Patent Description:
Recently, a hybrid vehicle and an electric vehicle are drawing a great deal of attention as an eco-friendly vehicle. Then, the hybrid vehicle is partially put into a practical use.

This hybrid vehicle is a vehicle having a DC power source, an inverter and a motor driven by the inverter as a power source in addition to a conventional engine. That is, while the power source is obtained by driving the engine, direct voltage from the DC power source is converted into alternating voltage by the inverter and the power source is obtained by rotating the motor by the converted alternating voltage. The electric vehicle is a vehicle having a DC power source, an inverter and a motor driven by the inverter as a power source.

In general, a secondary battery is installed in the hybrid vehicle or the electric vehicle as the DC power source. By demonstrating a performance of the secondary battery more, a performance of the vehicle can be improved.

For example, <CIT> discloses an output management device for a secondary battery. In a case where the secondary battery is required to output exceeding a rated output, this output management device sets a quantity of the output and a duration time for the output based on a temperature of the secondary battery.

In general, internal resistance of a battery has dependence on the temperature. For example, the internal resistance of the battery is increased as a temperature around the battery is lowered. When the internal resistance of the battery is increased, a change in battery voltage relative to a change in electric power inputted to or outputted from the battery is increased. When the change in the battery voltage is increased, the battery voltage may exceed an upper limit value of a use range or fall below a lower limit value of the use range. However, <CIT> does not particularly disclose such a problem.

Document <CIT> discloses a vehicle including a high-voltage battery that outputs driving power for driving said vehicle. A state of charge SOC, an input limit, and an output limit of the high-voltage battery are computed by a motor ECU from the battery current, the battery voltage, and the battery temperature, which are measured by an electric current sensor, a voltage sensor, and a temperature sensor connected to the power line from the high-voltage battery, and are received from the motor ECU by communication. Computing the input and output limits sets base values of the input limit and the output limit corresponding to the measured battery temperature.

Document <CIT> discloses vehicle and method of operating a vehicle including a motor that supplies a driving force to a wheel, a battery that supplies electric power to the motor and receives regenerative electric power from the motor and a controller that detects a state of the battery and sets, based on a detected state of the battery and outside air temperature, a first upper limit value and a first lower limit value for a voltage value and an electric current value that is output from the battery to the motor, and a second upper limit value and second lower limit value for the voltage value and the electric current value that is input from the regenerative electric power to the battery.

Document <CIT> discloses state of charge calculation device includes an ammeter for detecting charge and discharge currents of a secondary battery, a state detection sensor for detecting a start time of discharge from the secondary battery to an engine, a battery electronic control unit (ECU) for calculating a state of charge of the secondary battery. The battery ECU of this state of charge calculation device calculates the state of charge of the secondary battery, based on the current and voltage detected at the time when discharge starts. The battery ECU specifies a correction gain used in the calculation of a SOC correction amount, based on a temperature of the secondary battery detected by a temperature sensor.

An object of the present invention is to provide an input/output controller for a secondary battery capable of properly controlling battery voltage in accordance with a battery temperature, and a vehicle provided with the above device.

According to an aspect of the present invention, there is provided an input/output controller for a secondary battery as defined in claims <NUM> to <NUM>. According to another aspect of the present invention, there is provided a vehicle as defined in claim <NUM>.

Therefore, according to the present invention, the battery voltage can be properly controlled in accordance with the battery temperature.

It should be noted that the same or corresponding parts in the drawings are given the same reference symbols and description thereof will not be repeated.

<FIG> is a schematic diagram showing a configuration of a vehicle provided with an input/output controller for a secondary battery according to the present embodiment.

With reference to <FIG>, a hybrid vehicle <NUM> includes front wheels 20R and <NUM>, rear wheels 22R and <NUM>, an engine <NUM>, a planetary gear <NUM>, a differential gear <NUM> and gears <NUM> and <NUM>.

