Abstract:
A hydraulic control system for a transmission is provided. The hydraulic control system includes a source of pressurized hydraulic fluid that communicates with a discrete electronic transmission range selection (ETRS) subsystem. The hydraulic control system includes first and second mode valves located downstream of a hydraulic fluid pressure source. The mode valves are supplied with fluid via one or more solenoid valves or other valves. The mode valves have a plurality of ports configured to transfer pressurized hydraulic fluid. The first mode valve transfers pressurized hydraulic fluid from the source to the second mode valve. The second mode valve transfers pressurized hydraulic fluid from the first mode valve to one of drive or reverse. An electro-hydraulic circuit for pulling the transmission out of park and putting the transmission into park is also provided. A park sensor assembly including a Hall Effect sensor switch is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/652,803 filed on May 29, 2012. The disclosure of the above application is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The invention relates to a control system for an automatic transmission, and more particularly to an electro-hydraulic control system having a mechanism for electronic transmission range selection. 
     BACKGROUND 
     A typical multi-speed transmission uses several torque transmitting devices, such as friction clutches, to achieve a plurality of forward and reverse gear or speed ratios, a Neutral, and a Park. Selection of speed ratios is typically accomplished by engaging a shift lever or other driver interface device that is connected by a shifting cable or other mechanical connection to the transmission. Alternatively, the selection of speed ratios may be controlled by an electronic transmission range selection (ETRS) system, also known as a “shift by wire” system. In an ETRS system, selection of speed ratios is accomplished through electronic signals communicated between the driver interface device and the transmission. The ETRS system reduces mechanical components, increases instrument panel space, enhances styling options, and eliminates the possibility of shifter cable misalignment with the transmission range selection levers. 
     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 hydraulically actuated automatic transmission. 
     SUMMARY 
     A hydraulic control system for a transmission is provided. The hydraulic control system includes a source of pressurized hydraulic fluid that communicates with a discrete electronic transmission range selection (ETRS) subsystem. 
     The hydraulic control system includes first and second mode valves located downstream of a hydraulic fluid pressure source. The mode valves are supplied with fluid via one or more solenoid valves or other valves. The mode valves have a plurality of ports configured to transfer pressurized hydraulic fluid. The first mode valve transfers pressurized hydraulic fluid from the source to the second mode valve. The second mode valve transfers pressurized hydraulic fluid from the first mode valve to one of drive or reverse. An electro-hydraulic circuit for pulling the transmission out of park and putting the transmission into park is also provided. 
     In one aspect, which may be combined with or separate from the other aspects described herein, a hydraulic control system for a transmission is provided, wherein the transmission has a Park mode and an Out of Park mode of operation, and the transmission has a plurality of torque transmitting devices selectively engageable to provide at least one forward speed ratio and at least one reverse speed ratio when in the Out of Park mode of operation. The hydraulic control system includes a pressure regulator subsystem for providing a pressurized hydraulic fluid and a clutch control subsystem for selectively actuating the torque transmitting devices upon receipt of the pressurized hydraulic fluid. A first mode valve assembly is disposed in downstream fluid communication with the pressure regulator subsystem and in upstream fluid communication with the clutch control subsystem. A second mode valve assembly is disposed in downstream fluid communication with the first mode valve assembly and the pressure regulator subsystem and in upstream fluid communication with the clutch control subsystem. A park feed valve assembly is disposed in downstream fluid communication with the pressure regulator subsystem and the first mode valve assembly. The park feed valve assembly has a park feed valve moveable between a Park position and an Out of Park position. A park mechanism is disposed in downstream fluid communication with the park feed valve assembly and the first and second mode valve assemblies. The park mechanism is configured to place the transmission in a Park condition and an Out of Park condition. A park lock control device is connected to the park mechanism, and the park lock control device is actuatable to mechanically prevent the park mechanism from placing the transmission in a Park condition during an engine stop-start event. 
