Battery heating device

Abstract

To provide a battery heating device capable of suppressing deterioration of a motor coil.SOLUTION: A battery heating device includes a heating unit that heats a battery by passing a current from the battery to a coil of one phase selected from the coils of multiple phases of an electric motor, an estimation unit that estimates the temperature of each of the coils of the multiple phases while the temperature of the battery is being raised, and a recording unit that records a history of temperature stress according to the maximum value of the temperature of each of the coils of the multiple phases, and the heating unit selects, as the coil of the one phase to be heated, the coil of the phase that has the least amount of accumulated temperature stress from among the coils of the multiple phases on the basis of the history of the temperature stress.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a battery temperature increasing device.

Background Art

[0002] Regarding the technology for increasing the temperature of a battery, for example, Patent Document 1 describes that in a vehicle, the temperature of a secondary battery is increased by energizing a coil of a specific phase of a three-phase AC motor from the secondary battery.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the temperature of the battery is increased, only the coil of a specific phase is energized so that the motor driving the vehicle does not rotate. However, when only the coil of a specific phase is energized, there is a risk that the deterioration of the coil will progress significantly due to the temperature rise during energization.

[0005] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a battery temperature increasing device capable of suppressing the deterioration of the coil of an electric motor.

Means for Solving the Problems

[0006] The battery temperature increasing device of the present invention includes a temperature increasing unit that increases the temperature of the battery by energizing one phase of the coils selected from a plurality of phases of the motor coils from the battery, an estimating unit that estimates the temperature of each of the plurality of phases of the coils during the temperature increase of the battery, and a recording unit that records a history of temperature stress corresponding to the maximum value of the temperature of each of the plurality of phases of the coils. The temperature increasing unit selects, as the one phase of the coil to be energized, the coil of the phase with the least accumulated amount of the temperature stress among the plurality of phases of the coils based on the history of the temperature stress.

Effect of the Invention

[0007] According to the present invention, deterioration of the motor coils can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] (Configuration of Vehicle Drive System) FIG. 1 is a configuration diagram showing an example of a vehicle drive system 9. The vehicle drive system 9 is mounted on, for example, a hybrid vehicle or an electric vehicle. The vehicle drive system 9 includes, as an example, a motor 2, a storage battery 3 such as a lithium-ion battery, a gate drive circuit 4, an ECU (Electronic Control Unit) 1, an inverter 5, current sensors 61u to 61w, a temperature sensor 62, an oil temperature sensor 63, an IGBT (Insulated Gate Bipolar Transistor) 55, a diode 56, and a smoothing capacitor 57.

[0010] The storage battery 3 is an example of a battery. When the IGBT 55 is in the on state, the storage battery 3 supplies power to the electric motor 2 via the inverter 5. The inverter 5 generates a three-phase alternating current from the direct current output from the storage battery 3 and outputs it to the electric motor 2. The current sensors 61u to 61w are connected between the inverter 5 and the electric motor 2, and detect the current values Iu, Iv, and Iw of the u-phase, v-phase, and w-phase respectively.

[0011] The stator of the electric motor 2 is provided with three-phase coils (windings) 20u to 20w that are delta-connected to each other. When a three-phase alternating current flows from the inverter 5 to the coils 20u to 20w, the electric motor 2 rotates as a motor and can drive a drive shaft (not shown). Further, the temperature sensor 62 is, for example, a thermistor and detects the temperature of the stator of the electric motor 2. The oil temperature sensor 63 detects the temperature of the cooling oil that cools the electric motor 2.

[0012] The inverter 5 has IGBTs 51a to 51c and freewheeling diodes 53a to 53c on the upper arm side, and IGBTs 52a to 52c and freewheeling diodes 54a to 54c on the lower arm side. Note that other switching elements may be used instead of the IGBTs 51a to 51c and 52a to 52c.

