Electric vehicle temperature management apparatus

Abstract

Provided is an electric vehicle temperature management apparatus that makes it possible to suppress an excessive reduction in the output performance of an electric motor or the charge performance of a battery. This electric vehicle temperature management apparatus comprises a first module that is connected to a first power line via a second power line for equipment drive and that is capable of measuring a voltage input via the second power line, at least one second module that is capable of measuring a current flowing through the first power line, and a controller that performs temperature management. The controller determines the resistance value of the first power line on the basis of at least the voltage measured by the first module and the current measured by the second module and stores the resistance value. During battery discharge, the controller estimates the temperature of the first power line on the basis of the stored resistance value and the current of the first power line, and performs current limitation of the first power line on the basis of the estimated temperature.

Description

Temperature Management Device for Electric Vehicles

[0001] The present invention relates to a temperature management device for electric vehicles.

[0002] In recent electric vehicles, with the increase in the current of the battery, the output performance of the electric motor and the charging performance of the battery have been improved. On the other hand, when the current increases, the heat generation of the power line through which the large current flows increases. Patent Document 1 describes a technique for estimating the temperature of a harness connected to a drive motor in a hybrid vehicle from the current, and reducing the upper limit value of the power supplied to the electrical equipment and the drive motor of the vehicle when the temperature is above a predetermined temperature.

[0003] International Publication No. 2022 / 038718

[0004] The amount of heat generated by the power line can be estimated from the resistance value of the power line and the current value flowing through the power line. Conventionally, when estimating the amount of heat generated, the upper limit value of the resistance specified in advance as the specification of the component is usually used for the resistance value of the power line. The resistance values of the power lines installed in individual electric vehicles vary individually and are often lower than the above-specified upper limit value. Therefore, in conventional temperature management, the actual amount of heat generated is smaller and the actual temperature is lower than the estimated results of the amount of heat generated and the temperature of the power line. Therefore, in conventional temperature management of power lines, unnecessary current limitation occurs, reducing the output performance of the electric motor and the charging performance of the battery.

[0005] An object of the present invention is to provide a temperature management device for an electric vehicle that can suppress an excessive decrease in the output performance of the electric motor or the charging performance of the battery.

[0006] A temperature control device for an electric vehicle according to one embodiment of the present invention is a temperature control device for an electric vehicle mounted on an electric vehicle comprising: drive wheels; an electric motor for driving the drive wheels; a battery for storing power for driving; an inverter for driving the electric motor by receiving power from the battery; and a power line for transmitting power from the battery, wherein the power line includes a first power line for motor drive that transmits power between the battery and the inverter; a first module connected to the first power line via a second power line for driving equipment and capable of measuring the voltage input via the second power line; at least one second module capable of measuring the current flowing through the first power line; and a controller for temperature control, wherein the controller determines and stores the resistance value of the first power line based on the voltage measured by at least the first module and the current measured by the second module; estimates the temperature of the first power line based on the stored resistance value and the current of the first power line during battery discharge; and limits the current of the first power line based on the estimated temperature.

[0007] According to the present invention, the resistance value of the first power line can be measured for each individual electric vehicle, and this resistance value can be used for temperature control. This provides the effect of controlling the temperature of the first power line while suppressing an excessive decrease in the output performance of the electric motor or the charging performance of the battery.

[0008] This is a block diagram showing an electric vehicle equipped with a temperature control device according to Embodiment 1 of the present invention. This is a circuit diagram showing the configuration of the power lines in Figure 1. This is a flowchart showing the procedure for the pumping control process including resistance value acquisition processing. This is a diagram illustrating the resistance values ​​acquired by the resistance value acquisition process. This is a flowchart showing the procedure for the temperature control process executed by the vehicle controller. This is a circuit diagram showing the configuration of the power lines in Embodiment 2 of the present invention. This is a flowchart showing the procedure for the pre-temperature control process including resistance value acquisition processing.

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

[0010] (Embodiment 1) Figure 1 is a block diagram showing an electric vehicle 1 equipped with a temperature control device 30 according to Embodiment 1 of the present invention. Figure 2 is a circuit diagram showing the configuration of the power line 20 in Figure 1. As shown in Figure 1, the temperature control device 30 of Embodiment 1 of the present invention is mounted on an electric vehicle 1. The electric vehicle 1 includes drive wheels 2, a first electric motor 3 that drives several drive wheels 2 (for example, front wheels), a second electric motor 4 that drives several other drive wheels 2 (for example, rear wheels), a first motor control unit 6 that controls the drive of the first electric motor 3, and a second motor control unit 7 that controls the drive of the second electric motor 4. The electric vehicle 1 further includes a battery 5 that stores power for driving, a battery management unit 12 that manages the battery 5, a power line 20 through which power from the battery 5 is transmitted, a DC / DC converter 9 that can step down the voltage of the battery 5 to supply low-voltage power, and an equipment battery 10 that stores the low-voltage power. The electric vehicle 1 further includes a temperature control device 8 for adjusting the temperature of the passenger compartment, the battery 5, or both thereof, an operation control unit 15 that can be operated by the driver, and a vehicle controller 11 that receives operation signals from the operation control unit 15 and outputs operation commands for the first electric motor 3 and the second electric motor 4.

