Charging systems and vehicles

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 with a high state of charge (SOC: State Of Charge) or charged in an extremely low temperature state, a phenomenon (lithium precipitation) occurs in which lithium metal that leads to battery deterioration is deposited. Therefore, various techniques for suppressing the occurrence of lithium precipitation have been proposed for lithium-ion batteries.

[0003] Patent Document 1 discloses a system that charges a lithium-ion battery with the generated power of 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 the motor generator so that the power input from the motor generator to the lithium-ion battery (charging power) is below an input limit power value that can suppress the occurrence of lithium precipitation.

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 Patent Document 1 above, if the electronic control unit that controls the motor generator is unable to receive the operation command transmitted from the electronic control unit that monitors the state of the lithium-ion battery due to reasons such as a communication interruption, the motor generator will not be able to properly control the power generation based on the input limit power value. As a result, the motor generator may generate excessive power, which may cause lithium deposition in the lithium-ion battery.

[0006] This disclosure has been made in view of the above-mentioned problems, and aims to provide a charging system, etc., that can suppress the occurrence of lithium deposition in a lithium-ion battery when the power generation of a motor generator becomes unable to be properly controlled. [Means for solving the problem]

[0007] To solve the above problems, one aspect of the disclosed technology is a charging system mounted on a vehicle, comprising: a motor generator; a lithium-ion battery for storing the power generated by the motor generator; a relay for electrically connecting the motor generator and the lithium-ion battery; a first control unit for acquiring battery information including the temperature, current, and usage period of the lithium-ion battery and instructing the amount of power generated by the motor generator based on the battery information; and a second control unit for controlling the operation of the motor generator according to the instructions from the first control unit, wherein the first control unit, upon detecting an interruption in instructions to the second control unit, calculates the allowable charging power, which is the upper limit of the charging power to the lithium-ion battery that does not cause lithium deposition, based on the battery information, and shuts off the relay if the allowable charging power remains below a predetermined power for a predetermined time or longer. [Effects of the Invention]

[0008] According to the charging system described above, if the instruction to the motor generator is interrupted and power generation cannot be properly controlled, the relay is shut off in anticipation of a condition in which lithium deposition is likely to occur in the lithium-ion battery. This makes it possible to suppress the occurrence of lithium deposition in the lithium-ion battery. [Brief explanation of the drawing]

[0009] [Figure 1] Schematic diagram of a charging system according to one embodiment of the present disclosure. [Figure 2] Flowchart of the first example of battery charging control performed by a charging system [Figure 3] Process flowchart for the second example of battery charging control performed by the charging system [Modes for carrying out the invention]

[0010] The charging system of this disclosure electrically disconnects the charging path from the motor generator to the lithium-ion battery if the motor generator that charges the lithium-ion battery loses power generation control and there is a possibility of lithium deposition in the lithium-ion battery. As a result, the power generated by the motor generator is not supplied to the lithium-ion battery 111, and the phenomenon in which lithium metal is deposited in the lithium-ion battery 111 beyond its limit can be avoided. The embodiments of this disclosure will be described in detail below with reference to the drawings.

[0011] <Embodiment> [composition] Figure 1 is a block diagram showing a schematic configuration example of a charging system 100 according to one embodiment of the present disclosure. In Figure 1, the charging system 100 includes a battery pack 110, a first control unit 120, an MG unit 130, and a DC-DC converter 140. In Figure 1, power lines through which power is exchanged are shown as solid lines, and signal lines through which detected values ​​or instructions are shown as dashed lines. This charging system 100 is installed in vehicles such as hybrid electric vehicles (HEVs) that have 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 the vehicle's auxiliary equipment system (not shown), and can also store the power generated by the MG unit 130. This battery pack 110 comprises a lithium-ion battery 111, a relay 112, and a battery monitoring unit 113.

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

[0014] Relay 112 is installed between the MG unit 130 and the lithium-ion battery 111 and is configured to control the electrical connection state (continuity / disconnection) between the MG unit 130 and the lithium-ion battery 111. This relay 112 switches between a conduction state and a disconnection state according to the control of the first control unit 120.

[0015] The battery monitoring unit 113 is configured to monitor 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 such as sensors (not shown) 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 the auxiliary equipment system (not shown). The operation control of the MG unit 130 from the first control unit 120 is performed by notifying the MG unit 130 of predetermined instructions (torque, power generation amount, etc.) from the first control unit 120 via an in-vehicle network such as CAN (Controller Area Network). As one of the control functions of the first control unit 120 in this embodiment, it calculates the charge-permitted power, which is the upper limit of the charging power to the lithium-ion battery 111 that does not cause lithium deposition, based on the state of the lithium-ion battery 111 obtained from the battery monitoring unit 113, and battery-related information such as the usage period (elapsed time) of the lithium-ion battery 111 in the vehicle, the charge and discharge history performed during the usage period, and the degree of aging degradation (estimated capacity reduction), and controls the state of the relay 112 based on this charge-permitted power. Furthermore, the first control unit 120 can detect an interruption in CAN communication and understand that no instructions are being sent to the MG unit 130.

