Control system for a dual clutch transmission

This application claims the benefit of U.S. Provisional Application No. 61/146,936, filed on Jan. 23, 2009, 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 solenoids and 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 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 aspect of the present invention, the hydraulic control system includes an electric pump and an accumulator that provide a pressurized hydraulic fluid.

In another aspect of the present invention, the hydraulic control system includes two variable force solenoids in communication with an electric pump and an accumulator.

In yet another aspect of the present invention, the hydraulic control system includes two variable force solenoids in communication with the electric pump and the accumulator, two variable force solenoids or variable flow solenoids in communication with the two clutch actuating devices, and two variable force solenoids or variable flow solenoids in communication with two valve assemblies.

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

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 automatic transmission incorporating a hydraulic control system according to the principles of the present invention;

FIG. 2 is a schematic diagram of an embodiment of a hydraulic control system for a dual clutch transmission according to the principles of the present invention;

FIG. 3 is a schematic diagram of another embodiment of a hydraulic control system for a dual clutch transmission according to the principles of the present invention;

FIG. 4 is a schematic diagram of still another embodiment of a hydraulic control system for a dual clutch transmission according to the principles of the present invention;

FIG. 5A is a schematic diagram of an alternate valve assembly for use in the hydraulic control system of the present invention; and

FIG. 5B is a schematic diagram of another alternate valve assembly for use in the hydraulic control system 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. 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.

The gear arrangement 20 further includes a first synchronizer assembly 30 A, a second synchronizer assembly 30 B, and a third synchronizer assembly 30 C. The synchronizer assemblies 30 A-C 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-C is disposed either adjacent certain single gears or between adjacent pairs of gears within adjacent gear sets 26 . Each synchronizer assembly 30 A-C, 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-C.

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-C via a hydraulic control system 100 according to the principles of the present invention.

Turning to FIG. 2 , the hydraulic control system 100 of the present invention is operable to selectively engage the dual clutch assembly 18 and the synchronizer assemblies 30 A-C 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 and communicated throughout the hydraulic control system 100 via a pump 106 . The pump 106 is preferably driven by an electric engine (not shown) and 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 .

The hydraulic control system 100 further includes a plurality of solenoids and valves that direct the pressurized hydraulic fluid 102 delivered from the pump 106 or accumulator 130 via the main supply line 126 to a plurality of actuation devices. More specifically, the hydraulic control system 100 includes a first pressure control solenoid 138 , a second pressure control solenoid 140 , a first clutch solenoid 142 , a first clutch piston 144 , a second clutch solenoid 146 , a second clutch piston 148 , first synchronizer solenoid 150 , a second synchronizer solenoid 152 , a first valve assembly 154 , a second valve assembly 156 , a first synchronizer actuator 158 A, a second synchronizer actuator 158 B, and a third synchronizer actuator 158 C.

The first pressure control solenoid 138 and the second pressure control solenoid 140 branches or bifurcates the hydraulic control system 100 into two separate flow paths. This initial bifurcation, before any gear or clutch selection or activation components, essentially splits the control system 100 into two separate control systems. This is advantageous not only from a control standpoint since if only one side of the transmission 10 is active, only the clutch and gears on one shaft can possibly be selected but also its failure mode is desirable since failure of a component on one side of the transmission will affect only that side of the transmission and the control system, clutch and gears on the other side of the transmission will, in all likelihood, still be available to provide limited operation and mobility.

The first pressure control solenoid 138 is preferably an electrically controlled variable force solenoid. The first pressure control solenoid 138 includes an inlet port 138 A that communicates with an outlet port 138 B when the first pressure control solenoid 138 is activated or energized and includes an exhaust port 138 C that communicates with the outlet port 138 B when the first pressure control solenoid 138 is inactive or de-energized. Variable activation of the first pressure control solenoid 138 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 138 A to the outlet port 138 B. The inlet port 138 A is in communication with the main supply line 126 . The outlet port 138 B is in communication with a first manifold 160 . The exhaust port 138 C is in communication with an exhaust line 162 that communicates with the sump 104 . In an alternate embodiment, the first pressure control solenoid 138 may be replaced with a feed limit valve and an on/off solenoid.

