JP7560993B2 - Heat retention control device and heat retention control method - Google Patents

Description

The disclosed embodiments relate to a heat retention control device and a heat retention control method.

Conventionally, LiBs (Lithium-Ion rechargeable batteries) are known that are installed in HEVs (Hybrid Electric Vehicles) and EVs (Electric Vehicles) as, for example, auxiliary batteries.

Such LiBs contain multiple cells, but because the capacity, internal resistance, self-discharge rate, etc. of each cell are non-uniform, there is variation in the voltage of each cell (hereinafter referred to as "cell voltage"). Therefore, to eliminate such variation, equalization (so-called cell balancing) is usually performed using an equalization circuit.

In addition, in cell balancing, by appropriately heating the LiBs, the difference in self-charging speed between the cells can be increased, and the voltage difference between the cells can be reduced as a result of self-charging, making it possible to effectively eliminate variations. Therefore, a technology has been proposed in which a heating device such as a heater or fan is provided to warm the LiBs, and cell balancing is performed while the LiBs are heated by the heating device (see, for example, Patent Document 1).

JP 2008-236910 A

However, the above-mentioned conventional technology has room for further improvement in terms of keeping LiBs warm while reusing electricity.

For example, when the vehicle's ignition is off and the vehicle is not running, the supply of power to the vehicle's various devices, including the heating device mentioned above, is stopped, so the LiB cannot be heated, or at least cannot be kept warm. Therefore, it takes time for the LiB to warm up to a suitable temperature immediately after the vehicle is started.

On the other hand, the capacitors in the equalization circuit may still have a charge remaining in them immediately after the vehicle's ignition is turned off. However, this charge will naturally discharge over time, resulting in wasted power.

One aspect of the embodiment has been made in consideration of the above, and aims to provide a heat retention control device and a heat retention control method that can keep a battery warm while reusing power.

The heat retention control device according to one aspect of the embodiment includes an acquisition unit and a power supply control unit. The acquisition unit acquires the state of a heating device that heats a battery having a plurality of cells and that is provided so that cell balancing can be performed by an equalization circuit, and the state of the equalization circuit. When it is determined based on the states acquired by the acquisition unit that power supply to the heating device has stopped and that power has been stored in a capacitor of the equalization circuit, the power supply control unit supplies the power stored in the capacitor to the heating device.

According to one aspect of the embodiment, it is possible to keep the battery warm while reusing power.

FIG. 1 is a diagram showing an example of the configuration of a general equalization circuit. FIG. 2 is a schematic explanatory diagram of a heat retention control method according to the embodiment. FIG. 3 is a block diagram showing an example of the configuration of a heat retention control system according to the embodiment. FIG. 4 is a block diagram showing an example of the configuration of a heat retention control device according to the embodiment. FIG. 5 is a diagram illustrating conditions for supplying the power stored in the capacitor to the heater. FIG. 6 is a flowchart showing a processing procedure executed by the control device according to the embodiment.

Below, the embodiments of the heat retention control device and heat retention control method disclosed in the present application will be described in detail with reference to the attached drawings. Note that the present invention is not limited to the embodiments shown below.

The following description will be given by taking as an example a case where the battery is an LiB installed in a vehicle as an auxiliary battery. The following description will first use FIG. 1 to explain a typical configuration example of an equalization circuit 2', and then use FIG. 2 and subsequent figures to specifically explain a configuration example of the heat retention control system 1 according to this embodiment.

First, a configuration example of a general equalization circuit 2' will be described with reference to FIG. 1. FIG. 1 is a diagram showing a configuration example of a general equalization circuit 2'.

As shown in FIG. 1, the equalization circuit 2' includes capacitors C1 to C4 and _Cin , diodes D1 to D4, inductors L1 to L4 and _Lin , and a switch Q.

The capacitors C1 to C4 are equalizing capacitors, the capacitor _Cin is an input capacitor, and the inductor _Lin is an input inductor.