[0017] This first control unit 120 is typically configured as an electronic control unit (ECU) that includes a processor such as a microcontroller, memory, and an input / output interface. In the electronic control unit, the above-mentioned functions are realized by the processor reading and executing a program stored in memory.

[0018] The MG unit 130 is configured to assist in specific operations in the vehicle (such as driving force and engine starting) and to recover regenerative power generated during vehicle operation. This MG unit 130 comprises 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 auxiliary machine 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 auxiliary machine 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 auxiliary machine system. The auxiliary machine 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, referring further 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 lithium-ion battery charging control in the first example shown in Figure 2 is initiated, for example, when CAN communication between the first control unit 120 and the second control unit 132 is interrupted, and the first control unit 120 no longer notifies the second control unit 132 of the operation instruction (amount of power generated) for the motor generator 131. The MG unit 130, which no longer receives operation instructions, switches to a fail-safe mode in which the motor generator 131 is driven by autonomous power generation.

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

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

[0026] Once the first control unit 120 calculates the allowable charging power IWin, the process proceeds to step S202.

[0027] (Step S202) The first control unit 120 determines whether the charge-tolerance power IWin is below a first threshold. This determination is made to determine whether the charge-tolerance power IWin has reached a dangerous level that could cause lithium deposition in the lithium-ion battery 111. The first threshold is set to a predetermined power level below the maximum power that the lithium-ion battery 111 can be charged during autonomous power generation. This first threshold needs to be set appropriately because it creates a trade-off between the level of safety required to prevent lithium deposition in the lithium-ion battery 111 and the efficiency of power recovery by the motor generator 131. As an example, the sum of the power consumption of the vehicle's auxiliary systems (not shown) operating during autonomous power generation (fail-safe mode) can be set as the first threshold.

[0028] If the first control unit 120 determines that the charge-tolerance power IWin is less than the first threshold (step S202, yes), the process proceeds to step S203. On the other hand, if the first control unit 120 determines that the charge-tolerance power IWin is equal to or greater than the first threshold (step S202, no), the process proceeds to step S204.

[0029] (Step S203) The first control unit 120 measures the duration (duration t) during which the charge allowable power IWin remains below the first threshold. If the first control unit 120 has not yet measured the duration t, it starts measuring again; if it has already measured the duration t, it continues measuring.

[0030] When the first control unit 120 measures the duration t of the state in which the charge-permissible power IWin is less than the first threshold, the process proceeds to step S205.

[0031] (Step S204) The first control unit 120 clears the measured duration t. This process is based on the judgment that the state in which the charge-tolerance power IWin is below the first threshold has ended, and the charge-tolerance power IWin has moved out of the lithium deposition risk area.

[0032] When the duration 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 duration t is longer than the second threshold. This determination is made to avoid lithium deposition in the lithium-ion battery 111 due to the charge-permissible power IWin. This second threshold is a predetermined time determined based on the relationship between the trend of change in the charge-permissible power IWin after it falls below the first threshold and the power at which lithium metal deposition is estimated to occur (lithium deposition line). For example, the second threshold can be determined by considering the control time (response time) required from the time an instruction is given until the relay 112 actually trips.

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

[0035] (Step S206) The first control unit 120 controls the relay 112 to an off state. This control prevents the power generated by the motor generator 131 from being supplied to the lithium-ion battery 111, thereby preventing lithium deposition from occurring in the lithium-ion battery 111.

[0036] When the first control unit 120 controls the relay 112 to the off state, this lithium-ion battery charging control ends.

[0037] In this first example of lithium-ion battery charging control, if the lithium-ion battery 111 reaches a state where lithium deposition is a concern, the relay 112 is not immediately shut off when the allowable charging power IWin falls below the first threshold, but rather waits for the time of the second threshold before shutting off the relay 112. This makes it possible to improve the efficiency of recovering the power generated by the motor generator 131 while suppressing the occurrence of lithium deposition in the lithium-ion battery 111.

[0038] (2) Second example The lithium-ion battery 111 has a physical characteristic in which lithium deposition tends to occur more rapidly as the temperature approaches the cryogenic temperature. Therefore, the charge-permissible power IWin also tends to become more sensitive to current as the temperature decreases. The lithium-ion battery charge control in the second example addresses this tendency.

[0039] The second example of lithium-ion battery charging control shown in Figure 3 differs from the first example of lithium-ion battery charging control shown in Figure 2 in that it performs a decision process in step S301 before starting the lithium-ion battery charging control (steps S201 to S206). Below, the process of step S301 in the second example of lithium-ion battery charging control will be explained, and explanations of other processes that have the same step number as the first example will be omitted.

