Current circuit interruption system and current circuit interruption method

Abstract

This invention discloses a current circuit interruption system that can reduce the interruption performance required of the main relay, thereby enabling cost reduction and miniaturization of the main relay and the entire system. [Solution] The current circuit interruption system 10 comprises a current circuit 12 including a pair of main relays 22a, 22b and a precharge circuit 28, and a control unit 30 that sends ON / OFF signals to the pair of main relays 22a, 22b and a precharge relay 26. The control unit 30 is configured to perform a circuit interruption operation 11, which includes a precharge relay ON operation 42 that turns on the precharge relay 26, a one-side main relay OFF operation 44 that turns off one of the main relays 22a after the precharge relay ON operation 42, and a final OFF operation 46 that turns off at least one of the precharge relay 26 and the other main relay 22b after the one-side main relay OFF operation 44.

Description

Technical Field

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

Background Art

[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 intermittently supplies power from a battery to a motor or a generator connected via an inverter as a load on the vehicle side. Such a main relay used in 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such current circuit interruption systems, the main relay itself is required to have high short-circuit withstand capability and interruption performance in order to reliably interrupt the large current from the battery in the event of a vehicle malfunction. In other words, in the event of a vehicle malfunction, the battery is disconnected by blowing a fuse that anticipates a large current short circuit near the battery due to an accident such as a collision, and the battery is disconnected by turning off the main relay when an OFF signal is sent from the ECU to the main relay due to a system malfunction in the main circuit. Therefore, the main relay that constitutes the current circuit is required to have high short-circuit withstand capability to keep the contacts ON against the electromagnetic repulsion force of the short-circuit current, and high interruption performance to interrupt overcurrent in the event of a system malfunction by turning off the main relay. As a result, it is unavoidable that the main relay will become larger and more expensive, and if the required short-circuit withstand capability of the main relay cannot be secured, new interruption devices such as pyrofuses will be required, making it unavoidable that the current circuit interruption system will become larger and more expensive.

[0005] Therefore, we disclose a current circuit interruption system and a current circuit interruption method that can reduce the interruption performance required of the main relay, thereby reducing the cost and miniaturization of the main relay and the entire system. [Means for solving the problem]

[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 by transmitting an ON signal to the precharge relay to turn the precharge relay ON, a one-side main relay OFF operation after the precharge relay ON operation by transmitting 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 after the one-side main relay OFF operation by transmitting 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. [Effects of the Invention]

[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. [Brief explanation of the drawing]

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

[0010] <Description of Embodiments in this Disclosure> First, embodiments of this disclosure will be listed and described. The current circuit interruption system of this disclosure is (1) 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, 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 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.

[0011] The current circuit interruption system of this disclosure includes a current circuit comprising a pair of power lines (+-side power line and --side 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 precharge relay connected in series to one of the main relays, 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, a one-side main relay 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 low 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 can reduce the cost and size of the main relays, and consequently the cost and size of the entire system. Furthermore, since the interruption performance of the main relay can be reduced, it becomes easier to focus on improving short-circuit withstand capability, reducing the need for new interruption devices such as pyrofuses, and enabling further cost reduction and miniaturization.

[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 starts 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 final OFF operation stage 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 precharge relay ON operation is achieved by maintaining the precharge relay in the ON state when the vehicle is started. Since the precharge relay ON operation is performed when the vehicle is started, the precharge 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 the above (1) or (2), it is preferable that the pre-charge relay ON operation is realized after the control unit detects a vehicle abnormal signal. Since the pre-charge relay that is turned ON at the start of the vehicle can be turned OFF once and the pre-charge relay ON operation can be executed when a vehicle abnormal signal is detected, there is no need to keep the pre-charge relay ON all the time, and the power consumption can be suppressed.

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

[0020] According to the current circuit interruption method of the present disclosure, by the control unit performing the pre-charge relay ON operation, the one-side main relay OFF operation, and the final OFF operation, an operation similar to the circuit interruption operation described in the aspect (1) above can be executed, and an effect similar to the aspect (1) above can be exerted.

