Charging system and vehicle

Abstract

To provide a charging system capable of suppressing occurrence of lithium deposition in a lithium ion battery when power generation of a motor generator (MG) cannot be appropriately controlled.SOLUTION: A charging system mounted on a vehicle includes: an MG; a lithium ion battery that accumulates electric power generated by the MG; a relay that electrically connects the MG and the lithium ion battery; a first control unit that acquires battery information including a temperature, a current, and a use period of the lithium ion battery and instructs an amount of power generated by the MG based on the battery information; and a second control unit that controls an operation of the MG in accordance with an instruction from the first control unit. When interruption of an instruction to the second control unit is detected, the first control unit calculates, based on the battery information, allowable charge power which is an upper limit value of the charge power to the lithium ion battery in which lithium deposition does not occur, and cuts off the relay when a state in which the allowable charge power is less than the predetermined power continues for a predetermined time or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a charging system that controls the charging of a lithium-ion battery mounted on a vehicle, etc.

Background Art

[0002] When a lithium-ion battery is further charged in a state where the state of charge (SOC) is high or charged in an extremely low temperature state, a phenomenon (lithium precipitation) occurs in which lithium metal that leads to battery deterioration precipitates. Therefore, various techniques for suppressing the occurrence of lithium precipitation have been proposed for lithium-ion batteries.

[0003] Patent Document 1 discloses a system for charging a lithium-ion battery with the power generated by a motor generator in a hybrid vehicle. In the system described in this Patent Document 1, an electronic control unit that monitors the state of the lithium-ion battery controls an electronic control unit that controls the motor generator so that the power (charging power) input from the motor generator to the lithium-ion battery is equal to or less than an input limit power value that can suppress the occurrence of lithium precipitation. An operation command is issued.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the system described in the above Patent Document 1, for example, when the electronic control unit that monitors the state of the lithium-ion battery fails to receive an operation command transmitted from the electronic control unit due to a cause such as a communication interruption, the power generation of the motor generator cannot be appropriately controlled based on the input limit power value. For this reason, the motor generator may generate excessive power, and lithium precipitation may occur in the lithium-ion battery.

[0006] The present disclosure has been made in view of the above problems, and an object thereof is to provide a charging system and the like that can suppress the occurrence of lithium precipitation in a lithium-ion battery when the power generation of the motor generator cannot be appropriately controlled.

Means for Solving the Problems

[0007] In order to solve the above problems, one aspect of the disclosed technology is a charging system mounted on a vehicle, including a motor generator, a lithium-ion battery that stores the power generated by the motor generator, a relay that electrically connects the motor generator and the lithium-ion battery, a first control unit that acquires battery information including the temperature, current, and usage period of the lithium-ion battery and instructs the power generation amount of the motor generator based on the battery information, and a second control unit that controls the operation of the motor generator according to an instruction from the first control unit. When the first control unit detects an interruption in the instruction to the second control unit, the first control unit calculates a charging allowable power, which is the upper limit value of the charging power to the lithium-ion battery where lithium precipitation does not occur, based on the battery information, and shuts off the relay if the state where the charging allowable power is less than a predetermined power continues for a predetermined time or more.

Effects of the Invention

[0008] According to the charging system of the present disclosure, when the instruction to the motor generator is interrupted and power generation cannot be appropriately controlled, the relay is cut off by predicting a state in which lithium precipitation is likely to occur in the lithium-ion battery. Thereby, the occurrence of lithium precipitation in the lithium-ion battery can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0010] When the motor generator that charges the lithium-ion battery of the charging system of the present disclosure becomes unable to control power generation, if there is a possibility of lithium precipitation in the lithium-ion battery, the charging path from the motor generator to the lithium-ion battery is electrically disconnected. Thereby, the generated power of the motor generator is not supplied to the lithium-ion battery 111, and the occurrence of a phenomenon in which lithium metal precipitates beyond the limit of the lithium-ion battery 111 can be avoided. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] <Embodiment> [Configuration] FIG. 1 is a block diagram showing a schematic configuration example of a charging system 100 according to an embodiment of the present disclosure. In FIG. 1, the charging system 100 includes a battery pack 110, a first control unit 120, an MG unit 130, and a DCDC converter 140. In FIG. 1, power lines for power transfer are shown by solid lines, and signal lines through which detection values, instructions, etc. flow are shown by broken lines. This charging system 100 is mounted on a vehicle such as a hybrid electric vehicle (HEV) having an internal combustion engine as a power source.

