Control apparatus for hybrid vehicle

A control apparatus for a hybrid vehicle to permit charging of an electric-energy storage device with an electric energy supplied from an external electric power source provided outside said hybrid vehicle, while said hybrid vehicle is held stationary; and to operate an engine for operating a lubricant supply device to supply a predetermined amount of the lubricant, during charging of said electric-energy storage device by said external electric power source, irrespective of whether a count of said motor running counter has reached a predetermined upper limit, and to reset said motor running counter.

TECHNICAL FIELD

The present invention relates to a control apparatus for a hybrid vehicle provided with an engine and an electric motor serving as a vehicle drive power source, and more particularly to a supply of a lubricant to a power transmitting system provided to transmit a vehicle drive force from the vehicle drive power source to drive wheels.

BACKGROUND ART

There is known a control apparatus for a hybrid vehicle provided with an engine and electric motors serving as a vehicle drive power source, a power transmitting system for transmitting a drive force of the vehicle drive power source to a drive wheel, and an electric-energy storage device for supplying a stored electric energy to the electric motor. Patent documents 1, 2 and 3 disclose examples of such a hybrid vehicle control apparatus. The hybrid vehicles disclosed in these documents are provided with a power transmitting system including a planetary gear set which has a first element connected to the engine, a second element connected to a first electric motor, and a third element connected to an output rotary member and a second electric motor. The planetary gear set is configured to distribute an output of the engine to the first electric motor and the output rotary member. These hybrid vehicles are able to run in a motor drive mode in which only the second electric motor is operated as the vehicle drive power source, while the engine is held at rest. Generally, the hybrid vehicles as described above are provided with a mechanically operated oil pump operatively connected to the engine and constructed to deliver a working oil according to an operation of the engine, so that the oil pump operated while the engine is operated supplies a lubricant to the above-described planetary gear set and other parts (such as gears and bearings) of the power transmitting system.

The oil pump connected to the engine is not operated in the motor drive mode in which the engine is held at rest, so that the lubricant is not supplied as needed to the predetermined parts of the above-described power transmitting system in the motor drive mode, giving rise to a risk of deterioration of durability of the predetermined parts (such as the gears and other rotating members) of the power transmitting system, due to metal contacts of the parts, etc. In particular, a so-called “plug-in hybrid vehicle” the electric-energy storage device of which is chargeable with an electric energy supplied from an external electric power13ource for the hybrid vehicle such as a domestic power source is considered to be able to have comparatively long running time and distance in the motor drive mode, and consequently has a high risk of the above-described problem caused by the long running in the motor drive mode in which the lubricant is not supplied with the engine held at rest. To deal with this problem, the above-described Patent document 1 proposes a forced operation of the engine (engine motoring) by the first electric motor to operate the oil pump to supply the lubricant to predetermined parts of the engine, when a time period of resting of the engine exceeds a predetermined upper limit.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Object Achieved by the Invention

However, the forced operation of the engine by the first electric motor for lubrication causes deterioration of the charged state (reduction of the stored electric energy amount) of the electric-energy storage device used to supply the electric energy to the second electric motor, for example, causing a risk of reduction of the running distance and time in the motor drive mode, and resulting in an earlier operation of the engine, leading to reduction of energy efficiency of the vehicle, for instance, reduction of fuel economy of the vehicle. It is also noted that the forced operation of the engine in the motor drive mode means an operation of the engine irrespective of the vehicle running by the second electric motor, giving rise to a risk of giving the user of the vehicle a sense of anxiety. Thus, the forced operation of the engine may reduce advantages of the plug-in hybrid vehicle in the motor drive mode. It is noted here that the problem described above is not recognized in the art.

The present invention was made in view of the background art described above. It is therefore an object of the present invention to provide a control apparatus for a hybrid vehicle, which permits an improved fuel economy of the hybrid vehicle while permitting an adequate supply of a lubricant from a lubricant supply device to at least a portion of a power transmitting system.

Means for Achieving the Object

The object indicated above is achieved according to the present invention, which provides a control apparatus for (a) a hybrid vehicle provided with an engine and an electric motor serving as a vehicle drive power source, a power transmitting system for transmitting a drive force of the vehicle drive power source to a drive wheel, an electric-energy storage device for storing an electric energy to be supplied to the above-described electric motor, and a lubricant supply device which is operatively connected to the above-described engine and operated by a rotary motion of the engine to supply a lubricant to at least a portion of the above-described power transmitting system, (b) characterized in that the control apparatus is configured: to permit running of the hybrid vehicle in a motor drive mode in which only the above-described electric motor is operated as the vehicle drive power source, with the electric energy supplied from the electric-energy storage device while the rotary motion of the above-described engine is stopped; (c) to operate a motor running counter in the above-described motor drive mode, to count continuation of the motor drive mode without the rotary motion of the above-described engine, and to operate the above-described engine for operating the above-described lubricant supply device to supply a predetermined amount of the lubricant, when a count of the above-described motor running counter has reached a predetermined upper limit; (d) to permit charging of the above-described electric-energy storage device with an electric energy supplied from an external electric power source provided outside the above-described hybrid vehicle, while the hybrid vehicle is held stationary; (e) and to operate the above-described engine for operating the above-described lubricant supply device to supply the above-described predetermined amount of the lubricant, during charging of the above-described electric-energy storage device by the above-described external electric power source, irrespective of whether the count of the above-described motor running counter has reached the above-described predetermined upper limit, and to reset the above-described motor running counter.

Advantages of the Invention

The hybrid vehicle control apparatus constructed according to the present invention described above is configured to forcibly operate the above-described engine for operating the above-described lubricant supply device to supply the above-described predetermined amount of the lubricant during the charging of the above-described electric-energy storage device by the above-described external electric power source, and to reset the above-described motor running counter, making it possible to reduce the frequency of operations of the engine which take place to operate the above-described lubricant supply device to supply the predetermined amount of the lubricant, each time the count of the motor running counter has reached the predetermined upper limit in the motor drive mode. Accordingly, the reduction of the stored electric energy amount of the electric-energy storage device can be minimized, permitting continuation of the motor drive mode for a longer length of time, resulting in prolonged motor running time and distance, for instance, and a consequent improvement of the fuel economy. Thus, it is possible to improve the fuel economy while permitting an adequate supply of the lubricant by the lubricant supply device to at least a portion of the power transmitting system. Additionally, it is possible to reduce the risk of giving the vehicle user a sense of anxiety which would be caused by the operation of the engine in the motor drive mode, which takes place irrespective of the vehicle running in the motor drive mode. Thus, the advantage of the motor drive mode of the plug-in hybrid vehicle is improved.

