Abstract: A vehicle driving apparatus configured with a drive power source, a fluid coupling, a transmission apparatus; and a control apparatus. A rotation of a drive input member driven by the drive power source is transmitted to a shift input member via the fluid coupling and a rotation of the shift input member is shifted by the transmission apparatus and then transmitted to an output member. When a state shift command for shifting from a non-transmission state to a transmission state is input into a control apparatus in a state in which the drive power source does not generate a driving force, the control apparatus performs a shift input rotation operation before engaging a frictional engagement element and shifting to the transmission state by causing the drive power source to generate the driving force and rotating the shift input member via the fluid coupling while maintaining the non-transmission state.

Abstract: A method for controlling a motor vehicle drive train including a combustion engine, an electric machine and a transmission, which are coupled by a summation gear system, having two input and one output elements, and a clutch. One input element is coupled to the crankshaft of the combustion engine, the other input element is coupled to the rotor of the electric machine and the output element is coupled to the input shaft of the transmission and the clutch is arranged between two elements of the summation gear system, such that when the clutch is disengaged a speed difference between the combustion engine and the transmission input shaft is synchronized by the electric machine and, if necessary, by a controlled engagement of the clutch. To improve synchronization, at the beginning of the synchronization the clutch is brought to its contact point before the engagement of the bridging clutch.

Abstract: A powertrain system includes a transmission operative to transfer power between an input member and first and second torque machines and an output member. The first and second torque machines are connected to an energy storage device and the transmission is operative in a continuously variable operating range state.

Abstract: A control device for a vehicle which includes a differential portion controlling a differential state between the number of rotations of an input shaft connected to an engine, and the number of rotations of an output shaft connected to drive wheels, with controlling an operating state of an electric motor, and an automatic shifting portion forming part of a power transmitting path. The control device prevents degradation in operability of the vehicle, even in the presence of a shifting command resulting from a manual shift operation when the automatic shifting portion remains under a limited shifting state. More particularly, if the shifting command is present due to the manual shift operation, the differential state of the differential portion is controlled, thereby causing a variation in a drive force at a rate corresponding to the shifting command.

Abstract: A method controls a friction clutch disposed between an internal combustion engine and a change speed transmission. The friction clutch is controlled in such a way that it transmits an average coupling torque of the internal combustion engine and does not transmit periodically occurring peak values of the coupling torque. In addition, a control unit is programmed to carry out the method.

Abstract: An automotive transmission transitions from a drive gear to a neutral gear when an engine is shutdown. During a rolling pull-up, a crankshaft of the engine will be spun up to a desired speed and the transmission will transition from the neutral gear to an appropriate gear based on a shift schedule. A target transmission input speed is commanded to be a synchronous speed plus an offset to smoothly transition out of electric axle drive propulsion.

Abstract: A powertrain is provided with a first input clutch and a second input clutch, each of which is selectively engageable to connect an engine with a transmission input member. Selective engagement of the first input clutch permits a motor to power the engine to start the engine. Selective engagement of the second input clutch permits the engine to power the transmission for propulsion.

Abstract: When the power transmitting path in an automatic shifting portion (20) is interrupted, a Co-lock control is executed to allow a differential portion (11) to be placed in a non-differential or nearly non-differential state with rotary elements (RE1 to RE3) kept in a unitary rotation. Thus, an engine (8), a first electric motor (M1) and a second electric motor (M2) rotate at an identical or nearly identical speed. Then, for the purpose of controlling the second electric motor (M2) at a rotation speed below a permit rotation speed, it may suffice for the first and second electric motors (M1) and (M2) to be driven in a direction to lower relevant rotation speeds while monitoring any one of an engine rotation speed, a first-motor rotation speed and a second-motor rotation speed. This allows such a control to be easily executed, thereby preventing the second electric motor from reaching a high speed rotation.

Abstract: A method of carrying out a shift with traction force interruption during hybrid operation in a parallel hybrid vehicle having an automated transmission. The method comprises the steps of maintaining the coupling between the internal combustion engine (1) and the electric machine (2), eliminating the load before disengaging the old gear, and synchronizing to the new gear by the operation of the electric machine (2).

