Hybrid vehicle control unit

A hybrid vehicle control unit (HV-ECU) sets a sub-battery voltage during an engine non-operation time to be lower than a sub-battery voltage during the normal time, which decreases a charge amount to the sub-battery relative to an amount during the normal time. The HV-ECU sets the sub-battery voltage during an engine operation time to be higher than the sub-battery voltage during the engine non-operation time, which increases the charge amount to the sub-battery relative to an amount during the engine non-operation time. A SOC control according to the above-described scheme prevents a SOC decrease of the sub-battery SOC in comparison to the conventional SOC control scheme, thereby preventing charging of the sub-battery when the main battery SOC is lower than a certain threshold. Therefore, a run-down of the sub-battery is prevented.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2014-004059, filed on Jan. 14, 2014, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a hybrid vehicle drive system having a hybrid vehicle control unit used in a hybrid vehicle that is equipped with an engine and a motor-generator.

BACKGROUND INFORMATION

In recent years, hybrid vehicles have become popular because of the social demand for low fuel consumption and low emission vehicles. In a hybrid vehicle, a drive power of the vehicle is procured from both of an engine and a motor-generator, and the engine in the hybrid vehicle is also used to charge batteries, that is, for charging a main battery by driving the motor-generator to generate electricity. Further, a heater device, or an electric heater, in the hybrid vehicle is operated by receiving an electric power either from the main battery or from a sub-battery that is electrically connected to the main battery, for heating a vehicle compartment or the like.

In the hybrid vehicle having an electric heater for heating operation, for example, the heater device disclosed in a patent document 1 (i.e., Japanese Patent Laid-Open No. 2013-18420) stops an electricity supply from the main battery to the sub-battery when a main battery SOC is equal to or lower than a preset value, so that a heating capacity of the heater device as well as an EV travel capacity of the hybrid vehicle are preserved without consuming the electric power in the main battery.

The technique in the patent document 1 may cause a run-down of the sub-battery when a low-SOC state of the main battery continues for a long time, due to a no-charge control of the sub-battery.

In view of such a shortcoming of the conventional technique, an idea of the present disclosure is devised.

SUMMARY

It is an object of the present disclosure to provide a hybrid vehicle drive system in a hybrid vehicle that is equipped with an engine, a motor-generator generating electricity by a drive force of the engine, a main battery chargeable and dischargeable in an exchange of electricity with the motor-generator, a sub-battery electrically connected with the main battery, and a DC-DC converter disposed (at a position) between the main battery and the sub-battery and converting an input voltage from the main battery to an output battery output to the sub-battery which is designated as a sub-battery voltage, which at least controls the sub-battery voltage.

The hybrid vehicle drive system also includes a hybrid vehicle control unit that controls a charge amount to charge the sub-battery in the following manner when a main battery SOC is lower than a preset threshold. A unit of the charge amount used in the following description is Watt, represented as “W.”

In an engine non-operation time, the sub-battery voltage is set to a lower-than-normal value that is lower than a normal value being set in a normal time when the main battery SOC is equal to or higher than the threshold, for decreasing a charge amount to the sub-battery to be smaller than an amount in the normal time (i.e., a normal-time amount). In other words, a normal time is defined as a time when a main battery SOC is equal to or higher than a preset threshold. As such, when the main battery SOC is less than the preset threshold, in an engine non-operation time, the HV-ECU sets a sub-battery voltage during the engine operation time to be lower than a sub-battery voltage during the normal time, which decreases sub-battery charging during the engine non-operation time relative to sub-battery charging during the normal time.

In an engine operation time, the sub-battery voltage is set to a high value that is higher than an engine non-operation time value (S51) in/of the engine non-operation time, for increasing the charge amount to the sub-battery to be greater than an amount in the engine non-operation time (i.e., an engine non-operation time amount). In other words, when the main battery SOC is less than the preset threshold, in an engine operation time, the HV-ECU sets a sub-battery voltage during the engine operation time to be higher than the sub-battery voltage during the engine non-operation time, which increases sub-battery charging during the engine operation time relative to sub-battery charging during the engine non-operation time.