It is preferable that the hybrid vehicle is provided with a rotary drive device operatively connected to the above-described engine, and that the above-described engine is operated by the above-described rotary drive device. In this case, a forced operation of the engine without its starting or complete combustion can be adequately performed by operating the rotary drive device.

Preferably, the above-described power transmitting system is an electrically controlled differential portion which has a differential mechanism operatively connected to the above-described engine, and a differential electric motor operatively connected to the differential mechanism, and in which a differential state of the differential mechanism is controlled by controlling an operating state of the differential electric motor. In this case, the electric motor serving as the above-described vehicle drive power source is a vehicle driving electric motor operatively connected to the above-described drive wheel, and the differential electric motor is operated to operate the above-described engine. Thus, a forced operation of the engine without its starting or complete combustion can be adequately performed by operating the differential electric motor. In addition, the hybrid vehicle can be run in the motor drive mode adequately by using the vehicle driving electric motor.

Preferably, the above-described motor running counter is a motor running distance counter configured to count a distance of continuous running of the hybrid vehicle in the motor drive mode without an operation of the above-described engine. In this case, the lubricant supply device is operated to supply the lubricant at an adequate point of time in the motor drive mode.

Preferably, the above-described motor running counter is a motor running time counter configured to count a length of time of continuous running of the hybrid vehicle in the motor drive mode without an operation of the above-described engine. In this case, the lubricant supply device is operated to supply the lubricant at an adequate point of time in the motor drive mode.

Preferably, the above-described predetermined amount of the lubricant is supplied on the basis of the time of operation and the speed of operation of the above-described engine, and at least one of the time of operation and the speed of the operation is increased with a decrease of a temperature of the lubricant, so that the lubricant can be supplied adequately by the predetermined amount, irrespective of the temperature of the lubricant.

Preferably, a portion of the above-described power transmitting system is constituted by a differential mechanism having a first element connected to the above-described engine, a second element connected to a first electric motor, and a third element connected to an output rotary member and a second electric motor provided as the above-described electric motor. In this case, an output of the engine is distributed to the first electric motor and the above-described output rotary member. In the power transmitting system thus constructed, the differential mechanism functions as a transmission and permits the vehicle running in the motor drive mode, without a supply of a working oil (lubricant) for its shifting operation.

The above-described differential mechanism is preferably constituted by a planetary gear set having a carrier as the above-described first element, a sun gear as the above-described second element, and a ring gear as the above-described third element. In this case, the differential mechanism has a reduced axial dimension, and is simplified in construction being constituted by the single planetary gear set.

The above-described planetary gear set is preferably a planetary gear set of a single pinion type. In this case, the differential mechanism has a reduced axial dimension, and is simplified in construction being constituted by the single planetary gear set of the single pinion type.

The above-described second electric motor is preferably operatively connected directly to the above-described third element, or indirectly to the third element through a speed reducing device, for example, so that a drive force of the second electric motor is transmitted to the above-described output rotary member through the speed reducing device. In the latter case, the second electric motor can be small-sized.

MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described in detail by reference to the drawings.

Embodiment

FIG. 1is the schematic view for explaining a power transmitting system in the form of a transmission mechanism10of a hybrid vehicle8(shown inFIG. 5) to which the present invention is applicable. As shown inFIG. 1, the transmission mechanism10includes: a damper16which is operatively connected to an output shaft (e.g., crankshaft15) of an internal combustion engine in the form of an engine14such as a gasoline engine or a diesel engine serving as a vehicle drive power source, and which is provided to absorb a pulsation due to a variation of a torque of the engine14; an input shaft18rotated by the engine14through the damper16; a first electric motor M1; a planetary gear set20functioning as a power distributing mechanism; and a second electric motor M2. The damper16, input shaft18, first electric motor M1, planetary gear set20and second electric motor M2are disposed in the order of description from the side of the engine14, within a transaxial (T/A) casing12(hereinafter referred to as “casing12”) serving as a stationary member attached to a body of the vehicle.

This transmission mechanism10is suitably used for a transversal FF vehicle (front-engine, front-drive vehicle), for example, and is arranged to transmit a drive force of the engine14from an output rotary member of the transmission mechanism10in the form of an output gear24serving as one of a counter gear pair32, to a pair of drive wheels40through the counter gear pair32, a final gear pair34, a differential gear device (final speed-reduction gear device)36, a pair of axles38, etc., which also constitute respective parts of the power transmitting system (as shown inFIG. 5).

The input shaft18is rotatably supported at its opposite ends by ball bearings26and28, and is connected at one of its opposite end portions to the engine14through a dumper16so that the input shaft18is rotated by the engine14. To the other end portion of the input shaft18, there is connected a lubricant supply device in the form of an oil pump30so that the oil pump30is operated by a rotary motion of the input shaft18, to supply a lubricant to predetermined parts of the transmission mechanism10, such as the planetary gear set20, ball bearings26,28, counter gear pair32and final gear pair34.

The planetary gear set20is a planetary gear set of a single pinion type having a predetermined gear ratio ρ0, and rotary elements (elements) consisting of: a sun gear S; a pinion gear P; a carrier CA supporting the pinion gear P such that the pinion gear P is rotatable about its axis and about the axis of the planetary gear set20; and a ring gear R meshing with the sun gear S through the pinion gear P. Where the numbers of teeth of the sun gear S and the ring gear R are represented by ZS and ZR, respectively, the above-indicated gear ratio ρ0is represented by ZS/ZR. This planetary gear set20is a mechanism provided to mechanically distribute the output of the engine14received by the input shaft18, to the first electric motor M1and the output gear24. Namely, the planetary gear set20is constructed such that the carrier CA is connected to the input shaft18, that is, to the engine14, and the sun gear S is connected to the first electric motor M1, while the ring gear R is connected to the output gear24. The thus constructed planetary gear set20is placed in a differential state in which the three elements consisting of the sun gear S, carrier CA and ring gear R are rotatable relative to each other, so as to perform a differential function, so that the output of the engine14is distributed to the first electric motor M1and the output gear24, whereby a portion of the output of the engine14is used to drive the first electric motor M1to generate an electric energy which is stored or used to drive the second electric motor M2. Accordingly, the transmission mechanism10is placed in a continuously-variable shifting state (electrically established CVT state), in which the transmission mechanism10is operated as an electrically controlled continuously variable transmission in which the rotating speed of the output gear24is continuously variable, irrespective of the operating speed of the engine14.