[0011] Battery 5 outputs a high voltage, for example, 100V or more to 800V or more. Battery 5 is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, but various other secondary batteries may be used. Battery 5 is configured by connecting multiple battery cells in series and in parallel.

[0012] The equipment battery 10 outputs a voltage lower than the voltage of the battery 5, for example, a 12V system or a 24V system. The equipment battery 10 is, for example, a lead-acid battery, but various other types of secondary batteries may be used.

[0013] The vehicle controller 11 is an ECU (Electronic Control Unit) that executes a control program stored in the memory unit 11a. The driving operation unit 15 includes a steering unit 15a such as a steering wheel, an acceleration operation unit 15b such as an accelerator pedal, and a braking operation unit 15c such as a brake pedal. The vehicle controller 11 receives signals from the driving operation unit 15 and calculates the torque and other parameters required for the first electric motor 3 and the second electric motor 4 according to those signals. The vehicle controller 11 then sends driving commands for the first electric motor 3 and the second electric motor 4 to the first motor control unit 6 and the second motor control unit 7 so that the torque and other parameters are realized. The driving operation unit 15 further includes a selection operation unit 15d for selecting a driving mode. The driving modes selectable by the selection operation unit 15d may include a front-wheel drive mode that mainly runs on the power of the first electric motor 3, a rear-wheel drive mode that mainly runs on the power of the second electric motor 4, and a four-wheel drive mode that runs on the power of both the first electric motor 3 and the second electric motor 4. The vehicle controller 11 sends driving commands to the first motor control unit 6 and the second motor control unit 7 via the selection operation unit 15d, which realize power distribution according to the selected driving mode.

[0014] As shown in Figure 2, the first motor control unit 6 includes a first inverter 61 that converts power between the battery 5 and the first electric motor 3, a first motor controller 62 that controls the first inverter 61, and a voltage sensor 63 and a current sensor 64 that measure the input voltage and input current of the first inverter 61.

[0015] The second motor control unit 7 includes a second inverter 71 that converts power between the battery 5 and the second electric motor 4, a second motor controller 72 that controls the second inverter 71, and a voltage sensor 73 and a current sensor 74 that measure the input voltage and input current of the second inverter 71.

[0016] The first motor controller 62 and the second motor controller 72 are ECUs and are connected to the vehicle controller 11 via a communication network NE (see Figure 1), such as a CAN (Controller Area Network). Commands and data can be exchanged via the communication network NE. When the first motor controller 62 and the second motor controller 72 receive an operation command from the vehicle controller 11, they drive the first inverter 61 and the second inverter 71 so that the first electric motor 3 and the second electric motor 4 can be driven or regenerated according to the operation command.

[0017] The voltage sensor 63 and current sensor 64 of the first motor control unit 6 send their detection outputs to the first motor controller 62. The voltage sensor 73 and current sensor 74 of the second motor control unit 7 send their detection outputs to the second motor controller 72. The first motor controller 62 and the second motor controller 72 can send the detected voltage and current values ​​to the vehicle controller 11 via the communication network NE.

[0018] The DC / DC converter 9 includes a step-down circuit 91, a voltage sensor 93 and a current sensor 94 capable of measuring voltage and current between input terminals, and a DC / DC controller 92 that controls the operation of the step-down circuit. The detected values ​​from the voltage sensor 93 and the current sensor 94 are sent to the DC / DC controller 92. The DC / DC controller 92 is connected to a communication network NE (see Figure 1) and can receive commands from the vehicle controller 11, and can also send data such as detected voltage and current values ​​to the vehicle controller 11.

[0019] The battery management unit 12 may be a Battery Management System (BMC) that monitors the voltage, temperature, and other conditions of multiple battery cells in the battery 5 and performs processing to maintain the voltage balance of the multiple battery cells. Alternatively, the battery management unit 12 may be a Battery Control Unit (BCU) that estimates the State of Charge (SOC) and State of Health (SOH) of the battery 5, and manages the output power and input power of the battery 5. Alternatively, the battery management unit 12 may be a BMC equipped with the functions of a BCU. The battery management unit 12 has a current sensor 121 and a voltage sensor 122 that measure the current flowing through both terminals of the battery 5 and the voltage between both terminals, respectively. The current sensor 121 and the voltage sensor 122 may directly measure the current at one terminal of the battery 5 and the voltage between both terminals. Alternatively, the current sensor 121 and voltage sensor 122 may be configured to measure the current and voltage values ​​of multiple cells connected in parallel, or the current and voltage values ​​of multiple stacks, each consisting of multiple cells, and to sum these current and voltage values ​​to detect the current flowing through both terminals of the battery 5 and the voltage between the two terminals. The battery management unit 12 is connected to the communication network NE (see Figure 1) and can exchange commands and data with the vehicle controller 11.