Hybrid vehicle <NUM> further includes a battery <NUM> arranged on the rear side of the vehicle, a voltage boosting unit <NUM> for boosting voltage of direct current power outputted by battery <NUM>, an inverter <NUM> for supplying or receiving the direct current power to or from voltage boosting unit <NUM>, a motor generator MG1 for receiving mechanical power of engine <NUM> via planetary gear <NUM> and generating electric power, and a motor generator MG2 having a rotation shaft connected to planetary gear <NUM>. Inverter <NUM> is connected to motor generators MG1 and MG2 so as to convert alternating current power and the direct current power from a voltage boosting circuit.

Planetary gear <NUM> has first to third rotation shafts. The first rotation shaft is connected to engine <NUM>, the second rotation shaft is connected to motor generator MG1, and the third rotation shaft is connected to motor generator MG2.

Gear <NUM> is attached to this third rotation shaft. By driving gear <NUM>, this gear <NUM> transmits the mechanical power to differential gear <NUM>. Differential gear <NUM> transmits the mechanical power received from gear <NUM> to front wheels 20R and <NUM>, and also transmits rotation force of front wheels 20R and <NUM> to the third rotation shaft of the planetary gear via gears <NUM> and <NUM>.

Planetary gear <NUM> plays a role of dividing the mechanical power among engine <NUM> and motor generators MG1 and MG2. That is, when rotation of two of three rotation shafts of planetary gear <NUM> is determined, rotation of the remaining one rotation shaft is inevitably determined. Therefore, while engine <NUM> is operated in the most efficient area, electric generating capacity of motor generator MG1 is controlled so as to drive motor generator MG2. Thereby, vehicle speed is controlled and a wholly energy-efficient vehicle is realized.

Battery <NUM> serving as a DC power source is, for example, formed by a nickel hydride secondary battery, a lithium ion secondary battery or the like for supplying the direct current power to voltage boosting unit <NUM> and being charged by the direct current power from voltage boosting unit <NUM>.

Voltage boosting unit <NUM> boosts direct voltage received from battery <NUM>, and supplies the boosted direct voltage to inverter <NUM>. Inverter <NUM> converts the supplied direct voltage into alternating voltage, and controls drive of motor generator MG1 at the time of starting the engine. After starting the engine, the alternating current power generated by motor generator MG1 is converted into the direct current by inverter <NUM> and converted into voltage suitable for charging battery <NUM> by voltage boosting unit <NUM> so that battery <NUM> is charged.

Inverter <NUM> drives motor generator MG2. Motor generator MG2 assists engine <NUM> and drives front wheels 20R and <NUM>. At the time of braking, the motor generator performs a regenerating operation and converts rotation energy of the wheels into electric energy. The obtained electric energy is returned to battery <NUM> via inverter <NUM> and voltage boosting unit <NUM>.

System main relays <NUM> and <NUM> are provided between voltage boosting unit <NUM> and battery <NUM>, and high voltage is cut off at the time of not operating the vehicle.

Battery <NUM> includes internal resistance Rb. In general, internal resistance Rb has dependency on a temperature. For example, internal resistance Rb is increased as the temperature is lowered.

Hybrid vehicle <NUM> further includes a temperature sensor <NUM> and a voltage sensor <NUM> attached to battery <NUM>, and a control unit <NUM> for controlling engine <NUM>, inverter <NUM> and voltage boosting unit <NUM> in accordance with outputs of temperature sensor <NUM> and voltage sensor <NUM>. Temperature sensor <NUM> detects and transmits a temperature T of the battery to control unit <NUM>. Voltage sensor <NUM> detects and transmits voltage between terminals of battery <NUM> (battery voltage VB) to control unit <NUM>.

Control unit <NUM> receives temperature T and battery voltage VB and sets a limit value of electric power to be inputted to or outputted from battery <NUM>. Control unit <NUM> changes a change ratio of the limit value relative to a change in battery voltage VB in accordance with temperature T.