Thus, the transmission mechanism10includes a differential mechanism in the form of the planetary gear set20operatively connected to the engine14, and a differential electric motor in the form of the firs electric motor M1operatively connected to the planetary gear set20, and serves as an electrically controlled differential portion having the planetary gear set20a differential state of which is controlled by controlling an operating state of the first electric motor M1. The transmission mechanism10further includes the second electric motor M2, which is operatively connected to the output gear24so as to be rotated integrally with the output gear24, and which functions as a vehicle drive power source. Namely, this second electric motor M2serves as a vehicle drive electric motor operatively connected to the drive wheels40. Each of the first and second electric motors M1and M2provided in this embodiment is a so-called motor/generator having also a function of an electric generator. The first electric motor M1has at least a function of the electric generator for generating a reaction force, while the second electric motor M2has at least a function of the electric motor operating as a vehicle drive power source for producing a vehicle drive force. The transmission mechanism10thus constructed serves as the power transmitting system the planetary gear set20of which functions as a transmission and permits the vehicle running in a motor drive mode, without a supply of a working oil (lubricant) to the planetary gear set for its shifting operation.

FIG. 2is the collinear chart indicating, by straight lines, a relationship among the rotating speeds of the rotary elements of the transmission mechanism10. The collinear chart ofFIG. 2is a rectangular two-dimensional coordinate system in which the gear ratios ρ of the planetary gear set20is taken along the horizontal axis, while the relative rotating speeds of the rotary elements are taken along the vertical axis. A horizontal line X1indicates the rotating speed of 0, while a horizontal line X2indicates the rotating speed of 1.0, that is, an operating speed NEof the engine14connected operatively to the input shaft18.

Three vertical lines Y1, Y2and Y3respectively corresponding to the three elements of the planetary gear set20of the transmission mechanism10respectively represent the relative rotating speeds of a second rotary element (second element) RE2in the form of the sun gear S, a first rotary element (first element) RE1in the form of the carrier CA, and a third rotary element (third element) RE3in the form of the ring gear R. The distances between the adjacent ones of the vertical lines Y1, Y2and Y3are determined by the gear ratio ρ of the planetary gear set20. Described in detail, the distance between the vertical lines in the collinear chart representing the sun gear and carrier corresponds to “1”, while the distances between the carrier and ring gear correspond to the gear ratio ρ of the planetary gear set. That is, the transmission mechanism10is arranged such that the distance between the vertical lines Y1and Y2corresponds to “1”, while the distance between the vertical lines Y2and Y3corresponds to the gear ratio ρ.

Referring to the collinear chart ofFIG. 2, the transmission mechanism10in the present embodiment is arranged such that the first rotary element RE1(carrier CA) of the planetary gear set20is integrally fixed to the input shaft18, that is, to the engine14, and the second rotary element RE2is fixed to the first electric motor M1, while the third rotary element RE3(ring gear R) is fixed to the output gear24and the second electric motor M2, so that a rotary motion of the input shaft18is transmitted to the drive wheels40through the output gear24. A relationship between the rotating speeds of the sun gear S and the ring gear R is represented by an inclined straight line L0which passes a point of intersection between the lines Y2and X2. When the transmission mechanism10(planetary gear set20) is placed in the differential state in which the first rotary element RE1through the third rotary element RE3are rotatable relative to each other, for instance, the rotating speed of the ring gear R represented by a point of intersection between the straight line L0and the vertical line Y3is held substantially constant at a value determined by a running speed V of the vehicle. In this differential state, the rotating speed of the carrier CA, i.e., the rotating speed Ne of the engine, represented by a point of intersection between the straight line L0and the vertical line Y2is raised or lowered, when the rotating speed of the sun gear S represented by a point of intersection between the straight line L0and the vertical line Y1is raised or lowered by controlling an operating speed NM1of the first electric motor M1.

FIG. 3is the view indicating signals for controlling the transmission mechanism10of the present invention received by and signals generated from an electronic control device80. This electronic control device80is principally constituted by a so-called microcomputer which incorporates a CPU, a ROM, a RAM and an input/output interface. The electronic control device80is configured to process the signals according to programs stored in the ROM while utilizing a temporary data storage function of the RAM, to perform vehicle controls such as hybrid drive controls of the engine14, first electric motor M1and second electric motor M2.

The electronic control device80is arranged to receive from various sensors and switches shown inFIG. 3, various signals such as: a signal indicative of an engine water temperature THw; a signal indicative of a shift position PSHof a shift lever52(shown in FIG.4); a signal indicative of the rotating speed NEof the engine14; a signal indicative of an operating state of a switch provided to establish the motor drive mode (EV drive mode); a signal indicative of an operation of an air conditioner; a signal indicative of the vehicle running speed V corresponding to a rotating speed NOUTof the output gear24(output speed); a signal indicative of a temperature THOILof the lubricant; a signal indicative of an operation of a foot brake; a signal indicative of an operation amount ACCof an accelerator pedal corresponding to an operator's required output of the vehicle; a signal indicative of an opening angle θTHof an electronic throttle valve; a signal indicative of a longitudinal acceleration value G of the vehicle; a signal indicative of a rotating speed of each vehicle wheel; a signal indicative of the operating speed NM1of the first electric motor M1(hereinafter referred to as “first electric motor speed NM1”); a signal indicative of an operating speed NM2of the second electric motor M2(hereinafter referred to as “second electric motor speed NM2”); a signal indicative of a temperature THM1of the first electric motor M1(hereinafter referred to as “first electric motor temperature”); a signal indicative of a temperature THM2of the second electric motor M2(hereinafter referred to as “second electric motor temperature”); a signal indicative of a temperature THBATof a electric energy storage device56(shown inFIG. 5) (hereinafter referred to as “battery temperature”); a signal indicative of a charging or discharging current ICDof the electric-energy storage device56(hereinafter referred to as “charging/discharging current” or “input/output current”); a signal indicative of a voltage VBATof the electric-energy storage device56; a signal indicative of the charged state (stored electric energy amount) SOC of the electric-energy storage device56calculated on the basis of the above-described battery temperature THBAT, charging/discharging current ICDand voltage VBAT; and an output signal of a vehicle power switch operable by the vehicle user, which indicates a power on state (vehicle power ON or Ready-on state) or a power off state (vehicle power OFF or Ready-off state) of the vehicle.