The second pressure control solenoid 140 is preferably an electrically controlled variable force solenoid. The second pressure control solenoid 140 includes an inlet port 140 A that communicates with an outlet port 140 B when the second pressure control solenoid 140 is activated or energized and includes an exhaust port 140 C that communicates with the outlet port 140 B when the second pressure control solenoid 140 is inactive or de-energized. Variable activation of the second pressure control solenoid 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 inlet port 140 A is in communication with the main supply line 126 . The outlet port 140 B is in communication with a second manifold 164 . The exhaust port 140 C is in communication with the exhaust line 162 . In an alternate embodiment, the second pressure control solenoid 140 may be replaced with a feed limit valve and an on/off solenoid.

The first manifold 160 communicates the hydraulic fluid 102 from the first pressure control solenoid 138 to the first clutch control solenoid 142 , to a first pressure limit control valve 166 , and to a ball check valve 168 . The first clutch control solenoid 142 is preferably an electrically controlled variable flow solenoid, but can be a variable force solenoid, that is operable to actuate the first torque transmitting device 22 , as will be described in greater detail below. The first clutch control solenoid 142 includes an inlet port 142 A that communicates with an outlet port 142 B when the first clutch control solenoid 142 is activated or energized and includes an exhaust port 142 C that communicates with the outlet port 142 B when the first clutch control solenoid 142 is inactive or de-energized. Variable activation of the first clutch control solenoid 142 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 142 A to the outlet port 142 B. The inlet port 142 A is in communication with the first manifold 160 . The outlet port 142 B is in communication with a first clutch supply line 170 . The exhaust port 142 C is in communication with the exhaust line 162 . The first pressure limit control valve 166 is disposed in parallel with the first clutch control solenoid 142 and is in communication with the first clutch supply line 170 . If pressure within the first clutch supply line 170 exceeds a predetermined value, the first pressure limit control valve 166 opens to relieve and reduce the pressure.

The first clutch supply line 170 communicates through a flow restriction orifice 172 with an inlet port 144 A in the first clutch piston assembly 144 . The first clutch piston assembly 144 includes a single acting piston 174 slidably disposed in a cylinder 176 . The piston 174 translates under hydraulic pressure to engage the first torque transmitting device 22 , shown in FIG. 1 . When the first clutch control solenoid 142 is activated or energized, pressurized hydraulic fluid 102 is provided to the first clutch supply line 170 . The pressurized hydraulic fluid 102 is communicated from the first clutch supply line 170 to the first clutch piston assembly 144 where the pressurized hydraulic fluid 102 translates the piston 174 , thereby engaging the first torque transmitting device 22 . When the first clutch control solenoid 142 is de-energized, the inlet port 142 A is closed and hydraulic fluid from the cylinder 176 passes from the outlet port 142 B to the exhaust port 142 C and into the sump 104 , thereby disengaging the first torque transmitting device 22 .

The second manifold 164 communicates the hydraulic fluid 102 from the second pressure control solenoid 140 to the second clutch control solenoid 146 , to a second pressure limit control valve 178 , and to the ball check valve 168 . The second clutch control solenoid 146 is preferably an electrically controlled variable flow solenoid, but can be a variable force solenoid, that is operable to actuate the second torque transmitting device 24 , as will be described in greater detail below. The second clutch control solenoid 146 includes an inlet port 146 A that communicates with an outlet port 146 B when the second clutch control solenoid 146 is activated or energized and includes an exhaust port 146 C that communicates with the outlet port 146 B when the second clutch control solenoid 146 is inactive or de-energized. Variable activation of the second clutch control solenoid 146 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 146 A to the outlet port 146 B. The inlet port 146 A is in communication with the second manifold 164 . The outlet port 146 B is in communication with a second clutch supply line 180 . The exhaust port 146 C is in communication with the exhaust line 162 . The second pressure limit control valve 178 is disposed in parallel with the second clutch control solenoid 146 and is in communication with the second clutch supply line 180 . If pressure within the second clutch supply line 180 exceeds a predetermined value, the second pressure limit control valve 178 opens to relieve and reduce the pressure.