According to the present disclosure, when the main battery SOC is lower than the preset threshold, even though the charge to the sub-battery is restricted relative to the normal time during the engine operation time, the charge operation itself is performable (i.e., the charge of the sub-battery is not prohibited) during the engine operation time. Therefore, in comparison to the conventional technique in the patent document 1, the lowering of the sub-battery SOC is made harder, thereby preventing the run-down of the sub-battery.

On the other hand, during the engine non-operation time, the regenerated electric power from the motor-generator that is driven by the drive force of the engine, together with other electric power, are used to increase the charge amount to the sub-battery, thereby further securely preventing the run-down of the sub-battery.

Further, a sub-battery voltage control, for setting the sub-battery voltage in the engine operation time to the high value, further adjusts/increases the sub-battery voltage to a higher value as a drive load of the vehicle falls, for preferably increasing the charge amount to the sub-battery. In such manner, the engine load is increased when the drive load of the vehicle is low, thereby improving the engine efficiency as a result. In other words, the HV-ECU increases the sub-battery voltage as a drive load of the vehicle decreases, which increases the charge amount to the sub-battery.

In such a case, the charge amount to the sub-battery is determined to minimize a system loss that is calculated as a sum total of an engine loss and a sub-battery I/O loss caused by charge and discharge of the sub-battery, which yields/leads to an optimized system efficiency.

The hybrid vehicle control unit of the present disclosure may be applicable to a hybrid vehicle having an electric heater for heating a vehicle compartment or heating an engine, which is electrically connected to a sub-battery side of the DC-DC converter.

In such a case, in/during the engine non-operation time, an output of the electric heater is set to a smaller-than-normal value, which is smaller than a normal value in/of the normal time. In other words, the HV-ECU sets an output of the electric heater during the engine non-operation time to be less than an output of the electric heater during the normal time.

In/during the engine operation time, the output of the electric heater is set to a value that is greater than an engine non-operation time value, which is set to be greater than a value in/of the engine non-operation time (i.e., the great value set to be greater than the smaller-than-normal value). In other words, the HV-ECU sets an output of the electric heater during the engine operation time to be greater than the output of the electric heater during the engine non-operation time.

In such manner, when the main battery SOC is lower than the preset threshold, an electric power consumption of an EV travel is decreased than the normal time, while preventing the heating capacity for heating the vehicle compartment or for heating the engine.

Further, an electric heater output control, for setting the output of the electric heater in/during the engine operation time to the great value (i.e., to a value that is greater than the engine non-operation time value), further adjusts/increases the output of the electric heater to a greater value as a drive load of the vehicle falls, for preferably increasing (an amount of) electricity supplied from the DC-DC converter to the electric heater. In other words, the HV-ECU increases the output of the electric heater as a drive load of the vehicle decreases, which increases an amount of electricity supplied from the DC-DC converter to the electric heater. In such manner, the engine load is increased when the drive load of the vehicle is low, thereby improving the engine efficiency as a result.

Further, in such a case, an amount of decrease of the electric heater output set in the engine non-operation time (i.e., substantially, an EV travel time) is determined preferably based on an integration value of an amount of increase of the output of the electric heater in/during the engine operation time either of/in/during a so-far period that is a period of time between a specific previous time and a present time or of/in/during a past predetermined period that is a preset period of time in the past.

Further, the hybrid vehicle control unit of the present disclosure may preferably be configured to solely/entirely procure the electricity supplied to the DC-DC converter in/during the engine operation time from the motor-generator as a regenerated electric power thereof while controlling a discharge amount of the main battery to zero. In other words, the electricity supplied to the DC-DC converter in the engine operation time is procured entirely from the motor-generator.

In such manner, the energy loss accompanied by an input and output of the main battery is decreased. Further, since the control of the present disclosure is based on an assumption that the main battery SOC is low, the lowering of the main battery SOC approaching closer to a lower limit value is prevented by restricting the discharge of the main battery.