The electronic control device80is further arranged to generate various control signals to be applied to an engine output control device58controlling an engine output (shown inFIG. 5), such as: a drive signal to drive a throttle actuator64for controlling the opening angle θTHof the electronic throttle valve62disposed in an intake pipe60of the engine14; a signal to control an amount of injection of a fuel by a fuel injecting device66into the intake pipe60or cylinders of the engine14; a signal to be applied to an ignition device68to control the ignition timing of the engine14; command signals to command the electric motors M1and M2to operate; a signal to operate an ABS actuator for anti-lock braking of the wheels; a signal to operate a shift-position indicator for indicating the selected shift position; a signal to operate the electric air conditioner; and a signal to operate an EV drive mode indicator for indicating the selection of the EV drive mode.

FIG. 4shows an example of a manually operable shifting device in the form of a shifting device50for selecting one of a plurality of shift positions PSH. The shifting device50includes a shift lever52, which is disposed laterally adjacent to the operator's seat, for example, and which is manually operated to select one of the plurality of shift positions PSH.

The shift lever52is manually operated to: a parking position P for placing the transmission mechanism10in a neutral state in which the power transmitting path is disconnected and in which the output gear24is locked; a reverse position R for driving the vehicle in the rearward direction; a neutral position N for placing the transmission mechanism10in the neutral state established by forcibly stopping the operations of the first and second electric motors M1and M2to zero the vehicle drive force at the output gear24, for example; an automatic forward-drive shifting position D in which the transmission mechanism10is placed in an automatic shifting state in which a speed ratio γ0is continuously variable over a predetermined range; and an engine braking position B in which a considerably large engine braking effect is obtained by a regenerative braking operation of the second electric motor M2while the accelerator pedal is placed in the non-operated position.

Of the shift positions PSHconsisting of the above-indicated positions P through B, the parking position P and the neutral position N are non-drive positions selected when the vehicle is not driven. These non-drive positions P, N are selected to switch the power transmitting path to a power cut-off state. The reverse-drive position R, and the automatic forward-drive position D are drive positions selected when the vehicle is driven. These drive positions R, D are selected to switch the power transmitting path to a power transmitting state.

The electric-energy storage device56shown inFIG. 5is a chargeable and dischargeable DC power source, which is constituted by a secondary battery of a nickel hydrogen or lithium ion type, for example. When the vehicle is accelerated, for instance, an electric energy (electric power) generated by the first electric motor M1operated to generate a reaction force with respect to the engine14is stored in the electric-energy storage device56through an inverter54. When the vehicle is decelerated with a regenerative braking operation of the second electric motor M2, on the other hand, an electric power generated by the second electric motor M2is stored in the electric-energy storage device56through the inverter54. When the vehicle is run in the motor drive mode by the second electric motor M2, the electric power stored in the electric-energy storage device56is supplied through the inverter54to the second electric motor M2.

While the hybrid vehicle8is held stationary, the electric-energy storage device56can be charged with an electric power supplied from an external electric power source such as a commercial electric power source70provided outside the hybrid vehicle8. For example, the hybrid vehicle8is provided with a connector72for connection with the commercial electric power source70to receive the electric power therefrom. When this connector72is connected to a connector74provided on the side of the commercial electric power source70, the electric-energy storage device56is charged with the electric power supplied from the commercial electric power source70through the connector72and inverter54, by voltage application from the commercial electric power source70to the connector72.

FIG. 5is the functional block diagram for explaining major control functions of the electronic control device80. A hybrid control portion in the form of hybrid control means82shown inFIG. 5is configured to control the engine14to be operated in an operating range of high efficiency, and to control the speed ratio γ0of the transmission mechanism10operating as the electrically controlled continuously variable transmission, by optimizing a proportion of drive forces generated by the engine14and the second electric motor M2, and a reaction force generated by the first electric motor M1during its operation as the electric generator. For instance, the hybrid control means82calculates a target (required) output of the vehicle at the present running speed V of the vehicle, on the basis of an operation amount ACCof the accelerator pedal used as an operator's required vehicle output, and the vehicle running speed V, and calculate a target total vehicle output on the basis of the calculated target output of the vehicle and a required amount of charging of the electric-energy storage device. Then, the hybrid control means82calculates a target engine output to obtain the calculated target total vehicle output, while taking account of a power transmission loss, a load acting on various optional devices of the vehicle, an assisting torque to be generated by the second electric motor M2, etc. The hybrid control means82controls the engine14and the amount of generation of the electric energy by the first electric motor M1, such that the rotating speed NEand torque TEof the engine14are controlled to obtain the calculated target engine output.

Namely, the hybrid control means82determines a target value of the speed ratio y0of the transmission mechanism10so that the engine14is operated such that an operating point of the engine14follows a stored well known highest-fuel-economy curve (fuel-economy map or relation), which is obtained by experimentation so as to satisfy both of the desired operating efficiency and the highest fuel economy of the engine14in the continuously-variable shifting state, and which is defined in a two-dimensional coordinate system defined by an axis of the engine rotating speed NEand an axis of the output torque TEof the engine14(engine torque TE). For instance, the hybrid control means82determines the target value of speed ratio γ0of the transmission mechanism10such that the engine torque TEand engine rotating speed NEare controlled to obtain the target engine output (target total vehicle output: required vehicle drive force), and controls the speed ratio y0continuously within a predetermined range, to obtain the determined target value.

At the same time, the hybrid control means82controls an inverter54such that the electric energy generated by the first electric motor M1is supplied to the electric-energy storage device56and the second electric motor M2through the inverter54. That is, a major portion of the drive force produced by the engine14is mechanically transmitted to the output gear24, while the remaining portion of the drive force is consumed by the first electric motor M1to convert this portion into the electric energy, which is supplied through the inverter54to the second electric motor M2, so that the second electric motor M2is operated with the supplied electric energy, to produce a mechanical energy to be transmitted to the output gear24. Thus, the devices relating to an operation from the generation of the electric energy to the consumption of the electric energy by the second electric motor M2constitute an electric path through which the electric energy generated by conversion of a portion of the drive force of the engine14is converted into a mechanical energy.

The hybrid control means82is further configured to hold the engine speed NEsubstantially constant or at a desired value owing to an electric CVT function of the transmission mechanism10, by controlling the first electric motor speed NM1, for example, irrespective of whether the vehicle is stationary or running. That is, the hybrid control means82controls the first electric motor M1so as to operate the engine14, such that the first electric motor M1operatively connected to the input shaft18(that is, the output shaft of the engine14) through the planetary gear set20functions as a drive device operable to transmit a vehicle drive force to the input shaft18. For example, the hybrid control means82is configured to raise the engine speed NEduring running of the vehicle, by raising the first electric motor speed NM1while the output speed NOUTdetermined by the vehicle speed V (rotating speed of the drive wheels40) is held substantially constant.