     In another aspect, which may be combined with or separate from the other aspects described herein, a hydraulic control system for a transmission is provided, wherein the transmission has a Park mode and an Out of Park mode of operation, and the transmission has a plurality of torque transmitting devices selectively engageable to provide at least one forward speed ratio and at least one reverse speed ratio when in the Out of Park mode of operation. The hydraulic control system includes a pressure regulator subsystem for providing a pressurized hydraulic fluid. A first mode valve assembly has first, second, third and fourth ports, the first and second ports being in communication with the pressure regulator subsystem. The first mode valve assembly has a first mode valve moveable between a first and a second position. A second mode valve assembly has a first port in communication with the third port of the first mode valve assembly and a second port in communication with the fourth port of the first mode valve assembly. The second mode valve assembly has a third port in communication with a Drive circuit, a fourth port in communication with a Reverse circuit, and a fifth port. The second mode valve assembly has a second mode valve moveable between a first and a second position. A park feed valve assembly has a first port in communication with the third port of the first mode valve assembly and a second port in communication with a Park circuit. The park feed valve assembly has a park feed valve moveable between a Park position and an Out of Park position. A park mechanism has a first port in communication with the second port of the park feed valve assembly and a second port in communication with the fifth port of the second mode valve assembly. The park mechanism is configured to place the transmission in a Park condition and an Out of Park condition. 
     In yet another aspect, which may be combined with or separate from the other aspects described herein, a park sensor assembly for a park mechanism of a vehicular transmission is provided. The park sensor assembly includes an actuator rod assembly configured to move the transmission into and out of park. A piston rod is connected to the actuator rod assembly through a park lever and is configured to move along an axis between a first position and a second position. One of the first and second positions corresponds to a Park position of the transmission and the other of the first and second positions corresponds to an Out of Park position of the transmission. A magnet assembly is fixed to the piston rod. A Hall Effect sensor switch is disposed adjacent to the magnet assembly. The magnet assembly and piston rod are movable with respect to the Hall Effect sensor switch. The Hall Effect sensor switch is operable to detect the magnet assembly when the piston rod is in the first position. 
     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 
       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. 1A  is a diagram of a portion of a hydraulic control system according to the principles of the present disclosure; 
       FIG.  1 Bi is a diagram of another portion of the hydraulic control system of  FIG. 1A , showing a second mode valve in a destroked position, in accordance with the principles of the present disclosure; 
         FIG. 1C  is a diagram of yet another portion of the hydraulic control system of FIGS.  1 A- 1 Bi, according to the principles of the present disclosure; 
       FIG.  1 Bii is a diagram of a portion of the hydraulic control system of  FIGS. 1A-1C , showing the second mode valve in a stroked position, according to the principles of the present disclosure; 
         FIG. 2A  is a diagram of a portion of another hydraulic control system according to the principles of the present disclosure; 
         FIG. 2B  is a diagram of another portion of the hydraulic control system of  FIG. 2A , according to the principles of the present disclosure; 
         FIG. 2C  is a diagram of yet another portion of the hydraulic control system of  FIGS. 2A-2C , in accordance with the principles of the present disclosure; 
         FIG. 3A  is a diagram of a portion of yet another hydraulic control system according to the principles of the present disclosure; 
         FIG. 3B  is a diagram of another portion of the hydraulic control system of  FIG. 3A , in accordance with the principles of the present disclosure; 
         FIG. 3C  is a diagram of yet another portion of the hydraulic control system of  FIGS. 3A-3B , according to the principles of the present disclosure; 
         FIG. 4A  is a diagram of a portion of still another hydraulic control system according to the principles of the present disclosure; 
         FIG. 4B  is a diagram of another portion of the hydraulic control system of  FIG. 4A , according to the principles of the present disclosure; 
         FIG. 4C  is a diagram of yet another portion of the hydraulic control system of  FIGS. 4A-4B , in accordance with the principles of the present disclosure; 
         FIG. 5A  is an exploded perspective view of a park mechanism, in accordance with the principles of the present disclosure; 
         FIG. 5B  is a plan view of the park mechanism of  FIG. 5A  in a first position, according to the principles of the present disclosure; and 
         FIG. 5C  is a plan view of the park mechanism of  FIGS. 5A-5B  in a second position, in accordance with the principles of the present invention. 