The equalization circuit 2' converts the voltage input from cells B1 to B4 of LiB3 to capacitor _Cin by switching switch Q, and outputs it to the cell with the lowest voltage among cells B1 to B4. Hereinafter, the circuit composed of capacitor _Cin , switch Q, and inductor _Lin will be referred to as the input circuit, and the circuit composed of capacitors C1 to C4, diodes D1 to D4, and inductors L1 to L4 will be referred to as the output circuit.

Cells B1 to B4 are connected in series, and the first to fourth diode-inductor circuits, consisting of diode D1 and inductor L1, diode D2 and inductor L2, diode D3 and inductor L3, and diode D4 and inductor L4, are connected in parallel to each of the cells.

In each diode-inductor circuit, the inductor is connected to the anode side of the diode, and each diode-inductor circuit is connected in series so as not to block current of the polarity flowing from each inductor to the diode.

In addition, capacitors C1 to C4 are connected between the midpoints of the diodes and inductors in the first to fourth diode-inductor circuits and the input circuit, respectively. Cell B1 is grounded.

Note that the capacitors C1 to C4, the diodes D1 to D4, and the inductors L1 to L4 do not need to be identical elements, and the capacitance of each capacitor, the characteristics of each diode, and the inductance of each inductor may be different from each other. Similarly, the capacitances of the cells B1 to B4 of LiB3 may also be different from each other.

The number of cells, diode-inductor circuits, and equalizing capacitors is not limited to four and may be any number equal to or greater than two. In addition, in FIG. 1, there is only one switch, switch Q, but any control switch may be added for the purpose of customizing operation, etc.

Here, the cell voltages of the cells B1 to B4 are V1 to V4. The capacitance of the cells B1 to B4 is sufficiently large compared to the capacitance of the capacitors C1 to C4, and V1 to V4 are considered to be constant over one switching period of the switch Q. The time average of the voltage applied to the capacitor _Cin (the total voltage of the voltages applied to the cells B1 to B4) over the switching period is Vin (=V1+V2+V3+V4). The time average of the current flowing through the inductor _Lin is _ILin .

In such an equalization circuit 2', for example, if the cell with the lowest cell voltage among cells B1 to B4 is cell B1, the current that flows from cells B1 to B4 to the input circuit during one switching period flows via inductor _Lin to the output circuit including capacitors C1 to C4, is converted, and then preferentially output to cell B1 with the lowest voltage.

In terms of energy transfer, the input power transmitted from the input circuit to the output circuit is _Vin x _ILin , and this input power is converted in the output circuit and transmitted preferentially to the cell B1 with the lowest voltage. At this time, the current flowing into cell B1 is expressed as ( _Vin x _ILin )/V*, assuming that the loss in the equalization circuit 2' is zero. Here, V* is the voltage of the lowest voltage cell, and is equal to V1 in this example.

When power is supplied from the output circuit to cell B1, which has the lowest voltage, the cell voltage of cell B1 rises, while the cell voltages of the other cells B2 to B4 fall as power is supplied to the equalization circuit 2'. As a result, the voltage difference between cell B1 and the other cells B2 to B4 gradually decreases over time, and eventually the voltages of all cells B1 to B4 become equal.

In the meantime, in cell balancing using this type of equalization circuit 2', there is known existing technology that aims to quickly eliminate variations in cell voltage by appropriately warming the LiB3 using a heating device such as a heater or fan.

However, when using existing technology, for example, when the vehicle's ignition is off and the vehicle is not running, the supply of power to the vehicle's various devices, including the heating device described above, is stopped, so LiB3 cannot be heated, or at least cannot be kept warm. Therefore, it takes time for LiB3 to warm up to an appropriate temperature immediately after the vehicle is started.

On the other hand, the capacitors C1 to C4 included in the equalization circuit 2' may still have a charge remaining in them immediately after the vehicle's ignition is turned off. However, this charge is naturally discharged over time, resulting in a waste of power.

Therefore, in the heat retention control method according to the embodiment, when the power supply to the heater is stopped and power has been stored in the capacitors C1 to C4 of the equalization circuit 2', the power from those capacitors C1 to C4 is supplied to the heater.

