Vehicle battery system

Abstract

This invention provides an in-vehicle battery system that can mitigate vehicle speed fluctuations that occur when switching the output power of the battery. [Solution] An on-board battery system comprising: a driving motor; an air conditioning system for adjusting the temperature inside the vehicle; a detection device for detecting the temperature; a battery for supplying power to the driving motor and the air conditioning system; and a control device for controlling the air conditioning system and the output power of the battery, wherein the control device measures the change in the temperature detected by the detection device during a first period, and if the air conditioning system is ON and the change in temperature during the first period is within a threshold, the air conditioning system is turned OFF during a second period, the first period being a predetermined period immediately before switching the output power to the driving motor from a first power to a second power lower than the first power, and the second period being a predetermined time from the start to the end of the switch to the second power.

Description

Technical Field

[0001] The present invention relates to an in-vehicle battery system.

Background Art

[0002] Patent Document 1 discloses an in-vehicle battery system that restricts the output power of a battery to suppress the temperature rise of the battery and prevent the battery from exceeding its upper operating temperature limit. This in-vehicle battery system includes a battery control device that restricts the output power of the battery when the battery temperature is at or above a predetermined power restriction lower temperature. When the battery temperature approaches the upper operating temperature limit, the battery control device restricts the input and output power of the battery to suppress the temperature rise of the battery. The power restriction lower temperature is the lower limit value of the temperature range in which output restriction is performed before the battery temperature reaches the upper operating temperature limit. In a situation where the battery temperature is likely to rise, the battery control device applies a high-load output restriction value lower than the normal output restriction value to restrict the output power of the battery. A situation where the battery temperature is likely to rise is when the driving load is large, the outside air temperature is high, and the cooling load is large.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, in electric vehicles, the battery's output power is determined according to the driving load, and power is supplied from the battery to the drive motor. The battery's output power varies depending on the battery's temperature and charge level. The greater the driving load, the higher the output power required to the drive motor. However, if high output power is maintained for a long period of time, the battery's charge level may decrease rapidly, or the battery's temperature may rise suddenly. Therefore, normally, control is performed to limit the output power by switching the battery's output power. However, when the output power is switched, the output power to the drive motor fluctuates, causing the drive motor's torque to fluctuate. This can lead to a hunting phenomenon where the vehicle speed becomes unstable, potentially causing discomfort to the passengers.

[0005] One of the objectives of the present invention is to provide an in-vehicle battery system that can mitigate vehicle speed hunting that occurs when switching the output power of the battery. [Means for solving the problem]

[0006] An in-vehicle battery system according to one aspect of the present invention comprises a driving motor, an air conditioning system for adjusting the temperature inside the vehicle, a detection device for detecting at least the temperature, a battery for supplying power to the driving motor and the air conditioning system, and a control device for controlling the air conditioning system and the output power of the battery. The control device measures the change in the temperature detected by the detection device during a first period, and if the air conditioning system is ON and the change in temperature during the first period is within a threshold, it turns the air conditioning system OFF during a second period. The first period is a predetermined period immediately before switching the output power to the driving motor from a first power to a second power lower than the first power. The second period is a predetermined time from the start to the end of the switch to the second power. [Effects of the Invention]

[0007] The above-described onboard battery system switches off the air conditioning system during the second period, when the output power to the drive motor is switched from the first power to the second power. This increases the output power to the drive motor during the second period by sending the power that would otherwise be consumed by the air conditioning system to the drive motor, thus reducing the decrease in vehicle speed. Therefore, the vehicle speed hunting that occurs when the battery output power is switched can be mitigated, and the discomfort caused by vehicle speed hunting can be reduced. In addition, if the change in the temperature inside the vehicle during the first period immediately before switching the output power to the drive motor to the second power is within a threshold, the temperature inside the vehicle is assumed to be stable. Therefore, even if the air conditioning system is turned off during the second period, the change in the temperature inside the vehicle is small, making it less likely to cause discomfort to the passengers. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an in-vehicle battery system according to an embodiment. [Figure 2] Figure 2 is a schematic diagram showing the configuration of an air conditioning system included in an in-vehicle battery system according to an embodiment. [Figure 3] Figure 3 is a timing chart showing the time changes of accelerator pedal operation, output power, and vehicle speed. [Figure 4] Figure 4 is a graph showing the time change of the output power during the second period when control is performed in the in-vehicle battery system according to the embodiment. [Figure 5] Figure 5 is a graph showing the time change of the vehicle speed during the second period when control is performed in the in-vehicle battery system according to the embodiment. [Figure 6] Figure 6 is a flowchart showing an example of a control procedure by the control device of the in-vehicle battery system according to the embodiment. [Modes for carrying out the invention]