[0020] Of the above configuration, the temperature control device 30 of this embodiment is composed of a DC / DC converter 9, a first motor control unit 6, a second motor control unit 7, a vehicle controller 11, a battery management unit 12, and a power line 20. The DC / DC converter 9 corresponds to an example of the first module according to the present invention. The battery management unit 12, the first motor control unit 6, and the second motor control unit 7 each correspond to an example of the second module according to the present invention.

[0021] In this embodiment, the vehicle controller 11 also functions as the controller for the temperature control device 30. The vehicle controller 11 then performs the resistance value acquisition process and the temperature control process for the power line 20, which will be described later. However, the configuration is not limited to this one; a dedicated controller for the temperature control device 30 may be provided, or another controller in the electric vehicle 1 may function as the controller for the temperature control device 30. Furthermore, the controller for the temperature control device 30 may be composed of multiple ECUs, and the multiple ECUs may cooperate to perform the resistance value acquisition process and the temperature control process for the power line 20, which will be described later.

[0022] <Power Lines> As shown in Figure 2, a first power line L1 capable of carrying a large current is provided between the battery 5 and the first inverter 61, and between the battery 5 and the second inverter 71. The first power line L1 is a pair of power lines to which the anode terminal and cathode terminal of the battery 5 are connected, respectively. The first power line L1 is a rigid busbar or a cable with a large diameter and cross-sectional area. The first power line L1 may be covered with a highly heat-resistant coating.

[0023] The first power line L1 has a branch section B1 and includes a first segment Seg1 connecting the battery 5 and the branch section B1, a second segment Seg2 connecting the branch section B1 and the first inverter 61, and a third segment Seg3 connecting the branch section B1 and the second inverter 71. Each of the pair of first power lines L1 includes the first segments Seg1 to the third segments Seg3 and the branch section B1. The anode side of the branch section B1 is denoted as branch section B1a, and the cathode side as branch section B1b.

[0024] The first power line L1 may be provided with relays Ry1 to Ry3 along its path, which can switch the path open and closed. Specifically, relays Ry1 and Ry2 in Figure 2 are system main relays, and when switched to the closed state, power from the battery 5 can be transmitted via the first power line L1. Relay Ry3 is connected in series with the precharge resistor Rp and is a precharge relay to mitigate the inrush current that occurs when relays Ry1 and Ry2 are switched. When the characteristic values ​​(resistance, current, etc.) of the first segment Seg1 are shown below, they represent the characteristic values ​​when relays Ry1 and Ry2 are in the closed state. Because the current paths of relays Ry1 and Ry2 are short, their resistance values ​​are very small compared to the resistance value of the first power line L1.

[0025] The first segment Seg1 to the third segment Seg3 of the first power line L1 each have a wiring resistance (the resistance of the conductors that make up the first power line L1). These wiring resistances are schematically represented as resistances R1 to R3 in Figure 2. That is, resistance R1 in Figure 2 is the resistance of the entire first segment Seg1, and the resistance of a part of the first segment Seg1 is the same value in any part of the first segment Seg1. The same applies to resistances R2 and R3 in Figure 2.

[0026] The DC / DC converter 9 receives power from the battery 5 via a second power line L2 connected in the middle of the first power line L1. The second power line L2 is connected to a branching point B1 of the first power line L1. Note that connection to branching point B1 is not limited to being strictly connected to the branched portion of the first power line L1, but also includes being connected at a position shifted by a short distance from branching point B1. The short distance mentioned above corresponds to a distance in the standard length of the power line of the electric vehicle 1 that allows for negligible error even if the measurement point is shifted when measuring the resistance values ​​of each segment Seg1 to Seg3. Specifically, the short distance is defined as 10 cm or less. Preferably, the short distance is 6 cm or less, and more preferably 3 cm or less.

[0027] <Battery Charging Control Process and Resistance Value Acquisition Process> Figure 3 is a flowchart of the battery charging control process, including the resistance value acquisition process. When the voltage of the equipment battery 10 drops due to discharge during long-term parking of the electric vehicle 1, the vehicle controller 11 performs a battery charging process to transfer power from the battery 5 to the equipment battery 10 via the DC / DC converter 9. Then, during the battery charging process, it performs the resistance value acquisition process H1. The battery charging control process may also be performed when the electric vehicle 1 is being transported for shipment. The battery charging control process makes it possible to suppress the depletion of the charging power of the equipment battery 10 even when the electric vehicle 1 is parked for a long period of time.