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

[0022] <Embodiment 1> Hereinafter, the current circuit interruption system 10 of Embodiment 1 of this 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 loads, the inverter 16 and motor 18, and a pair of main relays 22, 22 (one side main relay, the + side main relay 22a, and the other side main relay, the - side main relay 22b) connected to each power line 20a and 20b, respectively. The current circuit 12 also includes a precharge circuit 28 connected in parallel to one of the main relays 22 (in Embodiment 1, the + side main relay 22a), which includes a precharge resistor 24 and a precharge 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 also connected to the inverter 16. In other words, 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, 22b is not limited, but in Embodiment 1, known mechanical relays (contact relays) are used as each main relay 22a, 22b. Note that each main relay 22a, 22b may be a semiconductor relay (non-contact relay). Such relays generally have a certain degree of interruption and short-circuit performance. Here, interruption performance refers to the ability to interrupt current up to a certain magnitude when an interruption signal (OFF signal) is received from an external source (e.g., the control unit 30), that is, the performance necessary to more reliably interrupt the current. If a current exceeding 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 capabilities, and relays specialized in interruption capabilities 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 perform 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 it ON, and a one-side main relay OFF operation 44, which follows the precharge relay ON operation 42 and sends an OFF signal to one of the main relays 22 (+side main relay 22a) connected in parallel to the precharge circuit 28 to turn it OFF. Furthermore, the circuit disconnection operation 11 includes a final OFF operation 46, which follows the one-side main relay OFF operation 44 and 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 it OFF. In particular, in Embodiment 1, the precharge relay ON operation 42 is achieved by maintaining the state in which the precharge relay 26 is ON 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] <Method for interrupting current circuits> The current interruption method according to this disclosure will be described below, with particular use of Figure 2. Specifically, the current 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 representing 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 precharge relay 26, the +-side main relay 22a, and the --side 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 --side main relay 22b, causing it to turn ON. If the +-side main relay 22a were to be turned ON in this state to charge the capacitor 36, an extremely large inrush current would flow instantaneously, potentially damaging the main relays 22a and 22b. To avoid this problem, a precharge circuit 28 is provided. That is, with the +-side main relay 22a remaining in the OFF state, the control unit 30 sends an ON signal to the precharge relay 26, performing a precharge relay ON operation 42 to turn the precharge relay 26 ON. This allows the capacitor 36 to be charged by a relatively low current value that has passed through the precharge 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 precharge relay 26 remains ON, thereby turning the +side main relay 22a ON. 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 precharge relay 26, the +side main relay 22a, and the -side main relay 22b are all ON. Even when both the precharge relay 26 and the +side main relay 22a are ON, the precharge circuit 28 is equipped with a precharge resistor 24, so almost no current flows through the precharge 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 a 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 remains 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 the 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 safely turn off the negative main relay 22b. 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 of interrupting current circuits. Conventionally, as shown in Figure 3, when the +-side main relay was in the ON state and power could be supplied through the +-side power line, the pre-charge relay was turned OFF, and the OFF state of the pre-charge relay was maintained under normal conditions. In this state, if a malfunction 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 current 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 performs 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, when 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 precharge relay ON operation 42 is achieved by maintaining the precharge relay 26 in the ON state when the vehicle is started. In other words, in electric vehicles and hybrid vehicles, the precharge relay 26 is turned ON when the capacitor 36 is charged when the vehicle is started. By maintaining this state, in the event of a vehicle malfunction such as an accident, the current circuit 12 can be quickly interrupted by the one-side main relay OFF operation 44 and the final OFF operation 46 without damaging the main relays 22a and 22b.

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

[0044] <Circuit break operation 50> In Embodiment 1, the precharge relay ON operation 42 was performed when the vehicle was started, and thereafter the ON state of the precharge relay 26 was maintained until the final OFF operation 46. However, in Embodiment 2, the precharge relay ON operation 42 is performed after the control unit 30 detects a vehicle abnormality signal.

