ELECTRICALLY POWERED VEHICLE AND CONTROL METHOD THEREFOR

An electrically powered vehicle includes an electric motor for generating a vehicle driving force in accordance with an accelerator operation amount by a driver, and a notification unit for notifying the driver of information about accelerator operation by the driver in a mode which makes the driver sense the accelerator operation amount more easily in the case where a wheel is in contact with an obstacle than in the case where the wheel is not in contact with the obstacle.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the same or corresponding portions in the drawing will be given the same reference symbols and the description thereof will not be repeated.

(Configuration of Electrically Powered Vehicle)

FIG. 1is a schematic view illustrating a configuration of a hybrid vehicle5serving as a representative example of an electrically powered vehicle according to an embodiment of the present invention.

With reference toFIG. 1, hybrid vehicle5includes an engine ENG, motor generators MG1and MG2, a battery10, a power conversion unit (PCU)20, a power split device PSD, a reduction device RD, front wheels70L and70R, rear wheels80L and80R, and an electronic control unit (ECU)30. A control device according to the present embodiment is embodied through execution of a program by ECU30, for example. InFIG. 1, hybrid vehicle5is exemplified to have front wheels70L and70R served as drive wheels; however, it is acceptable that rear wheels80L and80R serve as the drive wheels in place of front wheels70L and70R. Alternatively, in addition to the configuration inFIG. 1, a motor generator for driving rear wheels80L and80R may be further disposed so as to achieve a 4WD configuration.

The driving force generated by engine ENG is split into two paths by power split device PSD. One path is for driving front wheels70L and70R via reduction device RD. The other path is for driving the motor generator MG1to generate electric power.

Motor generator MG1is typically constituted by a three-phase AC synchronous motor generator. Driven by the driving force of engine ENG split by power split device PSD, motor generator MG1generates electric power as a generator. Not only motor generator MG1functions as a generator but also functions as an actuator for controlling the rotation speed of engine ENG.

The electric power generated by motor generator MG1is selectively distributed in accordance with an operating state of the vehicle and a SOC (State Of Charge) of battery10. For example, in normal running and rapid acceleration, the electric power generated by motor generator MG1is used directly as the power to drive motor generator MG2as a motor. On the other hand, in the case where the SOC of battery10is less than a prescribed value, the electric power generated by motor generator MG1is converted by power conversion unit20from AC power to DC power and stored in battery10.

Motor generator MG1is also used as a starter in starting engine ENG. When starting engine ENG, motor generator MG1is supplied with electric power from battery10and works as an electric motor. Thus, motor generator MG1cranks engine ENG to start it.

Motor generator MG2is typically constituted by a three-phase AC synchronous motor generator. When motor generator MG2is driven as an electric motor, it is driven by at least one of the electric power stored in battery10and the electric power generated by motor generator MG1. A driving force of motor generator MG2is transmitted to front wheels70L and70R through the intermediary of reduction device RD. Thereby, the vehicle is driven to run by engine ENG assisted by motor generator MG2or to run by only the driving force from motor generator MG2.

In a regenerative braking of the vehicle, motor generator MG2is driven by front wheels70L and70R through the intermediary of reduction device RD, and motor generator MG2is made to work as a generator. Thereby, motor generator MG2works as a regenerative brake which converts braking energy into electric energy. The electric power generated by motor generator MG2is stored in battery10through the intermediary of power conversion unit20.

Battery10is constituted by, for example, a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. In the embodiments of the present invention, battery10is illustrated as a representative example of a “power storage device”. In other words, any other power storage device such as an electric double-layer capacitor may also be used in place of battery10. Battery10supplies a DC voltage to power conversion unit20, and meanwhile is charged with a DC voltage from power conversion unit20.

Power conversion unit20performs a bidirectional electric power conversion from DC power supplied by battery10into AC power for driving and controlling the motor and from AC power generated by the generators into DC power.

