CONTROL APPARATUS FOR VEHICLE

A control apparatus for a vehicle including: (i) an engine; (ii) an input rotary member connected to the engine; (iii) an electric transmission mechanism that includes a differential mechanism configured to receive a power of the engine via the input rotary member and an electric motor connected to the differential mechanism; and (vi) a mechanical oil pump configured, when being driven by rotation of the input rotary member, to supply an oil for lubricating the differential mechanism. The differential mechanism includes a first rotary element connected to the input rotary member, a second rotary element connected to the electric motor, and a third rotary element connected to drive wheel. The control apparatus is configured to execute an electric-motor stop control for stopping the electric motor, each time a cumulative time or a cumulative distance of a towed running of the vehicle reaches a predetermined time or distance.

This application claims priority from Japanese Patent Application No. 2022-212276 filed on Dec. 28, 2022, the disclosure of which is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a control apparatus for a vehicle including an engine, an electric transmission mechanism and a mechanical oil pump.

BACKGROUND OF THE INVENTION

There is well known a control apparatus for a vehicle including: (i) a drive wheel; (ii) an engine; (iii) an input rotary member to which the engine is connected in a power transmittable manner; (iv) an electric transmission mechanism that includes (iv-1) a differential mechanism configured to receive a power of the engine via the input rotary member and (iv-2) an electric motor connected to the differential mechanism in a power transmittable manner, such that a differential state of the differential mechanism is controlled with an operation state of the electric motor being controlled; and (v) a mechanical oil pump configured, when being driven by rotation of the input rotary member, to supply an oil for lubricating the differential mechanism. For example, Patent Document 1 discloses a lubricating device for a vehicle. This Patent Document 1 discloses that an oil for lubricating a transmission mechanism is supplied by a mechanical oil pump when an engine is in an operation state, and that the oil for lubricating the transmission mechanism is supplied by driving an electric oil pump provided in a vehicle when the vehicle is towed with the engine being in a stop state.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

By the way, in a vehicle that does not include an electric oil pump, the lubrication of the transmission mechanism using the electric oil pump cannot be performed during a towed running with the engine being in a stop state. Therefore, in the vehicle that is not provided with the electric oil pump, when the vehicle continues to be towed for a long time or a long distance, there is a risk that an oil for lubricating the transmission mechanism could become insufficient.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a control apparatus for a vehicle, which makes it possible to lubricate a transmission mechanism by using a mechanical oil pump during a towed running with an engine being in a stop state.

According to a first aspect of the present invention, there is provided a control apparatus for a vehicle including: (i) a drive wheel; (ii) an engine; (iii) an input rotary member to which the engine is connected in a power transmittable manner; (iv) an electric transmission mechanism that includes (iv-1) a differential mechanism configured to receive a power of the engine via the input rotary member and (iv-2) an electric motor connected to the differential mechanism in a power transmittable manner, such that a differential state of the differential mechanism is controlled with an operation state of the electric motor being controlled; and (v) a mechanical oil pump configured, when being driven by rotation of the input rotary member, to supply an oil for lubricating the differential mechanism, wherein the differential mechanism includes a first rotary element connected to the input rotary member in a power transmittable manner, a second rotary element to which the electric motor is connected in a power transmittable manner, and a third rotary element connected to the drive wheel. The vehicle is to be towed with the engine being in a stop state and with the drive wheel being grounded during a towed running. The control apparatus is configured to execute an electric-motor stop control for a predetermined time, each time a cumulative time of the towed running reaches a predetermined time, or each time a cumulative distance of the towed running reaches a predetermined distance. When the electric-motor stop control is being executed, the electric motor is controlled such that rotation of the electric motor is stopped. Further, the differential mechanism is constructed such that a rotational speed of the first rotary element is between a rotational speed of the second rotary element and a rotational speed of the third rotary element.

