Patent Publication Number: US-9423016-B2

Title: Hydraulic oil deterioration ratio estimating apparatus in vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2014-004683, filed Jan. 14, 2014, entitled “Hydraulic Oil Deterioration Ratio Estimating Apparatus for Vehicle.” The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a hydraulic oil deterioration ratio estimating apparatus in a vehicle. 
     2. Description of the Related Art 
     In general, engine oil used for lubricating the engine of a vehicle and hydraulic oil (ATF) used for lubricating a transmission of the vehicle deteriorates over time. Accordingly, the oil needs to be changed. Japanese Unexamined Patent Application Publication Nos. 2005-172048 and 2006-322587 describe existing technology for determining a deterioration level of ATF. 
     According to Japanese Unexamined Patent Application Publication No. 2005-172048, deterioration of ATF is caused by the following two factors: the temperature of ATF and the rotation speed. Thus, deterioration of ATF is detected using thermal deterioration based on the fluid temperature and mechanical deterioration based on the rotation speed, and an alert message is output. 
     According to Japanese Unexamined Patent Application Publication No. 2005-172048, if a fuel temperature sensor and a rotation sensor malfunctions, deterioration is estimated using a value output from the sensor that malfunctions. Thus, a significant error between an estimated deterioration value and a real deterioration value occurs. For example, if the fuel temperature sensor outputs a value lower than a real temperature, it may be determined from the estimated value that ATF is not deteriorated. In contrast, if the fuel temperature sensor outputs a value higher than the real temperature, it may be determined from the sensor value that the deterioration level is significantly high. 
     To address such an issue, according to the technology of Japanese Unexamined Patent Application Publication No. 2006-322587, it is determined whether a fuel temperature detection unit malfunctions. If the fuel temperature detection unit malfunctions, an alternative value of the fuel temperature is set, and a thermal deterioration ratio at a time of malfunction is calculated. Thus, the thermal deterioration ratio is accurately estimated. In addition, the alternative value is set to a value that is higher than the ATF temperature during normal running conditions of the vehicle by a predetermined value. Thus, the deterioration level is estimated in a fail-safe manner. Furthermore, malfunction of an engine speed detection unit, an input shaft rotation speed detection unit, and an output shaft rotation speed detection unit is detected. If malfunction of one of the detection units is detected, a mechanical ATF deterioration ratio is calculated by using an alternative value. In this manner, the ATF deterioration ratio is accurately estimated. 
     SUMMARY 
     According to one aspect of the present invention, a hydraulic oil deterioration ratio estimating apparatus for use in a vehicle includes a torque converter, an automatic transmission, an oil temperature detector, an engine speed detecting unit, an input shaft rotation speed detector, an output shaft rotation speed detector, and a hydraulic oil deterioration ratio estimating unit. The torque converter is configured to transfer a drive force of an engine to an input shaft using hydraulic oil. The automatic transmission is configured to change a rotation speed of the input shaft rotated by the drive force through hydraulic control using the hydraulic oil and output the rotation to an output shaft. The oil temperature detector is configured to detect a temperature of the hydraulic oil. The engine speed detecting unit is configured to detect an engine speed of the engine. The input shaft rotation speed detector is configured to detect a rotation speed of the input shaft of the automatic transmission. The output shaft rotation speed detector is configured to detect a rotation speed of the output shaft of the automatic transmission. The hydraulic oil deterioration ratio estimating unit is configured to estimate a deterioration ratio of the hydraulic oil. The hydraulic oil deterioration ratio estimating unit includes a first thermal deterioration ratio calculating unit configured to calculate a thermal deterioration ratio of the hydraulic oil during stoppage of the vehicle on the basis of an estimated value of a change in temperature of the hydraulic oil from stoppage of the vehicle to start of the vehicle, a second thermal deterioration ratio calculating unit configured to calculate the current thermal deterioration ratio of the hydraulic oil on the basis of the temperature of the hydraulic oil detected by the oil temperature detector, add the calculated thermal deterioration ratio to a previously calculated thermal deterioration ratio, and calculate the thermal deterioration ratio after the vehicle starts operating, a third thermal deterioration ratio calculating unit configured to calculate the current thermal deterioration ratio of the hydraulic oil by summing the thermal deterioration ratio during stoppage of the vehicle calculated by the first thermal deterioration ratio calculating unit and the thermal deterioration ratio after the vehicle starts operating calculated by the second thermal deterioration ratio calculating unit, a mechanical deterioration ratio calculating unit configured to calculate a shear rotation speed of the hydraulic oil from the engine speed detected by the engine speed detecting unit, the rotation speed of the input shaft detected by the input shaft rotation speed detector, and the rotation speed of the output shaft detected by the output shaft rotation speed detector, calculate the current mechanical deterioration ratio of the hydraulic oil on the basis of the calculated shear rotation speed, and add the mechanical deterioration ratio to a previously calculated mechanical deterioration ratio, and a deterioration ratio comparing unit configured to compare the current thermal deterioration ratio calculated by the third thermal deterioration ratio calculating unit with the mechanical deterioration ratio calculated by the mechanical deterioration ratio calculating unit and select a larger one of the current thermal deterioration ratio and the mechanical deterioration ratio as an estimated value of the deterioration ratio of the hydraulic oil. 
