Wire protection devices and vehicle-mounted systems

Abstract

To provide an electric wire protection device and an on-vehicle system, capable of appropriately protecting an electric wire from overheating.SOLUTION: An electric wire protection device 10 comprises a current detection unit 12, a voltage detection unit 13, and a power supply controller 18. The current detection unit 12 detects a current value of an electric wire 8 connecting a power supply device 4 to a load 6, as a detection current value A. The voltage detection unit 13 detects a voltage value at a first voltage detection point 8U provided between the power supply device 4 and the electric wire 8, as a first detection voltage value VU. The voltage detection unit 13 detects a voltage value at a second voltage detection point 8D provided between the electric wire 8 and the load 6, as a second detection voltage value VD. The power supply controller 18 calculates a resistance value of the electric wire 8 as a calculated resistance value RC on the basis of the detection current value A, the first detection voltage value VU, and the second detection voltage value VD and, on the basis of the calculated resistance value RC, restricts power supply to be performed via the electric wire 8.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in the present application relates to a wire protection device and an in-vehicle system. [Background technology]

[0002] Patent Document 1 describes an apparatus for restoring power supply to a load after the power supply to the load is interrupted. The apparatus described in Patent Document 1 includes an electric current path protection circuit. The electric current path protection circuit estimates the temperature of the electric current path based on the heat generation and heat dissipation of the electric current path. The electric current path protection circuit prohibits current flow when the estimated temperature reaches a predetermined upper limit value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5660358 Summary of the Invention [Problem to be solved by the invention]

[0004] However, generally, when estimating the temperature of an electric circuit from the electric current, an error in the estimated temperature is likely to occur. Furthermore, in the temperature estimation method described in Patent Document 1, the electric current is sampled at a predetermined cycle, and the latest electric current and the previously calculated electric wire temperature rise are substituted into a calculation formula to calculate the latest electric wire temperature rise. Therefore, the error in the calculated electric wire temperature rise accumulates with each calculation, and as a result, there is a possibility that the error in the estimated temperature will become large. If the error in the estimated temperature becomes large, the electric circuit cannot be adequately protected.

[0005] An object of the technique disclosed in the present application is to provide a wire protection device and an in-vehicle system that can appropriately protect wires from overheating. [Means for solving the problem]

[0006] According to a first feature, the wire protection device includes a current detection unit, a voltage detection unit, and a power supply controller. The current detection unit detects a current value of a wire connecting a power supply device to a load as a detected current value. The voltage detection unit detects a voltage value at a first voltage detection point provided between the power supply device and the wire as a first detected voltage value. The voltage detection unit detects a voltage value at a second voltage detection point provided between the wire and the load as a second detected voltage value. The power supply controller calculates a resistance value of the wire as a calculated resistance value based on the detected current value, the first detected voltage value, and the second detected voltage value, and limits power supply through the wire based on the calculated resistance value.

[0007] In the wire protection device according to the first aspect, the state of the wire can be grasped relatively accurately based on the calculated resistance value, and the wire can be appropriately protected from overheating.

[0008] According to a second feature, in the wire protection device according to the first feature, the power supply controller calculates the temperature of the wire as a calculated wire temperature based on a resistance-temperature characteristic indicating the relationship between the resistance value and temperature of the wire and the calculated resistance value, and limits the power supply through the wire based on the calculated wire temperature.

[0009] In the wire protection device according to the second aspect, the state of the wire can be grasped more accurately based on the calculated wire temperature, and the wire can be more appropriately protected from overheating.

[0010] According to a third feature, in the electric wire protection device according to the second feature, the power supply controller cuts off the power supply through the electric wire when the calculated electric wire temperature exceeds a temperature threshold value. In the wire protection device according to the third aspect, the wire can be more appropriately protected from overheating.

[0011] According to a fourth feature, in the wire protection device according to the second or third feature, the power supply controller allows power supply through the wire when the calculated wire temperature is equal to or lower than a temperature threshold value.

[0012] In the wire protection device according to the fourth aspect, the wire can be more appropriately protected from overheating while still supplying power through the wire.

[0013] According to a fifth feature, in the wire protection device according to any one of the second to fourth features, the power supply controller includes a memory that stores the resistance-temperature characteristic.

[0014] In the wire protection device according to the fifth feature, by storing the resistance-temperature characteristics corresponding to the wire in the memory, the wire can be more appropriately protected from overheating.