Abstract: A control system for a drive unit of a vehicle, in which a power distribution mechanism is arranged on a route from a prime mover to a wheel, and a transmission is arranged on an output side of the power distribution mechanism. The control system includes a revolution frequency controller that restrains a variation in a revolution frequency of the prime mover by controlling a revolution frequency of the reaction force establishing device until a predetermined time elapses since a commencement of a shifting operation of the transmission. The control system is capable of restraining a variation in an output torque, in case of carrying out a shifting operation of a transmission arranged on an output side of a prime mover.

Abstract: A transmission system in a vehicle using a motor to transmit power assists acceleration by generating auxiliary engine power during acceleration in addition to gear changing by the motor. Where acceleration assistance is added, torque transition is conducted along a torque transmission route of dog clutch, second intermediate shaft, motor, first intermediate shaft, and gear position of first intermediate shaft before shifting so as to avoid the torque reduction in uncomfortable shocks and feelings to the driver due to torque reduction when shifting.

Abstract: When a reduction in a supply hydraulic pressure to a second shift portion is sensed, an engagement command of C0 clutch is generated so that a power split device (electrical differential portion) is brought into a locked state. In the locked state, a sun gear, a carrier rotated by an engine and a ring gear rotated by a second MG integrally rotate, whereby inertia is increased. Thus, high-speed rotation of a transmission member corresponding to an input shaft of the second shift portion can be prevented.

Abstract: A drive state shift control apparatus and method switches a hybrid drive (HEV) mode to an electric drive (EV) mode without engine stoppage shock or eliminates gearshifting shock in an electric vehicle. In response to a decrease in accelerator opening APO, a request for fourth-to-fifth upshift is issued, then request for HEV-to-EV mode shift is issued. At the time of the upshift, a direct clutch D/C is disengaged. At a first time interval after the mode shift is issued, a first clutch is disengaged. At a second time interval after the mode shift is issued, the engine begins to stop and the rotational speed of the motor-generator is controlled so that the speed falls to a predetermined rotational speed close to an after-gearshift rotational speed within a target shifting time interval. When the rotational speed reaches the predetermined rotational speed, a front brake Fr/B is engaged to perform a fourth-to-fifth upshift, and the torque of the motor is controlled so as to engage the one-way clutch smoothly.

Abstract: An automobile dual-power automatic transmission box supplies two different power sources to a wheel to drive an automobile and includes a first power source for rotating a first drive shaft, a second drive shaft rotated by the first drive shaft, a third drive shaft for rotating the wheel, a second power source, a clutch unit for driving the second power source to rotate the third drive shaft when the wheel speed is less than a predetermined value, or driving the second drive shaft for rotating the third drive shaft if the wheel speed is greater than the predetermined value, and a speed change unit for retarding the second drive shaft if the wheel speed reaches the predetermined value, and the clutch unit will drive the first power source to rotate the third drive shaft until the wheel speed approaches the rotating speed of the third drive shaft.

Abstract: A shiftable clutch device for disconnecting a first drive machine from a drive train and connecting it thereto, including a control device that can be actuated by a pressure medium, is characterized according to the invention in that the shiftable clutch device includes two partial clutches, a first partial clutch forming a main clutch and a second partial clutch forming a drag clutch, which are disposed and configured such that each is adapted to produce a drag torque in an end position of the control device, a first opening end position characterized by an open state of the main clutch and a second closing end position characterized by a closed state of the main clutch.

Abstract: A vehicle includes a motor/generator, a starter motor, a disconnect clutch disposed between the engine and the motor/generator, and at least one clutch disposed between the motor/generator and the vehicle drive wheels. When an engine start is requested, various parameters are controlled to ensure a smooth engine start wherein driveline torque disturbances are minimized. The starter motor is used to crank the engine at the lowest engine speeds when the engine-required torque is the highest. This reduces the amount of torque necessary to be supplied from the motor/generator, and further helps to reduce torque disturbances in the driveline. If the motor/generator is producing torque to propel the vehicle at the time the engine start is requested, a launch clutch or one or more transmission clutches can be controlled to provide slip between the motor/generator and the vehicle drive wheels to further reduce torque disturbances in the driveline.

Abstract: A high-efficiency vehicular transmission is provided. The transmission includes a transmission housing, a set of torque delivery elements which include first and second elements supported for rotation within the housing and an electric motor for changing angular velocity of at least one of the elements in response to an electrical signal during a shift to obtain a desired transmission ratio. At least one non-friction controllable coupling assembly has a coupling state for coupling the first element to either the second element or the housing and an uncoupling state for uncoupling the first element from either the second element or the housing, respectively. The at least one coupling assembly is non-hydraulically controlled to change state to maintain the desired transmission ratio.