[0012] The battery pack 110 is a power source that can supply power to the MG unit 130 and auxiliary systems of the vehicle (not shown) or store the power generated by the MG unit 130. This battery pack 110 includes a lithium-ion battery 111, a relay 112, and a battery monitoring unit 113.

[0013] The lithium-ion battery 111 is a secondary battery configured to be chargeable and dischargeable using lithium ions for movement between electrodes. The lithium-ion battery 111 is connected to the MG unit 130 and the DCDC converter 140 via the relay 112. This lithium-ion battery 111 is rated at a voltage (e.g., 48V) required to drive the MG unit 130 that assists the operation of the vehicle.

[0014] The relay 112 is provided between the MG unit 130 and the lithium-ion battery 111 and is configured to control the electrical connection state (conductivity / interruption) between the MG unit 130 and the lithium-ion battery 111. This relay 112 switches between the conductive state and the interrupted state according to the control of the first control unit 120.

[0015] The battery monitoring unit 113 is a configuration for monitoring the state of the lithium-ion battery 111. This battery monitoring unit 113 monitors information such as the voltage, current, and temperature of the lithium-ion battery 111. Detection devices (not shown) such as sensors can be used to monitor this information. The information monitored by the battery monitoring unit 113 is acquired by the first control unit 120.

[0016] The first control unit 120 is configured to control the operation of the MG unit 130 based on the state of the lithium-ion battery 111 and the power consumption of auxiliary equipment systems (not shown). The control of the operation of the MG unit 130 from the first control unit 120 is performed by notifying the MG unit 130 from the first control unit 120 of a predetermined instruction (such as torque and power generation amount) via an in-vehicle network such as CAN (Controller Area Network). As one of the controls, the first control unit 120 of the present embodiment calculates the charging allowable power, which is the upper limit value of the charging power to the lithium-ion battery 111 where lithium precipitation does not occur, based on the state of the lithium-ion battery 111 acquired from the battery monitoring unit 113 and information related to the battery such as the usage period (elapsed time) of the lithium-ion battery 111 in the vehicle derived from the state, the charge and discharge history performed during the usage period, and the aging degradation degree (estimated capacity decrease amount), and controls the state of the relay 112 based on this charging allowable power. Further, the first control unit 120 can detect the interruption of CAN communication and recognize that no instruction is given to the MG unit 130.

[0017] This first control unit 120 is typically configured as an electronic control unit (ECU: Electronic Control Unit) including a processor such as a microcomputer, a memory, and an input / output interface. In the electronic control unit, the functions described above are realized by the processor reading and executing the program stored in the memory.

[0018] The MG unit 130 is configured to assist specific operations (such as driving force and engine start) in the vehicle and to recover the regenerative power generated during the running of the vehicle. This MG unit 130 includes a motor generator (MG) 131 and a second control unit 132.

[0019] The motor generator (MG) 131 is a device that combines the functions of an electric motor and a generator. This motor generator 131 is connected to the lithium-ion battery 111 of the battery pack 110. When functioning as an electric motor, it is driven by receiving power from the lithium-ion battery 111, and when functioning as a generator, it supplies (charges) the generated power to the lithium-ion battery 111 or an accessory system (not shown).

[0020] The second control unit 132 is a configuration (e.g., a microcomputer) for controlling the operation of the motor generator 131. This second control unit 132 can control the torque and power generation amount of the motor generator 131 according to the operation instructions notified from the first control unit 120 via CAN or the like.