[0009] A specific example of an in-vehicle battery system according to an embodiment of the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals. The sizes of the components shown in each figure are represented for the purpose of clarifying the explanation and do not necessarily represent actual dimensions and proportions.

[0010] <Automotive Battery System> Referring to Figure 1, the configuration of the on-board battery system 1 according to this embodiment will be described. The on-board battery system 1 is mounted on an electric vehicle (not shown). An electric vehicle is an automobile that drives a traction motor 3 using electricity supplied from a battery 2. An electric vehicle is, for example, a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), or a fuel cell electric vehicle (FCEV).

[0011] As shown in Figure 1, the on-board battery system 1 comprises a battery 2, a traction motor 3, an air conditioning unit 4, a detection device 7, and a control device 8. The control device 8 controls the air conditioning unit 4 and the output power of the battery 2. One of the features of the on-board battery system 1 is that when switching the output power to the traction motor 3, if the air conditioning unit 4 is ON and certain conditions are met, it executes a control to turn the air conditioning unit 4 OFF. The configuration of the on-board battery system 1 will be described in detail below.

[0012] ≪Battery≫ Battery 2 is used as a power source to drive the traction motor 3. In addition to supplying power to the traction motor 3, Battery 2 also supplies power to the air conditioning unit 4.

[0013] ≪Motor for driving≫ The drive motor 3 is powered by electricity supplied from the battery 2. The higher the output power from the battery 2 to the drive motor 3, the higher the output the drive motor 3 can generate, and the greater the torque the drive motor 3 can produce.

[0014] ≪Air conditioner≫ As shown in Figure 2, the air conditioning system 4 adjusts the temperature of the air taken into the air conditioning duct 40 and sends the temperature-adjusted air from the air conditioning duct 40 into the vehicle interior. The air conditioning duct 40 is a duct through which air flows from outside the vehicle interior into the vehicle interior. The air conditioning duct 40 has an inlet 41, an air conditioning unit 5, and an outlet 42. The inlet 41 is the part that takes air into the air conditioning duct 40. The outlet 42 is the part that blows air out of the air conditioning duct 40 into the vehicle interior. In the air conditioning duct 40, the direction in which air flows in is upstream, and the direction in which air flows out is downstream. The inlet 41 is located at the uppermost part of the air conditioning duct 40. The outlet 42 is located at the lowermost part of the air conditioning duct 40. The air conditioning unit 5 is located in the middle part of the air conditioning duct 40. The air conditioning system 4 in this example is a heat pump type air conditioning system equipped with an electric compressor. A known configuration can be applied to the air conditioning unit 4.

[0015] The air conditioning duct 40 is equipped with a blower 45. The blower 45 is located upstream of the air conditioning unit 5. As the blower 45 rotates, air is drawn into the air conditioning duct 40 from the inlet 41, and the drawn-in air is sent through the air conditioning unit 5 to the outlet 42. By adjusting the output of the blower 45, the airflow rate of the air blown out from the outlet 42 is adjusted.

[0016] [Air conditioning unit] The air conditioning unit 5 adjusts the temperature of the air taken into the air conditioning duct 40. The air conditioning unit 5 has an evaporator 51, a heater core 52, and an air mix door 53. The evaporator 51 is a component that cools the air taken into the air conditioning duct 40. A refrigerant circulates through the evaporator 51. The cooled refrigerant circulates through the evaporator 51, cooling the air that passes through the evaporator 51. In this example, during cooling, the refrigerant circulating through the evaporator 51 is cooled by a heat pump (not shown). The heat pump cools the refrigerant by releasing the heat from the refrigerant compressed by an electric compressor into the outside air. The refrigerant is further cooled by expanding. The electric compressor is driven by power supplied from the battery 2.