Figure 2 is an overview diagram of a heat retention control method according to an embodiment. Specifically, as shown in Figure 2, a heat retention control system 1 according to an embodiment includes an equalization circuit 2, an LiB 3, and a heater 4. The heater 4 is an example of a heating device.

Using this heat retention control system 1, the heat retention control method according to the embodiment supplies the power stored in the capacitors C1 to C4 to the heater 4 when certain conditions are met.

The specified condition is when the power supply to the heater 4 is stopped and the capacitors C1 to C4 of the equalization circuit 2 are charged, as shown in FIG. 2.

As a result, even if the vehicle's ignition is turned off and heater 4 is no longer able to heat LiB3 using the normal power supply, it can still be powered by the power stored in capacitors C1 to C4, making it possible to keep LiB3 warm for at least longer than before.

In addition, the power stored in capacitors C1 to C4 is not wasted due to natural discharge. Therefore, according to the heat retention control method of the embodiment, it is possible to keep LiB3 warm while reusing power.

The predetermined conditions shown in FIG. 2 can be expressed as more detailed conditions #1 to #3. This will be explained later using FIG. 5.

In this way, in the heat retention control method according to the embodiment, when the power supply to the heater 4 is stopped and power has been stored in the capacitors C1 to C4 of the equalization circuit 2, the power from those capacitors C1 to C4 is supplied to the heater.

Therefore, according to the heat retention control method of the embodiment, it is possible to keep LiB3 warm while reusing electricity.

As shown in FIG. 2, the heat retention control system 1 may further include a heat storage material 5, for example, near the LiB3. This makes it possible to further improve the heat retention effect of the LiB3.

The following describes in more detail an example of the configuration of the heat retention control system 1 according to the embodiment. FIG. 3 is a block diagram showing an example of the configuration of the heat retention control system according to the embodiment. FIG. 4 is a block diagram showing an example of the configuration of the heat retention control device according to the embodiment.

Note that Figures 3 and 4 show only the components necessary to explain the features of this embodiment, and general components are omitted.

In other words, each component shown in Figures 3 and 4 is a functional concept, and does not necessarily have to be physically configured as shown. For example, the specific form of distribution and integration of each block is not limited to that shown, and all or part of it can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

In addition, in the explanation using Figures 3 and 4, the explanation of components that have already been explained may be simplified or omitted.

As shown in FIG. 3, the heat retention control system 1 includes an equalization circuit 2, an LiB 3, a heater 4, a power generation unit 6, an IG switch 7, a heat retention control device 10, and switches Q1 and Q2. The switch Q1 switches the connection between the heater 4 and the power generation unit 6. The switch Q2 switches the connection between the equalization circuit 2 and the heater 4.

Equalization circuit 2 differs from equalization circuit 2' described above in that each of capacitors C1 to C4 is connected to the connection path between equalization circuit 2 and switch Q2. LiB3 and heater 4 have already been explained, so their explanation will be omitted here.

The power generation unit 6 is a component having a power generation function, such as a motor generator, alternator, or battery mounted on a vehicle. When the power generation unit 6 is generating power, the switch Q1 is turned on and power is supplied to the heater 4. At this time, the switch Q2 is turned off by the heat retention control device 10. The IG switch 7 is an ignition switch.

The heat retention control device 10 acquires the state of the switch Q1 and the IG switch 7, as well as the state of the equalization circuit 2, and controls the on/off of the switch Q2 based on each acquired state.

As shown in FIG. 4, the heat retention control device 10 includes a control unit 11. The control unit 11 is a controller, and is realized, for example, by a CPU (Central Processing Unit) or MPU (Micro Processing Unit) executing various programs stored in a storage device inside the heat retention control device 10 using a RAM (Random Access Memory) as a working area. The control unit 11 can also be realized, for example, by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The control unit 11 has an acquisition unit 11a, a determination unit 11b, and a power supply control unit 11c, and realizes or executes the information processing functions and actions described below.

The acquisition unit 11a acquires the states of the power generation unit 6, the IG switch 7, and the switch Q1, as well as the state of the equalization circuit 2. The acquisition unit 11a also outputs each acquired state to the determination unit 11b.