     
    
    
     DESCRIPTION 
     With reference to  FIG. 1 , a portion of a hydraulic control system according to the principles of the present invention is generally indicated by reference number  100 . The hydraulic control system  100  generally includes a plurality of interconnected or hydraulically communicating subsystems including a pressure regulator subsystem  102 , a clutch control subsystem  106 , and an electronic transmission range selection (ETRS) control subsystem  110 . The hydraulic control system  100  may also include various other subsystems or modules, such as a lubrication subsystem, a torque converter clutch subsystem, and/or a cooling subsystem, without departing from the scope of the present invention. 
     The pressure regulator subsystem  102  is operable to provide and regulate pressurized hydraulic fluid, such as oil, throughout the hydraulic control system  100 . The pressure regulator subsystem draws hydraulic fluid from a sump, which may be disposed at the bottom of a transmission housing to which the hydraulic fluid returns and collects from various components and regions of the transmission. The hydraulic fluid is forced from the sump and throughout the hydraulic control system  100  via a pump. The pump is preferably driven by an engine and may be, for example, a gear pump, a vane pump, a gerotor pump, or any other positive displacement pump. The pump communicates pressurized hydraulic fluid to a fluid line. The fluid line may be in communication with a spring biased one-way valve, a spring biased blow-off safety valve, and a pressure regulator valve. The control system  100  may also include a feed limit valve assembly (not shown) to limit the maximum pressure of hydraulic fluid to various subsystems and control solenoids. 
     The clutch control subsystem  106  provides hydraulic fluid to clutch actuators (not shown). The clutch actuators are hydraulically actuated pistons that each engage one of a plurality of torque transmitting devices C 1 , C 2  to achieve various forward, or drive speed ratios and reverse speed ratios. 
     The ETRS control subsystem  110  connects the pressure regulator subsystem  102  with the clutch control subsystem  106 . Generally, the ETRS control subsystem  110  converts electronic input for a requested range selection (Drive, Reverse, Park) into hydraulic and mechanical commands. The hydraulic commands use line pressure hydraulic fluid from the pressure regulator subsystem  102  via fluid line  130  to supply hydraulic fluid to the clutch actuator subsystem. The mechanical commands include engaging and disengaging a park mechanism  180 . 
     Referring to  FIG. 1 , the ETRS control subsystem  110  will now be described. The ETRS control subsystem  110  uses line pressure hydraulic fluid from the pump (or an auxiliary pump) to engage a range selection via the clutch control subsystem  106 . The ETRS control subsystem  110  is controlled using the hydraulic fluid line pressure that originates with the pump (or an auxiliary pump), or another fluid source. The ETRS control subsystem  110  includes solenoids  112 ,  114 ,  116 . Each of the solenoids  112 ,  114 ,  116  could be high flow, direct acting variable force solenoids, low flow on-off solenoids, or any other type of actuating device. In  FIG. 1 , at least one solenoid  116  is preferably a high flow, direct acting variable force solenoid. Each solenoid  112 ,  114 ,  116  may be supplied with hydraulic fluid from the pump (line pressure), or they may be fed hydraulic pressurized fluid from any other suitable fluid source. 
