Vehicle power supply system

Abstract

This vehicle power supply system comprises: an auxiliary battery provided as a power supply for auxiliary equipment in a vehicle; a relay inserted between the auxiliary battery and the auxiliary equipment; and a control unit that performs cut-off control due to capacity reduction, in which the relay is controlled to be turned off in accordance with a decrease in the remaining amount of the auxiliary battery to cut off the power supply from the auxiliary battery to the auxiliary equipment. The vehicle power supply system further comprises a switch unit capable of switching between an ON state and an OFF state. When the control unit detects that the switch unit is turned on in a state in which the relay is turned off, the control unit performs control to turn on the relay.

Description

Vehicle Power Supply Systems

[0001] The present invention relates to the technical field of a vehicle power supply system equipped with a battery for supplying power to auxiliary machinery in a vehicle.

[0002] The use of lithium ion batteries as a substitute for 12V auxiliary lead batteries is being considered.

[0003] As a related prior art, the following Patent Document 1 can be cited: Patent Document 1 discloses a technology for improving vehicle safety by ensuring power supply in emergencies such as vehicle crashes.

[0004] Japanese Patent Application Laid-Open No. 2022-167433

[0005] When a lithium-ion battery is used as an auxiliary battery, its behavior when the battery dies differs from that of a lead battery. A lithium-ion battery is equipped with a control circuit called a Battery Management System (BMS) to protect the battery cells. When the battery cells are not charged for some reason and the SOC (State of Charge) representing the remaining battery capacity drops, a relay function (called a System Main Relay (SMR)) is implemented to shut off power automatically to prevent the battery from becoming irreversibly unusable.

[0006] However, the SMR function causes a loss of power to auxiliary equipment, including various on-board ECUs (Electric Control Units), making it impossible to restart the vehicle even if repairs or recharging are required. Since the auxiliary equipment loses power at this time, the diagnostic equipment also becomes unusable.

[0007] Therefore, when attempting to recharge and reuse a lithium-ion battery, it is necessary to connect a separate power source to the vehicle to enable power supply to the diagnostic device and send a restart command to the BMS, or if there is no separate power source near the vehicle, to remove the lithium-ion battery and send a restart command to the BMS in an environment where power can be supplied, or to replace the lithium-ion battery with a new one, etc., which complicates the work and leads to increased repair costs.

[0008] The present invention has been made in consideration of the above circumstances, and aims to prevent the complicated response work when the battery dies, even when a lithium-ion battery is installed as an auxiliary battery, and to prevent the ease of maintenance from being reduced compared to when a conventional lead battery is used.

[0009] One embodiment of the vehicle power supply system of the present invention comprises an auxiliary battery provided as a power source for auxiliary equipment in a vehicle, a relay inserted between the auxiliary battery and the auxiliary equipment, and a control unit that controls the relay to turn off in response to a decrease in the remaining charge of the auxiliary battery and performs low-capacity cut-off control to cut off power supply from the auxiliary battery to the auxiliary equipment, and also comprises a switch unit that can be switched between an on state and an off state, and the control unit controls the relay to turn on when it detects that the switch unit has been turned on while the relay is off.

[0010] According to the present invention, even when a lithium-ion battery is installed as an auxiliary battery, it is possible to prevent the response work when the battery dies from becoming complicated, and to prevent the ease of maintenance from decreasing compared to when a conventional lead battery is used.

[0011] It is a diagram showing a schematic internal configuration example of a vehicle equipped with a vehicle power supply system as an embodiment. It is a diagram for explaining the configuration example of the vehicle power supply system. It is a flowchart of processing of a control unit provided in the vehicle power supply system. It is a diagram showing another configuration example of a switch unit.

[0012] An embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a diagram showing an example of a schematic internal configuration of a vehicle equipped with a vehicle power supply system 1 according to an embodiment. Note that Fig. 1 shows only the components according to the present invention among the various components of the vehicle according to the embodiment.

[0013] The vehicle of this embodiment is configured as a hybrid electric vehicle (HEV) equipped with an engine 2 and a motor generator (MG) 4, and is also equipped with a high-voltage battery 5 (driving battery) for providing drive power for the MG 4. In a vehicle that is an HEV, the engine 2 may be used as a drive source for the wheels, or as a power source for generating power to drive the MG 4 and to charge the high-voltage battery 5.