[0045] Specifically, as mentioned above, the pre-charge relay 26 is turned ON when charging the capacitor 36 during vehicle startup in order to prevent inrush current. After the capacitor 36 has been charged to a certain extent and the +-side main relay 22a is turned ON, the control unit 30 sends an OFF signal to the pre-charge relay 26 to turn it OFF. In other words, in Embodiment 2, during normal operation 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] 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 performs a pre-charge relay ON operation 42, which sends an ON signal to the pre-charge relay 26 to turn the pre-charge relay 26 ON. After that, it is the same as in Embodiment 1, and the control unit 30 performs a one-side main relay OFF operation 44, which sends an OFF signal to the + side main relay 22a to turn the + side main relay 22a OFF. Subsequently, from the above state, the control unit 30 performs a final OFF operation 46, which sends an OFF signal to the pre-charge relay 26 to turn the pre-charge relay 26 OFF. As a result, the current circuit 12 is completely shut off, and the control unit 30 can send an OFF signal to the - side main relay 22b, thereby safely turning the - side main relay 22b OFF as well. As a result, after a vehicle malfunction occurs, the pre-charge relay 26, the positive-side main relay 22a, and the negative-side main relay 22b are all set to the OFF state.

[0047] Even when the circuit interruption operation 50 of Embodiment 2 is adopted, the state after a vehicle malfunction is substantially the same as in Embodiment 1, and therefore the same effects as in Embodiment 1 are achieved. In particular, in Embodiment 2, when the + side main relay 22a is turned ON and normal vehicle driving begins, the pre-charge relay 26 is turned OFF and remains OFF until a vehicle malfunction occurs. As a result, there is no need to keep the pre-charge relay 26 ON during normal operation, and power consumption can be reduced compared to Embodiment 1.

[0048] <Variation> While Embodiments 1 and 2 have been described in detail above as specific examples of the present disclosure, the present disclosure is not limited by these specific descriptions. Modifications, improvements, etc., to the extent that they can achieve the objectives of the present disclosure are included in the present disclosure. For example, the following modifications of 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 - side main relay 22b was turned ON first, and then the pre-charge relay 26 was turned ON. However, the invention is not limited to this embodiment, and the pre-charge relay may be turned ON first, and then the - side main relay may be turned ON.

[0050] (2) In 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 the one-side main relay OFF operation performed after a vehicle malfunction occurs.

[0051] (3) In embodiments 1 and 2, the precharge relay 26 was turned OFF by the final OFF operation 46, but the negative main relay may be turned OFF first, and then the precharge 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 precharge 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 precharge relay is not required, and the functions of each main relay and the precharge relay can be divided, so it is preferable to turn the precharge relay OFF with the final OFF operation. [Explanation of Symbols]

[0052] 10 Current Circuit Interruption System 11 Circuit interruption operation (Embodiment 1) 12 Current circuit 14 batteries 16 Inverters 18 Motors 20 Power Lines 20A + side power line 20b - Side power line 22 Main Relay 22a + side main relay (main relay on one side) 22b - Main relay on one side (main relay on the other side) 24 Precharge resistors 26 Pre-charge relay 28 Precharge Circuit 30 Control Unit 32 Current Sensor 34 fuses 36 Capacitors 38 Electrical junction box 42 Pre-charge relay ON operation 44. One-sided main relay OFF operation 46 Final OFF operation 50 Circuit break operation (Embodiment 2)

Claims

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. The current circuit comprises a pair of main relays and a control unit that sends ON / OFF signals to the precharge relay, The control unit is configured to perform a circuit interruption operation. Current circuit interruption system, wherein the circuit interruption operation includes 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, after the precharge relay ON operation, involves sending an OFF signal to one of the main relays connected in parallel to the precharge circuit to turn the one of the main relays OFF; and a final OFF operation, which, after the one-side main relay OFF operation, 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.

2. The current circuit includes a fuse connected to the power line, The current circuit interruption system according to claim 1, wherein 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 the ON state when the vehicle is started.

4. The current circuit interruption system according to claim 1 or 2, wherein the pre-charge 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 connected to each of the pair of power lines; and 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, wherein the pair of main relays and the precharge relay are connected to a control unit, The control unit performs a pre-charge relay ON operation, which involves sending an ON signal to the pre-charge relay to turn on the pre-charge relay, After the precharge relay ON operation, the precharge circuit sends an OFF signal to one of the main relays connected in parallel, thereby turning off one of the main relays, in a one-side main relay OFF operation. After the aforementioned OFF operation of one main relay, a final OFF operation is performed in which an OFF signal is sent to at least one of the precharge relay and the other main relay to turn OFF the precharge relay and the other main relay. A method for interrupting an electric current circuit.

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