DETAILED DESCRIPTION

Hereafter, the embodiment of the present disclosure is described with reference to the drawings.

InFIG. 1,FIG. 6, andFIG. 11respectively showing a configuration of a hybrid vehicle to which a hybrid vehicle control unit of each embodiment is applied, the same numeral is assigned to the same component, and the description of the same component is not repeated. In the drawings, a double line connecting two or more components represents a mechanical connection line, a thick broken line represents an electrical connection line, and a thin solid line represents a signal line.

The configuration of the hybrid vehicle to which the hybrid vehicle control unit of the first embodiment of the present disclosure is applied is described with reference toFIG. 1.

A hybrid vehicle101shown inFIG. 1is a parallel hybrid vehicle provided with an engine2and one motor-generator31as its source of a driving force. An HV-ECU80serving as a “hybrid vehicle control unit” arbitrates the driving force of the engine2and the motor-generator31, and controls the drive of the hybrid vehicle101in an integrated manner. Especially, in each of the embodiments of the present disclosure, the HV-ECU80controls a supply of electric power to the sub-battery6mentioned later.

The driving force of the engine2is transmitted to a crankshaft15, and drives the wheel14via a deferential gear mechanism19and an axle13. An engine ECU20acquires information, including a crank angle of the crankshaft15, an engine rotation speed, etc., based on a crank angle signal and the like which are inputted from a crank angle sensor (not illustrated), and controls an operation of the engine2.

A motor-generator31is, for example, a permanent magnet type three-phase motor of a synchronous control, and is electrically connected with a main battery4via an inverter33which is a power converter for converting a direct-current power to/from an alternating current electric power of three phases.

The motor-generator31serves as a motor for outputting a mechanical power when receiving and consuming an electric power from the main battery4, i.e., for driving the wheel4to assist a driving force of the engine2, and also serves as a generator for outputting a regenerated electric power when receiving a driving power from a deceleration of the vehicle or from the engine2.

Further, at a position between the motor-generator31and the deferential gear mechanism19, as a dashed line shows, a transmission17may be provided for increasing or decreasing a rotation speed from both sides. The transmission17may have a clutch, or the clutch may be provided at a position between the engine2and the motor-generator31.

An MG-ECU30controls a switching operation of the inverter33, based on a torque instruction from the HV-ECU80and an electrical angle signal from a rotation angle sensor provided near a rotor of the motor-generator31, etc., and controls a supply of electric power to the motor-generator31.

Further, at a position between the main battery4and the inverter33, a booster converter for boosting the direct-current electric power of the main battery4may be provided.

The main battery4is an electricity storage device capable of charging and discharging electricity such as a nickel hydride battery, and a lithium ion battery, for example, and a device such as an electric double layer capacitor, etc., may also be serving as one form of the main battery4.

The main battery4is charged within a certain limit range of SOC (State Of Charge). The information on SOC of the main battery4is transmitted to the HV-ECU80.

A DC-DC converter5is connected to an electric power path on a main battery4side of the inverter33. Further, on an opposite side of the DC-DC converter5relative to the main battery4, the sub-battery6is connected.

The DC-DC converter5converts an input voltage from the main battery4to an output voltage to the sub-battery6(henceforth designated as a “sub-battery voltage”). Since the main battery4side has a higher voltage relative to the sub-battery6side, the DC-DC converter5lowers the high voltage on the main battery4side to output a low voltage toward the sub-battery6.

The sub-battery6supplies an electric power to various auxiliary devices, such as a fan, a blower, a pump and the like in the vehicle.

In such a configuration, the AC power generated by the motor-generator31is converted into the DC power by the inverter33, and is supplied to the main battery4and to the DC-DC converter5as a regenerated electric power. Further, the electric power discharged from the main battery4is supplied to the motor-generator31via the inverter33, or is supplied to the sub-battery6via the DC-DC converter5, depending on a situation.