[0014] In this example, a four-wheeled vehicle is assumed as the vehicle, but the vehicle of the embodiment may be any vehicle having at least two or more wheels.

[0015] The vehicle is provided with an inverter 6 for the MG 4. When the MG 4 is powered, the inverter 6 outputs a drive voltage generated based on the input voltage from the high-voltage battery 5 to the MG 4, and when regenerating power, the inverter 6 charges the high-voltage battery 5 using the regenerated power from the MG 4.

[0016] The vehicle also includes auxiliary equipment 3. The auxiliary equipment 3 broadly includes various electronic components, such as a fuel injector and an electronic throttle, for operating the engine 2, various ECUs (Electric Control Units) for controlling various vehicle operations, such as controlling the engine 2 and MG4, and on-board electronic devices, such as meters, navigation equipment, and audio equipment.

[0017] The vehicle power supply system 1 is configured to include an auxiliary battery unit 10 for supplying power to the auxiliary devices 3. The auxiliary battery unit 10 has an auxiliary battery 11 provided as a power source for the auxiliary devices 3. In this example, the rated output voltage of the auxiliary battery 11 is 12 V. However, the rated output voltage of the auxiliary battery 11 is not limited to 12 V and may be, for example, 24 V. The rated output voltage of the auxiliary battery 11 is lower than the rated output voltage of the high-voltage battery 5 (for example, 400 V).

[0018] In the vehicle power supply system 1 of the embodiment, a lithium-ion battery, rather than a lead battery, is used as the auxiliary battery 11. A lithium-ion battery can be made smaller and lighter in terms of battery weight and size compared to a lead battery, and has advantages in terms of reducing vehicle weight and installation space.

[0019] In the vehicle of the embodiment, the auxiliary battery 11 can be charged by the high-voltage battery 5. When the auxiliary battery 11 is charged by the high-voltage battery 5, a DC / DC converter 7 is used. The DC / DC converter 7 has a step-down function, and steps down the input voltage from the high-voltage battery 5 (to 12 V in this example) and outputs the stepped-down voltage to the auxiliary battery unit 10, thereby charging the auxiliary battery 11.

[0020] Fig. 2 is a diagram for explaining an example configuration of the vehicle power supply system 1. In Fig. 2, the auxiliary machinery 3, the high-voltage battery 5, and the DC / DC converter 7 shown in Fig. 1 are also shown together with the example configuration of the vehicle power supply system 1.

[0021] Here, the connector 22 shown in the figure is a connector formed with various terminals for connecting a diagnostic machine, and in this example is a connector for a CAN (Controller Area Network). When a CAN communication device such as a diagnostic machine is connected to the connector 22, power can be supplied from the vehicle power supply system 1 to the communication device via the connector 22.

[0022] As shown in the figure, the vehicle power supply system 1 includes an auxiliary battery unit 10 and a switch unit 20 .

[0023] The auxiliary battery unit 10 includes an auxiliary battery 11, a relay 12, and a control unit 13. The auxiliary battery unit 10 also includes terminals formed therein, including a positive terminal Tp, a negative terminal Tm, a data terminal Td, a switch signal terminal Ts, and a GND (ground) terminal Tg.

[0024] Outside the auxiliary battery unit 10, the auxiliary devices 3 are inserted between a positive terminal Tp and a negative terminal Tm grounded to GND, as shown in the figure. Similarly, the DC / DC converter 7 and the high-voltage battery 5 are also inserted between the positive terminal Tp and the negative terminal Tm.

[0025] Within the auxiliary battery unit 10, a series-connected circuit of a relay 12 and the auxiliary battery 11 is inserted between the positive terminal Tp and the negative terminal Tm. The relay 12 is configured as an electromagnetic relay, and its on / off switching is controlled by a control unit 13. When the relay 12 is on, the auxiliary battery 11 and the positive terminal Tp are electrically connected, allowing power from the auxiliary battery 11 to be supplied to the auxiliary devices 3. Furthermore, the electrical connection between the auxiliary battery 11 and the positive terminal Tp allows power from the high-voltage battery 5 to be charged to the auxiliary battery 11 via the DC / DC converter 7. On the other hand, when the relay 12 is off, the auxiliary battery 11 and the positive terminal Tp are electrically disconnected, preventing the auxiliary battery 11 from supplying power to the auxiliary devices 3. Furthermore, charging of the auxiliary battery 11 by the high-voltage battery 5 is also disabled.