The second clutch supply line 180 communicates through a flow restriction orifice 182 with an inlet port 148 A in the second clutch piston assembly 148 . The second clutch piston assembly 148 includes a single acting piston 186 slidably disposed in a cylinder 188 . The piston 186 translates under hydraulic pressure to engage the second torque transmitting device 24 , shown in FIG. 1 . When the second clutch control solenoid 146 is activated or energized, pressurized hydraulic fluid 102 is provided to the second clutch supply line 180 . The pressurized hydraulic fluid 102 is communicated from the second clutch supply line 180 to the second clutch piston assembly 146 where the pressurized hydraulic fluid 102 translates the piston 186 , thereby engaging the second torque transmitting device 24 . When the second clutch control solenoid 146 is de-energized, the inlet port 146 A is closed and hydraulic fluid from the cylinder 188 passes from the outlet port 146 B to the exhaust port 146 C and into the sump 104 , thereby disengaging the second torque transmitting device 24 .

The ball check valve 168 is a control device that is disposed between the first manifold 160 and the second manifold 164 . The ball check valve 168 includes a first inlet port 168 A, a second inlet port 168 B, and an outlet port 168 C. The first inlet port 168 A is in communication with the first manifold 160 . The second inlet port 168 B is in communication with the second manifold 164 . The outlet port 168 C is in communication with a third manifold 190 . The ball check valve 168 closes off whichever of the inlet ports 168 A, 168 B that is delivering the lower hydraulic pressure and provides communication between whichever of the inlet ports ( 168 A, 168 B) having or delivering the higher hydraulic pressure and the outlet port 168 C.

The third manifold 190 communicates pressurized hydraulic fluid 102 to the first synchronizer solenoid 150 and the second synchronizer solenoid 152 . More specifically, the first synchronizer solenoid 150 is preferably an electrically controlled variable force solenoid, but can be a variable flow solenoid. The first synchronizer solenoid 150 is operable to control the pressure of hydraulic fluid 102 delivered to one side of each of the synchronizer actuators 158 A-C, as will be described in greater detail below. The first synchronizer solenoid 150 includes an inlet port 150 A that communicates with an outlet port 150 B when the first synchronizer solenoid 150 is activated or energized and includes an exhaust port 150 C that communicates with the outlet port 150 B when the first synchronizer solenoid 150 is inactive or de-energized. Variable activation of the first synchronizer solenoid 150 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 150 A to the outlet port 150 B. The inlet port 150 A is in communication with the third manifold 190 . The outlet port 150 B is in communication with an intermediate line 192 . The exhaust port 150 C is in communication with an exhaust line 162 .

The second synchronizer solenoid 152 is preferably an electrically controlled variable force solenoid, but can be a variable flow solenoid. The second synchronizer solenoid 152 is operable to control the pressure of hydraulic fluid 102 delivered to another side of each of the synchronizer actuators 158 A-C, as will be described in greater detail below. The second synchronizer solenoid 152 includes an inlet port 152 A that communicates with an outlet port 152 B when the second synchronizer solenoid 152 is activated or energized and includes an exhaust port 152 C that communicates with the outlet port 152 B when the second synchronizer solenoid 152 is inactive or de-energized. Variable activation of the second synchronizer solenoid 152 regulates or controls the pressure of the hydraulic fluid 102 as the hydraulic fluid 102 communicates from the inlet port 152 A to the outlet port 152 B. The inlet port 152 A is in communication with the third manifold 190 . The outlet port 152 B is in communication with an intermediate line 194 . The exhaust port 152 C is in communication with an exhaust line 162 .

The first valve assembly 154 is in communication with both the first and second synchronizer solenoids 150 , 152 via the intermediate lines 192 and 194 . The first valve assembly 154 is operable to direct pressurized hydraulic fluid 102 from the first and second synchronizer solenoids 150 , 152 to the first synchronizer actuator 158 A and to the second valve assembly 156 , as will be described in greater detail below. The first valve assembly 154 includes a first inlet port 154 A, a second inlet port 154 B, a first outlet port 154 C, a second outlet port 154 D, a third outlet port 154 E, a fourth outlet port 154 F, and an exhaust port 154 G. The first inlet port 154 A is in communication with intermediate line 192 . The second inlet port 154 B is in communication with intermediate line 194 . The first outlet port 154 C is in communication with a synchronizer supply line 196 . The second outlet port 154 D is in communication with a synchronizer supply line 198 . The third outlet port 154 E is in communication with an intermediate line 200 . The fourth outlet port 154 F is in communication with an intermediate line 202 . The exhaust port 154 G is in communication with the exhaust line 162 .

