Abstract:
A hydraulic control circuit for a transmission includes a plurality of solenoids and valves in fluid communication with a plurality of actuators. The actuators are operable to actuate a plurality of torque transmitting devices. Selective activation of the solenoids allows for a pressurized fluid flow to activate at least one of the actuators in order to shift the transmission into a desired gear ratio.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/893,882, filed on Mar. 8, 2007. The disclosure of the above application is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a control system for a multi-speed transmission, and more particularly to a hydraulic control system having a plurality of solenoids and valves operable to actuate a plurality of actuators within the multi-speed transmission. 
       BACKGROUND 
       [0003]    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. 
         [0004]    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 transmission. 
       SUMMARY 
       [0005]    The present invention provides a hydraulic control circuit for a transmission. The hydraulic control circuit includes a plurality of solenoids and valves in fluid communication with a plurality of actuators. The actuators are operable to actuate a plurality of torque transmitting devices. Selective activation of the solenoids allows for a pressurized fluid flow to activate at least one of the actuators in order to shift the transmission into a desired gear ratio. 
         [0006]    One embodiment of the hydraulic control circuit of the present invention includes a first solenoid that receives a first pressurized fluid flow, a second solenoid that receives a second pressurized fluid flow, a first valve assembly in communication with the first solenoid for selectively receiving the first pressurized fluid flow and in communication with the second solenoid for selectively receiving the second pressurized fluid flow, a second valve assembly in communication with the first valve assembly for selectively receiving one of the first and second pressurized fluid flows, and a third valve assembly in communication with the first valve assembly for selectively receiving one of the first and second pressurized fluid flows. A first actuator is in communication with the second valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a first pair of a plurality of gear ratios, a second actuator is in communication with the second valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a second pair of the plurality of gear ratios, a third actuator is in communication with the third valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a third pair of the plurality of gear ratios, a fourth actuator is in communication with the third valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a fourth pair of the plurality of gear ratios. The first solenoid is operable to selectively communicate the first pressurized fluid flow to the first valve assembly, the second solenoid is operable to selectively communicate the second pressurized fluid flow to the first valve assembly, the first valve assembly is operable to selectively communicate the first and second pressurized fluid flows to the second and third valve assemblies, the second valve assembly is operable to selectively communicate the first and second pressurized fluid flows to the first and second actuators, and the third valve assembly is operable to selectively communicate the first and second pressurized fluid flows to the third and fourth actuators. 
         [0007]    In one aspect of the present invention, the first solenoid includes a first solenoid fluid port in communication with the first valve assembly and the second solenoid includes a second solenoid fluid port in communication with the first valve assembly. 
         [0008]    In another aspect of the present invention, the first valve assembly includes a first fluid port in communication with the first solenoid fluid port and a second fluid port in communication with the second solenoid fluid port. 
         [0009]    In yet another aspect of the present invention, the first valve assembly includes a third fluid port and a fourth fluid port in selective communication with the first fluid port and a fifth fluid port and a sixth fluid port in selective communication with the second fluid port, wherein the third and fifth fluid ports are in communication with the second valve assembly and the fourth and sixth fluid ports are in communication with the third valve assembly. 
         [0010]    In yet another aspect of the present invention, the second valve assembly includes a seventh fluid port in communication with the fourth fluid port and an eighth fluid port in communication with the sixth fluid port. 
         [0011]    In yet another aspect of the present invention, the second valve assembly includes a ninth fluid port and a tenth fluid port in selective communication with the seventh fluid port and an eleventh fluid port and a twelfth fluid port in selective communication with the eighth fluid port, wherein the tenth and twelfth fluid ports are in communication with the first actuator and the ninth and eleventh fluid ports are in communication with the second actuator. 
         [0012]    In yet another aspect of the present invention, the third valve assembly includes a thirteenth fluid port in communication with the third fluid port and fourteenth fluid port in communication with the fifth fluid port. 