[0026] The control unit 13 is configured with a microcomputer having, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and the CPU executes various processes in accordance with programs stored in the ROM, thereby performing various controls related to the auxiliary battery unit 10. Although not shown in the figure, the control unit 13 is supplied with power from the auxiliary battery 11.

[0027] The control unit 13 is capable of performing data communication with an external device, such as a diagnostic machine, connected to the connector 22 via the data terminal Td. The control unit 13 is also capable of performing data communication with an in-vehicle ECU (not shown) via the data terminal Td. The control unit 13 is also capable of executing processing based on external instructions, such as commands sent by the diagnostic machine.

[0028] The control unit 13 also has a function of monitoring the state of the auxiliary battery 11. For example, the control unit 13 is capable of monitoring the output voltage value, output current value, battery temperature, etc. of the auxiliary battery 11 and calculating the SOC (State Of Charge) and SOH (State Of Health).

[0029] Furthermore, the control unit 13 also controls the relay 12 based on the result of monitoring the state of the auxiliary battery 11. Specifically, in this embodiment, the control unit 13 controls the relay 12 to be turned off in response to a decrease in the remaining charge of the auxiliary battery 11, thereby performing low-capacity cutoff control, which cuts off the power supply from the auxiliary battery 11 to the auxiliaries 3. For example, the control unit 13 controls the relay 12 to be turned off in response to detection that the SOC of the auxiliary battery 11 has become equal to or lower than a predetermined threshold. Note that, with regard to the low-capacity cutoff control, the condition for turning off the relay 12 is not limited to the condition that the SOC becomes equal to or lower than the predetermined threshold. For example, other conditions can be defined, such as incorporating a time element to set the condition that the state in which the SOC is equal to or lower than the predetermined threshold has elapsed for a predetermined period of time, or incorporating a frequency element to set the condition that the number of times per unit time the SOC becomes equal to or lower than a certain value is equal to or higher than a predetermined number of times.

[0030] By performing the above-described shut-off control when capacity is low, when a lithium ion battery is used as the auxiliary battery 11, it is possible to prevent the auxiliary battery 11 from becoming irreversibly unusable.

[0031] Here, the above-described low-capacity shutoff control causes a loss of power to the auxiliaries 3, including various on-board ECUs (Electric Control Units), making it impossible to restart the vehicle even if repairs or recharging are desired (since the power supply to the auxiliaries 3 has been lost, the diagnostic equipment also becomes unusable). Therefore, when attempting to recharge the auxiliary battery 11 and reuse it, it is necessary to connect a separate power source to the vehicle to enable power supply to the diagnostic equipment and send a restart command to the control unit 13, or, if there is no separate power source near the vehicle, remove the auxiliary battery unit 10 and send a restart command to the control unit 13 in an environment where power can be supplied, or replace the auxiliary battery unit 10 with a new one, etc., which complicates the work and leads to increased repair costs.

[0032] Therefore, in this embodiment, a switch unit 20 that can be switched between an ON state and an OFF state by operation is provided, and the control unit 13 controls the relay 12 to be ON when the switch unit 20 is turned ON while the relay 12 is OFF. As a result, even if power supply to the auxiliary equipment 3 is stopped due to the low-capacity cutoff control for protecting the auxiliary battery 11, when the user turns on the switch unit 20, the relay 12 is forcibly turned ON, thereby enabling power supply to the auxiliary equipment 3. Once power supply to the auxiliary equipment 3 is enabled, the system starts up, and the auxiliary battery 11 can be charged by the high-voltage battery 5. Thereafter, power supply from the auxiliary battery 11 to the auxiliary equipment 3 can be continued as usual. In other words, in this case, the only action required to deal with a dead battery is for the user to turn on the switch unit 20. In this way, even when a lithium-ion battery is provided as the auxiliary battery, the response to a dead battery can be prevented from becoming complicated.