The hybrid control means82includes engine output control means functioning to command an engine output control device58to control the engine14, so as to provide a required output, by controlling a throttle actuator64to open and close an electronic throttle valve62, and controlling an amount and time of fuel injection by a fuel injection device66, and/or the timing of ignition by an ignition device68such as ignitor, alone or in combination. For instance, the hybrid control means82is basically configured to control the throttle actuator60on the basis of the accelerator pedal operation amount ACCand according to a predetermined stored relationship (not shown) between the accelerator pedal operation amount ACCand the throttle vale opening angle θTH, such that the opening angle θTHincreases with an increase of the accelerator pedal operation amount ACC. According to a command from the hybrid control means82, the engine output control device58controls the engine torque by controlling the throttle actuator64to open and close the electronic throttle valve62, and controlling the fuel ignition by the fuel injection device66, and the ignition timing of the ignition device68.

The hybrid control means82is further configured to establish a motor drive mode (EV drive mode) in which only the second electric motor M2is operated as a vehicle drive power source, with an electric energy supplied from the electric-energy storage device56, while the engine14is held at rest. For example, the EV drive mode is generally established by the hybrid control means82, when a vehicle output torque TOUTis in a comparatively low range in which the engine efficiency is comparatively low, relative to when the vehicle output torque is in high range, namely, when the engine torque TEis in a comparatively low range, or when the vehicle speed V is in a comparatively low range, that is, when the vehicle load is comparatively low.

For preventing a dragging of the engine14in its non-operated state and improving the fuel economy in the EV drive mode, the hybrid control means82is configured to hold the engine speed NEat zero or substantially zero, as needed, owing to the electric CVT function (differential function) of the transmission mechanism10, by placing the first electric motor M1in its non-load or freely rotatable state, for example. Namely, the hybrid control means82not only holds the engine14in its non-operated state, but also prevents a rotary motion of the engine14, in the EV drive mode.

The hybrid control means82also includes engine start control means functioning to start the engine14while the vehicle is stationary or running in the EV drive mode. For instance, the hybrid control means82commands the first electric motor M1to raise the first electric motor speed NM1, i.e., to operate as an engine starter, for raising the engine speed NEto a point higher than a predetermined value NE′ at which complete combustion can take place, for example, to a point higher than an idling speed, at which the engine14can be kept operated by itself. After the engine speed NEhas been raised to the above-indicated point, the hybrid control means82commands the fuel injection device66to supply the engine14with the fuel, and commands the ignition device68to start the engine14.

The hybrid control means82is further configured to establish a so-called “torque assisting” mode in which the engine14operated as a vehicle drive power source in the engine drive mode is assisted by the second electric motor M2operated to drive the drive wheels40, with an electric energy supplied from the first electric motor M1and/or the electric-energy storage device56through the electric path described above.

The hybrid control means82is further configured to place the first electric motor M1in the non-load freely rotatable state, for thereby preventing power transmission through the transmission mechanism10, that is, for establishing a state in which the power transmission path through the transmission mechanism10is disconnected, and to also place the second electric motor M2in the non-load state to prevent the transmission mechanism10from providing an output. Namely, the hybrid control means82can place the transmission mechanism10in its neutral state by placing the electric motors M1, M2in the non-load state.

In the EV drive mode in which only the second electric motor M2is operated as the vehicle drive power source while the engine14is held at rest, the oil pump30is not operated, so that the lubricant is not supplied from the oil pump30to the predetermined parts of the transmission mechanism10, such as the gears of the planetary gear set20and the ball bearings26,28. In the EV drive mode, therefore, a motor running counter is operated to count continuation of the motor drive mode in which the second electric motor M2is operated while the engine14is held at rest, and a forced operation (motoring) of the engine14is performed by the first electric motor M1to operate the oil pump30to supply a predetermined amount of the lubricant, when a count of the motor running counter has reached a predetermined upper limit.

The above-described motor running counter is a motor running distance counter configured to count a distance L of continuous running (EV running distance L) of the vehicle in the motor drive mode without an operation of the engine14. That is, the count of the motor running counter represents the distance L of actual running of the vehicle in the EV drive mode established after the engine14is stopped. Alternatively, the above-described motor running counter is a motor running time counter configured to count a length of time T of continuous running (EV running time T) of the vehicle in the motor drive mode without the operation of the engine14. That is, the count of the motor running counter represents the length of time T of actual running of the vehicle in the EV drive mode established after the engine14is stopped.

The above-described predetermined upper limit of the count is a threshold value predetermined by experimentation to determine whether the engine14should be operated by the first electric motor M1to operate the oil pump30to supply the lubricant to the predetermined parts of the transmission mechanism10, to prevent deterioration of durability of the predetermined parts due to metal contacts of the parts. Where the count represents the EV running distance L, for example, a predetermined upper limit (threshold value) Lα is used for the EV running distance L. Where the count represents the EV running time T, a predetermined upper limit (threshold value) Tα is used for the EV running time T.

The above-described predetermined amount of the lubricant is an amount of the lubricant predetermined by experimentation, which is sufficient to improve the durability of the predetermined parts of the transmission mechanism10by forming oil films on the metal contact surfaces. A supply of the thus predetermined amount of the lubricant is based on the time and speed of the forced operation of the engine14by the first electric motor M1, for example. Namely, the time and speed of the forced operation of the engine14by the first electric motor M1required to supply the predetermined amount of the lubricant are predetermined on the basis of an amount of delivery of the lubricant by the oil pump30, which is determined by the capacity of the oil pump30, the operating time of the oil pump30and the operating speed of the oil pump30. The rate of flow of the lubricant decreases with a decrease of the temperature THOILof the lubricant. In this respect, it is desirable to increase the time and/or speed of the forced operation of the engine14with a decrease of the temperature THOILof the lubricant so as to ensure the predetermined amount of the lubricant.

The forced operation of the engine14by the first electric motor M1to operate the oil pump30to lubricate the predetermined parts of the transmission mechanism10during EV running results in deterioration of the charged state SOC of the electric-energy storage device56from which the electric energy is supplied to the first electric motor M1. Accordingly, the maximum EV running distance and time are reduced, and the engine14should be operated (started) at an earlier point of time, giving rise of a risk of reduction of the energy efficiency of the vehicle, for instance, reduction of the fuel economy of the vehicle. From another point of view, the forced operation of the engine14in the EV drive mode means an operation of the engine irrespective of the vehicle running by the electric motor, giving rise to a risk of giving the user of the vehicle a sense of anxiety. In this respect, it is particularly noted that the hybrid vehicle8according to the present embodiment is a so-called “plug-in hybrid vehicle” in which the electric-energy storage device56is chargeable with an electric energy supplied from the commercial electric power source70, and which permits comparatively long running time and distance in the EV drive mode. However, the forced operation of the engine14by the first electric motor M1during EV running if performed frequently may reduce advantages of the plug-in hybrid vehicle in the EV running mode, such as an improvement of the fuel economy.