The determination unit 11b determines whether or not a predetermined condition for supplying the power stored in the capacitors C1 to C4 to the heater 4 is met, based on each state acquired by the acquisition unit 11a. As already explained with reference to FIG. 2, such a predetermined condition is when the power supply to the heater 4 is stopped and the capacitors C1 to C4 of the equalization circuit 2 have already stored power.

These conditions will be explained in more detail. Figure 5 is an explanatory diagram of the conditions for supplying the power stored in capacitors C1 to C4 to heater 4.

The above-mentioned predetermined condition, i.e., when the power supply to the heater 4 is stopped and the capacitors C1 to C4 of the equalization circuit 2 are charged, is, for example, when the IG is off, as shown as "Condition #1" in Figure 5.

When the state of the IG switch 7 changes from IG ON to IG OFF, the determination unit 11b determines that the "condition #1" is met and immediately causes the power supply control unit 11c to turn on the switch Q2 and supply the power stored in the capacitors C1 to C4 to the heater 4.

The aforementioned specified condition is, for example, when the power generation unit 6 is off (i.e., the power generation unit 6 is stopped) and cell balancing is completed, as shown as "Condition #2" in FIG. 5.

When the state of the power generation unit 6 and the state of the equalization circuit 2 satisfy "condition #2", the determination unit 11b causes the power supply control unit 11c to turn on the switch Q2 and supply the power stored in the capacitors C1 to C4 to the heater 4.

The above-mentioned predetermined condition is, for example, when there is no power source for heater 4 (i.e., switch Q1 is off) and cell balancing has been completed, as shown as "Condition #3" in FIG. 5.

When the state of switch Q1 and the state of equalization circuit 2 satisfy "condition #3," determination unit 11b causes power supply control unit 11c to turn on switch Q2 and supply the power stored in capacitors C1 to C4 to heater 4.

Returning to the explanation of FIG. 4, the power supply control unit 11c controls the on/off of the switch Q2 based on the judgment result of the judgment unit 11b. When the judgment unit 11b judges that any of the above-mentioned conditions #1 to #3 is satisfied, the power supply control unit 11c turns on the switch Q2 to supply the power stored in the capacitors C1 to C4 to the heater 4.

Furthermore, if the judgment unit 11b judges that none of the above-mentioned conditions #1 to #3 are satisfied, the power supply control unit 11c turns off the switch Q2.

Next, the processing procedure executed by the heat retention control device 10 will be described with reference to FIG. 6. FIG. 6 is a flowchart showing the processing procedure of the heat retention control device 10 according to the embodiment.

As shown in FIG. 6, the heat retention control device 10 has the acquisition unit 11a acquire the states of the power generation unit 6, the IG switch 7, and the equalization circuit 2 (step S101).

Then, the judgment unit 11b judges whether any of the above-mentioned conditions #1 to #3 (see Figure 5) is satisfied (step S102).

If any of conditions #1 to #3 is met (step S102, Yes), the power supply control unit 11c turns on switch Q2 (step S103) and supplies the power stored in capacitors C1 to C4 to heater 4.

On the other hand, if none of conditions #1 to #3 are met (step S102, No), the power supply control unit 11c turns off the switch Q2 (step S104). Note that step S104 also includes the case where the switch Q2 is maintained in the off state if it is originally off.

Then, the judgment unit 11b judges whether the IG switch 7 is off or not (step S105). If it is not off (step S105, No), the process from step S101 is repeated. If it is off (step S105, Yes), the process ends.

As described above, the heat retention control device 10 according to the embodiment includes an acquisition unit 11a and a power supply control unit 11c. The acquisition unit 11a acquires the state of the heater 4 (corresponding to an example of a "heating device") that heats the LiB3 (corresponding to an example of a "battery") that has multiple cells B1 to B4 and is provided so that cell balancing can be performed by the equalization circuit 2, and the state of the equalization circuit 2. When it is determined based on the states acquired by the acquisition unit 11a that the power supply to the heater 4 has stopped and that power has been stored in the capacitors C1 to C4 of the equalization circuit 2, the power supply control unit 11c supplies the power stored in the capacitors C1 to C4 to the heater 4.