Hybrid vehicle5further includes a steering wheel40, an accelerator position sensor44for detecting an accelerator opening degree Acc corresponding to a stepped amount of the accelerator pedal by the driver, a brake pedal position sensor46for detecting a brake pedal position BP, a shift position sensor48for detecting a shift position SP, and a G sensor50for detecting an acceleration of hybrid vehicle5.

Further, motor generators MG1and MG2are disposed with rotation angle sensors51and52for detecting a rotor rotation angle, respectively. A rotor rotation angle θ1 of motor generator MG1detected by rotation angle sensor51and a rotor rotation angle θ2 of motor generator MG2detected by rotation angle sensor52are transmitted to ECU30. It should be noted that rotation angle sensor51and52may be omitted in case that rotor rotation angle θ1 can be estimated in ECU30on the basis of a current, a voltage or the like of motor generator MG1and rotor rotation angle θ2 can be estimated in ECU30on the basis of a current, a voltage or the like of motor generator MG2.

ECU30is electrically connected to engine ENG, power conversion unit20and battery10. On the basis of detection signals from various sensors, ECU30collectively controls the operating state of engine ENG, the driving state of motor generators MG1and MG2, and the state of charge of battery10so as to keep hybrid vehicle5in a desired running state.

ECU30is further electrically connected to a combination meter100disposed in the front of the driver's seat in hybrid vehicle5. As to be described later, combination meter100includes a display panel configured to be capable of displaying various information (text information and image information) for the driver to perform the driving, and a speaker capable of outputting audio sound to the driver. Under the control of ECU30, the display panel and the speaker can notify the driver of various information. In other words, combination meter100constitutes a “notification unit” according to the present invention.

FIG. 2is a schematic diagram for explaining in detail a power train in hybrid vehicle5ofFIG. 1.

With reference toFIG. 2, the power train (hybrid system) of hybrid vehicle5includes motor generator MG2, reduction device RD coupled to an output shaft160of motor generator MG2, engine ENG, motor generator MG1, and power split device PSD.

In the example illustrated inFIG. 2, power split device PSD is constituted by a planetary gear mechanism, and includes a sun gear151coupled to a sun gear shaft which is hollow and has a shaft center thereof through which a crank shaft150is penetrated, a ring gear152which is supported in such a way that it can rotate coaxially with crank shaft150, a pinion gear153which is disposed between sun gear151and ring gear152and is configured to revolve while rotating along the outer periphery of sun gear151, and a planetary carrier154which is coupled to an end portion of crank shaft150for supporting the rotation shaft of each pinion gear153.

Power split device PSD has three shafts including the sun gear shaft coupled to sun gear151, a ring gear case155coupled to ring gear152and crank shaft150coupled to planetary carrier154, and the three shafts serve as power input/output shafts. As the power input or output to any two shafts among the three shafts is determined, the power input to the remaining shaft is determined on the basis of the power input or output to the two other shafts.

A counter drive gear170for retrieving power is disposed outside ring gear case155and is configured to rotate integrally with ring gear152. Counter drive gear170is coupled to a power transmission reduction gear RG. Ring gear case155corresponds to an “output member” in the present invention. Accordingly, in accordance with the electric power and the power input/output from the motor generator MG1, power split device PSD outputs at least a part of the output from engine ENG to the output member.

Moreover, the transmission of power is performed between counter drive gear170and power transmission reduction gear RG. Power transmission reduction gear RG drives a differential gear DEF which is connected to front wheels70L and70R serving as drive wheels. On a descending slope or the like, the rotation of the drive wheels is transmitted to differential gear DEF, and power transmission reduction gear RG is driven by differential gear DEF.

Motor generator MG1includes a stator131which generates a rotating magnetic field, and a rotor132which is disposed inside stator131and has a plurality of permanent magnets embedded therein. Stator131includes a stator core133and a three-phase coil134wound around stator core133. Rotor132is coupled to the sun gear shaft rotating integrally with sun gear151of power split device PSD. Stator core133is formed through stacking thin electromagnetic steel sheets, and is fixed to a case (not shown).