In view of the above, the present embodiment is configured such that the forced operation of the engine14by the first electric motor M1to operate the oil pump30to supply the above-descried predetermined amount of the lubricant is performed during charging of the electric-energy storage device56by the commercial electric power source70(namely, during a plug-in charging of the electric-energy storage device56), irrespective of whether the count of the above-described motor running counter (representing the EV running distance L or EV running time T) has reached the predetermined upper limit (EV running distance upper limit Lα or EV running time upper limit Tα), and the motor running counter is reset, in order to reduce the frequency of the forced operation of the engine14by the first electric motor M1in the EV drive mode.

Described in detail, a vehicle-power-source-switch operation determining portion in the form of vehicle-power-source-switch determining means84is provided to determine whether a vehicle power source switch has been operated by the user to a Ready-on state, for instance, to start running of the vehicle in a power-off state. For example, this determination is made by determining whether an output signal of a power switch has been received during an operation of a brake pedal after a power-on operation, for example, inserting a key into a key slot. The vehicle-power-source-switch determining means84also determines whether the vehicle power source switch has been operated by the user to a Ready-off state, for instance, to terminate running of the vehicle in a power-on state. For example, this determination is made by determining whether an output signal of the power switch has been received while the vehicle running speed V is lower than a threshold value V′. This threshold value V′ is predetermined by experimentation and stored in memory for determining whether the vehicle is stationary. The above-described power-on state of the vehicle is a state which is established by starting a hybrid system for permitting running of the vehicle and in which the vehicle running is controlled by hybrid control commands associated with the vehicle running. The operation to start the vehicle running is performed to start the control devices and to implement a system check (including an abnormality check relating to the hybrid control) of the control devices for placing the vehicle in a drivable state (in the Read-on state), and should be distinguished from an operation to start the vehicle when the vehicle is stopped at a stop signal on a roadway. The above-described power-off state of the vehicle is a state in which the hybrid system cannot be started to permit starting of the vehicle running, but it is possible to detect connection of the connector74for plug-in charging of the electric-energy storage device56by the commercial electric power source70, and to monitor and control the plug-in charging.

An EV drive mode determining portion in the form of EV drive mode determining means86is provided to determine whether the present state of the vehicle requires the vehicle to be placed in the EV drive mode. This determination is made by determining whether the hybrid control means82has determined that the EV drive mode should be established, or whether the EV drive mode is actually established. Thus, the EV drive mode determining means86determines that the vehicle is placed in the EV drive mode, if the vehicle is placed in a state in which the EV drive mode should be established, irrespective of whether the EV drive mode is actually established.

A charged state determining portion in the form of charged state determining means88is provided to determine whether an actual electric energy amount P representative of the charged state SOC of the electric-energy storage device56is equal to or smaller than a predetermined threshold Pα. This threshold Pα is a charging start threshold predetermined by experimentation to determine whether the electric-energy storage device56should be charged by the first electric motor M1operated as the electric generator by the engine14when the charged state SOC of the electric-energy storage device56is not sufficient during the vehicle running in the EV drive mode, for instance.

When the charged state determining means88has determined that the actual electric energy amount P representative of the charged state SOC of the electric-energy storage device56is equal to or smaller than the predetermined threshold Pα, the hybrid control means82energies the first electric motor M1in the EV drive mode to raise the first electric motor speed NM1for raising the engine speed NEto a level not lower than a predetermined level NE′ at which complete combustion is possible. At the same time, the hybrid control means82commands the fuel injection device66to inject a fuel into the engine14, and commands the ignition device68to ignite the engine14, for thereby starting the engine14. After the engine14has been started, the hybrid control means82resets the above-described motor running counter (to reset the counted EV running distance L or EV running time T) to its initial state.

A vehicle speed determining portion in the form of vehicle speed determining means90is provided to determine whether the actual vehicle running speed V is equal to or higher than a predetermined value Vα. When the vehicle running speed V (operating speed NM2of the second electric motor M2) is raised in the EV drive mode, the first electric motor M1, pinion gear P, and bearings and other parts within the transmission mechanism10, for example, are operated or rotated at comparatively high speeds, as indicated by the straight line L1inFIG. 2, so that their durability may be reduced. To prevent excessive rotating speeds of those pinion gear P, bearings and other parts, it is necessary to raise the operating speed of the first electric motor M1, that is, to cause a forced operation of the engine14by the first electric motor M1. The predetermined value Vα indicated above is a threshold value obtained by experimentation to determine whether the first electric motor M1is operated to cause the forced operation of the engine14to protect the above-described parts.

A continuous EV running counting portion in the form of continuous EV running counting means92is provided to operate the motor running counter to count the continuation of the motor drive mode in which the second electric motor M2is operated while the engine14is held at rest during EV mode, for example. For example, the continuous EV running counting means92is configured to count the actual EV running distance L of the vehicle after the forced operation of the engine14is stopped as an EV running distance count L. Alternatively, the continuous EV running counting means92is configured to count the actual EV running time T after the forced operation of the engine14is stopped as an EV running time count T.

A continuous EV running determining portion in the form of continuous EV running determining means94is provided to determine whether the count of the motor running counter operated by the continuous EV running counting means92is equal to or higher than the predetermined upper limit. For example, the continuous EV running determining means94is configured to determine whether the EV running distance L counted under the control of the continuous EV running counting means92is equal to or longer than the predetermined threshold value Lα. Alternatively, the continuous EV running determining means94is configured to determine whether the EV running time T counted under the control of the continuous EV running counting means92is equal to or longer than the predetermined threshold value Tα.

