Charging system and vehicle

Abstract

The invention relates to a charging system and a vehicle. The charging system includes: a motor generator; a lithium ion battery for storing the electric power generated by the motor generator; the relay is used for electrically connecting the motor generator with the lithium ion battery; a first processor that acquires battery information and instructs the amount of power generated by the motor generator on the basis of the battery information; and a second processor that controls the operation of the motor generator in accordance with the instruction, and when an interruption of the instruction to the second processor is detected, the first processor calculates, on the basis of the battery information, an allowable charging power, which is the upper limit value of the charging power to the lithium ion battery at which lithium deposition does not occur. When the state in which the charging allowable power is less than the predetermined power continues for a predetermined time or longer, the relay is turned off.

Description

Technical Field

[0001] The present disclosure relates to a charging system and the like that controls charging of a lithium-ion battery mounted on a vehicle. Background Art

[0002] If a lithium-ion battery is further charged at a high state of charge (SOC) or at an extremely low temperature, lithium metal will precipitate (lithium precipitation) which causes battery deterioration. Therefore, various technologies have been proposed for lithium-ion batteries to suppress the occurrence of lithium precipitation.

[0003] International Publication No. 2010 / 005079 discloses a system for charging a lithium-ion battery with electric power generated by an electric generator in a hybrid vehicle. In the system described in International Publication No. 2010 / 005079, an instruction is given from an electronic control unit that monitors the state of the lithium-ion battery to an electronic control unit that controls the electric generator to operate in such a manner that the electric power (charging power) input from the electric generator to the lithium-ion battery is below an input limit power value that can suppress the generation of lithium precipitation.

[0004] In the system described in International Publication No. 2010 / 005079, for example, when the electronic control unit controlling the electric generator cannot receive the instruction of the action sent from the electronic control unit monitoring the state of the lithium-ion battery due to reasons such as communication interruption, it becomes impossible to properly control the power generation of the electric generator based on the input limit power value. Therefore, there is a concern that the electric generator generates excessive power and the lithium-ion battery produces lithium precipitation. Summary of the invention

[0005] The present disclosure provides a charging system and the like that can suppress the occurrence of lithium deposition in a lithium-ion battery when the power generation of a motor generator cannot be appropriately controlled.

[0006] One mode of the disclosed technology provides a charging system mounted on a vehicle. The charging system comprises: an electric generator; a lithium-ion battery configured to store the electric power generated by the electric generator; a relay configured to electrically connect the electric generator to the lithium-ion battery; a first processor configured to obtain battery information including the temperature, current, and usage period of the lithium-ion battery, and to indicate the amount of power generated by the electric generator based on the battery information; and a second processor configured to control the operation of the electric generator according to the instruction from the first processor. The first processor is configured to calculate the upper limit value of the charging power to the lithium-ion battery that does not cause lithium precipitation, that is, the charging allowable power, based on the battery information when an interruption of the instruction to the second processor is detected, and to cut off the relay if the state in which the charging allowable power is less than the specified power continues for more than a specified time.

[0007] According to the charging system disclosed above, when the instruction to the motor generator is interrupted and power generation cannot be properly controlled, the relay is disconnected when the lithium ion battery is predicted to be in a state where lithium deposition will occur. Thus, the occurrence of lithium deposition in the lithium ion battery can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Hereinafter, features, advantages, technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals represent like components, wherein:

[0009] Figure 1 This is a schematic configuration diagram of a charging system according to one embodiment of the present disclosure.

[0010] Figure 2 This is a processing flowchart of a first example of battery charging control executed by the charging system.

[0011] Figure 3 This is a processing flowchart of the second example of battery charging control executed by the charging system. DETAILED DESCRIPTION

[0012] In the charging system of the present disclosure, when the electric generator charging the lithium-ion battery becomes unable to control power generation, if there is a possibility of lithium precipitation in the lithium-ion battery, the charging path from the electric generator to the lithium-ion battery is electrically disconnected. As a result, the electric power generated by the electric generator is no longer supplied to the lithium-ion battery 111, which can avoid the phenomenon of lithium metal precipitation caused by the lithium-ion battery 111 exceeding the limit.

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0014] <Implementation Method>

[0015] [constitute]

[0016] Figure 1 1 is a block diagram showing a schematic configuration example of a charging system 100 according to an embodiment of the present disclosure. Figure 1 In the embodiment, the charging system 100 includes a battery pack 110, a first control unit 120, an MG unit 130, and a DCDC converter 140. Figure 1 In FIG. 1 , a power line for transferring power is indicated by a solid line, and a signal line for passing a detection value, an indication, etc. is indicated by a dotted line. 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.

