fourth synchronizer actuator 186 D includes a fluid port 234 D that communicates with a first end 235 D of the piston 230 D and a fluid port 236 D that communicates with an opposite second end 237 D of the piston 230 D having a smaller contact area than the first end 235 D. Fluid port 234 D is in communication with the synchronizer supply line 214 and fluid port 236 D is in communication with the synchronizer supply line 218 . Accordingly, the pressurized hydraulic fluid 102 communicated from the second actuator pressure control device 141 enters the fourth synchronizer actuator 186 D through the fluid port 236 D and contacts the second end 237 D of the piston 230 D and the flow of hydraulic fluid 102 from the second flow control device 180 enters the fourth synchronizer actuator 186 D through the fluid port 234 D and contacts the first end 235 D of the piston 230 D. The difference in the force generated by the pressure of the hydraulic fluid 102 delivered to fluid port 236 D from the second actuator pressure control device 141 and the hydraulic fluid 102 delivered to fluid port 234 D from the second flow control device 180 moves the piston 230 D between various positions. By controlling the flow of hydraulic fluid 102 from the second flow control device 180 , the piston 234 D is actuated between the various positions. Each position in turn corresponds to a position of the shift rail of the fourth synchronizer assembly 30 D (i.e., engaged left, engaged right, and neutral). A fork position sensor 240 D may be included to communicate to the controller 32 the position of the shift fork 233 D.

During general operation of the hydraulic control system 100 , the accumulator 130 provides the pressurized hydraulic fluid 102 throughout the system and the pump 106 is employed to charge the accumulator 130 . Selection of a particular forward or reverse gear ratio is achieved by first selectively actuating one of the synchronizer assemblies 30 A-D and then selectively actuating one of the torque transmitting devices 22 , 24 . It should be appreciated that the combination of selective engagement of the actuator assemblies 30 A-D and torque transmitting devices 22 , 24 providing a forward or reverse gear ratio may vary without departing from the scope of the present invention.

Generally, the first actuator pressure control device 140 selectively provides pressurized hydraulic fluid 102 to each of the synchronizer actuators 186 A-B and the first flow control device 178 and the second actuator pressure control device 141 selectively provides pressurized hydraulic fluid 102 to each of the synchronizer actuators 186 C-D and the second flow control device 180 . Individual synchronizer actuators 186 A-D are actuated by controlling a flow from one of the flow control devices 178 and 180 based upon positioning of the first and second valve assemblies 182 and 184 .

For example, to actuate the first synchronizer assembly 30 A, the first pressure control device 140 is energized to provide a pressure on the piston 230 A and to provide a flow of pressurized hydraulic fluid 102 to the first flow control device 178 . Bi-directional translation of the first synchronizer assembly 30 A is then achieved by selectively energizing the first flow control device 178 . To actuate the second synchronizer assembly 30 B, the first pressure control device 140 is energized to provide a pressure force on the piston 230 B and to provide a flow of pressurized hydraulic fluid 102 to the first flow control device 178 . Bi-directional translation of the second synchronizer assembly 30 B is then achieved by selectively energizing the first flow control device 178 .

To actuate the third synchronizer assembly 30 C, the second pressure control device 141 is energized to provide a pressure force on the piston 230 C and to provide a flow of pressurized hydraulic fluid 102 to the second flow control device 180 . Bi-directional translation of the third synchronizer assembly 30 C is then achieved by selectively energizing the second flow control device 180 .

To actuate the fourth synchronizer assembly 30 D, the second pressure control device 141 is energized to provide a pressure force on the piston 230 D and to provide a flow of pressurized hydraulic fluid 102 to the second flow control device 180 . Bi-directional translation of the third synchronizer assembly 30 D is then achieved by selectively energizing the second flow control device 180 .

To engage or actuate the first torque transmitting device 22 , the clutch pressure control device 136 and the first clutch flow control device 144 is energized or opened. To engage or actuate the second torque transmitting device 24 , the clutch pressure control device 136 and the second clutch flow control device 160 are energized or opened.

By providing flow control of the clutches 22 and 24 and/or the synchronizer assemblies 30 A-D, the hydraulic control system 100 is operable to provide direct clutch position control, direct synchronizer actuator position control, and variable clutch and synchronizer actuator position control. At the same time, quick clutch response times are enabled, spin losses are reduced, and packaging space of the hydraulic control system 100 is reduced, all of which contributes to improved fuel economy and performance. The hydraulic control system 100 is also compatible with BAS/BAS+ hybrid systems. Finally, failure mode protection is enabled through pre-staged position control of the control devices 136 , 140 , 141 , 144 , 160 , 178 , 180 , and the valves 182 and 184 .

The description of the invention is merely exemplary in nature and variations that do not depart from the general essence 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.