Specifically, control unit <NUM> decreases the change ratio of the limit value relative to the change in battery voltage VB as temperature T is lowered, and increases the change ratio of the limit value relative to the change in battery voltage VB as temperature T is raised. Thereby, even when the temperature of battery <NUM> is changed, battery voltage VB can be brought closer to target voltage.

<FIG> is a block diagram of an input/output control system of battery <NUM> included in control unit <NUM> of <FIG>. It should be noted that the input/output control system shown in <FIG> may be realized by software or by hardware.

With reference to <FIG>, an input/output control system <NUM> in the present embodiment forms a feedback control system. Input/output control system <NUM> includes a target value generating unit <NUM>, a subtracting unit <NUM>, a PI control unit <NUM>, an initial value setting unit <NUM>, a final value determining unit <NUM>, and an input/output processing unit <NUM>.

Target value generating unit <NUM> generates and outputs target voltage VB0 serving as a target value of the voltage of battery <NUM>. Target voltage VB0 may be a fixed value or, for example, a value to be set in accordance with a deterioration state of battery <NUM>.

Subtracting unit <NUM> subtracts battery voltage VB from target voltage VB0 and outputs a subtracting result thereof to PI control unit <NUM>.

PI control unit <NUM> performs proportional integral operation taking a deviation between target voltage VB0 and battery voltage VB as an input and outputs an operation result thereof to final value determining unit <NUM>. PI control unit <NUM> changes control gain (hereinafter also referred to as the "feedback gain") in accordance with temperature T. A configuration of PI control unit <NUM> will be described later.

Initial value setting unit <NUM> sets an initial value of a limit value Win of electric power inputted to battery <NUM> (initial value Win0) and an initial value of a limit value Wout of electric power outputted from battery <NUM> (initial value Wout0). A method of setting initial values Win0 and Wout0 is not particularly limited. For example, initial value setting unit <NUM> may preliminarily store a map for correspondence between battery voltage VB and initial value Win0 and a map for correspondence between battery voltage VB and initial value Wout0. In this case, initial value setting unit <NUM> determines initial value Win0 or initial value Wout0 based on battery voltage VB detected by voltage sensor <NUM> of <FIG>.

Final value determining unit <NUM> receives initial value Win0 from initial value setting unit <NUM> and the operation result of PI control unit <NUM>. Final value determining unit <NUM> compensates initial value Win0 with using the operation result of PI control unit <NUM> and determines limit value Win of the electric power to be inputted to battery <NUM>.

Similarly, final value determining unit <NUM> receives initial value Wout0 from initial value setting unit <NUM> and the operation result of PI control unit <NUM>. Final value determining unit <NUM> compensates initial value Wout0 with using the operation result of PI control unit <NUM> and determines limit value Wout of the electric power to be inputted to battery <NUM>. That is, PI control unit <NUM> changes a compensation amount of limit value Win and a compensation amount of limit value Wout of the electric power in accordance with the temperature.

Input/output processing unit <NUM> charges battery <NUM> based on limit value Win given from final value determining unit <NUM>. Electricity is discharged from battery <NUM> based on limit value Wout given from final value determining unit <NUM>. Input/output processing unit <NUM> operates voltage boosting unit <NUM>, inverter <NUM> and engine <NUM> shown in <FIG> so that battery <NUM> is charged or the electric power is discharged from battery <NUM>.

<FIG> is a diagram showing a configuration of PI control unit <NUM> of <FIG>.

With reference to <FIG>, PI control unit <NUM> includes a proportional operation unit <NUM>, an integral operation unit <NUM>, a coefficient setting unit <NUM>, and an adding unit <NUM>. Integral operation unit <NUM> includes an amplifying unit <NUM> and an integrating unit <NUM>.

Proportional operation unit <NUM> operates a proportional value of the deviation (VBO - VB) with using proportional gain (kP(T) × kPD) determined by the product of a coefficient kP(T) to be inputted and predetermined gain kPD. Integral operation unit <NUM> operates an integral value of the deviation (VBO - VB) with using integral gain (kI(T) × kID) determined by the product of a coefficient kI(T) to be inputted and predetermined gain kID.

kPD and kID are gain when a battery temperature is a predetermined temperature (such as -<NUM>) (hereinafter, referred to as the "default"). kP(T) and kI(T) are coefficients changed in accordance with the temperature. Therefore, the proportional gain in proportional operation unit <NUM> and the integral gain in integral operation unit <NUM> are changed in accordance with the temperature.