[0021] The DCDC converter 140 is provided between the battery pack 110 and the MG unit 130 and an accessory system (not shown), and is a power converter for converting the input generated power of the MG unit 130 or the power stored in the battery pack 110 into a required voltage and outputting it to the accessory system. The accessory system not shown includes, for example, a lead-acid battery with a rated voltage of 12V and in-vehicle loads driven by a 12V voltage.

[0022] [Control] Next, with further reference to FIGS. 2 and 3, the control performed by the charging system 100 according to an embodiment of the present disclosure will be described. FIG. 2 is a flowchart showing the processing procedure of the first example of lithium-ion battery charging control executed by the first control unit 120 of the charging system 100. FIG. 3 is a flowchart showing the processing procedure of the second example of lithium-ion battery charging control executed by the first control unit 120 of the charging system 100.

[0023] (1) First example The charging control of the lithium-ion battery in the first example shown in FIG. 2 starts, for example, when the CAN communication between the first control unit 120 and the second control unit 132 is interrupted and the operation instruction (power generation amount) of the motor generator 131 from the first control unit 120 to the second control unit 132 is no longer notified. The MG unit 130 for which the operation instruction is no longer notified shifts to a fail-safe mode in which the motor generator 131 is driven by self-power generation.

[0024] (Step S201) The first control unit 120 calculates the allowable charging power IWin, which is the upper limit value of the charging power to the lithium-ion battery 111 where lithium precipitation does not occur. This allowable charging power IWin can be obtained, for example, by the following calculation.

[0025] First, based on the charge and discharge history of the lithium-ion battery 111, a current value Ilim at which lithium metal precipitates due to the negative electrode potential dropping to the lithium reference potential when charging continues is calculated. Next, a target current value Itag (=Ilim + ΔI) obtained by adding a margin ΔI to this current value Ilim is calculated. Then, the allowable charging power IWin (=Itag × Vbad) is obtained by multiplying this target current value Itag by the assumed worst-case value Vbad of the voltage.

[0026] When the allowable charging power IWin is calculated by the first control unit 120, the process proceeds to step S202.

[0027] (Step S202) The first control unit 120 determines whether the allowable charging power IWin is less than the first threshold value. This determination is made to determine whether the allowable charging power IWin has reached a dangerous region where lithium precipitation may occur in the lithium-ion battery 111. The first threshold value is set to a predetermined power that is lower than the maximum power at which the lithium-ion battery 111 can be charged during autonomous power generation, and the allowable charging power IWin is lower than this value. Since this first threshold value brings about a trade-off relationship between the high safety level where no lithium precipitation occurs in the lithium-ion battery 111 and the recovery efficiency of the generated power by the motor generator 131, it needs to be set appropriately. As an example, the total power consumption of an accessory system (not shown) of a vehicle operating during autonomous power generation (during fail-safe) can be set as the first threshold value.

[0028] When the first control unit 120 determines that the allowable charging power IWin is less than the first threshold value (step S202, yes), the process proceeds to step S203. On the other hand, when the first control unit 120 determines that the allowable charging power IWin is greater than or equal to the first threshold value (step S202, no), the process proceeds to step S204.

[0029] (Step S203) The first control unit 120 measures the time (continuous time t) during which the state where the allowable charging power IWin is less than the first threshold value continues. Here, when the first control unit 120 has not been measuring the continuous time t, it newly starts the measurement, and when it has already been measuring the continuous time t, it continues the measurement.

[0030] When the first control unit 120 measures the continuous time t of the state where the allowable charging power IWin is less than the first threshold value, the process proceeds to step S205.

[0031] (Step S204) The first control unit 120 clears the measured continuous time t. This process is based on the determination that the state where the allowable charging power IWin is less than the first threshold value has been interrupted and the allowable charging power IWin has exited the dangerous region of lithium precipitation.

[0032] When the continuous time t is cleared by the first control unit 120, the process proceeds to step S201.