[0028] During the pumping control process while transporting the vehicle, the system startup controller for the electric vehicle 1 repeatedly monitors for voltage drops in the equipment battery 10 (step S1). If a voltage drop is detected, in step S2, the system startup controller activates the battery management unit 12 and the vehicle controller 11 to perform the pumping process, and the vehicle controller 11 starts the pumping process (step S2). Note that the order in which the multiple controllers are started, and which controller is the main controller that starts the multiple controllers, are not limited to the above example and can be changed in various ways as appropriate.

[0029] In step S2, when the assembly process begins, the vehicle controller 11 switches relays Ry1 and Ry2 to the closed state, and further activates the first motor controller 62, the second motor controller 72, and the DC / DC controller 92 of the DC / DC converter 9. Although the first inverter 61 and the second inverter 71 are stopped, a small leakage current flows through them when a high voltage is applied. Therefore, the leakage current i2 from the first inverter 61 flows through the second segment Seg2 of the first power line L1, and the leakage current i3 from the second inverter 71 flows through the third segment Seg3. The output current i1 from the battery 5 flows through the first segment Seg1. The output current i1 includes the leakage currents i2 and i3.

[0030] When the power line 20 is in the state described above, the vehicle controller 11 obtains the value of the voltage V5 (see Figure 2) between both terminals of the battery 5 from the battery management unit 12, and also obtains the value of its input voltage V9 (see Figure 2) from the DC / DC converter 9. Then, from these, it calculates the voltage V1 applied to the first segment Seg1 of the first power line L1 (step S3). In Figure 2, the voltage V1 is schematically shown as the voltage applied to resistor R1, but the voltage V1 is (voltage between the first terminal tb1 of the battery 5 and one branch B1a) + (voltage between the other branch B1b and the second terminal tb2 of the battery 5). Note that if current is flowing through the DC / DC converter 9, the voltage drop in the second power line L2 will be an error in the above calculation, so the value of the input voltage V9 of the DC / DC converter 9 sent to the vehicle controller 11 may be the voltage value measured during the period before the step-down operation when no input current is flowing through the DC / DC converter 9. The voltage and current values ​​obtained in the subsequent steps S4, S6, S7, S9, and S10 may also be measured over the same period.

[0031] Next, the vehicle controller 11 obtains the value of current i1 from the battery management unit 12 (step S4). Then, using the voltage V1 calculated in step S3 and the value of current i1 obtained in step S4, it calculates the resistance R1 of the first segment Seg1 of the first power line L1 (step S5).

[0032] Next, the vehicle controller 11 obtains the value of the input voltage V6 of the first inverter 61 from the first motor controller 62, and calculates the voltage V2 applied to the second segment Seg2 of the first power line L1 from the input voltage V6 and the input voltage V9 of the DC / DC converter 9 (step S6). In Figure 2, the voltage V2 is schematically shown as the voltage applied to the resistor R2, but the voltage V2 is (the voltage between one branch B1a and one input terminal ti1 of the first inverter 61) + (the voltage between the other input terminal ti2 of the first inverter 61 and the other branch B1b).

[0033] Next, the vehicle controller 11 obtains the value of the current i2 flowing between the input terminals ti1 and ti2 of the first inverter 61 from the first motor controller 62 (step S7). Then, using the voltage V2 calculated in step S6 and the value of the current i2 obtained in step S7, it calculates the resistance R2 of the second segment Seg2 of the first power line L1 (step S8).

[0034] Next, the vehicle controller 11 obtains the value of the input voltage V7 of the second inverter 71 from the second motor controller 72, and calculates the voltage V3 applied to the third segment Seg3 of the first power line L1 from the input voltage V7 and the input voltage V9 of the DC / DC converter 9 (step S9). In Figure 2, the voltage V3 is schematically shown as the voltage applied to the resistor R3, but the voltage V3 is (the voltage between one branch B1a and one input terminal ti3 of the second inverter 71) + (the voltage between the other input terminal ti4 of the second inverter 71 and the other branch B1b).

[0035] Next, the vehicle controller 11 obtains the value of the current i3 flowing between the input terminals ti3 and ti4 of the second inverter 71 from the second motor controller 72 (step S10). Then, using the voltage V3 calculated in step S9 and the value of the current i3 obtained in step S10, it calculates the resistance R3 of the third segment Seg3 of the first power line L1 (step S11).

[0036] Once the values ​​of resistors R1 to R3 have been calculated, the vehicle controller 11 stores these values ​​in the storage unit 11a as parameters to be used in the temperature control processing of the power line 20 (step S12).

[0037] The resistance value acquisition process H1 in steps S3 to S12 is performed during a period when no large current is flowing through the first segment Seg1 to the third segment Seg3 of the first power line L1, i.e., when the first power line L1 is at room temperature. Therefore, this process makes it possible to calculate the accurate resistance values ​​R1 to R3 of the first power line L1, free from errors caused by heat.

[0038] Next, the vehicle controller 11 starts the DC / DC converter 9 to perform a step-down operation (step S13), determines whether the voltage of the equipment battery 10 exceeds a threshold (step S14), and if it does, stops the DC / DC converter 9 (step S15) and ends the pumping control.

