Abstract:
A system includes a pressure sensor that measures a transmission fluid pressure at a first fluid cavity of a transmission. A transmission control module receives the transmission fluid pressure, determines a transmission fluid temperature in the first fluid cavity based on the transmission fluid pressure, and controls the transmission fluid pressure based on the transmission fluid temperature.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/040917, filed on Mar. 31, 2008. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present invention relates to vehicle transmissions, and more specifically to transmission oil measurement systems and methods. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    A transmission may have various fluid paths that carry transmission oil. For example, a pressure control device may control a source of pressurized fluid to a brake or clutch within the transmission in order to change gears or drive modes. A transmission may include a transmission control module that may control the operation of the transmission components and diagnose faults within the transmission. 
         [0005]    The operation of the transmission control module may be optimized by receiving accurate feedback regarding the operation of the transmission. Measurement of transmission oil characteristics may provide useful regarding transmission status and faults. Pressure and temperature measurements from the transmission fluid may provide information indicative of transmission status or faults based on the source of the measurements. 
       SUMMARY 
       [0006]    A system includes a pressure sensor that measures a transmission fluid pressure at a first fluid cavity of a transmission. A transmission control module receives the transmission fluid pressure, determines a transmission fluid temperature in the first fluid cavity based on the transmission fluid pressure, and controls the transmission fluid pressure based on the transmission fluid temperature. 
         [0007]    A method includes measuring a transmission fluid pressure at a first fluid cavity of a transmission with a transmission sensor, determining a transmission fluid temperature in the first fluid cavity based on the transmission fluid pressure, and controlling the transmission fluid pressure based on the transmission fluid temperature. 
         [0008]    Further 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 
         [0009]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a schematic illustration of an exemplary transmission system; 
           [0011]      FIG. 2  is a schematic illustration of an exemplary transmission oil measurement device; and 
           [0012]      FIG. 3  is a flow diagram describing steps in transmission oil measurement. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The following description is merely exemplary in nature and is in no way intended to limit the present teachings, applications, or uses. For purposes of clarity, the same reference numbers may be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality. 
         [0014]    The transmission oil measurement system and method according to the present disclosure uses a pressure sensor and a fluid temperature sensor in the same integrated circuit package to measure fluid in the same location. For example only, the pressure sensor and the temperature sensor may be located less than 2 mm apart. Accordingly, the pressure sensor and the transmission sensor share the same integrated circuit or set of integrated circuits within the same chip package, such as an ASIC. 
         [0015]    Typically, temperature sensors located within an integrated circuit package measure an internal temperature of the integrated circuit package and related components. For example, the integrated circuit package may compensate for and correct errors associated with increased temperatures. 
         [0016]    The transmission oil measurement system according to the present disclosure extrapolates the sensed temperature from the pressure sensor integrated circuit package, thereby minimizing the need for additional dedicated temperature sensors outside of the pressure sensor. Accordingly, every pressure sensor in a transmission may provide a temperature measurement in a different location of the transmission. For example, the same wired connections that communicate pressure values may be multiplexed to communicate temperature values. 
         [0017]    Referring now to  FIG. 1 , a schematic of an exemplary transmission system including fluid sensors  40 ,  42 ,  44 ,  46 , and  48  is depicted. A transmission system  10  may include transmission  12 , torque converter  14 , transmission control module  18  and pressure control system  50 . Transmission  12  may include planetary gears  16 , brake  20 , brake  22 , clutch  24 , clutch  26 , and clutch  28 . Pressure control system  50  may include sump  52 , pump  56 , pressure control devices  30 ,  32 ,  34 ,  36 , and  38 , fluid sensors  40 ,  42 ,  44 ,  46 , and  48 , sump sensor  54 , and fluid supply  60 . 
         [0018]    Torque converter  14  may receive a torque output from an engine (not shown). Torque converter  14  may transmit that torque to transmission  12 . Transmission  12  may have planetary gears  16  that change a gear ratio and a transmission status (park, neutral, drive, or reverse) based on the status of brakes  20  and  22  and clutches  24 ,  26 , and  28 . Although brakes  20  and  22  and clutches  24 ,  26 , and  28  are depicted, it should be recognized that the transmission oil measurement system described herein may operate with any fluid-controlled component of transmission  12  and that other arrangements of brakes, clutches and/or planetary gears may be used with the transmission oil measurement system described herein. 
         [0019]    Sump  52  may provide a reservoir of transmission oil fluid which may be provided from sump  52  and pressurized by pump  56 . Pump  56  may provide pressurized transmission oil to pressure control devices  30 ,  32 ,  34 ,  36 , and  38  through fluid supply  60 . Based on a signal from transmission control module  18 , pressure control devices  30 ,  32 ,  34 ,  36 , and  38  may selectively provide pressurized fluid to brakes  20  and  22  and clutches  24 ,  26 , and  28 . The pressurized fluid provided to the brakes  20  and  22  and clutches  24 ,  26 , and  28  may allow the brakes  20  and  22  and clutches  24 ,  26 , and  28  to actuate to change the present gear selection of planetary gear  16  within transmission  12 . 