     According to another aspect of the present invention, a hydraulic oil deterioration ratio estimating apparatus in a vehicle includes a torque converter, an automatic transmission, an oil temperature detector, an engine speed detector, an input shaft rotation speed detector, an output shaft rotation speed detector, and a hydraulic oil deterioration ratio estimator. The torque converter is configured to transfer a drive force of an engine to an input shaft using hydraulic oil. The automatic transmission is configured to change a rotation speed of the input shaft rotated by the drive force through hydraulic control using the hydraulic oil and configured to output a rotation to an output shaft. The oil temperature detector is configured to detect a temperature of the hydraulic oil. The engine speed detector is configured to detect an engine speed of the engine. The input shaft rotation speed detector is configured to detect the rotation speed of the input shaft of the automatic transmission. The output shaft rotation speed detector is configured to detect a rotation speed of the output shaft of the automatic transmission. The hydraulic oil deterioration ratio estimator is configured to estimate a deterioration ratio of the hydraulic oil. The hydraulic oil deterioration ratio estimator includes a first thermal deterioration ratio calculator, a second thermal deterioration ratio calculator, a third thermal deterioration ratio calculator, a mechanical deterioration ratio calculator, and a deterioration ratio comparator. The first thermal deterioration ratio calculator is configured to calculate a first thermal deterioration ratio of the hydraulic oil during stoppage of the vehicle based on an estimated value of a change in temperature of the hydraulic oil from the stoppage of the vehicle to start of the vehicle. The second thermal deterioration ratio calculator is configured to calculate a first current thermal deterioration ratio of the hydraulic oil based on the temperature of the hydraulic oil detected by the oil temperature detector and configured to add the first current thermal deterioration ratio to an integrated value of the first current thermal deterioration ratio to calculate a second thermal deterioration ratio of the hydraulic oil after the vehicle starts operating. The third thermal deterioration ratio calculator is configured to sum the first thermal deterioration ratio during the stoppage of the vehicle calculated by the first thermal deterioration ratio calculator and the second thermal deterioration ratio after the vehicle starts operating calculated by the second thermal deterioration ratio calculator to calculate a second current thermal deterioration ratio of the hydraulic oil. The mechanical deterioration ratio calculator is configured to calculate a shear rotation speed of the hydraulic oil from the engine speed detected by the engine speed detector, the rotation speed of the input shaft detected by the input shaft rotation speed detector, and the rotation speed of the output shaft detected by the output shaft rotation speed detector, configured to calculate a current mechanical deterioration ratio of the hydraulic oil based on the shear rotation speed, and configured to add the current mechanical deterioration ratio to an integrated value of the current mechanical deterioration ratio to calculate a mechanical deterioration ratio of the hydraulic oil. The deterioration ratio comparator is configured to compare the second current thermal deterioration ratio calculated by the third thermal deterioration ratio calculator with the mechanical deterioration ratio calculated by the mechanical deterioration ratio calculator to select a larger one of the second current thermal deterioration ratio and the mechanical deterioration ratio as an estimated value of the deterioration ratio of the hydraulic oil. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. 
         FIG. 1  is a schematic illustration of the configuration of a vehicle having an ATF deterioration estimating apparatus mounted therein according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is a block diagram of the ATF deterioration estimating apparatus. 
         FIGS. 3A to 3C  illustrate thermal deterioration ratio tables during IG-OFF. 
         FIG. 4  illustrates a thermal deterioration acceleration coefficient table after IG-ON. 
         FIG. 5  illustrates a thermal deterioration ratio table after IG-ON. 
         FIG. 6  illustrates a mechanical ATF deterioration ratio table. 
         FIG. 7  is a flowchart illustrating the procedure for ATF deterioration estimating process. 
         FIG. 8  is a flowchart of calculation of thermal ATF deterioration during IG-OFF. 
         FIG. 9  is a flowchart of calculation of thermal ATF deterioration after IG-ON. 
         FIG. 10  is a flowchart of calculation of mechanical ATF deterioration. 
         FIG. 11  is a flowchart of an ATF deterioration estimation process. 
         FIG. 12  is a flowchart of an ATF change determination process. 
         FIG. 13  is a flowchart of an ATF deterioration resetting process. 
         FIG. 14  is a flowchart of an ATF deterioration ratio resetting process. 
         FIG. 15  illustrates resetting of an ATF deterioration ratio when ATF is changed. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. 
     Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.  FIG. 1  is a schematic illustration of the configuration of a vehicle having an ATF deterioration estimating apparatus mounted therein according to an exemplary embodiment of the present disclosure. As illustrated in  FIG. 1 , the vehicle includes an engine  2 , a crankshaft  4 , an automatic transmission (also simply referred to as a “transmission”)  6 , an ECU (a control unit)  12 , a hydraulic pressure control unit  14 , a display apparatus  16 , a fuel temperature sensor  18 , an engine rotation speed sensor  20 , a main shaft rotation speed sensor  22 , and a counter shaft rotation speed sensor  24 . 
     The crankshaft  4  of the engine  2  is connected to the transmission  6 . A torque converter (T/C)  8  disposed in the transmission  6  transfers the engine torque via ATF (hydraulic oil) which is in the form of fluid. The T/C  8  includes a pump impeller  8   b  integrated with a front cover  8   a  connected to the crankshaft  4 , a turbine runner  8   c  that is disposed between the front cover  8   a  and the pump impeller  8   b  and that faces the pump impeller  8   b , and a stator  8   d.    
     A lockup clutch  9  is disposed between the turbine runner  8   c  and the front cover  8   a . The lockup clutch  9  is pressed against the inner surface of the front cover  8   a  under the control of the hydraulic pressure control unit  14  in response to an instruction output from the ECU  12 . Thus, the lockup clutch  9  is engaged with the front cover  8   a . In contrast, if the lockup clutch  9  is unpressed, the lockup clutch  9  is disengaged from the front cover  8   a . ATF is enclosed within a container formed by the front cover  8   a  and the pump impeller  8   b.    
     The transmission  6  further includes a main shaft  10   a ,a counter shaft  10   b  disposed parallel to the main shaft  10   a , and a plurality of pairs of gears, one of which is provided on the main shaft  10   a  side and the other on the counter shaft  10   b  side (e.g., first to fifth forward gear pairs and a reverse gear pair). 
     The plurality of gear pairs are formed from input gears attached to the main shaft  10   a  and output gears attached to the counter shaft  10   b . The gears in each pair are engaged with each other at all times. 
     Either the input gear or the output gear is freely rotatable relative to the main shaft  10   a  or the counter shaft  10   b . The gear is connected and disconnected to and from the main shaft  10   a  or the counter shaft  10   b  using a synchro clutch. 
     Among the plurality of gear pairs, a high speed gear (e.g., 4th gear) and a low speed gear (e.g., 1st gear) of the forward gear pairs are illustrated in  FIG. 1  as examples. A high speed output gear  40   b  of the high speed gear pair and a low speed output gear  42   b  of the low speed gear pair are joined to the counter shaft  10   b  in an integrated manner. 
