Abstract:
Pressure transducers are incorporated as part of a transmission control unit TCU rather than placed in a remote location. This configuration eliminates the need to link the pressure transducers to the TCU via a long electrical connection, thereby shortening the signal path of the low-level signals output from the pressure transducers and reducing the complexity of the overall system. The transducers may be disposed either directly or on supports having support ports that align with pressure ports in the manifold to form fluidic paths between the manifold and the transducer.

Description:
TECHNICAL FIELD 
   The present invention relates to automatic shifting speed change transmissions employed in motor vehicles where electrically operated solenoid valves are controlled by an electronic computer for controlling the flow of pressurized fluid to transmission shift actuators employed in the transmission shifting operation. 
   BACKGROUND OF THE INVENTION 
   Electronically controlled solenoid operated valves provide improved shifting capabilities for the transmission compared to hydro-mechanical shift control and, in particular, permits staged or progressive release and application of clutches, such as band clutches and/or plate clutches, for effecting smoother speed changes in the transmission. In currently-known production transmissions, these valve assemblies are mounted internally on the transmission valve body and supplied with pressurized fluid from a pump disposed in the transmission. Shifting is performed using open loop control of the valves, which requires time-consuming and costly calibration of each valve in the transmission system. However, as the valves wear over time and as the viscosity of the transmission fluid changes due to age and contamination, the transmission system moves away from its initial calibration conditions, reducing the shifting performance of the transmission. 
   Closed loop control of solenoid operated valves has been proposed as a way to obviate the need for precise calibration of the solenoid pilot and regulating valves used for clutch engagement and line pressure regulation in an automatic speed change transmission. Preferably, closed loop control includes providing a feedback signal that indicates the torque transmitted by a particular shifting clutch band or plate to the solenoid valve. U.S. Pat. No. 6,807,472 describes a system that allows closed loop control of a transmission system by using pressure sensors to sense the hydraulic pressure to each clutch actuator and provide an electrical signal to a transmission control unit (TCU) corresponding to the sensed pressure. The TCU then determines the difference between the actual sensed pressure and a target pressure corresponding to the desired output pressure to the actuators. The TCU controls the current level or the duty-cycle sent to either a linear or pulse-width-modulated (PWM) solenoid-operated valve to control the clutch regulator valve or the clutch actuator directly until the actual pressure reaches the target pressure. This closed loop feedback ensures that the shift actuators provide smooth transmission shifting operation, even with temperature changes, valve wear, and transmission fluid contamination. 
   Piezoelectric pressure transducers are often a preferred choice in many sensing applications because of their low cost, but they pose numerous design challenges due to their non-linear response, low output signal strength, and temperature sensitivity. Thus, using piezoelectric pressure transducers requires signal amplification and correction for non-linearities. Corrections may be carried out by, for example, mixed-signal ASICs. Further, the pressure transducers must be positioned so that current can be carried from the TCU to the solenoid valves and that signals can be carried from the pressure transducers back to the TCU to effect control of valves based on the pressure transducer signals. 
   Placing discrete, isolated, single transducers in a transmission system having a signal communication interface, such as a lead frame, stamped metal traces, flex-circuits, plated circuits, a wire harness, wireless means, etc. to carry current and signals between the TCU, solenoid valves, and transducers increases the overall complexity of the system and also exposes the transducers to current spikes from the solenoids in the valves. Because the transducers output low-level signals, the noise generated by the current spikes will create unacceptable signal errors. 
   There is a desire for a transmission control unit that incorporates low-cost pressure transducers while reducing noise sensitivity and complexity. 
   SUMMARY OF THE INVENTION 
   The invention is generally directed to a TCU having a package containing a plurality of pressure transducers for pressure detection. The package includes one or more pressure transducers and a microprocessor, microcontroller, or state-machine incorporated into a single package. The package provides pressure sensing and control in a transmission system via a single device that can be easily incorporated in the transmission system. In one example, the package can be attached to the TCU in one step, connecting multiple pressure transducers to the system, instead of individually linking each pressure transducer from a remote location to the TCU. The package can shorten the signal communication path of the low-level signals output from the pressure transducer and reduces the complexity of the overall transmission system. 