[0039] The pumping control process program or the resistance value acquisition process H1 program described above is stored in a non-transient storage medium (non-transient computer-readable medium), such as the storage unit 11a of the vehicle controller 11. The vehicle controller 11 may be configured to read a program stored in a portable non-transient recording medium and execute the program. The portable non-transient storage medium described above may store the pumping control process program or the resistance value acquisition process H1 program described above.

[0040] Figure 4 illustrates the resistance values ​​obtained by the resistance value acquisition process H1. In Figure 4, the value of resistance R1 is shown as a representative of the resistances R1 to R3, but the same applies to resistances R2 and R3. The bar graph in Figure 4 shows the value of resistance R1 of the first segment Seg1 of the first power line L1 on the vertical axis. The worst value of resistance R1, such as the specification value, and the actual value measured for each of the three identical electric vehicles 1 are shown, respectively. The three identical electric vehicles 1 are referred to as "Vehicle A" to "Vehicle C".

[0041] As shown in Figure 4, the resistance R1 of the first segment Seg1 is lower in actual values ​​(resistance R1 of "Vehicle A" to "Vehicle C") compared to worst-case values ​​such as specification values. Furthermore, even with the same type of electric vehicle 1, there may be variations in resistance R1 for each individual electric vehicle 1 ("Vehicle A" to "Vehicle C"). Therefore, by actually taking measurements, the vehicle controller 11 can grasp the value of resistance R1 of the first segment Seg1 of the first power line L1 with minimal error. When using worst-case values ​​such as specification values, as in the conventional method, errors A to C between the specified value and the actual resistance R1 value result in an overestimation of the heat generation and temperature of the first segment Seg1 compared to the actual case. On the other hand, by using the value of resistance R1 measured for each individual electric vehicle 1, it becomes possible to estimate the heat generation and temperature with less error.

[0042] <Temperature Management Process> Figure 5 is a flowchart showing the procedure for the temperature management process performed by the vehicle controller 11. The temperature management process is performed repeatedly during the system operation of the electric vehicle 1. In the temperature management process, the vehicle controller 11 acquires a measured value of the current of the first power line L1 (step S21). This measured value is the sum of the input current of the first inverter 61 flowing through the second segment Seg2 of the first power line L1, the input current of the second inverter 71 flowing through the third segment Seg3, and the current flowing through the first segment Seg1. Note that currents from other high-voltage devices, including the DC / DC converter 9, also flow through the first power line L1. However, these currents are often negligibly small compared to the currents of the first inverter 61 and the second inverter 71, and therefore, the vehicle controller 11 omits acquiring these currents here. Alternatively, the vehicle controller 11 may simultaneously acquire the currents of other high-voltage devices and calculate the current of the first segment Seg1 by adding these currents. In step S21, the vehicle controller 11 acquires the current values ​​of each of the first segment Seg1 to the third segment Seg3 of the first power line L1.

[0043] Next, the vehicle controller 11 multiplies the values of the resistors R1 to R3 stored in step S12 of FIG. 4 by the current values of each segment acquired in step S21, thereby calculating the heat generation amount of each of the first segment Seg1 to the third segment Seg3 of the first power line L1 (step S22).

[0044] Subsequently, the vehicle controller 11 calculates the magnitude of the cooling effect applied to the first power line L1 (step S23). When air-cooled by outside air, the magnitude of the cooling effect may be calculated from the outside air temperature, outside air flow rate, etc. When water-cooling or the like is performed, the magnitude of the cooling effect may be calculated from the water temperature or the like.

[0045] Then, based on the estimated temperature of the first power line L1 calculated last time (the estimated temperature of each of the first segment Seg1 to the third segment Seg3), the heat generation amount in step S22, and the magnitude of the cooling effect in step S23, the vehicle controller 11 calculates the estimated temperature of each of the first segment Seg1 to the third segment Seg3 of the first power line L1 (step S24).

[0046] Next, the vehicle controller 11 determines whether the estimated temperature of the first power line L1 has reached the first threshold temperature or higher (step S25). If it has reached the threshold or higher, current limiting such as reducing the upper limit current in the segment that has reached the threshold or higher is performed (step S26).

[0047] In addition, the vehicle controller 11 determines whether there is a segment under current limiting (step S27). If there is, it determines whether the estimated temperature of the segment has reached a second threshold temperature that is lower than the first threshold temperature (step S28). If it has reached the threshold or lower, the vehicle controller 11 releases the current limit for the segment (step S29).

[0048] After steps S25 to S29, the vehicle controller 11 ends one temperature management process, and in the next control cycle, repeats the process from step S21 again. By repeating such temperature management processes, it is possible to prevent the first power line L1 through which a large current flows from becoming abnormally hot.