[0013] The collector terminals of the IGBTs 51a to 51c on the upper arm are connected to the positive terminal of the storage battery 3, and the emitter terminals of the IGBTs 51a to 51c on the upper arm are respectively connected to the collector terminals of the IGBTs 52a to 52c on the lower arm. The emitter terminals of the IGBTs 52a to 52c on the lower arm are connected to the negative terminal of the storage battery 3. The connection points between the IGBTs 51a to 51c on the upper arm and the IGBTs 52a to 52c on the lower arm are connected to the coils 20u to 20w via the current sensors 61u to 61w. The gate terminals of each of the IGBTs 51a to 51c and 52a to 52c are connected to the gate drive circuit 4.

[0014] Each of the IGBTs 51a to 51c and 52a to 52c has freewheeling diodes 53a to 53c and 54a to 54c connected in parallel. The cathode terminals of the freewheeling diodes 53a to 53c and 54a to 54c are respectively connected to the collector terminals of the IGBTs 51a to 51c and 52a to 52c, and the anode terminals of the freewheeling diodes 53a to 53c and 54a to 54c are respectively connected to the emitter terminals of the IGBTs 51a to 51c and 52a to 52c. A regenerative current flows from the coils 20u to 20w into the freewheeling diodes 53a to 53c and 54a to 54c. Further, the freewheeling diodes 53a to 53c and 54a to 54c discharge the surge voltage generated when the IGBTs 51a to 51c and 52a to 52c are turned off.

[0015] The IGBT 55 is connected between the positive terminal of the storage battery 3 and the collector terminals of the upper-arm IGBTs 51a to 51c. The gate terminal of the IGBT 55 is connected to the gate drive circuit 4. A diode 56 is connected in parallel to the IGBT 55. The anode terminal of the diode 56 is connected to the emitter terminal of the IGBT 55, and the cathode terminal of the diode 56 is connected to the collector terminal of the IGBT 55. The diode 56 controls the direction of the direct current from the storage battery 3.

[0016] The smoothing capacitor 57 is connected between the positive and negative terminals of the storage battery 3. The smoothing capacitor 57 smoothes the voltage between the upper-arm IGBTs 51a to 51c and the lower-arm IGBTs 52a to 52c by capacitance.

[0017] The gate drive circuit 4 drives the IGBTs 51a to 51c, 52a to 52c, and 55. The gate drive circuit 4 generates a switching signal according to an instruction from the ECU 1 and outputs it to the gate terminals of the respective IGBTs 51a to 51c, 52a to 52c, and 55. The IGBTs 51a to 51c, 52a to 52c, and 55 turn on or off according to the switching signal. Note that the on state refers to a state in which current flows from the collector terminal to the emitter terminal of the IGBTs 51a to 51c, 52a to 52c, and 55.

[0018] ECU1 controls the vehicle drive system 9. ECU1 is an example of a battery temperature raising device. When the vehicle is running, ECU1 instructs the gate drive circuit 4 to generate a switching signal that becomes a PWM (Pulse Width Modulation) signal so that a three-phase alternating current is output to the electric motor 2. As a result, IGBTs 51a - 51c, 52a - 52c repeatedly turn on and off at individual timings to generate a three-phase alternating current from a direct current. Note that IGBT 55 is maintained in the on state.

[0019] Also, when the vehicle stops, ECU1 performs temperature raising control of the storage battery 3 so that the charging time of the storage battery 3 does not increase due to the temperature drop of the storage battery 3. In this example, ECU1 raises the temperature of the storage battery 3 by performing charge and discharge control on the storage battery 3 using coils 20u - 20w, but is not limited thereto, and the storage battery 3 may be heated using the heat generation of coils 20u - 20w.

[0020] ECU1 instructs the gate drive circuit 4 so that current flows from the storage battery 3 to only one of the three-phase coils 20u - 20w. When ECU1 instructs the gate drive circuit 4 to pass current through coil 20u, it instructs to turn on only IGBTs 55, 51a, 52b. When passing current through coil 20v, it instructs to turn on only IGBTs 55, 51b, 52c. Also, when ECU1 instructs to pass current through coil 20w, it instructs to turn on only IGBTs 55, 51c, 52a. That is, the combination of the upper-arm IGBTs 51a - 51c and the lower-arm IGBTs 52a - 52c corresponding to coils 20u - 20w is turned on.