Therefore, the heat retention control device 10 according to the embodiment can keep LiB3 warm while reusing electricity.

The LiB3 is mounted on the vehicle, and the power supply control unit 11c immediately supplies the power stored in the capacitors C1 to C4 to the heater 4 when the vehicle's IG switch 7 is switched from on to off.

Therefore, according to the heat retention control device 10 of the embodiment, when the IG is turned off, the power stored in the capacitors C1 to C4 can be immediately reused to keep the LiB3 warm.

In addition, when the power generation unit 6 that supplies power to the heater 4 is off and cell balancing has been completed, the power supply control unit 11c supplies the power stored in the capacitors C1 to C4 to the heater 4.

Therefore, according to the heat retention control device 10 of the embodiment, the LiB3 can be heated with the power stored in the capacitors C1 to C4 not only when the IG is off, but also when the power generation unit 6 is stopped. Note that if the interval between the stoppage and start-up of the power generation unit 6 is long, the effect of heating with the heater 4 is small, but since there are also situations where the interval is short, supplying power to the heater 4 itself is effective.

In addition, when there is no power source supplying power to the heater 4 and cell balancing has been completed, the power supply control unit 11c supplies the power stored in the capacitors C1 to C4 to the heater 4.

Therefore, according to the heat retention control device 10 of the embodiment, LiB3 can be heated using the power stored in capacitors C1 to C4 not only when the IG is off or the power generation unit 6 is stopped, but also when there is no power source for heater 4.

In addition, a heat storage material 5 is provided near the LiB3. This makes it possible to further improve the heat retention effect of the LiB3.

In addition, since LiB3 is provided so that cell balancing can be performed by the equalization circuit 2, cells B1 to B4 themselves generate heat as charging and discharging takes place inside the equalization circuit 2, and by heating them together with the heater 4, it is possible to quickly raise the temperature.

In the above embodiment, LiB3 is used as an example of a battery, but the battery is not limited to this as long as it includes multiple cells that are the subject of cell balancing by the equalization circuit 2. For example, an electric double layer capacitor configured as a battery may also be used.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

1 Heat retention control system 2 Equalization circuit 3 LiB
4 heater 5 heat storage material 6 power generation unit 7 IG switch 10 heat retention control device 11 control unit 11a acquisition unit 11b determination unit 11c power supply control unit B1 to B4 cells C1 to C4 capacitors D1 to D4 diodes L1 to L4 inductors Q1, Q2 switch

Claims (6)

an acquisition unit that acquires a state of a heating device that heats a battery having a plurality of cells and that is provided so that cell balancing can be performed using an equalization circuit, and a state of the equalization circuit;
and a power supply control unit that supplies the power stored in the capacitor to the heating device when it is determined based on each state acquired by the acquisition unit that the power supply to the heating device has stopped and that power has been stored in the capacitor of the equalization circuit. The battery is mounted on a vehicle,
The power supply control unit is
2. The heat retention control device according to claim 1, wherein when an ignition switch of the vehicle is switched from on to off, the power stored in the capacitor is immediately supplied to the heating device. The power supply control unit is
The heat retention control device according to claim 1 or 2, characterized in that when a power generation unit that supplies power to the heating device is off and the cell balancing is completed, the power stored in the capacitor is supplied to the heating device. The power supply control unit is
The heat retention control device according to claim 1, 2 or 3, characterized in that when there is no power source supplying power to the heating device and the cell balancing has been completed, the power stored in the capacitor is supplied to the heating device. 5. The heat retention control device according to claim 1, further comprising a heat storage material provided in the vicinity of the battery. an acquisition step of acquiring a state of a heating device that heats a battery having a plurality of cells and that is provided so that cell balancing can be performed by an equalization circuit, and a state of the equalization circuit;
and a power supply control process for supplying the power stored in the capacitor to the heating device when it is determined based on each state acquired in the acquisition process that the power supply to the heating device has stopped and that power has been stored in the capacitor of the equalization circuit.

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