         [0020]    The actual pressure of the pressurized fluid may not match a commanded or desired pressure. This pressure error may be proportional to temperature. The pressure provided by the transmission fluid may vary in a known relationship based on the temperature of the transmission fluid. Accordingly, sensors may be provided to monitor the pressure and temperature of transmission fluid. For example, pressure and temperature sensors may be located in the same integrated circuit package and directly provide temperature to the transmission control module  18 . One or more integrated circuit packages including the sensors may provide the pressure and temperature values via serial communication of digital data. The transmission control module  18  may receive temperature compensated pressure values. Alternatively, the transmission control module  18  may receive uncompensated pressure values and determine fluid temperature indirectly based on calculations, lookup tables, and/or characterized models. 
         [0021]    Sump sensor  54  may provide a status signal such as temperature to transmission control module  18 . Fluid sensors  40 ,  42 ,  44 ,  46 , and  48  may include temperature and pressure sensors and may be located in any fluid path of transmission  12  such as at each of the pressure control devices  30 ,  32 ,  34 ,  36 , and  38 . Fluid sensors  40 ,  42 ,  44 ,  46 , and  48  may come into contact with transmission oil and may be useful in monitoring transmission status and faults. For example, temperature and pressure information from a location close to the pressure control device and/or brakes  20  and  22  and clutches  24 ,  26 , and  28  may be used to match an actual fluid pressure to a desired fluid pressure. This information may also allow transmission control module  18  to confirm a brake or clutch status or to determine a fault such as if a clutch is running hot. However, it should be recognized that any of fluid sensors  40 ,  42 ,  44 ,  46 , or  48  could be located at any fluid path of transmission system  10 . 
         [0022]    Fluid sensors  40 ,  42 ,  44 ,  46 , and  48  may communicate with transmission control module  18 . Communication may be via analog signals indicating temperature and pressure or may be through serial communications. Transmission control module  18  may also receive signals from sump sensor  54 . Transmission control module  18  may provide control signals to pressure control devices  30 ,  32 ,  34 ,  36  and  38 . 
         [0023]    Referring now to  FIG. 2 , an exemplary pressure and temperature sensor  40  of sensors  40 ,  42 ,  44 ,  46 , and  48  is depicted within a fluid path of an exemplary pressure control device  30  of pressure control devices  30 ,  32 ,  34 ,  36 , and  38 . Fluid sensor  40  may include a control module  70 , pressure sensor  72 , and temperature sensor  74 . These components may be integrated or packaged in close proximity to allow measurement of pressure and temperature from a single location within the fluid path. Control module  70  may be an ASIC  70  and may be in communication with transmission control module  18 . 
         [0024]    As depicted in  FIG. 2 , fluid sensor  40  may be disposed in pressure control device  30  to come into contact with transmission oil. Pressure control device  30  may include an access port  80  that allows fluid sensor  40  to come into contact with transmission fluid. Each of pressure control devices  30 ,  32 ,  34 ,  36 , and  38  may include a respective access port  80 ,  82 ,  84 ,  86 , and  88 . It should also be recognized that if it is desired to locate fluid sensors  40 ,  42 ,  44 ,  46 , and  48  in a location other than within pressure control devices  30 ,  32 ,  34 ,  36 , and  38 , access ports  80 ,  82 ,  84 ,  86 , and  88  may be located accordingly. 
         [0025]    Access port  80  may be configured in any manner that provides fixed and sealed engagement between fluid sensor  40  and the fluid path, such as threaded engagement or a sealed press fit. An alternative to providing access ports within the fluid path may also be to provide predetermined fluid diversion paths wherein a small amount of transmission fluid is diverted from the fluid path and delivered to directly to fluid sensor  40 . 
         [0026]    The pressure sensor  72  and temperature sensor  74  of fluid sensor  40  may be separate components from ASIC  70  or one or more may be integrated into ASIC  70 . Pressure sensor  72  and temperature sensor  74  may receive accurate readings of transmission oil parameters from being in contact with the transmission oil. Pressure sensor  72  and temperature sensor  74  may provide pressure and temperature information to ASIC  70 . 
         [0027]    ASIC  70  may perform calculations and may be in communication with transmission control module  18  to send measured or calculated values to transmission control module  18 . ASIC  70  may communicate data directly or may communicate via serial communications. ASIC  70  may receive raw pressure data from pressure sensor  72  and raw temperature data from temperature sensor  74 . Calculated values may include temperature-compensated pressure data from a combination of pressure sensor  72  and temperature sensor  74  measurements. 
         [0028]    Referring now to  FIG. 3 , control logic  100  for transmission oil measurement using an integrated temperature and pressure measurement device is depicted. At block  102 , the transmission may be in a current state such as one commanded by a driver shifting the transmission. Transmission control module  18  module may receive a driver gear selection input (not shown) from the vehicle and may selectively control one or more of pressure control devices  30 ,  32 ,  34 ,  36 , and  38 . 