         [0013]    In yet another aspect of the present invention, the third valve assembly includes a fifteenth fluid port and a sixteenth fluid port in selective communication with the thirteenth fluid port and a seventeenth fluid port and an eighteenth fluid port in selective communication with the fourteenth fluid port, wherein the fifteenth and seventeenth fluid ports are in communication with the third actuator and the sixteenth and eighteenth fluid ports are in communication with the fourth actuator. 
         [0014]    In yet another aspect of the present invention, the first valve assembly includes a moveable first valve operable to allow fluid communication between the first fluid port and the third fluid port when in a first position, to allow fluid communication between the first fluid port and the fourth fluid port when in a second position, to allow fluid communication between the second fluid port and the fifth fluid port when in the first position, and to allow fluid communication between the second fluid port and the sixth fluid port when in the second position. 
         [0015]    In yet another aspect of the present invention, the valve is moveable between the first and second positions by a first valve solenoid assembly in fluid communication with the first valve assembly. 
         [0016]    In yet another aspect of the present invention, the second valve assembly includes a moveable second valve operable to allow fluid communication between the seventh fluid port and the ninth fluid port when in a first position, to allow fluid communication between the seventh fluid port and the tenth fluid port when in a second position, to allow fluid communication between the eighth fluid port and the eleventh fluid port when in the first position, and to allow fluid communication between the eighth fluid port and the twelfth fluid port when in the second position. 
         [0017]    In yet another aspect of the present invention, the second valve is moveable between the first and second positions by a second valve solenoid assembly in fluid communication with the second valve assembly. 
         [0018]    In yet another aspect of the present invention, the third valve assembly includes a moveable third valve operable to allow fluid communication between the thirteenth fluid port and the fifteenth fluid port when in a first position, to allow fluid communication between the thirteenth fluid port and the sixteenth fluid port when in a second position, to allow fluid communication between the fourteenth fluid port and the seventeenth fluid port when in the first position, and to allow fluid communication between the fourteenth fluid port and the eighteenth fluid port when in the second position. 
         [0019]    In yet another aspect of the present invention, the third valve is moveable between the first and second positions by a third valve solenoid assembly in fluid communication with the third valve assembly. 
         [0020]    In yet another aspect of the present invention, the first, second, third, and fourth actuators are three area piston assemblies that each engage a torque transmitting device. 
         [0021]    In yet another aspect of the present invention, the first and second pressurized fluid flows contact pistons within the first, second, third, and fourth actuators in order to actuate the torque transmitting devices. 
         [0022]    Another embodiment of the hydraulic control circuit of the present invention includes a first solenoid that receives a first pressurized fluid flow, a second solenoid that receives a second pressurized fluid flow, a first valve assembly in communication with the first solenoid for selectively receiving the first pressurized fluid flow and in communication with the second solenoid for selectively receiving the second pressurized fluid flow, a first valve solenoid in communication with the first valve assembly for selectively actuating the first valve assembly, a second valve assembly in communication with the first valve assembly for selectively receiving one of the first and second pressurized fluid flows, a second valve solenoid in communication with the second valve assembly for selectively actuating the second valve assembly, a third valve assembly in communication with the first valve assembly for selectively receiving one of the first and second pressurized fluid flows, and a third valve solenoid in communication with the third valve assembly for selectively actuating the third valve assembly. A first actuator is in communication with the second valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a first pair of a plurality of gear ratios, a second actuator is in communication with the second valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a second pair of the plurality of gear ratios, a third actuator is in communication with the third valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a third pair of the plurality of gear ratios, and a fourth actuator is in communication with the third valve assembly for selectively receiving one of the first and second pressurized fluid flows for initiating one of a fourth pair of the plurality of gear ratios. The first solenoid is operable to selectively communicate the first pressurized fluid flow to the first valve assembly, the second solenoid is operable to selectively communicate the second pressurized fluid flow to the first valve assembly, the first valve assembly is operable to selectively communicate the first and second pressurized fluid flows to the second and third valve assemblies, the second valve assembly is operable to selectively communicate the first and second pressurized fluid flows to the first and second actuators, and the third valve assembly is operable to selectively communicate the first and second pressurized fluid flows to the third and fourth actuators. 