[0049] The temperature control processing method is not limited to the above example. Any method can be adopted as long as it is a control process that prevents the first power line L1 from becoming excessively hot using the values ​​of resistors R1 to R3 stored in the resistance value acquisition process H1. For example, a method may be used in which the temperature of the first power line L1 is measured by a temperature sensor, and the future temperature if the control is continued as is is estimated based on the values ​​of resistors R1 to R3 and the planned current value, and the current is limited so that the estimated temperature does not exceed a threshold.

[0050] The temperature control processing program is stored in a non-transient storage medium, such as the storage unit 11a of the vehicle controller 11. The vehicle controller 11 may be configured to read a program stored in a portable non-transient recording medium and execute the program. The portable non-transient storage medium may store the temperature control processing program described above.

[0051] As described above, the temperature control device 30 of Embodiment 1 includes a first power line L1 for motor drive that transmits power between the battery 5 and the first inverter 61 and the second inverter 71, and a DC / DC converter 9 (corresponding to the first module) connected to the first power line L1 via a second power line L2. The DC / DC converter 9 can measure the input voltage V9 applied to the second power line L2. Furthermore, in the temperature control device 30, the first power line L1 is provided with a battery management unit 12, a first motor control unit 6, and a second motor control unit 7 that can measure the current flowing through the first power line L1. Therefore, the vehicle controller 11 can calculate the resistances R1 to R3 of the first power line L1 using the voltage and current values ​​measured by these units. Furthermore, in the temperature management process, the vehicle controller 11 can estimate the temperature of the first power line L1 based on the calculated resistance values ​​R1 to R3 and the current of the first power line L1, and perform temperature management processing to limit the current of the first power line L1 according to the estimated temperature. Note that the above temperature estimation and current limiting may be performed while the battery 5 is discharging or while the battery 5 is charging.

[0052] With the above configuration, the temperature control process for the first power line L1 is performed using the resistances R1 to R3 measured in each electric vehicle 1. Compared to estimating the temperature using the worst-case resistance value such as the specification value, it is possible to estimate the temperature with less margin and with greater accuracy. Therefore, temperature control of the first power line L1 with less margin can be achieved. Consequently, excessive intervention of current limiting of the first power line L1, such as lowering the upper limit current, can be reduced, and the deterioration of the output characteristics of the electric vehicle 1 and the regenerative charging characteristics of the battery 5 caused by excessive intervention of current limiting can be suppressed.

[0053] Furthermore, according to the temperature control device 30 of Embodiment 1, the DC / DC converter 9 is a module that operates using power input via the second power line L2, the first power line L1 has a branch section B1, and the second power line L2 is connected to the branch section B1. Therefore, the DC / DC converter 9 makes it possible to measure the voltage at the branch section B1, and to accurately measure the resistances R2 and R3 of each segment branched off from the first power line L1 at the branch section B1.

[0054] Furthermore, according to the temperature control device 30 of Embodiment 1, it includes a first electric motor 3 and a second electric motor 4 driven by the power of the battery 5, a first inverter 61 that drives the first electric motor 3, and a second inverter 71 that drives the second electric motor 4. The first inverter 61 and the second inverter 71 are provided in the second segment Seg2 and the third segment Seg3 that branch off from the first power line L1. In addition, the first power line L1 is connected to a battery management unit 12 capable of measuring the current flowing through the first segment Seg1, a first motor control unit 6 capable of measuring the current flowing through the second segment Seg2, and a second motor control unit 7 capable of measuring the current flowing through the third segment Seg3, so that the current of each segment can be measured. Therefore, without providing dedicated current and voltage sensors to measure resistances R1 to R3, the resistances R1 to R3 of the first segment Seg1 to the third segment Seg3 can be measured using a module provided in the electric vehicle 1 having multiple electric motors (first electric motor 3 and second electric motor 4). Thus, the number of additional components required to measure resistance values ​​can be reduced.

[0055] Furthermore, according to the temperature control device 30 of Embodiment 1, the vehicle controller 11 executes a resistance value acquisition process H1 when performing pumping control to transfer power from the DC / DC converter 9 to the equipment battery 10, and acquires the values ​​of the resistances R1 to R3 of the first power line L1. During the pumping control period, the DC / DC converter 9 is running, so the voltage V9 at the branch section B1 can be measured by the DC / DC converter 9. Therefore, it is possible to measure the resistance value with less waste compared to starting the dormant DC / DC converter 9 in order to measure the voltage V9. Also, during pumping control, the electric vehicle 1 is in a dormant state immediately beforehand, and the first power line L1 is at room temperature. Therefore, the resistance value of the first power line L1 at room temperature can be acquired. Furthermore, during the pumping control period, a small leakage current flows when a high voltage is applied to the first inverter 61 and the second inverter 71. Therefore, by utilizing this leakage current, the resistance value of the first power line L1 can be acquired stably with low power consumption.

[0056] (Embodiment 2) Figure 6 is a circuit diagram showing the configuration of the power lines in Embodiment 2 of the present invention. In Embodiment 2, the temperature control device 30 is configured with a temperature control device 8 as a first module connected to the first power line L1 via the second power line L2.

