Patent Publication Number: US-2021174614-A1

Title: Vehicle control device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2019-221697 filed on Dec. 6, 2019, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a vehicle control device that performs learning of correcting a parameter used in a control program for controlling a vehicle. 
     2. Description of Related Art 
     There are known vehicle control devices that are configured to update a learned value stored in a storage unit and store the updated learned value, and that store an initial set value of the learned value in advance and, when part replacement information is input, rewrite the learned value relating to the replaced part to the initial set value. One example is the control device described in Japanese Patent Application Publication No. 2001-65399 (JP 2001-65399 A). 
     SUMMARY 
     In the vehicle control device described in JP 2001-65399 A, part replacement information is input manually. Therefore, if part replacement information fails to be input, the learned value relating to the replaced part will not be rewritten to the initial value, which may degrade the controllability of the vehicle after replacement of the part. 
     The present disclosure has been contrived under these circumstances, and an object thereof is to provide a vehicle control device that automatically determines that a part has been replaced and appropriately executes learning upon replacement of the part to quickly mitigate degradation of the controllability of the vehicle after replacement of the part. 
     The gist of a first disclosure is as follows: A vehicle control device that performs learning to correct a parameter used in a control program for controlling a vehicle, the vehicle control device including (a) a storage unit that stores learning data obtained by the learning, (b) a replacement determining unit that determines whether or not a part controlled by the parameter has been replaced, and (c) a rewriting executing unit that resets the learning data stored in the storage unit when the replacement determining unit determines that the part has been replaced, wherein the replacement determining unit determines that the part has been replaced based on an adjustment that is performed upon replacement of the part. 
     The gist of a second disclosure is as follows: The vehicle control device of the first disclosure, wherein the adjustment is an adjustment of a resolver provided in a rotating machine that transmits a travel driving force to the part. 
     The gist of a third disclosure is as follows: The vehicle control device of the first or second disclosure, wherein the replacement determining unit determines that the part has been replaced based on an update, resulting from the adjustment, in a replacement record of the part included in maintenance information. 
     The gist of a fourth disclosure is as follows: The vehicle control device of the third disclosure, wherein, after the replacement record is updated, the replacement determining unit determines only once that the part has been replaced. 
     The gist of a fifth disclosure is as follows: The vehicle control device of any one of the first to fourth disclosures, wherein (a) the part is a transmission, and (b) the parameter is an oil pressure command value for controlling switching of a gear stage of the transmission. 
     The gist of a sixth disclosure is as follows: The vehicle control device of any one of the first to fifth disclosures, further including an IG determining unit that determines whether or not an ignition signal has been switched from an OFF signal that stops a travel driving force source to an ON signal that starts the travel driving force source, wherein the replacement determining unit determines whether or not the part has been replaced when the IG determining unit determines that the ignition signal has been switched from the OFF signal to the ON signal. 
     The vehicle control device of the first disclosure includes (a) the storage unit that stores the learning data obtained by the learning, (b) the replacement determining unit that determines whether or not the part controlled by the parameter has been replaced, and (c) the rewriting executing unit that resets the learning data stored in the storage unit when the replacement determining unit determines that the part has been replaced. The replacement determining unit determines that the part has been replaced based on the adjustment that is performed upon replacement of the part. Thus, the determination as to replacement of the part is automatically made based on the adjustment that is performed upon replacement of the part. Since the determination as to replacement of the part is automatically made and the learning data is reset, learning is appropriately executed upon replacement of the part, so that degradation of the controllability of the vehicle after replacement of the part is quickly mitigated. 
     The vehicle control device of the second disclosure is the vehicle control device of the first disclosure, wherein the adjustment is an adjustment of the resolver provided in the rotating machine that transmits a travel driving force to the part. It is possible to infer that the rotating machine has been re-mounted and, by extension, to automatically determine that the part has been replaced, based on the adjustment of the resolver. 
     The vehicle control device of the third disclosure is the vehicle control device of the first or second disclosure, wherein the replacement determining unit determines that the part has been replaced based on an update, resulting from the adjustment, in the replacement record of the part included in maintenance information. Since the determination as to replacement of the part is automatically made based on an update in the replacement record and the learning data is reset, degradation of the controllability of the vehicle after replacement of the part is quickly mitigated. 
     The vehicle control device of the fourth disclosure is the vehicle control device of the third disclosure, wherein, after the replacement record is updated, the replacement determining unit determines only once that the part has been replaced. Since the part is determined to have been replaced only once after the replacement record of the part included in the maintenance information is updated, the learning data is reset only once upon replacement of the part and thus execution of unnecessary learning is avoided. 
     The vehicle control device of the fifth disclosure is the vehicle control device of any one of the first to fourth disclosures, wherein (a) the part is a transmission, and (b) the parameter is the oil pressure command value for controlling switching of the gear stage of the transmission. Thus, when it is determined that the transmission has been replaced, the learning data relating to the oil pressure command value stored in the learning data storage unit is reset. Therefore, learning is appropriately executed upon replacement of the transmission, so that aggravation of shift shock that occurs when the gear stage is switched after replacement of the transmission is quickly mitigated. 
     The vehicle control device of the sixth disclosure is the vehicle control device of any one of the first to fifth disclosures, further including the IG determining unit that determines whether or not the ignition signal has been switched from the OFF signal that stops the travel driving force source to the ON signal that starts the travel driving force source, wherein the replacement determining unit determines whether or not the part has been replaced when the IG determining unit determines that the ignition signal has been switched from the OFF signal to the ON signal. Since the learning data is reset when the ignition signal is switched from the OFF signal to the ON signal, a sense of discomfort that the driver feels can be reduced compared with when the learning data is reset while the vehicle is traveling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG. 1  is a schematic configuration diagram of a vehicle equipped with a driving device ECU according to an embodiment of the present disclosure, and is a functional block diagram showing a main part of control functions for various types of control in the vehicle; 
         FIG. 2  is a graph showing one example of, and a relationship between, a gear shifting chart that is used for gear shifting control of a stepped transmission section and a power source switching map that is used for controlling switching between engine-powered travel and motor-powered travel; 
         FIG. 3  is a hydraulic circuit diagram illustrating part of the configuration of a hydraulic control circuit that performs gear shifting control of the stepped transmission section; 
         FIG. 4  is an actuation table showing, alongside each other, combinations of hydraulic friction-engaging devices to be actuated that are used to establish the respective gear stages in the stepped transmission section and combinations of solenoid patterns in the respective gear stages; 
         FIG. 5  is a nomogram in which relationships among the rotation speeds of rotating elements in a power transmission device that are coupled to one another in a different state in a different gear stage can be represented by straight lines; 
         FIG. 6  is a sectional view illustrating the configuration of a linear solenoid valve provided in the hydraulic control circuit; 
         FIG. 7  is a graph showing an example of valve characteristics that represent a relationship between a driving current and an output pressure in the linear solenoid valve; 
         FIG. 8  is a time chart showing an example of an action of the linear solenoid valve during gear shifting of the stepped transmission section, and illustrating how a driving current to the linear solenoid valve changes during a transitional period of engagement of a predetermined hydraulic friction-engaging device to be engaged at the time of gear shifting; 
         FIG. 9  is an example of a time chart of on-road learning in the case of gear shifting of the stepped transmission section from a second-speed gear stage to a third-speed gear stage; 
         FIG. 10  is an example about a correction value for an oil pressure command value that has been learned with a throttle valve opening degree divided into predetermined ranges in the case of gear shifting of the stepped transmission section from the second-speed gear stage to the third-speed gear stage; 
         FIG. 11A  is a graph of a relationship between an exciting voltage and a torque voltage that are detected while a first rotating machine is rotating with zero output torque, and is a graph in a case where the resolver does not have an offset; 
         FIG. 11B  is a graphs of a relationship between an exciting voltage and a torque voltage that are detected while a first rotating machine is rotating with zero output torque, and is a graph in a case where the resolver has an offset; 
         FIG. 12  is an example of maintenance information that has been updated after replacement of the compound transmission; and 
         FIG. 13  is an example of a flowchart illustrating a main part of control operation of the driving device ECU shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present disclosure will be described in detail below with reference to the drawings. In the following embodiment, the drawings are simplified or modified as necessary and do not necessarily exactly represent the dimensional ratios, shapes, etc. of parts. 
       FIG. 1  is a schematic configuration diagram of a vehicle  10  equipped with a driving device ECU  100  according to the embodiment of the present disclosure, and is a functional block diagram showing a main part of control functions for various types of control in the vehicle  10 . 