According to the first aspect of the present invention, the motor stop control is executed for the predetermined time each time the cumulative time during the towed running in the state in which the engine is stopped and the drive wheel is grounded reaches the predetermined time or each time the cumulative distance during the towed running reaches the predetermined distance. Accordingly, in the differential mechanism, rotation of the second rotary element to which the electric motor is connected is stopped in a state in which the third rotary element connected to the drive wheel is rotated, so that the first rotary element connected to the input rotary member is rotated whereby the mechanical oil pump is rotationally driven. Thus, the transmission mechanism can be lubricated using the mechanical oil pump during the towed running in the engine stop state.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Embodiment

FIG.1is a view schematically showing a configuration of a vehicle10to which the present invention is applied, and also a control function and a main part of a control system for various kinds of control in the vehicle10. As shown inFIG.1, the vehicle10includes an engine12, a first electric motor MG1and a second electric motor MG2. The vehicle10includes also drive wheels14and a power transmission device16provided in a power transmission path between the engine12and the drive wheels14. The vehicle10is an electric vehicle, particularly, a hybrid electric vehicle, including the engine12and the second electric motor MG2, which function as power sources.

The engine12is a known internal combustion engine. In the engine12, an engine torque Te which is a torque of the engine12is controlled by an engine control device50which is provided in the vehicle10and which is controlled by an electronic control apparatus90that will be described later.

Each of the first electric motor MG1and the second electric motor MG2is a rotary electric machine and is a so-called motor generator. The first electric motor MG1and the second electric motor MG2are connected to a high-voltage battery54provided in the vehicle10via an inverter52provided in the vehicle10. The inverter52is controlled by the electronic control apparatus90, such that an MG1torque Tg as a torque of the first electric motor MG1and an MG2torque Tm as a torque of the second electric motor MG2are controlled. The first electric motor MG1and the second electric motor MG2are provided in a casing18attached to a body of the vehicle10.

The power transmission device16includes, in a casing18, a damper20, an input shaft22, a transmission portion24, a composite gear26, a driven gear28, a driven shaft30, a final gear32, a differential gear34and a reduction gear36. The power transmission device16includes a rotor shaft RSmg1integrally connected to a rotor MG1rof the first electric motor MG1and a rotor shaft RSmg2integrally connected to a rotor MG2rof the second electric motor MG2in the casing18. The power transmission device16further includes a pair of drive shafts38connected to the differential gear34.

The input shaft22functions as an input rotary member of the transmission portion24, and is connected to a crankshaft12aof the engine12via the damper20and other elements. The input shaft22is an input rotary member to which the engine12is connected in a power transmittable manner, and is configured to receive a power from the engine12. The transmission portion24is connected to the input shaft22. The compound gear26is a rotary body that is an output member of the transmission portion24. A drive gear26ais formed on a part of the outer circumferential surface of the composite gear26. The drive gear26ais an output-side rotary member of the transmission portion24. The driven gear28meshes with the drive gear26a. The driven gear28and the final gear32are fixed on the driven shaft30, and are unrotatable relative to each other. The final gear32has a diameter smaller than that of the driven gear28, and meshes with the differential-ring gear34aof the differential-gear34. The reduction gear36has a diameter smaller than that of the driven gear28, and meshes with the driven gear28. The rotor shaft RSmg2is connected to the reduction gear36, so that the second electric motor MG2is connected to the reduction gear36in a power transmittable manner.

The power transmission device16transmits the power outputted from the engine12to the driven gear28via the transmission portion24. Further, the power transmission device16transmits a power outputted from the second electric motor MG2to the driven gear28via the reduction gear36. The power transmission device16transmits the power transmitted to the driven gear28to the drive wheels14sequentially via the driven shaft30, the final gear32, the differential gear34and the drive shaft38, for example.

The transmission portion24includes the first electric motor MG1, the rotor shaft RSmg1and a planetary gear device40. The planetary gear device40is a known single-pinion planetary gear device including a sun gear S, a carrier CA, a ring gear R and pinions P. The sun gear S is connected to the rotor shaft RSmg1in a power transmittable manner. In other words, the first electric motor MG1is connected to the sun gear S in a power transmittable manner. The carrier CA is connected to the input shaft22in a power transmittable manner. That is, the engine12is connected to the carrier CA in a power transmittable manner via the input shaft22, for example. The ring gear R is formed on a part of the inner circumferential surface of the composite gear26, and is integrally connected to the drive gear26a. That is, the ring gear R is connected to the drive wheels14in a power transmittable manner. The pinions P are supported by the carrier CA so as to be rotatable and revolvable. The ring gear R meshes with the sun gear S via the pinions P.