InFIG. 1, a solid line arrow from the inverter33to the DC-DC converter5shows (a flow of) a regenerated electric power Preg, and a dashed line arrow from the main battery4to the DC-DC converter5shows (a flow of) an electric power Pmb discharged from the main battery4.

The HV-ECU80receives an input of various signals, i.e., an accelerator signal from an accelerator sensor, a brake signal from a brake switch, a shift signal from a shift switch, a speed signal about the speed of the vehicle, etc., and determines a drive state of the vehicle based on information obtained therefrom.

The HV-ECU80communicates/exchanges information with the engine ECU20, the MG-ECU30, the main battery4, the DC-DC converter5, and the sub-battery6, and controls a driving force of the engine2and the motor-generator31, as well as charge and discharge of the main battery4, and the sub-battery6, etc., in an integrated manner.

Further, other ECUs may also be provided at a position in between (i) the HV-ECU80and (ii) the main battery4, the DC-DC converter5and the sub-battery6.

In the embodiments of the present disclosure, the HV-ECU80controls the sub-battery voltage by providing an instruction to the DC-DC converter5, based on a determination of whether SOC of the main battery4is lower than a preset threshold or is equal to or higher than the threshold, and whether the engine2is in operation or is not in operation (i.e., whether it is in an engine operation time or in an engine non-operation time).

Regarding the above description, an “engine non-operation time” includes a vehicle stop time. However, the present disclosure assumes a situation of an (electric power) output being provided from the sub-battery6, it (the “engine non-operation time”) practically means an EV travel time, which is a travel of the hybrid vehicle by an output of mechanical power from the motor-generator31.

Next, the control performed by the HV-ECU80in the first embodiment is described with reference to a flowchart inFIG. 2. The sign “S” means a “step” in the description of the following flowcharts.

In S1, it is determined whether SOC of the main battery4is smaller than threshold value α. The threshold value α may be set, for example, as any value, e.g. 40%, 50%, 60% or the like.

A time when SOC of the main battery4is equal to or greater than the threshold value α is referred to as a “normal time.” In the normal time, S1is determined as NO, and S21sets the sub-battery voltage to a normal value.

When SOC of the main battery4is smaller than the threshold value α (S1:YES), it is determined in S3whether the engine2is in operation (i.e., in an engine operation time). When the engine2is not in operation (S3:NO) (i.e., in an engine non-operation time), S41sets the sub-battery voltage to be lower than the normal value.

When the engine2is in operation, i.e., in the engine operation time (S3:YES), S51sets the sub-battery voltage to be higher than the value in the engine non-operation time, i.e., the value set in S41.

If the normal value set in S21is, for example, 13 [V], the value set in S41in the engine non-operation time is lower than 13 [V], that is, for example, 11 [V].

Further, the value set in S51in the engine operation time is higher than 11 [V] in the engine non-operation time, that is, for example, may be set to 12 [V], or to 14 [V]. That is, in other words, the preset value in the engine operation time may either be higher than or be lower than the normal value.

Thus, the “sub-battery charge amount” in a unit of electric power [W] (=voltage [V]×current [A]) is controlled by changing the sub-battery voltage. That is, in the engine non-operation time, the sub-battery voltage is set to be lower than the normal value, and the charge amount of the sub-battery is decreased by reducing the electric power supply from the main battery4side of the DC-DC converter5.

On the other hand, the sub-battery voltage is set to be higher than the engine non-operation time, and the charge amount of the sub-battery is increased by promoting/increasing the electric power supply from the main battery4side of the DC-DC converter5in the engine operation time.

Further, in S51, a map ofFIG. 3or a map ofFIGS. 4A,4B,4C which respectively specifies a relationship between the charge amount of the sub-battery and other parameters is used, and the sub-battery voltage in the engine operation time is set up appropriately.

FIG. 3shows a map of a relationship between a drive load of the vehicle and the charge amount of the sub-battery, and the graph line falls toward the right side of the graph. In other words, the control performed by the HV-ECU80is that the sub-battery voltage is set to be higher as the drive load falls, for an increase of the charge amount of the sub-battery. In this map diagram, the charge amount of the sub-battery, i.e., an absolute value of the vertical axis of the map, is suitably determined according to a requested charge amount etc.