     The vehicle  10  is a hybrid vehicle and includes an engine  12 , a first rotating machine MG 1 , a second rotating machine MG 2 , a power transmission device  14 , driving wheels  28 , the driving device ECU  100 , a first gateway ECU  150 , and a second gateway ECU  152 . 
     The engine  12  is a travel driving force source of the vehicle  10  and formed by an internal combustion engine, such as a gasoline engine or a diesel engine. An engine torque Te [Nm] output from the engine  12  is controlled as an engine control device  50  including an electronic throttle valve, fuel injection equipment, and an ignition system is controlled by the driving device ECU  100  to be described later. 
     The first rotating machine MG 1  and the second rotating machine MG 2  are, for example, rotating electrical machines that are so-called motor-generators having the functions of an electric motor (motor) and a power generator (generator). The first rotating machine MG 1  and the second rotating machine MG 2  can serve as travel driving force sources of the vehicle  10 . Each of the first rotating machine MG 1  and the second rotating machine MG 2  is connected to a battery  54  provided in the vehicle  10  through an inverter  52  provided in the vehicle  10 . As the inverter  52  is controlled by the driving device ECU  100  to be described later, an MG 1  torque Tg [Nm] output from the first rotating machine MG 1  and an MG 2  torque Tm [Nm] output from the second rotating machine MG 2  are controlled. As to torques output from the rotating machines, for example, in the case of positive rotation, a positive torque that is on an acceleration side is a power running torque and a negative torque that is on a deceleration side is a regenerative torque. When the MG 1  torque Tg and the MG 2  torque Tm output from the first rotating machine MG 1  and the second rotating machine MG 2 , respectively, are power running torques, power output from the first rotating machine MG 1  and the second rotating machine MG 2  is a travel driving force. (“Driving force” and “torque” are used synonymously with “power” when no particular distinction is made among these words.) The battery  54  gives and receives electricity to and from each of the first rotating machine MG 1  and the second rotating machine MG 2 . The battery  54  is a chargeable-dischargeable secondary battery, such as a lithium-ion battery pack or a nickel-metal hydride battery pack. The first rotating machine MG 1  and the second rotating machine MG 2  are provided inside a transaxle case  16  that is a non-rotating member mounted on a vehicle body. The engine  12 , the first rotating machine MG 1 , and the second rotating machine MG 2  correspond to the “travel driving force source” in the present disclosure, and the first rotating machine MG 1  and the second rotating machine MG 2  correspond to the “rotating machine” in the present disclosure. 
     The power transmission device  14  includes an electrical stepless transmission section  18 , a mechanical stepped transmission section  20 , and others that are disposed in series on a common central axis inside the transaxle case  16 . The stepless transmission section  18  is coupled to the engine  12  directly or indirectly through a damper or the like (not shown). The stepped transmission section  20  is coupled to an output side of the stepless transmission section  18 . The power transmission device  14  includes a differential gear  24  coupled to an output shaft  22  that is an output rotating member of the stepped transmission section  20 , and a pair of axles  26  coupled to the differential gear  24 . In the power transmission device  14 , power output from the engine  12  and the second rotating machine MG 2  is transmitted to the stepped transmission section  20 . The power transmitted to the stepped transmission section  20  is transmitted to the driving wheels  28  through the differential gear  24  etc. The power transmission device  14  thus configured is suitably used for front-engine, rear-wheel-drive (FR) vehicles. The stepless transmission section  18 , the stepped transmission section  20 , etc. are configured so as to be substantially symmetrical with respect to the common central axis, and lower halves of these sections from the central axis are omitted from  FIG. 1 . This common central axis is a central axis of a crankshaft of the engine  12 , a coupling shaft  34  coupled to the crankshaft, or the like. The stepless transmission section  18 , the stepped transmission section  20 , the differential gear  24 , and the pair of axles  26  in the power transmission device  14  constitute a power transmission path PT provided between the engine  12  and the driving wheels  28 . 
     The stepless transmission section  18  includes a differential mechanism  32  as a power split device that mechanically divides power from the engine  12  toward the first rotating machine MG 1  and an intermediate transmission member  30  that is an output rotating member of the stepless transmission section  18 . The first rotating machine MG 1  is a rotating machine to which power from the engine  12  is transmitted. The second rotating machine MG 2  is connected to the intermediate transmission member  30  so as to be able to transmit power thereto. The intermediate transmission member  30  is coupled to the driving wheels  28  through the stepped transmission section  20 , and therefore the second rotating machine MG 2  is a rotating machine that is connected to the power transmission path PT, as well as to the driving wheels  28 , so as to be able to transmit power thereto. 
     The differential mechanism  32  is a commonly known single-pinion planetary gear device including a sun gear S 0 , a carrier CA 0 , and a ring gear R 0 . 
     The stepped transmission section  20  is a mechanical transmission mechanism as a stepped transmission that constitutes a part of the power transmission path PT between the intermediate transmission member  30  and the driving wheels  28 , i.e., an automatic transmission that constitutes a part of the power transmission path PT between the differential mechanism  32  and the driving wheels  28 . The intermediate transmission member  30  functions also as an input rotating member of the stepped transmission section  20 . The stepped transmission section  20  is a commonly known planetary-gear automatic transmission including, for example, a plurality of planetary gear devices, namely a first planetary gear device  36  and a second planetary gear device  38 , and a plurality of engaging devices, namely a clutch C 1 , a clutch C 2 , a brake B 1 , a brake B 2 , and a one-way clutch F 1 . Hereinafter, the clutch C 1 , the clutch C 2 , the brake B 1 , and the brake B 2  will be referred to simply as hydraulic friction-engaging devices CB when no particular distinction is made among them. 
     The hydraulic friction-engaging device CB is a hydraulically operated friction-engaging device formed by, for example, a multi-disc or single-disc clutch or a brake that is pressed by a hydraulic actuator, or a band brake that is tightened by a hydraulic actuator. As a hydraulic control circuit  56  provided in the vehicle  10  is controlled by the driving device ECU  100  to be described later, the application state of each hydraulic friction-engaging device CB that is an engaged state, a released state, etc. is switched according to a regulated oil pressure output from the hydraulic control circuit  56 . 
     The first planetary gear device  36  is a commonly known single-pinion planetary gear device including a sun gear S 1 , a carrier CA 1 , and a ring gear R 1 . The second planetary gear device  38  is a commonly known single-pinion planetary gear device including a sun gear S 2 , a carrier CA 2 , and a ring gear R 2 . 
     The differential mechanism  32 , the first planetary gear device  36 , the second planetary gear device  38 , the hydraulic friction-engaging devices CB, the one-way clutch F 1 , the first rotating machine MG 1 , and the second rotating machine MG 2  are coupled to one another as shown in  FIG. 1 . 
     An engagement torque that is the torque capacity of each hydraulic friction-engaging device CB is changed by a regulated engaging oil pressure that is output from each of linear solenoid valves SL 1  to SL 4  etc. in the hydraulic control circuit  56  provided in the vehicle  10 . 
     In the stepped transmission section  20 , one of gear stages that are different from one another in gear ratio γat (=AT input rotation speed Nati [rpm]/AT output rotation speed Nato [rpm]) is established as the combination of the application states of more than one hydraulic friction-engaging device CB is switched. The AT input rotation speed Nati is an input rotation speed of the stepped transmission section  20  and has the same value as the rotation speed of the intermediate transmission member  30  and an MG 2  rotation speed Nm [rpm]. The AT output rotation speed Nato is the rotation speed of the output shaft  22  that is an output rotating member of the stepped transmission section  20 , and is also an output rotation speed No [rpm] of a compound transmission  40  that is the entire transmission combining the stepless transmission section  18  and the stepped transmission section  20 . The compound transmission  40  corresponds to the “transmission” and the “part” in the present disclosure. 
     In a completed state of the vehicle  10  (including, for example, a state where conversion or repair, i.e., replacement or repair, of the compound transmission  40  has been completed), the first rotating machine MG 1  and the second rotating machine MG 2  can be said to be integrally configured with the compound transmission  40 . The first rotating machine MG 1  and the second rotating machine MG 2  are configured to be able to transmit to the compound transmission  40  a travel driving force that each of them outputs. 