[0021] After energizing one of the coils 20u to 20w for a predetermined time, ECU1 turns off IGBT55. As a result, a back electromotive force is generated in the energized coil 20u to 20w, and the capacitor 57 is charged with the charge from the coil 20u to 20w. Thereafter, ECU1 turns off IGBT51a to 51c and 52a to 52c, and turns off only IGBT55. As a result, the charged power of the capacitor 57 is supplied to the battery 3, and the battery 3 is charged. Due to the above operations, the battery 3 is discharged and charged, so the battery 3 generates heat and its temperature rises due to its internal resistance component.

[0022] However, if ECU1 energizes only a specific coil among the coils 20u to 20w, the coil may deteriorate significantly due to the temperature rise during energization.

[0023] Therefore, ECU1 records the history of temperature stress due to the temperature rise of the coils 20u to 20w for each phase, and selects and energizes the coil 20u to 20w in the phase with the least temperature stress based on the history. At this time, ECU1 estimates the temperature of the energized coils 20u to 20w from the current values Iu, Iv, Iw, the temperature Ts, and the oil temperature To, etc. The configuration of ECU1 will be described below.

[0024] (Configuration of ECU) Figure 2 is a configuration diagram showing an example of ECU1. ECU1 is an example of a computer and includes a CPU (Central Processing Unit) 10, a ROM (Read Only Memory) 11, a RAM (Random Access Memory) 12, a non-volatile memory 13 such as a flash memory, and a communication port 14. The CPU 10 is electrically connected to the ROM 11, the RAM 12, the non-volatile memory 13, and the communication port 14 via a bus 19 so that signals can be input and output to each other.

[0025] The ROM 11 stores a program for driving the CPU 10. The RAM 12 functions as a working memory of the CPU 10. The communication port 14 relays communication between the CPU 10 and the current sensors 61u to 61w, the temperature sensor 62, and the oil temperature sensor 63.

[0026] When the CPU 10 reads a program from the ROM 11, it forms a temperature rising unit 100, an estimation unit 101, and a recording unit 102 as software functions. Note that the temperature rising unit 100, the estimation unit 101, and the recording unit 102 may be formed as hardware such as an ASIC (Application Specific Integrated Circuit). Also, the non-volatile memory 13 stores temperature change amount map data 130, saturation temperature map data 131, and temperature stress history data 132.

[0027] The temperature rising unit 100 heats up the storage battery 3 by energizing it from the storage battery 3 to one phase of the coils 20u to 20w of the three phases of the electric motor 2. For example, the temperature rising unit 100 instructs the gate drive circuit 4 to turn on or off each of the IGBTs 51a to 51c, 52a to 52c so that only the selected coils 20u to 20w are energized. As a result, the storage battery 3 discharges and heats up due to its internal resistance.

[0028] After energization for a certain period of time, the temperature rising unit 100 instructs the gate drive circuit 4 to turn off the IGBT 55 so that the smoothing capacitor 57 is charged. After charging, the temperature rising unit 100 instructs the gate drive circuit 4 to turn on the IGBT 55 and turn off the IGBTs 51a to 51c, 52a to 52c. As a result, the storage battery 3 is charged from the smoothing capacitor 57 and heats up due to its internal resistance.

[0029] The estimation unit 101 estimates the temperatures of the coils 20u to 20w during the temperature rise of the storage battery 3 based on the temperature change amount map data 130 and the saturation temperature map data 131. In the temperature change amount map data 130, for each temperature estimated value T1 to Tn (n: an integer of 2 or more), the temperature change amount (°C / second) per phase corresponding to the maximum current value (A) and the oil temperature (°C) among the respective current values of the coils 20u to 20w is registered. The estimation unit 101 acquires the temperature change amounts of the coils 20u to 20w from the temperature change amount map data 130 based on the detection values of the current sensors 61u to 61w and the oil temperature sensor 63 and the immediately preceding temperature estimated value.