[0015] According to a sixth feature, in the wire protection device according to any one of the first to fifth features, The power supply controller calculates the calculated resistance value based on a resistance value calculation formula that indicates the relationship between the detected current value, the first detected voltage value, and the second detected voltage value.

[0016] In the wire protection device according to the sixth aspect, the resistance value of the wire can be more appropriately calculated by using the resistance value calculation formula, and the wire can be more appropriately protected from overheating.

[0017] According to a seventh feature, in the wire protection device related to the sixth feature, the power supply controller corrects an error in the resistance value calculation formula based on the first detected voltage value and the second detected voltage value output from the voltage detection unit when the power supply via the wire is interrupted.

[0018] In the wire protection device according to the seventh feature, by using the first detected voltage value and the second detected voltage value when the power supply through the wire is cut off, the error in the resistance value calculation formula can be appropriately corrected, and the wire can be more appropriately protected from overheating.

[0019] According to an eighth feature, in the wire protection device according to the sixth or seventh feature, the power supply controller corrects an error in the resistance value calculation formula based on a plurality of different detected current values ​​output from the current detection unit at a plurality of different detection timings, a plurality of different first detected voltage values ​​output from the voltage detection unit at a plurality of different detection timings, and a plurality of different second detected voltage values ​​output from the voltage detection unit at a plurality of different detection timings.

[0020] In the wire protection device according to the eighth aspect, the error in the resistance calculation formula can be appropriately corrected, and the wire can be more appropriately protected from overheating.

[0021] According to a ninth feature, in the wire protection device related to the eighth feature, the power supply controller corrects an error in the resistance value calculation formula based on a plurality of different detected current values ​​output from the current detection unit at a plurality of different detection timings in a first judgment period in which the detected current value is equal to or less than a reference current value, a plurality of different first detected voltage values ​​output from the voltage detection unit at a plurality of different detection timings in the first judgment period, and a plurality of different second detected voltage values ​​output from the voltage detection unit at a plurality of different detection timings in the first judgment period.

[0022] In the wire protection device according to the ninth feature, when the detected current value is equal to or less than the reference current value, the temperature of the wire is relatively low, and therefore the accuracy of the resistance value calculation formula tends to be relatively less affected by the wire temperature. Therefore, by correcting the error in the resistance value calculation formula based on the multiple different detected current values, the multiple different first detected voltage values, and the multiple different second detected voltage values ​​in the first determination period, the error in the resistance value calculation formula can be more appropriately corrected.

[0023] According to a tenth feature, in the wire protection device related to the ninth feature, the power supply controller corrects an error in the resistance value calculation formula based on a plurality of different detected current values ​​output from the current detection unit at a plurality of different detection timings during a first judgment period in which the detected current value is equal to or less than the reference current value and during a second judgment period from the start of the vehicle until a predetermined time has elapsed, a plurality of different first detected voltage values ​​output from the voltage detection unit at a plurality of different detection timings during the first judgment period and the second judgment period, and a plurality of different second detected voltage values ​​output from the voltage detection unit at a plurality of different detection timings during the first judgment period and the second judgment period.

[0024] In the wire protection device according to the tenth feature, the temperature of the wire is relatively low until a predetermined time has elapsed since the start of the vehicle, so that the accuracy of the resistance value calculation formula is less susceptible to the influence of the wire temperature. Therefore, by correcting the error of the resistance value calculation formula based on the multiple different detected current values, the multiple different first detected voltage values, and the multiple different second detected voltage values ​​in the first judgment period and the second judgment period, the error of the resistance value calculation formula can be more appropriately corrected.

[0025] According to an eleventh feature, in the wire protection device according to the tenth feature, the second determination period includes an inrush current period in which the current detection unit detects an inrush current value, and a steady current period in which the current detection unit detects a steady current value after the inrush current period. The plurality of different detected current values ​​includes an inrush current value and a steady current value. The plurality of different first detected voltage values ​​includes a first inrush voltage value and a first steady voltage value corresponding to the inrush current value and the steady current value, respectively. The plurality of different second detected voltage values ​​includes a second inrush voltage value and a second steady voltage value corresponding to the inrush current value and the steady current value, respectively. The power supply controller corrects an error in the resistance value calculation formula based on the inrush current value, the steady current value, the first inrush voltage value, the first steady voltage value, the second inrush voltage value, and the second steady voltage value.

[0026] In the wire protection device according to the eleventh feature, since the difference between the inrush current value and the steady-state current value is relatively large, the error in the resistance value calculation formula can be corrected based on a wide range of data.