The planetary gear device40functions as a differential mechanism configured to produces a differential effect. The power of the engine12is inputted to the planetary gear device40via the input shaft22. The first electric motor MG1is an electric motor that is connected to the planetary gear device40in a power transmittable manner. The planetary gear device40is a power distribution mechanism configured to mechanically distribute the power of the engine12to the first electric motor MG1and the drive gear26a. The transmission portion24is a known electric transmission mechanism in which a differential state of the planetary gear device40is controlled with an operation state of the first electric motor MG1being controlled.

The vehicle10further includes a mechanical oil pump56. In this embodiment, the mechanical oil pump56is referred to as an MOP56. The MOP56is connected to the input shaft22in a power transmittable manner. The MOP56is to be rotationally driven by the engine12so as to supply an oil Fld used for lubrication and cooling of each part of the power transmission device16. That is, the MOP56is driven by the rotation of the input shaft22to supply the oil Fld that lubricates the planetary gear device40, for example.

FIG.2is a collinear chart showing a relative relationship among rotational speeds of rotary elements in the transmission portion24. InFIG.2, three vertical lines Y1, Y2, Y3correspond to the three rotary elements of the planetary gear device40constituting the transmission portion24. The vertical line Y1represents the rotational speed of the sun gear S corresponding to the second rotary element RE2to which the first electric motor MG1(see “MG1” inFIG.2) is connected in a power transmittable manner. The vertical line Y2represents the rotational speed of the carrier CA corresponding to the first rotary element RE1to which the engine12is connected in a power transmittable manner. The MOP56(see “MOP” inFIG.2) is connected to the input shaft22to which the engine12is connected in a power transmittable manner. The vertical line Y3represents the rotational speed of the ring gear R corresponding to the third rotary element RE3that integrally connected to the drive gear26a(see “OUT” inFIG.2). As shown inFIG.2, the planetary gear device40as the differential mechanism is constructed such that the rotational speed of the carrier CA as the first rotary element RE1is between the rotational speed of the sun gear S as the second rotary element RE2and the rotational speed of the ring gear R as the third rotary element RE3. The second electric motor MG2(see “MG2” inFIG.2) is connected to the driven gear28meshing with the drive gear26avia the reduction gear36, for example, in a power transmittable manner. Intervals among the vertical lines Y1, Y2, Y3are dependent on a gear ratio ρ (=number of teeth of the sun gear/number of teeth of the ring gear) of the planetary gear device40. When the distance between the sun gear and the carrier is set to an interval corresponding to “1” in the relationship among the vertical axes of the collinear chart, the distance between the carrier and the ring gear is set to an interval corresponding to the gear ratio ρ.

In the transmission portion24, the relationship between the rotational speed of the sun gear S and the rotational speed of the ring gear R is indicated by straight lines Le, Lm that intersect the vertical line Y2. The solid line Le inFIG.2indicates an example of relative speeds of the rotary elements during a forward running in an HEV running mode that is a running mode enabling an engine running, i.e., hybrid running (=HEV running), in which at least the engine12is used as a power source. In the HEV running mode, when a reaction torque, i.e., a negative torque from the first electric motor MG1, is inputted in positive rotation to the sun gear S with respect to the engine torque Te inputted to the carrier CA in the differential mechanism34, an engine direct transmission torque Td [=Te/(1+ρ0)=−(1/ρ0)×Tg] appears in the ring gear R as a positive torque in positive rotation. In accordance with a required drive torque Trdem, a sum of the engine direct transmission torque Td and the MG2torque Tm is transmitted to the drive wheels14as the drive torque Tr in the forward direction of the vehicle10. In this instance, the transmission portion24can be operated as an electrically controlled continuously variable transmission in which the gear ratio γ (=input rotational speed Ni/output rotational speed No) is continuously variable. The input rotational speed Ni is a rotational speed of the input shaft22, and is the same value as the engine rotational speed Ne that is a rotational speed of the engine12. The output rotational speed No is a rotational speed of the drive gear26a.