FIGS. 4A and 4Bare a characteristic diagram of a relationship between the charge amount of the sub-battery and an engine loss, and a relationship between the charge amount of the sub-battery and a sub-battery I/O loss.

The engine loss inFIG. 4Ameans the rate of loss of the thermal energy of fuel, which is not effectively changed into driving force. Generally, the engine efficiency is high when the drive load is high, and thus the engine loss decreases. Due to a correlation between the charge amount of the sub-battery and the electric power generated by the motor-generator31that is driven by the driving force of the engine2, the engine loss decreases when the charge amount of the sub-battery is large. Further, when the charge amount of the sub-battery is large, a negative inclination of the graph line becomes gentle.

The sub-battery I/O loss inFIG. 4Bis mainly a Joule heat generated with an internal resistance in association with the charge and discharge of the sub-battery6. The sub-battery I/O loss becomes large when the charge amount of the sub-battery is large, and a positive inclination of the graph becomes steep, when the charge amount of the sub-battery is large.

The system loss inFIG. 4Cis a sum total of the engine loss and the sub-battery I/O loss, and is represented by a convex curve. The HV-ECU80sets in S51, i.e., in the engine operation time, a target control value to the sub-battery charge amount W0that corresponds to the minimum value (min) of the system loss.

Therefore, when the sub-battery charge amount based on the sub-battery voltage in the normal time is smaller than W0(W−), the sub-battery voltage in the engine operation time is set to be higher than the normal value, and, when the sub-battery charge amount based on the sub-battery voltage in the normal time is larger than W0(W+), the sub-battery voltage in the engine operation time is set to be lower than the normal value.

Next, the effects in the present embodiment of the present disclosure achieved by the control of the sub-battery voltage is described with reference to a time chart inFIGS. 5A,5B, in comparison to the conventional technique.

FIG. 5Bshows an ON/OFF state of the engine2andFIG. 5Ashows a change of the sub-battery SOC according to such an ON/OFF of the engine2, respectively using a solid line for the embodiment of the present disclosure and a dashed line for the conventional technique.

Here, since the contents shown inFIGS. 5A and 5Bare shared by all the embodiments in the present disclosure, the notation inFIG. 5Areads “PRESENT DISCLOSURE” instead of “FIRST EMBODIMENT.”

When SOC of the main battery4is smaller than the threshold value α, the conventional technique completely stops the electric power supply from the main battery4to the sub-battery6. Therefore, if the drive of the auxiliary devices is performed using the electric power of the sub-battery6, the sub-battery SOC continues to fall. Thus, the sub-battery SOC falls to be lower than the “sub-battery run-down SOC” between time t2and time t3, and sub-battery run-down is caused.

In the present embodiment of the present disclosure, when SOC of the main battery4is lower than the threshold value α, the charging to the sub-battery6is not completely prohibited, even though the charging is somewhat restricted in the engine non-operation time, i.e., time t0-t1and time t2-t3. Therefore, compared with the conventional technique, the sub-battery SOC is harder to fall, and the sub-battery run-down is prevented.

On the other hand, in the engine operation time of time t1-t2, due to an increase of the charge amount of the sub-battery by the regenerated electric power from the motor-generator31that is driven by the driving force of the engine2, the sub-battery SOC goes up. Therefore, the sub-battery run-down is further, or more securely, prevented than in the engine non-operation time.

Since the regenerated electric power is also charged to the main battery4and is also used as an electric power for an EV travel of the vehicle in the above-described situation, EV travel capacity is simultaneously secured.

Further, in the first embodiment, in the engine operation time, the sub battery voltage is set to be higher when the drive load of the vehicle is low as described above inFIG. 3, and it makes the charge amount of the sub-battery increase. Therefore, the engine load is raised in such manner when the drive load of the vehicle is low, which achieves an improvement of the engine efficiency as a result.