Abstract: A control apparatus for a hybrid vehicle power transmitting system including a switching portion operable to switch a power transmitting path between a power transmitting state and a power cut-off state in response to an operation of a shift lever, the control apparatus including (a) an operating-state estimating portion configured to estimate an operating speed of an electric motor which constitutes a part of the power transmitting path or a rotating speed of a coupling element of the coupling portion, which speed is established after switching of the power transmitting path from one of the power transmitting and cut-off states to the other, and (b) a switching restricting portion configured to restrict a switching operation to switch the power transmitting path between the two states, when the estimated operating or rotating speed of the electric motor or coupling device is higher than a predetermined upper limit.

Abstract: A vehicle-starting-engine-torque restricting device is provided to restrict engine torque upon starting of a vehicle with an engine used as a vehicle drive power source, so that a required output of a first electric motor which generates a reaction force corresponding to the engine torque can be made smaller than when the engine torque is not restricted. Namely, the vehicle-starting-engine-torque restricting device eliminates a need of increasing the maximum output of the first electric motor to generate the reaction force corresponding to the engine torque, making it possible to reduce the required size of the first electric motor.

Abstract: A construction machine comprises an electric motor/generator coupled to an electricity accumulator, an engine, a transmission coupled to drive wheels, an epicyclic gearing for coupling an output shaft of the electric motor/generator, an output shaft of the engine, and an input shaft of the transmission, the engine torque and/or the generator torque being transmitted to drive wheels, a clutch for directly coupling two among the output shaft of the electric motor/generator, the output shaft of the engine, and the input shaft of the transmission, and a controller configured to, under a condition in which the clutch is in an off-state, control engine speed based on the degree to which the accelerator is open and on the amount of electricity in the electricity accumulator, to control shifting of the transmission gear position based on the accelerator opening degree, operational state of the generator, and the electricity amount motor/generator.

Abstract: A power transmission apparatus disposed includes: a motor for driving wheels, and transforms kinetic energy at the driving path to electrical energy; a normal close type clutch that includes an input and an output and is selectively set in an engaging state and a released state, wherein the clutch is normally set in the engaging state by a biasing member and is set in the released state when hydraulic pressure is applied; a hydraulic-pressure feeding device for supplying the adjusted hydraulic pressure to the clutch; and a control device for controlling the feeding device. When changing the clutch from the engaged state to the released state, if the difference between rotation numbers of the input and the output becomes equal to or larger than the predetermined value, the control device controls the feeding device to bring the clutch to a state just before the engaged state.

Abstract: A hybrid drive device includes a fluid clutch including an inputting element to which an engine torque outputted from an engine is inputted and an outputting element connected to an input shaft of a transmission to integrally rotate therewith for outputting the torque to the input shaft, the fluid clutch transmitting the torque between the inputting element and the outputting element via a fluid either with or without incrementing the torque, and a motor generator connected to the input shaft for outputting a motor torque to the input shaft to drive the transmission.

Abstract: A vehicle comprises a drive sub-system having an engine and a first motor and a generator sub-system having a transmission and a second motor. The transmission for the vehicle is driven with the first motor, the second motor and the engine individually and in combination such that the vehicle may selectively operate in a serial hybrid mode and a parallel hybrid mode.

Abstract: A vehicle has an internal combustion engine (ICE) and a electric traction motor (ETM) coupled by a standard transmission through a differential to drive traction wheels. A control system receives sensor signals including speed sensors, a load sensor, and an incline sensors. The control system processes the speed signals to generate indicator signals corresponding to speed of the ETM, the vehicle speed, the shifting gears and the speed of the transmission output shaft. One or more displays present indications of when the speed of a shifting gear corresponding to the speed of the ETM matches the speed of the vehicle thus the speed of the transmission output shaft. An operator may shift, without clutching, from neutral and to a next shifting gear when there is an indication that the speed of the next shifting gear matches the speed of a shifting collar coupled to the transmission output shaft.

Abstract: A method for ascertaining learned values for controlling an internal combustion engine, a second drive unit, e.g., an electric motor, drags the internal combustion engine in a specific operating state, and the learned values are ascertained in this operating state.