Motor generator MG1operates as an electric motor which rotates rotor132according to the interaction between a magnetic field generated by the permanent magnets embedded in rotor132and a magnetic field generated by three-phase coil134. Motor generator MG1also operates as a generator which generates an electromotive force at both ends of three-phase coil134according to the interaction between the magnetic field generated by the permanent magnets and the rotation of rotor132.

Motor generator MG2includes a stator136which generates a rotating magnetic field, and a rotor137which is disposed inside stator136and has a plurality of permanent magnets embedded therein. Stator136includes a stator core138and a three-phase coil139wound around stator core138.

Rotor137is coupled to ring gear case155rotating integrally with ring gear152of power split device PSD through the intermediary of reduction device RD. Stator core138is formed through stacking, for example, thin electromagnetic steel sheets, and is fixed to a case (not shown).

Similarly, motor generator MG2operates as a generator which generates an electromotive force at both ends of three-phase coil139according to the interaction between the magnetic field generated by the permanent magnets and the rotation of rotor137. Motor generator MG2also operates as an electric motor which rotates rotor137according to the interaction between a magnetic field generated by the permanent magnets and a magnetic field generated by three-phase coil139.

Reduction device RD performs speed reduction through a structure in which a planetary carrier166which is one of the rotating elements of the planetary gear is fixed to a case. In other words, reduction gear RD includes a sun gear162coupled to an output shaft160of rotor137, a ring gear168rotating integrally with ring gear152, and a pinion gear164intermeshing with ring gear168and sun gear162for transmitting the rotation of sun gear162to ring gear168. For example, if the number of teeth of ring gear168is set twice or more relative to the number of teeth of sun gear162, the reduction ratio can be doubled or more.

Thereby, the rotational force from motor generator MG2is transmitted through the intermediary of reduction device RD to output member (ring gear case)155rotating integrally with ring gears152and168. In other words, motor generator MG2is configured to apply power from output member155to the drive wheels. It should be noted that it is acceptable to couple output shaft160of motor generator MG2to output member155without disposing reduction device RD, i.e., without a reduction gear ratio.

Power conversion unit20includes a converter12, and inverters14and22. Converter12converts a DC voltage Vb from battery10into a DC voltage VH to be applied between a power supply line PL and a ground line GL. In addition, converter12is configured to allow bi-directional voltage conversion from DC voltage VH between power supply line PL and ground line GL into DC voltage Vb for charging battery10or vice versa.

Inverters14and22are generally constituted by a three-phase inverter and configured to convert DC voltage VH between power supply line PL and ground line GL into an AC voltage and output the AC voltage to motor generators MG2and MG1, respectively. Further, inverters14and22are configured to convert an AC voltage generated respectively by motor generators MG2and MG1into DC voltage VH and apply it between power supply line PL and ground line GL.

In hybrid vehicle5constructed as described above, ECU30stores a table in which accelerator opening degree Acc corresponding to a stepped amount of the accelerator pedal by the driver is associated with a required torque to be output to output member155. ECU30, with reference to the table, calculates the required torque to be output to output member155on the basis of accelerator opening degree Acc, and controls the operating state of engine ENG and the driving state of motor generators MG1and MG2so as to cause a required driving force corresponding to the required torque to be output to output member155.

FIG. 3is a block diagram illustrating a control structure by ECU30according to the present embodiment. Each functional block illustrated inFIG. 3is typically embodied by executing a program stored preliminarily in ECU30, and it is also acceptable that a part of or the entire part of its functions is implemented by dedicated hardware.

With reference toFIG. 3, ECU30includes a brake ECU32and a power management ECU34. Brake ECU32and power Management ECU34are connected in such a way that they can communicate with each other.

G sensor50detects an acceleration of the vehicle and transmits the detection result to brake ECU32. Brake ECU32controls a braking force from a braking device (not shown) on the basis of an output value from G sensor50.

