Abstract:
An easily packaged torque monitoring system accurately captures driveline torque data for use by engine, transmission or other vehicle controllers. The torque monitoring system utilizes a structural member to hydraulically connect a driving member with a driven member. A pressure-sensing device is operatively connected with a fluid chamber in the structural member through which the driving member drives the driven member. The pressure-sensing device senses a pressure level within the chamber. The amount of torque transmitted from the driving member to the driven member is directly linearly related to the sensed pressure. In one embodiment, the pressure-sensing device is a surface acoustic wave sensor in contact with the hydraulic fluid that wirelessly relays a sensor signal (i.e., a signal with a value corresponding with sensed pressure and thus with torque) to a controller.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a system of monitoring torque in a drive train based on sensed pressure.  
       BACKGROUND OF THE INVENTION  
       [0002]     Monitoring engine torque in the drive train of a vehicle allows the engine, the transmission and vehicle controls to utilize this information to modify engine output, transmission ratio as well as motor/generator speed or torque, in the case of a hybrid transmission. Known torque monitoring systems present a variety of challenges. For example, a mechanically-mounted strain gauge presents packaging challenges due to electronic wiring needed to interconnect the strain gauge with a control signal receiver and controller. Additionally, magnetorestrictive technologies used to sense torque have significant packaging issues and may be cost prohibitive.  
         [0003]     A magnetorestrictive material having magnetic characteristics that change with a change in torque requires the use of a drive line shaft or other torque-transmitting component having a nickel content that is cost prohibitive both from a material and processing standpoint. Additionally, packaging of a pick-up component, such as wire brushes, that can relay the magnetic change of the shaft, is difficult and requires additional assembly time.  
       SUMMARY OF THE INVENTION  
       [0004]     An easily packaged torque monitoring system accurately captures driveline torque data for use by engine, transmission or other vehicle controllers. The torque monitoring system utilizes a structural member to hydraulically connect a driving member with a driven member. The structural member forms at least a portion of a fluid chamber. The driving member pressurizes the fluid chamber to drive the driven member. Thus the mechanical force of the driving member is converted to hydraulic force that drives the driven member. A pressure-sensing device is operatively connected with the fluid in the fluid chamber. The pressure-sensing device senses a pressure level within the chamber. The amount of torque transmitted from the driving member to the driven member is directly linearly related to the sensed pressure.  
         [0005]     In one embodiment, the pressure-sensing device is a surface acoustic wave sensor in contact with the hydraulic fluid that wirelessly relays a sensor signal (i.e., a signal with a value corresponding with sensed pressure and thus with torque) to an electronic controller. The controller may then convert the pressure level to a torque value and provide a control signal to adjust an operating condition of the transmission, the engine or another vehicle component. The surface acoustic wave sensor may be a commercially available wireless tire pressure sensor. In another embodiment, the pressure-sensing device is a pressure regulator valve fluidly connected with the pressurized fluid chamber.  
         [0006]     The pressurized fluid chamber may be formed by a cylindrical structural member connected with a driven member, such as a plate connected for rotation with a torque converter turbine, referred to herein as a back plate. The driving member may be a flex plate connected with a piston that moves within the chamber to transfer torque via hydraulic pressure from the flex plate to the back plate.  
         [0007]     In another embodiment the pressurized fluid chamber may be formed by a flexible diaphragm connected between the driving and driven members that flexes in response to rotation of the driving member, thus pressurizing the fluid contained within the diaphragm to drive the driven number.  
         [0008]     A method of monitoring engine torque includes hydraulically connecting first and second coaxial rotatable members by providing a hydraulic chamber therebetween. The first rotatable member is driven by the engine and the second rotatable member is operatively connected with the transmission. The method includes rotating the first rotatable member to thereby rotatably drive the second rotatable member via pressure resulting in the hydraulic chamber. The method further includes sensing a level of pressure within the chamber and relaying a sensor signal representing the sensed pressure to a controller. The sensor signal may then be converted to a level of engine torque, as they are directly and linearly related. An operating condition of the engine or transmission or other vehicle component may be adjusted based on the relayed sensor signal.  