The broken line Lm inFIG.2indicates an example of relative speeds of the rotary elements during a forward running in a BEV running mode that is a running mode enabling a motor running (=BEV running) in which running of the vehicle10is performed using the second electric motor MG2as the power source in a state in which operation of the engine12is stopped. In the BEV running mode, the first electric motor MG1is in a no-load state and is idled in a negative direction, and the carrier CA is set to 0 rotation, that is, the engine rotational speed Ne is set to 0. In this state, only the second electric motor MG2is used as the power source, and the MG2torque Tm, which becomes a positive torque by the positive rotation transmitted to the driven gear28, is transmitted to the drive wheels14as the drive torque Tr in the forward direction of the vehicle10.

FIG.3is a view showing an example of an electrical configuration of an electric circuit unit60including the inverter52provided in the vehicle10. As shown inFIG.3, the vehicle10further includes an auxiliary battery58in addition to the high-voltage battery54. The electric circuit unit60controls the first electric motor MG1and the second electric motor MG2.

The high-voltage battery54is a chargeable and dischargeable DC power supply, and is a secondary battery such as a nickel-hydrogen secondary battery or a lithium-ion battery. The high-voltage battery54is connected to the electric circuit unit60.

The stored electric power is supplied from the high-voltage battery54to the first electric motor MG1and the second electric motor MG2via the electric circuit unit60. The electric power generated by a power generation control of the first electric motor MG1and the electric power generated by a regeneration control of the second electric motor MG2are supplied to the high-voltage battery54via the electric circuit unit60. The high-voltage battery54is a battery for driving the vehicle10.

The electric circuit unit60includes a DC-DC converter62and a power control circuit64.

The DC-DC converter62is connected to the high-voltage battery54. The DC-DC converter62functions as a charging device that reduces the voltage of the high-voltage battery54to a voltage equivalent to that of the auxiliary battery58and charges the auxiliary battery58. The auxiliary battery58supplies the electric power for operating auxiliary devices provided in the vehicle10. The auxiliary battery58supplies the electric power for operating the electronic control apparatus90, for example.

The power control circuit64includes a boost converter66and the inverter52. The power control circuit64controls the electric power exchanged between the high-voltage battery54and each of the first electric motor MG1and the second electric motor MG2.

The boost converter66is a buck-boost circuit having a function of boosting the voltage of the high-voltage battery54and supplying the boosted voltage to the inverter52, and a function of bucking the voltage converted into a direct current by the inverter52and supplying the bucked voltage to the high-voltage battery54.

The inverter52includes an MG1power module68, a MG2power module70and a capacitor72. The MG1power module68includes transistors74u,74v,74w,76u,76v,76w. In this embodiment, the transistors74u,74v,74wwill be referred to as transistors74, and the transistors76u,76v,76wwill be referred to as transistors76, unless otherwise specified. The MG1power module68constitutes a three-phase bridge circuit of an U-phase, a V-phase and a W-phase, by the transistors74,76, for example. The transistors74,76are turned ON and OFF as switching elements to convert a DC current into a three-phase AC current. The transistors74constitute upper arms of the transistors74,76. The transistors76constitute lower arms of the transistors74,76. Since the MG2power module70has the same configuration as the MG1power module68, the MG2power module70is not described herein. Each of the first and second electric motors MG1, MG2is a three-phase alternating-current synchronous motor that is to be driven by inverter52having a plurality of switching elements.

The inverter52converts the direct current from the boost converter66into an alternating current for driving the first electric motor MG1and the second electric motor MG2. The inverter52converts the alternating current generated by the first electric motor MG1using the power of the engine12and the alternating current generated by the second electric motor MG2using the regenerative braking, into the direct current. The invertor52supplies the alternating current generated by the first electric motor MG1as a power for driving the second electric motor MG2depending on a running state of the vehicle10.