     A high speed input gear  40   a  of the high speed gear pair and a low speed input gear  42   a  of the low speed gear pair are idle gears that are rotatable about the main shaft  10   a . The high speed input gear  40   a  and the low speed input gear  42   a  are connected and disconnected to and from the main shaft  10   a  by synchro clutches  44  and  46 , respectively. 
     Each of the synchro clutches  44  and  46  is formed as, for example, a wet multi-disc clutch. The synchro clutches  44  and  46  include, respectively, outer clutch plates  44   a  and  46   a  disposed so as to be rotatable in unison with the main shaft  10   a , inner clutch plates  44   b  and  46   b  that are disposed so as to be overlapped by the outer clutch plates  44   a  and  46   a , be in contact with the outer clutch plates  44   a  and  46   a , and be rotatable in unison with the input gears  40   a  and  42   a , and hydraulic actuators (not illustrated) controlled by the ECU  12 . Note that the input gears  40   a  and  42   a  are idle gears for the main shaft  10   a.    
     Each of the hydraulic actuators has a piston that forms a piston chamber and that is disposed slidably. The hydraulic actuator generates a thrust force in accordance with the hydraulic pressure of ATF supplied to the piston chamber. Thus, the hydraulic actuator engages the outer clutch plate  44   a  with the inner clutch plate  44   b  or engages the outer clutch plate  46   a  with the inner clutch plate  46   b . In this manner, the counter shaft  10   b  is engaged with one of the input gears  40   a  and  42   a  in an integrated manner. The hydraulic pressure of ATF supplied to the piston chamber is controlled on the basis of a clutch hydraulic pressure instruction value output from the ECU  12 . Thus, the engagement state of each of the synchro clutches  44  and  46  can be controlled. 
     An output final gear  50   a  that is disposed so as to be integrated with the counter shaft  10   b  of the transmission  6  and a drive final gear  50   b  that is disposed so as to be integrated with a drive shaft  52  connected to a drive wheel W form a final gear pair. The output final gear  50   a  are engaged with the drive final gear  50   b  at all times. 
     The ECU  12  controls the hydraulic pressure of ATF for each of the lockup clutch  9  and the synchro clutches  44  and  46  using the hydraulic pressure control unit  14 . In addition, the ECU  12  controls a display operation performed by the display apparatus  16  and the operation performed on the display apparatus  16 . Furthermore, the ECU  12  performs ATF deterioration estimation and ATF deterioration ratio resetting, which are described in more detail below. The hydraulic pressure control unit  14  controls the clutch torque of each of the lockup clutch  9  and the synchro clutches  44  and  46  of the transmission  6  on the basis of an ATF hydraulic pressure instruction output from the ECU  12 . 
     The display apparatus  16  includes a display unit that displays information regarding a distance traveled, a running speed, a time, an oil change alert message, and the oil change count. The display apparatus  16  further includes an operation unit including a reset switch (not illustrated). 
     The fuel temperature sensor  18  is disposed in the transmission  6  to detect an ATF temperature TATF. The engine rotation speed sensor  20  detects a rotation speed Ne of the crankshaft  4  of the engine  2 . The main shaft rotation speed sensor  22  serves as an input shaft rotation speed detector that detects a rotation speed Nm of the main shaft  10   a . The counter shaft rotation speed sensor  24  serves as an output shaft rotation speed detector that detects a rotation speed Nc of the counter shaft  10   b . The detection signals output from the sensors  18 ,  20 ,  22 , and  24  are input to the ECU  12 . 
     The vehicle has an ignition switch (IG switch)  26  mounted therein. The IG switch  26  is operated by a driver to start and stop the vehicle (the engine  2 ). In addition, the vehicle includes an IG switch sensor  28  that detects ON/OFF of the IG switch  26 . The detection signal output from the IG switch sensor  28  is input to the ECU  12 . The vehicle starts operating when the driver turns on the IG switch  26  (IG-ON) and stops operating when the driver turns off the IG switch  26  (IG-OFF). 
     The vehicle further includes an ambient temperature sensor  29  that detects the ambient temperature. A detection signal output from the ambient temperature sensor  29  is input to the ECU  12 . 
       FIG. 2  is a block diagram of an ATF deterioration estimating apparatus included in the ECU  12  according to the present disclosure. The function of the ATF deterioration estimating apparatus is realized by, for example, the ECU  12  executing a program stored in a ROM (not illustrated) of the ECU  12 . The ATF deterioration estimating apparatus includes a data storage unit  100 , a data reading unit  102 , a data writing unit  104 , and an IG-OFF-period thermal deterioration ratio table  105 , a thermal deterioration acceleration coefficient table  106 , a post-IG-ON thermal deterioration ratio table  108 , and a mechanical ATF deterioration ratio table  110  stored in the ROM. The ATF deterioration estimating apparatus further includes an IG-OFF-period thermal deterioration ratio calculating unit (a first thermal deterioration ratio calculating unit)  118 , a post-IG-ON thermal deterioration ratio calculating unit (a second thermal deterioration ratio calculating unit)  120 , a thermal deterioration ratio adder unit (a third thermal deterioration ratio calculating unit)  123 , a mechanical deterioration ratio calculating unit  122 , an ATF deterioration estimating unit  124 , an ATF change determination unit  126 , and an ATF deterioration resetting unit  128 . 
     The data storage unit  100  is an electrically erasable programmable read-only memory (EEPROM) that stores a distance traveled VCRUN, an ATF change flag F_CHANGEATF, an ATF change count ATFCNT, and ATF data used for ATF deterioration estimation, such as a thermal ATF deterioration LOILH (LOILH 1 +LOILH 2 ) and a mechanical ATF deterioration LOILR. 
     The data reading unit  102  reads VCRUN, LOILH, and LOILR from the data storage unit  100  when the engine  2  starts due to IG-ON. The data writing unit  104  writes, to the data storage unit  100 , LOILH and LOILR obtained when the engine  2  stops due to IG-OFF. 
       FIGS. 3A to 3C  illustrate the IG-OFF-period thermal deterioration ratio table  105 . More specifically,  FIG. 3A  illustrates an ATF temperature (estimated value) table indicating the ATF temperature vs. an elapsed time from IG-OFF.  FIG. 3B  illustrates a thermal deterioration ratio table indicating thermal deterioration per unit time vs. an ATF temperature (a fuel temperature).  FIG. 3C  illustrates a thermal deterioration ratio (integrated value) table indicating a thermal deterioration ratio (an integrated value) vs. an elapsed time from IG-OFF. 
     As illustrated in  FIG. 3A , in the ATF temperature (estimated value) table indicating the ATF temperature vs. an elapsed time from IG-OFF, the abscissa represents an elapsed time t (sec) (a time period over which ATF is left unused) from IG-OFF, and the ordinate represents an ATF temperature T (° C.). By using Newton&#39;s law of cooling, the ATF temperature T with respect to the elapsed time t from IG-OFF can be expressed as follows: 
     