[0017] The heater core 52 is a member that heats the air passing through the evaporator 51. The heater core 52 is disposed downstream of the evaporator 51. A heat medium circulates through the heater core 52. When the heated heat medium circulates through the heater core 52, the air passing through the heater core 52 is heated. In this example, during heating, the heat medium circulating through the heater core 52 is heated by a heat pump not shown in the figure. The heat pump extracts heat from the outside air and heats the heat medium. Further, the heat medium is heated by being compressed by an electric compressor.

[0018] The air conditioner 4 of this example further includes an electric heater not shown in the figure. The electric heater heats the heat medium circulating through the heater core 52. The electric heater is, for example, a high-voltage heater (HVH: High Voltage Heater). The electric heater is used when the heating capacity is insufficient with only the heat pump. The electric heater is driven by the electric power supplied from the battery 2.

[0019] The air mix door 53 is a member that adjusts the ratio of the air passing through the heater core 52 and the air bypassing the heater core 52. The air mix door 53 is disposed between the evaporator 51 and the heater core 52. That is, the air mix door 53 is disposed downstream of the evaporator 51 and upstream of the heater core 52. By adjusting the opening degree of the air mix door 53, the temperature of the air blown out from the air outlet 42 is adjusted.

[0020] <<Detection device>> The detection device 7 shown in FIG. 1 is a sensor that detects the air conditioning situation in the vehicle interior. The detection device 7 includes a temperature sensor 70 that detects the temperature in the vehicle interior. The temperature sensor 70 may be installed at an appropriate position in the vehicle interior. The temperature sensor 70 may be installed, for example, inside an instrument panel not shown in the figure, or may be installed at the air outlet 42 shown in FIG. 2. In this example, the temperature sensor 70 is installed at the air outlet 42 and detects the temperature of the air blown into the vehicle interior from the air outlet 42. The detection device 7 may have, in addition to the temperature sensor 70, a humidity sensor not shown in the figure that detects the humidity in the vehicle interior.

[0021] ≪Control device≫ The control device 8 is comprised of, for example, an electronic control unit (ECU). Each process performed by the control device 8 is realized by a processing circuit (Circuitry) that includes one or more processors.

[0022] The above processing circuit may consist of one or more processors, one or more memories, various analog circuits, various digital circuits, etc., combined in an integrated circuit, and may also include an input / output interface (I / F). The one or more memories store programs (instructions) that cause the one or more processors to execute each of the above processes. The one or more memories are typically ROM (Read-Only Memory) and RAM (Random Access Memory).

[0023] One or more of the above processors may execute each of the above processes according to the above program read from one or more of the above memory, or they may execute each of the above processes according to logic circuits that have been pre-designed to execute each of the above processes. The above processors may be various processors suitable for computer control, such as CPUs (Central Processing Units), GPUs (Graphics Processing Units), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and ASICs (Application Specific Integrated Circuits). Furthermore, multiple physically separated processors may cooperate with each other to execute each of the above processes.

[0024] The control device 8 performs output control to switch the output power of the battery 2, measurement control to measure the change in temperature inside the vehicle immediately before switching the output power, and air conditioning stop control to turn off the air conditioning system 4 when the air conditioning system 4 is ON and the measured temperature change is within a predetermined range. The details of each control will be explained below with reference to Figures 3 to 5. The top graph in Figure 3 is a graph showing the change in the amount of operation of the accelerator pedal over time. The horizontal axis represents time [seconds], and the vertical axis represents the amount of operation of the accelerator pedal [%]. The middle graph in Figure 3 is a graph showing the change in the output power of the battery 2 and the output power to the driving motor 3 over time. The horizontal axis represents time [seconds], and the vertical axis represents output power [kW]. The dashed line graph in Figure 3 shows the change in the output power Wout of the battery 2 over time. The solid line graph in Figure 3 shows the change in the output power Pm to the driving motor 3 over time. The bottom graph in Figure 3 shows the change in the vehicle speed Vs over time. The horizontal axis represents time [seconds], and the vertical axis represents vehicle speed [km / h].