       FIG. 2  is a graph showing one example of, and a relationship between, a gear shifting chart that is used for gear shifting control of the stepped transmission section  20  and a power source switching map that is used for controlling switching between engine-powered travel and motor-powered travel. Engine-powered travel is a travel mode in which at least the engine  12  is used as a travel driving force source. Motor-powered travel is a travel mode in which the engine  12  is not used as a travel driving force source and the first rotating machine MG 1  or the second rotating machine MG 2  is used as a travel driving force source. As shown in  FIG. 2 , relationships (a gear shifting chart or a gear shifting map) represented by upshift lines (solid lines) and downshift lines (dashed lines), with a vehicle speed V [km/h] and a demanded driving force Frdem [N] as variables, are stored in advance. When a point specified by the actual vehicle speed V and demanded driving force Frdem that are variables crosses an upshift line (solid line) or a downshift line (dashed line), it is determined to start gear shifting control. Motor-powered travel is executed in a region indicated by the long dashed short dashed line where the engine efficiency is generally low, which is a low-vehicle-speed region where the vehicle speed V is relatively low or a low-load region where the demanded driving force Frdem is relatively low. Further, motor-powered travel is used when the state-of-charge (charge capacity) SOC [%] of the battery  54  connected to the second rotating machine MG 2  through the inverter  52  is not lower than a predetermined value. Establishing a gear stage of the stepped transmission section  20  based on this gear shifting chart can achieve favorable fuel efficiency of the vehicle  10 . 
       FIG. 3  is a hydraulic circuit diagram illustrating part of the configuration of the hydraulic control circuit  56  that performs gear shifting control of the stepped transmission section  20 . 
     The hydraulic control circuit  56  includes, as components for controlling the engagement torques of the hydraulic friction-engaging devices CB that are engaging elements provided in the stepped transmission section  20 , the linear solenoid valve SL 1 , the linear solenoid valve SL 2 , the linear solenoid valve SL 3 , the linear solenoid valve SL 4  (hereinafter referred to simply as “linear solenoid valves SL” when no particular distinction is made among them), a solenoid valve SC 1 , a solenoid valve SC 2  (hereinafter referred to simply as “solenoid valves SC” when no particular distinction is made between them), and a switching valve  58 . 
     The linear solenoid valve SL is an electromagnetic valve that, using a line pressure PL [Pa] regulated by, for example, a regulator valve (not shown) as an original pressure, outputs an oil pressure corresponding to an oil pressure control command signal Sat that is input from the driving device ECU  100  (see  FIG. 1 ), according to an electromagnetic force of a solenoid that is controlled based on the oil pressure control command signal Sat. 
     An oil pressure output from the linear solenoid valve SL 1  is supplied to a hydraulic actuator  62   a  that controls the application state of the clutch C 1 . An oil pressure output from the linear solenoid valve SL 2  is supplied to a hydraulic actuator  62   b  that controls the application state of the clutch C 2 . An oil pressure output from the linear solenoid valve SL 3  is supplied to a hydraulic actuator  62   c  that controls the application state of the brake B 1 . An oil pressure output from the linear solenoid valve SL 4  is supplied to a hydraulic actuator  62   d  that controls the application state of the brake B 2 . 
     Based on the oil pressure control command signal Sat input from the driving device ECU  100 , each solenoid valve SC switches between an ON state where the switching valve  58  outputs an oil pressure and an OFF state where the switching valve  58  does not output an oil pressure. The solenoid valves SC are preferably normally closed ON-OFF valves. 
     A state where an oil pressure is supplied from the solenoid valve SC 1  and the solenoid valve SC 2  will be referred to as an ON-state, and a state where no oil pressure is supplied from the solenoid valve SC 1  and the solenoid valve SC 2  will be referred to as an OFF state. The switching valve  58  is provided with a spring  60  that urges a spool valve element in the switching valve  58 . When the solenoid valve SC 1  is in the OFF state and the solenoid valve SC 2  is in the OFF state, the switching valve  58  is kept in the OFF state as the spool valve element in the switching valve  58  is urged by an urging force of the spring  60 . When the solenoid valve SC 1  is in the ON state and the solenoid valve SC 2  is in the OFF state, the switching valve  58  is kept in the ON state as the spool valve element in the switching valve  58  is moved against the urging force of the spring  60 . When the solenoid valve SC 1  is in the ON state and the solenoid valve SC 2  is in the ON state, the switching valve  58  is kept in the OFF state as the spool valve element in the switching valve  58  is urged by the urging force of the spring  60 . 
     Thus, in the hydraulic control circuit  56  shown in  FIG. 3 , when the solenoid valve SC 1  is in the ON state and the solenoid valve SC 2  is in the OFF state, a supply source of the line pressure PL and an oil passage  64  between the linear solenoid valve SL 2  and the linear solenoid valve SL 3  communicate with each other. When both the solenoid valve SC 1  and the solenoid valve SC 2  are in the OFF state, or when both the solenoid valve SC 1  and the solenoid valve SC 2  are in the ON state, communication between the supply source of the line pressure PL (original pressure) and the oil passage  64  is interrupted while a drain port EX in the switching valve  58  and the oil passage  64  communicate with each other. 
       FIG. 4  is an actuation table showing, alongside each other, combinations of the hydraulic friction-engaging devices CB to be actuated (combinations of the application states thereof) that are used to establish the respective gear stages in the stepped transmission section  20  and combinations of solenoid patterns in the respective gear stages. For the hydraulic friction-engaging devices shown in  FIG. 4 , circles represent an engaged state and blank cells represent a released state. For the solenoid patterns shown in  FIG. 4 , circles represent a state where an oil pressure is output and blank cells represent a state where no oil pressure is output. 
     In  FIG. 4 , “P,” “Rev,” “N,” and “D” represent a parking range, a reverse range, a neutral range, and a drive range, respectively, one of which is selected by manual operation of a shift lever. The parking range and the neutral range are no-travel ranges that are selected not to cause the vehicle  10  to travel. The reverse range is a travel range that is selected to cause the vehicle  10  to travel backward. The drive range is a travel range that is selected to cause the vehicle  10  to travel forward. As the linear solenoid valves SL and the solenoid valves SC are controlled in accordance with the solenoid patterns shown in  FIG. 4 , the combination of the application states of the hydraulic friction-engaging devices CB is controlled. The range of the power transmission device  14  is switched and the gear stage established in the stepped transmission section  20  is switched, i.e., gears are shifted, according to the combination of the application states of the hydraulic friction-engaging devices CB. 
       FIG. 5  is a nomogram in which relationships among the rotation speeds of rotating elements in the power transmission device  14  that are coupled to one another in a different state in a different gear stage can be represented by straight lines. The nomogram shown in  FIG. 5  is represented by two-dimensional coordinates, with the axis of abscissas showing relationships among gear ratios ρ of the differential mechanism  32 , the first planetary gear device  36 , and the second planetary gear device  38  and the axis of ordinates showing relative rotation speeds. The horizontal line X 1  indicates zero rotation speed, and the horizontal line XG indicates the rotation speed of the intermediate transmission member  30 . 
     The three vertical lines Y 1 , Y 2 , Y 3  indicate, from the left side, the relative rotation speeds of the sun gear S 0 , the carrier CA 0 , and the ring gear R 0 , respectively, and the intervals of the three vertical lines Y 1  to Y 3  are determined according to the gear ratio of the differential mechanism  32 . The four vertical lines Y 4 , Y 5 , Y 6 , Y 7  indicate, from the right side, the relative rotation speeds of the sun gear  51 , the carrier CA 1  and the ring gear R 2 , the ring gear R 1  and the carrier CA 2 , and the sun gear S 2 , respectively, and the intervals of the four vertical lines Y 4  to Y 7  are determined according to the gear ratios of the first planetary gear device  36  and the second planetary gear device  38 . 
     As shown in  FIG. 5 , in the stepped transmission section  20 , when the clutch C 1  and the brake B 2  (one-way clutch F 1 ) are engaged, the rotation speed of the output shaft  22  in a first-speed gear stage (1st) is indicated by the point of intersection between the oblique straight line L 1  that passes through the point of intersection between the vertical line Y 7  and the horizontal line XG and the point of intersection between the vertical line Y 5  and the horizontal line X 1 , and the vertical line Y 6  that indicates the rotation speed of a rotating element coupled to the output shaft  22 . The rotation speed of the output shaft  22  in a second-speed gear stage (2nd) is indicated by a point determined when the clutch C 1  and the brake B 1  are engaged, which is the point of intersection between the oblique straight line L 2  and the vertical line Y 6  indicating the rotation speed of the rotating element coupled to the output shaft  22 . The rotation speed of the output shaft  22  in a third-speed gear stage (3rd) is indicated by a point determined when the clutch C 1  and the clutch C 2  are engaged, which is the point of intersection between the horizontal straight line L 3  and the vertical line Y 6  indicating the rotation speed of the rotating element coupled to the output shaft  22 . The rotation speed of the output shaft  22  in a fourth-speed gear stage (4th) is indicated by a point determined when the clutch C 2  and the brake B 1  are engaged, which is the point of intersection between the oblique straight line L 4  and the vertical line Y 6  indicating the rotation speed of the rotating element coupled to the output shaft  22 . 