[0027] According to a twelfth feature, the wire protection device according to the tenth or eleventh feature further includes a temperature sensor that detects an environmental temperature of the wire as a detected environmental temperature. The power supply controller corrects an error in the resistance value calculation formula based on the plurality of different detected current values, the plurality of different first detected voltage values, the plurality of different second detected voltage values, and the detected environmental temperature output from the temperature sensor during the second determination period.

[0028] In the wire protection device according to the twelfth feature, the error in the resistance calculation formula can be more appropriately corrected by taking into account the environmental temperature of the wire.

[0029] According to a thirteenth feature, the wire protection device according to any one of the eighth to twelfth features further includes a temperature sensor that detects an environmental temperature of the wire as a detected environmental temperature. The power supply controller corrects an error in the resistance value calculation formula based on the plurality of different detected current values, the plurality of different first detected voltage values, the plurality of different second detected voltage values, and the detected environmental temperature.

[0030] In the wire protection device according to the thirteenth feature, the error in the resistance calculation formula can be more appropriately corrected by taking into account the environmental temperature of the wire.

[0031] According to a 14th feature, in a wire protection device relating to any one of the 1st to 13th features, the voltage detection unit includes a first voltage detection unit that detects a voltage value at a first voltage detection point as a first detected voltage value, and a second voltage detection unit that detects a voltage value at a second voltage detection point as a second detected voltage value.

[0032] In the wire protection device of the fourteenth feature, even if the first voltage detection point and the second voltage detection point are separated from each other, the first voltage detection unit and the second voltage detection unit can detect the voltage values ​​at the first voltage detection point and the second voltage detection point.

[0033] According to a fifteenth feature, in the wire protection device according to the fourteenth feature, the first voltage detection unit is connected to a first voltage detection point arranged on a voltage line provided between the power supply device and the load and a first reference point arranged on a ground line provided between the power supply device and the load and serving as a reference for a first detected voltage value, and the second voltage detection unit is connected to a second voltage detection point arranged on the voltage line and a second reference point arranged on the ground line and serving as a reference for a second detected voltage value.

[0034] In the wire protection device according to the fifteenth feature, the first voltage detection unit and the second voltage detection unit can accurately detect the voltage values ​​at the first voltage detection point and the second voltage detection point.

[0035] According to a sixteenth feature, in the wire protection device according to the fifteenth feature, the second reference point is provided at a position on the ground line different from a position of the first reference point.

[0036] In the wire protection device according to the sixteenth feature, the degree of freedom in arranging the first voltage detection unit and the second voltage detection unit can be increased.

[0037] According to a 17th feature, in the wire protection device related to the 16th feature, the second voltage detection unit is connected to a line connecting the first voltage detection unit and the first reference point, and corrects the second detected voltage value based on the potential difference between the first reference point and the second reference point.

[0038] In the wire protection device according to the seventeenth feature, the degree of freedom in arranging the first voltage detection unit and the second voltage detection unit can be increased, while the detection accuracy of the second voltage detection unit can be improved.

[0039] According to an eighteenth feature, in the wire protection device according to the fifteenth feature, the second reference point is provided on a line connecting the first voltage detection unit and the first reference point.

[0040] In the wire protection device according to the eighteenth feature, the detection accuracy of the second voltage detection section can be improved.

[0041] According to a nineteenth feature, in the wire protection device according to the eighteenth feature, the second reference point is provided at the same position as the first reference point.

[0042] In the wire protection device according to the nineteenth aspect, the detection accuracy of the second voltage detection section can be further improved.

[0043] According to a twentieth feature, in the wire protection device according to any one of the fourteenth to nineteenth features, the first voltage detection section and the second voltage detection section are configured as an integrated unit.

[0044] The wire protection device according to the twentieth feature can more appropriately protect the wires from overheating while simplifying the structure.

[0045] According to a twenty-first feature, the wire protection device according to any one of the fourteenth to nineteenth features further includes a first unit and a second unit disposed at a position spaced apart from the first unit. The first unit includes a first voltage detection unit. The second unit includes a second voltage detection unit.

[0046] In the wire protection device according to the twenty-first feature, the first voltage detection unit and the second voltage detection unit are provided as separate units, so that the wire protection device can be applied to various arrangements of power sources and loads.