Rotation angle sensor52detects rotor rotation angle θ2 of motor generator MG2and transmits it to power management ECU34. Power Management ECU34, on the basis of the received rotor rotation angle θ2 of motor generator MG2, calculates a rotation speed of motor generator MG2per unit time (motor rotation speed) Nm2. Power management ECU34, on the basis of the calculated motor rotation speed Nm2, calculates a speed (vehicular speed) V of hybrid vehicle5. Vehicular speed V is correspondent to the rotation speed of output member155. Accelerator position sensor44transmits the detected accelerator opening degree Acc to power management ECU34.

Although not illustrated in the drawings, ECU30further includes a battery ECU configured to manage and control a charge and discharge state of battery10, an engine ECU configured to control an operation state of engine ENG, and a MG_ECU configured to control a driving state of motor generators MG1and MG2in accordance with the state of hybrid vehicle5. Power management ECU34controls the entire hybrid system through a reciprocal control and management on battery ECU, engine ECU, MG_ECU, brake ECU32and the like so as to make hybrid vehicle5run at the best efficiency.

Specifically, power management ECU34, in accordance with the vehicle state of hybrid vehicle5and the driving operations, calculates a vehicle driving force and/or a vehicle braking force required by the whole hybrid vehicle5. The vehicle state includes vehicular speed V. The driving operations include accelerator opening degree Acc, brake pedal position BP, shift position SP and the like.

To achieve the required vehicle driving force or vehicle braking force, power management ECU34determines an output request to motor generators MG1and MG2and an output request to engine ENG. Hybrid vehicle5may run on only an output from motor generator MG2while engine ENG is stopped. Thus, it is possible to increase energy efficiency by determining each output request so as to prevent engine ENG from being activated in a region where fuel consumption is poor. The output request to motor generators MG1and MG2is set under such a restriction that an electric power range capable of charging or discharging battery10is reserved so as to allow battery10to be charged or discharged. In other words, in the case where the output power of battery10cannot be secured, the output from the motor generator MG2is restricted.

Power management ECU34, in accordance with an output request set for motor generators MG1and MG2, calculates the torque and the rotation speed of motor generators MG1and MG2, and outputs to MG_ECU a control command about the torque and the rotation speed and a control command value about voltage VH.

Further, power management ECU34generates an engine control instruction representing a determined engine power and a desired engine rotation speed and outputs it to engine ECU. In accordance with the engine control instruction, fuel injection, ignition timing, valve timing and the like of engine ENG (not shown) are controlled.

MG_ECU, in accordance with a control command from power management ECU34, generates a control signal for performing a drive instruction which instructs the conversion of a DC voltage output from converter12to an AC voltage for driving motor generator MG1, and a control signal for performing a regeneration instruction which instructs the conversion of an AC voltage generated by motor generator MG1into a DC voltage to be output back to converter12. These control commands (MG1control commands) for motor generator MG1are output to inverter22. Similarly, MG_ECU generates a control signal for performing a drive instruction which instructs the conversion of a DC voltage to an AC voltage for driving motor generator MG2, and a control signal for performing a regeneration instruction which instructs the conversion of an AC voltage generated at motor generator MG2into a DC voltage to be output back to converter12. These control commands (MG2control commands) for motor generator MG2are output to inverter14.

MG_ECU generates a control signal for performing a voltage step-up instruction, a control signal for performing a voltage step-down instruction, and a shut-down signal for instructing operation inhibitions to converter12so as to control DC voltage VH in accordance with the control command from power management ECU34. Thereby, the charge and discharge power of battery10is controlled according to the voltage conversion by converter12in response to these control signals.

Power management ECU34further controls and manages a meter ECU110configured to control a display panel120and a speaker122which are disposed in combination meter100.