[0017] The battery pack 110 is a power source capable of supplying power to the MG unit 130 and auxiliary systems of the vehicle (not shown), or storing power generated by the MG unit 130. The battery pack 110 includes a lithium-ion battery 111, a relay 112, and a battery monitoring unit 113.

[0018] The lithium ion battery 111 is a secondary battery that uses lithium ions for transfer between electrodes and is chargeable and dischargeable. The lithium ion battery 111 is connected to the MG unit 130 and the DCDC converter 140 via the relay 112. The lithium ion battery 111 is rated at a voltage (e.g., 48V) required for driving the MG unit 130 to assist in the operation of the vehicle.

[0019] The relay 112 is provided between the MG unit 130 and the lithium ion battery 111 and is used to control the electrical connection state (on / off) between the MG unit 130 and the lithium ion battery 111. The relay 112 switches between the on state and the off state according to the control of the first control unit 120.

[0020] The battery monitoring unit 113 is a structure for monitoring the state of the lithium-ion battery 111. The battery monitoring unit 113 monitors information such as the voltage, current, and temperature of the lithium-ion battery 111. The monitoring of this information can use a detection device such as a sensor (not shown). The information monitored by the battery monitoring unit 113 is obtained by the first control unit 120.

[0021] The first control unit 120 is a structure for controlling the operation of the MG unit 130 based on the state of the lithium-ion battery 111 and the power consumption of the auxiliary system (not shown). The control of the operation of the MG unit 130 by the first control unit 120 is performed, for example, by notifying the MG unit 130 of a predetermined instruction (torque, power generation, etc.) from the first control unit 120 to the MG unit 130 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 performs the following control: based on the state of the lithium-ion battery 111 obtained from the battery monitoring unit 113, the use period (elapsed time) of the lithium-ion battery 111 in the vehicle derived from the state, the history of charge and discharge performed during use, the aging degradation degree (estimated capacity reduction) and other information related to the battery, the upper limit value of the charging power to the lithium-ion battery 111 without causing lithium deposition, that is, the charging allowable power, is calculated, and the state of the relay 112 is controlled based on the charging allowable power. In addition, the first control unit 120 can detect the interruption of the CAN communication and grasp the fact that the instruction cannot be given to the MG unit 130.

[0022] The first control unit 120 is typically configured as an electronic control unit (ECU) including a processor, a memory, and an input / output interface such as a microcomputer. In the electronic control unit, the processor reads out a program stored in the memory and executes it to realize the above-mentioned functions.

[0023] The MG unit 130 is a configuration for assisting a specific operation (driving force, engine start, etc.) in the vehicle or recovering regenerative power generated while the vehicle is running. The MG unit 130 includes a motor generator (MG) 131 and a second control unit 132 .

[0024] The motor generator (MG) 131 is a device having both the functions of a motor and a generator. The motor generator 131 is connected to the lithium-ion battery 111 of the battery pack 110, and receives power from the lithium-ion battery 111 to drive the motor when it functions as a motor, and supplies (charges) the generated power to the lithium-ion battery 111 and an auxiliary system (not shown) when it functions as a generator.

[0025] The second control unit 132 is a component (eg, a microcomputer) for controlling the operation of the motor generator 131. The second control unit 132 can control the torque and power generation amount of the motor generator 131 according to the operation instruction notified from the first control unit 120 via CAN or the like.

[0026] The DCDC converter 140 is a power converter provided between the battery pack 110 and the MG unit 130 and an auxiliary system (not shown) for converting the power generated by the MG unit 130 and the power stored in the battery pack 110 to a required voltage and outputting it to the auxiliary system. The auxiliary system (not shown) includes, for example, a lead storage battery with a rated voltage of 12V and a vehicle-mounted load driven by a voltage of 12V.

[0027] [control]

[0028] Next, refer to Figure 2 as well as Figure 3 Next, control performed by the charging system 100 according to one embodiment of the present disclosure will be described. Figure 2 1 is a flowchart showing a processing procedure of a first example of lithium-ion battery charging control executed by the first control unit 120 of the charging system 100 . Figure 3 1 is a flowchart showing a processing procedure of a second example of lithium-ion battery charging control executed by the first control unit 120 of the charging system 100 .

[0029] (1)Example 1

[0030] For example, if 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 to the second control unit 132 is not notified from the first control unit 120, the operation starts. Figure 2 The MG unit 130 that is no longer notified of the operation instruction shifts to a fail-safe mode in which the motor generator 131 is driven by self-generated power.