     The first solenoid  112  opens a fluid line  118  to supply pressurized hydraulic fluid to a first port  120 B of an enablement valve assembly  120 . The enablement valve assembly  120  includes a spool valve  122  slidably disposed within a bore  124  and four fluid ports  120 A-D. When pressurized fluid is supplied through the fluid line  118 , fluid pressure acts upon the spool valve  122  through the fluid port  120 B and compresses the spool valve  122  against a spring  126  into a stroked position, by way of example. The spool valve  122  is actuated to a stroked position or by the solenoid  112  and by hydraulic fluid acting on the spool valve  122  delivered via fluid line  118  and to a de-stroked position by the spring  126 . When the spool valve  122  of the enablement valve assembly  120  is actuated by the solenoid  112 , the fluid port  120 C communicates with the fluid port  120 D. The fluid port  120 C communicates with a fluid pressure source line  130 , and the fluid port  120 D communicates with a mode valve supply line  132 . Accordingly, when the enablement valve assembly  120  is actuated by the solenoid  112 , the fluid pressure source line  130 , such as from line pressure, communicates with the mode valve supply line  132 . Port  120 A is an exhaust port that communicates with the sump. 
     The ETRS subsystem  110  further includes first and second mode valve assemblies  134 ,  136 . The first mode valve  134  includes ports  134 A-I. Port  134 A communicates with a fluid line  138 . Port  134 C communicates with a fluid line  140 . Ports  134 D and  134 H communicate with the fluid line  132 . Port  134 E communicates with a fluid line  142 . Port  134 G communicates with a fluid line  144 . Port  134 B,  134 F, and  134 I are exhaust ports that communicate with the sump. 
     The first mode valve assembly  134  further includes a valve  146  slidably disposed within a bore  148 . The valve  146  is actuated by the solenoid  114  and a spring  150 . When solenoid  114  is opened, fluid communicates through solenoid  114 , through line  140 , and moves the valve  146  against the spring  150 . Accordingly, the valve  146  is moveable between a stroked position where the spring  150  is compressed and a de-stroked position, shown in  FIG. 1 . In the de-stroked position, as illustrated in  FIG. 1 , port  134 D communicates with port  134 E. Accordingly, the mode valve supply line  132  communicates with line  142 . From there, fluid travels to port  136 E of the second mode valve assembly  136 , which will be described in further detail below. When the first mode valve assembly  134  is de-stroked, port  134 H is closed. 
     In the stroked position, solenoid  114  is opened and fluid from line  140  contacts the valve  146  through port  134 C and moves the valve  146  against the spring  150 . In this condition, port  134 H communicates with port  134 G, and port  134 D is closed. Accordingly, when actuated, line  132  communicates with line  144 . One branch  152  of line  144  communicates with a park feed valve assembly  155 , and another branch  154  of line  144  communicates with port  136 I of the second mode valve assembly  136 . 
     In some variations, the solenoid  114  is used for other purposes within the transmission. In such a case, the solenoid  114  may not be available to actuate or to hold open the first mode valve assembly  134 . In such a case, another solenoid or valve  160  may be used to feed fluid via the fluid line  138  to the first port  134 A of the first mode valve assembly  134 . Fluid pressure within the line  162  compresses a second valve  164  located within the bore  148  of the first mode valve assembly  134 . When the second valve  164  is compressed, the valve  146  is held in the actuated position and fluidly connecting the ports  134 H and  134 G. 
     The valve  174  is moveable between a stroked position where the spring  177  is compressed (shown in FIG.  1 Bi), and a de-stroked position where the spring  177  is not compressed (shown in FIG.  1 Bii). In the de-stroked position, port  136 I communicates with port  136 H and port  136 E is blocked. Accordingly, branch  154  of line  144  communicates with line  173 , which is the drive line of the transmission. Therefore, the transmission is in “Drive” when the second mode valve assembly  136  is de-stroked, subject to the Park status. In the de-stroked position, port  136 F communicates with port  136 G and exhausts. In addition, port  136 E communicates with port  136 D. Accordingly, line  142  communicates with the “into park” line  170 , therefore sending fluid to the park mechanism  180 , which will be described in further detail below. 