Here, it is assumed that hybrid vehicle5constructed as described above is in a state in which a wheel is in contact with an obstacle such as a step or a wheel block (locked state). In this situation, the rotation speed of output member155, i.e., the rotation speed of motor generator MG2is in a very low speed range. It should be noted that as a wheel is in the locked state, since the rotor position of motor generator MG2is fixed, a current flows continuously into a specific phase of motor generator MG2, and thereby, an inverter element for applying the current to the coil of the specific phase will generate more heat than the other inverter element.

As the accelerator pedal is further stepped down by the driver from the locked state of the wheel, ECU30(power management ECU34) controls the operating state of engine ENG and the driving state of motor generators MG1and MG2so as to output the required driving force calculated according to accelerator opening degree Acc corresponding to the stepped amount of the accelerator pedal operated by the driver to output member155. Consequently, as the driver further steps down the accelerator pedal, the required driving force corresponding to the stepped amount increases. Therefore, when the wheel climbs over an obstacle such as a step or a wheel block to escape from the locked state, it is possible that the driver may have such a feeling that the vehicle is rushing out.

In a normal vehicle with only an engine served as a power source, as the driver steps down the accelerator pedal, the engine speed increases in accordance with the increment of the stepped amount, and accordingly, a driving sound of the engine increases in accordance with the increment of the engine speed. Therefore, when a wheel is in the locked state, through the driving sound of the engine which increases in accordance with the increasing stepped amount of the accelerator pedal, it is possible to make the driver recognize the situation and the operation amount of the accelerator pedal. As a result, it is possible to prevent the driver from further stepping down the accelerator pedal excessively.

In contrast, in an electrically powered vehicle with an electric motor served as a power source, since the driving sound of the electric motor is relatively smaller than the driving sound of the engine, it is difficult to make the driver recognize the situation where a wheel is in the locked state and the operation amount of the accelerator pedal through the driving sound of the electric motor. Thus, it is possible that the driver may misjudge the state where a wheel is in the locked state as a state where a sufficient torque is not output from the electric motor due to an insufficient stepped amount of the accelerator pedal, which thereby makes the driver further step down the accelerator pedal.

Therefore, in the electrically powered vehicle according to the present embodiment, when a wheel is in the locked state, power management ECU34controls the notification mode of combination meter100so as to notify the driver of information about the accelerator operation.

FIG. 4is a block diagram explaining controls of combination meter100according to an embodiment of the present invention.

With reference toFIG. 4, power management ECU34includes a MG2 rotation speed detecting unit340and a lock detecting unit342. MG2 rotation speed detecting unit340detects MG2 rotation speed Nm2 on the basis of rotor rotation angle θ2 which is detected by rotation angle sensor52of motor generator MG2.

Lock detecting unit342calculates vehicular speed V (corresponding to the rotation speed of output member155) on the basis of motor rotation speed Nm2 detected by MG2 rotation speed detecting unit340. Lock detecting unit342, on the basis of the calculated vehicular speed V, an output value G from G sensor50and an output value Acc from accelerator position sensor44, detects whether or not a wheel is in the locked state. If the wheel is detected to be in the locked state, lock detecting unit342turns on a lock determination flag FLC.

When lock determination flag FLC is turned on, meter ECU110issues a meter control command to display panel120and a sound control command to speaker122so as to notify the driver of the information about the accelerator operation in a mode in which as the accelerator opening degree Acc becomes greater, the driver is made to sense the accelerator operation amount more easily.

FIG. 5is a flowchart for achieving the controls of combination meter100according to an embodiment of the present invention.

With reference toFIG. 5, power management ECU34, on the basis of the output value from G sensor50, accelerator opening degree Acc and vehicular speed V, determines whether or not a wheel is in the locked state. Specifically, at step S01, power management ECU34firstly determines whether or not a road on which hybrid vehicle5is running or parking is sloping on the basis of the output value from G sensor50.