Further, as shown inFIG. 4, when the charge amount to the sub-battery6is determined to minimize the system loss which is the sum total of the engine loss and the sub-battery I/O loss, the system efficiency is optimized.

In addition, as shown inFIG. 1, the electric power supplied to the DC-DC converter5is procured solely from the regenerated electric power Preg by the motor-generator31while controlling the discharge amount Pmb from the main battery4to zero. Thereby, the energy loss accompanying the I/O of the main battery4is reduced. Further, by restricting the discharge from the main battery4, SOC of the main battery4is prevented from approaching a lower limit.

The configuration of the hybrid vehicle to which the hybrid vehicle control unit of the second embodiment of the present disclosure is applied is described with reference toFIG. 6.

As shown inFIG. 6, in a hybrid vehicle102, an electric heater7is connected to the sub-battery6side of the DC-DC converter5. The electric heater7includes all the devices that generate heat with the electrical energy, which may be a heat pump, a PTC heater, a seat heater, etc. and are used for heating of the vehicle compartment or warming the components in the vehicle. The HV-ECU80controls the electric power supplied to the electric heater7from the DC-DC converter5according to the requested power of the electric heater7.

Next, the control performed by the HV-ECU80in the second embodiment is described with reference to a flowchart ofFIG. 7. InFIG. 7, the same step number substantially points to the same step in the first embodiment ofFIG. 2, and description of the same step is omitted.

In the control of the second embodiment, Steps S22, S42or S52, which respectively set an output of the electric heater, are performed subsequently to Steps S21, S41or S51which set the sub-battery voltage inFIG. 2.

When SOC of the main battery4is equal to or greater than the threshold value α (S1:NO), i.e., in the normal time, the output of the electric heater is set in S22to the normal value, subsequent to S21.

When SOC of the main battery4is smaller than the threshold value α (S1:YES) and in the engine non-operation time (S3:NO), the output of the electric heater is set in S42to a value that is smaller than the normal value, subsequent to S41.

When SOC of the main battery4is smaller than the threshold value α (S1:YES) and in the engine operation time (S3:YES), the output of the electric heater is set in S52to a value that is greater than the value in the engine non-operation time, subsequent to S51.

In S52, the output of the electric heater is set to a large value when the drive load of the vehicle is low, according to a map inFIG. 8. The map is prepared in plural pieces according to the magnitude of the requested output of the electric heater7.

Relative to a characteristic line for a standard requested output, which is represented by a solid line, a characteristic line for a greater-than-standard requested output is represented by a broken line, i.e., an upward shifted line of the standard output, and a characteristic line for a smaller-than-standard requested output is represented by a dashed line, i.e., an downward shifted line of the standard output. Further, the inclination of each of those lines is not necessarily a constant one.

Further, as shown inFIG. 9, an amount of decrease of the output of the electric heater7, which is smaller than the normal value in the engine non-operation time (i.e., mainly an EV travel time) is set in S42based on an integration value [J] (=[W·s]) of the amount of increase of the output of the electric heater so far, up to the present time.

That is, in other words, when the integration value of the increase of the output of the electric heater7is large, which means that thermal energy for heating is already reserved, the amount of decrease of the output is increasable/increased without deteriorating the heating capacity.

Here, an integration period for calculating the integration value may be set as a so-far period that is a period of time between a specific previous time and a present time or as a past predetermined period that is a preset period of time in the past. For example, in case that an ON (operation)/OFF (stop) of the engine2has been repeated for a couple of times so far, the output of the electric heater in not only the immediately-before engine operation time but also previous engine operation times may have an influence on the room temperature or the component temperature, thereby the output of the electric heater in such engine operation times may be included in the integration calculation as the so-far period.

Next, with reference to a time chart inFIGS. 10A and 10B, the electric heater output control in the second embodiment is described.

