Electric vehicle control method and electric vehicle control device

Abstract

This prevents the battery from running out of power even if the power from the charger drops during charging, which involves warming up the in-vehicle device. [Solution] An electric vehicle control method in which a controller determines whether or not an in-vehicle device needs to be warmed up, and if warming up is necessary, performs warm-up control using the waste heat of the electric powertrain to warm up the in-vehicle device, characterized in that when warm-up control is performed while charging with power from an external charger, if the power from the external charger is insufficient for the power required to perform the warm-up control, the insufficient power is supplied from the battery, and if the battery charge state falls below a predetermined charge state threshold during the execution of warm-up control, the permitted power for use by the electric powertrain for warm-up control is reduced.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electric vehicle control method and an electric vehicle control device.

BACKGROUND ART

[0002] Regarding control of an electric vehicle that can be charged with electric power from an external charger (charging station), Patent Document 1 discloses that even when the electric power supplied from the charging station decreases, charging stop control is not performed if the decrease in the stored electricity amount of the high-voltage battery falls within an allowable range.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] By the way, a battery has a characteristic that the lower the temperature, the smaller the input and output current values. When the battery temperature is low, battery warm-up control is known, in which a current that does not contribute to torque is passed through the electric motor of the electric powertrain to cause the electric motor to generate heat, and the waste heat therefrom is used to raise the temperature of the battery.

[0005] When this battery warm-up control is implemented during charging, a portion of the power from the charger is supplied to the electric powertrain. However, the control described in the above-mentioned document does not take this into consideration. In other words, if the power from the charger decreases during charging with battery warm-up control, the reduced power must be drawn from the high-voltage battery in order to continue the battery warm-up control. This reduces the charge stored in the high-voltage battery, and there is a risk that the high-voltage battery will run out of power. Furthermore, when other on-board devices of the high-voltage battery, such as the heating function of the cabin air conditioning system, are used during charging, a portion of the power from the charger is supplied to the cabin air conditioning system to raise the temperature of the refrigerant (i.e., to warm up the cabin air conditioning system). Therefore, if the power supplied from the charger decreases, there is a similar risk that the charge stored in the high-voltage battery will decrease.

[0006] Therefore, the present invention aims to provide a control system that can prevent the battery from becoming completely depleted even if the power from the charger decreases during charging, which involves warming up the in-vehicle device. [Means for solving the problem]

[0007] According to one aspect of the present invention, an electric vehicle control method is provided in which a controller determines whether or not an in-vehicle device needs to be warmed up, and if warming up is necessary, performs warming up of the in-vehicle device using waste heat from the electric powertrain. In this method, when the controller performs warm-up control while charging with power from an external charger, if the power from the external charger is insufficient to perform the warm-up control, the controller supplies the insufficient power from the battery. Furthermore, if the battery charge level falls below a predetermined charge threshold during the warm-up control, the controller reduces the permitted power for use by the electric powertrain for warm-up control. [Effects of the Invention]

[0008] According to the above embodiment, even if the power from the charger decreases during charging with the vehicle device warming up, it is possible to prevent the battery from becoming completely depleted. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a block diagram showing the control system of an electric vehicle. [Figure 2] Figure 2 is a flowchart showing the control routines executed by the control system. [Figure 3] Figure 3 is an example of a time chart when the control routine shown in Figure 2 is executed. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] [System Configuration] Figure 1 is a block diagram showing the configuration of the control system that performs the control according to this embodiment. The target of control in this embodiment is an electric vehicle that can be charged using power supplied from an external charger.

[0012] This control system comprises a controller 1 as the control unit, a BMS (Battery Management System) 2, an HVAC (Heating, Ventilation and Air Conditioning) system 3, and an electric powertrain (e-PT in the diagram) 4.

[0013] Controller 1 comprises a water circuit control unit 5, a battery warm-up permission determination unit 6, and a high-voltage control unit 7. In Figure 1, the water circuit control unit 5, battery warm-up permission determination unit 6, and high-voltage control unit 7 are shown as blocks; however, this does not represent their physical configuration, but rather their respective functions. Furthermore, Controller 1 is composed of a microcomputer equipped with a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure Controller 1 with multiple microcomputers.

[0014] The BMS2 is a system that monitors battery conditions (not shown in the diagram), such as voltage, current, temperature, and battery coolant temperature, and calculates the amount of charge from the current charge and the battery's state of charge (SOC) based on these conditions, and controls charging and discharging accordingly.

[0015] HVAC system 3 is a so-called air conditioning control system that provides heating, ventilation, and air conditioning for the vehicle interior.