       
         
           
             
               
                 
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     In equation (1), t represents the elapsed time (sec) from IG-OFF (a time period over which ATF is left unused), T 0  represents the ATF temperature (° C.) when t=0 (immediately after IG-OFF), T represents the ATF temperature (° C.) at a time t, Tm represents the ambient temperature (° C.), and αS/C represents the cooling characteristic coefficient of the vehicle. The cooling characteristic coefficient αS/C is determined from the heat dissipation characteristics of equipment, such as the torque converter  8  and the transmission  6 . The ambient temperature Tm can be detected using the ambient temperature sensor  29 . Note that if the vehicle does not include the ambient temperature sensor  29 , the ambient temperature Tm can be obtained immediately after IG-ON by using the following equation: 
     
       
         
           
             
               
                 
                   
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     As illustrated in  FIG. 3B , in the thermal deterioration ratio table indicating a thermal deterioration ratio per unit time vs. an ATF temperature, the abscissa represents the ATF temperature (TATF), and the ordinate represents the thermal deterioration ratio per unit time of ATF (DTLOILH 1 ) (%). When the ATF temperature TATF varies from T to T 0 , the thermal deterioration ratio per unit time DTLOILH 1  is calculated using this table. As can be seen from  FIG. 3B , the thermal deterioration ratio DTLOILH 1  of ATF increases with increasing ATF temperature TATF. 
     As illustrated in  FIG. 3C , in the thermal deterioration ratio table indicating a thermal deterioration ratio vs. an elapsed time from IG-OFF, the abscissa represents an elapsed time from IG-OFF (a time period over which ATF is left unused) t (sec), and the ordinate represents the thermal deterioration ratio of ATF (the integrated value) (LOILH 1 ) (%). In this table, an integrated value LOILH 1  of the thermal deterioration ratio over the elapsed time from IG-OFF is calculated using the ATF temperature TATF for the elapsed time from IG-OFF calculated in  FIG. 3A  and the thermal deterioration ratio per unit time DTLOILH 1  for the ATF temperature TATF calculated in  FIG. 3B . That is, the area of a portion X with hatchings in the graph illustrated in  FIG. 3C  represents the integrated value LOILH 1  of the thermal deterioration ratio for the elapsed time from IG-OFF. 
       FIG. 4  illustrates the thermal deterioration acceleration coefficient table  106  after IG-ON. The abscissa represents the amount of heat generation of ATF in the T/C  8  (DQOILTC), and the ordinate represents the thermal deterioration acceleration coefficient (KLOILH). As can be seen from  FIG. 4 , KLOILH is a value determined in accordance with DQOILTC. In particular, if DQOILTC is within a predetermined range, deterioration of ATF is accelerated. Note that as described below, DQOILTC can be calculated from, for example, Ne, Nm, and the amplification factor of the T/C  8 . 
       FIG. 5  illustrates the post-IG-ON thermal deterioration ratio table  108 . In  FIG. 5 , the abscissa represents the fuel temperature (TATF), and the ordinate represents the thermal deterioration ratio (%) (DTLOILH2). As can be seen from  FIG. 5 , DTLOILH 2  is a value determined in accordance with TATF. In particular, deterioration of ATF progresses with increasing TATF. 
       FIG. 6  illustrates the mechanical ATF deterioration ratio table  110 . In  FIG. 6 , the abscissa represents the shear rotation (TREV), and the ordinate represents the kinetic viscosity deterioration ratio (%) (DTLOILR). As can be seen from  FIG. 6 , DTLOILR is a value determined in accordance with TREV. In particular, deterioration of ATF progresses with increasing TREV. 
     The IG-OFF-period thermal deterioration ratio calculating unit  118  calculates the thermal deterioration ratio (the integrated value) LOILH 1  during IG-OFF using the elapsed time from IG-OFF (the time period over which ATF is left unused) t (sec), the ATF temperature To (° C.) when t=0 (immediately after IG-OFF), the ATF temperature T (° C.) at a time t, and the ambient temperature Tm (° C.) in the tables illustrated in  FIGS. 3A to 3C . 
     The post-IG-ON thermal deterioration ratio calculating unit  120  calculates DQOILTC using, for example, Ne and Nm and searches the thermal deterioration acceleration coefficient table  106  using the calculated DQOILTC. Thus, the post-IG-ON thermal deterioration ratio calculating unit  120  calculates KLOILH 2 . Thereafter, the post-IG-ON thermal deterioration ratio calculating unit  120  searches the post-IG-ON thermal deterioration ratio table  108  using TATF to calculate the DTLOILH 2  and assigns (the previous LOILH 2 +DTLOILH 2 *KLOILH 2 ) to the thermal ATF deterioration LOILH 2 . 
     The thermal deterioration ratio adder unit  123  sums the ATF thermal deterioration ratio (the thermal ATF deterioration) LOILH 1  during IG-OFF calculated by the IG-OFF-period thermal deterioration ratio calculating unit  118  and the ATF thermal deterioration ratio (the thermal ATF deterioration) LOILH 2  after IG-ON calculated by the post-IG-ON thermal deterioration ratio calculating unit  120 . 
     The mechanical deterioration ratio calculating unit  122  calculates TREV using Ne, Nm, and Nc and searches the mechanical ATF deterioration ratio table  110  using the calculated TREV. Thus, the mechanical deterioration ratio calculating unit  122  calculates the mechanical ATF deterioration ratio DTLOILR and assigns (the previous LOILR+DTLOILR) to the mechanical ATF deterioration LOILR. 