[0033] The switch unit 20 may be configured as a physical switch, such as a push button switch, a knob switch, a slide switch, or a dial switch, provided at a predetermined position in the vehicle. The switch unit 20 may also be configured as a virtual switch using a GUI (Graphical User Interface). In either case, the switch unit 20 may be configured as a toggle switch that can be switched from an off state to an on state and vice versa.

[0034] The vehicle power supply system 1 is formed with a switch signal supply unit 21 for supplying a switch signal indicating the on or off state of the switch unit 20 to the control unit 13. As shown in the figure, one terminal of the switch unit 20 is connected to the control unit 13 via a switch signal terminal Ts. The line connected from one terminal of the switch unit 20 to the control unit 13 via the switch signal terminal Ts is referred to as the positive line of the switch signal. The other terminal of the switch unit 20 is connected to the control unit 13 via a GND terminal Tg. The line connected from the other terminal of the switch unit 20 to the control unit 13 via the GND terminal Tg is referred to as the negative line of the switch signal.

[0035] In this example, the control unit 13 determines whether the switch unit 20 is turned on by determining whether the switch signal has changed from an off level to an on level. This makes it possible to distinguish between cases where the switch unit 20 is stuck on and improves the accuracy of the on / off determination of the switch unit 20. In particular, it is possible to prevent the relay 12 from also being stuck on when the switch unit 20 is stuck on, and it is possible to prevent erroneous power supply from the auxiliary battery 11 to the auxiliary devices 3 under low-capacity cutoff control.

[0036] In this example, the switch signal supply unit 21 is configured to supply the control unit 13 with a signal having a predetermined voltage value that is less than the output voltage of the auxiliary battery 11 when the switch unit 20 is turned on. Specifically, the switch signal supply unit 21 in this example includes a resistor Ru as a pull-up resistor connected to the positive line of the switch signal, and a resistor Rd as a pull-down resistor connected to the negative line of the switch signal, as shown in the figure, so that when the switch unit 20 is turned on, the switch signal supply unit 21 can supply the control unit 13 with a signal having a predetermined voltage value that is less than the output voltage of the auxiliary battery 11. Although not shown in the figure, a 12V voltage powered by the auxiliary battery 11 is connected to the resistor Ru as a pull-up resistor.

[0037] In this example, in accordance with the configuration of the switch signal supply unit 21 described above, the control unit 13 determines whether the switch unit 20 is turned on based on whether a signal is supplied at the predetermined voltage value. For example, if the design value of the predetermined voltage value is 5 V, the control unit 13 determines whether the voltage value of the supplied switch signal is 5 V. In this case, it is conceivable to define a voltage range that can be regarded as a predetermined voltage value such as 5 V, and determine whether the voltage value of the supplied switch signal is within that voltage range. Specifically, if the design value of the predetermined voltage value is 5 V, for example, 4 V and 6 V are defined as thresholds for the voltage range, and it is determined whether the voltage value of the supplied switch signal is within the range from 4 V to 6 V.

[0038] The above-described configuration of the switch signal supply unit 21 and the method for determining whether the switch unit 20 is on can prevent the switch unit 20 from being erroneously determined to be in the on state when the switch signal supply line is shorted to GND. That is, the relay 12 can be prevented from being stuck on when there is a GND short, and the auxiliary battery 11 can be prevented from erroneously supplying power to the auxiliary devices 3 under low-capacity cutoff control.

[0039] Furthermore, in this example, when a predetermined exceptional condition is met, the control unit 13 maintains the relay 12 in the OFF state, regardless of whether the switch unit 20 is in the ON state or the OFF state. Specifically, when a predetermined exceptional condition that could lead to battery failure, such as an overcurrent, overcharging, high temperature, or over-discharge of the auxiliary battery 11, is met while the relay 12 is in the OFF state, the control unit 13 maintains the relay 12 in the OFF state even if the switch unit 20 is turned ON. This prevents failure of the auxiliary battery 11 and improves safety.

[0040] A specific example of the processing procedure of the control unit 13 will be described with reference to the flowchart of Fig. 3. The control unit 13 executes the processing shown in Fig. 3 while the relay 12 is in the OFF state.

