Abstract:
The present invention provides improved, real time sensing of pressure supplied to the hydraulic operator of a clutch for a motor vehicle driveline power take off. A proportional sensor in the hydraulic line to the power take off clutch actuator provides a data signal in real time of the actual pressure applied to the clutch actuator. This signal is provided to the power take off control module (PCM) and/or to the transmission control module (TCM). The power take off control module, having instantaneous data regarding the pressure applied to the hydraulic operator achieves two important operating functions: monitoring and feedback.

Description:
FIELD 
       [0001]    The present disclosure relates to sensors for use with a hydraulic clutch power take off (PTO) and more particularly to proportional pressure sensors for use with heavy duty transmission hydraulic clutch driveline power take offs. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    With many heavy duty trucks having heavy duty transmissions, it is commonplace to have power take off components associated with the driveline. Such components generally comprehend a selectively engageable clutch, a drive gear, an idler gear and a driven gear that, when the clutch is engaged, transfer torque from the driveline axis to an axis offset from and parallel to the driveline axis and thence to a shaft or other torque transfer component. 
         [0004]    Typically, such clutches have hydraulic operators. Typically, as well, it is accepted power take off design practice to include a two position pressure switch associated with the hydraulic fluid pressure provided to the hydraulic clutch actuator to provide an on/off or go/no go signal to a PTO controller or other electronic control module (ECM) indicating or confirming that pressure has been applied to the clutch. While such pressure switch is set to change state at a pressure indicating assured clutch engagement, wear of such components and other variables such as fluid temperature and age can and generally will change the operating point of the clutch or switch over time. From the standpoint of accurate and repeatable information regarding the state of the power take off, this inaccuracy is undesirable. 
       SUMMARY 
       [0005]    The present invention provides improved, real time sensing of pressure supplied to the hydraulic operator of a clutch for a driveline power take off. A proportional sensor in the hydraulic line to the clutch actuator provides a data signal in real time of the actual pressure applied to the clutch actuator. This signal is provided to the power take off control module (PCM) and to the transmission control module (TCM). The power take off control module, having instantaneous data regarding the pressure applied to the hydraulic operator achieves two important operating functions: monitoring and feedback. First of all, it may confirm as well as monitor in real time that sufficient and appropriate pressure has been and is being provided to the hydraulic actuator to ensure proper clutch engagement. Second of all, the data may be utilized to adjust the pressure upward or downward to ensure proper clutch engagement. Of course, the data may be also utilized to provide a safety indication that insufficient pressure is available to engage the clutch without slipping or to engage it at all. Thus, the overall performance and safety of a power take off equipped with a proportional hydraulic clutch pressure sensor will be improved. 
         [0006]    Thus it is an aspect of the present invention to provide improved pressure sensing of pressure supplied to the hydraulic operator of a clutch for a driveline power take off. 
         [0007]    It is a further aspect of the present invention to provide improved, real time sensing of pressure supplied to the hydraulic operator of a clutch for a driveline power take off. 
         [0008]    It is a still further aspect of the present invention to provide improved, real time sensing of pressure supplied to the hydraulic operator of a clutch for a driveline power take off of a heavy duty transmission. 
         [0009]    It is a still further aspect of the present invention to provide a proportional pressure sensor for hydraulic fluid supplied to the hydraulic operator of a clutch for a driveline power take off. 
         [0010]    It is a still further aspect of the present invention to provide a real time proportional pressure sensor for hydraulic fluid supplied to the hydraulic operator of a clutch for a driveline power take off. 
         [0011]    It is a still further aspect of the present invention to provide real time proportional data from a pressure sensor for hydraulic fluid supplied to the hydraulic operator of a driveline power take off clutch to a power take off control module (PCM). 
         [0012]    It is a still further aspect of the present invention to provide a real time proportional data from a pressure sensor for hydraulic fluid supplied to the hydraulic operator of a driveline power take off clutch for heavy duty transmissions to a power take off control module (PCM). 