[0016] The electric powertrain 4 includes an electric motor (not shown) for vehicle propulsion and an inverter (not shown) for controlling the electric motor.

[0017] Controller 1 performs various processes based on the information obtained from BMS2. Information is exchanged between Controller 1 and BMS2 via so-called CAN communication.

[0018] The battery warm-up permission determination unit 6 determines whether to allow or disallow battery warm-up control based on the battery temperature, battery SOC, battery warm-up on / off threshold, etc., obtained from the BMS2, and transmits the determination result as a warm-up implementation flag to the water circuit control unit 5 and the high-voltage control unit 7. Battery warm-up control, as referred to here, is a control to promote the temperature rise of the battery when it is cold. Specifically, it involves flowing a current component that does not contribute to torque (d-axis current) through the electric motor to generate heat, recovering the waste heat with battery cooling water, and raising the temperature of the battery.

[0019] The water circuit control unit 5 controls the cooling water circuit (also called the water circuit) based on the battery temperature and battery cooling water temperature obtained from the BMS2, the warm-up execution flag obtained from the battery warm-up permission determination unit 6, and the waste heat recovery request obtained from the HVAC system 3. It also transmits water circuit information such as cooling water temperature and cooling water flow rate to the HVAC system 3.

[0020] The high-voltage control unit 7 controls high-voltage devices such as the electric powertrain 4 and the HVAC system 3, based on the battery state of charge acquired from the BMS 2, the warm-up execution flag acquired from the battery warm-up permission determination unit 6, the battery warm-up request acquired from the HVAC system 3, and the like. Note that the "battery warm-up request" from the HVAC system 3 to the high-voltage control unit 7 is issued when the temperature rise of the cooling water is required to ensure the heating function.

[0021] [Battery Warm-up Control] As described above, the battery has a characteristic that the lower the temperature, the smaller the input and output current values. Therefore, when the battery temperature is low, battery warm-up control using waste heat from the electric motor is performed to promote temperature rise.

[0022] When performing battery warm-up control in a non-charging state, for example before the start of traveling, the electric power for causing the electric motor to generate heat is supplied by the battery. On the other hand, when performing battery warm-up control during charging with electric power supplied from an external charger, the control is performed by supplying part of the electric power supplied from the charger to the electric motor. This is because it is appropriate not to consume the electric power of the battery in light of the charging purpose of increasing the battery SOC.

[0023] Here, a problem arises when the electric power supplied from the charger decreases for some reason (such as power restriction or failure). From the viewpoint of charging efficiency, it is desirable to continue the battery warm-up control to increase the input current of the battery. Therefore, the BMS 2 requests the controller 1 for the electric power required for the battery warm-up control regardless of the magnitude of the electric power supplied from the charger. However, when the electric power supplied from the charger becomes smaller than the electric power required for the battery warm-up control, the electric power of the battery has to be used to continue the battery warm-up control. If the battery warm-up control is continued in such a state, there is a risk that the battery will run out of electricity depending on the battery SOC.

[0024] Therefore, in this embodiment, even if the power supplied from the charger decreases, the control described below is performed to continue battery warm-up control during charging and to prevent the battery from becoming depleted.

[0025] Figure 2 is a flowchart showing the control routine executed by the control system described above. This control routine is executed repeatedly whenever the electric vehicle starts charging using power from an external charger.

[0026] In step S100, the controller 1 determines whether battery warm-up control is necessary. If necessary, it proceeds to step S110; otherwise, it terminates the routine. The determination of whether battery warm-up control is necessary is based on the battery temperature. For example, the battery temperature may be estimated from the coolant temperature of the HVAC system 3, and if the estimated battery temperature is lower than a preset battery warm-up on / off threshold, it may be determined that battery warm-up control is necessary. The battery warm-up on / off threshold is a value that can be arbitrarily set according to the performance of the battery.

[0027] In step S110, controller 1 starts battery warm-up control. The details of the battery warm-up control are as described above. Specifically, a portion of the power supplied from the charger is used to supply a current (d-axis current) to the electric motor that does not contribute to torque, thereby generating heat in the electric motor. The waste heat from the electric motor is recovered by circulating cooling water, and the battery is heated up using the now-high temperature cooling water. If the power from the external charger is insufficient to perform the warm-up control, the battery is used to supply the remaining power.

[0028] In step S120, controller 1 determines whether the current battery SOC is less than the battery SOC at the start of charging. If it is less, it proceeds to step S130; otherwise, it terminates the routine. The current battery SOC and the battery SOC at the start of charging are obtained from BMS2, which constantly monitors the battery SOC based on the battery's input / output current values.