   The package may be configured to have its own ports that align with pressure ports in the manifold to form fluidic paths between the manifold and the transducer. This allows the package to act as an adapter plate that can be retrofitted to an existing manifold system. As a result, the enhanced performance provided by the package can be easily provided in both new TCU designs and pre-existing TCU designs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are block diagrams of a closed loop transmission control system in which a TCU according to one embodiment of the invention can be used; 
       FIGS. 2A through 2E  illustrate section views of various embodiments of a transducer incorporated in the inventive TCU; 
       FIGS. 3A and 3B  are representative top and bottom views of a package used in a TCU according to one embodiment of the invention; 
       FIG. 4  is a representative top perspective view of a sub-package to be used in a TCU according to another embodiment of the invention; 
       FIG. 5  is a representative top perspective view of a package incorporating the sub-package shown in  FIG. 4 . 
       FIG. 6  is a representative top view of a TCU using the package of  FIG. 4  embodiment of the invention; and 
       FIG. 7  is a representative top view of a TCU according to a further embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1A and 1B  are representative block diagrams illustrating a closed-loop pressure control system  10  for a vehicle transmission in which a pressure transducer package according to the invention can be used. The system  10  may include a plurality of solenoid operated valves  12  supplied with pressurized hydraulic fluid from a pump  11 , which may be driven by a transmission input shaft. Each valve  12  supplies pressurized fluid along a conduit to a hydraulic control valve  18 , and the output of each hydraulic control valve  18  is applied through a conduit to a hydraulically actuated clutch  22 , as for example, a band clutch or plate clutch, for controlling torque transmission upon a speed (gear) change. 
   The pressure supplied to each clutch ( FIG. 1A ) or to each control valve ( FIG. 1B ) along the clutch&#39;s respective conduit  20  is sensed by a pressure transducer  24 , which provides an electrical indication of the sensed pressure, as shown by a dashed line in  FIGS. 1A and 1B , to an electronic transmission control unit (TCU)  26 . The TCU  26  also receives an input in the form of a command pressure signal from a powertrain computer  28  that is programmed to provide the desired shift characteristics for the particular vehicle and engine-transmission combination. The pressure transducers  24  may comprise any appropriate pressure sensor, such as a piezoelectric sensor. 
   In the inventive structure, one or more pressure transducers  24  are incorporated into a unitary package  30  that can be easily incorporated into the transmission system  10  (e.g., by attachment to the TCU  26 ).  FIGS. 2A through 2E  are representative section views showing various embodiments of the inventive package  30  and ways they may be incorporated into a transmission manifold. The package  30  may be encased in a plastic package housing  31  ( FIGS. 3A  though  5 ) for easy handling and protection. 
   As is known in the art, the TCU includes a manifold  50  having internal pressure ports  52 . In the illustrated embodiment, the package housing  31  sits on top of the manifold  50  and the transducers  24  are disposed in the package  30 , allowing the transducers  24  to be oriented above the manifold  50 . However, the package housing  31  may also be configured to sit on top of or be embedded in a TCU housing or a plate that is disposed on the manifold  50 . Alternatively, reference numeral  31  may be treated as the TCU housing, with the transducers  24  coupled to the TCU housing rather than the package housing. 
   As shown in  FIGS. 3A through 5 , the package  30  includes a plurality of pressure transducers  24  coupled to the substrate  61 , either directly or through a support, to form a single multiple-transducer package  30 . 
   Referring to  FIGS. 2A through 2C , the package  30  may include supports  62  integrated with a circuit card, a flex circuit, plated traces, or any other component acting as the substrate  61 . The supports  52  may be made of glass or other insulating material. The supports  62  have their own associated support ports  66  that correspond and align with the pressure ports  52  in the manifold  50  to form fluidic channels that allow fluid in the pressure ports  52  to reach the transducers  24  when the package  30  is incorporated into the transmission system  10 . As a result, the transducers  24  can generate an output based on the fluid pressure detected at its associated pressure port  52 . Alternatively, the supports  62  are omitted so that the transducers  24  are disposed directly on the substrate  61 , without any other component acting as the interface between the transducer  24  and the substrate  61 . In this case, the pressure ports  52  communicate directly with the transducers  24 . 