Amplifying unit <NUM> amplifies the deviation (VBO - VB) with using integral gain (kI(T) × kID). Integrating unit <NUM> time-integrates an output of amplifying unit <NUM>. It should be noted that integrating unit <NUM> may be provided in a previous stage of amplifying unit <NUM>.

Coefficient setting unit <NUM> changes coefficients kP(T) and kI(T) in accordance with temperature T. For example, coefficient setting unit <NUM> refers to a map shown in <FIG> so as to determine coefficients kP(T) and kI(T). Coefficient setting unit <NUM> outputs coefficients kP(T) and kI(T) to proportional operation unit <NUM> and integral operation unit <NUM> respectively.

Adding unit <NUM> adds an operation result (proportional value) of proportional operation unit <NUM> and an operation result (integral value) of integral operation unit <NUM>. An operation result in adding unit <NUM> is an output of PI control unit <NUM>.

<FIG> is a diagram for illustrating a map referred by coefficient setting unit <NUM> of <FIG>.

With reference to <FIG>, when the battery temperature is a predetermined value TL (-<NUM> in the above example), both coefficients kP(T) and kI(T) are <NUM>. As the battery temperature is raised from predetermined value TL, coefficients kP(T) and kI(T) are increased. It should be noted that a change ratio of coefficients kP(T) and kI(T) relative to a change in the temperature is not limited to an inclination of a curve shown in <FIG> but properly determined in accordance with a characteristic of battery <NUM>, a response property in the feedback control system or the like.

Next, an effect by the input/output controller of the present embodiment will be described. It should be noted that hereinafter, a case where the electric power is taken out from battery <NUM> will be mainly described.

<FIG> is a diagram for illustrating a relationship between discharged electric power of battery <NUM> and battery voltage VB.

With reference to <FIG>, curves c1 to c3 are curves showing the relationship between the electric power of battery <NUM> at the time of electric discharge and battery voltage VB. Curves c1 and c3 show the relationship between the discharged electric power of battery <NUM> and battery voltage VB in a state where the internal resistance of the electric battery is relatively low and in a state where the internal resistance of the electric battery is relatively high respectively. Curve c2 shows the relationship between the discharged electric power of battery <NUM> and battery voltage VB in a middle state between the state where the internal resistance of the electric battery is relatively low and the state where the internal resistance of the electric battery is relatively high.

In any of curves c1 to c3, as the discharged electric power is increased, battery voltage VB is lowered from voltage VO serving as open circuit voltage.

Next, the change in the temperature in a minute change amount of electric power P relative to a minute change amount of battery voltage VB will be described. When electromotive force of battery <NUM> shown in <FIG> is Eo, a resistance value of internal resistance Rb is R, and current passing through battery <NUM> is I, battery voltage VB is represented as (Eo - I × R). Electric power P outputted from battery <NUM> is represented as I × VB. Therefore, a relationship shown in the following equation (<NUM>) is established with regard to electric power P and battery voltage VB.

Here, the change amount of electric power P relative to the change amount of battery voltage VB is dP/dV. dP/dV is equal to a result of differentiating electric power P shown in equation (<NUM>) with respect to battery voltage VB. Therefore, dP/dV is represented as the following equation (<NUM>).

In general, as the battery temperature is lowered, the internal resistance of the battery is increased. That is, in a case where (Eo - VB) is fixed, as the battery temperature is lowered, dP/dV is decreased. Conversely, this indicates that as the battery temperature is lowered, (dV/dP) is increased.