The first valve assembly 154 further includes a valve 204 slidably disposed within a bore 205 . The valve 204 is moveable between two positions by a direct acting solenoid 206 . When the direct acting solenoid 206 is energized, the valve 204 is moved to a first position, as illustrated in FIG. 2 . When the direct acting solenoid 206 is de-energized, a return spring (not shown) moves the valve 204 to a second position. When the valve 204 is in the first position, the first inlet port 154 A is in communication with the first outlet port 154 C, the second inlet port 154 B is in communication with the third outlet port 154 E, and the second and fourth outlet ports 154 D, 154 F are in communication with the exhaust port 154 G. When the valve 204 is in the second position, the first inlet port 154 A is in communication with the second outlet port 154 D, the second inlet port 154 B is in communication with the fourth outlet port 154 F, and the first and third outlet ports 154 C, 154 E are in communication with the exhaust port 154 G. Accordingly, when the direct acting solenoid 206 is energized and the valve 204 is in the first position, pressurized hydraulic fluid 102 from the first and second synchronizer solenoids 150 , 152 is communicated to the first synchronizer actuator 158 A. When the direct acting solenoid 206 is de-energized and the valve 204 is in the second position, pressurized hydraulic fluid 102 from the first and second synchronizer solenoids 150 , 152 is communicated to the second valve assembly 156 .

The second valve assembly 156 is operable to direct pressurized hydraulic fluid 102 from the first and second synchronizers 150 , 152 to the second synchronizer actuator 158 B and to the third synchronizer actuator 158 C, as will be described in greater detail below. The second valve assembly 156 includes a first inlet port 156 A, a second inlet port 1568 , a first outlet port 156 C, a second outlet port 156 D, a third outlet port 156 E, a fourth outlet port 156 F, and an exhaust port 156 G. The first inlet port 156 A is in communication with intermediate line 202 . The second inlet port 156 B is in communication with intermediate line 200 . The first outlet port 156 C is in communication with a synchronizer supply line 208 . The second outlet port 156 D is in communication with a synchronizer supply line 210 . The third outlet port 156 E is in communication with an intermediate line 212 . The fourth outlet port 156 F is in communication with an intermediate line 214 . The exhaust port 156 G is in communication with the exhaust line 162 .

The second valve assembly 156 further includes a valve 216 slidably disposed within a bore 218 . The valve 216 is moveable between two positions by a direct acting solenoid 220 . When the direct acting solenoid 220 is energized, the valve 216 is moved to a first position. When the direct acting solenoid 220 is de-energized, a return spring (not shown) moves the valve 216 to a second position, as illustrated in FIG. 2 . When the valve 216 is in the first position, the first inlet port 156 A is in communication with the first outlet port 156 C, the second inlet port 156 B is in communication with the third outlet port 156 E, and the second and fourth outlet ports 156 D, 156 F are in communication with the exhaust port 154 G. When the valve 216 is in the second position, the first inlet port 156 A is in communication with the second outlet port 156 D, the second inlet port 156 B is in communication with the fourth outlet port 156 F, and the first and third outlet ports 156 C, 156 E are in communication with the exhaust port 156 G. Accordingly, when the direct acting solenoid 220 is energized and the valve 216 is in the first position, pressurized hydraulic fluid 102 from the first and second synchronizer solenoids 150 , 152 is communicated to the third synchronizer actuator 158 C. When the direct acting solenoid 220 is de-energized and the valve 216 is in the second position, pressurized hydraulic fluid 102 from the first and second synchronizer solenoids 150 , 152 is communicated to the second synchronizer actuator 158 B.