Referring back toFIG.1, the vehicle10includes the electronic control apparatus90as a controller including a control apparatus of the vehicle10related to various controls of the engine12and the electric motors, for example. The electronic control apparatus90includes, for example, a so-called microcomputer including a CPU, a RAM, a ROM and an input/output interface. The electronic control apparatus90performs the various controls in the vehicle10, by the CPU performing signal processing in accordance with programs pre-stored in the ROM while using a temporary storage function of the RAM.

The electronic control apparatus90is supplied with various signals (e.g., engine rotational speed Ne (=input rotational speed Ni), output rotational speed No corresponding to vehicle running speed V, MG1rotational speed Ng of the first electric motor MG1, MG2rotational speed Nm of the second electric motor MG2, accelerator opening degree θacc, throttle-valve opening degree θth, brake-ON signal Bon, power-switch signal PSon and toeing-ON signal FTon) based on detection values supplied from various sensors provided in the vehicle10(e.g., engine speed sensor80, output speed sensor81, MG1speed sensor82, MG2speed sensor83, accelerator opening degree sensor84, throttle-valve opening degree sensor85, brake switch86, power switch87and toeing selection switch88).

The power switch87is a switch that is to be operated by a driver of the vehicle10so as to switch a vehicle-power supply state, i.e., a supply state of power in the vehicle10. The power switch87is, for example, a momentary-type push button switch, and is to be pushed to a switch-ON position by the driver. Each time the power switch87is pushed to the switch-ON position, the power switch87outputs a power switch signal PSon corresponding to the switch-ON position.

The electronic control apparatus90detects the operation of the power switch87by the driver based on the power switch signal PSon. The operation of the power switch87by the driver is a vehicle-power supply operation for switching the vehicle-power supply state. The electronic control apparatus90switches the vehicle-power supply state in accordance with the power switch signal Pson and the brake-ON signal Bon, for example.

The vehicle-power supply state includes, for example, an off (=“OFF”) state, an accessory-ON (=“ACC”) state, an ignition-ON (=“IG-ON”) state and a ready-ON (=“READY-ON”) state. The OFF state is, for example, a power supply state for disabling running of the vehicle10and also disabling some functions not related to the running of the vehicle10. The ACC state is a power supply state in which, for example, a combination meter (not shown) is turned OFF to disable the running of the vehicle10but to enable some functions not related to the running of the vehicle10. The IG-ON state is, for example, a power supply state for turning ON the combination meter to enable control of functions other than control of the running of the vehicle10. The IG-ON state is a power supply state in which the drive torque Tr cannot be generated, i.e., a power supply state in which the vehicle10cannot start or run even if the accelerator is turned ON. That is, the IG-ON state is a predetermined power supply state in which the engine12cannot be brought into an operated state and the vehicle10cannot be driven. The READY-ON state is, for example, a power supply state for turning ON the combination meter to enable the running of vehicle10. That is, the READY-ON state is a power supply state in which the running of the vehicle10can be controlled, and is a power supply state in which the vehicle10can start and run when the accelerator is turned ON.

The towing selection switch88is a switch that is to be operated by the driver to select a flat towing mode. The flat-towing mode is a driving mode of the vehicle10corresponding to a towed running in which the vehicle10is towed. The towed running in the flat towing mode is, for example, a flat towing in which the vehicle10is towed in a state in which the engine12is stopped and all the wheels of the vehicle10are grounded. The flat towing is used, for example, in a situation in which the vehicle10is connected to a camping car or a motor home and is moved, and is also referred to as “four-down towing”, “dinghy towing”, “recreational towing” or the like. The towing selection switch88is, for example, a dial-type changeover switch, and outputs the towing-ON signal FTon when being switched to a flat-towing selection position by the driver.

Various command signals (for example, an engine control command signal Se for controlling the engine12, an MG control command signal Smg for controlling each of the first electric motor MG1and the second electric motor MG2) are outputted from the electronic control apparatus90to respective devices (for example, the engine control device50, the inverter52) provided in the vehicle10.

The electronic control apparatus90includes power-source control means in the form of a power-source control portion92, and towing control means in the form of a towing control portion94, in order to realize various controls in the vehicle10.