At step S01, power management ECU34estimates a gradient of the road on which hybrid vehicle5is running or parking on the basis of the output value of the G sensor50. Then, on the basis of the estimated gradient of the road, power management ECU34determines whether or not the road is sloping. For example, if the estimated gradient of the road is smaller than a prescribed gradient, power management ECU34determines that the road on which hybrid vehicle5is running or parking is not sloping, i.e., the road is a flat road.

On the other hand, if the estimated gradient of the road is equal to or greater than the prescribed gradient (YES at step S01), power management ECU34determines that the road is an ascending road. In the case where the road on which hybrid vehicle5is running or parking is an ascending road, the control of combination meter100to be described later is not performed. This is because that when the vehicle is running on an ascending road, there is no possibility of giving the driver a feeling that the vehicle is rushing out.

If it is determined that the road on which hybrid vehicle5is running or parking is not sloping (NO at step S01), at step S02, power management ECU34determines whether or not accelerator opening degree Acc is equal to or greater than a prescribed determination value X1. Determination value X1 is a threshold for determining whether or not the driver is stepping down the accelerator pedal (i.e., X1>0[%]). If accelerator opening degree Acc is smaller than determination value X1 (NO at step S02), power management ECU34keeps lock determination flag FLC at OFF and ends the process.

On the other hand, when accelerator opening degree Acc is equal to or greater than determination value X1 (YES at step S02), at step S03, power management ECU34determines whether or not vehicular speed V is in a very low vehicular speed range containing a vehicular speed of 0 (V≦Y [km/h]). If vehicular speed V is not in the very low vehicular speed range (NO at step S03), power management ECU34keeps lock determination flag FLC at OFF and ends the process.

On the contrary, if vehicular speed V is in the very low vehicular speed range (YES at step S03), at step S04, power management ECU34determines that a wheel of hybrid vehicle5is in the locked state. Then, power management ECU34sets lock determination flag FLC to ON. In other words, the processing of steps S01to S04corresponds to the function of lock detecting unit342inFIG. 5.

After lock determination flag FLC is set to ON by power management ECU34, at steps S05to S09, meter ECU110controls the notification mode of display panel120and speaker122to notify the driver of information about the accelerator operation.

Specifically, at step S05, meter ECU110determines whether or not accelerator opening degree Acc is equal to or greater than a prescribed reference amount X2. If accelerator opening degree Acc is smaller than prescribed reference amount X2 (NO at step S05), meter ECU110maintains the display mode of combination meter100and ends the process. Reference amount X2 is a threshold for determining whether or not the driver is stepping down the accelerator pedal (i.e., X2>0[%]).

On the other hand, if accelerator opening degree Acc is equal to or greater than prescribed reference amount X2 (YES at step S05), then at step S06, meter ECU110determines whether or not a power meter is contained in display panel120.FIG. 6(a) illustrates an example of the power meter. The power meter is disposed near the driver's seat of hybrid vehicle5for displaying a driving force (running power) used to run the vehicle. Power meter is configured as an indicating device for visibly displaying a running power used in the current running by pointing an indicating pointer at a scale mark displayed in a scale plate for indicating running power. The rotation of the indicating pointer is controlled by meter ECU110. As illustrated inFIG. 6(a), an arc-shaped bar indicating the range of power which can be set as the running power is disposed in the scale plate. Though not illustrated in the drawing, a scale number indicating the corresponding power and a unit symbol indicating the unit [kW] of the power are displayed close to the bar. On the bar, there are displayed with an eco-drive zone (ECO region in the drawing) prioritizing fuel economy at a power less than a upper power limit which is defined on the basis of the relationship between power output from engine ENG and fuel economy or output power available from battery10and at which hybrid vehicle5can run at perfect fuel economy, a power drive zone (POWER region in the drawing) prioritizing output power rather than fuel economy in a power region equal to or greater than the upper power limit, and a zone (CHARGE region in the drawing) where the running power is negative, in other words, a zone where motor generator MG2is controlled under a regenerative mode.