     The second mode valve assembly  136  generally includes ports  136 A-M. Ports  136 B,  136 G,  136 K, and  136 M are exhaust ports that communicate with the sump. Ports  136 A and  136 J communicate with a fluid line  166 . Port  136 C communicates with fluid line  168 . Ports  136 D and  136 L communicate with a fluid line  170 . Port  136 E communicates with the fluid line  142 . Port  136 F communicates with a fluid line  172 . Port  136 H communicates with a fluid line  173 . Port  136 I communicates with the branch  154  of the fluid line  144 . The second mode valve assembly  136  includes a valve  174  slidably disposed within a bore  176 . The valve  174  is actuated by the solenoid  116 . When solenoid  116  is opened, fluid travels through line  168 , communicates through port  136 C, and moves the valve  174  against the spring  177 . 
     The valve  174  is moveable between a stroked position where the spring  177  is compressed (shown in  FIG. 1A ), and a de-stroked position where the spring  177  is not compressed (shown in  FIG. 1 ). In the de-stroked position, port  136 I communicates with port  136 H and port  136 E is blocked. Accordingly, branch  154  of line  144  communicates with line  173 , which is the drive line of the transmission. Therefore, the transmission is in “Drive” when the second mode valve assembly  136  is de-stroked, subject to the Park status. In the de-stroked position, port  136 F communicates with port  136 G and exhausts. In addition, port  136 E communicates with port  136 D. Accordingly, line  142  communicates with the “into park” line  170 , therefore sending fluid to the park mechanism  180 , which will be described in further detail below. 
     In the stroked position (see  FIG. 1A ), wherein the valve  174  is compressed against the spring  177 , the port  136 L communicates with the port  136 K and exhausts. The port  136 I communicates with the port  136 J. Accordingly, the branch  154  of the line  144  ( FIG. 1 ) communicates with the line  166 . Pressure in line  166  acts upon a second valve  178  in the bore  176  and forces the second valve  178  toward the first valve  174 , thereby closing the port  136 C. In addition, in the stroked position, port  136 H communicates with port  136 G and exhausts. Also, port  136 E communicates with port  136 F. Accordingly, line  142  communicates with line  172 , which is the “Reverse” line. Therefore, the transmission is in “Reverse” when the second mode valve assembly  136  is stroked, subject to the Park status. 
     The first mode valve assembly  134  may include a position sensor  171 , and the second mode valve assembly  136  may include a pair of position sensors  175 ,  179 , by way of example. 
     As described above, the park feed valve assembly  155  feeds fluid pressure to the “out of park” line  161 , and the port  136 D feed fluid pressure into the “into park” line  170 . Fluid lines  161  and  170  communicate with the Park servo valve  182 . The Park servo valve  182  includes ports  182 A and  182 B each located on either side of a piston  184 . The piston  184  is mechanically coupled to the park mechanism  180 . Port  182 A communicates with fluid line  170  and port  182 B communicates with fluid line  161 . The piston  184  moves upon contact by the hydraulic fluid supplied by one of the fluid lines  161 ,  170 , thereby mechanically disengaging or engaging the Park mechanism  180 . 
     The Park mechanism  180  is connected with an out-of-Park (OOP) solenoid  186 . The OOP solenoid  186  is actuatable to mechanically prevent the valve  174  from stroking and to prevent the Park mechanism  180  from engaging during an engine stop-start event (i.e. when the vehicle is intended to be mobile during an automatic engine stop). The OOP solenoid  186  may also be used to disengage the Park servo valve  182  when it is desirable to operate in Drive or Reverse at other times. 
     A park sensor assembly  201  is used to identify whether the park mechanism  180  is in park. The park sensory assembly  201  includes a Hall Effect sensor switch  202  and a magnet assembly  203 , which includes a magnet  204 , a holder  205 , and a fastener  206  (see  FIG. 5A ). The park sensor assembly is described in additional detail in  FIGS. 5A-5C  below. 