[0029] This step is for determining whether the power supplied by the charger has decreased. Therefore, the threshold used for the determination does not have to be the battery SOC at the start of charging, as long as it is possible to detect a decrease in the power supplied by the charger. This will be explained later. In this embodiment, the amount of power supplied by the charger is not directly monitored, so this method is used to determine whether the power supplied by the charger has decreased. Therefore, if the configuration allows for direct monitoring of the amount of power supplied by the charger, the determination may be made based on the amount of power being monitored.

[0030] In step S130, the controller 1 reduces the power used for battery warm-up (hereinafter referred to as the permitted power). That is, in this control routine, the permitted power is reduced when the battery SOC becomes smaller than the value at the start of charging. This makes it possible to mitigate the rate at which the battery SOC decreases when battery warm-up control is continued. The method of reducing the permitted power is arbitrary. For example, the amount of power supplied to the electric powertrain may be divided into multiple permitted power ranges, and the controller may switch to a permitted power range smaller than the current permitted power range.

[0031] Controller 1, after setting the permitted power range, transmits information about the permitted power range to the electric powertrain 4. While it is possible to transmit the permitted power range as an analog value, in this embodiment, the permitted power range is converted to a digital signal before transmission. For example, signals W1, W2, W3, etc., are assigned to multiple permitted power ranges, and these signals are transmitted. This reduces the CAN bus load compared to transmitting the values ​​as analog.

[0032] Furthermore, reducing the permitted power output increases the input current to the battery. For this reason, if the permitted power output is abruptly reduced to zero, the input current to the battery will increase sharply, and if the battery's State of Charge (SOC) is close to full charge, there is a risk of overcharging. Therefore, in this embodiment, the permitted power output is controlled to decrease by a predetermined percentage. For example, multiple permitted power output ranges are set, and the system is gradually switched to a range with lower power output.

[0033] In step S140, the electric powertrain 4 converts the digital signal received from the controller 1 into an authorized power range and sets the current value to be supplied to the electric motor based on the authorized power range. For example, it sets the current value to correspond to the minimum power within the authorized power range. Setting the current value to correspond to the minimum power ensures that the electric powertrain 4 will not be supplied with excessive power, regardless of what value the actually usable power is within the authorized power range.

[0034] In step S150, the controller 1 determines whether the current battery SOC obtained from the BMS2 has recovered to the battery SOC at the start of charging. If it has recovered, it proceeds to step S160; otherwise, it returns to step S130. As a result, if the battery SOC continues to decrease while this control routine is repeated, the power supplied to the electric powertrain will gradually decrease.

[0035] In step S160, the controller 1 increases the permitted power range and transmits information about the increased permitted power range as a digital signal to the electric powertrain 4. Then, in step S170, the electric powertrain 4 sets the current value to be supplied to the electric motor based on the received digital signal. The CAN communication between the controller 1 and the electric powertrain 4 in steps S150 and S160 is the same as in steps S130 and S140.

[0036] As described above, once the battery SOC recovers, the power supplied to the electric powertrain is restored to its original level.

[0037] In step S180, the controller 1 determines whether the current battery SOC obtained from the BMS2 is greater than or equal to the battery SOC at the start of charging. If it is greater, it proceeds to step S190; otherwise, it returns to step S130.

[0038] In step S190, the controller 1 determines whether the permitted power has recovered to the level at the start of charging through the processing in steps S160 and S170. If it has recovered, the current routine is terminated; otherwise, the process returns to step S160.

[0039] Figure 3 shows an example of a time chart when the above control routine is executed. This example shows the case where charging starts at timing T0, and then the power supplied from the charger decreases at timing T1.

[0040] Charging begins at timing T0, and battery warm-up control also starts. From timing T0 to timing T1, the battery state of charge (SOC) increases. This is because a portion of the power supplied by the charger is used for battery warm-up control, while the remainder is used for battery charging.

[0041] At timing T1, if the power supplied from the charger decreases for any reason, the battery SOC will start to decrease. This is because the power supplied from the charger becomes less than the power required for battery warm-up control, and the battery is drawing power from the battery to compensate for the insufficient power needed to continue the battery warm-up control. However, as mentioned above, the power supplied from the charger is not directly monitored, so at this point, controller 1 has not detected the decrease in power supplied from the charger.