[0031] (Step S201)

[0032] The first control unit 120 calculates the charge-allowed power IWin which is the upper limit value of the charge power to the lithium-ion battery 111 at which lithium deposition does not occur. The charge-allowed power IWin can be obtained by, for example, the following calculation.

[0033] First, the current value Ilim at which lithium metal is deposited due to the negative electrode potential dropping to the lithium reference potential when charging continues is calculated based on the charge and discharge history of the lithium-ion battery 111. Next, the target current value Itag (= Ilim + ΔI) obtained by adding a margin (margin) ΔI to the current value Ilim is calculated. Furthermore, the charging allowable power IWin (= Itag × Vbad) is obtained by multiplying the assumed worst value Vbad of the voltage by the target current value Itag.

[0034] When the charge-allowed electric power IWin is calculated by the first control unit 120 , the process proceeds to step S202 .

[0035] (Step S202)

[0036] The first control unit 120 determines whether the charge-allowed power IWin is less than the first threshold value. This determination is made to determine whether the charge-allowed power IWin has reached a dangerous area where lithium precipitation is likely to occur in the lithium-ion battery 111. The first threshold value is set to a prescribed power at which the charge-allowed power IWin is lower than the maximum power that can be charged to the lithium-ion battery 111 in autonomous power generation. In order to have a trade-off relationship between the height of safety of the lithium-ion battery 111 not causing lithium precipitation and the recovery efficiency of the generated power by the electric generator 131, the first threshold value needs to be appropriately set. As an example, the sum of the power consumption of the auxiliary system (not shown) of the vehicle operating in autonomous power generation (fault protection) can be set as the first threshold value.

[0037] When the first control unit 120 determines that the charge-allowed 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 charge-allowed power IWin is greater than the first threshold value (step S202, no), the process proceeds to step S204.

[0038] (Step S203)

[0039] The first control unit 120 counts the time (duration time t) during which the state in which the charge-allowed power IWin is less than the first threshold value continues. If the duration time t has not been counted, the first control unit 120 newly starts counting, and if the duration time t has already been counted, continues the counting.

[0040] When the first control unit 120 measures the duration t of the state in which the charge-allowed electric power IWin is less than the first threshold, the process proceeds to step S205 .

[0041] (Step S204)

[0042] The first control unit 120 clears the measured duration t. This process is based on the determination that the state in which the charge-allowed power IWin is less than the first threshold value is interrupted and the charge-allowed power IWin is out of the dangerous region of lithium deposition.

[0043] When the duration t is cleared by the first control unit 120 , the process proceeds to step S201 .

[0044] (Step S205)

[0045] The first control unit 120 determines whether the duration t is longer than the second threshold value. This determination is made to avoid the generation of lithium precipitation of the lithium-ion battery 111 caused by the charge-allowed power IWin. The second threshold value is a predetermined time determined based on the relationship between the change trend from when the charge-allowed power IWin becomes less than the first threshold value and the power (lithium precipitation line) inferred to be lithium metal precipitation. For example, the second threshold value can be determined by considering the control time (response time) required from the time the instruction is given to the time when the relay 112 actually performs the cut-off action.

[0046] When 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, when the first control unit 120 determines that the duration t is less than the second threshold (step S205, no), the process proceeds to step S201.

[0047] (Step S206)

[0048] The first control unit 120 controls the relay 112 to be in the disconnected state. This control prevents the electric 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.

[0049] When the relay 112 is controlled by the first control unit 120 to be in the disconnected state, the present lithium-ion battery charging control ends.

[0050] In the lithium-ion battery charging control of the first example, when the lithium-ion battery 111 is in a state where lithium deposition is concerned, the relay 112 is not immediately disconnected when the charge-allowed power IWin is lower than the first threshold, but the relay 112 is disconnected after waiting for a time period of the second threshold. Thus, the lithium deposition in the lithium-ion battery 111 can be suppressed while improving the efficiency of recovering the generated power of the electric generator 131.

[0051] (2) Case 2

[0052] The lithium ion battery 111 has a physical property that lithium deposition occurs more rapidly as the temperature approaches extremely low temperature. Therefore, there is a tendency that the charge-allowed power IWin also becomes more sensitive to current as the temperature becomes lower. The lithium ion battery charging control of the second example corresponds to this tendency.

[0053] Figure 3 The lithium-ion battery charging control of the second example shown is different in that at the beginning of the above Figure 2 Prior to the lithium ion battery charging control (steps S201 to S206) of the first example shown, the determination process of step S301 is performed. The following describes the process of step S301 for the lithium ion battery charging control of the second example, and the description of other processes with the same step numbers as those of the first example is omitted.