     The ATF deterioration estimating unit  124  assigns the larger one of the sum of the thermal ATF deterioration LOILL 1  during IG-OFF and the thermal ATF deterioration LOILL 2  after IG-ON and the mechanical ATF deterioration LOILR to an ATF deterioration estimated value LOIL. The ATF change determination unit  126  calculates VCRUN using, for example, Nc. Thereafter, the ATF change determination unit  126  compares VCRUN with each of a maximum distance of the warranty coverage and a minimum distance of the warranty coverage and compares LOIL with an ATF change threshold value so as to determine whether an ATF change time is reached. If an ATF change time is not reached, the ATF change determination unit  126  assigns a no-change-required value ‘0’ to the ATF change flag F_CHANGEATF. However, if the ATF change time is reached, the ATF change determination unit  126  assigns a change-required value ‘1’ to the ATF change flag F_CHANGEATF and displays an ATF change alert message on the display apparatus  16 . 
     The IG-OFF-period thermal deterioration ratio calculating unit  118  calculates LOILH 1  immediately after the engine  2  starts by IG-ON. In contrast, the post-IG-ON thermal deterioration ratio calculating unit  120  and the mechanical deterioration ratio calculating unit  122  calculate LOILH 2  and LOILR and the ATF deterioration estimating unit  124  estimates ATF deterioration at predetermined intervals (e.g., 1-second intervals) between start of the engine  2  by IG-ON and stoppage of the engine  2  by IG-OFF. 
     The ATF deterioration resetting unit  128  starts operating when a reset switch of the display apparatus  16  is pressed by an operator after ATF is changed or when a reset operation is performed by an operator using a PGM tester. In ATF change, a certain percent (e.g., about 40%) of old deteriorated ATF may remain inside the T/C  8  and a hydraulic control system. Accordingly, the ATF deterioration resetting unit  128  assigns an ATF deterioration reset value (a non-zero value) to LOILH 1 , LOILH 2 , and LOILR, assigns ‘0’ to VCRUN, and assigns ‘0’ to F_CHNGEATF and TATFFAIL. In addition, the ATF deterioration resetting unit  128  turns off the ATF change alert display and a fail alert display of, for example, TATF and increments ATFCNT by one. These values are written to the data storage unit  100 . 
     If 60% of ATF is changeable and 40% of ATF is unchangeable, the ATF deterioration resetting unit  128  sets the ATF deterioration reset value to 0.4 (i.e., 40%). Alternatively, if, for example, the amount of remaining deteriorated ATF is 40% of the whole ATF and the deterioration ratio of the remaining deteriorated ATF is 50%, the ATF deterioration reset value is set to 0.4*0.5=0.2 (i.e., 20%). 
       FIGS. 7 to 12  are flowcharts illustrating an example of an ATF deterioration estimating operation according to the present disclosure.  FIGS. 13 and 14  are flowcharts illustrating an example of an ATF deterioration resetting operation.  FIG. 15  is a graph illustrating the ATF deterioration ratio in which the abscissa represents a distance traveled and the ordinate represents the ATF deterioration ratio LOIL. 
     In step S 10  illustrated in  FIG. 7 , it is determined whether the engine  2  is started, that is, whether the ignition switch is turned on (IG-ON). The determination is positive (YES) only for the first time after the engine  2  is started by IG-ON. The next determination and the subsequent determinations are negative (NO). 
     If the determination is positive (YES), the processing proceeds to step S 12 , where VCRUN, LOILH, and LOILR are read from the data storage unit  100 . However, if the determination in step S 10  is negative (NO), the processing proceeds to step S 14 , where it is determined whether IG-OFF occurs (the engine  2  is stopped). If IG-OFF does not occur (the engine  2  is not stopped), that is, IG-ON occurs (the engine  2  is running), the processing proceeds to step S 15 , where it is determined whether the thermal ATF deterioration during IG-OFF is corrected. If the thermal ATF deterioration during IG-OFF is not corrected (NO), the processing proceeds to step S 16 , where the thermal ATF deterioration during IG-OFF is calculated. 
     In step S 16 , the thermal ATF deterioration during IG-OFF is calculated, as illustrated in  FIG. 8 . That is, in step S 36 , the elapsed time t (the time period over which ATF is left unused) from IG-OFF to IG-ON is obtained, and the ATF temperature To and the ambient temperature Tm at a time of IG-OFF are obtained. In step S 38 , the thermal deterioration ratios per unit time during the elapsed time from t=0 to t are summed. Thus, the thermal ATF deterioration for the ATF temperature during the elapsed time from t=0 to t is calculated. 
     If the thermal ATF deterioration during IG-OFF is calculated in step S 16  or if the thermal ATF deterioration during IG-OFF is corrected in step S 15  (YES), the processing proceeds to step S 17 , where the thermal ATF deterioration after IG-ON is calculated. The calculation of the thermal ATF deterioration after IG-ON in step S 17  is performed as illustrated in  FIG. 9 . 
     In step S 56  illustrated in  FIG. 9 , the amount of heat generation of ATF in the T/C  8  is calculated. That is, let DQOILTC be the amount of heat generation of ATF in the T/C  8 . Then, DQOILTC can be calculated as follows:
 