         [0029]    One of the selected pressure control devices may transmit pressurized transmission oil to one of brakes  20  and/or  22  based on a commanded pressure from transmission control module  18 , wherein brakes  20  and/or  22  may actuate to fix rotation of a gear within planetary gears  16 . A selected pressure control device may also provide pressurized transmission oil to one or more of clutches  24 ,  26 , and/or  28 , as commanded from transmission control module  18 . The selected clutch or clutches may engage to allow gears of planetary gears  16  to engage. In this manner, the transmission status may be changed based on a driver changing gear. Control logic  100  may continue to block  104 . 
         [0030]    At block  104 , sump sensor  54  and fluid sensors  40 ,  42 ,  44 ,  46 , and  48  may provide measurements to transmission control module  18 . The data from sump sensor  54  may include a transmission oil temperature within sump  52 . Data received from fluid sensors  40 ,  42 ,  44 ,  46 , and  48  may include pressure data, temperature-compensated pressure data, and temperature data. 
         [0031]    At block  106 , transmission control module  18  may operate transmission  12  based on the measured data from sump sensor  54  and fluid sensors  40 ,  42 ,  44 ,  46 , and  48 . For example, transmission control module  18  may monitor system faults based on temperatures measured at respective fluid sensors  40 ,  42 ,  44 ,  46 , and  48 . When located relative to a pressure control device  30 ,  32 ,  34 ,  36 , or  38 , a fluid sensor may be situated such that excess heat created by a malfunctioning brake  20  or  22  and/or clutch  24 ,  26 , or  28  may be sensed. A fault may be indicated if the measured temperature exceeds a predetermined threshold. Faults may also be indicated by temperature differences between two of sensors  40 ,  42 ,  44 ,  46 ,  48  and/or  54  exceeding a predetermined threshold. 
         [0032]    Referring again to  FIG. 2 , the transmission control module  18  may also use pressure, temperature, or a calculated temperature based on temperature-compensated and temperature uncompensated pressure readings to operate the transmission  10 . For example, transmission control module  18  may provide a commanded pressure to a pressure control device  30 ,  32 ,  34 ,  36 , or  38 . However, pressure may vary with fluid temperature such that the actual pressure is different from the commanded pressure. 
         [0033]    The transmission control module  18  may independently receive a temperature-compensated pressure and a temperature-uncompensated pressure. For example, the ASIC  70  may calculate the temperature-compensated pressure based on the measured temperature of the temperature sensor  74 . Conversely, the ASIC  70  may calculate the temperature-uncompensated pressure without considering the measured temperature of the temperature sensor  74 . The ASIC  70  transmits both the temperature-compensated and temperature-uncompensated pressures to the transmission control module  18 . 
         [0034]    The transmission control module  18  may determine a difference between the temperature-compensated and temperature-uncompensated pressures and determine the temperature of the transmission fluid based on the difference. In other words, the difference between the pressure values received from the ASIC  70  may be indicative of the transmission fluid temperature in the vicinity of the ASIC  70 . For example, the transmission control module  18  may determine the temperature based on a temperature lookup table and/or calculations that characterize and model the temperature of the transmission fluid. 
         [0035]    A relationship between the temperature and the pressure values may be based on a function of different commanded pressure regions (e.g. low, medium, and high commanded pressures), the temperature-compensated and temperature-uncompensated pressure difference, and/or an actual temperature. For example, the transmission control module  18  may use a first, second, and third lookup tables, models, or calculations for each of the low, medium, and high commanded pressures, respectively. For example only, a first pressure region may be less than 100 kPa, a second pressure region may be between 100 and 600 kPa, and a third pressure region may be greater than 600 Kpa. 
         [0036]    Accordingly, transmitting measurements of the temperature sensor  74  to the transmission control module  18  is not required. The transmission control module  18  may determine the transmission fluid temperature based on the received transmission fluid pressures. 
         [0037]    The ASIC  70  may transmit the temperature-compensated and temperature-uncompensated pressures to the transmission control module  18  using the same wire or wires (e.g. via serial and multiplexed analog and/or digital signals), and/or via wireless transmission. Communication from the ASIC  70  to the transmission control module  18  may indicate whether a particular pressure value is temperature-compensated or temperature-uncompensated. For example, data transmitted from the ASIC  70  may include one or more bits or pulses that indicate whether an associated pressure value is temperature-compensated or temperature-u ncompensated. 
         [0038]    Although the present disclosure describes pressure sensors, those skilled in the art can appreciate that any sensor that uses a temperature sensor within the same circuit package may incorporate the above described methods of extracting and extrapolation temperature, including, but not limited to, linear position sensors, torque sensors, and air flow sensors. 
         [0039]    Those skilled in the art may now appreciate from the foregoing description that the broad teachings of the present disclosure may be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.