         [0013]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0014]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0015]      FIG. 1  is a schematic diagram of an internal combustion engine, transmission, power take off assembly and associated controls incorporating the present invention; 
           [0016]      FIG. 2  is a fragmentary section view of a power take off control valve and sensor assembly according to the present invention; 
           [0017]      FIG. 3  is a perspective view of a power take off and sensor assembly according to the present invention; and 
           [0018]      FIG. 4  is a full sectional view of a power take off assembly incorporating the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0020]    With reference to  FIG. 1 , a portion of a motor vehicle driveline assembly, typically, but not necessarily, for a heavy duty truck is illustrated and generally designated by the reference number  10 . The driveline assembly  10  includes and internal combustion engine  12  which may be a gasoline, Diesel or flex fuel engine. The output of the engine  12  is coupled to and drives a torque converter  14  which, in turn, has an output which is coupled to and drives an automatic transmission  16 . The transmission  16  includes numerous shafts, planetary gear assemblies, clutches, brakes and associated components (all not illustrated) which provide a sequence of a plurality of forward speeds or gear ratios and reverse to an output or prop shaft  18 . While the transmission  16  just described is, as noted, an automatic transmission, it should be appreciated that the invention is equally adapted to and suitable for use with a manual transmission, in which case, among other details, the torque converter is replaced by a main friction clutch. 
         [0021]    Typically, the system includes a driver interface  20  which accepts inputs such as accelerator pedal position, gear selection, power take off activation and the like from the vehicle operator (not illustrated) and provides such data and information to an engine control module (ECM)  22  which controls operation of the engine  12 . Data and information for the driver interface  20  is also provided to a power take off control module (PCM)  24 . Both the driver interface  20  and the power take off control module  24  communicate with a transmission control module (TCM)  26 . The power take off control module  24  provides control signals to and receives data and information from a power take off assembly  30 . Similarly, the transmission control module  26  provides control signals to and receives data and information from actuators and sensors within the transmission  16 . 
         [0022]    Turning now to  FIGS. 2, 3 and 4 , the torque converter  14  and the automatic transmission  16  reside within a first housing  32  and the power take off assembly  30  includes a second housing  34  which is typically cast metal and which is secured to the outside of the first, torque converter and transmission housing  32  by a plurality of threaded fasteners  36 . The engine  12  includes a shaft  38  which, as noted above, drives the input (pump) of the torque converter  14  and is thus both the output shaft of the engine  12  and the input shaft of the torque converter  14 . Thus, the shaft  38  is rotating whenever the engine  12  is operating. Secured to the shaft  38  is a first, drive chain sprocket  40  which is partially surrounded and engaged by a multi-link chain  42 . The multi-link chain  42  also partially surrounds and engages a second, driven chain sprocket  44 . The power take off housing  34  may include an access cap or cover  46  also secured by threaded fasteners  36  which protects the second, driven chain sprocket  44  and seals and closes the second, power take off housing  34  and the first, torque converter and transmission housing  32 . The second, driven chain sprocket  44  is secured to a drive shaft  50  which is supported by suitable anti-friction bearings  52 . It will be appreciated that the two chain sprockets  40  and  44  and the chain  42  may be replaced by other parallel shaft, power transfer devices such as spur or helical gears or a timing chain. In the case of gears, of course, the driven shaft, such as the drive shaft  50 , will rotate in the opposite direction from the drive shaft unless an intermediate or idler gear is also utilized. 
         [0023]    The drive shaft  50  is typically and preferably disposed on an axis parallel to and spaced from an axis of the shaft  38  of the engine  12  and the torque converter  14 . The drive shaft  50  is coupled to by, for example, interengaging splines, and drives an outer housing  58  of a friction clutch assembly  60 . The friction clutch assembly  60  includes a plurality of first or reaction discs or plates  62  coupled for rotation by interengaging splines with the outer housing  58  and a plurality of interleaved second or friction discs or plates  64  coupled by interengaging splines for rotation with an output shaft  68  to which additional shafts or couplings and equipment (not illustrated) are connected to be driven by the power take off assembly  30 . It will be appreciated that the arrangement of the reaction plates  62  and the friction discs  64  may be altered, with the friction discs  64  coupled to the outer housing  58  and the reaction plates  62  coupled to the output shaft  68 . The output shaft  68  is preferably piloted on the drive shaft  50 . The friction clutch assembly  60  also includes a hydraulic operator  70  disposed concentrically about the drive shaft  50 . 