[0030] The estimation unit 101 calculates a new temperature estimated value by adding the product of the temperature change amount in the temperature change amount map data 130 and a predetermined time (for example, the cycle of the estimation process) to the immediately preceding temperature estimated values of the coils 20u to 20w. Note that the detection value of the temperature sensor 62 is used as the initial value of the temperature estimated value.

[0031] The temperature change amounts of the coils 20u to 20w are determined by the heat generation amount due to energization and the cooling amount due to the cooling oil. The heat generation amount is calculated based on the product of the squared values of the current values Iu to Iw of the coils 20u to 20w and the resistance value (that is, the power). Further, the cooling amount is calculated based on the oil temperature. The temperature change amount map data 130 is generated in advance by simulation results or experimental results and stored in the non-volatile memory 13.

[0032] In addition, in the saturation temperature map data 131, the saturation temperatures (°C) of the coils 20u to 20w during energization corresponding to the maximum current value (A) and the oil temperature (°C) among the respective current values of the coils 20u to 20w are registered. When the temperature estimated value is higher than the saturation temperature, the estimation unit 101 sets the saturation temperature as the temperature estimated value.

[0033] The recording unit 102 records the history of temperature stress according to the maximum value of the estimated temperature of the coils 20u to 20w of each phase. The temperature stress history data 132 records the lifetimes Lu to Lw of the coils 20u to 20w of the u-phase, v-phase, and w-phase. During the energization of the coils 20u to 20w, the recording unit 102 can calculate the temperature stress applied to each of the coils 20u to 20w with high precision in order to calculate the temperature stress from the maximum value of the estimated temperature.

[0034] For example, the recording unit 102 calculates the amount of decrease in the lifetimes of the coils 20u to 20w as the temperature stress. The lifetime can be calculated, for example, according to the Arrhenius law. According to the Arrhenius law, when the temperature of the coils 20u to 20w changes by 10°C, the lifetime is halved. Each time the coils 20u to 20w are energized, the recording unit 102 subtracts the decrease amount ΔL, which is the temperature stress, from the lifetime for each phase and records it as a history in the temperature stress history data 132.

[0035] The recording unit 102 sets the lifetime at the time of manufacturing the coils 20u to 20w to 160°C - 500H, for example. 160°C - 500H means that the endurance time in a temperature environment of 160°C is 500 hours.

[0036] ΔL = t × 1 / 2 {(160-Tmax) / 10} ···(1)

[0037] The recording unit 102 calculates the decrease amount ΔL of the lifetime from the above formula (1). In formula (1), t is the energization time of the coils 20u to 20w, and Tmax is the maximum value of the estimated temperature of the coils 20u to 20w. For example, when Tmax = 150°C and t = 1 second, the decrease amount ΔL of the lifetime is 0.5 seconds in a temperature environment of 160°C. Therefore, the lifetime of the coils 20u to 20w becomes 1799999.5 seconds, which is reduced by 0.5 seconds from 500 hours.

[0038] In this way, each time the coils 20u to 20w are energized, the recording unit 102 calculates the amount of life reduction ΔL corresponding to the maximum temperature of each coil 20u to 20w, and records in the temperature stress history data 132 the life reduced by the amount of reduction ΔL. That is, the accumulated amount of temperature stress is recorded in the temperature stress history data 132.

[0039] Based on the temperature stress history data 132, the temperature increasing unit 100 selects, as the coils 20u to 20w of one phase to be energized, the coils 20u to 20w of the phase with the least accumulated amount of temperature stress. Specifically, the temperature increasing unit 100 selects, in the temperature stress history data 132, the coils 20u to 20w of the phase with the longest life. Thereby, among the three-phase coils 20u to 20w, the situation where only one phase of the coils is biasedly energized is suppressed, and each coil 20u to 20w is energized on average, so that the deterioration of the coils 20u to 20w as a whole can be suppressed.

[0040] (Battery temperature increasing process) FIG. 3 is a flowchart showing an example of the battery temperature increasing process. This process is executed, for example, when the temperature of the storage battery 3 becomes lower than the threshold value during the stop of the vehicle.