The power-source control portion92has an engine control function of controlling the operation of the engine12and a motor control function of controlling the operations of the first electric motor MG1and the second electric motor MG2via the inverter52.

The power-source control portion92calculates a drive request amount for the vehicle10by the driver, for example, by applying the accelerator opening degree θacc and the vehicle running speed V to a drive request amount map. The drive demand amount map is for obtaining the drive demand amount, and is a predetermined relationship which is obtained by experimentation or determined by an appropriate design theory and which is stored in advance. The drive request amount is, for example, a drive torque Tr requested to the vehicle10, that is, a requested drive torque Trdem [Nm] of the drive wheels14. In other words, the requested drive torque Trdem is a requested drive power Prdem [W] at the vehicle running speed V at that time. A requested drive force Frdem [N] of the driving wheels14may be used as the requested drive force.

The power-source control portion92outputs the engine control command signal Se and the MG control command signal Smg so as to realize the required drive power Prdem in consideration of, for example, a transmission loss and an auxiliary device load. For example, the engine control command signal Se is a command value of the engine power Pe that is the power of the engine12that outputs the engine torque Te at the engine rotational speed Ne at that time, in consideration of an engine optimum fuel consumption point, for example. The MG control command signal Smg is a command value of a generated power Wg of the first electric motor MG1that outputs the MG1torque Tg at the MG1rotational speed Ng at the time of outputting the command as the reaction torque of the engine torque Te. The MG control command signal Smg is a command value of a power consumption Wm of the second electric motor MG2that outputs the MG2torque Tm at the MG2rotational speed Nm at the time of outputting the command of the generated power Wg. The engine optimum fuel consumption point is determined in advance as an engine operation point at which a total fuel efficiency of the vehicle10is maximized in consideration of, for example, a charge/discharge efficiency of the high-voltage battery54and a transmission efficiency of the power transmission device16, for example, in addition to the fuel consumption of the engine12alone.

The power-source control portion92sets the running mode of vehicle10to the BEV running mode when the requested drive power Prdem is in a BEV running region, namely, when the requested drive power Prdem is smaller than a predetermined threshold value. On the other hand, the power-source control portion92sets the running mode of the vehicle10to the HEV running mode when the required drive power Prdem is in a HEV running region, namely, when the requested drive power Prdem is not smaller than the predetermined threshold value. However, even when the required drive power Prdem is in the BEV running region, the power-source control portion92establishes the HEV running mode when the high-voltage battery54needs to be charged or when the engine12and other elements need to be warmed up.

When the toeing-ON signal FTon is outputted, the towing control portion94turns ON a flag of the flat towing mode. When the flag of the flat towing mode is turned ON, the towing control portion94sets the vehicle power supply state to the IG-ON state and sets the transmission portion24to a neutral state. The flat towing is performed in the neutral state of the transmission portion24. The neutral state of the transmission portion24is realized by, for example, causing the first electric motor MG1to idle in a no-load state so as not to take a reaction torque with respect to the engine torque Te, whereby the transmission portion24is brought into a state in which the engine torque Te cannot be transmitted.

When the flat towing is being performed, the drive gear26ais rotated with the rotation of the drive wheels14, so that it is necessary to lubricate the planetary gear device40and other elements. On the other hand, when the flat towing is being performed, the engine12is in a stop state and the input shaft22is not rotated, the MOP56is not driven and the oil Fld that lubricates the planetary gear device40and other elements is not supplied. Further, when flat towing is being performed, the vehicle power supply state is set to the IG-ON state, so that the engine12cannot be started. Therefore, in a case where the vehicle10is not provided with an electric oil pump, there is a possibility that the oil Fld for lubricating the planetary gear device40and other elements becomes insufficient when the vehicle10continues to run in the flat towing mode for a long time or a long distance.

During the flat towing, the transmission portion24is in the neutral state, and the drive gear26ais rotated by the rotation of the drive wheels14. Therefore, if the first electric motor MG1is controlled so as to stop the rotation of the first electric motor MG1during the flat towing, the input shaft22can be rotated to drive the MOP56.