Abstract: A split serial-parallel hybrid dual-power drive system, comprised of two or more than two separation drive systems allowing independent operation to respectively drive the load, or all loads driven individually are incorporated in a common frame to drive land, surface, underwater transportation means or aircraft, industrial machines and equipment or any other load drive by rotational kinetic energy.

Abstract: A split serial-parallel hybrid dual-power drive system, comprised of two or more than two separation drive systems allowing independent operation to respectively drive the load, or all loads driven individually are incorporated in a common frame to drive land, surface, underwater transportation means or aircraft, industrial machines and equipment or any other load drive by rotational kinetic energy.

Abstract: A split serial-parallel hybrid dual-power drive system, comprised of two or more than two separation drive systems allowing independent operation to respectively drive the load, or all loads driven individually are incorporated in a common frame to drive land, surface, underwater transportation means or aircraft, industrial machines and equipment or any other load drive by rotational kinetic energy.

Abstract: A hybrid transmission is provided that is operatively connectable to an engine. The transmission has an electric motor and a clutch, which may be a brake-type clutch or a rotating-type clutch, depending on the embodiment, integrated within the transmission. Absent the electric motor and the clutch, and with the addition of a torque converter and torque converter lock-up clutch, the transmission would be a non-hybrid, operable automatic transmission. The transmission is operable to provide an electric-only operating ode, an engine-only operating mode, an electrically-variable operating mode and a parallel hybrid operating mode.

Abstract: A control apparatus for a vehicular drive system including an electrically controlled differential portion having a differential mechanism, and an electric motor which is operatively connected to the differential mechanism and an operating state of which is controlled to control a differential state between input and output shaft speeds, and a transmission portion constituting a part of a power transmitting path between the differential portion and a vehicle drive wheel, the control apparatus including a differential-state switching portion for switching the differential portion between differential-state and non-differential states, a shifting control portion for controlling a shifting action of the transmission portion, and a learning control portion for effecting learning compensation of a control amount of a control element to be controlled during the shifting action, wherein the learning control portion includes a differential-state learning control portion operable to implement the learning compensation

Abstract: A vehicle drive apparatus is disclosed having a differential mechanism and an electric motor provided in the differential mechanism for miniaturizing the drive apparatus or improving fuel consumption while suppressing the occurrence of shifting shocks. A switching clutch C0 or switching brake B0 is provided for placing a shifting mechanism 10 in a continuously variable shifting state and a step variable shifting state, enabling the drive apparatus to have combined advantages including a fuel economy improving effect of a transmission, enabled to electrically change a speed ratio, and a high transmitting efficiency of a gear type transmitting device enabled to mechanically transmit drive power.

Abstract: A vehicle comprises a plurality of motors operatively connected with one another. The vehicle is powered with the plurality of motors individually and in combination with one another to primarily operate each of the plurality of motors within a predetermine efficiency range.

Abstract: An apparatus and method are provided to execute synchronous shifting in a powertrain system having multiple torque-generative devices each operable to independently supply motive torque to the transmission device. The exemplary transmission device comprises a two-mode, compound-split, hybrid electro-mechanical transmission. Operation includes operating in an initial fixed gear ratio, operating the transmission in a mode operation, and, operating the transmission in a final fixed gear ratio. The control system reduces reactive torque of a clutch activating the initial gear, and deactivates the first torque-transfer device when the reactive torque is less than a predetermined value. It determines that speed of an input shaft to the transmission is substantially synchronized with a rotational speed of the second torque-transfer device, and actuates the second torque-transfer device.

Abstract: A method of operating a drive train having a hybrid drive that comprises an internal combustion engine and an electric machine, a clutch connected between the combustion engine and electric machine, a transmission connected between the electric machine and an output drive, and a start-up element connected between the electric machine and the output drive. The method for starting-up the drive train, when the clutch connected between the combustion engine and the electric machine and the start-up element are both disengaged, and the electric machine is stopped and short-circuited. The method comprising the steps of accelerating the internal combustion engine to a rotational speed which depends on a short circuit torque of the electric machine that must be overcome; engaging the clutch connected between the combustion engine and electric machine; and bringing the combustion engine to a start-up speed depending on the driver's request; and engaging the start-up element.