[0040] In addition, the lithium-ion battery charging control in the second example is also initiated in the same way as in the first example when CAN communication between the first control unit 120 and the second control unit 132 is interrupted, and the first control unit 120 no longer notifies the second control unit 132 of the operation instruction (amount of power generated) for the motor generator 131.

[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 above a third threshold. This determination is made to determine whether the temperature of the lithium-ion battery 111 has become low enough for lithium deposition to occur easily. This third threshold is a predetermined temperature (battery connection permission temperature during autonomous power generation) determined based on the physical characteristics of the lithium-ion battery 111 at low temperatures and the first threshold used in step S202 and the second threshold used in step S205. For example, assuming that the maximum current continues to flow through the lithium-ion battery 111, the time from when the charge-permissible power IWin falls below the first threshold to when it reaches the lithium deposition line can be determined by simulation for each predetermined temperature, and the highest temperature at which the time of the second threshold arrives earlier than the time it takes for the charge-permissible power IWin to reach the lithium deposition line can be set as the third threshold. In other words, the third threshold can be the maximum temperature that satisfies the condition that "the time of the second threshold is longer than the time it takes for the charge-permissible power IWin to reach the lithium deposition line."

[0042] If the first control unit 120 determines that the battery temperature T is above the third threshold (step S301, yes), the process proceeds to step S201 because the temperature of the lithium-ion battery 111 is not low enough for lithium deposition to occur. On the other hand, if the first control unit 120 determines that the battery temperature T is below the third threshold (step S301, no), the process proceeds to step S206 because the temperature of the lithium-ion battery 111 is low enough for lithium deposition to occur.

[0043] In this second example of lithium-ion battery charging control, if the time from when the allowable charging power IWin falls below the first threshold to when it reaches the lithium deposition line is earlier than the time of the second threshold that triggers the decision to shut off relay 112, the possibility of lithium deposition occurring in the lithium-ion battery 111 becomes extremely high, and therefore relay 112 is shut off without performing the processes described in steps S201 to S205 above. This makes it possible to avoid lithium deposition in the lithium-ion battery 111 even more safely than in the first example.

[0044] <Effects and Actions> As described above, according to the charging system 100 according to one embodiment of the present disclosure, in a system configuration comprising a motor generator 131, a lithium-ion battery 111 capable of storing the power generated by the motor generator 131, and a relay 112 connecting the motor generator 131 and the lithium-ion battery 111, if the motor generator 131 becomes uncontrollable due to an instruction on the amount of power generated based on information from the lithium-ion battery 111, the relay 112 is shut off if it is estimated that there is a possibility of lithium deposition in the lithium-ion battery 111.

[0045] This control prevents lithium deposition from occurring when the power generated by the motor generator 131, which performs autonomous power generation based on fail-safe principles due to interruptions in CAN communication or other reasons, exceeds the charging capacity IWin of the lithium-ion battery 111, thereby preventing the lithium-ion battery 111 from being charged with power exceeding the limit.

[0046] Furthermore, according to the charging system 100 of this embodiment, even when the motor generator 131 is performing autonomous power generation, if there is no possibility of lithium deposition in the lithium-ion battery 111, the lithium-ion battery 111 is kept connected (the relay 112 is in a conductive state). This control enables a stable supply of power from the MG unit 130 and the battery pack 110 to the vehicle's auxiliary equipment system (not shown) via the DCDC converter 140 in fail-safe mode.

[0047] Although one embodiment of the disclosed technology has been described above, the disclosure can be understood not only as a charging system, but also as a battery charging control method executed by a control device equipped with a processor and memory in the charging system, a program for 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 described herein can be used, for example, to control the charging of a lithium-ion battery installed in a vehicle. [Explanation of Symbols]

[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 DC-DC converters

Claims

1. A charging system installed in a vehicle, Motor generator and, A lithium-ion battery that stores the electricity generated by the motor generator, A relay that electrically connects the motor generator and the lithium-ion battery, A first control unit acquires battery information including the temperature, current, and usage period of the lithium-ion battery, and instructs the amount of power generated by the motor generator based on the battery information. The system comprises a second control unit that controls the operation of the motor generator in accordance with the instructions from the first control unit, When the first control unit detects an interruption in the instruction to the second control unit, The maximum charge power, which is the upper limit of the charging power to the lithium-ion battery in which lithium deposition does not occur, is calculated based on the battery information. A charging system that shuts off the relay if the charge-permissible power remains below a predetermined power for a predetermined period of time or longer.

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

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

4. A vehicle equipped with the charging system according to claim 1 or 2.

5. A vehicle equipped with the charging system described in Claim 3.

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