         [0023]    In one aspect of the present invention, the first valve assembly includes a moveable first valve operable to allow fluid communication between a plurality of first fluid ports in the first valve assembly, and wherein the first valve is actuatable by a third pressurized fluid flow selectively communicated from the first valve solenoid. 
         [0024]    In another aspect of the present invention, the second valve assembly includes a moveable second valve operable to allow fluid communication between a plurality of second fluid ports in the second valve assembly, and wherein the second valve is actuatable by a fourth pressurized fluid flow selectively communicated from the second valve solenoid. 
         [0025]    In yet another aspect of the present invention, the third valve assembly includes a moveable third valve operable to allow fluid communication between a plurality of third fluid ports in the third valve assembly, and wherein the third valve is actuatable by a fifth pressurized fluid flow selectively communicated from the third valve solenoid. 
         [0026]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0028]      FIG. 1  is a schematic diagram of an embodiment of a hydraulic control system for a dual clutch transmission having an actuator control subsystem according to the principles of the present invention; 
           [0029]      FIG. 2  is a schematic diagram of an embodiment of an actuator control subsystem according to the principles of the present invention; 
           [0030]      FIG. 3A  is a schematic cross-sectional view of a pair of exemplary pistons of a three area piston assembly controlled by the actuator control subsystem of the present invention; 
           [0031]      FIG. 3B  is a schematic cross-sectional view of an exemplary three area piston assembly in a first position; 
           [0032]      FIG. 3C  is a schematic cross-sectional view of an exemplary three area piston assembly in a second position; and 
           [0033]      FIG. 3D  is a schematic cross-sectional view of an exemplary three area piston assembly in a third position. 
       
    
    
     DESCRIPTION 
       [0034]    With reference to  FIG. 1 , a hydraulic control system for use in a dual clutch transmission in a motor vehicle is illustrated schematically and generally indicated by reference number  10 . The hydraulic control system  10  includes a plurality of subsystems including a line pressure subsystem  12 , a torque converter clutch (TCC) control subsystem  14 , a lubrication control subsystem  16 , an electronic limited slip differential (ELSD) subsystem  17 , a clutch control subsystem  18 , an electronic transmission range selection (ETRS) subsystem  19 , and an actuator control subsystem  20 . The hydraulic control system  10  is operable to control the dual clutch transmission, as will be described in greater detail below. Additionally, the hydraulic control system  10  may include various other subsystems without departing from the scope of the present invention. 
         [0035]    The line pressure subsystem  12  is operable to provide and regulate pressurized hydraulic fluid, such as oil, throughout the hydraulic control system  10 . Accordingly, the line pressure subsystem  12  may include various components (not shown) such as a hydraulic pump, a fluid source, a line pressure blow-off valve, a line pressure regulator valve, and/or a filter. In the example provided, the line pressure subsystem  12  includes a fluid communication channel or line passage, indicated by reference number  28 , which directly provides pressurized hydraulic fluid to the TCC control subsystem  14 , and the clutch control subsystem  18 , and the actuator control subsystem  20 . The line passage  28  is illustrated schematically in  FIG. 1  as a plurality of separate lines, however it should be appreciated that the line passage  28  may be a single continuous passage or a plurality of linked passages in series or in parallel without departing from the scope of the present invention. 
         [0036]    The TCC control subsystem  14  controls the operation of a torque converter (not shown) in the dual clutch transmission. The TCC control subsystem  16  is in direct hydraulic communication with the lubrication control subsystem  16  through a fluid passage  30 . The fluid passage  30  may be a single passage or a plurality of linked passages in series or in parallel without departing from the scope of the present invention. 