Curves c1 to c3 show a relationship of dV/dP mentioned above. In <FIG>, the minute change amount of electric power P is ΔP. In curves c1 to c3, the change amounts of battery voltage VB corresponding to ΔP are ΔV1, ΔV2 and ΔV3 respectively. A relationship of ΔV1 < ΔV2 < ΔV3 is established with regard to ΔV1, ΔV2 and ΔV3. Therefore, a relationship of (ΔV1/ΔP) < (ΔV2/ΔP) < (ΔV3/ΔP) is established. This indicates that as the temperature of battery <NUM> is lowered, sensitivity of battery voltage VB is increased relative to the change in electric power P.

<FIG> is a diagram for illustrating a possible problem caused in a case where the feedback gain in PI control unit <NUM> of <FIG> is set to be constant with the temperature.

With reference to <FIG>, provided that the discharged electric power of the battery is controlled so that the discharged electric power of the battery is changed by ΔP around Po. Here, voltage VL is a lower limit value of battery voltage VB determined based on, for example, a performance of the battery, a use state (deterioration state) of the battery or the like. By maintaining battery voltage VB higher than voltage VL, for example, over-discharge of the battery can be prevented.

In curves c1 and c2, even when the discharged electric power of the battery is changed by ΔP, battery voltage VB is always higher than voltage VL. On the other hand, in curve c3, the change in battery voltage VB relative to the change in the discharged electric power is large. Therefore, when the discharged electric power of the battery is changed by ΔP, battery voltage VB is lower than voltage VL.

<FIG> is a diagram for illustrating an effect in a case where the feedback gain in PI control unit <NUM> of <FIG> is changed in accordance with the temperature.

With reference to <FIG>, ΔP1, ΔP2 and ΔP3 show change amounts of the discharged electric power of battery <NUM> when battery voltage VB is changed from target voltage VB0 to voltage V1 in curves c1 to c3 respectively.

With reference to <FIG> and <FIG>, in a case where the internal resistance is small, that is, in a case where the battery temperature is high, the feedback gain in PI control unit <NUM> is set to be large. In this case, the feedback gain is set so that the discharged electric power of the battery is changed along curve c1 so to speak.

In the case where the battery temperature is high, the internal resistance of the battery is decreased. Therefore, the change in battery voltage VB relative to the change in outputted electric power of the battery is small. In the present embodiment, in the case where the battery temperature is high, the feedback gain is increased so as to increase the compensation amount of limit value Wout. Thereby, the change in limit value Wout can be increased. Even when the change in battery voltage VB is small, the response property of input/output control system <NUM> can be enhanced. Therefore, battery voltage VB can be brought closer to target voltage VB0 for a short time.

On the other hand, in a case where the internal resistance is large, that is, in a case where the battery temperature is low, the feedback gain in PI control unit <NUM> is set to be small. In the case where the battery temperature is low, the change in battery voltage VB relative to the change in the outputted electric power of the battery is large. Therefore, the feedback gain relative to the deviation between target voltage VB0 and battery voltage VB (that is, VB0 - VB) is increased more than necessary, for example, overshoot of battery voltage VB, undershoot of battery voltage VB, hunting of battery voltage VB or the like may be caused.

In the present embodiment, in the case where the battery temperature is low, the feedback gain is decreased. Thereby, the compensation amount of limit value Wout is decreased and the change in limit value Wout relative to the change in battery voltage VB can be decreased. Thereby, since fluctuation of battery voltage VB can be decreased, the overshoot, the undershoot, the hunting and the like of battery voltage VB can be prevented.

As a result, in the present embodiment, in a case where the electric power is taken out from the battery, the electric power to be outputted from the battery can be controlled so that the lower limit value of battery voltage VB (voltage V1) is higher than voltage VL. That is, the voltage of the battery can be properly controlled in accordance with the battery temperature.

<FIG> is a flowchart showing processing performed by input/output control system <NUM> shown in <FIG>. The processing of this flowchart is executed whenever a predetermined condition is met, or at a fixed intervals.