         [0009]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic fragmentary partially cross-sectional side view illustration of a vehicle drive train employing a first embodiment of a torque monitoring system within the scope of the invention (cross-section taken at arrows shown in  FIG. 2 );  
         [0011]      FIG. 2  is a schematic fragmentary illustration in front view, rotated clockwise 90 degrees with respect to  FIG. 1 ) of the torque monitoring system of  FIG. 1 ;  
         [0012]      FIG. 3  is a schematic fragmentary partially cross-sectional illustration of the torque monitoring system of  FIGS. 1 and 2  having a piston and cylinder arrangement;  
         [0013]      FIG. 4  is a schematic fragmentary partial cross-sectional illustration in view of a second embodiment of a torque monitoring system that may be employed in the vehicle drivetrain of  FIG. 1 ;  
         [0014]      FIG. 5  is a schematic fragmentary illustration in partial cross-sectional view of a third embodiment of a torque monitoring system; and  
         [0015]      FIG. 6  is a schematic cross-sectional side view illustration of a drive train utilizing the torque monitoring system of  FIG. 5 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Referring to the drawings wherein like reference numbers refer to like components, a vehicle drivetrain  10  is shown in  FIG. 1 . The drivetrain  10  includes an engine  12  connected via a torque monitoring system  14  to a torque converter  16  and a transmission  18 . Only the upper half of the drive train  10  is shown in  FIG. 1  (i.e., the portion above the axis of rotation C).  
         [0017]     The engine  12  drives an engine output shaft  20  that is bolted via bolts  22  to a flex plate  24 . The bolts  22  are received in bolt openings  23  in the flex plate  24 . Only one bolt  22  and opening  23  are shown. However, the engine output shaft  20  and flex plate  24  circumscribe the axis of rotation C and have additional bolts  22  and openings  23  distributed thereabout. The flex plate  24  is also referred to herein as a first rotatable member or a driving member. A starter gear  26  is arranged at the outer periphery of the flex plate  24  and is powered by a starter motor (not shown) to start the engine  12 .  
         [0018]     The flex plate  24  is part of the torque monitoring system  14 . The torque monitoring system  14  also includes a structural member  28  and a back plate  30 . The back plate  30  is coaxial with the flex plate  24 , is generally annular and also circumscribes the axis of rotation C. The structural member  28  is connected between the flex plate  24  and the back plate  30 . The back plate  30  may also be referred to herein as a second rotatable member or a driven member. The back plate  30  is connected via bolts  32  to a torque converter housing  34 . The torque converter  16  includes a torque converter housing  34 , a pump portion  42 , a turbine portion  44 , a stator portion  46  and a torque converter output element  48 . The torque converter housing  34  surrounds and is operatively connected for rotation with a pump portion  42  of the torque converter  14 . Operation of the torque converter  16  is known in the art. The back plate  30  is rotatably driven through the structural member  28  by rotation of the flex plate  24  as will be explained herein. The torque monitoring system  14  also includes a pressure-sensing device  40  that, in the embodiment shown in  FIG. 1 , is preferably a wireless surface acoustic wave sensor. Wireless surface acoustic wave sensors are commercially available and are used, for example, to sense tire pressure. Rotation of the back plate  30  rotates the pump portion  42  of the torque converter  16  which creates a fluid coupling to drive the turbine portion  44 . The stator portion  46  is axially centered between the pump portion  42  and turbine portion  44 . The fluid coupling between the pump portion  42  and the turbine portion  44  drives the torque converter output element  48  that is connected thereto.  
         [0019]     Transmission input shaft  50  is splined or otherwise connected for rotation with the torque converter output element  48 . Thus, the engine  12  drives the transmission  18  through the torque monitoring system  14  and the torque converter  16 . A transmission valve body  54  contains a multitude of hydraulic valves controlled by an electronic controller  56  to control torque-transmitting mechanisms such as clutches and brakes within the transmission  18 , as is known in the art. The controller  56  may receive wireless or electronic sensor signals from various components such as the engine  12  and the transmission  18 . Additionally the controller  56  may relay control signals to the transmission  18  (i.e., through the valve body  54 ) or to the engine  12 , for example, a control signal may be relayed to the engine  12  from the controller  56  along control signal wire  58 . It should be appreciated that separate controllers may be utilized for the engine  12  and the transmission  18  or a single controller may control functioning of both. The controller or controllers may instead be wirelessly connected with the respective engine and transmission.  