[0033] (Step S205) The first control unit 120 determines whether the continuous time t is longer than the second threshold value. This determination is made to avoid the occurrence of lithium precipitation in the lithium-ion battery 111 due to the charge allowable power IWin. This second threshold value is a predetermined time determined based on the change trend after the charge allowable power IWin becomes less than the first threshold value and the power at which lithium metal is estimated to precipitate (lithium precipitation line). For example, the second threshold value can be determined in consideration of the control time (response time) required from when the instruction is given until the relay 112 actually performs the cutoff operation.

[0034] When the first control unit 120 determines that the continuous time t is longer than the second threshold value (step S205, yes), the process proceeds to step S206. On the other hand, when the first control unit 120 determines that the continuous time t is less than or equal to the second threshold value (step S205, no), the process proceeds to step S201.

[0035] (Step S206) The first control unit 120 controls the relay 112 to the cutoff state. By this control, the power generated by the motor generator 131 is not supplied to the lithium-ion battery 111, and the occurrence of lithium precipitation in the lithium-ion battery 111 can be avoided.

[0036] When the relay 112 is controlled to the cutoff state by the first control unit 120, this lithium-ion battery charge control ends.

[0037] In the lithium-ion battery charging control of this first example, when the lithium-ion battery 111 enters a state where lithium precipitation is a concern, instead of immediately cutting off the relay 112 when the charging allowable power IWin falls below the first threshold value, the relay 112 is cut off after waiting for the time of the second threshold value. As a result, while enhancing the efficiency of recovering the generated power of the motor generator 131, it is possible to suppress the occurrence of lithium precipitation in the lithium-ion battery 111.

[0038] (2) Second example The lithium-ion battery 111 has a physical characteristic that lithium precipitation is likely to occur rapidly as the temperature approaches extremely low temperatures. For this reason, the charging allowable power IWin also tends to have a greater sensitivity to current as the temperature decreases. The lithium-ion battery charging control of the second example is in response to this tendency.

[0039] The lithium-ion battery charging control of the second example shown in FIG. 3 is different in that a determination process according to step S301 is performed before starting the lithium-ion battery charging control (steps S201 to S206) of the first example shown in FIG. 2 above. Hereinafter, the process of this step S301 for the lithium-ion battery charging control of the second example will be described, and the description of other processes with the same step numbers as the first example will be omitted.

[0040] Note that the lithium-ion battery charging control of the second example also starts when the CAN communication between the first control unit 120 and the second control unit 132 is interrupted and the operation instruction (generated power amount) of the motor generator 131 from the first control unit 120 to the second control unit 132 is no longer notified, similar to the first example.

[0041] (Step S301) The first control unit 120 determines whether the battery temperature T, which is the temperature of the lithium-ion battery 111, is equal to or higher than a third threshold value. This determination is made to determine whether the temperature of the lithium-ion battery 111 has become low enough that lithium precipitation is likely to occur. This third threshold value is a predetermined temperature (the battery connection permission temperature during self-power generation) determined based on the physical characteristics of the lithium-ion battery 111 at low temperatures, the first threshold value used in step S202, and the second threshold value used in step S205. For example, when it is assumed that a maximum current continues to flow through the lithium-ion battery 111, the time it takes for the charging allowable power IWin to reach the lithium precipitation line after falling below the first threshold value is obtained by simulation or the like for each predetermined temperature, and the highest temperature at which the arrival of the second threshold value time is earlier than the time it takes for the charging allowable power IWin to reach the lithium precipitation line can be set as the third threshold value. In other words, the third threshold value can be set as the maximum value of the temperature that satisfies the condition that "the time of the second threshold value is longer than the time it takes for the charging allowable power IWin to reach the lithium precipitation line".

[0042] When the first control unit 120 determines that the battery temperature T is equal to or higher than the third threshold value (step S301, yes), since the temperature of the lithium-ion battery 111 is not a low temperature at which lithium precipitation is likely to occur, the process proceeds to step S201. On the other hand, when the first control unit 120 determines that the battery temperature T is lower than the third threshold value (step S301, no), since the temperature of the lithium-ion battery 111 is a low temperature at which lithium precipitation is likely to occur, the process proceeds to step S206.