[0047] According to a twenty-second feature, an in-vehicle system includes a power supply device, a load, an electric wire, and a wire protection device according to any one of the first to twenty-first features. The wire protection device is electrically connected to the power supply device. The wire protection device is electrically connected to the load. No other device is electrically connected between the power supply device and the wire protection device. No other device is electrically connected between the wire protection device and the load.

[0048] In the in-vehicle system according to the twenty-second feature, no other devices are electrically connected between the power supply device and the wire protection device, and no other devices are electrically connected between the wire protection device and the load. That is, the wire protection device is disposed on a dedicated line between the power supply device and the load. Therefore, at least one of the detected current value, the first detected voltage value, and the second detected voltage value is less susceptible to the influence of the current supplied to the other load, and the detection accuracy of at least one of the detected current value, the first detected voltage value, and the second detected voltage value can be improved. For example, by applying the wire protection device to a dedicated line, the fluctuation of the ground potential is included in the detection signal rather than in the error. Therefore, the detection signal becomes larger, and the detection accuracy is improved. Effect of the Invention

[0049] According to the technology disclosed in the present application, it is possible to provide a wire protection device and an in-vehicle system that can appropriately protect wires from overheating. [Brief description of the drawings]

[0050] [Figure 1] FIG. 1 is a schematic block diagram of a vehicle including a wire protection device according to an embodiment. [Diagram 2] FIG. 2 shows an example of a graph of resistance-temperature characteristics used in the wire protection device shown in FIG. [Diagram 3] FIG. 3 is a schematic block diagram of a vehicle including a wire protection device according to a first modified example. [Figure 4] FIG. 4 is a schematic block diagram of a vehicle including a wire protection device according to the second modification. [Diagram 5] FIG. 5 is a schematic block diagram of a vehicle including a wire protection device according to the third modified example. [Figure 6] FIG. 6 shows an example of a graph of a resistance value calculation formula used in the wire protection device shown in FIG. [Figure 7] FIG. 7 shows an example of a timing chart of the wire protection device shown in FIG. [Figure 8] FIG. 8 shows an example of a timing chart of the wire protection device shown in FIG. [Figure 9] FIG. 9 shows an example of a graph of a resistance value calculation formula used in the wire protection device shown in FIG. [Figure 10] FIG. 10 shows an example of a flowchart of the operation of the wire protection device shown in FIG. [Figure 11] FIG. 11 shows an example of a flowchart of the operation of the wire protection device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, the same reference numerals indicate corresponding or identical components.

[0052] As shown in Fig. 1, the vehicle 2 includes an on-board system 3. The on-board system 3 includes a power supply device 4, a load 6, an electric wire 8, and an electric wire protection device 10. Examples of the vehicle 2 include automobiles. Examples of the automobiles include automobiles equipped with an engine (internal combustion engine) as a power source, hybrid vehicles equipped with an engine and a vehicle drive motor as power sources, and electric vehicles or fuel cell vehicles equipped with a vehicle drive motor as a power source. However, the vehicle 2 is not limited to the above vehicles.

[0053] The load 6 is electrically connected to the power supply device 4 via an electric wire 8 and an electric wire protection device 10. The power supply device 4 supplies power (electricity) to the load 6 via the electric wire 8 and the electric wire protection device 10. To protect the electric wire 8, the electric wire protection device 10 limits the power supply between the power supply device 4 and the load 6 depending on the condition of the electric wire 8.

[0054] The loads 6 are operated by electricity supplied from the power supply device 4. Examples of the loads 6 include an electronic control unit (ECU), a light, a heater, an audio device, a sensor, and a camera. The power supply device 4 may be connected to a plurality of loads 6. The loads 6 may also be referred to as in-vehicle devices 6.

[0055] The power supply device 4 includes a battery and a power supply circuit. The power supply circuit converts a voltage (e.g., 12 V) supplied from the battery into a predetermined control voltage (e.g., 3 V or 5 V). The power supply device 4 is electrically connected to the load 6 via an electric wire 8 and an electric wire protection device 10. The power supply device 4 supplies the control voltage to the load 6 via the electric wire 8 and the electric wire protection device 10. The power supply device 4 is electrically connected to a start operation unit 2A of the vehicle 2. The start operation unit 2A is configured to receive a start operation by a user to start the vehicle 2. The start operation unit 2A is configured to receive a stop operation by a user to stop the system of the vehicle 2.