[0054] In addition, similar to the first example, if 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 electric generator 131 to the second control unit 132 is no longer notified from the first control unit 120, the lithium-ion battery charging control of the second example is started.

[0055] (Step S301)

[0056] The first control unit 120 determines whether the temperature of the lithium-ion battery 111, that is, the battery temperature T, is above the third threshold value. This judgment is made to determine whether lithium deposition is easier to occur, the lower the temperature of the lithium-ion battery 111. The third threshold value is a predetermined temperature (battery connection allowable temperature in autonomous power generation) determined based on the physical properties of the lithium-ion battery 111 at low temperature, the first threshold value used in the above step S202, and the second threshold value used in the above step S205. For example, assuming that the maximum current continues to flow to the lithium-ion battery 111, the time from the charging allowable power IWin being lower than the first threshold value to the time when the lithium deposition line is reached is obtained by simulation, etc. at each predetermined temperature, and the highest temperature that can arrive at the second threshold value earlier than the time when the charging allowable power IWin reaches the lithium deposition line is set as the third threshold value. In other words, the third threshold value can be the maximum value of the temperature that satisfies the condition that "the time of the second threshold value is longer than the time when the charging allowable power IWin reaches the lithium deposition line".

[0057] When the first control unit 120 determines that the battery temperature T is above 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 less 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.

[0058] In the lithium ion battery charging control of the second example, when the time from when the charging allowable power IWin is lower than the first threshold to when the lithium precipitation line is reached is earlier than the time of the second threshold for judging the cut-off relay 112, since the possibility of lithium precipitation in the lithium ion battery 111 is very high, the relay 112 is cut off without performing the processing of the above steps S201 to S205. Thus, the generation of lithium precipitation in the lithium ion battery 111 can be avoided more safely than in the above first example.

[0059] <Function / Effect>

[0060] As described above, according to the charging system 100 involved in one embodiment of the present disclosure, in a system configuration including an electric generator 131, a lithium-ion battery 111 capable of storing the power generated by the electric generator 131, and a relay 112 connecting the electric generator 131 and the lithium-ion battery 111, when the electric generator 131 becomes unable to be controlled according to an indication of the power generation amount based on information of the lithium-ion battery 111, if it is inferred that there is a possibility of lithium deposition in the lithium-ion battery 111, the relay 112 is disconnected.

[0061] This control can prevent the lithium ion battery 111 from being charged with power exceeding the limit and causing lithium deposition when the power generated by the electric generator 131 that performs autonomous power generation based on fault protection becomes greater than the charge allowable power IWin of the lithium ion battery 111 due to interruption of CAN communication or the like.

[0062] In addition, according to the charging system 100 of the present embodiment, even when the electric generator 131 generates power autonomously, if there is a possibility of lithium deposition in the lithium-ion battery 111, the state of connecting the lithium-ion battery 111 is maintained (the relay 112 is turned on). By this control, in the fail-safe mode, a stable power supply can be provided from the MG unit 130 and the battery pack 110 to the auxiliary system (not shown) of the vehicle via the DCDC converter 140.

[0063] An embodiment of the technology disclosed herein has been described above, but the present disclosure can be understood not only as a charging system, but also as a battery charging control method executed by a control device having a processor and a memory possessed by a 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 a control device, etc.

[0064] The charging system of the present disclosure can be used, for example, when controlling the charging of a lithium-ion battery mounted on a vehicle.

Claims

1. A charging system, mounted on a vehicle, characterized in that: include: Motor generator; a lithium-ion battery configured to store the electric power generated by the motor generator; a relay configured to electrically connect the motor generator to the lithium-ion battery; a first processor configured to obtain battery information including a temperature, a current, and a usage period of the lithium-ion battery, and to instruct an amount of power generated by the motor generator based on the battery information; as well as a second processor configured to control the operation of the motor generator according to the instruction from the first processor, in, The first processor is configured to calculate the upper limit value of the charging power to the lithium ion battery that does not cause lithium deposition, that is, the charging allowable power, based on the battery information, when the interruption of the instruction to the second processor is detected. If the state in which the charge-permitted electric power is less than the predetermined electric power continues for a predetermined time or longer, the relay is turned off.

2. The charging system according to claim 1, characterized in that: The first processor is configured to, when detecting an interruption of the instruction to the second processor, disconnect the relay if the temperature of the lithium-ion battery is lower than a predetermined temperature.

3. The charging system according to claim 1 or 2, characterized in that: The first processor is configured to calculate the charge-allowable power based on the temperature of the lithium-ion battery, the charge and discharge history, and the degree of aging degradation.

4. A vehicle, characterized in that: The charging system according to any one of claims 1 to 3 is mounted.

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