 DQOILTC=|TQ IN* Ne−TQ OUT* Nm| 
 
where
         TQIN: T/C pump absorption torque (input torque),   TQOUT: T/C turbine torque (output torque),   Ne: engine speed, and   Nm: main shaft rotation speed.       

     TQIN and TQOUT can be expressed as follows:
 
 TQ IN=τ*( Ne/ 1000)2*9.8*2*3.14/60, and
 
 TQ OUT= KTR *( TQ IN).
 
Accordingly,
 
 DQOILTC=|TQ IN( Ne−KTR*Nm )|=|τ*( Ne/ 1000)2*( Ne−KTR×Nm )|*9.8*2*3.14/60,
 
where τ: T/C pump absorption torque coefficient, and
         KTR: T/C torque ratio.       

     Subsequently, in step S 58 , the thermal deterioration acceleration coefficient table  106  is searched to obtain the thermal deterioration acceleration coefficient KLOILH corresponding to the amount of heat generation of ATF in the T/C  8 . Thereafter, the processing proceeds to step S 64 . 
     In step S 64 , the post-IG-ON thermal deterioration ratio table  108  is searched using TATF to detect the ATF thermal deterioration ratio DTLOILH. 
     Subsequently, the processing proceeds to step S 66 , where the thermal ATF deterioration LOILH is calculated. That is, (the previous LOILH+DTLOILH*KLOILH) is assigned to LOILH. Thereafter, the processing returns to step S 18  in  FIG. 7 . 
     In step S 18 , the mechanical ATF deterioration LOILR illustrated in  FIG. 10  is calculated. In step S 112  illustrated in  FIG. 10 , the shear rotation speed TREV is calculated on the basis of Ne, Nm, and Nc. 
     That is, the following calculation is performed:
 
 TREV=Ne×K 1 +Nm×K 2 +Nc×K 3,
 
where each of K 1 , K 2 , and K 3  denotes a coefficient for correcting the influence level for mechanical deterioration of a rotating part. K 1 , K 2 , and K 3  are determined on the basis of, for example, the numbers of gear tooth and the numbers of bearings of rotation members.
 
     Subsequently, the processing proceeds to step S 114 , where the mechanical ATF deterioration ratio table  110  is searched using TREV to calculate the mechanical ATF deterioration ratio DTLOILR corresponding to TREV. 
     Subsequently, the processing proceeds to step S 116 , where the mechanical ATF deterioration LOILR is calculated. That is, (the previous LOILR+DTLOILR) is assigned to LOILR. Thereafter, the processing returns to step S 20  illustrated in  FIG. 7 . 
     In step S 20 , the ATF deterioration estimating process illustrated in  FIG. 11  is performed. As illustrated in  FIG. 11 , in step S 150 , it is determined whether the thermal ATF deterioration LOILH (LOILH 1 +LOILH 2 )&gt;the mechanical ATF deterioration LOILR. If the determination is positive (YES), the processing proceeds to step S 152 , where the thermal ATF deterioration LOILH (LOILH 1 +LOILH 2 ) is assigned to the ATF deterioration LOIL. However, if the determination is negative (NO), the processing proceeds to step S 154 , where the mechanical ATF deterioration LOILR is assigned to the ATF deterioration LOIL. Thereafter, the processing returns to step S 22  illustrated in  FIG. 7 . 
     In step S 22 , the ATF change determination process illustrated in  FIG. 12  is performed. As illustrated in  FIG. 12 , in step S 200 , the distance traveled is calculated on the basis of Nc. That is, let RATIO be the final gear ratio, and let RTIRE be the radius of the tire. Then, the distance traveled is expressed as follows:
 
distance traveled=vehicle speed×time.
 
Since vehicle speed=(tire rotation speed per unit time)×distance traveled per tire rotation=(Nc/RATIO)×(2π×RTIRE), the previous VCRUN+vehicle speed (the distance per second) is assigned to VCRUN.
 