[0056] The start operation unit 2A includes, for example, at least one of an engine start key and a start button. Examples of the user's start operation include an operation in which the user turns the engine start key of the start operation unit 2A to the start side, and an operation in which the user presses the start button of the start operation unit 2A. Examples of the user's stop operation include an operation in which the user turns the engine start key of the start operation unit 2A to the stop side, and an operation in which the user presses the start button of the start operation unit 2A again. When the start operation unit 2A receives the user's start operation, it outputs a start signal. When the start operation unit 2A receives the user's stop operation, it outputs a stop signal. When the power supply device 4 receives the start signal from the start operation unit 2A, it starts supplying power to the wire protection device 10. When the power supply device 4 receives the stop signal from the start operation unit 2A, it stops supplying power to the wire protection device 10.

[0057] The wire protection device 10 is electrically connected to the power supply device 4. The wire protection device 10 is electrically connected to the load 6. In this embodiment, no other device is electrically connected between the power supply device 4 and the wire protection device 10. No other device is electrically connected between the wire protection device 10 and the load 6. That is, the wire protection device 10 is disposed on a dedicated line between the power supply device 4 and the load 6. However, other device may be electrically connected between the wire protection device 10 and the power supply device 4. Other device may be electrically connected between the wire protection device 10 and the load 6.

[0058] The wire protection device 10 includes a current detection unit 12 and a voltage detection unit 13. The current detection unit 12 detects a current value in a wire 8 connecting the power supply device 4 to a load 6 as a detected current value A. The voltage detection unit 13 detects a voltage value at a first voltage detection point 8U provided between the power supply device 4 and the wire 8 as a first detected voltage value VU. The voltage detection unit 13 detects a voltage value at a second voltage detection point 8D provided between the wire 8 and the load 6 as a second detected voltage value VU.

[0059] In this embodiment, the voltage detection unit 13 includes a first voltage detection unit 14 and a second voltage detection unit 16. The first voltage detection unit 14 detects the voltage value at the first voltage detection point 8U as a first detected voltage value VU. The second voltage detection unit 16 detects the voltage value at the second voltage detection point 8D as a second detected voltage value VD. The first voltage detection point 8U may also be referred to as an upstream voltage detection point 8U. The second voltage detection point 8D may also be referred to as a downstream voltage detection point 8D. The first voltage detection unit 14 may also be referred to as an upstream voltage detection unit 14. The second voltage detection unit 16 may also be referred to as a downstream voltage detection unit 16. The first detected voltage value VU may also be referred to as a detected upstream voltage value VU. The second detected voltage value VD may also be referred to as a detected downstream voltage value VD.

[0060] The wire protection device 10 includes a power supply controller 18. The power supply controller 18 limits the power supply through the wire 8 based on the detected current value A, the first detected voltage value VU, and the second detected voltage value VD. The power supply controller 18 calculates the resistance value of the wire 8 as a calculated resistance value RC based on the detected current value A, the first detected voltage value VU, and the second detected voltage value VD, and limits the power supply through the wire 8 based on the calculated resistance value RC. In this embodiment, the power supply controller 18 calculates the temperature of the wire 8 as a calculated wire temperature TC based on a resistance-temperature characteristic D1 (see FIG. 2, for example) indicating the relationship between the resistance value and temperature of the wire 8 and the calculated resistance value RC. The power supply controller 18 limits the power supply through the wire 8 based on the calculated wire temperature TC. However, the power supply controller 18 may be configured to limit the power supply through the wire 8 directly using the calculated resistance value RC without using the resistance-temperature characteristic D1. The power supply controller 18 includes a memory 18M. The memory 18M stores the resistance-temperature characteristic D1.

[0061] The wire protection device 10 includes a first unit 20 and a second unit 22. The second unit 22 is disposed at a position away from the first unit 20. The first unit 20 is disposed upstream of the second unit 22. The first unit 20 includes a current detection unit 12, a first voltage detection unit 14, and a power supply controller 18. The second unit 22 includes a second voltage detection unit 16. The first unit 20 may also be referred to as an upstream unit 20. The second unit 22 may also be referred to as a downstream unit 22. At least one of the current detection unit 12 and the power supply controller 18 may be provided in the second unit 20.

[0062] In this application, in the direction of current flow from positive (higher voltage side) to negative (lower voltage side), the positive side is referred to as "upstream" or "upstream side", and the negative side is referred to as "downstream" or "downstream side".