The synchronizer actuators 158 A-C are preferably three-area piston assemblies operable to each engage or actuate a shift rail in a synchronizer assembly, but can be two-area piston assemblies. More specifically, the first synchronizer actuator 158 A is operable to actuate the first synchronizer assembly 30 A, the second synchronizer actuator 158 B is operable to actuate the second synchronizer assembly 30 B, and the third synchronizer actuator 158 C is operable to actuate the third synchronizer assembly 30 C. The first synchronizer actuator 158 A includes a first piston 228 and a second piston 230 . The pistons 228 , 230 are slidably disposed within a piston housing or cylinder 232 . The pistons 228 , 230 present three separate areas for pressurized hydraulic fluid to act upon. The first piston 228 engages or contacts a finger lever or other shift rail component of the first synchronizer assembly 30 A. The first synchronizer actuator 158 A includes a fluid port 234 that communicates with one end of the first piston 228 and with the second piston 230 and includes a fluid port 236 that communicates with an opposite end of the first piston 228 . Fluid port 234 is in communication with synchronizer supply line 196 and fluid port 236 is in communication with synchronizer supply line 198 . Accordingly, the pressurized hydraulic fluid 102 communicated from the first valve assembly 154 enters the first synchronizer actuator 158 A through the fluid ports 234 , 236 and contacts the pistons 228 , 230 . The difference in pressure between the hydraulic fluid delivered to fluid port 234 from the first synchronizer control solenoid 150 and the hydraulic fluid delivered to fluid port 236 from the second synchronizer solenoid 152 moves the pistons 228 , 230 between 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).

The second synchronizer actuator 158 B includes a first piston 238 and a second piston 240 . The pistons 238 , 240 are slidably disposed within a piston housing or cylinder 242 . The pistons 238 , 240 present three separate areas for pressurized hydraulic fluid to act upon. The first piston 238 engages or contacts a finger lever or other shift rail component of the second synchronizer assembly 30 B. The second synchronizer actuator 158 B includes a fluid port 244 that communicates with one end of the first piston 238 and with the second piston 240 and includes a fluid port 246 that communicates with an opposite end of the first piston 238 . Fluid port 244 is in communication with synchronizer supply line 210 and fluid port 246 is in communication with synchronizer supply line 214 . Accordingly, the pressurized hydraulic fluid 102 communicated from the second valve assembly 156 enters the second synchronizer actuator 158 B through the fluid ports 244 , 246 and contacts the pistons 238 , 240 . The difference in pressure between the hydraulic fluid delivered to fluid port 244 from the second synchronizer control solenoid 152 and the hydraulic fluid delivered to fluid port 246 from the first synchronizer solenoid 150 moves the pistons 238 , 240 between 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).

Finally, the third synchronizer actuator 158 C includes a first piston 248 and a second piston 250 . The pistons 248 , 250 are slidably disposed within a piston housing or cylinder 252 . The pistons 248 , 250 present three separate areas for pressurized hydraulic fluid to act upon. The first piston 248 engages or contacts a finger lever or other shift rail component of the third synchronizer assembly 30 C. The third synchronizer actuator 158 C includes a fluid port 254 that communicates with one end of the first piston 248 and with the second piston 250 and includes a fluid port 256 that communicates with an opposite end of the first piston 248 . Fluid port 254 is in communication with synchronizer supply line 208 and fluid port 256 is in communication with synchronizer supply line 212 . Accordingly, the pressurized hydraulic fluid 102 communicated from the second valve assembly 156 enters the third synchronizer actuator 158 C through the fluid ports 254 , 256 and contacts the pistons 248 , 250 . The difference in pressure between the hydraulic fluid delivered to fluid port 254 from the second synchronizer control solenoid 152 and the hydraulic fluid delivered to fluid port 256 from the first synchronizer solenoid 150 moves the pistons 248 , 250 between 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).

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 selectively actuating one of the torque transmitting devices 22 , 24 and selectively actuating one of the synchronizer assemblies 30 A-C. It should be appreciated that which actuator assembly 30 A-C and which torque transmitting device 22 , 24 provide which forward or reverse gear ratio may vary without departing from the scope of the present invention. To engage or actuate the first torque transmitting device 22 , the first pressure control solenoid 138 and the first clutch control solenoid 142 are energized. To engage or actuate the second torque transmitting device 24 , the second pressure control solenoid 140 and the second clutch control solenoid 146 are energized.

To actuate the first synchronizer assembly 30 A, one of the first and second pressure control solenoids 138 , 140 are energized and the first valve assembly 154 is placed in the first position. In addition, one of the first and second torque transmitting devices 22 , 24 are engaged as described above. Bi-directional translation of the first synchronizer assembly 30 A is then achieved by selectively energizing the synchronizer solenoids 150 , 152 . For example, synchronizer solenoid 150 is energized to move the first synchronizer actuating assembly 158 A and therefore the first synchronizer assembly 30 A to a first engaged position, synchronizer solenoid 152 is energized to move the first synchronizer actuating assembly 158 A and therefore the first synchronizer assembly 30 A to a second engaged position, and both synchronizer solenoids 150 , 152 are energized to provide a neutral position.