[0042] When the current battery SOC falls below the battery SOC at the start of charging at timing T2, controller 1 determines that the power supplied from the charger has decreased. Then, from timing T2 to timing T6, while the current battery SOC is lower than the battery SOC at the start of charging, the permitted power is gradually reduced, and the current value of the electric powertrain decreases accordingly. Specifically, the permitted power is gradually reduced within the permitted power range of digital signal W1 at timings T2 to T3, within the permitted power range of digital signal W2 at timings T3 to T4, and within the permitted power range of digital signal W3 at timings T4 to T5. Accordingly, the current value becomes the smallest value within each permitted power range.

[0043] Then, at timing T6, once the current battery SOC has recovered to the battery SOC at the start of charging, the authorized power for use begins to be restored to its original value.

[0044] By executing the above control routine, it is possible to prevent the battery from running out of power.

[0045] In this embodiment, the case where the battery SOC at the start of charging is used as the charge state threshold has been described, but the battery SOC at the start of battery warm-up control may also be used as the charge state threshold. For example, even if it is determined that battery warm-up is not necessary at the start of charging, battery warm-up control may be performed during charging due to changes in the environment, etc. In this case, using the battery SOC at the start of battery warm-up control as the charge state threshold allows for a quicker determination of the decrease in power supplied from the charger. Alternatively, the charge state threshold may be the battery SOC at the start of charging or the battery SOC at the start of battery warm-up control, as well as the charging time, etc., at which it can be determined that the power from the charger has clearly decreased. Furthermore, since there may be a delay between detecting a decrease in power from the charger and the actual decrease in the current value of the electric powertrain, the charge state threshold may be the battery SOC that takes this delay into account for each of the above battery SOCs.

[0046] As described above, this embodiment provides an electric vehicle control method in which the controller 1 determines whether or not the on-board device needs to be warmed up, and if warming up is necessary, it performs warming up of the on-board device using the waste heat of the electric powertrain. In this method, when the controller 1 performs warm-up control while charging with power from an external charger, if the power from the external charger is insufficient to perform the warm-up control, it supplies the insufficient power from the battery. Furthermore, if the battery's charge state falls below a predetermined charge state threshold during the warm-up control, the controller 1 reduces the permitted power for use by the electric powertrain 4 for warm-up control. This prevents the battery from becoming depleted during charging accompanied by warming up of the on-board device.

[0047] In this embodiment, when the controller 1 reduces the permitted power usage, it reduces it by a predetermined percentage to prevent battery overcharging. This suppresses battery degradation caused by the control according to this embodiment.

[0048] In this embodiment, the controller 1 sets multiple permitted power ranges, sets a digital signal indicating each permitted power range, and transmits the digital signal to the electric powertrain 4 via CAN. This reduces the bus load on the CAN.

[0049] In this embodiment, upon receiving a digital signal, the electric powertrain 4 performs current value control at the minimum value within the permitted power range indicated by the digital signal.

[0050] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. [Explanation of Symbols]

[0051] 1. Controller, 2. BMS, 3. HVAC system, 4. Electric powertrain

Claims

1. In an electric vehicle control method, a controller determines whether or not an in-vehicle device needs to be warmed up, and if warming up is necessary, it performs warm-up control using waste heat from the electric powertrain to warm up the in-vehicle device, When performing the warm-up control while charging with power from an external charger, If the power from the external charger is insufficient to perform the warm-up control described above, the remaining power will be supplied from the battery. An electric vehicle control method characterized in that, if the charge state of the battery falls below a predetermined charge state threshold during the execution of the warm-up control, the permitted power for use in the electric powertrain for the warm-up control is reduced.

2. In the electric vehicle control method described in claim 1, The controller prevents overcharging of the battery by reducing the permitted power by a predetermined percentage when the power to be used is reduced.

3. In the electric vehicle control method described in claim 1, The controller sets a plurality of permitted power ranges, sets a digital signal indicating each permitted power range, and transmits the digital signal to the electric powertrain via CAN, in an electric vehicle control method.

4. In the electric vehicle control method described in claim 3, An electric vehicle control method comprising: an electric powertrain that, upon receiving the digital signal, performs current value control at the minimum value within the permitted power range indicated by the digital signal.

5. An electric vehicle control device comprising a control unit that determines whether or not an in-vehicle device needs to be warmed up, and if warming up is necessary, performs warm-up control that uses the waste heat of the electric powertrain to warm up the in-vehicle device, An electric vehicle control device characterized in that, when the control unit performs the warm-up control while charging with power from an external charger, if the power from the charger is insufficient to perform the warm-up control, it supplies the insufficient power from the battery, and if the charge state of the battery falls below a charge state threshold determined based on the charge state at the start of charging while the warm-up control is being performed, it reduces the permitted power for use by the electric powertrain for the warm-up control.

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