         [0037]    The lubrication control subsystem  16  provides lubrication and cooling to a variety of components throughout the dual clutch transmission. For example, the lubrication control subsystem  16  may direct hydraulic fluid through a plurality of fluid passages (not shown) to components that generate heat. 
         [0038]    The electronic limited slip differential (ELSD) subsystem  17  is operable to control an axle clutch  31  located in a differential gear box (not shown) of the motor vehicle. The axle clutch  31  is coupled to a pair of half-axles  33  which in turn are coupled to a pair of wheel assemblies  35 . The axle clutch  31  controls the difference in speed between the pairs of half-axles  33  and wheel assemblies  35  in order to eliminate the difference (or “slip”) between the pairs of half axles  33  and wheel assemblies  35 . An exemplary ELSD control subsystem is disclosed in commonly assigned U.S. patent application Ser. No. 11/950,465 filed on Dec. 5, 2007, and hereby incorporated by reference as if fully disclosed herein. 
         [0039]    The clutch control subsystem  18  is operable to control a dual clutch assembly that includes a first clutch  32  and a second clutch  34 . The clutches  32 ,  34  may be used to engage one or more input shafts or countershafts (not shown) within the dual clutch transmission and provide dynamic or “power-on” shifts by alternating engagement between the clutches  32 ,  34  and the actuator control subsystem  20 . 
         [0040]    The electronic transmission range selection (ETRS) subsystem  19  receives the shift command from a vehicle operator and in the present embodiment is a shift by wire system. The ETRS subsystem  19  is operable to control a park system  37  upon receipt of electronic control signals. The park system  37  is operable to provide at least two modes of transmission operation including a first mode or out-of-Park mode and a second mode or Park mode. While in Park mode, the park system  37  prevents the transmission from moving the vehicle by preferably locking an output shaft (not shown) of the transmission. While in out-of-Park mode, the park system  37  is disengaged and the transmission may move the vehicle by engaging any of the forward or reverse speed ratios. An exemplary ETRS control subsystem is disclosed in commonly assigned U.S. patent application Ser. No. 11/950,483 filed on Dec. 5, 2007, and hereby incorporated by reference as if fully disclosed herein. 
         [0041]    With reference to  FIG. 2 , the actuator control subsystem  20  controls the actuation of a plurality of synchronizers, clutches, and/or brakes in order to selectively engage a plurality of gear sets (not shown) within the dual clutch transmission to provide a plurality of forward and reverse speed ratios and a Neutral. The actuator control subsystem  24  includes two variable force solenoids  150 ,  152 , an odd/even actuator security valve  160 , an even actuator security valve  162 , an odd actuator security valve  164 , three on/off solenoid valves  170 ,  172 , and  174  and four “three-area” piston actuators  180 ,  182 ,  184  and  186 . 
         [0042]    Solenoid  150  includes a fluid port  195  that is in communication with the line passage  28  and a fluid port  197  that is in communication with a fluid communication passage  200 . Fluid communication passage  200  is in fluid communication with the odd/even actuator security valve  160 . Solenoid  150  is operable to communicate the pressurized hydraulic fluid from the line passage  28  to engage the 2 nd , 3 rd , 6 th , and 7 th  gear ratios of the dual clutch transmission, as will be described in greater detail below. 
         [0043]    Solenoid  152  includes a fluid port  199  that is in communication with the line passage  28  and a fluid port  201  that is in communication with a fluid communication passage  202 . Fluid communication passage  202  is in fluid communication with the odd/even actuator security valve  160 . Solenoid  152  is operable to communicate the pressurized hydraulic fluid from the line passage  28  to engage the 1 st , 4 th , 5 th , and Reverse gear ratios of the dual clutch transmission, as will be described in greater detail below. 