With reference to <FIG> and <FIG>, input/output control system <NUM> obtains a value of battery voltage VB and a value of temperature T (Step S1). Next, with reference to <FIG> and <FIG>, processing of Steps S2 and S3 will be described.

In Step S2, coefficient setting unit <NUM> calculates coefficients kP(T) and kI(T) based on temperature T and the map (refer to <FIG>).

In Step S3, PI control unit <NUM> sets the feedback gain by multiplying default gain by the coefficient. Specifically, in Step S3, proportional operation unit <NUM> sets the proportional gain by multiplying the default gain (gain kPD) by coefficient kP(T). Similarly, in Step S3, integral operation unit <NUM> sets the integral gain by multiplying the default gain (gain kID) by coefficient kI(T).

With reference to <FIG> and <FIG> again, processing of Step S4 will be described. In Step S4, input/output control system <NUM> executes feedback control (PI control) based on a voltage exceeding amount (that is, deviation (VBO - VB)). When the processing of Step S4 is finished, the entire processing is returned to Step S1 again.

It should be noted that not only in a case where the electric power is outputted from the battery, but also in a case where the electric power is inputted to the battery, the input/output controller of the present embodiment can be applied.

<FIG> is a diagram for illustrating a relationship between charged electric power of battery <NUM> and battery voltage VB.

With reference to <FIG>, curves c4 to c6 are curves showing the relationship between the electric power of battery <NUM> at the time of electric charge and battery voltage VB. Curves c4 and c6 show the relationship between the charged electric power of battery <NUM> and battery voltage VB in a state where the internal resistance of the battery is relatively low and in a state where the internal resistance of the battery is relatively high respectively. Curve c5 shows the relationship between the charged electric power of battery <NUM> and battery voltage VB in a middle state between the state where the internal resistance of the battery is relatively low and the state where the internal resistance of the battery is relatively high.

In any of curves c4 to c6, as the charged electric power is increased, battery voltage VB is increased. At the time of charging battery <NUM>, as the internal resistance of battery <NUM> is raised, a change ratio of battery voltage VB relative to the change in the charged electric power is increased.

Voltage VH is an upper limit value of battery voltage VB determined based on, for example, the performance of the battery, the use state (deterioration state) of the battery or the like. By maintaining battery voltage VB lower than voltage VH, for example, over-charge of the battery can be prevented. ΔP4, ΔP5 and ΔP6 show change amounts of the charged electric power when battery voltage VB is changed from voltage V2 to voltage V3 in curves c4 to c<NUM> respectively. It should be noted that target voltage VB0 is between voltage V2 and voltage V3.

In a case where the internal resistance is small, that is, in a case where the battery temperature is high, the feedback gain in PI control unit <NUM> of <FIG> is set to be large. On the other hand, in a case where the internal resistance is high, that is, in a case where the battery temperature is low, the feedback gain in PI control unit <NUM> is set to be small.

In a case where the battery temperature is high, the feedback gain is increased. Therefore, the compensation amount of limit value Win is increased. As a result, the change in the charged electric power is increased. Therefore, even when the change in battery voltage VB is small, the response property of input/output control system <NUM> can be enhanced. On the other hand, in a case where the battery temperature is low, the change in battery voltage VB relative to the change in the outputted electric power of the battery is increased but the feedback gain is decreased. In this case, since the compensation amount of limit value Win is decreased, the change in limit value Win relative to the change in battery voltage VB can be decreased. Thereby, the overshoot, the undershoot, the hunting and the like of battery voltage VB can be prevented.

That is, as well as a case where the electric power is taken out from battery <NUM>, in a case where battery <NUM> is charged, the fluctuation of battery voltage VB relative to the electric power inputted to the battery can be suppressed (battery voltage VB can be brought closer to target voltage VB0) not in accordance with the battery temperature.

As a result, the electric power to be inputted to the battery can be controlled so that the upper limit value of battery voltage VB (voltage V3) is lower than voltage VH. In such a way, according to the present embodiment, the voltage of the battery can be properly controlled in accordance with the battery temperature.