[0063] The power supply controller 18 includes a switch circuit 24, a processor 18P, a circuit board 18C, and a bus 18B. The switch circuit 24 is provided between the power supply device 4 and the load 6, and allows and blocks the power supply from the power supply device 4 to the load 6. The switch circuit 24 includes, for example, a field effect transistor (FET) 24F and a gate driver 24G.

[0064] The FET 24F is, for example, a metal oxide semiconductor (MOS) FET. More specifically, the FET 24F is an N-channel MOSFET. However, the FET 24F is not limited to an N-channel MOSFET. The FET 24F includes a drain electrode D, a source electrode S, and a gate electrode G. The drain electrode D is electrically connected to the power supply 4 via an electric wire 8. The source electrode S is electrically connected to the load 6 via an electric wire 8. The gate electrode G is electrically connected to the gate driver 24G.

[0065] When a gate voltage higher than the threshold is applied to the gate electrode G, the FET 24F allows a current to flow from the source electrode S to the drain electrode D. When a gate voltage higher than the threshold is not applied to the gate electrode G, the FET 24F blocks a current from flowing from the source electrode S to the drain electrode D.

[0066] The gate driver 24G is electrically connected to the processor 18P via the circuit board 18C and the bus 18B. The gate driver 24G supplies a gate voltage higher than a threshold to the gate electrode G of the FET 24F based on a command from the processor 18P.

[0067] The processor 18P includes, for example, a central processing unit (CPU) and / or a micro processing unit (MPU). The memory 18M includes, for example, a volatile and / or non-volatile memory. An example of the volatile memory includes a random access memory (RAM). An example of the non-volatile memory includes a read only memory (ROM) and an electrically erasable programmable ROM (EEPROM).

[0068] The memory 18M of the power supply controller 18 stores information such as a control program and firmware for implementing the control algorithm of the power supply controller 18. The processor 18P implements the control algorithm of the power supply controller 18 by reading and executing the control program stored in the memory 18M. The configuration of the power supply controller 18 is not limited to the processor 18P and the memory 18M. The configuration of the power supply controller 18 can be implemented by hardware only, software only, or a combination of hardware and software.

[0069] The switch circuit 24, the processor 18P, and the memory 18M are electrically mounted on a circuit board 18C. The switch circuit 24, the processor 18P, and the memory 18M are electrically connected to each other via the circuit board 18C and the bus 18B.

[0070] The current detection unit 12 and the first voltage detection unit 14 are electrically connected to the power supply controller 18. The current detection unit 12 and the first voltage detection unit 14 are electrically mounted on a circuit board 18C. The current detection unit 12 and the first voltage detection unit 14 are electrically connected to the processor 18P and the memory 18M via the circuit board 18C and the bus 18B. The detected current value A output from the current detection unit 12 is input to the power supply controller 18 via the circuit board 18C and the bus 18B. The first detected voltage value VU output from the first voltage detection unit 14 is input to the power supply controller 18 via the circuit board 18C and the bus 18B.

[0071] The wire protection device 10 further includes a temperature sensor 26 that detects the environmental temperature of the wire 8 as a detected environmental temperature TE. The temperature sensor 26 is provided in the first unit 20. The temperature sensor 26 is electrically connected to the power supply controller 18. The temperature sensor 26 is electrically connected to the processor 18P and the memory 18M via the circuit board 18C and the bus 18B. The detected environmental temperature TE output from the temperature sensor 26 is input to the power supply controller 18 via the circuit board 18C and the bus 18B. The temperature sensor 26 may be provided in a location other than the first unit 20. The temperature sensor 26 may be omitted from the wire protection device 10.

[0072] The second unit 22 includes a circuit board 22C. The second voltage detection unit 16 is electrically mounted on the circuit board 22C. The wire protection device 10 includes an electric cable 28. The second unit 22 is electrically connected to the first unit 20 via the electric cable 28. The second voltage detection unit 16 is electrically connected to the processor 18P and the memory 18M via the circuit board 22C, the electric cable 28, the bus 18B, and the circuit board 18C. The second detected voltage value VD output from the second voltage detection unit 16 is input to the power supply controller 18 via the circuit board 22C and the electric cable 28.

[0073] The vehicle 2 further includes electric wires 81, 82, 84, and 85. The power supply device 4 is electrically connected to the first unit 20 via the electric wire 81. The electric wire 82 is provided in the first unit 20. The first unit 20 is electrically connected to the second unit 22 via the electric wire 8. The electric wire 84 is provided in the second unit 22. The second unit 22 is electrically connected to the load 6 via the electric wire 85.