[0025] Output control switches the output power Wout of battery 2 according to the driving load of the electric vehicle. Driving load refers to the load acting on the electric vehicle while it is in motion. Driving load is high when starting, accelerating, and climbing hills. When the driving load is high, it is required to drive the drive motor 3 at high output, so the output power Pm to the drive motor 3 needs to be increased. The driving load can be determined, for example, according to the amount of accelerator pedal operation. When the amount of accelerator pedal operation is large, it is assumed that the driving load is high. For example, if the amount of accelerator pedal operation is 70% or more, it is considered that the driving load is high. The amount of accelerator pedal operation can be detected by an accelerator sensor (not shown).

[0026] Output control includes control that switches the output power Pm to the drive motor 3 from a first power P1 to a second power P2. "Switching from the first power P1 to the second power P2" means switching in the order of first power P1 → second power P2 → first power P1. Specifically, if the state of first power P1 continues for a certain period of time, the system switches from first power to second power for a predetermined time and then switches back to first power. First power P1 is the power supplied from the battery 2 to the drive motor 3 when the driving load is high. Second power P2 is a lower power than first power P1 and is a power that can reduce the temperature rise of the battery 2. If the state of first power P1 continues for a long time, the power consumed by the drive motor 3 increases, and the charge of the battery 2 decreases rapidly. In addition, the temperature of the battery 2 rises rapidly due to the heat generated during discharge. By switching from the high output first power P1 to the low output second power P2, the power consumption of the drive motor 3 is reduced, and the decrease in the charge of the battery 2 can be mitigated. Furthermore, it is possible to reduce the temperature rise of battery 2 due to heat generation during discharge, and to recover the temperature of battery 2 more quickly.

[0027] When the output power Wout of battery 2 is switched, the output power Pm to the drive motor 3 is switched. In this example, the output power Wout is switched using a predetermined output map. The output map is used for output control of the battery of an electric vehicle and represents the relationship between the temperature, charge state (SOC: State of Charge) of battery 2 and the output power Wout. The output power Wout is the upper limit of the discharge power under normal use conditions of battery 2. When the selected output map switches from high output to low output, the output power Pm switches from the first power P1 to the second power P2. If the output map remains in a high output state for a long period of time, the output map is automatically switched to a low output after a certain period of time has elapsed.

[0028] While the first power setting P1 is enabled, the drive motor 3 operates at high output, resulting in high power performance. However, if the duration of the first power setting P1, i.e., the duration Dh of the first power setting, is too long, the temperature of the battery 2 will rise significantly. The duration Dh of the first power setting P1 is, for example, between 10 seconds and 60 seconds.

[0029] While the vehicle is switched to the second power source P2, the output power Pm to the drive motor 3 decreases, causing a decrease in the torque of the drive motor 3. As a result, a hunting phenomenon occurs in which the vehicle speed Vs temporarily decreases. The duration of the switch to the second power source P2, i.e., the second period D2 from the start to the end of the switch to the second power source P2, is, for example, between 2 seconds and 10 seconds.

[0030] The measurement and control measures the temperature change detected by the temperature sensor 70 during the first period D1. The first period D1 is a predetermined period immediately before switching to the second power P2. The first period D1 is, for example, 2 seconds or more and 10 seconds or less. For example, if the first period D1 is 3 seconds, the temperature change from 3 seconds before switching to the second power P2 until the start of the switch is measured.

[0031] The air conditioning stop control determines whether the temperature change measured by the above measurement control is within a predetermined threshold. If the air conditioning unit 4 is ON and the temperature change in the first period D1 is within the threshold, the air conditioning stop control turns the air conditioning unit 4 OFF during the second period D2. Turning the air conditioning unit 4 OFF reduces the power consumption of the air conditioning unit 4. Specifically, the power consumption of the heat pump compressor and electric heater can be reduced. Figure 4 shows the output power Pm to the traction motor 3 during the second period D2. The solid line in Figure 4 shows the output power Pm when the air conditioning unit 4 remains ON. The dashed line in Figure 4 shows the output power Pm when the air conditioning unit 4 is OFF. Figure 5 shows the vehicle speed Vs during the second period D2. The solid line in Figure 5 shows the vehicle speed Vs when the air conditioning unit 4 remains ON. The dashed line in Figure 5 shows the vehicle speed Vs when the air conditioning unit 4 is OFF. As shown in Figure 4, by turning off the air conditioning unit 4, the power consumed by the air conditioning unit 4 can be sent to the traction motor 3 during the second period D2. As a result, the output power Pm increases during the second period D2. Therefore, as shown in Figure 5, the decrease in vehicle speed Vs is reduced, and the hunting of vehicle speed Vs can be mitigated.