   The TCU  26  also includes a processor  70 , such as a microprocessor or ASIC. The processor  70  may either be incorporated in the package  30  (e.g., disposed on the substrate  61 , as shown in  FIGS. 3 through 5 ) or be the processor for the TCU  26  itself. In this example, a wire bond  68  connects each pressure transducer  24  to a corresponding electrical contact point  58  on the substrate  61  so that signals from the pressure transducer  24  can be routed elsewhere. Signals and current are routed between the TCU  26 , the transducers  24 , and the processor  70  via any desired signal communication interface, such as a lead frame, stamped metal traces, flex-circuits, plated circuits, a wire harness, wireless means, etc. Note that in some embodiments, the same component (e.g., the lead frame, etc.) will act as both the substrate  61  and the signal communication interface. 
   Regardless of the specific package configuration  30 , the alignment between the pressure ports  52  and the transducers  24  allows the package  30  to be retrofitted into any pre-existing transmission system, if desired. This allows the package  30  to be easily manufactured separately from the TCU  26  and be attached to the TCU  26  without having to reconfigure the manifold  50  to accommodate the package  30 . 
     FIG. 2A  shows one embodiment where the support  62  in the package  30  is embedded in the housing  31  of the inventive package  30 . To prevent fluid leakage, a sealing structure may be included around the pressure port  52 . In the embodiment shown in  FIG. 2A , an O-ring  80  acts as the sealing structure and is wedged between the manifold  50  and the support  58  to fluidically seal the pressure port  52 . Those of ordinary skill in the art will understand that other sealing structures, such as gasket material, may be used without departing from the scope of the invention. 
   An O-ring  80  is also used in the embodiment of  FIG. 2B , but in this case the O-ring  80  is wedged into a depression  72  in the manifold  50 . Note that in  FIG. 2B , the support  62  and the circuit card  64  are disposed on top of the package housing  31  rather than being embedded in it. Like the embodiment shown in  FIG. 2A , the arrangement of the transducers  24  on the circuit card  64  in this embodiment can be adjusted to correspond with the configuration of the pressure ports  52  in the manifold  50 . 
     FIG. 2C  shows an alternative sealing structure that does not require a separate O-ring. Instead, the support  58  has a tapered (e.g. frusto-conical) extension  82  or similar integral structure. When the support  58  is embedded into the package housing  31 , the extension  82  extends out of the package  30  below the housing  31  into the manifold  50  to form a press-fit, fluid-tight seal around the pressure port  52 . Like the embodiment of  FIG. 2B , this embodiment allows the package  30  to be manufactured separately and attached to the TCU  26  in a modular fashion. 
   Although  FIGS. 2A through 2C  show the transducers  24  disposed above the top surface of the substrate  61 , those of ordinary skill in the art will understand that the transducers  24  may be disposed on or below the bottom surface of the substrate  61  as well without departing from the scope of the invention. 
     FIG. 2D  shows an alternative structure wherein the pressure transducer  24  is disposed on the substrate  61  so that the transducer  24  can be bonded or mechanically fastened so that it communicates directly with the pressure ports  52  (e.g., bonded or mechanically fastened to the housing  31 ). This may be accomplished by, for example, placing the transducer  24  on an underside of the substrate  61  or embedding the transducer  24  in the substrate  61  to leave the transducer  24  exposed for interfacing with the pressure port  52 . The wire bonds  68  are then connected via the wire bonds  68  to the communication interface, such as a flex circuit or traces plated directly on the TCU  26 , or on an insulated interface. In this embodiment, the transducer  24  communicates directly with the pressure port  52 . Note that although the embodiment in  FIG. 2D  shows the transducer  24  incorporated in the substrate  61 , the package may also allow direct contact between the transducer  24  and the pressure port  52  by mounting the transducer  24  to the underside of the substrate  61 . 
     FIG. 2E  shows an alternative structure where the pressure transducer  24  is disposed inside an individual transducer housing  70 . The housing  70  may then directly bonded to the TCU or a subcarrier (e.g., the package housing  31 ) and the wire bonds  68  are bonded out to a communication interface on the TCU or on an insulated interface. 