         [0044]    The odd/even actuator security valve  160  is operable to communicate the pressurized hydraulic fluid communicated from either of the solenoids  150 ,  152  to one of the odd or even actuator security valves  162 ,  164 . More specifically, the odd/even actuator security valve  160  includes a fluid port  203  in communication with fluid communication passage  200  and a fluid port  205  in communication with fluid communication passage  202  for receiving the pressurized hydraulic fluid from one of the solenoids  150 ,  152 . The odd/even actuator security valve  160  also includes a fluid port  207  in communication with a fluid communication passage  208 , a fluid port  210  in communication with a fluid communication passage  212 , a fluid port  214  in communication with a fluid communication passage  216 , and a fluid port  218  in communication with a fluid communication passage  220 . Fluid communication passages  212  and  220  are in communication with the even actuator security valve  162  and fluid communication passages  208  and  216  are in communication with the odd actuator security valve  164 . The odd/even actuator security valve  160  includes a valve  222  slidably disposed therein. The valve  222  is moveable between two positions in order to allow selective communication of the pressurized hydraulic fluid from fluid port  203  to fluid port  207  when in a first position and fluid port  210  when in a second position and to allow selective communication of the hydraulic fluid from fluid port  205  to fluid port  214  when in the first position and fluid port  218  when in the second position. The position of the valve  222  is controlled by activation of the solenoid  170 . 
         [0045]    The even actuator security valve  162  is operable to communicate the pressurized hydraulic fluid from the odd/even actuator security valve  160  to the actuators  180  and  182  in order to engage one of the even gear ratios (i.e., the 2 nd , 4 th , 6 th , and Reverse gear ratios) of the dual clutch transmission. More specifically, the even actuator security valve  162  includes a fluid port  230  in communication with fluid communication passage  212  and a fluid port  232  in communication with fluid communication passage  220  for receiving the pressurized hydraulic fluid from the odd/even actuator security valve  160 . The even actuator security valve  162  also includes a fluid port  238  in communication with a fluid communication passage  240 , a fluid port  242  in communication with a fluid communication passage  244 , a fluid port  246  in communication with a fluid communication passage  248 , and a fluid port  250  in communication with a fluid communication passage  252 . Fluid communication passages  244  and  252  are in communication with actuator  180  and fluid communication passages  240  and  248  are in communication with actuator  182 . The even actuator security valve  162  includes a valve  254  slidably disposed therein. The valve  254  is moveable between two positions in order to allow selective communication of the pressurized hydraulic fluid from fluid port  232  to fluid port  238  when in a first position and fluid port  242  when in a second position and to allow selective communication of the hydraulic fluid from fluid port  230  to fluid port  246  when in the first position and fluid port  250  when in the second position. The position of the valve  252  is controlled by activation of the solenoid  172 . 
         [0046]    The odd actuator security valve  164  is operable to communicate the pressurized hydraulic fluid from the odd/even actuator security valve  160  to the actuators  184  and  186  in order to engage one of the odd gear ratios (i.e., the 1 st , 3 rd , 5 th , and 7 th  gear ratios) of the dual clutch transmission. More specifically, the odd actuator security valve  164  includes a fluid port  260  in communication with fluid communication passage  208  and a fluid port  262  in communication with fluid communication passage  216  for receiving the pressurized hydraulic fluid from the odd/even actuator security valve  160 . The odd actuator security valve  164  also includes a fluid port  264  in communication with a fluid communication passage  266 , a fluid port  268  in communication with a fluid communication passage  270 , a fluid port  272  in communication with a fluid communication passage  274 , and a fluid port  276  in communication with a fluid communication passage  278 . Fluid communication passages  266  and  274  are in communication with actuator  184  and fluid communication passages  270  and  278  are in communication with actuator  186 . The odd actuator security valve  164  includes a valve  280  slidably disposed therein. The valve  280  is moveable between two positions in order to allow selective communication of the pressurized hydraulic fluid from fluid port  260  to fluid port  264  when in a first position and fluid port  268  when in a second position and to allow selective communication of the hydraulic fluid from fluid port  262  to fluid port  272  when in the first position and fluid port  276  when in the second position. The position of the valve  280  is controlled by activation of the solenoid  174 . 