To actuate the second synchronizer assembly 30 B, one of the first and second pressure control solenoids 138 , 140 are energized, the first valve assembly 154 is placed in the second position, and the second valve assembly 156 is placed in the second position. In addition, one of the first and second torque transmitting devices 22 , 24 are engaged as described above. Bi-directional translation of the second synchronizer assembly 30 B is then achieved by selectively energizing the synchronizer solenoids 150 , 152 . For example, synchronizer solenoid 150 is energized to move the second synchronizer actuating assembly 158 B and therefore the second synchronizer assembly 30 B to a first engaged position, synchronizer solenoid 152 is energized to move the second synchronizer actuating assembly 158 B and therefore the second synchronizer assembly 30 A to a second engaged position, and both synchronizer solenoids 150 , 152 are energized to provide a neutral position.

To actuate the third synchronizer assembly 30 C, one of the first and second pressure control solenoids 138 , 140 are energized, the first valve assembly 154 is placed in the second position, and the second valve assembly 156 is placed in the first position. In addition, one of the first and second torque transmitting devices 22 , 24 are engaged as described above. Bi-directional translation of the third synchronizer assembly 30 C is then achieved by selectively energizing the synchronizer solenoids 150 , 152 . For example, synchronizer solenoid 150 is energized to move the third synchronizer actuating assembly 158 C and therefore the third synchronizer assembly 30 C to a first engaged position, synchronizer solenoid 152 is energized to move the third synchronizer actuating assembly 158 C and therefore the third synchronizer assembly 30 C to a second engaged position, and both synchronizer solenoids 150 , 152 are energized to provide a neutral position.

Turning now to FIG. 3 , another embodiment of a hydraulic control system is generally indicated by reference number 300 . The hydraulic control system 300 is substantially similar to the hydraulic control system 100 described above, and accordingly like components are indicated by like reference numbers. However, the hydraulic control system 300 replaces the direct acting solenoids 206 and 220 with hydraulic control solenoids 306 and 320 . Each of the hydraulic control solenoids 306 , 320 are in communication with the third manifold 190 via a hydraulic control solenoid supply line 318 . Hydraulic control solenoid 306 communicates with the first valve assembly 154 via an actuation line 320 . More specifically hydraulic control solenoid 306 is preferably an electrically controlled on/off solenoid. Hydraulic control solenoid 306 includes an inlet port 306 A that communicates with an outlet port 306 B when hydraulic control solenoid 306 is activated or energized and includes an exhaust port 306 C that communicates with the outlet port 306 B when hydraulic control solenoid 306 is inactive or de-energized. The inlet port 306 A is in communication with the hydraulic control solenoid supply line 318 . The outlet port 306 B is in communication with actuation line 320 . The exhaust port 306 C is in communication with the exhaust line 162 . A flow restriction orifice 322 is preferably disposed within the actuation line 320 between the hydraulic control solenoid 306 and the first valve assembly 154 . The valve 204 is moved to the first position when hydraulic control solenoid 306 communicates pressurized hydraulic fluid 102 from the third manifold 190 through the actuation line 320 and into the first valve assembly 154 where the hydraulic fluid 102 acts upon the valve 204 .

Hydraulic control solenoid 320 communicates with the second valve assembly 156 via an actuation line 324 . More specifically, hydraulic control solenoid 320 is preferably an electrically controlled on/off solenoid. Hydraulic control solenoid 320 includes an inlet port 320 A that communicates with an outlet port 320 B when hydraulic control solenoid 320 is activated or energized and includes an exhaust port 320 C that communicates with the outlet port 320 B when hydraulic control solenoid 320 is inactive or de-energized. The inlet port 320 A is in communication with the hydraulic control solenoid supply line 318 . The outlet port 320 B is in communication with actuation line 324 . The exhaust port 320 C is in communication with the exhaust line 162 . A flow restriction orifice 326 is preferably disposed within the actuation line 324 between the hydraulic control solenoid 320 and the second valve assembly 156 . The valve 216 is moved to the first position when hydraulic control solenoid 320 communicates pressurized hydraulic fluid 102 from the third manifold 190 through the actuation line 324 and into the second valve assembly 156 where the hydraulic fluid 102 acts upon the valve 216 .