FIG. 10Bshows an ON/OFF state of the engine2andFIG. 10Ashows a change of the output of the electric heater7according to such an ON/OFF of the engine2, respectively using a solid line for the present disclosure case and a dashed line for the no control case.

When the control of the present disclosure is not used, the output of the electric heater7is not affected by an ON/OFF of the engine2.

When the control of the present disclosure is used, in the period of time t6-time t7during which the engine2stops, the output of the electric heater7decreases compared with the no control case.

In the period of time t5-time t6and time t7-time t8during which the engine2operates, the output of the electric heater7becomes large compared with the stop time of the engine2. Therefore, the output of the electric heater changes in a stepwise manner at the engine2ON/OFF switching times.

As mentioned above, in the second embodiment, the hybrid vehicle102has a configuration in which the electric heater7is connected to the sub-battery6side of the DC-DC converter5. In such a configuration, when SOC of the main battery4is lower than the threshold value α, in addition to the sub-battery voltage control, the HV-ECU80performs the electric heater output control.

Just like the sub-battery voltage control, in the engine non-operation time, i.e., in an EV travel time, the electric heater output control sets the output of the electric heater7to be smaller than the normal value that is used in the normal time, and, in the engine operation time, sets the output of the electric heater7to be greater than the set value in the engine non-operation time. In such manner, while preventing the lowering of the heating capacity, the electric power consumption amount in the EV travel time is reduced compared with the normal time.

Further, in the engine operation time, the output of the electric heater7is set to be greater as the drive load of the vehicle falls to be low, and the electric power supplied to the electric heater7is increased from the DC-DC converter5in the engine operation time, as shown inFIG. 8. Therefore, the engine load is raised in such manner when the drive load of the vehicle is low, which achieves an improvement of the engine efficiency as a result.

Further, as shown inFIG. 9, the amount of decrease of the output of the electric heater7in the engine non-operation time, i.e., in the EV travel time, is determined, based on the integration value of the amount of increase of the output of the electric heater7in the engine operation time.

Thereby, the electric power consumption in the EV travel time is reduced appropriately, taking into consideration a reservation of heating capacity.

In addition, as shown inFIG. 6, the same effect as the first embodiment is achieved because the configuration of the present embodiment, in which the electric power to be supplied to the DC-DC converter5is procured solely from the regenerated electric power Preg regenerated by the motor-generator31while controlling the discharge amount Pmb from the main battery4to zero.

The configuration of the hybrid vehicle to which the hybrid vehicle control unit of the third embodiment of the present disclosure is applied is described with reference toFIG. 11.

As shown inFIG. 11, in a hybrid vehicle103, the electric heater7is connected to the main battery4side of the DC-DC converter5, and the regenerated electric power from the motor-generator31or the electric power discharged from the main battery4is supplied thereto, for heating the compartment or for warming the vehicle component.

As such, the electric heater7may be connected not only on the sub-battery6side but on the main battery4side of the DC-DC converter5.

However, as described in the second embodiment, the electric heater output control, in which the output of the electric heater7is changed depending on the engine operation/non-operation time when SOC of the main battery4is lower than the threshold value α, is based on an assumption that the electric heater7is connected on the sub-battery6side (of the converter5).

Therefore, a characteristic control of the third embodiment is fundamentally the same as the control of the first embodiment.

As shown inFIGS. 1,6,11, the hybrid vehicle which has the hybrid vehicle control unit of the present disclosure is typically configured to have one motor-generator31. However, the hybrid vehicle control unit of the present disclosure may be applicable to the hybrid vehicle that has an engine and two motor-generators together with a power split mechanism that distributes the driving force from the engine, i.e., to a so-called series-parallel hybrid vehicle.

Further, the motor-generator, which generates electric power by receiving the driving force from the engine, may be replaced with a fuel cell, which generates electric power by causing a chemical reaction between hydrogen and oxygen. In such a case, the “engine” in the claims may be replaced with the “fuel cell.”

As mentioned above, the present disclosure is not limited to the above-described embodiments, but is variously implemented as long as the gist of the disclosure is realized and achieved therein.