[0041] First, the temperature increasing unit 100 refers to the temperature stress history data 132 (step St1). Next, based on the temperature stress history data 132, the temperature increasing unit 100 selects one phase of the coil with the longest life from the three-phase coils 20u to 20w (step St2). Next, the temperature increasing unit 100 starts energization only for the selected one-phase coils 20u to 20w by instructing the gate drive circuit 4 to turn on and off the IGBTs 51a to 51c, 52a to 52c, and 55 (step St3). At this time, the temperature increasing unit 100 starts a timer for measuring the energization time.

[0042] Next, the estimation unit 101 acquires the detection values of the current sensors 61u to 61w, the temperature sensor 62, and the oil temperature sensor 63 (step St4). Next, the estimation unit 101 acquires the temperature change amount from the temperature change amount map data 130 based on the temperature of the temperature sensor 62 (initial value of the temperature estimation value), the maximum current value among the current values of the current sensors 61u to 61w, and the oil temperature of the oil temperature sensor 63 (step St5). Next, the estimation unit 101 calculates the temperature estimation value by multiplying the temperature change amount by the temperature estimation period (step St6).

[0043] Next, the estimation unit 101 acquires the saturation temperature for each phase from the saturation temperature map data 131 based on the maximum current value among the current values of the current sensors 61u to 61w and the oil temperature of the oil temperature sensor 63 (step St7). Next, the estimation unit 101 compares the temperature estimation value with the saturation temperature for each phase (step St8). When the temperature estimation value > saturation temperature holds (Yes in step St8), the estimation unit 101 updates the temperature estimation value of the corresponding phase to the saturation temperature (step St9). When the temperature estimation value ≤ saturation temperature holds (No in step St8), the estimation unit 101 does not execute the process of step St9 for the corresponding phase.

[0044] Next, the temperature rising unit 100 determines whether the energization time has exceeded a predetermined time K based on a timer (step St10). The predetermined time K is determined based on, for example, the temperature rise amount of the storage battery 3 with respect to the energization amount of the coils 20u to 20w. When the energization time ≤ K holds (No in step St10), the processes from step St4 and subsequent are executed again. When the energization time > K holds (Yes in step St10), the temperature rising unit 100 instructs the gate drive circuit 4 to stop the energization of the coils 20u to 20w (step St11).

[0045] Next, the recording unit 102 detects the maximum temperature for each of the energized coils 20u to 20w (step St12). Here, the recording unit 102 stores the temperature estimation value for each of the coils 20u to 20w in the RAM 11 every time the estimation unit 101 calculates the temperature estimation value, and detects the maximum value after the energization stops.

[0046] Next, the recording unit 102 calculates the amount of decrease in the lifespan of each coil 20u to 20w by the above method (step St13). Next, the recording unit 102 updates the lifespan of the temperature stress history data 132 based on the amount of decrease (step St14). For this reason, in step St1, the temperature raising unit 100 can appropriately select the coil with the longest lifespan among the coils 20u to 20w. In this way, the battery temperature raising process is executed.

[0047] The above-described embodiments are preferred examples of the present invention. However, the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

Explanation of Reference Numerals

[0048] 1 ECU (Battery Temperature Raising Device), 2 Electric Motor, 3 Storage Battery (Battery), 5 Inverter, 9 Vehicle Drive System, 20u to 20w Coils, 100 Temperature Raising Unit, 101 Estimation Unit, 102 Recording Unit

Claims

【Claim 1】 A temperature raising unit that raises the temperature of the battery by energizing one phase of coils selected from a plurality of phases of coils of an electric motor from a battery; An estimation unit that estimates the temperature of each of the plurality of phases of coils during the temperature rise of the battery; A recording unit that records a history of temperature stress according to the maximum value of the temperature of each of the plurality of phases of coils; and has, The temperature raising unit selects, as the one phase of coils to be energized, the coil of the phase with the least accumulated amount of the temperature stress among the plurality of phases of coils based on the history of the temperature stress. A battery temperature raising device.

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