     As described above, the gear stage established in the stepped transmission section  20  is switched as the combination of the hydraulic friction-engaging devices CB to be engaged is changed. 
     As shown in  FIG. 1 , the vehicle  10  includes the driving device ECU  100 . The driving device ECU  100  includes a so-called microcomputer having, for example, a CPU, RAM, ROM, input-output interface, and others. The CPU controls driving devices of the vehicle  10  including the engine  12 , the first rotating machine MG 1 , the second rotating machine MG 2 , and the power transmission device  14  by performing signal processing in accordance with a program that is stored in the ROM in advance using a temporary storage function of the RAM. The driving device ECU  100  corresponds to the “control device” in the present disclosure. 
     Input into the driving device ECU  100  are various signals etc. (e.g., the engine speed Ne [rpm]; the output rotation speed No that is the rotation speed of the output shaft  22 ; an MG 1  rotation speed Ng [rpm] that is the rotation speed of the first rotating machine MG 1 ; the MG 2  rotation speed Nm [rpm] that is the rotation speed of the second rotating machine MG 2 ; an accelerator operation amount θacc [%] that is an operation amount of an accelerator pedal representing the extent of acceleration operation by a driver; a throttle valve opening degree θth [%]; a battery temperature THbat [° C.], a battery charge-discharge current that [A], and a battery voltage Vbat [V] of the battery  54 ; a hydraulic fluid temperature THoil [° C.] inside the hydraulic control circuit  56 ; and the ignition signal IG that is a signal indicating whether to start or stop the travel driving force source) based on detection values of various sensors etc. (e.g., rotation speed sensors  70 ,  72 , resolvers  74 ,  76 , an accelerator operation amount sensor  78 , a throttle valve opening degree sensor  80 , a battery sensor  90 , an oil temperature sensor  92 , and an ignition switch  94  that is a switch for starting the travel driving force source) provided in the vehicle  10 . 
     From the driving device ECU  100 , various command signals (e.g., an engine control command signal Se that is a command signal for controlling the engine  12 , a rotating machine control command signal Smg that is a command signal for controlling each of the first rotating machine MG 1  and the second rotating machine MG 2 , and the oil pressure control command signal Sat that is a command signal for controlling the application state of each hydraulic friction-engaging device CB) are output to the devices (e.g., the engine control device  50 , the inverter  52 , and the hydraulic control circuit  56 ) provided in the vehicle  10 . 
     The driving device ECU  100  functionally includes a program storage unit  100   a , a driving control unit  100   b , a learning unit  100   c , a learning data storage unit  100   d , and an offset storage unit  100   e.    
     The program storage unit  100   a  stores control programs for controlling the driving devices. 
     The driving control unit  100   b  executes operation control of the engine  12 , the first rotating machine MG 1 , and the second rotating machine MG 2 , and executes gear shifting control of switching the gear stage of the stepped transmission section  20  of the power transmission device  14 , in accordance with the control programs stored in the program storage unit  100   a.    
     The learning unit  100   c  learns a correction value for correcting the value of a parameter used in a control program. The learned correction value is stored in the learning data storage unit  100   d . The learning data storage unit  100   d  is formed by, for example, a non-volatile memory. In the driving control unit  100   b , the value of the parameter that is the object of learning is corrected by the learned correction value, and a corrected learned value LRN is used in the control program as the parameter. The learning data storage unit  100   d  corresponds to the “storage unit” in the present disclosure. 
     In the following, learning of a driving current IDR [A] for the linear solenoid valve SL that controls switching of the gear stage of the stepped transmission section  20  will be described as a specific example of learning of a parameter used in a control program. 
       FIG. 6  is a sectional view illustrating the configuration of the linear solenoid valve SL provided in the hydraulic control circuit  56 . The linear solenoid valves SL 1  to SL 4  provided in the hydraulic control circuit  56  have basically the same configuration; in  FIG. 6 , therefore, the linear solenoid valve SL 1  is illustrated as a representative. The linear solenoid valve SL 1  is composed of a solenoid  114  that is a device to which a current is applied and which then converts electric energy into a driving force, and a pressure regulating part  116  that is driven by the solenoid  114  to regulate the line pressure PL that is an input pressure and thereby generate a predetermined output pressure PSL [Pa]. 
     The solenoid  114  includes a winding core  118 , a solenoid coil  120 , a core  122 , a plunger  124 , a case  126 , and a cover  128 . The winding core  118  has a cylindrical shape. The solenoid coil  120  is lead wire wound on an outer circumference of the winding core  118 . The core  122  can move inside the winding core  118  in the direction of a central axis. The plunger  124  is fixedly provided at an end portion of the core  122  on the opposite side from the pressure regulating part  116 . The case  126  houses the winding core  118 , the solenoid coil  120 , the core  122 , and the plunger  124 . The cover  128  is fitted in an opening of the case  126 . 
     The pressure regulating part  116  has a sleeve  130 , a spool valve element  132 , and a spring  134 . The sleeve  130  is fitted in the case  126 . The spool valve element  132  is provided so as to be able to move inside the sleeve  130  in the direction of a central axis. The spring  134  urges the spool valve element  132  toward the solenoid  114 . An end portion of the spool valve element  132  on the side of the solenoid  114  butts against an end portion of the core  122  on the side of the pressure regulating part  116 . 
     In the linear solenoid valve SL 1  thus configured, when a driving current IDR is applied to the solenoid coil  120 , the plunger  124  is moved according to the current value in the direction of a central axis that is common to the core  122  and the spool valve element  132 . As the plunger  124  is moved, the core  122  and also the spool valve element  132  are moved in the same direction. Thus, the flow rate of a hydraulic fluid input through an input port  136  and the flow rate of a hydraulic fluid discharged through a drain port  138  are adjusted. For example, based on the valve characteristics representing a relationship between the driving current IDR and the output pressure PSL shown in  FIG. 7 , the line pressure PL (original pressure) input through the input port  136  is regulated to a predetermined output pressure PSL corresponding to the driving current IDR and output through an output port  140 . 
       FIG. 8  is a time chart showing an example of an action of the linear solenoid valve SL at the time of gear shifting of the stepped transmission section  20 , and illustrating how the driving current IDR to the linear solenoid valve SL changes during a transitional period of engagement of a predetermined hydraulic friction-engaging device CB to be engaged at the time of gear shifting. Since the output pressure PSL of the linear solenoid valve SL is determined when the driving current IDR is specified as shown in  FIG. 7 , the driving current IDR can serve as an oil pressure command value for the output pressure PSL. 
     In the period from time t 1  to time t 2  (quick charge period), the driving current IDR is temporarily increased for pack closing of closing a pack clearance. In the period from time t 2  to time t 3  (a period of constant standby pressure), the driving current IDR is maintained at a level corresponding to a constant standby pressure that is a state shortly before engagement. In the period from time t 3  to time t 4  (sweep period), the driving current IDR is gradually raised to gradually increase the engagement torque. At time t 4  when it is determined that synchronization has been achieved, the driving current IDR is increased to a maximum value. The relationship between the driving current IDR and time t [ms] during the transitional period of engagement as shown in the time chart of  FIG. 8  is a parameter used in a control program for gear shifting control. 
     The linear solenoid valves SL vary in valve characteristics, and the hydraulic friction-engaging devices CB vary in engagement characteristics. To reduce these variations in characteristics among the linear solenoid valves SL and the hydraulic friction-engaging devices CB, learning of correcting the driving current IDR to the linear solenoid valve SL is performed. For example, the driving current value IDRx [A] shown in  FIG. 8  corresponding to the constant standby pressure of the hydraulic friction-engaging device CB to be engaged is used as a parameter that is the object of learning. The driving current value IDRx corresponding to the constant standby pressure of the hydraulic friction-engaging device CB to be engaged corresponds to the “oil pressure command value” in the present disclosure. 
     This learning consists of in-factory learning that is executed in the factory, with the engine  12  operating, before shipment of the vehicle  10  or delivery of the vehicle  10  of which the compound transmission  40  has been replaced or repaired, and on-road learning that is executed after the vehicle  10  is shipped from the factory or the vehicle  10  of which the compound transmission  40  has been replaced or repaired is delivered, while the vehicle  10  is traveling. 