     In step S 202 , it is determined whether VCRUN is greater than a maximum distance of the warranty coverage. If the determination in step S 202  is negative (NO), the processing proceeds to step S 204 , where it is determined whether the distance traveled VCRUN is less than a minimum distance of the warranty coverage. 
     If the determination in step S 204  is negative (NO), the processing proceeds to step S 206 , where it is determined whether the ATF deterioration is greater than an ATF change threshold value. If it is determined that the ATF deterioration is greater than the ATF change threshold value, the processing proceeds to step S 210 , where “1” is assigned to the ATF change flag F_CHANGEATF and, in addition, an ATF change alert message is displayed on the display apparatus  16 . However, if the determination in step S 206  is negative (NO), “0” is assigned to the ATF change flag F_CHANGEATF in step S 208 . 
     In contrast, if, in step S 202 , it is determined that the distance traveled VCRUN is greater than a maximum distance of the warranty coverage (YES), the processing proceeds to step S 210 , where “1” is assigned to the ATF change flag F_CHANGEATF and, in addition, an ATF change alert message is displayed on the display apparatus  16 . However, if, in step S 204 , it is determined that the distance traveled VCRUN is less than the minimum distance of the warranty coverage (YES), the processing proceeds to step S 208 , where “0” is assigned to the ATF change flag F_CHANGEATF. Thereafter, the processing returns to step S 10  illustrated in  FIG. 7 . The processes in steps S 10  to S 22  are repeated at predetermined intervals (1-second intervals). 
     If, in step S 14  of  FIG. 7 , it is determined that the engine  2  is shut down by IG-OFF, the processing proceeds to step S 24 , where LOILH (LOILH+LOILH 2 ), LOILR, F_CHANGEATF, TATFFAIL to NcFAIL, and VCRUN are written to the data storage unit  100 . Thereafter, the processing is completed. 
     Since the ATF change alert message is displayed on the display apparatus  16 , the operator changes ATF. After the ATF change is completed, the operator turns on the reset switch of the display apparatus  16 . In step S 250  illustrated in  FIG. 13 , it is determined whether the reset switch of the display apparatus  16  is turned on. If the determination is positive (YES), the processing proceeds to step S 252 . However, if the determination is negative (NO), the processing is completed. In step S 252 , the ATF deterioration resetting process illustrated in  FIG. 14  is performed. 
     As illustrated in  FIG. 14 , in step S 300 , the ATF deterioration reset value (e.g., 0.4) is assigned to LOILH. Thereafter, the processing proceeds to step S 302 . In step S 302 , the ATF deterioration reset value (e.g., 0.4) is assigned to LOILR, and the processing proceeds to step S 304 . In step S 304 , LOILH and LOILR are written to the data storage unit  100 . Thereafter, the processing returns to step S 254  illustrated in  FIG. 11 . As illustrated in  FIG. 15 , when ATF is changed, the ATF deterioration ratio is reset to, for example, 0.4 (i.e., 40%) on the basis of the remaining amount of deteriorated ATF. Accordingly, the deterioration of ATF is not underestimated. 
     When ATF is changed, it is difficult to change ATF inside the torque converter and the hydraulic control system and, thus, the change ratio is not 100%. Accordingly, even when ATF is changed, the deteriorated ATF still remains and, thus, the ATF deterioration ratio is not 0. Consequently, if the deterioration estimated value is reset to 0 when ATF is changed, a significant error occurs between the deterioration ratio and the real deterioration ratio. Thus, according to the present exemplary embodiment, when ATF is changed, the ATF deterioration ratio is reset to an appropriate value based on the remaining amount of deteriorated ATF. 
     As illustrated in  FIG. 13 , in step S 254 , ‘0’ is assigned to the distance traveled VCRUN, which is written to the data storage unit  100 . In step S 256 , ‘0’ is assigned to F_CHANGEATF, which is written to the data storage unit  100 . In step S 258 , the ATF change alert message displayed on the display apparatus  16  is cleared. In step S 260 , the ATF change count ATFCNT is incremented by one and is written to the data storage unit  100 . 
     As described above, according to the present exemplary embodiment, the hydraulic oil deterioration ratio estimating apparatus includes the thermal deterioration ratio calculating unit (the first thermal deterioration ratio calculating unit)  118  configured to calculate a thermal deterioration ratio of the hydraulic oil during stoppage of the vehicle (during IG-OFF) on the basis of an estimated value of a change in temperature of the hydraulic oil from the previous stoppage of the vehicle to start of the vehicle, the thermal deterioration ratio calculating unit (the second thermal deterioration ratio calculating unit)  120  configured to calculate the current thermal deterioration ratio of the hydraulic oil after the vehicle starts operating by calculating the current thermal deterioration ratio of the hydraulic oil on basis of the temperature of the hydraulic oil detected by the fuel temperature sensor  18  and adding the calculated thermal deterioration ratio to a previously calculated thermal deterioration ratio, the thermal deterioration ratio adder unit  123  (the third thermal deterioration ratio calculating unit) configured to calculate the current thermal deterioration ratio of the hydraulic oil by summing the thermal deterioration ratio during stoppage of the vehicle calculated by the thermal deterioration ratio calculating unit  118  and the thermal deterioration ratio after the vehicle starts operating calculated by the deterioration ratio calculating unit  120 , the mechanical deterioration ratio calculating unit  122  configured to calculate the current mechanical deterioration ratio of the hydraulic oil and add the calculated mechanical deterioration ratio to a previously calculated mechanical deterioration ratio, and the ATF deterioration estimating unit (the deterioration ratio comparing unit)  124  configured to compare the current thermal deterioration ratio calculated by the thermal deterioration ratio adder unit  123  with the mechanical deterioration ratio calculated by the mechanical deterioration ratio calculating unit  122  and select a larger one of the current thermal deterioration ratio and the mechanical deterioration ratio as an estimated value of the deterioration ratio of the hydraulic oil. 
     According to the present disclosure, the hydraulic oil deterioration ratio estimating apparatus of a vehicle can calculate a current thermal deterioration ratio of the hydraulic oil by calculating the thermal deterioration ratio of the hydraulic oil during stoppage of the vehicle using the thermal deterioration ratio calculating unit  118  and adding the calculated thermal deterioration ratio to the thermal deterioration ratio after the vehicle starts operating calculated using the thermal deterioration ratio calculating unit  120 . That is, since the thermal environment during stoppage of the vehicle and the deterioration conditions caused by the high heat of the hydraulic oil after the vehicle has traveled can be estimated, a situation in which although deterioration of the hydraulic oil progresses in reality, the estimated value of the thermal deterioration does not appropriately rise can be prevented. Accordingly, the detection accuracy of the thermal deterioration ratio of the hydraulic oil can be increased, since a more appropriate thermal deterioration ratio of the hydraulic oil including the thermal deterioration ratio during stoppage of the vehicle can be calculated. 