An engine operating portion in the form of engine operating means96is provided to apply an engine operating command to the hybrid control means82to cause the forced operation of the engine14by the first electric motor M1, for operating the oil pump30to supply the predetermined amount of the lubricant, when the vehicle speed determining means90has determined that the actual vehicle running speed V is equal to or higher than the predetermined value Vα, or when the continuous EV running determining means94has determined that the EV running distance L is equal to or longer than the predetermined threshold value Lα, or that the EV running time T is equal to or longer than the predetermined threshold value Tα. According to the above-described engine operating command, the hybrid control means82energizes the first electric motor M1to raise its operating speed NM1, to cause the forced operation of the engine14at a suitable speed and for a suitable length of time, which suitable speed and length of time are predetermined by experimentation so that the predetermined amount of the lubricant is supplied. These speed (rpm) and length of time (sec) of the forced operation of the engine14are obtained by experimentation so that the oil pump30is operated by the forced operation of the engine14to supply the predetermined amount of the lubricant to all of the predetermined parts of the transmission mechanism10. For instance, the predetermined speed of the forced operation of the engine14is predetermined to be equal to the idling speed, and the predetermined length of time of the forced operation is predetermined to be selected within a range from several seconds to several tens of seconds. After the forced operation of the engine14by the first electric motor M1is performed, the hybrid control means82resets the above-described motor running counter (resets the counted EV running distance L or EV running time T) to its initial state.

A plug-in charging determining portion in the form of plug-in charging determining means98is provided to determine whether the electric-energy storage device56is in the process of being charged by the commercial electric power source70(in a plug-in charging state). For instance, the plug-in charging determining means98is configured to determine whether the electric-energy storage device56is being charged with an electric energy supplied from the commercial electric power source70through the inverter54, with the connector74of the commercial electric power source70being connected to the connector72to apply a voltage of the commercial electric power source70to the connector72.

When the plug-in charging determining means98has determined that the electric-energy storage device56is in the process of being charged by the commercial electric power source70, the engine operating means96applies the engine operating command to the hybrid control means82for operating the oil pump30to supply the predetermined amount of the lubricant, as well as when the engine operating command is applied to the hybrid control means82according to the affirmative determinations by the vehicle speed determining means90and the continuous EV running determining means94. The hybrid control means82operates to rotate engine14using the first electric motor M1in accordance with the engine operating command. After rotating engine14, the hybrid control means82resets a value (count) of the motor running counter.

FIG. 6is the flow chart illustrating a major control operation of the electric control device80, namely, a control operation performed to improve the fuel economy while permitting the oil pump30to supply the predetermined amount of the lubricant to the predetermined parts of the transmission mechanism10. This control operation is repeatedly performed with an extremely short cycle time of about several milliseconds to about several tens of milliseconds.

Initially, step (hereinafter “step” being omitted) S10inFIG. 6corresponding to the plug-in charging determining means98is implemented to determine whether the electric-energy storage device56is in the process of being charged by the commercial electric power source70. When the electric-energy storage device56is not in the plug-in charging state, a negative determination is obtained in S10, and the control flow goes to S20corresponding to the vehicle-power-source-switch operation determining means84, to determine whether the vehicle power source switch has been operated by the user to the Ready-on state, for instance, to start running of the vehicle in the power-off state. When a negative determination is obtained in S20, the present control routine is terminated. When an affirmative determination is obtained in S20, the control flow goes to S30corresponding to the EV drive mode determining means86, to determine whether the vehicle is presently placed in the EV drive mode. When a negative determination is obtained in S30, the present control routine is terminated. When an affirmative determination is obtained in S30, the control flow goes to S40corresponding to the charged state determining means88, to determine whether the actual electric energy amount P representative of the charged state SOC of the electric-energy storage device56is equal to or smaller than the predetermined threshold Pα. When the electric energy amount P is equal to or smaller than the predetermined threshold Pα, an affirmative determination is obtained in S40, the control flow goes to S50corresponding to the hybrid control means82, to operate the first electric motor M1to raise the engine speed NEto the level not lower than the predetermined level NE′ at which complete combustion is possible. At the same time, the fuel injection device66is operated to inject the fuel into the engine14, and the ignition device68is operated to ignite the engine14, for thereby starting the engine14. After the engine14has been started, the counted EV running distance L and EV running time T are reset.

When a negative determination is obtained in S40, the control flow goes to S60corresponding to the vehicle speed determining means90, to determine whether the actual vehicle running speed V is equal to or higher than the predetermined value Vα. When the actual vehicle running speed V is not equal to or higher than the predetermined value Vα, a negative determination is obtained in S60, and the control flow goes to S70corresponding to the continuous EV running determining means94, to determine whether the EV running distance L counted under the control of the continuous EV running counting means92is equal to or longer than the predetermined threshold value Lα. When the EV running distance L is not equal to or longer than the predetermined threshold value Lα, i.e., the determination in S70is negative, the control flow goes to S80also corresponding to the continuous EV running determining means94, to determine whether the EV running time T counted under the control of the continuous EV running counting means92is equal to or longer than the predetermined threshold value Tα. When an affirmative determination is obtained in any one of the above-described S60, S70and S80, the control flow goes to S90corresponding to the engine operating means96and the hybrid control means82, to generate the engine operating command for causing the forced operation of the engine14by the first electric motor M1to operate the oil pump30to supply the predetermined amount of the lubricant, so that the first electric motor M1is energized according to the engine operating command, to raise the first electric motor speed NM1, for forcibly operating the engine14for the predetermined length of time and at the predetermined speed. After the forced operation of the engine14by the first electric motor M1is performed, the counted EV running distance L and the counted EV running time T are reset.

When the EV running time T is not equal to or longer than the predetermined threshold value Tα, a negative determination is obtained in S80, and the control flow goes to S100corresponding to the vehicle-power-source-switch operation determining means84, to determine whether the vehicle power source switch has been operated by the user to the Ready-off state, for instance, to terminate running of the vehicle in the power-on state. When a negative determination is obtained in S100, the above-described step S30and subsequent steps are repeatedly implemented. When an affirmative determination is obtained in S100, the present control routine is terminated. When an affirmative determination is obtained in S10in the plug-in charging state, on the other hand, the control flow goes to S110corresponding to the engine operating means96and the hybrid control means82, to generate the engine operating command for operating the oil pump30to supply the predetermined amount of the lubricant, as in S90described above, so that the engine14is forcibly operated by the first electric motor M1according to the engine operating command, and the counted EV running distance L and the counted EV running time T are reset after the forced operation of the engine14by the first electric motor M1.

In the embodiment descried above, the engine14is forcibly operated by the first electric motor M1for operating the oil pump30to supply the predetermined amount of the lubricant during the plug-in charging of the electric-energy storage device56by the commercial electric power source70, and the above-described motor running counter (counting the EV running distance L and the EV running time T) is reset, making it possible to reduce the frequency of operations of the engine14which take place to operate the oil pump30to supply the predetermined amount of the lubricant, each time the count of the motor running counter has reached the predetermined upper limit in the EV drive mode. Accordingly, the reduction of the stored electric energy amount SOC of the electric-energy storage device56during EV running can be minimized, permitting continuation of the EV drive mode for a longer length of time, resulting in prolonged EV running time and distance, for instance, and a consequent improvement of the fuel economy. Thus, it is possible to improve the fuel economy while permitting an adequate supply of the lubricant to the predetermined parts of the transmission mechanism10using oil pump30. Additionally, it is possible to reduce the risk of giving the vehicle user a sense of anxiety which would be caused by the forced operation of the engine14in the EV drive mode, which takes place irrespective of the vehicle running in the EV drive mode. Thus, the advantage of the EV drive mode of the plug-in hybrid vehicle is improved.