[0074] The electric wire 81 includes electric connectors 81A and 81B, a voltage line VL1, and a ground line GL1. The electric connector 81A is removably connected to the power supply device 4. The electric connector 81B is removably connected to the first unit 20 of the electric wire protection device 10. The electric connector 81A is connected to the electric connector 81B via the voltage line VL1 and the ground line GL1.

[0075] The electric wire 82 is provided in the first unit 20. The first voltage detection point 8U is provided in the first unit 20. The electric wire 82 includes electric connectors 82A and 82B, a voltage line VL2, and a ground line GL2. The electric connectors 82A and 82B are electrically connected to the circuit board 18C. The voltage line VL2 and the ground line GL2 are provided on the circuit board 18C. The electric connector 82A is connected to the electric connector 82B via the voltage line VL2 and the ground line GL2. The electric connector 81B of the electric wire 81 is detachably connected to the electric connector 82A of the electric wire 82. The voltage line VL2 is electrically connected to the voltage line VL1 via the electric connectors 81B and 82A. The ground line GL2 is electrically connected to the ground line GL1 via the electric connectors 81B and 82A. The voltage line VL2 and the ground line GL2 are electrically connected to the circuit board 18C so that power is supplied from the power supply device 4 to the power supply controller 18 regardless of the power supply from the power supply device 4 to the load 6. Therefore, while power is being supplied from the power supply device 4 to the wire protection device 10, the power supply controller 18 operates using the power supply from the power supply device 4.

[0076] The wire 8 includes electrical connectors 83A and 83B, a voltage line VL3, and a ground line GL3. The electrical connector 83A is connected to the electrical connector 83B via the voltage line VL3 and the ground line GL3. The electrical connector 83A is removably connected to the first unit 20 of the wire protection device 10. The electrical connector 83A of the wire 8 is removably connected to the electrical connector 82B of the wire 82. The voltage line VL3 is electrically connected to the voltage line VL2 via the electrical connectors 82B and 83A. The ground line GL3 is electrically connected to the ground line GL2 via the electrical connectors 82B and 83A. The electrical connector 83B is removably connected to the second unit 22 of the wire protection device 10.

[0077] The electric wire 84 is provided on the second unit 22. The second voltage detection point 8D is provided on the electric wire 84. The electric wire 84 includes electrical connectors 84A and 84B, a voltage line VL4, and a ground line GL4. The electrical connectors 84A and 84B are electrically connected to the circuit board 18C. The voltage line VL4 and the ground line GL4 are provided on the circuit board 18C. The electrical connector 84A is connected to the electrical connector 84B via the voltage line VL4 and the ground line GL4. The electrical connector 83B of the electric wire 8 is detachably connected to the electrical connector 84A of the electric wire 84. The voltage line VL4 is electrically connected to the voltage line VL3 via the electrical connectors 83B and 84A. The ground line GL4 is electrically connected to the ground line GL3 via the electrical connectors 83B and 84A.

[0078] The electric wire 85 includes electrical connectors 85A and 85B, a voltage line VL5, and a ground line GL5. The electrical connector 85A is connected to the electrical connector 85B via the voltage line VL5 and the ground line GL5. The electrical connector 85A is removably connected to the first unit 20 of the electric wire protection device 10. The electrical connector 85A of the electric wire 85 is removably connected to the electrical connector 84B of the electric wire 84. The voltage line VL5 is electrically connected to the voltage line VL4 via the electrical connectors 84B and 85A. The ground line GL5 is electrically connected to the ground line GL4 via the electrical connectors 84B and 85A. The electrical connector 85B is removably connected to the load 6.

[0079] The FET 24F of the switch circuit 24 is disposed on the voltage line VL2. The current detection unit 12 detects the value of the current flowing through the voltage line VL2 as a detected current value A. The first voltage detection unit 14 detects the voltage value applied between the voltage line VL2 and the ground line GL2 as a first detected voltage value VU. The second voltage detection unit 16 detects the voltage value applied between the voltage line VL4 and the ground line GL4 as a second detected voltage value VD.