     In addition, according to the above-described hydraulic oil deterioration ratio estimating apparatus of a vehicle, the IG-OFF-period thermal deterioration ratio calculating unit  118  calculates the thermal deterioration ratio of the hydraulic oil from the time the vehicle previously stops to the time the vehicle starts on the basis of an estimated value of a change in temperature of the hydraulic oil from the time the vehicle previously stops to the time the vehicle starts and the thermal deterioration ratio per unit time of the hydraulic oil. 
     According to such a configuration, a deterioration level of the hydraulic oil caused by the thermal environment during stoppage of the vehicle and the heat generated after the vehicle starts operating can be more accurately estimated. As a result, the thermal deterioration ratio during stoppage of the vehicle can be more accurately calculated. 
     In the preceding specification, the disclosure has been described with reference to a specific exemplary embodiment. It will, however, be evident that various modifications and changes may be made without departing from the broader spirit and scope of the disclosure and the technical aspect of the specification and drawings. 
     According to an aspect of the present disclosure, a hydraulic oil deterioration ratio estimating apparatus for use in a vehicle is provided. The apparatus includes a torque converter configured to transfer a drive force of an engine to an input shaft using hydraulic oil, an automatic transmission configured to change a rotation speed of the input shaft rotated by the drive force through hydraulic control using the hydraulic oil and output the rotation to an output shaft, an oil temperature detector configured to detect a temperature of the hydraulic oil, an engine speed detecting unit configured to detect an engine speed of the engine, an input shaft rotation speed detector configured to detect a rotation speed of the input shaft of the automatic transmission, an output shaft rotation speed detector configured to detect a rotation speed of the output shaft of the automatic transmission, and a hydraulic oil deterioration ratio estimating unit configured to estimate a deterioration ratio of the hydraulic oil. The hydraulic oil deterioration ratio estimating unit includes a first thermal deterioration ratio calculating unit configured to calculate a thermal deterioration ratio of the hydraulic oil during stoppage of the vehicle on the basis of an estimated value of a change in temperature of the hydraulic oil from stoppage of the vehicle to start of the vehicle, a second thermal deterioration ratio calculating unit configured to calculate the current thermal deterioration ratio of the hydraulic oil on the basis of the temperature of the hydraulic oil detected by the oil temperature detector, add the calculated thermal deterioration ratio to a previously calculated thermal deterioration ratio, and calculate the thermal deterioration ratio after the vehicle starts operating, a third thermal deterioration ratio calculating unit configured to calculate the current thermal deterioration ratio of the hydraulic oil by summing the thermal deterioration ratio during stoppage of the vehicle calculated by the first thermal deterioration ratio calculating unit and the thermal deterioration ratio after the vehicle starts operating calculated by the second thermal deterioration ratio calculating unit, a mechanical deterioration ratio calculating unit configured to calculate a shear rotation speed of the hydraulic oil from the engine speed detected by the engine speed detecting unit, the rotation speed of the input shaft detected by the input shaft rotation speed detector, and the rotation speed of the output shaft detected by the output shaft rotation speed detector, calculate the current mechanical deterioration ratio of the hydraulic oil on the basis of the calculated shear rotation speed, and add the mechanical deterioration ratio to a previously calculated mechanical deterioration ratio, and a deterioration ratio comparing unit configured to compare the current thermal deterioration ratio calculated by the third thermal deterioration ratio calculating unit with the mechanical deterioration ratio calculated by the mechanical deterioration ratio calculating unit and select a larger one of the current thermal deterioration ratio and the mechanical deterioration ratio as an estimated value of the deterioration ratio of the hydraulic oil. 
     According to the present disclosure, the hydraulic oil deterioration ratio estimating apparatus of a vehicle can calculate a current thermal deterioration ratio of the hydraulic oil by calculating the thermal deterioration ratio of the hydraulic oil during stoppage of the vehicle using the first thermal deterioration ratio calculating unit and adding the calculated thermal deterioration ratio to the thermal deterioration ratio after the vehicle starts operating calculated using the second thermal deterioration ratio calculating unit. That is, since the thermal environment during stoppage of the vehicle and the deterioration conditions caused by the high heat of the hydraulic oil after the vehicle has traveled can be estimated, a situation in which although deterioration of the hydraulic oil progresses in reality, the estimated value of the thermal deterioration does not appropriately rise can be prevented. Accordingly, the detection accuracy of the thermal deterioration ratio of the hydraulic oil can be increased, since a more appropriate thermal deterioration ratio of the hydraulic oil including the thermal deterioration ratio during stoppage of the vehicle can be calculated. 
     It is desirable that the first thermal deterioration ratio calculating unit calculate the thermal deterioration ratio of the hydraulic oil from a time the vehicle stops operating to a time the vehicle starts operating on the basis of an estimated value of a change in temperature of the hydraulic oil from a time the vehicle previously stops operating to a time the vehicle starts operating and a thermal deterioration ratio per unit time of the hydraulic oil. 
     According to such a configuration, a deterioration level of the hydraulic oil caused by the thermal environment during stoppage of the vehicle and the heat generated after the vehicle starts operating can be more accurately estimated. As a result, the thermal deterioration ratio during stoppage of the vehicle can be more accurately calculated. Note that the reference numerals in parentheses correspond to those of elements of an exemplary embodiment described below. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.