The present embodiment is further arranged such that the engine14is forcibly operated by the first electric motor M1operatively connected to the engine. Thus, the forced operation of the engine14without its starting or complete combustion can be adequately performed by operating the first electric motor M1.

In the present embodiment, the transmission mechanism10is an electrically controlled differential portion which has the planetary gear set20operatively connected to the engine14, and the first electric motor M1operatively connected to the planetary gear set20, and in which the differential state of the planetary gear set20is controlled by controlling the operating state of the first electric motor M1. The second electric motor M2which cooperates with the engine14to serve as the vehicle drive power source is operatively connected to the drive wheels40, and the first electric motor M1is operated to forcibly operate the engine14, so that the forced operation of the engine14without its starting or complete combustion can be adequately performed by operating the first electric motor M1. In addition, the hybrid vehicle can be run in the EV drive mode by using the second electric motor M2adequately.

The present embodiment is further arranged such that the above-described motor running counter is the motor running distance counter configured to count the distance L of continuous running of the hybrid vehicle in the EV drive mode without an operation of the engine14, so that the oil pump30is operated to supply the lubricant at an adequate point of time in the EV drive mode.

The present embodiment is also arranged such that the above-described motor running counter is the motor running time counter configured to count the length of time T of continuous running of the hybrid vehicle in the EV drive mode without an operation of the engine14, so that the oil pump30is operated to supply the lubricant at an adequate point of time in the EV drive mode.

The present embodiment is further arranged such that the above-described predetermined amount of the lubricant is supplied on the basis of the time of operation and the speed of operation of the engine14, and at least one of the time of operation and the speed of the operation is increased with a decrease of the temperature THOIL, of the lubricant, so that the lubricant can be supplied adequately by the predetermined amount, irrespective of the temperature THOILof the lubricant.

While the embodiment of this invention has been described hi detail by reference to the drawings, it is to be understood that the present invention may be otherwise embodied.

In the illustrated embodiment, the motor running counter is operated to count the EV running distance L or EV running time T, and the continuous EV running determining means94(S70and S80inFIG. 6determines whether the counted EV running distance L is equal to or longer than the predetermined threshold value Lα, and whether the counted EV running time T is equal to or longer than the predetermined threshold value Tα. However, at least one of the EV running distance L and the EV running time T may be counted by the EV running counter for determining whether the count of the motor running counter is equal to or higher than the predetermined upper limit, according to the principle of the present invention. Even in such a case, effect of the present invention is obtained to a certain extent.

In the illustrated embodiment, the determination is made in S100of the flow chart ofFIG. 6as to whether the operation to place the vehicle in the Ready-off state is performed in the power-on state, and one cycle of execution of the control routine is terminated, when the affirmative determination is obtained in S100, so that S10of the flow chart is implemented again in the next cycle of execution of the control routine. Namely, the determination as to whether the plug-in charging is performed is made in the Ready-off state, since the vehicle is configured such that the plug-in charging is performed in the Ready-off state. However, the vehicle need not be configured such that the plug-in charging is performed in the Ready-off state. That is, the provision of S100is not essential.

Although the engine operating command is generated in S90of the flow chart ofFIG. 6in the illustrated embodiment to forcibly operate the engine14by the first electric motor M1, the engine14may be started for operation by itself, according to the engine operating command. In this case, the hybrid control means82starts the engine14according to the engine operating command. In S110, however, the operation of the engine14is limited to the forced operation by the first electric motor M1, without starting of the engine14(namely, limited to the motoring by the first electric motor M1).

In the illustrated embodiment, the transmission mechanism10is provided as the power transmitting system. However, the present invention is applicable to any other power transmitting system which permits running of the vehicle in the EV drive mode, without a supply of the working fluid. For example, the present invention is applicable to a power transmitting system provided with a manual transmission well known in the art, and an engine and an electric motor which serve as a vehicle drive power source.

In the illustrated embodiment, the transmission mechanism10is provided with the differential mechanism in the form of the planetary gear set20. However, this planetary gear set20may be replaced by a differential mechanism in the form of a differential gear device having a pinion rotated by the engine14, and a pair of bevel gears which mesh with the pinion and which are operatively connected to the first electric motor M1and the output gear24, for instance.

In the illustrated embodiment, the oil pump30is provided as the lubricant supply device such that the oil pump30is coaxially connected to the crankshaft15of the engine14through the input shaft18and the damper16. However, the oil pump30may be replaced by any other lubricant supply device which is operated by the engine14to permit a supply of the lubricant to the predetermined parts of the transmission mechanism10. For instance, the lubricant supply device may be an oil pump operatively connected to the engine14through a belt or gears.

In the illustrated embodiment, the first electric motor M1operatively connected to the engine14through the planetary gear set20is provided as a rotary drive device operatively connected to the engine14. However, the first electric motor M1may be replaced by any other rotary drive device which permits a forced operation of the engine14. For example, the rotary drive device may be an electric motor (an engine starting device or starter well known in the art) operatively connected to the engine14either directly or through a belt or gears.

In the illustrated embodiment, the plug-in charging of the electric-energy storage device56is performed with an electric energy supplied from the commercial electric power source70through the inverter54. However, the plug-in charging may be performed in any other manner. For instance, the plug-in charging of the electric-energy storage device56may be performed with the electric energy supplied from the commercial electric power source70through a charging device or an external charging device exclusively provided on the vehicle, rather than the inverter54.

While the embodiment has been described for illustrative purpose only, the present invention may be embodied with various changes and improvements which may occur to those skilled in the art.

NOMENCLATURE OF REFERENCE SIGNS

8: Hybrid vehicle10: Transmission mechanism (Power transmitting system, Electrically controlled differential portion)14: Engine (Vehicle drive power source)20: Planetary gear set (Differential mechanism)30: Oil pump (Lubricant supply device)40: Drive wheels56: Electric-energy storage device70: Commercial power source (External electric power source)80: Electronic control device (Control apparatus)M1: First electric motor (Rotary drive device, Differential electric motor)M2: Second electric motor (Vehicle drive power source, Vehicle drive electric motor)