     Turning to  FIG. 2 , another embodiment of the hydraulic control system is generally indicated by reference number  200 . The hydraulic control system  200  is similar to the hydraulic control system  100  shown in  FIGS. 1-1A  and like components are indicated by like reference numbers. The first and second mode valves  134 ,  136  are the same as those described and shown with respect to  FIGS. 1-1A , and every port and line is not label specifically labeled, but should be understood to be the same as in  FIGS. 1-1A . However, the solenoid  114  and the solenoid  116  have been replaced by solenoid-valve assemblies  190 ,  192 . The solenoid-valve assembly  190  includes a low flow solenoid  194  that controls a valve  196 . The solenoid  194  actuates the valve  196 , which supplies fluid pressure to the port  134 C through the line  140 . The solenoid-valve assembly  192  includes a low flow solenoid  198  that controls a valve  199 . The solenoid  198  actuates the valve  199 , which supplies fluid pressure to the port  136 C through the line  168 . The first mode valve  134  also includes a pair of positions sensors  171 A,  171 B, in this embodiment. 
     With reference to  FIG. 3 , yet another embodiment of the hydraulic control system is generally indicated by reference number  300 . The hydraulic control system  300  is similar to the hydraulic control system  100  shown in  FIGS. 1-1A  and like components are indicated by like reference numbers. The first and second mode valves  134 ,  136  and the valve assembly  120  are the same as those described and shown with respect to  FIGS. 1-1A , and every port and line is not label specifically labeled, but should be understood to be the same as in  FIGS. 1-1A . However, the solenoid  114  has been replaced by a dedicated high flow solenoid  115 . Whereas the solenoid  114  could have been a solenoid that was used with other components, the high flow solenoid  115  is a dedicated solenoid for actuating the second mode valve assembly  134 . The first mode valve  134  also includes a pair of positions sensors  171 A,  171 B, in this embodiment. 
     With reference to  FIG. 4 , still another embodiment of the hydraulic control system is generally indicated by reference number  400 . The hydraulic control system  400  is similar to the hydraulic control system  100  shown in  FIGS. 1-1A  and like components are indicated by like reference numbers. The first and second mode valves  134 ,  136  and the valve assembly  120  are the same as those described and shown with respect to  FIGS. 1-1A , and every port, line, or other component is not specifically labeled, but should be understood to be the same as in  FIGS. 1-1A . However, the first mode valve  134  includes a pair of positions sensors  171 A,  171 B, in this embodiment, rather than a single position sensor  171 . 
     Referring now to  FIGS. 5A-5C , the park mechanism  180  and park sensor assembly  201  are illustrated in greater detail. The park piston  184  is connected to a piston rod  207 , which has the park sensor assembly  201  disposed at an end  208  thereof. The Hall Effect sensor switch  202  is connected to a stationary piston housing  209  of the piston  184  by a fastener  210  and compression limiter  211 . A park lever  212  is pivotally attached to the piston rod  207  and to an actuator rod assembly  213 , which is configured to move the transmission into and out of park. Thus, the piston rod  207  is coupled to the actuator rod assembly  213  through the park lever  212 . The magnet assembly  203  includes the magnet  204  disposed around the holder  205  (preferably formed of plastic), and the magnet assembly  203  is secured to the end  208  of the piston rod  207 , such that the magnet assembly  203  moves axially with movement of the piston rod  207 . For example, the magnet assembly  203  may be assembled to or molded over the end  208  of the piston rod  207 . 
     As shown in  FIG. 5B , when the transmission is in park, the end  208  of the piston rod  207 , having the magnet assembly  203  disposed thereon, aligns with the Hall Effect sensor switch  202 , such that the Hall Effect recognized the magnet  204  and that the transmission is in park. When the piston rod  207  is moved further away from the piston housing  209  along its longitudinal axis, as shown in  FIG. 5C , the end  208  of the piston rod  207  and the magnet assembly  203  are no longer aligned with the Hall Effect sensor switch  202 . Thus, the Hall Effect sensor switch  202  does not recognize the magnet  204 , which indicates that the transmission is not in park. 
     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.