[0041] First, in step S101, the control unit 13 waits until the switch unit 20 is turned on. Specifically, in this example, the resistors Ru and Rd are designed to supply a switch signal with a predetermined voltage value less than 12 V when the switch unit 20 is turned on. Therefore, the control unit 13 determines whether the switch signal has reached this predetermined voltage value as a determination of whether the switch unit 20 has been turned on (specifically, as described above, a determination is made using two thresholds, but details will be omitted to avoid redundancy). At this time, in this example, a change in the switch signal from an OFF level to an ON level is included in the determination conditions. Therefore, in the process of step S101, the control unit 13 first determines whether a change in the voltage value of the switch signal equal to or greater than the threshold value has been detected, and, upon detection of this change, determines whether the voltage value after the change has reached the predetermined voltage value less than 12 V as described above.

[0042] If it is determined in step S101 that the switch unit 20 is turned on, the control unit 13 proceeds to step S102 and determines whether an exceptional condition is satisfied. Specifically, in this example, the exceptional conditions are an overcurrent, overcharge, high temperature, and overdischarge of the auxiliary battery 11, as exemplified above, and the control unit 13 determines whether any of these conditions is satisfied.

[0043] If it is determined in step S102 that the exceptional condition is not met, the control unit 13 proceeds to step S103 and controls the relay 12 to be on.

[0044] On the other hand, if it is determined in step S102 that the exceptional condition is met, the control unit 13 proceeds to step S104 and maintains the relay 12 in the OFF state.

[0045] The control unit 13 ends the series of processes shown in FIG. 3 in response to execution of the process of either step S103 or S104.

[0046] Although the above example shows a case where it is determined whether an exceptional condition is met based on whether the switch unit 20 is determined to be on, it is also possible to determine whether an exceptional condition is met, and if it is determined that the exceptional condition is met, to perform processing to maintain the relay 12 in the off state without executing an on determination of the switch unit 20. In either case, if an exceptional condition is met, the relay 12 is maintained in the off state regardless of whether the switch unit 20 is on or off.

[0047] Here, in the above, examples of configuring the switch unit 20 as a physical switch include push button switches and knob switches, but such button switches can detract from the design depending on the installation location and require manufacturing costs for the switch components, while as the switch unit 20, it is a so-called emergency switch and will not be used frequently over the life cycle of the vehicle.

[0048] In consideration of this point, the switch unit 20 may be configured as a switch that is switched between an ON state and an OFF state by inserting or removing a fuse 25 in a fuse box 30 of the vehicle, such as a switch unit 20A shown in Fig. 4. Specifically, the switch unit 20A has a terminal unit 20a (including at least a positive terminal and a negative terminal) formed in the fuse box 30. The switch unit 20A is configured to be switched between an ON state and an OFF state by inserting or removing a fuse 25 into or from this terminal unit 20a.

[0049] This makes it possible to prevent the design from being damaged when providing the switch section 20 in the vehicle, and also to reduce costs since a spare fuse provided in the vehicle can be used as the fuse 25.

[0050] The present embodiment is not limited to the specific example described above, and various modified configurations are possible. For example, although the above example illustrates a case where a lithium-ion battery is used as the auxiliary battery 11, the auxiliary battery 11 is not limited to a lithium-ion battery and may be any battery that can be subject to low-capacity cutoff control.

[0051] Furthermore, although the above example illustrates the application of the present invention to an HEV, the present invention can also be suitably applied to vehicles such as BEVs (Battery Electric Vehicles) that do not have an engine, or to engine vehicles that do not have a traction motor and use an engine as a drive source for the wheels.

[0052] As described above, a vehicle power supply system (1) according to an embodiment of the present invention includes an auxiliary battery (11) provided as a power source for auxiliary equipment in a vehicle, a relay (12) inserted between the auxiliary battery and the auxiliary equipment, a control unit (13) that performs low-capacity cutoff control by turning off the relay in response to a decrease in the remaining charge of the auxiliary battery, thereby cutting off power supply from the auxiliary battery to the auxiliary equipment, and a switch unit (20, 20A) that can be switched between an on state and an off state. When the control unit detects that the switch unit is turned on while the relay is off, the control unit turns on the relay. Thus, even if power supply to the auxiliary equipment has been stopped by the low-capacity cutoff control for protecting the auxiliary battery, if the user turns on the switch unit, the relay is forcibly turned on, thereby enabling power supply to the auxiliary equipment. Therefore, even if a lithium-ion battery is installed as an auxiliary battery, it is possible to prevent the response work when the battery dies from becoming complicated, and to prevent the ease of maintenance from decreasing compared to when a conventional lead battery is used.