         [0020]     Operation of the torque monitoring system  14  of  FIG. 1  will now be described with respect to the embodiment of  FIGS. 2 and 3 . The flex plate  24  has an opening or window  60  formed, machined or otherwise provided therein. The opening or window  60  is also shown in  FIG. 1 . The back plate  30  is axially adjacent the flex plate  24  as shown in  FIG. 1 . A portion of the back plate  30  is visible through the window  60  of  FIG. 2 . The structural member  28  is supported on an extension  62  of the back plate  30 . The structural member  28  forms a chamber  64  that contains hydraulic fluid  74 . An extension  66  of the flex plate  24  forms or supports a piston  68  slidable within the chamber  64 . The structural member  28  with its fluid-filled chamber  64 , the piston  68  and extensions  62 ,  66  create a hydraulic connection along radius R within the window  60  between the flex plate  24  and back plate  30 . As may be better viewed in  FIG. 3 , a wireless sensor  40  is supported in an opening  72  in the structural member  28  such that the sensor  40  is in contact with fluid  74  contained within the chamber  64 . Thus, the wireless sensor  40  is mounted to sense hydraulically transferred torque. Mechanically mounting a surface acoustic wave torque sensor in the torque path of a vehicle driveline, i.e., a torque sensor mounted to sense torque within a rigid structural component, would be sensitive to various levels of torque acting in multiple planes of the component and is thus not well suited for driveline or vehicle controls. By isolating torque along the hydraulic connection between the flex plate  24  and the back plate  30 , this problem is avoided. Seal rings  76  prevent leakage of the fluid  74  between the structural member  28  and the piston  68 .  
         [0021]     When the engine  12  drives engine output member  20  to rotatably drive the flex plate  24  (all shown in  FIG. 1 ), the flex plate  24  drives the back plate  30  through the hydraulic connection established by the torque monitoring system  14 . Specifically, clockwise rotation of the flex plate  24  in  FIG. 2  will cause the piston  68  to pressurize the fluid  74  within the hydraulic chamber  64  to create a force on the inner surfaces of the cylindrical structure  28 . This will drive the back plate  30  in a clockwise direction as well. The back plate  30 , because it is bolted to the torque converter housing  34  (shown in  FIG. 1 ) will rotatably drive the torque converter pump portion  42  to thereby drive the turbine portion  44  and the transmission  18 . The engine output shaft  20 , the flex plate  24 , the back plate  30 , the torque converter housing  34 , the pump portion  42 , the turbine portion  44 , the torque converter output element  48  and the transmission input shaft  50  all rotate about the axis of rotation C.  
         [0022]     The pressure-sensing device  40  is in contact with the fluid  74 . As discussed above, the pressure-sensing device  40  is preferably a surface acoustic wave sensor, as known in the art, which transmits a wireless signal corresponding with the sensed pressure level of the fluid. Such wireless surface acoustic wave pressure sensors are used in vehicle tires to monitor tire pressure. Referring again to  FIG. 1 , the surface acoustic wave sensor  40  transmits a wireless sensor signal that is received by the controller  56 . The controller  56  contains a processor programmed to convert the sensor signal indicating pressure level into a corresponding torque value according to a stored algorithm. As is understood by those skilled in the art, torque of the engine conveyed through the engine output member  20  results in a force at an effective radius R measured from the axis of rotation C of the engine output member  20 . The force acts over an effective area of the cylindrical structural member  28 . The magnitude of the force is equal to the engine torque divided by the radius R, as is known in the art. The effective area is a cross-sectional area in a plane perpendicular to the force. The force results in a pressure within the chamber  64  equal to the force divided by the effective area. The pressure is thereby proportional to engine torque. The pressure-sensing device  40 , by relaying the sensed pressure value to the controller  56 , enables the controller  56  to vary operating conditions according to stored algorithms and programs in response to the sensed pressure. For example, the controller may change the degree of engine valve lift to effect engine power and torque, or may change the transmission ratio by selectively engaging a torque-transmitting mechanism or by controlling speed of a motor/generator in the case of a hybrid transmission. Because the torque monitoring system  14  allows a sensed pressure that is linearly related to engine torque, the torque monitoring system  14  permits control based upon torque values.  
         [0023]     Referring to  FIG. 4 , an alternative embodiment of a torque monitoring system  14 ′ includes an alternative structural member  28 ′ having a flexible diaphragm structure. The flexible diaphragm  28 ′ may be an elastomeric material similar to a brake booster diaphragm. First and second halves  80 ,  82  of flexible diaphragm  28 ′ are movable relative to one another. Thus, the flexible diaphragm  28 ′ flexes to allow movement of the flange portion  66 ′ of the flex plate  24 ′ toward the flange portion  62 ′ of the backing plate  30 ′ when the flex plate  24 ′ rotates, thus increasing fluid pressure within a chamber  64 ′ enclosed by the first and second halves  80 ,  82 , respectively of the diaphragm  28 ′. The pressure-sensing device  40  is supported within an opening  83  through the second half  82  of the flexible diaphragm  28 ′, allowing a portion of the sensor  40  into contact with the fluid  74 ′ to monitor the pressure thereof. As with the torque monitoring system  14  of  FIG. 2 , the hydraulic connection established by the flexible diaphragm  28 ′ allows the flex plate  24 ′ to rotatably drive the back plate  30 ′.  