Abstract: The invention relates to a method for controlling a creep mode of a vehicle comprising a hybrid drive (1), a drive train (2) which essentially comprises an internal combustion engine (3), an electric machine (5), a gear-shift element (4) arranged between the internal combustion engine (3) and the electric machine (5), a transmission (7) and a power take-off (26). The aim of the invention is to allow an efficient creep mode which is substantially temporally unlimited and reliable and wherein an electrical energy storage device (14) is used as little as possible. The method according to the invention is characterized in that primarily the gear-shift element (4) is used when the internal combustion engine (3) is running and secondarily, depending on a monitoring of defined operation parameters of the gear-shift element (4) and/or of variables relevant for the creep mode, the electric machine (5) is used to implement the creep mode.

Abstract: A method is proposed for controlling and/or regulating a starting process in a hybrid drive arrangement of a vehicle, in which at least one control unit (8) is used by means of which a combustion engine (1), at least one electric machine (3), a transmission (4) and a first clutch (2) arranged between the combustion engine (1) and the electric machine (3) and a second clutch (5) arranged between the electric machine (3) and the transmission (4) are controlled so as to carry out a starting process, such that to change from electric starting to at least partially combustion-engine-powered staring the clutch torque that can be transferred is adjusted to the nominal driving torque so that the torque of the electric machine (3), the torque of the combustion engine (1) and/or the clutch torque of the first clutch (2) are matched.

Abstract: The invention relates to a method and a device for controlling a creep mode of a vehicle having a hybrid drive system (1, 1?), having a parallel hybrid drivetrain (2, 2?) comprising an internal combustion engine (3), at least one electrical machine (5), a first switching element (4) designed as a frictional element and disposed between the internal combustion engine (3) and the electrical machine (5), by means of which the internal combustion engine (3) can be connected to the electrical machine (5), a gearbox (7), an output (26), and at least one second switching element (6) designed as a frictional element and disposed between the electrical machine (5) and the output (26), by means of which the electrical machine (5) can be operationally connected to the output (26).

Abstract: A powertrain includes a prime mover, a transmission, an input shaft adapted to transmit torque between the prime mover and the transmission, an output shaft adapted to transmit torque between the transmission and a driveline, and a master clutch between the prime mover and the input shaft, the clutch being movable between a disengaged position and an engaged position in which the clutch is not and is adapted to transmit torque between the prime mover and the input shaft, respectively. An electric motor is arranged for torque transmission with at least one of the input shaft and the output shaft, and a controller is provided for controlling the electric motor to rotate the input shaft at a rotational speed within an operating range of the prime mover when the clutch is moved from the disengaged to the engaged position.

Abstract: A hybrid vehicle control system for cutting off fuel to an internal combustion engine of hybrid vehicle while providing smooth transitions from a hybrid drive mode to an electric drive mode is provided. The hybrid vehicle control system includes an integrated controller configured to receive inputs corresponding to vehicle speed and an indicated driving force, and to select an appropriate mode transition pattern from a group of mode transition patters according to the change in indicated driving force.

Abstract: The present invention provides a method for reducing backlash vibrations in a hybrid electric vehicle, in which the backlash vibrations generated between a motor and a driving wheel can be easily reduced by slipping a clutch in an automatic transmission when the direction of a motor driving torque is changed while the hybrid electric vehicle is running in electric vehicle (EV) mode.

Abstract: A control apparatus for a hybrid vehicle for controlling and limiting the transmission of power from an engine to the driving wheels during start-up of the engine to produce a hybrid running mode where the vehicle is powered by both the engine and a motor-generator. During start-up of the engine, a first frictional element changing its state before and after a shift of the transmission is allowed to slip, and a second frictional element is allowed to slip. The element that is allowed to slip is switched from one to the other.

Abstract: A hybrid vehicle control device is provided with an engine stop control section and a fuel injection control section. The engine stop control section is configured to issue an engine speed reduction command to reduce an engine speed of an engine during an engine stopping operation occurring in response to establishment of an engine stop condition by using an electric motor and slip engaging a drive-wheel side clutch disposed between the electric motor and a drive wheel such that the drive-wheel side clutch transmits rotational torque between the electric motor and the drive wheel. The fuel injection control section is configured to issue a fuel injection command to continue fuel injection during the engine stopping operation until the engine speed decreases below a prescribed engine speed whereupon the fuel injection is stopped.