[0043] In this second example of lithium-ion battery charging control, when the time it takes for the charging allowable power IWin to reach the lithium precipitation line after falling below the first threshold value is earlier than the arrival of the time of the second threshold value at which the determination is made to cut off the relay 112, the possibility of lithium precipitation occurring in the lithium-ion battery 111 becomes extremely high. Therefore, the relay 112 is cut off without performing the processes of steps S201 to S205. As a result, the occurrence of lithium precipitation in the lithium-ion battery 111 can be avoided more safely than in the first example.

[0044] <Effect> As described above, according to the charging system 100 according to an embodiment of the present disclosure, in a system configuration including a motor generator 131, a lithium-ion battery 111 capable of storing the generated power of the motor generator 131, and a relay 112 connecting the motor generator 131 and the lithium-ion battery 111, when the motor generator 131 cannot be controlled according to an instruction of the generated power based on the information of the lithium-ion battery 111, if it is estimated that there is a possibility of lithium precipitation in the lithium-ion battery 111, the relay 112 is cut off.

[0045] By this control, when the generated power of the motor generator 131 performing autonomous power generation based on fail-safe due to interruption of CAN communication or the like becomes larger than the charging allowable power IWin of the lithium-ion battery 111, it is possible to avoid that power exceeding the limit is charged to the lithium-ion battery 111 and lithium precipitation occurs.

[0046] Further, according to the charging system 100 according to the present embodiment, even when the motor generator 131 is performing autonomous power generation, if there is no possibility of lithium precipitation in the lithium-ion battery 111, the lithium-ion battery 111 is kept connected (the relay 112 is in a conductive state). By this control, in the fail-safe mode, stable power can be supplied from the MG unit 130 and the battery pack 110 to an auxiliary machine system (not shown) of the vehicle via the DCDC converter 140.

[0047] As described above, an embodiment of the technology of the present disclosure has been described. However, the present disclosure can be regarded not only as a charging system, but also as a battery charging control method executed by a control device including a processor and a memory provided in the charging system, a program of the battery charging control method, a computer-readable non-temporary recording medium storing the program, or a vehicle equipped with a charging system including the control device.

Industrial Applicability

[0048] The charging system of the present disclosure can be used when controlling the charging of a lithium-ion battery mounted on a vehicle, etc.

Explanation of Signs

[0049] 100 Charging system 110 Battery pack 111 Lithium-ion battery 112 Relay 113 Battery monitoring unit 120 First control unit 130 MG unit 131 Motor generator (MG) 132 Second control unit 140 DCDC converter

Claims

1. A charging system mounted on a vehicle, comprising: a motor generator; a lithium-ion battery that stores the electric power generated by the motor generator; a relay that electrically connects the motor generator and the lithium-ion battery; a first control unit that acquires battery information including the temperature, current, and usage period of the lithium-ion battery, and instructs the power generation amount of the motor generator based on the battery information; a second control unit that controls the operation of the motor generator according to the instruction from the first control unit; when the first control unit detects an interruption in the instruction to the second control unit, the first control unit calculates a charging allowable power, which is the upper limit value of the charging power to the lithium-ion battery where lithium precipitation does not occur, based on the battery information; a charging system that shuts off the relay if a state where the charging allowable power is less than a predetermined power continues for a predetermined time or longer.

2. The charging system according to claim 1, wherein when the first control unit detects an interruption in the instruction to the second control unit, the first control unit shuts off the relay if the temperature of the lithium-ion battery is less than a predetermined temperature.

3. The charging system according to claim 1 or 2, wherein the first control unit calculates the charging allowable power based on the temperature of the lithium-ion battery, the charge and discharge history, and the degree of aging deterioration.

4. A vehicle equipped with the charging system according to any one of claims 1 to 3.

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