[0057] The temperature control device 8 may be any temperature control unit that operates on the power of the battery 5, such as a heater device for adjusting the temperature inside the passenger compartment, a compressor device for a heat pump that cools and dehumidifies the passenger compartment, or a battery heater device that heats the battery 5 when the temperature is low.

[0058] As shown in Figure 6, the temperature control device 8 includes a temperature control device 81 such as a heater or compressor, a temperature control controller 82 that controls the temperature control device 81, and a voltage sensor 83 and a current sensor 84 that measure the input voltage and input current of the temperature control device 81, respectively. The detected values ​​of the voltage sensor 83 and the current sensor 84 are sent to the temperature control controller 82. The temperature control controller 82 is connected to a communication network NE (see Figure 1) and can receive commands from the vehicle controller 11, and can also send data such as detected voltage and current values ​​to the vehicle controller 11.

[0059] The temperature control device 8 receives power from the battery 5 via a second power line L2 connected in the middle of the first power line L1. The second power line L2 is connected to the branching point B1 of the first power line L1. Note that connection to the branching point B1 is not strictly limited to a connection to the branched portion of the first power line L1, but includes connections with slight deviations as described in Embodiment 1.

[0060] <Pre-temperature control processing and resistance value acquisition processing> Figure 7 is a flowchart showing the procedure for pre-temperature control processing, including resistance value acquisition processing. While the electric vehicle 1 is idle, the vehicle controller 11 repeatedly determines whether it is the pre-temperature control time based on the user's set scheduled start time for driving, or whether the user has input a command to perform pre-temperature control (step S31). The pre-temperature control time is a predetermined time before the scheduled start time for driving. If either is YES, the vehicle controller 11 starts the temperature control processing from step S32. In step S32, the vehicle controller 11 switches relays Ry1 and Ry2 to the closed state and starts the temperature control device 8 (step S32).

[0061] Next, the vehicle controller 11 executes the resistance value acquisition process H2 in steps S3A to S12A. The resistance value acquisition process in steps S3A to S12A is the same as the process in steps S3 to S12 of Figure 3 described above, except that the input voltage V8 of the temperature control device 8 is applied instead of the input voltage V9 of the DC / DC converter 9. The resistance value acquisition process H2 in steps S3A to S12A may be executed before the temperature control device 8 supplies the pre-temperature control current in order to reduce errors due to the resistance of the second power line L2.

[0062] In the resistance value acquisition process in steps S3A to S12A of Embodiment 2, similar to Embodiment 1, the values ​​of the resistances R1 to R3 of the first segment Seg1 to the third segment Seg3 of the first power line L1 can be accurately calculated and stored. Furthermore, in Embodiment 2 as well, the resistance value acquisition process H2 can be performed during periods when no large current is flowing through the first segment Seg1 to the third segment Seg3 of the first power line L1, i.e., at room temperature of the first power line L1. Therefore, the accurate resistances R1 to R3 of the first power line L1, free from heat-related errors, can be calculated.

[0063] Once the resistances R1 to R3 have been calculated and stored, the vehicle controller 11 starts the temperature control device 8 (step S33) and repeatedly checks whether a specified time has elapsed or whether a specified temperature has been reached (step S34). If the result is YES, the vehicle controller 11 stops the temperature control device 8 (step S35) and terminates the pre-temperature control process.

[0064] <Temperature Control Processing> In the temperature control processing of Embodiment 2, the temperature of the first power line L1 is controlled in the same way as in Embodiment 1, using the values ​​of resistors R1 to R3 obtained during the pre-temperature control processing.

[0065] As described above, the temperature control device 30 of Embodiment 2 includes a temperature control device 8 connected to the first power line L1 via a second power line L2. The temperature control device 8 can measure the input voltage V8 applied via the second power line L2. Furthermore, similar to Embodiment 1, the first power line L1 is provided with a battery management unit 12, a first motor control unit 6, and a second motor control unit 7, which can measure the current flowing through the first power line L1. Therefore, the vehicle controller 11 can measure the resistances R1 to R3 of the first power line L1 using the voltage and current values ​​measured by these units. Thus, in Embodiment 2, as in Embodiment 1, temperature control processing with a small margin on the first power line L1 is realized, and a decrease in the output characteristics of the electric vehicle 1 and a decrease in the regenerative charging characteristics of the battery 5 caused by excessive intervention of current limiting can be suppressed.

[0066] Furthermore, according to the temperature control device 30 of Embodiment 2, the vehicle controller 11 executes a resistance value acquisition process H2 during pre-temperature control processing. During the pre-temperature control processing period, the temperature control device 8 is activated, so the voltage V8 at the branch section B1 can be measured by the temperature control device 8. Therefore, it is possible to acquire a resistance value with less waste compared to activating the idle temperature control device 8 in order to measure the voltage V8. Also, during pre-temperature control processing, the electric vehicle 1 is often idle immediately beforehand, and the first power line L1 is at room temperature. Therefore, the resistance value of the first power line L1 at room temperature can be acquired. Furthermore, during the pre-temperature control period, a small leakage current flows through the first inverter 61 and the second inverter 71 due to the application of high voltage. Therefore, by utilizing this leakage current, the resistance value of the first power line L1 can be acquired stably with low power consumption.