Abstract: A method for operating a drivetrain of a motor vehicle having in the force flow direction and in the following order an internal combustion engine, a clutch, an electric motor, a transmission and an axle gearset, or an internal combustion engine, a clutch, an electric motor, a transmission input shaft, a transmission and an axle gearset. The electric motor is used for pre-lubricating and warming the transmission such that, with the vehicle clutch disengaged, the lubricant pump of the transmission is driven by the electric motor so bearings are supplied with lubricant before the engine is started, and the heat, produced by splashing the lubricant, additionally warms the transmission.

Abstract: A hybrid-vehicle engine start controlling apparatus includes an engine, a motor connected to a vehicle driving shaft, a first engaging element provided between the engine and the motor for connecting and disconnecting the engine and the motor and engine start control means. The engine start controlling means is configured to start the engine by increasing a driving torque of the motor and increasing a transmission torque capacity of the first engaging element so as to increase a rotation speed of the engine by the driving torque of the motor in a state in which the engine is stopped and the first engaging element is released. The engine start controlling means includes a first engaging phase for increasing the transmission torque capacity of the first engaging element at a first velocity, and a second engaging phase for changing the transmission torque capacity at a second velocity lower than the first velocity.

Abstract: In a control unit and a method for operating a hybrid drive arrangement (1) with an internal combustion engine (5), an electric drive (3) and a coupling device (20) that is arranged therebetween, when the internal combustion engine (5) and the electric drive (3) should be coupled together, the rotational speed of the internal combustion engine (5) is pilot-controlled to a target rotational speed level (N2) such that the drive shafts (4, 6) of the internal combustion engine (5) and the electric drive (3) run at least approximately synchronously. The pilot-control takes place by the throttle valve. Subsequently, the rotational speed of the internal combustion engine (5) is controlled in such a manner that the drive shafts (4, 6) of the internal combustion engine (5) and the electric drive (3) run essentially synchronously. Then, the drive shafts (4, 6) are joined by the coupling device (20).

Abstract: A multi-mode hybrid transmission including a selectable one-way clutch and first and second torque machines transitions to operating in a target continuously variable mode including applying a selectable one-way clutch and controlling input torque and motor torques of the first and second torque machines using a second kinematic relationship. A multi-step process is executed to transition the first clutch to a deactivated state, transition the second selectable one-way clutch to the applied state, and transition to using the second kinematic relationship to achieve a preferred output torque.

Abstract: The present invention provides a method which controls the hydraulic pressure of a clutch (an engine clutch) disposed between an engine and a drive motor, thus reducing gear shifting shock and vibration. The method comprises a slip preparation step of determining that gear shifting is required and reducing the hydraulic pressure of the clutch to a preset target hydraulic pressure from a point in time at which the gear shifting is required. The method further comprises a slip maintaining step of feedback-controlling the hydraulic pressure of the clutch such that a slip rate of the clutch is maintained constant after the hydraulic pressure of the clutch reaches the target hydraulic pressure; and a clutch lock-up completing step of increasing the hydraulic pressure of the clutch, from a point in time at which the gear shifting is completed, to a maximum hydraulic pressure for making a lock-up state of the clutch.

Abstract: A system for robust fault detection in an electrically variable, hydraulically controlled transmission includes independently monitoring hydraulic pressure within a hydraulic control circuit and electric machine rotation for detecting clutch state faults.

Abstract: A method for the operation of a hybrid drive system is provided. The hybrid drive system has a first drive machine, for example an internal combustion engine, and a second drive machine, such as an electric machine. The hybrid drive system can also have a first gearshift sub-transmission and a second gearshift sub-transmission. The first gearshift sub-transmission can have a first input shaft that can be coupled to an output shaft using a first group of shifting gearwheel pairs, and the first input shaft can be coupled to the first drive machine. The second gearshift sub-transmission can have a second input shaft that is coupled to the output shaft using a second group of shifting gearwheel pairs, and the second input shaft can be connected with the second drive machine.

Abstract: A control apparatus and method of controlling a hybrid vehicle are taught herein. The vehicle selectively switches between an EV mode wherein the vehicle travels by only a driving force produced by the motor/generator when an accelerator opening is less than or equal to an engine-stop line or a HEV mode wherein the vehicle travels by at least a driving force produced by the engine the accelerator opening exceeds the engine-stop line. A transition from the HEV mode to the EV mode is executed when the accelerator opening becomes less than or equal to the engine-stop line during the HEV mode and a given delay time has expired. The delay time is set to a shorter time as an accelerator return speed decreases.