         [0024]    Referring now to  FIGS. 2 and 4 , the hydraulic operator  70  is selectively provided with pressurized hydraulic fluid through a first or inlet passageway  72 . The first or inlet passageway  72  provides pressurized fluid to a piston  74  of the hydraulic operator  70  from a three position solenoid valve  76 . A second or supply passageway  78  provides pressurized hydraulic fluid to the solenoid valve  76  from a source such as a hydraulic pump (not illustrated) in the transmission  16 . A third passageway  82  associated with the solenoid valve  76  is an exhaust passageway which communicates with and returns hydraulic fluid to a transmission sump (not illustrated). The three position solenoid valve  76  includes a spool or plunger  84  with two lands  86  and suitable O-ring seals  88 . 
         [0025]    Also in fluid communication with the first or inlet passageway  72  and the hydraulic operator  70  is a proportional pressure sensor  90 . The pressure sensor  90  provides a continuous, typically analog, electrical output or signal from a resistance element on terminals  92  to, for example, the power take off control module (PCM)  24  directly proportional to the hydraulic pressure in the first passageway  72  and that applied to the hydraulic operator  70 . The pressure sensor  90  is secured to the housing  32  of the power take off assembly  30  by a bracket and threaded fastener  94  and includes an O-ring seal  96  or similar structure to seal the input or inlet fitting  98  of the pressure sensor  90  within the first or inlet passageway  72 . It should be appreciated that the input or inlet fitting  98  of the pressure sensor  90  may also include male threads which secure the sensor  90  in complementary female threads in the first passageway  72 . 
         [0026]    In operation, from a first, quiescent or de-energized position illustrated in  FIG. 2 , the spool  84  of the three position solenoid valve  76 , which is preferably controlled by the power take off control module  24 , is moved downward (in  FIG. 2 ) to a second position which provides pressurized hydraulic fluid to the first passageway  72  and thus to the piston  74  of the hydraulic operator  70  and the pressure sensor  90 . The actual pressure in the passageway  72  which is applied to the hydraulic operator  70  is thus measured in real time by the pressure sensor  90  and provided to the power take off control module  24 . In a third, lowermost position, the spool  84  and the lands  86  close off the second passageway  78  and connect the first passageway  72  with the third, exhaust passageway  82  to release pressure and fluid from the hydraulic operator  70  and the pressure sensor  90  and return it to the sump, thereby disengaging the friction clutch assembly  60 . 
         [0027]    It will be appreciated that the first position of the spool, illustrated in  FIG. 2  maintains fluid pressure in the passageway  72  (and the hydraulic operator  70  and the sensor  90 ) if it is moved directly from the second position to the first, quiescent or de-energized position. Thus, not only can electrical power consumption and heat generation in the solenoid valve  76  be reduced while maintaining operating hydraulic pressure on the hydraulic clutch operator  70  and engagement of the friction clutch assembly  60 , but such pressure may be monitored by the pressure sensor  90  to ensure proper pressure and engagement of the friction clutch assembly  60  are maintained. 
         [0028]    As noted above, the proportional pressure sensor  90  provides improved overall operation of the power take off assembly  30  as well as the transmission  16  by providing a constant data stream of the actual instantaneous or real time pressure applied to the friction clutch assembly  60  of the power take off assembly  30 . The pressure feedback provided by the pressure sensor  90  to the power take off control module (PCM)  24  and the transmission control module (TCM)  26  may be utilized to boost or adjust the line pressure provided to the solenoid valve  76 . It may also be utilized to provide improved diagnostics and safety during every phase of PTO operation, such as monitoring the fluid pressure prior to and during clutch engagement or to increase line pressure to increase torque transfer across the friction clutch assembly  60 . 
         [0029]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist 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.