     In-factory learning is learning that involves outputting a standard value STN [A] as the driving current value IDRx to the linear solenoid valve SL and measuring the resulting shift shock, and then correcting the standard value STN so as to reduce the shift shock. This shift shock is attributable to tie-up of the stepped transmission section  20 , a flare (racing) of the engine speed Ne, etc. For example, a flare amount (racing amount) Neblow [rpm] (see  FIG. 9 ) that is an amount of flare of the engine speed Ne is detected as an amount of temporary rise in the engine speed Ne during a transitional period of gear shifting. By this in-factory learning, the driving current value IDRx is corrected from the standard value STN to a value obtained by adding an in-factory correction value to the standard value STN. The value obtained by adding the in-factory correction value to the standard value STN is stored in the learning data storage unit  100   d  as a pre-learning set value SET [A] that is a value before on-road learning. 
     When gear shifting is executed while the vehicle  10  is traveling, on-road learning is executed, based on the actual control result, about the driving current value IDRx for which the pre-learning set value SET is output to one of the linear solenoid valves SL 1  to SL 4  that is involved in gear shifting, i.e., that corresponds to the friction-engaging element to be released or engaged to shift gears. Specifically, for example, whether or not a flare has occurred during gear shifting that has been executed is detected, and the driving current value IDRx for the linear solenoid valves SL is corrected so as to bring the detected flare amount closer to a predetermined target value. The flare amount and the predetermined target value will be described later. 
     In on-road learning, the amount of correction is calculated in each learning session, and learning of correcting the driving current value IDRx by the calculated correction amount is repeated each time gear shifting is executed while the vehicle  10  is traveling. By using a correction value CMP [A] that is a total value of the amounts of correction of the respective learning sessions in the case of repeated learning by on-road learning, the driving current value IDRx is corrected from the pre-learning set value SET to the learned value LRN [A] that is obtained by adding the correction value CMP to the pre-learning set value SET. The correction value CMP learned by on-road learning is stored in the learning data storage unit  100   d . At the beginning of on-road learning, the correction value CMP is a zero value. On-road learning corresponds to “learning” in the present disclosure, and the correction value CMP corresponds to the “learning data” in the present disclosure. The learning data is stored as data showing the result of on-road learning. 
       FIG. 9  is one example of a time chart of on-road learning in the case of gear shifting of the stepped transmission section  20  from the second-speed gear stage to the third-speed gear stage. In  FIG. 9 , a state where no flare has occurred is indicated by a solid line, and a state where a flare has occurred is indicated by a dashed line. In  FIG. 9 , the axis of abscissas shows time t [ms] and the axis of ordinates shows, from the top, the engine speed Ne, the MG 1  rotation speed Ng, the MG 1  torque Tg, the MG 2  rotation speed Nm, the MG 2  torque Tm, a C 2  oil pressure Pc 2  [Pa] that is an oil pressure supplied to the hydraulic actuator  62   b  that controls the application state of the clutch C 2 , a B 1  oil pressure Pb 1  [Pa] that is an oil pressure supplied to the hydraulic actuator  62   c  that controls the application state of the brake B 1 , a Pc 2  driving current IDRc 2  [A] that is an oil pressure command value for the C 2  oil pressure Pc 2 , and a Pb 1  driving current IDRb 1  [A] that is an oil pressure command value for the B 1  oil pressure Pb 1 . The object of learning is the driving current value IDRx corresponding to the constant standby pressure at the Pc 2  driving current IDRc 2  of the C 2  oil pressure Pc 2  supplied to the hydraulic actuator  62   b  that controls the application state of the clutch C 2  that is the hydraulic friction-engaging device to be engaged. 
     At time t 1 , execution of clutch-to-clutch shifting is started. In the period from time t 1  to time t 4 , the Pc 2  driving current IDRc 2  to the hydraulic actuator  62   b  that controls the application state of the clutch C 2  being the hydraulic friction-engaging device to be engaged is changed from a low state to a high state in accordance with the above-described time chart shown in  FIG. 8 . Meanwhile, during the period from time t 1  to time t 4 , the Pb 1  driving current IDRb 1  to the hydraulic actuator  62   c  that controls the application state of the brake B 1  being the hydraulic friction-engaging device to be released is gradually changed from a high state to a low state. On-road learning is executed such that at time tx (t 1 &lt;tx&lt;t 4 ) during this clutch-to-clutch shifting (i.e., during control of switching of the gear stage of the stepped transmission section  20 ), the flare amount Neblow that is the amount of flare of the engine speed Ne is within a predetermined target range including predetermined target values Blowtgt [rpm]. The predetermined target range for the flare amount Neblow is a range that is set in advance through experiment or design so as to realize execution of such clutch-to-clutch shifting that shift shock and shift time are within allowable ranges. 
     Specifically, when the flare amount Neblow is larger than a target upper limit value Blowtgt 2  [rpm] of the predetermined target range, it is inferred that there is a period in which neither of the brake B 1  and the clutch C 2  has a transmission torque due to a time lag between a releasing action of the brake B 1  and an engaging action of the clutch C 2 . In this case, shift shock or prolongation of shift time may occur. In the next gear shifting, therefore, the driving current value IDRx is increased by the correction amount of one learning session from the value before the current session of learning by on-road learning such that the time lag between the releasing action of the brake B 1  and the engaging action of the clutch C 2  is eliminated or reduced. Thus, in the next gear shifting, the driving current value IDRx is increased from the current driving current value IDRx by the correction amount of one learning session. 
     Conversely, when the flare amount Neblow is smaller than a target lower limit value Blowtgt 1  [rpm] of the predetermined target range, tie-up of both the brake B 1  and the clutch C 2  having a transmission torque occurs as the releasing action of the brake B 1  and the engaging action of the clutch C 2  coincide with each other, which may result in shift shock. In the next gear shifting, therefore, the driving current value IDRx is reduced by the correction amount of one learning session from the value before the current session of learning by on-road learning such that the tie-up is eliminated or mitigated. Thus, in the next gear shifting, the driving current value IDRx is reduced from the current driving current value IDRx by the correction amount of one learning session. 
     When the flare amount Neblow is within the predetermined target range, this means that execution of such clutch-to-clutch shifting that shift shock and shift time are within the allowable ranges is already realized, and therefore the driving current value IDRx is not corrected, i.e., not changed. Thus, the driving current value IDRx for the next gear shifting is set to the same value as that of the current gear shifting. 
     On-road learning is executed in the entire travel range, i.e., the entire range of the throttle valve opening degree θth (or the accelerator operation amount θacc), and is executed, for example, with the throttle valve opening degree θth (or the accelerator operation amount θacc) being divided into predetermined ranges. For each predetermined range, the correction value CMP that is a total value of the amounts of correction obtained by repeated learning is learned. 
       FIG. 10  is an example of the correction value CMP for the Pc 2  driving current value IDRc 2  that has been learned with the throttle valve opening degree θth divided into predetermined ranges in the case of gear shifting of the stepped transmission section  20  from the second-speed gear stage to the third-speed gear stage. As shown in  FIG. 10 , for example, the throttle valve opening degree θth is divided into four predetermined ranges: a range of 0 [%] or larger but smaller than 25 [%]; a range of 25 [%] or larger but smaller than 50 [%]; a range of 50 [%] or larger but smaller than 75 [%]; and a range of 75 [%] or larger but smaller than 100 [%]. For the driving current value IDRx corresponding to each of these four divided predetermined ranges, the correction value CMP is learned as a value ΔPc 2 - 1 , a value ΔPc 2 - 2 , a value ΔPc 2 - 3 , or a value ΔPc 2 - 4  by on-road learning. The driving current value IDRx that is the parameter used in the control program is corrected by each of the correction values CMP (the value ΔPc 2 - 1 , the value ΔPc 2 - 2 , the value ΔPc 2 - 3 , and the value ΔPc 2 - 4 ) learned by on-road learning for the respective predetermined ranges. Not only when gears are shifted from the second-speed gear stage to the third-speed gear stage in the stepped transmission section  20  but also when gears are shifted between a different pair of gear stages, the driving current value IDRx corresponding to the constant standby pressure of the hydraulic friction-engaging device CB to be engaged serves as a parameter that is the object of learning for each predetermined range of the throttle valve opening degree θth. Thus, there is a plurality of parameters that serves as objects of learning, and the correction value CMP is learned for each of these parameters. 