Returning toFIG. 5, if a power meter (seeFIG. 6(a)) is contained in display panel120(YES at step S06), at step S07, meter ECU110switches the display mode of the power meter from the display of the vehicle running power to the display of the accelerator pedal operation amount (accelerator opening degree Acc).FIG. 6(b) illustrates an example of a power meter which has been switched to the display of accelerator opening degree Acc.

With reference toFIG. 6(b), an arc-shaped bar indicating a full range of accelerator opening degrees (0-100[%]) which can be set as accelerator opening degree Acc is displayed in the scale plate. Meter ECU110controls the power meter to indicate an output value from accelerator position sensor44with an indicating pointer. Thus, the power meter serves as an indicating device for visibly displaying current accelerator opening degree Acc. Therefore, it is possible to make the driver sense the operation amount of the accelerator pedal.

On the other hand, if a power meter is not contained in display panel120(NO at step S08), at step S08, meter ECU110lights on a telltale which is disposed in display panel120for indicating the power output. At this time, if the operation amount of the accelerator pedal is equal to or greater than prescribed reference amount X2, meter ECU110alters the display mode of the telltale in accordance with the operation amount of the accelerator pedal. For example, as illustrated inFIG. 7, meter ECU110makes a blinking cycle of the telltale shorter on the basis of the output value from accelerator position sensor44as the operation amount of the accelerator pedal becomes greater. Accordingly, when the driver further steps down the accelerator pedal, the blinking cycle of the telltale will become shorter, and thereby it is possible to make the driver sense the operation amount of the accelerator pedal.

Instead of being configured to alter the blinking cycle of the telltale in accordance with the operation amount of the accelerator pedal, meter ECU110may be configured to alter the displaying brightness or displaying color of the telltale in accordance with the operation amount of the accelerator pedal.

In addition to the control of display panel120as described above, at step S09, meter ECU110further controls speaker122to issue a notification sound about the accelerator operation by the driver when the driver operation amount of the accelerator pedal is equal to or greater than prescribed reference amount X2 (YES at step S05). Specifically, meter ECU110alters the issue mode of the notification sound in accordance with the operation amount of the accelerator pedal. For example, meter ECU110controls speaker122to increase the volume of the notification sound as the operation amount of the accelerator pedal becomes greater. Alternatively, it is acceptable that speaker122is controlled to alter the tone of the notification sound in accordance with the operation amount of the accelerator pedal.

Thus, according to the electrically powered vehicle of the present embodiment, in the case where a wheel is in the locked state, display panel120(the power meter or the telltale) and speaker122are made to notify the driver of the information about the accelerator operation in a mode which makes the driver sense the accelerator operation amount more easily than in the case the wheel is not in the locked state. Thus, it is possible to make the driver recognize that a wheel is in the locked state and the operation amount of the accelerator pedal. As a result, it is possible to prevent the driver from stepping down the accelerator pedal excessively.

Modification

In the above embodiment, display panel120and speaker122are configured to be controlled in accordance with accelerator opening degree Acc; however, instead of accelerator opening degree Acc, it is acceptable that display panel120and speaker122are configured to be controlled in accordance with a vehicle driving force required for hybrid vehicle5.

FIG. 8is a flowchart for achieving the controls of combination meter100according to a modification of an embodiment of the present invention. Compared with the flowchart ofFIG. 5, the determination process for a locked state according to the present modification is performed with steps S01to S03inFIG. 5being replaced by steps S01, S021and S03, respectively, in the flowchart ofFIG. 8.

Specifically, at step S01, if it is determined that the road on which hybrid vehicle5is running or parking is not sloping (NO at step S01) on the basis of the output value from G sensor50, at step S021, power management ECU34determines whether or not the required driving force calculated on the basis of accelerator opening degree Acc is equal to or greater than a prescribed determination value P1 [Nm]. Determination value P1 [Nm] is a threshold value for determining whether or not the driver is stepping down the accelerator pedal (P1>0 [Nm]), and is set to a value greater than a creep torque to move the vehicle at a very low speed even when there is no acceleration request from the driver.