   Note that although  FIGS. 2D and 2E  do not show a sealing structure, those of ordinary skill in the art will understand that any of the sealing structures shown in  FIGS. 2A through 2C  may be incorporated into the embodiments of  FIGS. 2D and 2E  without departing from the scope of the invention. 
   Regardless of the specific orientation of the transducers  24 , wire bonds or package leads  68  route signals generated by the transducer(s)  24  to a communication interface (not shown) on the substrate  61 , such as a flex-circuit or plated traces, which in turn route the signals to the processor  70  that processes the transducer signals. 
   By configuring the package  30  so that the transducers  24  are together in a single device itself rather than discrete components scattered throughout the transmission system  10 , the invention shortens the signal path between the manifold  50  and the transducers  24  and between the transducers  24  and the processor  70  reducing the complexity of the overall transmission control system and making it less sensitive to noise. 
   If the inventive package  30  is incorporated in a TCU  26 , the package  30  may use a pre-existing processor in the TCU  26  to process the transducer signals, if desired. Also, the transducers  24  may be configured in any desired fashion with the package  30 . 
     FIGS. 3A through 5  show possible transducer arrangements in the package  30 . Note that invention is not limited to these configurations and that other configurations are possible without departing from the scope of the invention. The package  30  can be built using any of the structures shown in  FIGS. 2A through 2E . As noted above, the package  30  is manufactured separately from the manifold  50  and can be connected to the manifold  50  by a harness, lead frame, or any other connector. 
     FIGS. 3A and 3B  illustrate a package configuration where the transducers  24  are arranged roughly in a circular or hexagonal shape on their respective substrates  61 . The transducers  24  and the processor  70  are housed in the package housing  31 . Optional dams  73  or filler material may be included in the package  30  to stabilize the transducers  24  and processor  70  to prevent them from becoming jarred loose over time. The package housing  30  may also include a bolt hole  74  to allow the package  30  to be attached easily to the manifold  50  with a single bolt, as shown in  FIG. 6 . 
   Because the transducers  24  and processor  70  are grouped together in a single package  30 , only four connection lines  90  (i.e., data, clock, power and ground) are needed to connect the transducers  24  to the TCU  26 . This reduces the overall length of the traces between the processor  70  and the transducers  24  and reduces the total number of connections to the TCU  26 , making the overall pressure sensing system more noise-resistant. Further, the package  30  acts as a modular component that can be attached to any manifold without reconfiguration of the manifold itself. 
     FIGS. 4 and 5  illustrate another embodiment where the package  30  includes one or more sub-packages  100 .  FIG. 4  shows one embodiment of the sub-package  100 . The sub-package  100  includes two or more of the transducers  24  and its own associated sub-package lines  102  and sub-package housing  104 . As shown in  FIG. 5 , two or more of the sub-packages  100  are disposed in the package housing  31  to form the complete package  30 . The sub-package lines  102  are coupled to package traces  104 , which are in turn connected to the connection lines  90 . In the example shown in  FIG. 5 , each sub-package  100  has its own data and clock connection lines, and the two sub-packages share power and ground lines. In this example, the package housing  31  includes two bolt holes  74  for attaching the package  30  to the TCU  26 , as shown in  FIG. 7 . Multiple packages  30  may be attached to the TCU  26  to obtain a desired number of transducers  24  in the TCU  26 . 
   Note that the sub-packages  100  may be calibrated before they are assembled into the package  30 . This makes it possible for different entities to manufacture the sub-package  100  and the finished package  100 . 
   The arrangements described above are simply illustrative examples of possible embodiments. Those of ordinary skill in the art will understand that the package can have different configurations without departing from the scope of the invention. Further, although the above examples focus on a transmission manifold, those of ordinary skill in the art will see that the inventive package can be used in any fluid pressure sensing system. 
   By incorporating one or more transducers and a processor into a single package, the inventive TCU has fluid pressure monitoring and control capabilities without requiring reconfiguration of the entire transmission manifold. Instead, fluid in the manifold can simply be redirected to the inventive package using, for example, an adapter plate that re-routes fluid to the transducers. 
   Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims