Current circuit interruption system and current circuit interruption method

Abstract

Disclosed is a current circuit interruption system that makes it possible to reduce the interruption performance required of main relays and to lower the cost and reduce the size of the main relays and the system as a whole.　A current circuit interruption system 10 comprises: a current circuit 12 that includes a pair of main relays 22a, 22b and a precharge circuit 28; and a control unit 30 that transmits ON / OFF signals to the pair of main relays 22a, 22b and a precharge relay 26. The control unit 30 executes a circuit interruption operation 11. The circuit interruption operation 11 includes a precharge relay ON operation 42 that turns the precharge relay 26 ON, a one-side main relay OFF operation 44 that follows the precharge relay ON operation 42 and turns one main relay 22a OFF, and a final OFF operation 46 that follows the one-side main relay OFF operation 44 and turns at least one of the precharge relay 26 and the other main relay 22b OFF.

Description

Current Circuit Interruption System and Current Circuit Interruption Method

[0006] ,

[0001] The present disclosure relates to a current circuit interruption system and a current circuit interruption method.

[0002] Conventionally, vehicles equipped with a battery composed of a high-voltage secondary battery such as an electric vehicle or a hybrid vehicle have a current circuit interruption system including a relay. For example, Patent Document 1 discloses a current circuit interruption system provided with a main relay that interrupts the power supply from a battery to a motor or a generator connected via an inverter as a load on the vehicle side. The main relay used in such a current circuit is provided on the positive electrode side and the negative electrode side, and by turning off the main relay, the power supply from the battery can be stopped.

[0003] Japanese Patent Application Laid-Open No. 2010-213500

[0004] In such a current circuit interruption system, in order to surely interrupt a large current from the battery in case of vehicle abnormality, the main relay itself is required to have a high short-circuit withstand capacity and interruption performance. That is, in case of vehicle abnormality, it can be roughly divided into two cases: one is to disconnect the battery by fusing a fuse assuming a short circuit of a large current near the battery due to a collision accident or the like, and the other is to disconnect the battery by sending an OFF signal from an ECU to the main relay to turn off the main relay due to a system abnormality in the main circuit. Therefore, the main relay constituting the current circuit is required to have a high short-circuit withstand capacity to keep the contacts ON against the electromagnetic repulsive force of the short-circuit current and a high interruption performance to interrupt the overcurrent in case of system abnormality by turning off the main relay. As a result, the main relay is inevitably enlarged and increased in cost. Furthermore, when the required short-circuit withstand capacity of the main relay cannot be ensured, a new interruption device such as a pilot fuse is required, and the enlargement and cost increase of the current circuit interruption system cannot be avoided.

[0005] Therefore, a current circuit interruption system and a current circuit interruption method are disclosed that can reduce the interruption performance required for the main relay and can reduce the cost and size of the main relay and the entire system.

[0006] The current circuit interruption system of the present disclosure comprises a current circuit including a pair of power lines connecting a battery and a load, a pair of main relays connected to each of the pair of power lines, a precharge circuit connected in parallel to one of the pair of main relays and including a precharge resistor and a precharge relay connected in series, and a control unit that sends ON / OFF signals to the pair of main relays and the precharge relay of the current circuit, wherein the control unit performs a circuit interruption operation, the circuit interruption operation including a precharge relay ON operation which sends an ON signal to the precharge relay to turn the precharge relay ON, a one-side main relay OFF operation which, after the precharge relay ON operation, sends an OFF signal to one of the main relays to which the precharge circuit is connected in parallel to turn the one of the main relays OFF, and a final OFF operation which, after the one-side main relay OFF operation, sends an OFF signal to at least one of the precharge relay and the other main relay to turn the precharge relay and at least one of the other main relays OFF.

[0007] The current circuit interruption method of the present disclosure is performed on a current circuit comprising a pair of power lines connecting a battery and a load, a pair of main relays connected to each of the pair of power lines, and a precharge circuit connected in parallel to one of the pair of main relays, the pair of main relays and the precharge relay being connected to a control unit, wherein the control unit performs a precharge relay ON operation, which involves sending an ON signal to the precharge relay to turn the precharge relay ON; a one-side main relay OFF operation, which involves sending an OFF signal to one of the main relays to which the precharge circuit is connected in parallel after the precharge relay ON operation to turn one of the main relays OFF; and a final OFF operation, which involves sending an OFF signal to at least one of the precharge relay and the other main relay to turn the precharge relay and the other main relay OFF after the one-side main relay OFF operation.

[0008] According to the current circuit interruption system and current circuit interruption method of this disclosure, the interruption performance required of relays can be reduced, and the relays and the entire system can be made more cost-effective and smaller.

[0009] Figure 1 is a schematic diagram showing the electrical configuration of the current circuit interruption system according to Embodiment 1. Figure 2 is an explanatory diagram for explaining the circuit interruption operation in the current circuit interruption system shown in Figure 1. Figure 3 is an explanatory diagram for explaining the circuit interruption operation in a conventional current circuit interruption system. Figure 4 is an explanatory diagram for explaining the circuit interruption operation in the current circuit interruption system according to Embodiment 2.

[0010] <Description of Embodiments of the Disclosure> First, embodiments of the Disclosure will be listed and described. The current circuit interruption system of the present disclosure comprises: (1) a current circuit including a pair of power lines connecting a battery and a load, a pair of main relays connected to each of the pair of power lines, and a precharge circuit connected in parallel to one of the pair of main relays, which includes a precharge resistor and a precharge relay connected in series; and a control unit which sends ON / OFF signals to the pair of main relays and the precharge relay of the current circuit, wherein the control unit performs a circuit interruption operation, the circuit interruption operation including a precharge relay ON operation which sends an ON signal to the precharge relay to turn the precharge relay ON; a one-side main relay OFF operation which, after the precharge relay ON operation, sends an OFF signal to one of the main relays to which the precharge circuit is connected in parallel to turn the one of the main relays OFF; and a final OFF operation which, after the one-side main relay OFF operation, sends an OFF signal to at least one of the precharge relay and the other main relay to turn the precharge relay and at least one of the other main relays OFF.

[0011] The current circuit interruption system of this disclosure includes a current circuit comprising a pair of power lines (a positive power line and a negative power line), each connected to a main relay, and a precharge circuit in parallel connected to one of the main relays, with a precharge resistor and a precharge relay connected in series; and a control unit capable of performing circuit interruption operations. In the circuit interruption operation performed by the control unit, an ON operation is performed to turn on the precharge relay by sending an ON signal to the precharge relay, then, with the precharge relay turned ON, an OFF operation is performed to turn off one of the main relays on the side to which the precharge circuit is connected in parallel, and finally, a final OFF operation is performed to turn off the precharge relay and the other main relay. As a result, when the final OFF operation is performed in the event of a vehicle malfunction, the current flowing through the current circuit is the current that passes through the precharge resistor, so the current flowing through the current circuit is kept small compared to the normal state when the current passes through each main relay. As a result, it is possible to reduce the interruption performance required of the main relays. Therefore, it is possible to provide a current circuit interruption system that enables cost reduction and miniaturization of the main relay, and consequently, cost reduction and miniaturization of the entire system. Furthermore, since the interruption performance of the main relay can be reduced, it becomes easier to specialize in improving the short-circuit withstand capability, and the need for new interruption devices such as pyrofuses can be reduced, further cost reduction and miniaturization can be achieved.

[0012] Furthermore, since pre-charge circuits are provided on the pair of power lines connecting the battery and the load to reduce the effects of startup current and protect the system and components from excessive voltage and current, it is possible to reduce the cost and size of relays, and ultimately the cost and size of the entire system, without requiring new components, by utilizing existing pre-charge circuits.

[0013] Furthermore, the pre-charge relay ON operation may be performed by using an operation to turn it ON when the vehicle starts up, or the pre-charge relay may be turned OFF after the vehicle has started up, and then the pre-charge relay ON operation may be performed in response to the detection of a vehicle abnormality signal.

[0014] Furthermore, the target to be turned OFF at the stage of performing the final OFF operation may be either the other main relay or the pre-charge relay, or both.

[0015] (2) In the above (1), it is preferable that the current circuit is equipped with a fuse connected to the power line, and that the battery is disconnected from the current circuit when the fuse blows.

[0016] By reducing the interruption performance of the main relay, it becomes possible to focus on improving the short-circuit withstand capability of the main relay. This effectively suppresses malfunctions such as the main relay igniting before the fuse blows, even in the event of a large-current short circuit near the battery, such as in a collision, and allows for stable disconnection of the battery by the blown fuse. This also makes it possible to eliminate the need for additional interruption devices such as pyrofuses that were used in conjunction when the required short-circuit withstand capability of the main relay could not be ensured, enabling further miniaturization and cost reduction of the current circuit interruption system.

[0017] (3) In (1) or (2) above, it is preferable that the pre-charge relay ON operation is achieved by maintaining the pre-charge relay in the ON state when the vehicle is started. Since the pre-charge relay ON operation is performed when the vehicle is started, the pre-charge relay is already in the ON state when a vehicle malfunction occurs, and the subsequent one-side main relay OFF operation and final OFF operation can be performed quickly.

[0018] (4) In (1) or (2) above, it is preferable that the pre-charge relay ON operation is performed after the control unit detects a vehicle abnormality signal. Since the pre-charge relay, which was turned ON when the vehicle was started, is turned OFF once, and the pre-charge relay ON operation is performed when a vehicle abnormality signal is detected, it is not necessary to keep the pre-charge relay ON at all times, and power consumption can be reduced.

[0019] The current circuit interruption method of the present disclosure is a current circuit interruption method performed on a current circuit comprising: (5) a pair of power lines connecting a battery and a load; a pair of main relays connected to the pair of power lines, respectively; and a precharge circuit connected in parallel to one of the pair of main relays, which includes a precharge resistor and a precharge relay connected in series, wherein the pair of main relays and the precharge relay are connected to a control unit, wherein the control unit performs a precharge relay ON operation, which involves transmitting an ON signal to the precharge relay to turn the precharge relay ON; a one-side main relay OFF operation, which involves transmitting an OFF signal to one of the main relays to which the precharge circuit is connected in parallel after the precharge relay ON operation to turn one of the main relays OFF; and a final OFF operation, which involves transmitting an OFF signal to at least one of the precharge relay and the other main relay to turn the precharge relay and at least one of the other main relay OFF after the one-side main relay OFF operation.

[0020] According to the current circuit interruption method of the present disclosure, the control unit can perform the same operation as the circuit interruption operation described in the embodiment of (1) above by performing the precharge relay ON operation, the one-side main relay OFF operation and the final OFF operation, and can achieve the same effects as the embodiment of (1) above.

[0021] <Details of Embodiments of the Disclosure> Specific examples of the current circuit interruption system and current circuit interruption method of the Disclosure will be described below with reference to the drawings. However, the Disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the Claims as indicated by the Claims.

[0022] <Embodiment 1> Hereinafter, the current circuit interruption system 10 of Embodiment 1 of the present disclosure will be described with reference to Figures 1 and 2. This current circuit interruption system 10 is applicable, for example, to electric vehicles and hybrid vehicles, and in the event of a vehicle emergency such as an accident, the current flowing through the current circuit 12 can be stably interrupted by performing a predetermined circuit interruption operation 11. Note that for multiple identical components, reference numerals may be assigned to only some of the components, while the reference numerals for other components may be omitted.

[0023] <Current Circuit Interruption System 10> As shown in Figure 1, the current circuit 12 in the current circuit interruption system 10 includes a pair of power lines 20, 20 (+-side power line 20a and --side power line 20b) connecting the battery 14 and the load, which is the inverter 16 and motor 18, and a pair of main relays 22, 22 (a +-side main relay 22a, which is the main relay on one side, and a --side main relay 22b, which is the main relay on the other side) connected to each power line 20a and 20b, respectively. In addition, this current circuit 12 includes a pre-charge circuit 28 connected in parallel to one of the main relays 22 (in Embodiment 1, the +-side main relay 22a), which includes a pre-charge resistor 24 and a pre-charge relay 26 connected in series.

[0024] Furthermore, the current circuit interruption system 10 includes a control unit 30 that sends ON / OFF signals to each of the main relays 22a, 22b and the pre-charge relay 26 in the current circuit 12.

[0025] <Current Circuit 12> As described above, the current circuit 12 includes power lines 20a and 20b to which the main relays 22a and 22b are connected, and a precharge circuit 28 (precharge resistor 24 and precharge relay 26) connected in parallel to the + side main relay 22a. In Embodiment 1, on the + side power line 20a, the current sensor 32 is connected to the battery 14 side of the + side main relay 22a and precharge circuit 28. Also, on the - side power line 20b, the fuse 34 is connected to the battery 14 side of the - side main relay 22b. A capacitor 36 is connected in parallel with the inverter 16 between the + side power line 20a and the - side power line 20b. The power lines 20a and 20b connect the battery 14 and the inverter 16, and the motor 18 is connected to the inverter 16. That is, the battery 14 and the motor 18 are connected via the inverter 16.

[0026] In the current circuit 12 described above, the main relays 22a and 22b, the precharge circuit 28 (precharge resistor 24 and precharge relay 26), and the fuse 34 may be arranged in an electrical junction box 38, for example, shown by the dashed line in Figure 1. In the current circuit 12, the battery 14, inverter 16, motor 18, current sensor 32, and capacitor 36, which are provided outside the electrical junction box 38, may be of known type. The precharge resistor 24 and fuse 34 may also be of known type. The fuse 34 may be a known fused fuse or a pyro fuse, but if a fused fuse is used as the fuse 34, it is possible to prevent a malfunction in which, for example, a signal to activate the pyro fuse cannot be sent in the event of an accident or other abnormality in the vehicle, and the pyro fuse does not activate. When this fuse 34 is cut (blown if it is a fused fuse), the battery 14 is disconnected from the current circuit 12.

[0027] <Main Relay 22 (+-side Main Relay 22a and --side Main Relay 22b)> The specific structure of each main relay 22a and 22b is not limited, but in Embodiment 1, known mechanical relays (contact relays) are used as each main relay 22a and 22b. Note that each main relay 22a and 22b may be a semiconductor relay (non-contact relay). Such relays generally have a certain degree of interruption performance and short-circuit performance. Here, interruption performance indicates the performance of how large a current can be interrupted when an interruption signal (OFF signal) is received from an external source (for example, the control unit 30), that is, the performance necessary to more reliably interrupt the current. If a current larger than the interruption performance is attempted to be interrupted, the relay may be damaged and reliable interruption of the current may not be achieved.

[0028] On the other hand, short-circuit performance refers to the ability of a relay to withstand a large current when a short circuit occurs in the event of an accident, without being damaged. In other words, it is a necessary performance to prevent the relay from being interrupted due to damage. Since the relay will be damaged if a current exceeding the short-circuit performance flows through the circuit, the circuit must be interrupted, for example, by a fuse, before the current flowing through the circuit exceeds the relay's short-circuit performance. In other words, the relay needs to maintain the energized state of the circuit until it is interrupted by the fuse, and short-circuit performance is the performance necessary to maintain that energized state. In short, the interruption performance and short-circuit performance of conventional relays are conflicting performances, but both are necessary to avoid damage to the relay. For example, the idea of ​​improving only one of the performances, or eliminating one of the performances, did not exist in the past. When improving both interruption performance and short-circuit performance, it was necessary to improve both performances, which led to the problem of increasing the size of the relay.

[0029] In the current circuit interruption system 10 of this disclosure, each main relay 22a, 22b can have its interruption performance reduced by performing the circuit interruption operation 11, or it can be a relay that does not need to have interruption performance and is specialized for short-circuit performance. Such a relay specialized for short-circuit performance can be easily manufactured by changing the internal structure of the relay.

[0030] <Pre-charge relay 26> The specific structure of the pre-charge relay 26 is not limited, and known mechanical relays (contact relays) or semiconductor relays (non-contact relays) can be used. The pre-charge relay 26 may also have interruption performance, and relays specialized in interruption performance can be easily manufactured by changing the internal structure of the relay.

[0031] <Control Unit 30> The control unit 30 of Embodiment 1 is configured to execute the circuit disconnection operation 11 shown in Figure 2. The circuit disconnection operation 11 includes a precharge relay ON operation 42, which sends an ON signal to the precharge relay 26 to turn the precharge relay 26 ON, and a one-side main relay OFF operation 44, which, after the precharge relay ON operation 42, sends an OFF signal to one of the main relays 22 (+side main relay 22a) to which the precharge circuit 28 is connected in parallel, to turn the +side main relay 22a OFF. Furthermore, the circuit disconnection operation 11 includes a final OFF operation 46, which, after the one-side main relay OFF operation 44, sends an OFF signal to at least one of the precharge relay 26 and the other main relay 22 (-side main relay 22b) to turn the precharge relay 26 and the -side main relay 22b OFF. In particular, in Embodiment 1, the pre-charge relay ON operation 42 is achieved by maintaining the pre-charge relay 26 in the ON state when the vehicle is started.

[0032] The specific configuration of the control unit 30 is not limited, but for example, it may include a microcomputer mounted on a circuit board electrically connected to the current circuit 12, and this microcomputer can transmit ON / OFF signals to each of the main relays 22a, 22b and the precharge relay 26.

[0033] <Current Circuit Interruption Method> The current circuit interruption method according to this disclosure will be described below, with particular use of Figure 2. That is, the current circuit interruption method of this disclosure is performed on the current circuit 12 described above. Figure 2 shows the ON / OFF states of the precharge relay 26, the + side main relay 22a, and the - side main relay 22b, with the horizontal axis being the time axis. Note that Figure 2 is a simplified representation of the ON / OFF states of the precharge relay 26, the + side main relay 22a, and the - side main relay 22b over time, and the length of time shown on the time axis (the length of time shown in the left-right direction in Figure 2) may not match the actual length of time.

[0034] As shown in Figure 2, before the vehicle starts up, the pre-charge relay 26, the positive main relay 22a, and the negative main relay 22b are all in the OFF state. When the vehicle starts up, the control unit 30 first sends an ON signal to the negative main relay 22b, which then turns ON. If the positive main relay 22a is turned ON in this state to charge the capacitor 36, an extremely large inrush current will flow instantaneously, which may damage the main relays 22a and 22b. To avoid this problem, a pre-charge circuit 28 is provided. That is, with the positive main relay 22a still in the OFF state, the control unit 30 sends an ON signal to the pre-charge relay 26 to perform a pre-charge relay ON operation 42, which turns the pre-charge relay 26 ON. This allows the capacitor 36 to be charged by a relatively low current that has passed through the pre-charge resistor 24.

[0035] Subsequently, after the capacitor 36 has charged to a certain extent, the control unit 30 sends an ON signal to the +-side main relay 22a while the pre-charge relay 26 remains ON, thereby turning on the +-side main relay 22a. This enables charging of the capacitor 36 through the +-side power line 20a, and also supplies power to the motor 18 via the inverter 16, making the vehicle suitable for driving. In other words, in Embodiment 1, after the vehicle is started (for example, during normal operation such as when the vehicle is running), the pre-charge relay 26, the +-side main relay 22a, and the --side main relay 22b are all in the ON state. Even when both the pre-charge relay 26 and the +-side main relay 22a are ON, the pre-charge circuit 28 is equipped with a pre-charge resistor 24, so almost no current flows through the pre-charge circuit 28 compared to the +-side power line 20a.

[0036] Then, at some point, an abnormality occurs in the vehicle due to an accident or the like. In that case, if the circuit is short-circuited or the current sensor 32 detects a current value that exceeds the tripping capacity of each main relay 22a, 22b, that is, if the control unit 30 detects a vehicle abnormality signal, the control unit 30 sends an OFF signal to the + side main relay 22a and performs a one-side main relay OFF operation 44 to turn off the + side main relay 22a. At that time, since the pre-charge relay 26 is maintained in the ON state, the current circuit 12 is not completely shut off when the + side main relay 22a is turned OFF, and current flows through the pre-charge circuit 28. In other words, the OFF operation of the + side main relay 22a does not shut off the current circuit 12, and the + side main relay 22a does not need to have tripping capacity.

[0037] Next, from the above state, the control unit 30 performs a final OFF operation 46, which involves sending an OFF signal to the pre-charge relay 26 to turn off the pre-charge relay 26. This completely shuts off the current circuit 12, and the control unit 30 sends an OFF signal to the negative main relay 22b, which can also be safely turned OFF. As a result, after an abnormality occurs in the vehicle, the pre-charge relay 26, the positive main relay 22a, and the negative main relay 22b are all turned OFF.

[0038] Here, Figure 3 shows a conventional method for interrupting current circuits. Conventionally, as shown in Figure 3, when the +-side main relay was turned ON and power could be supplied through the +-side power line, the pre-charge relay was turned OFF, and the pre-charge relay remained OFF under normal conditions. In this state, if an abnormality occurred in the vehicle due to an accident or the like and a large current flowed through the current circuit, turning the main relay OFF could damage the main relay if the current flowing through the circuit exceeded its interruption capacity, potentially preventing reliable interruption of the current circuit. Furthermore, improving interruption performance also required improving short-circuit performance, which tended to increase the size of the main relay.

[0039] In contrast, according to the current circuit interruption system 10 and current circuit interruption method of Embodiment 1, the control unit 30 executes the circuit interruption operation 11. In the current circuit interruption system 10 of Embodiment 1, the ON state of the precharge relay 26 is maintained even under normal conditions, and when a vehicle abnormality occurs, the + side main relay 22a is turned OFF before the precharge relay 26 by the one side main relay OFF operation 44. With the + side main relay 22a turned OFF in this way, only current flows through the precharge circuit 28 to the current circuit 12, and this current is interrupted by the final OFF operation 46, which turns OFF at least one of the precharge relay 26 and the - side main relay 22b. In other words, the interruption performance required in the final OFF operation 46 is smaller than the interruption performance required in conventional relays, and it is sufficient if at least one of the precharge relay 26 and the - side main relay 22b has the above interruption performance.

[0040] In short, conventional relays, as mentioned above, do not have the concept of specializing in either interruption performance or short-circuit performance, which are conflicting performances. With the increasing currents in recent automobiles, relays have tended to become larger. However, in this disclosure, by adopting the current circuit interruption system 10 of Embodiment 1, the required interruption performance can be kept relatively small. This simplifies the structure related to interruption performance inside the relay, leading to miniaturization and cost reduction of the pre-charge relay 26 and / or each main relay 22a, 22b. In particular, if the pre-charge relay 26 has interruption performance, neither the +-side main relay 22a nor the --side main relay 22b needs to have interruption performance, and relays specialized in short-circuit performance can be used. On the other hand, if the +-side main relay 22a is in the OFF state, only a relatively small current value flows through the current circuit 12 after passing through the pre-charge resistor 24, so the short-circuit performance of the pre-charge relay 26 can be kept small, or it does not need to have short-circuit performance at all. Therefore, the pre-charge relay 26 and the negative-side main relay 22b can share the functions, and by designing each with a structure specialized for its function, further miniaturization and cost reduction can be achieved.

[0041] In the current circuit interruption system 10 of Embodiment 1, it is preferable that the fuse 34 is a blunt fuse. In the event of a vehicle malfunction such as an accident, even if a relatively high-current short-circuit current flows, damage to the negative-side main relay 22b can be prevented, and even if a signal from the control unit 30 cannot be transmitted to the fuse, damage to the negative-side main relay 22b is prevented by the fuse 34 melting due to heat.

[0042] The pre-charge relay ON operation 42 is configured to maintain the pre-charge relay 26 in the ON state when the vehicle is started. That is, in an electric vehicle or a hybrid vehicle, when charging the capacitor 36 at the start of the vehicle, the pre-charge relay 26 is turned on. By maintaining this state, in case of vehicle abnormalities such as accidents, the one-side main relay OFF operation 44 and the final OFF operation 46 can quickly cut off the current circuit 12 without damaging the main relays 22a and 22b.

[0043] <Embodiment 2> Hereinafter, the circuit interruption operation 50 in the current circuit interruption system according to Embodiment 2 of the present disclosure will be described with reference to FIG. 4. In the current circuit interruption system according to Embodiment 2, since the basic circuit structure is the same as that in Embodiment 1, the description thereof will be omitted. In the description of the circuit interruption operation 50 according to Embodiment 2, operations that are substantially the same as those in Embodiment 1 are denoted by the same reference numerals as those in Embodiment 1 in FIG. 4, and detailed description thereof will be omitted.

[0044] <Circuit interruption operation 50> In Embodiment 1, the pre-charge relay ON operation 42 is performed when the vehicle is started, and thereafter, the ON state of the pre-charge relay 26 is maintained until the final OFF operation 46. In Embodiment 2, however, the pre-charge relay ON operation 42 is realized after the control unit 30 detects a vehicle abnormality signal.

[0045] Specifically, as described above, the pre-charge relay 26 is turned on for the purpose of preventing inrush current when charging the capacitor 36 at the start of the vehicle. After that, when the capacitor 36 is charged to a certain extent and the + side main relay 22a is turned on, the control unit 30 transmits an OFF signal to the pre-charge relay 26 to turn off the pre-charge relay 26. That is, in Embodiment 2, during normal times such as when the vehicle is running, the + side main relay 22a and the - side main relay 22b are turned on, and the pre-charge relay 26 is turned off.

[0046] And at a certain point, an abnormality occurs in the vehicle due to an accident or the like. At that time, if a circuit is short-circuited or the like, and a current value exceeding the cutoff performance of each main relay 22a, 22b is detected by, for example, the current sensor 32, that is, when the control unit 30 detects a vehicle abnormality signal, the control unit 30 executes a precharge relay ON operation 42 of transmitting an ON signal to the precharge relay 26 to turn on the precharge relay 26. After that, it is the same as in the first embodiment, and the control unit 30 executes a one-side main relay OFF operation 44 of transmitting an OFF signal to the + side main relay 22a to turn off the + side main relay 22a. Subsequently, from the above state, the control unit 30 executes a final OFF operation 46 of transmitting an OFF signal to the precharge relay 26 to turn off the precharge relay 26. As a result, the current circuit 12 is completely cut off, and by the control unit 30 transmitting an OFF signal to the - side main relay 22b, the - side main relay 22b can also be safely turned off. Thereby, after an abnormality occurs in the vehicle, the precharge relay 26, the + side main relay 22a, and the - side main relay 22b are all turned off.

[0047] Even when the circuit cutoff operation 50 of the second embodiment is adopted, after an abnormality occurs in the vehicle, since it becomes substantially the same state as in the first embodiment, the same effects as in the first embodiment are exhibited. In particular, in the second embodiment, when the + side main relay 22a is turned on and normal vehicle running is started, the precharge relay 26 is turned off and remains off until an abnormality occurs in the vehicle. Thereby, it is not necessary to maintain the precharge relay 26 in the ON state during normal times, and power consumption can be suppressed compared to the first embodiment.

[0048] <Modification Example> Although the first and second embodiments have been described in detail as specific examples of the present disclosure, the present disclosure is not limited by this specific description. Modifications, improvements, etc. within the scope that can achieve the object of the present disclosure are included in the present disclosure. For example, modification examples of the following embodiments are also included in the technical scope of the present disclosure.

[0049] (1) In the embodiments 1 and 2 described above, when starting the vehicle, the negative main relay 22b was turned ON first, and then the pre-charge relay 26 was turned ON. However, the embodiment is not limited to this, and the pre-charge relay may be turned ON first, and then the negative main relay may be turned ON.

[0050] (2) In the embodiments 1 and 2 described above, a precharge circuit 28 was provided on the positive power line 20a, but the precharge circuit may also be provided on the negative power line. In that case, the negative main relay is turned OFF by a one-sided main relay OFF operation performed after a vehicle malfunction occurs.

[0051] (3) In embodiments 1 and 2, the pre-charge relay 26 was turned OFF by the final OFF operation 46, but the negative main relay may be turned OFF, and then the pre-charge relay may be turned OFF. In this case as well, the tripping performance of the negative main relay 22b is kept relatively small, so the same effects as in embodiments 1 and 2 are achieved. In addition, as in the embodiments described above, by turning the pre-charge relay OFF with the final OFF operation, the tripping performance of the positive and negative main relays is not required, and the short-circuit performance of the pre-charge relay is not required, and the functions of each main relay and the pre-charge relay can be divided, so it is preferable to turn the pre-charge relay OFF with the final OFF operation.

[0052] 10 Current circuit interruption system 11 Circuit interruption operation (Embodiment 1) 12 Current circuit 14 Battery 16 Inverter 18 Motor 20 Power line 20a + side power line 20b - side power line 22 Main relay 22a + side main relay (main relay on one side) 22b - side main relay (main relay on the other side) 24 Precharge resistor 26 Precharge relay 28 Precharge circuit 30 Control unit 32 Current sensor 34 Fuse 36 Capacitor 38 Electrical junction box 42 Precharge relay ON operation 44 One side main relay OFF operation 46 Final OFF operation 50 Circuit interruption operation (Embodiment 2)

Claims

1. A current circuit interruption system comprising: a pair of power lines connecting a battery and a load; a pair of main relays connected to each of the pair of power lines; a precharge circuit connected in parallel to one of the pair of main relays, including a precharge resistor and a precharge relay connected in series; and a control unit that sends ON / OFF signals to the pair of main relays and the precharge relay of the current circuit, wherein the control unit is configured to perform a circuit interruption operation, the circuit interruption operation comprising: a precharge relay ON operation which sends an ON signal to the precharge relay to turn the precharge relay ON; a one-side main relay OFF operation which, after the precharge relay ON operation, sends an OFF signal to one of the main relays to which the precharge circuit is connected in parallel to turn the one of the main relays OFF; and a final OFF operation which, after the one-side main relay OFF operation, sends an OFF signal to at least one of the precharge relay and the other main relay to turn the precharge relay and at least one of the other main relays OFF.

2. The current circuit interruption system according to claim 1, wherein the current circuit includes a fuse connected to the power line, and the battery is disconnected from the current circuit when the fuse blows.

3. The current circuit interruption system according to claim 1 or claim 2, wherein the pre-charge relay ON operation is achieved by maintaining the pre-charge relay in an ON state when the vehicle is started.

4. The current circuit interruption system according to claim 1 or 2, wherein the precharge relay ON operation is performed after the control unit detects a vehicle abnormality signal.

5. A current circuit interruption method performed on a current circuit comprising: a pair of power lines connecting a battery and a load; a pair of main relays respectively connected to the pair of power lines; and a precharge circuit connected in parallel to one of the pair of main relays, which includes a precharge resistor and a precharge relay connected in series, wherein the pair of main relays and the precharge relay are connected to a control unit, the method comprising: a precharge relay ON operation in which the control unit transmits an ON signal to the precharge relay to turn the precharge relay ON; a one-side main relay OFF operation in which, after the precharge relay ON operation, the control unit transmits an OFF signal to one of the main relays to which the precharge circuit is connected in parallel to turn the one of the main relays OFF; and a final OFF operation in which, after the one-side main relay OFF operation, the control unit transmits an OFF signal to at least one of the precharge relay and the other main relay to turn the precharge relay and at least one of the other main relays OFF.

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