During the flat towing, the towing control portion94outputs the MG control command signal Smg for executing an electric-motor stop control for controlling the first electric motor MG1so as to stop the rotation of the first electric motor MG1, namely, outputs the MG control command signal Smg for executing an MG1stop control CTstmg1. The towing control portion94executes the MG1stop control CTstmg1for a predetermined time TMf at a predetermined interval IVf during the flat towing. The predetermined time TMf is, for example, a predetermined control time for sufficiently supplying the oil Fld for lubricating the planetary gear device40and other elements.

The predetermined interval IVf is, for example, each time a cumulative time TMcnt of the flat towing reaches a predetermined time TMcntf, or each time a cumulative distance DTcnt of the flat towing reaches a predetermined distance DTcntf. The cumulative time TMcnt may be interpreted to mean a cumulative time for which the flat towing has been performed. The cumulative distance DTcnt may be interpreted to mean a cumulative distance by which the vehicle10has run by performance of the flat towing. A time when the flat towing is performed is, for example, when the vehicle10runs in a state in which the flat towing mode is selected, namely, in a state in which the flat towing mode is ON. Alternatively, the time when the flat towing is performed is, for example, when the vehicle10runs in substantially in the same vehicle state as running in the flat towing mode, namely, in a state in which the vehicle-power supply state is the IG-ON state and the running speed V exceeds a predetermined speed Vf. The predetermined speed Vf is, for example, a predetermined lower limit value for determining that the vehicle10is being moved by the flat towing.

The cumulative time TMcnt is a numerical value obtained by measuring a running time of the flat towing, i.e., a duration time count. The cumulative distance DTcnt is a numerical value obtained by measuring a running distance of the flat towing, i.e., a continuous distance count. The predetermined time TMcntf and the predetermined distance DTcntf are predetermined thresholds for determining that it is necessary to lubricate the planetary gear device40and other elements, for example. After the execution of the MG1stop control CTstmg1, the towing controller94clears the cumulative time TMcnt to reset the cumulative time TMcnt to 0, and clears the cumulative distance DTcnt to reset the cumulative distance DTcnt to 0.

The MG1stop control CTstmg1is, for example, a MG1three-phase ON control CTonmg1, i.e., a three-phase ON control in the MG1power module68of the inverter52. The towing controller94executes the MG1three-phase ON control CTonmg1by controlling the inverter52to turn ON all of the upper arms (transistors74) of the transistors74,76and to turn OFF all of the lower arms (transistors76) of the transistors74,76. Alternatively, the towing controller94executes the MG1three-phase ON control CTonmg1by controlling the inverter52to turn OFF all of the upper arms of the transistors74,76and to turn ON all of the lower arms of the transistors74,76. When the MG1three-phase ON control CTonmg1is executed while the first electric motor MG1is rotating, the first electric motor MG1generates a drag torque, so that the rotation of the first electric motor MG1is stopped. The drag torque of the first electric motor MG1is a torque acting in a direction for reducing an absolute value of the MG1rotational speed Ng.

FIG.4is a view showing the MG1three-phase ON control CTonmg1.FIG.4shows examples of execution and non-execution of the MG1three-phase ON control CTonmg1, in a collinear chart similar to that ofFIG.2. InFIG.4, a broken line Lr indicates an example of relative speeds of the rotary elements in the flat towing during the non-execution of the MG1three-phase ON control CTonmg1. When the MG1three-phase ON control CTonmg1is not executed, the first electric motor MG1is idled in a no-load state, so that the rotation of the carrier CA, i.e., the rotation of the input shaft22is stopped. On the other hand, a solid line Lon indicates an example of the relative speeds of the rotary elements in the flat towing during execution of the MG1three-phase ON control CTonmg1. When the MG1three-phase ON control CTonmg1is executed, the first electric motor MG1that has been idled generates a drag torque, and the rotation of the first electric motor MG1is changed to be stopped. As a result, the input shaft22is rotated and the MOP56is driven, so that the oil Fld for lubricating the planetary gear device40and other elements is supplied.