     Like the driving device ECU  100 , each of the first gateway ECU  150  and the second gateway ECU  152  shown in  FIG. 1  includes a so-called microcomputer having, for example, a CPU, RAM, ROM, input-output interface, and others. Maintenance information to be described later is sent to the driving device ECU  100  by either the first gateway ECU  150  or the second gateway ECU  152 . The first gateway ECU  150  can communicate wirelessly with a server  160  and executes control of receiving maintenance information from the server  160  and sending the maintenance information to the driving device ECU  100 . The second gateway ECU  152  can connect to the server  160  through a connector  170  and executes control of receiving maintenance information from the server  160  and sending the maintenance information to the driving device ECU  100 . The server  160  is, for example, a computer including a program for providing maintenance information to the vehicle  10 , a CPU that executes the program, and a maintenance storage unit  160   a  that is a storage device for storing maintenance information. 
     As the first rotating machine MG 1  and the second rotating machine MG 2 , for example, synchronous motors (that function also as power generators as described above) are used because of good controllability of their rotation speed when acting as travel driving force sources. These synchronous motors are, for example, magnet-embedded synchronous motors having a structure in which permanent magnets are disposed (embedded) inside a rotor. The rotor, magnetized by the permanent magnets, is attracted to and repelled from a rotating magnetic field generated by a stator and thereby rotated. In a synchronous motor, the rotor is driven to rotate as a rotating magnetic field according to the rotation position (angular position) of the rotor is generated. Therefore, if the rotation position of the rotor in a synchronous motor is not correctly detected, the synchronous motor will not be correctly driven. The first rotating machine MG 1  and the second rotating machine MG 2  are provided with the resolvers  74 ,  76 , respectively, to correctly detect the rotation positions of the rotors. 
     The resolver  74  generally includes a resolver rotor that rotates in conjunction with the rotor of the first rotating machine MG 1 , i.e., rotates integrally with the rotor while being unable to rotate relatively thereto, and is configured to detect the rotation position of the rotor of the first rotating machine MG 1  by detecting the rotation position (angular position) of the resolver rotor. However, due to an error in the mounting position of the resolver  74  etc., an amount of difference (offset amount θoff [rad]) may occur between the rotation position of the rotor of the first rotating machine MG 1  detected by the resolver  74  and the actual rotation position of the rotor of the first rotating machine MG 1 . Hereinafter, a case where the offset amount θoff is not zero will be referred to as “there is an offset” and a case where the offset amount θoff is zero will be referred to as “there is no offset.” 
     If an “offset adjustment” to be described later is not performed in the state where there is an offset, it will be difficult to correctly drive the first rotating machine MG 1 . Therefore, it is necessary to perform the offset adjustment of the resolver  74  when mounting the first rotating machine MG 1  and the resolver  74  after installing the compound transmission  40  in the vehicle  10  (e.g., replacing or repairing the compound transmission  40 ). The “offset adjustment” is an adjustment that involves detecting the offset amount θoff of the resolver  74  provided in the first rotating machine MG 1 , and correcting the rotation position of the rotor of the first rotating machine MG 1  detected by the resolver  74  according to the detected offset amount θoff so as to correctly represent the actual rotation position of the rotor of the first rotating machine MG 1 . Also for the resolver  76  provided in the second rotating machine MG 2 , as with the resolver  74 , it is necessary to perform the offset adjustment of the resolver  76  when mounting the second rotating machine MG 2  and the resolver  76  after installing the compound transmission  40 . Thus, the offset adjustment of the resolvers  74 ,  76  is performed upon replacement of the compound transmission  40 . The offset adjustment performed on the resolvers  74 ,  76  corresponds to the “adjustment” in the present disclosure. The “adjustment” in the present disclosure refers to an adjustment that is performed upon replacement of a “part” of the vehicle  10 , such as the compound transmission  40 , such that that part or constituent members relating to that part work appropriately. 
     In the following, the offset adjustment of the resolver  74  will be described. The offset adjustment of the resolver  76  is the same and therefore will not be described here. 
       FIG. 11A  and  FIG. 11B  are graphs of a relationship between an exciting voltage Vd [V] and a torque voltage Vq [V] that are detected while the first rotating machine MG 1  is rotating with zero output torque, illustrating a difference between when the resolver  74  has an offset and when it does not have an offset.  FIG. 11A  is a graph in a case where the resolver does not have an offset.  FIG. 11B  is a graph in a case where the resolver has an offset. The axis of abscissas and the axis of ordinates shown in  FIG. 11A  and  FIG. 11B  are a d-axis (exciting voltage Vd) and a q-axis (torque voltage Vq) in so-called vector control. 
     Detection of the offset amount θoff of the resolver  74  is performed, for example, while the first rotating machine MG 1  is rotating with zero output torque. When the resolver  74  does not have an offset in this state, both an exciting current Id [A] that is a current for generating a rotating magnetic field and a torque current Iq [A] that is a current for generating an output torque become zero in a dq-axis coordinate system. Therefore, when the first rotating machine MG 1  is rotating with zero output torque, exciting voltage Vd=0 and torque voltage Vq=ωφ as shown in the following Formulae (3) and (4) are derived from the voltage equations shown in the following Formulae (1) and (2). The symbols ω [rad/s], ϕ [Wb], R [Ω], Ld [H], and Lq [H] denote the angular speed of the rotor, a predetermined magnetic flux according to a stator interlinkage magnetic flux of the permanent magnets embedded in the rotor, the resistance of the windings wound around the stator, a d-axis inductance, and a q-axis inductance, respectively. 
         Vd=−ω·Lq·Iq+R·Id   (1)
 
         Vq=ω·Ld·Id+ωϕ+R·Iq   (2)
 
         Vd= 0  (3)
 
         Vq=ωϕ   (4)
 
     The states expressed by Formulae (3) and (4) can be represented in a dq-axis coordinate system as in  FIG. 11A . However, if the resolver  74  has an offset, recognition axes for control are shifted as indicated by dashed lines in  FIG. 11B , so that the exciting voltage Vd (a d-axis component Vd′) which is supposed to be zero is detected. The offset amount θoff of the resolver  74  is detected based on the exciting voltage Vd thus detected. The detected offset amount θoff of the resolver  74  is stored in the offset storage unit  100   e  along with update information indicating that the offset amount θoff has been updated, such as the date of detection or a revision number (version). After the offset amount θoff of the resolver  74  is detected, the rotation position of the rotor of the first rotating machine MG 1  detected by the resolver  74  is corrected by the offset amount θoff stored in the offset storage unit  100   e , so that the actual rotation position of the rotor of the first rotating machine MG 1  is correctly recognized and the first rotating machine MG 1  is correctly driven. Thus, the offset adjustment is performed that involves detecting the offset amount θoff of the resolver  74 , and correcting the rotation position of the rotor of the first rotating machine MG 1  detected by the resolver  74  according to the detected offset amount θoff so as to correctly represent the actual rotation position of the rotor of the first rotating machine MG 1 . 
       FIG. 12  is an example of maintenance information that has been updated after replacement the compound transmission  40  of the vehicle  10 . The maintenance information on the vehicle  10  is stored as electronic data in the maintenance storage unit  160   a  that is a storage device inside the server  160 . 
     As shown in  FIG. 12 , in the maintenance information, information relating to maintenance of the vehicle  10  is recorded as the vehicle&#39;s history along with general items about the vehicle  10 , such as the name of the vehicle, the vehicle body number, the name of the dealer, and the name of inspection. In the vehicle&#39;s history, information relating to purchase of the vehicle  10  and replacement of the compound transmission  40  since the purchase of the vehicle  10  (replacement record) is recorded with the date of purchase and the date of replacement, respectively. 
     In the following, a case where maintenance information is sent from the first gateway ECU  150  to the driving device ECU  100  will be described as an example. 
     As shown in  FIG. 1 , the driving device ECU  100  functionally includes an IG determining unit  100   f , a sending-receiving unit  100   g , a replacement determining unit  100   h , and a rewriting executing unit  100   i . The first gateway ECU  150  functionally includes a wireless communication unit  150   a  and a sending-receiving unit  150   b . The driving device ECU  100  corresponds to the “control device” in the present disclosure. 
     The IG determining unit  100   f  determines whether or not the ignition signal IG has been switched from an OFF signal to an ON signal. When the ignition switch  94  is turned off, the ignition signal IG becomes the OFF signal that stops the travel driving force sources, so that the engine  12 , the first rotating machine MG 1 , and the second rotating machine MG 2  that are travel driving force sources are stopped. When the ignition switch  94  is turned on, the ignition signal IG becomes the ON signal that starts the travel driving force sources, so that the engine  12 , the first rotating machine MG 1 , and the second rotating machine MG 2  that are travel driving force sources are put in a state of being able to output a travel driving force. 