[0032] The temperature change threshold is, for example, ±3°C or less. If the temperature change during the first period D1 is within the threshold, the temperature inside the vehicle is assumed to be stable. During the second period D2, even if the air conditioning system 4 is turned OFF, the temperature change inside the vehicle is small, so it is unlikely to cause discomfort to the passengers.

[0033] [Control Procedure] Referring to Figure 6, a specific example of the control procedure by the control device 8 will be explained. In this example, the case where control is started when the air conditioning unit 4 is ON and the driving load is high will be explained.

[0034] <Step S1 - Step S2> Step S1 sets the output power Pm to the drive motor 3 to the first power = P1 according to the driving load and starts the timer count. In this example, the duration Dh of the first power P1 is 30 seconds. That is, after 30 seconds have elapsed since setting to the first power P1, it switches to the second power P2. Step S2 waits until the timer count reaches the first period D1. In this example, the first period D1 is 3 seconds. That is, it waits until 27 seconds have elapsed since setting to the first power P1.

[0035] <Step S3 - Step S4> Step S3 measures the change in temperature Tc inside the vehicle during the first period D1 and determines whether the temperature change Tc is within the range of the threshold Tt. In this example, the threshold Tt is ±3°C. That is, the temperature change Tc in the 3 seconds immediately before switching to the second power P2 is measured and it is determined whether the temperature change Tc is ±3°C or less. The temperature inside the vehicle is detected by the temperature sensor 70. In this example, the temperature of the air blown out from the air outlet 42 is detected. If the temperature change Tc is within the range of the threshold Tt, the process proceeds to step S4 and the air conditioning unit 4 is turned OFF. In this example, during cooling, the electric compressor is turned OFF. During heating, the electric compressor and electric heater are turned OFF. If the temperature change Tc is outside the range of the threshold Tt, the process proceeds to step S5. That is, the air conditioning unit 4 is not turned OFF.

[0036] <Step S5 - Step S6> Step S5 switches the output power Pm to the drive motor 3 from the first power P1 to the second power P2. In this example, the second period D2 from the start to the end of the switch to the second power P2 is 4 seconds. Step S6 switches back from the second power P2 to the first power P1 after the switch to the second power P2 is complete.

[0037] <Step S7> Step S7 is to turn on the air conditioning unit 4 if it was turned OFF in step S4. In other words, the air conditioning unit 4 is OFF during the second period D2 when the power supply is switched to the second power supply P2. [Explanation of Symbols]

[0038] 1. On-board battery system 2 batteries 3. Motor for driving 4 Air conditioner 5. Air conditioning unit 7. Detection device 8 Control device 40 Air conditioning ducts 41 inlet, 42 outlet 45 Blower 51 Evaporator, 52 Heater core, 53 Air mix door 70 Temperature Sensor P1: Power Plant 1, P2: Power Plant 2 Wout: Battery output power, Pm: Output power to the drive motor Dh duration D1 Period 1, D2 Period 2 Vs vehicle speed Tc: Temperature change, Tt: Threshold

Claims

[Claim 1] The driving motor and An air conditioning system that adjusts the temperature inside the vehicle, A detection device for detecting the temperature, A battery that supplies power to the aforementioned drive motor and the aforementioned air conditioning system, The system includes a control device that controls the air conditioning system and the output power of the battery, The control device is The change in the temperature detected by the detection device during the first period is measured. If the air conditioning unit is ON and the temperature change during the first period is within the threshold, the air conditioning unit will be turned OFF during the second period. The first period is a predetermined period immediately before switching the output power to the drive motor from a first power to a second power lower than the first power. The second period is a predetermined time from the start to the end of the switching of the second power supply. Vehicle battery system.

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