         [0024]     Referring to  FIGS. 5 and 6 , a second alternative embodiment of the torque monitoring system  14 ″ is illustrated. The torque monitoring system  14 ″ utilizes hydraulic componentry to monitor pressure. As with the embodiments of  FIGS. 1 through 3 , the flex plate  24 ″ has an extension  66 ″ which forms a piston  68 ″ that is movable within a cylindrical walled structural member  28 ″ formed or supported by an extension  62 ″of the back plate  30 ″. The back plate  30 ″ is bolted to a torque converter housing  34 ″ and the flex plate  24 ″ is connected with an engine output shaft as in the embodiment of  FIG. 1 . Movement of the piston  68 ″ pressurizes fluid  74 ″ within the chamber  64 ″. A hydraulic channel  84  is formed through the back plate  30 ″ and torque converter housing  34 ″ (see  FIG. 6 ) in fluid communication with a hydraulic channel  86  in the transmission input shaft  50 ″. A portion of the housing  34 ″ extends radially inward toward the shaft  50 ″. The hydraulic channel  86  is in turn in fluid communication with a flow channel  88  through transmission housing structure  90  of the transmission  18 ″. The transmission housing structure  90  may be a center support member or outer casing of transmission  18 ″. Or any transmission member capable of having a channel routed therethrough. Alternatively, flexible tubing may be employed to establish the required fluid connections rather than channels. The pressurized fluid channel  88  is in fluid communication with a pressure regulator valve  92  contained in a valve body  54 ″. Alternative channels may be utilized to route fluid from the chamber  64 ″ to the pressure regulator valve  92 . Those skilled in the art will readily understand the operation of a pressure regulator valve to accomplish the comparison of pressure level with a known line pressure level and create a corresponding sensor signal. Hydraulic line or system pressure  94  as well as electrical power  96  is supplied to the pressure regulator valve  92  that then compares pressure supplied from the channel  98  with a known line pressure  94  to provide a control signal  98  proportional to the sensed pressure level. The sensor signal  98  may be relayed to an electronic controller  56 ″ which may then be wirelessly or otherwise connected with the engine  12  and with the transmission  18 ″ to control an operating condition thereof based upon the sensed pressure level.  
         [0025]     Referring to the structure described with respect to  FIGS. 1 through 5 , a method of monitoring engine torque includes hydraulically connecting first and second coaxial rotatable members. That is, the flex plate  24  and the back plate  30  are hydraulically connected via the enclosed fluid chamber  64  provided therebetween. A piston and cylindrical structural member design may be used as in the embodiment of  FIGS. 1-3  and that of  FIGS. 5 and 6 . Alternatively, the flexible diaphragm  83  of the embodiment of  FIG. 4  may be used. The first rotatable member of the flex plate  24  is driven by the engine  12  and the second rotatable member or back plate  30  is operatively connected with the transmission  18 . The method includes rotating the first rotatable member or flex plate  28  to thereby rotate the second rotatable member or back plate  30  via the pressure in the hydraulic chamber  64  resulting from rotation of the flex plate  28 . The method further includes sensing hydraulic pressure within the chamber  64 . A pressure-sensing device such as the wireless surface acoustic wave sensor  40  or the hydraulic pressure regulator valve  92  of the embodiments of  FIGS. 5 and 6  is utilized for the sensing step. The method further includes relaying a signal corresponding with the sensed pressure to an electronic controller  56  (or  56 ″ in the embodiment of  FIGS. 5 and 6 ). If a pressure regulator valve such as valve  92  of  FIG. 6  is utilized, relaying is accomplished by providing fluidly connected channels  84 ,  86 ,  88  in communication with the pressure regulator valve  92 .  
         [0026]     The method further includes converting the sensed pressure to a level of engine torque. Optionally, a stored algorithm within the controller  56  converts pressure levels (or sensor signals correlated with pressure levels) into a corresponding torque value. The controller  56  then calculates a control signal based on the corresponding torque value. The control signal is then relayed to the engine  12 , the transmission  18  or any other vehicle component to carry out the step of adjusting an operating condition (such as engine speed or transmission ratio) based on the sensed pressure value and corresponding engine torque.  
         [0027]     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.