[0067] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiments, a configuration having a plurality of electric motors (first electric motor 3 and second electric motor 4) and a first power line L1 having branched first segments Seg1 to third segments Seg3 was described as one example. However, there may be only one electric motor that outputs the power for driving, and the first power line L1 may not have a branch section B1. Furthermore, even in a configuration having a plurality of electric motors, the plurality of electric motors may be electric motors that are combined with various drive wheels, for example, an electric motor that drives the left drive wheel and an electric motor that drives the right drive wheel.

[0068] Furthermore, in the above embodiment, an example was shown in which a DC / DC converter 9 and a temperature control device 8 were used as the first module connected to the first power line L1 via the second power line L2. However, the first module can be any module that operates on the voltage of the battery 5.

[0069] Furthermore, in the above embodiment, examples were shown in which the resistance value acquisition process is performed during the assembly process and during the pre-temperature control process. However, the resistance value acquisition process may be performed at various timings. For example, even while the electric vehicle 1 is running, the current flowing to the second inverter 71 decreases when it is running in front-wheel drive mode, and the current flowing to the first inverter 61 decreases when it is running in rear-wheel drive mode. Therefore, when running in either drive mode, the resistance of the segment with the lower current can be calculated by measuring the voltage and current in the same way as shown in the above embodiment. Other details shown in the embodiment can be modified as appropriate without departing from the spirit of the invention.

[0070] This invention can be used in temperature control devices for electric vehicles.

[0071] 1 Electric vehicle 2 Drive wheels 3 First electric motor 4 Second electric motor 5 Battery 6 First motor control unit 61 First inverter 62 First motor controller 63 Voltage sensor 64 Current sensor 7 Second motor control unit 71 Second inverter 72 Second motor controller 73 Voltage sensor 74 Current sensor 8 Temperature control device 81 Temperature control device 82 Temperature control controller 83 Voltage sensor 84 Current sensor 9 DC / DC converter 91 Step-down circuit 92 DC / DC controller 93 Voltage sensor 94 Current sensor 10 Equipment battery 11 Vehicle controller 12 Battery management unit 15 Operation unit 20 Power line 30 Temperature control device NE Communication network L1 First power line L2 Second power line Seg1 First segment Seg2 Second segment Seg3 Third segment B1 Branch H1, H2 Resistance value acquisition process R1-R3 Resistors

Claims

1. A temperature control device for an electric vehicle, mounted on an electric vehicle comprising: drive wheels; an electric motor for driving the drive wheels; a battery for storing power for driving; an inverter for driving the electric motor using power from the battery; and a power line for transmitting power from the battery, wherein the power line includes a first power line for motor drive that transmits power between the battery and the inverter; a first module connected to the first power line via a second power line for equipment drive and capable of measuring the voltage input via the second power line; at least one second module capable of measuring the current flowing through the first power line; and a controller for temperature control, wherein the controller determines and stores the resistance value of the first power line based on the voltage measured by at least the first module and the current measured by the second module; estimates the temperature of the first power line based on the stored resistance value and the current of the first power line during battery discharge; and limits the current of the first power line based on the estimated temperature.

2. The temperature control device for an electric vehicle according to claim 1, wherein the first module is a module that operates by power input via the second power line, the first power line has a branching section, and the first module is connected to the branching section via the second power line.

3. The electric motor includes a first electric motor and a second electric motor; the inverter includes a first inverter for driving the first electric motor and a second inverter for driving the second electric motor; the first power line includes a first segment between the battery and the branching section, a second segment between the branching section and the first inverter, and a third segment between the branching section and the second inverter; the second module includes a battery management unit capable of measuring the output current of the battery, a first motor control unit including the first inverter and capable of measuring the current of the second segment, and a second motor control unit including the second inverter and capable of measuring the current of the third segment, the temperature control device for an electric vehicle according to claim 2.

4. The temperature control device for an electric vehicle according to claim 1, wherein the first module is a DC / DC converter that reduces the voltage of the battery, the electric vehicle is equipped with an equipment battery that stores power at a lower voltage than the battery, and the controller performs pumping control to drive the DC / DC converter to transfer power from the battery to the equipment battery when the amount of charge stored in the equipment battery decreases while the electric vehicle is stopped, and determines the resistance value during the pumping control.

5. The temperature control device for an electric vehicle according to claim 1, wherein the first module is a temperature control device driven by the power of the battery, the controller performs pre-driving temperature control to drive the temperature control device while the electric vehicle is parked, and determines the resistance value during the pre-driving temperature control.

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