With reference to FIG. 4 , another embodiment of a hydraulic control system is generally indicated by reference number 400 . The hydraulic control system 400 is substantially similar to the hydraulic control system 300 described above, and accordingly like components are indicated by like reference numbers. However, the hydraulic control system 400 includes an actuator feed valve 402 and a spring biased blow-off safety valve 404 . The actuator feed valve 402 is disposed within the hydraulic control solenoid supply line 318 between the third manifold 190 and the hydraulic control solenoids 306 , 320 . The actuator feed valve 402 is operable to control or limit the pressure of the hydraulic fluid 102 from the third manifold 190 before entering the hydraulic control solenoids 306 , 320 .

The spring biased blow-off safety valve 404 is in communication with the third manifold 190 and is in communication with the sump 104 . The spring biased blow-off safety valve 404 is set at a relatively high predetermined pressure and if the pressure of the hydraulic fluid 102 in the third manifold 190 exceeds this pressure due to pressure build up from the actuator feed valve 402 , the safety valve 404 opens momentarily to relieve and reduce the pressure of the hydraulic fluid 102 .

It should be appreciated that various components within the hydraulic control systems 100 , 300 , and 400 shown in FIGS. 2-4 may have alternate configurations without departing from the scope of the present invention. For example, with reference to FIG. 5A , an alternate valve assembly is indicated by reference number 554 . The valve assembly 554 replaces the first valve assembly 154 shown in FIGS. 2-4 . The valve assembly 554 includes a first inlet port 554 A, a second inlet port 554 B, a first outlet port 554 C, a second outlet port 554 D, a third outlet port 554 E, a fourth outlet port 554 F, a plurality of exhaust ports 554 G, and a primary exhaust port 554 H. The first inlet port 554 A is in communication with intermediate line 192 . The second inlet port 554 B is in communication with intermediate line 194 . The first outlet port 554 C is in communication with a synchronizer supply line 196 . The second outlet port 554 D is in communication with a synchronizer supply line 198 . The third outlet port 554 E is in communication with an intermediate line 200 . The fourth outlet port 554 F is in communication with an intermediate line 202 . The exhaust ports 554 G are in communication with the primary exhaust port 554 H which in turn is in communication with the exhaust line 162 . The valve assembly 554 further includes a valve 504 slidably disposed within a bore 505 . The valve 504 is moveable between two positions and includes a plurality of lands 506 that selectively allow communication between the outlet ports 554 C-F and the plurality of exhaust ports 554 G. The valve assembly 554 may be actuated directly, as described in FIG. 2 , or via a hydraulic fluid, as described in FIGS. 3 and 4 .

With reference to FIG. 5B , another alternate valve assembly is indicated by reference number 556 . The valve assembly 556 replaces the second valve assembly 156 shown in FIGS. 2-4 . The valve assembly 556 includes a first inlet port 556 A, a second inlet port 556 B, a first outlet port 556 C, a second outlet port 556 D, a third outlet port 556 E, a fourth outlet port 556 F, a plurality of an exhaust ports 556 G, and a primary exhaust port 556 H. The first inlet port 556 A is in communication with intermediate line 202 . The second inlet port 556 B is in communication with intermediate line 200 . The first outlet port 556 C is in communication with a synchronizer supply line 208 . The second outlet port 556 D is in communication with a synchronizer supply line 210 . The third outlet port 556 E is in communication with an intermediate line 212 . The fourth outlet port 556 F is in communication with an intermediate line 214 . The exhaust ports 556 G are in communication with the primary exhaust port 556 H which in turn is in communication with the exhaust line 162 . The valve assembly 556 further includes a valve 516 slidably disposed within a bore 518 . The valve 516 is moveable between two positions and includes a plurality of lands 519 that selectively allow communication between the outlet ports 556 C-F and the plurality of exhaust ports 556 G. The valve assembly 556 may be actuated directly, as described in FIG. 2 , or via a hydraulic fluid, as described in FIGS. 3 and 4 .

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.