[0053] In addition, in the vehicle power supply system according to the embodiment, the control unit determines whether the switch unit is turned on by determining whether a switch signal indicating the on or off state of the switch unit has changed from an off level to an on level. This makes it possible to distinguish between cases where the switch unit is stuck on and improves the accuracy of the on / off determination of the switch unit. In particular, this prevents the relay from also being stuck on when the switch unit is stuck on, thereby preventing erroneous power supply from the auxiliary battery to the auxiliary devices under low-capacity shutoff control.

[0054] Furthermore, the vehicle power supply system according to the embodiment includes a switch signal supply unit (21) that supplies a signal of a predetermined voltage value less than the output voltage of the auxiliary battery to the control unit when the switch unit is turned on. The control unit determines whether the switch unit is turned on based on the presence or absence of the signal supply of the predetermined voltage value. This prevents the relay from being stuck on when the switch signal supply line is shorted to ground, and prevents erroneous power supply from the auxiliary battery to the auxiliary devices under low-capacity shutoff control.

[0055] Furthermore, in the vehicle power supply system according to the embodiment, when a predetermined exceptional condition is met, the control unit maintains the relay in the off state regardless of whether the switch unit is in the on or off state. As a result, when a predetermined exceptional condition that could lead to battery failure, such as an overcurrent, overcharging, high temperature, or over-discharge of the auxiliary battery, is met, power is not supplied from the auxiliary battery to the auxiliary devices even if the switch unit is turned on. This improves safety.

[0056] In the vehicle power supply system according to the embodiment, the switch unit (20A) is configured as a switch that is switched between an on state and an off state by inserting or removing a fuse into or from a terminal portion formed in a fuse box of the vehicle. This prevents the design from being damaged when providing the switch unit in the vehicle, and also reduces costs by allowing the spare fuse installed in the vehicle to be used instead.

[0057] REFERENCE SIGNS LIST 1 Vehicle power supply system 2 Engine 3 Auxiliary equipment 4 MG (motor generator) 5 High voltage battery 6 Inverter 7 DC / DC converter 10 Auxiliary battery unit 11 Auxiliary battery 12 Relay 13 Control unit 20, 20A Switch unit 21 Switch signal supply unit 22 Connector unit Ru, Rd Resistor Ts Switch signal terminal Tg GND terminal Tp Positive terminal Tm Negative terminal Td Data terminal 20a Terminal unit 25 Fuse 30 Fuse box

Claims

1. A vehicle power supply system comprising: an auxiliary battery provided as a power source for auxiliary equipment in a vehicle; a relay inserted between the auxiliary battery and the auxiliary equipment; a control unit that controls the relay to turn off in response to a decrease in the remaining charge of the auxiliary battery and performs low-capacity cut-off control to cut off power supply from the auxiliary battery to the auxiliary equipment; and a switch unit that can be switched between an on state and an off state, wherein the control unit controls the relay to turn on when it detects that the switch unit has been turned on while the relay is off.

2. The vehicle power supply system according to claim 1, wherein the control unit determines whether the switch unit is turned on by determining whether a switch signal indicating the on or off state of the switch unit has changed from an off level to an on level.

3. The vehicle power supply system according to claim 1, further comprising a switch signal supply unit that supplies a signal of a predetermined voltage value less than the output voltage of the auxiliary battery to the control unit when the switch unit is turned on, and the control unit determines whether the switch unit is turned on based on whether or not a signal of the predetermined voltage value is supplied.

4. The vehicle power supply system according to claim 1, wherein the control unit maintains the relay in an off state when a predetermined exceptional condition is met, regardless of whether the switch unit is in an on state or an off state.

5. A vehicle power supply system as set forth in any one of claims 1 to 4, wherein the switch section is configured as a switch that is switched between an on state and an off state by inserting or removing a fuse into or from a terminal section formed in a fuse box of the vehicle.

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