     The replacement determining unit  100   h  determines whether or not the offset adjustment has been performed on at least either of the resolvers  74 ,  76  provided in the compound transmission  40  controlled by the parameter that is the object of learning. The offset adjustment is determined to have been performed, for example, when either of the following conditions is met: (a) the value of the offset amount θoff of at least either of the resolvers  74 ,  76  has been changed based on the offset adjustment; and (b) the date of detection or the revision number in the aforementioned update information has been updated based on the offset adjustment of at least either of the resolvers  74 ,  76 . Thus, the offset adjustment is determined to have been performed when at least one offset amount θoff has been changed based on the offset adjustment of the resolvers  74 ,  76 . 
     When the IG determining unit  100   f  determines that the ignition signal IG has been switched from the OFF signal to the ON signal, the sending-receiving unit  100   g  sends to the sending-receiving unit  150   b  a switching signal indicating that the ignition signal IG has been switched from the OFF signal to the ON signal. 
     When the switching signal is received by the sending-receiving unit  150   b , the wireless communication unit  150   a  acquires the maintenance information on the vehicle  10  from the maintenance storage unit  160   a  of the server  160 . The sending-receiving unit  150   b  sends to the sending-receiving unit  100   g  the maintenance information acquired by the wireless communication unit  150   a.    
     When the maintenance information is received by the sending-receiving unit  100   g , the replacement determining unit  100   h  determines whether or not the replacement record of the compound transmission  40  included in the maintenance information has been updated. For example, when the date of replacement in the replacement record of the compound transmission  40  recorded in the vehicle&#39;s history included in the maintenance information is updated (including a case where a new date of replacement is added to the replacement record), after the update, it is determined only once that the replacement record has been updated. The replacement determining unit  100   h  determines that the replacement record has been updated, preferably only once when determining for the first time whether or not the replacement record has been updated after the update of the replacement record. 
     When either of the conditions that the offset adjustment is determined to have been performed on at least either of the resolvers  74 ,  76  and that the replacement record of the compound transmission  40  is determined to have been updated is met, the replacement determining unit  100   h  determines that the compound transmission  40  that is integrally configured with the first rotating machine MG 1  and the second rotating machine MG 2  provided with the resolvers  74 ,  76  has been replaced. When the offset adjustment is determined not to have been performed on either of the resolvers  74 ,  76  and the replacement record of the compound transmission  40  is determined not to have been updated, the replacement determining unit  100   h  determines that the compound transmission  40  has not been replaced. 
     When the replacement determining unit  100   h  determines that the compound transmission  40  has been replaced, the rewriting executing unit  100   i  resets the correction value CMP stored in the learning data storage unit  100   d . When the replacement determining unit  100   h  determines that the compound transmission  40  has not been replaced, the rewriting executing unit  100   i  does not reset the correction value CMP stored in the learning data storage unit  100   d . The meaning of resetting the correction value CMP includes returning the correction value CMP to the zero value that is the value at the beginning of on-road learning, as well as setting the correction value CMP to a predetermined value that is determined in advance so as to bring the correction value CMP closer to the zero value that is the value at the beginning of on-road learning. For example, this predetermined value is a value obtained by multiplying the correction value CMP shortly before being reset by a correction factor k (0&lt;k&lt;1). 
       FIG. 13  is one example of a flowchart illustrating a main part of control operation of the driving device ECU  100  shown in  FIG. 1 . The flowchart of  FIG. 13  is repeatedly executed. 
     In step S 10  corresponding to the function of the IG determining unit  100   f , it is determined whether or not the ignition signal IG has been switched from the OFF signal to the ON signal. When the determination result in step S 10  is affirmative, step S 20  is executed. When the determination result in step S 10  is negative, the process returns to the start. 
     In step S 20  corresponding to the function of the replacement determining unit  100   h , it is determined whether or not the offset adjustment has been performed on at least either of the resolvers  74 ,  76 . The offset adjustment is determined to have been performed, for example, when one of the value of the offset amount θoff, the date of detection, and the revision number of at least either of the resolvers  74 ,  76  stored in the offset storage unit  100   e  is different between the last execution of the flowchart and the current execution of the flowchart. When the determination result in step S 20  is affirmative, step S 70  is executed. When the determination result in step S 20  is negative, step S 30  is executed. 
     In step S 30  corresponding to the function of the sending-receiving unit  100   g , the maintenance information on the vehicle  10  is acquired. Then, step S 40  is executed. 
     In step S 40  corresponding to the function of the replacement determining unit  100   h , it is determined whether or not the replacement record of the compound transmission  40  included in the maintenance information has been updated. The replacement record is determined to have been updated, for example, when the latest date of replacement in the replacement record of the compound transmission  40  that is recorded in the vehicle&#39;s history included in the maintenance information stored in the maintenance storage unit  160   a  is different between the last execution of the flowchart and the current execution of the flowchart. Thus, after the replacement record included in the maintenance information is updated, it is determined only once that the replacement record has been updated. When the determination result in step S 40  is affirmative, step S 70  is executed. When the determination result in step S 40  is negative, step S 50  is executed. 
     In step S 50  corresponding to the function of the replacement determining unit  100   h , it is determined that the compound transmission  40  has not been replaced. Then, step S 60  is executed. 
     In step S 60  corresponding to the function of the rewriting executing unit  100   i , the correction value CMP is not reset. Then, the process returns to the start. 
     In step S 70  corresponding to the function of the replacement determining unit  100   h , it is determined that the compound transmission  40  has been replaced. As described above, in step S 40 , after the replacement record included in the maintenance information is updated, it is determined only once that the replacement record has been updated. Therefore, after the replacement record is updated, it is determined only once that the compound transmission  40  has been replaced. Then, step S 80  is executed. 
     In step S 80  corresponding to the function of the rewriting executing unit  100   i , the correction value CMP is reset. Then, the process returns to the start. 
     In this embodiment, the driving device ECU  100  includes (a) the learning data storage unit  100   d  that stores the correction value CMP learned by on-road learning, (b) the replacement determining unit  100   h  that determines whether or not the compound transmission  40  controlled by the parameter has been replaced, and (c) the rewriting executing unit  100   i  that resets the correction value CMP stored in the learning data storage unit  100   d  when the replacement determining unit  100   h  determines that the compound transmission  40  has been replaced. The replacement determining unit  100   h  determines that the compound transmission  40  has been replaced based on the offset adjustment that is performed upon replacement of the compound transmission  40 . Thus, the determination as to replacement of the compound transmission  40  is automatically made based on the offset adjustment that is performed upon replacement of the compound transmission  40 . Since the determination as to replacement of the compound transmission  40  is automatically made and the correction value CMP is reset, on-road learning is appropriately executed upon replacement of the compound transmission  40 , so that degradation of the controllability of the vehicle  10  after replacement of the compound transmission  40  is quickly mitigated. 
     In this embodiment, the adjustment performed upon replacement of the compound transmission  40  is the offset adjustment of the resolvers  74 ,  76  provided in the first rotating machine MG 1  and the second rotating machine MG 2 , respectively, that transmit a travel driving force to the compound transmission  40 . It is possible to infer that the first rotating machine MG 1  and the second rotating machine MG 2  have been re-mounted and, by extension, to automatically determine that the compound transmission  40  has been replaced, based on the offset adjustment of the resolvers  74 ,  76 . 
     In this embodiment, the replacement determining unit  100   h  determines that the compound transmission  40  has been replaced based on an update, resulting from the offset adjustment, in the replacement record of the compound transmission  40  included in the maintenance information. Since the determination as to replacement of the compound transmission  40  is automatically made based on an update in the replacement record and the correction value CMP is reset, degradation of the controllability of the vehicle  10  after replacement of the compound transmission  40  is quickly mitigated. 
     In this embodiment, after the replacement record of the compound transmission  40  included in the maintenance information is updated, the replacement determining unit  100   h  determines only once that the compound transmission  40  has been replaced. Since the compound transmission  40  is determined to have been replaced only once after the replacement record is updated, the correction value CMP is reset only once upon replacement of the compound transmission  40  and thus execution of unnecessary on-road learning is avoided. 
     In this embodiment, (a) the part for which determination as to replacement is made is the compound transmission  40  that is a transmission, and (b) the parameter that is the object of learning is the driving current value IDRx for controlling switching of the gear stage of the compound transmission  40 . Thus, when it is determined that the compound transmission  40  has been replaced, the correction value CMP relating to the driving current value IDRx stored in the learning data storage unit  100   d  is reset. Therefore, on-road learning is appropriately executed upon replacement of the compound transmission  40 , so that aggravation of shift shock that occurs when the gear stage is switched after replacement of the compound transmission  40  is quickly mitigated. 