         [0047]    Actuators  180 ,  182 ,  184 , and  186  are preferably three-area piston assemblies operable to each engage a torque transmitting element. With reference to  FIG. 3A-D , actuator  180  will be described in greater detail, it being appreciated that actuators  182 ,  184 , and  186  are substantially identical to actuator  180  and accordingly actuators  182 ,  184 , and  186  have corresponding components. Actuator  180  includes a first piston  286  and a second piston  288 , best seen in  FIG. 3A . The pistons  286 ,  288  are slidably disposed within a piston housing or cylinder  290 , best seen in  FIGS. 3B-D . The pistons  286 ,  288  present three separate areas  292 ,  294 , and  296 . Area  292  is located on the first piston  286  and areas  294  and  296  are located on the second piston  288 . Each area  292 ,  296 , and  298  have different sizes or surface areas. The pistons  286 ,  288  engage a finger lever  300  of a synchronizer assembly (not shown). The actuator  180  includes a fluid port  302  that communicates with the areas  292  and  294  of the pistons  286 ,  288  and a fluid port  304  that communicates with area  296  of piston  288 . Fluid port  302  is in communication with fluid communication channel  252  and fluid port  304  is in communication with fluid communication channel  244 . Accordingly, the pressurized hydraulic fluid communicated from the even actuator security valve  162  may enter the actuator  180  through one of the fluid ports  302 ,  304  and contact one of the areas  292 ,  294 ,  296  of the pistons  286 ,  288  in order to move the pistons  286 ,  288  between various positions. Each position in turn corresponds to a position of the finger lever  300  of the synchronizer assembly. For example,  FIG. 3B  illustrates the actuator  180  in a neutral position,  FIG. 3C  illustrates pressurized fluid from the fluid port  302  moving the piston  288  to the right to initiate a 6 th  4 th  gear ratio, and  FIG. 3D  illustrates pressurized fluid from the fluid port  304  moving the piston  288  to the left to initiate a 4 th  gear ratio. 
         [0048]    Returning to  FIG. 2 , actuator  182  includes a fluid port  306  in communication with fluid communication channel  240  and a fluid port  308  in communication with fluid communication channel  248 . Pressurized hydraulic fluid delivered to actuator  182  from fluid port  306  is operable to engage the Reverse gear ratio and pressurized hydraulic fluid delivered to actuator  182  from fluid port  308  is operable to engage the 2 nd  gear ratio. 
         [0049]    Actuator  184  includes a fluid port  310  in communication with fluid communication channel  266  and a fluid port  312  in communication with fluid communication channel  274 . Pressurized hydraulic fluid delivered to actuator  184  from fluid port  310  is operable to engage the 7 th  gear ratio and pressurized hydraulic fluid delivered to actuator  184  from fluid port  312  is operable to engage the 5 th  gear ratio. 
         [0050]    Actuator  186  includes a fluid port  314  in communication with fluid communication channel  278  and a fluid port  316  in communication with fluid communication channel  270 . Pressurized hydraulic fluid delivered to actuator  186  from fluid port  314  is operable to engage the 1 st  gear ratio and pressurized hydraulic fluid delivered to actuator  186  from fluid port  316  is operable to engage the 3 rd  gear ratio. While specific gear ratios for the dual clutch transmission have been associated with specific actuators  180 ,  182 ,  184 ,  186  in the embodiment provided, it should be appreciated that the specific gear ratios initiated by the actuators  180 ,  182 ,  184 ,  186  may vary without departing from the scope of the present invention and is controlled by which specific synchronizers are coupled to the actuators  180 ,  182 ,  184 ,  186 . 
         [0051]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.