When the vehicle driving force is smaller than determination value P1 [Nm] (NO at step S021), power management ECU34keeps lock determination flag FLC at OFF and ends the process.

On the other hand, when the vehicle driving force is equal to or greater than determination value P1 (YES at step S021), at step S03, power management ECU34determines whether or not vehicular speed V is in a very low vehicular speed range containing the vehicular speed of 0 (V≦Y [km/h]). If vehicular speed V is not in the very low vehicular speed range (NO at step S03), power management ECU34keeps lock determination flag FLC at OFF and ends the process.

On the contrary, if vehicular speed V is in the very low vehicular speed range (YES at step S03), at step S04, power management ECU34determines that a wheel of hybrid vehicle5is in the locked state. Then, power management ECU34sets lock determination flag FLC to ON. In other words, the processing of steps S01to S04corresponds to the function of lock detecting unit342inFIG. 5.

If it is determined that the wheel is in the locked state, at steps S051to S09, meter ECU110controls the notification mode of display panel120and speaker122so as to notify the driver of the information about the accelerator operation.

Specifically, at step S051, meter ECU110determines whether or not the vehicle driving force is equal to or greater than a prescribed reference amount P2. If the vehicle driving force is smaller than prescribed reference amount P2 (NO at step S051), meter ECU110maintains the display mode of combination meter100and ends the process. Reference amount P2 is a threshold for determining whether or not the driver is stepping down the accelerator pedal and is set to a value greater than the creep torque (i.e., P2>0 [Nm]).

On the other hand, if the vehicle driving force is equal to or greater than prescribed reference amount P2 (YES at step S051), then at step S06, meter ECU110determines whether or not a power meter is contained in display panel120. if a power meter (seeFIG. 6(a)) is contained in display panel120(YES at step S06), at step S07, meter ECU110switches the display mode of the power meter from the display of the vehicle power to the display of the accelerator pedal operation amount (accelerator opening degree Acc) (seeFIG. 6(b)).

On the other hand, if a power meter is not contained in display panel120(NO at step S06), at step S08, meter ECU110lights on a telltale which is disposed in display panel120. Here, when the vehicle driving force is equal to or greater than prescribed reference amount P2, meter ECU110makes the blinking cycle of the telltale shorter as the vehicle driving force becomes greater.

Further at step S09, when the vehicle driving force is equal to or greater than prescribed reference amount P2 (YES at step S051), meter ECU110controls speaker122to issue a notification sound about the accelerator operation to the driver.

In the present embodiment, the hybrid vehicle having the configuration ofFIG. 1is used as an example of the electrically powered vehicle, and however, the present invention is not limited to be applied to such example. In other words, the present invention may be applied to any hybrid vehicle (for example, the so-called series hybrid vehicle or power-split hybrid vehicle) having a driving system different fromFIG. 1, any electric vehicle, and any fuel cell vehicle as long as it is mounted with an electric motor (motor generator) having a driving system which is controlled in accordance with the operation amount of the accelerator pedal.

In the present embodiment, a combination meter including a display panel and a speaker is used as an example of a notification unit capable of notifying the driver of various information; however, the notification unit is not limited to the configuration of such example. In other words, it should be noted that as long as it is possible to alter the notification mode in accordance with the accelerator operation amount in such a manner that makes the driver sense the accelerator operation amount more easily in the case where a wheel is in the locked state than in the case where the wheel is not in the lock state, any configuration can obtain the effects of the present invention.

It should be understood that the embodiments disclosed herein have been presented for the purpose of illustration and description but not limited in all aspects. It is intended that the scope of the present invention is not limited to the description above but defined by the scope of the claims and encompasses all modifications equivalent in meaning and scope to the claims.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an electrically powered vehicle mounted with an electric motor generating a driving force in accordance with an accelerator operation amount.

REFERENCE SIGNS LIST