     In this embodiment, the driving device ECU  100  further includes the IG determining unit  100   f  that determines whether or not the ignition signal IG has been switched from the OFF signal that stops the engine  12 , the first rotating machine MG 1 , and the second rotating machine MG 2  that are travel driving force sources to the ON signal that starts these travel driving force sources. The replacement determining unit  100   h  determines whether or not the compound transmission  40  has been replaced when the IG determining unit  100   f  determines that the ignition signal IG has been switched from the OFF signal to the ON signal. Since the correction value CMP is reset when the ignition signal IG is switched from the OFF signal to the ON signal, a sense of discomfort that the driver feels can be reduced compared with when the correction value CMP is reset while the vehicle is traveling. 
     While the embodiment of the present disclosure has been described in detail above based on the drawings, the disclosure can also be implemented with other aspects. 
     In the above-described embodiment, the offset storage unit  100   e  that stores the detected offset amounts θoff of the respective resolvers  74 ,  76  and the update information indicating that these offset amounts θoff have been updated is provided in the driving device ECU  100 , but the present disclosure is not limited to this aspect. For example, the detected offset amounts θoff of the respective resolvers  74 ,  76  may be stored in the offset storage unit  100   e  inside the driving device ECU  100 , while the update information indicating that these offset amounts θoff have been updated may be stored in the server  160 . In the case of this configuration, the update information on the detected offset amounts θoff of the respective resolvers  74 ,  76  is acquired from the server  160  before execution of step S 20  of the flowchart shown in  FIG. 13 . 
     In the above-described embodiment, the maintenance storage unit  160   a  that stores maintenance information is provided in the server  160 , but the present disclosure is not limited to this aspect. For example, a maintenance storage unit that stores maintenance information may be provided in the driving device ECU  100 . In the case of this configuration, in step S 30  of the flowchart shown in  FIG. 13 , the maintenance information may be acquired from the maintenance storage unit provided in the driving device ECU  100 . 
     In the above-described embodiment, the parameter that is the object of learning is the driving current value IDRx corresponding to the constant standby pressure of the hydraulic friction-engaging device to be engaged during clutch-to-clutch shifting, but the present disclosure is not limited to this aspect. For example, the parameter may be the driving current value of the driving current IDR for pack closing in the period from time t 1  to time t 2  shown in the time chart of  FIG. 8 , or may be the length of the period from time t 1  to time t 2  (quick charge period) or the length of the period from time t 2  to time t 3  (the period of constant standby pressure). Further, the parameter that is the object of learning is not limited to one relating to the hydraulic friction-engaging device to be engaged of the stepped transmission section  20  included in the compound transmission  40 ; the parameter may also be, for example, a fuel injection amount, fuel injection timing, or ignition timing in the engine control device  50  that controls the engine  12 . Thus, the term “parameter” refers to a control value for directly or indirectly controlling a part (e.g., the compound transmission  40  or the engine  12 ), and the operation of the part controlled is changed as this control value is corrected by on-road learning. 
     In the above-described embodiment, the learning unit  100   c  executes on-road learning based on the flare amount Neblow that is an amount of flare of the engine speed Ne, but the present disclosure is not limited to this aspect. For example, the learning unit  100   c  may execute on-road learning such that, instead of the flare amount Neblow, at least one of a flare amount Nmblow [rpm] that is an amount of flare of the MG 2  rotation speed Nm, a flare time (racing time) TMeblow [ms] that is a time of flare of the engine speed Ne, and a flare time TMmblow [ms] that is a time of flare of the MG 2  rotation speed Nm, shown in  FIG. 9 , is within a predetermined target range thereof. The flare amount Nmblow is detected as an amount of temporary rise in the MG 2  rotation speed Nm during a transitional period of gear shifting. The flare time TMeblow and the flare time TMmblow are detected as a time of temporary rise in the engine speed Ne and the MG 2  rotation speed Nm, respectively, during a transitional period of gear shifting. The predetermined target range of each of the flare time TMeblow, the flare amount Nmblow, and the flare time TMmblow is a range that is set in advance through experiment or design so as to realize execution of such clutch-to-clutch shifting that shift shock and shift time remain within allowable ranges. 
     In the above-described embodiment, a learning guard value GD [A] for preventing erroneous learning in on-road learning is not provided, but it may be provided. Specifically, when the absolute value of the correction value CMP that is a total value of the amounts of correction of the respective learning sessions in the case of repeated learning by on-road learning exceeds a range specified by the learning guard value GD (&gt;0) (i.e., when CMP&lt;−GD or GD&lt;CMP), the driving current value IDRx that is the object of learning is corrected by only a minimum value (−GD) or a maximum value (GD) in the specified range, i.e., by only the learning guard value GD. On the other hand, when the absolute value of the correction value CMP is within the range specified by the learning guard value GD (i.e., −GD≤CMP≤GD), correction of the driving current value IDRx by the correction value CMP is executed by on-road learning. The learning guard value GD specifies the upper limit value of the absolute value of the correction value CMP that is the sum of the amounts of correction resulting from repeated correction by on-road learning. 
     In the above-described embodiment, the “learning data” stored in the learning data storage unit  100   d  is the correction value CMP, but the present disclosure is not limited to this aspect. Instead of the correction value CMP, for example, the learned value LRN may be stored as the “learning data.” Since the learned value LRN is a value obtained by adding the correction value CMP to the pre-learning set value SET, storing the pre-learning set value SET and the learned value LRN in the learning data storage unit  100   d  is equivalent to storing the result of on-road learning. In the case of this aspect, the rewriting executing unit  100   i  resets the learned value LRN instead of resetting the correction value CMP. The meaning of resetting the learned value LRN includes returning the learned value LRN to the pre-learning set value SET that is the value at the beginning of on-road learning, as well as setting the learned value LRN to a predetermined value that is determined in advance so as to bring the leaned value LRN closer to the pre-learning set value SET that is the value at the beginning of on-road learning. For example, this predetermined value is a value obtained by adding, to the pre-learning set value SET, a value obtained by multiplying the difference between the learned value LRN shortly before being reset and the pre-learning set value SET by the correction factor k (0&lt;k&lt;1). 
     In the above-described embodiment, the part that is controlled by the parameter is the compound transmission  40 , but the present disclosure is not limited to this aspect. If there is a part, other than the compound transmission  40 , upon replacement of which an adjustment is performed, a determination as to replacement of that part may be made based on the adjustment, or a determination as to replacement of that part may be made based on a replacement record of that part included in maintenance information. 
     In the above-described embodiment, the driving device ECU  100  includes the learning data storage unit  100   d , the IG determining unit  100   f , the replacement determining unit  100   h , and the rewriting executing unit  100   i , but the present disclosure is not limited to this aspect. The driving device ECU  100  and other control functions may, as necessary, be integrated into one electronic control device, or the driving device ECU  100  may, as necessary, be functionally divided into a different electronic control device and an external memory. 
     In the above-described embodiment, the maintenance information on the vehicle  10  is sent from the server  160  to the first gateway ECU  150  by wireless communication, and the sent maintenance information is sent from the first gateway ECU  150  to the driving device ECU  100 , but the present disclosure is not limited to this aspect. For example, the maintenance information on the vehicle  10  may be sent from the server  160  to the second gateway ECU  152 , and the sent maintenance information may be sent from the second gateway ECU  152  to the driving device ECU  100 . The second gateway ECU  152  has substantially the same control function as the first gateway ECU  150 , but is different from the first gateway ECU  150  in that the maintenance information is sent to the second gateway ECU  152  through the connector  170  from the server  160  that is connected thereto by wire, and not wirelessly. Thus, the second gateway ECU  152  functionally includes a communication unit that can receive data from the server  160  instead of the wireless communication unit  150   a , and the sending-receiving unit  150   b.    
     In the above-described embodiment, the vehicle  10  is a hybrid vehicle, but the present disclosure is not limited to this aspect. For example, the vehicle  10  may also be a vehicle that does not have the engine  12  and has only rotating machines, such as the first rotating machine MG 1  and the second rotating machine MG 2 , as travel driving force sources. Alternatively, the vehicle  10  may have only one rotating machine that transmits a travel driving force to the transmission. In the case of this configuration, whether or not the offset adjustment has been performed is determined based on a resolver provided in that one rotating machine. 
     What has been described above is merely an embodiment of the present disclosure. The disclosure can be implemented with various changes and improvements based on the knowledge of those skilled in the art made to the aspects thereof within the scope of the gist of the disclosure.