It should be noted that in the present embodiment, a flowchart showing processing in a case where battery <NUM> is charged is the same as the flowchart shown in <FIG>. Therefore, description thereof will not be repeated.

With reference to <FIG>, the input/output controller for the secondary battery in the present embodiment will be comprehensively described. The input/output controller for the secondary battery is provided with temperature sensor <NUM> detecting the battery temperature of battery <NUM> (temperature T), voltage sensor <NUM> detecting the battery voltage of battery <NUM> (battery voltage VB), and control unit <NUM> receiving temperature T detected by temperature sensor <NUM> and battery voltage VB detected by voltage sensor <NUM> and setting the limit value (Win/Wout) to be inputted to or outputted from battery <NUM>. Control unit <NUM> changes the change ratio of the limit value relative to battery voltage VB in accordance with temperature T.

With reference to <FIG>, preferably, control unit <NUM> includes the operation unit (PI control unit <NUM>) performing control operation based on the deviation between target voltage VB0 of battery <NUM> and battery voltage VB. PI control unit <NUM> changes the control gain used for the control operation in accordance with temperature T. Control unit <NUM> further includes initial value setting unit <NUM> setting the initial value (Win0/Wout0) of the limit value, and final value determining unit <NUM> determining the limit value (Win/Wout) based on the initial value of the limit value and the operation result of PI control unit <NUM>.

More preferably, PI control unit <NUM> determines the control gain so that the control gain is decreased as temperature T is lowered.

With reference to <FIG>, more preferably, the control operation of the operation unit (PI control unit <NUM>) is the proportional integral operation. The control gain includes the proportional gain and the integral gain. PI control unit <NUM> has coefficient setting unit <NUM>, proportional operation unit <NUM>, integral operation unit <NUM>, and adding unit <NUM>. Proportional operation unit <NUM> sets coefficients kP(T) and kI(T) (first and second coefficients) in accordance with temperature T. Proportional operation unit <NUM> sets the proportional gain by multiplying coefficient kP(T) by fixed gain kPD not in accordance with temperature T and operates the proportional value of the deviation with using the proportional gain. Integral operation unit <NUM> sets the integral gain by multiplying coefficient kI(T) by fixed gain kID not in accordance with temperature T and operates the integral value of the deviation with using the integral gain. Adding unit <NUM> adds the proportional value and the integral value.

In such a way, in the present embodiment, the voltage of the battery can be properly controlled in accordance with the battery temperature. Therefore, an electric storage performance and a discharge performance of the battery can be sufficiently exhibited.

According to the present embodiment, hybrid vehicle <NUM> is provided with the input/output controller for the secondary battery described in any of the above descriptions and battery <NUM>. Since the electric storage performance and the discharge performance of the battery can be sufficiently exhibited by the input/output controller, a performance of the vehicle can be sufficiently exhibited.

It should be noted that the above descriptions show an example that the input/output controller for the secondary battery of the present embodiment is applied to a series/parallel type hybrid system capable of dividing and transmitting the mechanical power of the engine into a wheel axle and a generator by a power split device. However, the present invention can be also applied to a series type hybrid vehicle of using an engine only for driving a generator and generating drive force of a wheel axle only by a motor using electric power generated by the generator or an electric vehicle traveling only by a motor.

Claim 1:
An input/output controller for a secondary battery, comprising:
a temperature detecting unit (<NUM>) configured to detect a battery temperature of said secondary battery;
a voltage detecting unit (<NUM>) configured to detect battery voltage of said secondary battery; and
a setting unit (<NUM>) configured to receive said battery temperature detected by said temperature detecting unit (<NUM>) and said battery voltage detected by said voltage detecting unit (<NUM>);
characterized in that
said setting unit (<NUM>) is further configured to set a limit value of electrical power to be inputted to or outputted from the secondary battery based on a difference between said battery voltage and a target battery voltage, and in that
said setting unit (<NUM>) is further configured to change a change ratio of said limit value of electrical power in accordance with said battery temperature.