The MG1three-phase ON control CTonmg1is a control for decelerating the first electric motor MG1by generating a braking torque caused by a counter-electromotive force of the rotating first electric motor MG1, and is not a control for outputting a positive torque or a negative torque as the MG1torque Tg. The MG1three-phase ON control CTonmg1is not a control for outputting a torque for cranking the engine12by the first electric motor MG1. Therefore, the MG1three-phase ON control CTonmg1can be executed even in a state in which the high-voltage battery54is disconnected from the electric circuit unit60by a relay (not shown). When the vehicle power supply state is the IG-ON state, for example, the high-voltage battery54is disconnected from the electric circuit unit60by the relay (not shown).

FIG.5is a flowchart showing a main part of a control operation of the electronic control apparatus90, and also a control operation for lubricating the planetary gear device40and other elements by using the MOP56during the flat towing. A control routine ofFIG.5is executed in a repeated manner, for example.

In the control routine ofFIG.5, each step corresponds to function of the towing control portion94. The control routine is initiated with step S10that is implemented to determine whether or not the flat towing mode is ON, or determine whether or not the vehicle power supply state is the IG-ON state and the vehicle running speed V exceeds a predetermined speed Vf. When a negative determination is made at step S10, one cycle of execution of the control routine is terminated. When an affirmative determination is made at step S10, the cumulative time TMcnt as a continuous time count of the flat towing is updated and the cumulative distance DTcnt as a continuous distance count of the flat towing are updated at step S20. Next, at step S30, it is determined whether or not the cumulative time TMcnt exceeds the predetermined time TMcntf, or whether or not the cumulative distance DTcnt exceeds the predetermined distance DTcntf. When a negative determination is made at step S30, one cycle of execution of the control routine is terminated. When an affirmative determination is made at step S30, step S40is implemented to execute the MG1three-phase ON control CTonmg1for the predetermined time TMf. Further, the cumulative time TMcnt and the cumulative distance DTcnt are cleared.

As described above, the MG1stop control CTstmg1is executed for the predetermined time TMf each time the cumulative time TMcnt during the flat towing reaches the predetermined time TMcntf or each time the cumulative distance DTcnt during the flat towing reaches the predetermined distance DTcntf. Accordingly, in the planetary gear device40, the rotation of the second rotary element RE2is stopped in a state in which the third rotary element RE3is rotated, so that the first rotary element RE1is rotated whereby the MOP56is rotationally driven. Therefore, the planetary gear device40and other elements can be lubricated using the MOP56during the flat towing.

According to the present embodiment, the flat towing is performed in the neutral state of the transmission portion24in which the first electric motor MG1is idled in the no-load state. As a result, the flat towing is appropriately performed. In addition, the MOP56is rotationally driven by the MG1stop control CTstmg1executed during the flat towing.

Further, according to the present embodiment, the time when the flat towing is performed is the time when the vehicle10runs in the state where the vehicle power supply state is the IG-ON state and the vehicle speed V exceeds the predetermined vehicle speed Vf, or the time when the vehicle10runs in the state where the flat towing mode is selected. As a result, it is possible to lubricate the planetary gear device40and other elements using the MOP56during the flat towing.

Further, according to the present embodiment, since the MG1stop control CTstmg1is the MG1three-phase ON control CTonmg1, the rotation of the first electric motor MG1is appropriately stopped during the flat towing.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the present invention is also applicable to other embodiments.

For example, in the above-described embodiment, the towed running of the vehicle10in which the MG1stop control CTstmg1is executed is not limited to the flat towing. For example, since the drive gear26ais rotated also in a state in which driven wheels are not in contact with the ground and only the drive wheels14are in contact with the ground, it is necessary to lubricate the planetary gear device40and the like. Therefore, the towed running of the vehicle10in which the MG1stop control CTstmg1is to be executed may be a towed running in a state in which the engine12is stopped and the driving wheels14are grounded.

Further, in the above-described embodiment, the present invention can be applied to any vehicle provided with an electric transmission mechanism including a differential mechanism having at least three rotary elements.

It should be noted that the above-described embodiment is merely one embodiment, and the present invention can be implemented in a mode in which various changes and improvements are added based on the knowledge of those skilled in the art.

NOMENCLATURE OF ELEMENTS