[0080] The first voltage detection unit 14 is connected to a first voltage detection point 8U arranged on a voltage line VL2 provided between the power supply device 4 and the load 6, and a first reference point RP1 arranged on a ground line GL2 provided between the power supply device 4 and the load 6 and serving as a reference for the first detected voltage value VU. The second voltage detection unit 16 is connected to a second voltage detection point 8D arranged on a voltage line VL4, and a second reference point RP2 arranged on the ground line GL4 and serving as a reference for the second detected voltage value VD. In this embodiment, the second reference point RP2 is provided at a position different from the position of the first reference point RP1 on the ground line. The position of the first reference point RP1 is away from the position of the second reference point RP2. However, as shown in FIG. 3, the second reference point RP2 may be provided on a line connecting the first voltage detection unit 14 and the first reference point RP1. In the modified example shown in FIG. 3, the second reference point RP2 is provided at the same position as the position of the first reference point RP1. However, the second reference point RP2 may be provided at a position different from the position of the first reference point RP1 on the line connecting the first voltage detection unit 14 and the first reference point RP1. Also, as shown in FIG. 4, when the second reference point RP2 is provided at a position different from the position of the first reference point RP1 on the ground line, the second voltage detection unit 16 may be connected to the line connecting the first voltage detection unit 14 and the first reference point RP1. In this case, the second voltage detection unit 16 corrects the second detection voltage value VD based on the potential difference between the first reference point RP1 and the second reference point RP2. Furthermore, in this embodiment, the first voltage detection unit 14 and the second voltage detection unit 16 are provided in the first unit 20 and the second unit 22, respectively, but as shown in FIG. 5, the first voltage detection unit 14 and the second voltage detection unit 16 may be configured as an integrated unit.

[0081] 1 and 6, the power supply controller 18 calculates the calculated resistance value RC based on a resistance value calculation formula D2 that indicates the relationship between the detected current value A, the first detected voltage value VU, and the second detected voltage value VD. The memory 18M of the power supply controller 18 stores the resistance value calculation formula D2. The memory 18M stores the latest calculated resistance value RC.

[0082] For example, the current detection unit 12 outputs the detected current value A constantly or at a predetermined cycle. The first voltage detection unit 14 outputs the first detected voltage value VU constantly or at a predetermined cycle. The second voltage detection unit 16 outputs the second detected voltage value VD constantly or at a predetermined cycle. The power supply controller 18 stores the latest detected current value A, the latest first detected voltage value VU, and the latest second detected voltage value VD in the memory 18M. The power supply controller 18 calculates the calculated resistance value RC at a predetermined cycle based on the latest detected current value A, the latest first detected voltage value VU, the latest second detected voltage value VD, and the resistance value calculation formula D2. The power supply controller 18 calculates the temperature of the electric wire 8 as the calculated electric wire temperature TC at a predetermined cycle based on the resistance temperature characteristic D1 and the calculated resistance value RC. The memory 18M stores the latest calculated electric wire temperature TC.

[0083] 7, the power supply controller 18 allows power supply through the power wire 8 when the calculated power wire temperature TC is equal to or lower than the temperature threshold value T0. Specifically, when the calculated power wire temperature TC is equal to or lower than the temperature threshold value T0, the processor 18P of the power supply controller 18 transmits a current supply command to the gate driver 24G of the switch circuit 24. The gate driver 24G supplies a gate voltage to the FET 24F of the switch circuit 24 based on the current supply command. The supply of the gate voltage causes the FET 24F to allow power supply from the power supply device 4 to the load 6. As a result, power is supplied from the power supply device 4 to the load 6.

[0084] On the other hand, when the calculated electric wire temperature TC exceeds the temperature threshold value T0, the power supply controller 18 cuts off the power supply through the electric wire 8. When the calculated electric wire temperature TC exceeds the temperature threshold value T0, the processor 18P of the power supply controller 18 sends a power supply stop command to the gate driver 24G of the switch circuit 24. The gate driver 24G stops the supply of gate voltage to the FET 24F of the switch circuit 24 based on the power supply stop command. By stopping the supply of gate voltage, the FET 24F of the switch circuit 24 cuts off the power supply from the power supply device 4 to the load 6.

[0085] As shown in FIG. 6, for example, the relationship between the detected current value A, the first detected voltage value VU, the second detected voltage value VD, and the resistance value R is expressed by the following formula (1).

[0086] ΔV = VU - VD = A × R (1) However, when the resistance value R is constant, a voltage error ΔVE1 may occur when the detected current value A is zero, as shown in the following formula (2).

[0087] ΔV = VU - VD = A × R + ΔVE1 (2) By rearranging equation (2), we obtain the following equation (3).

[0088] R = (ΔV-ΔVE1) / A (3) The formulas (2) and (3) are referred to as resistance value calculation formula D2.

[0089] The power supply controller 18 corrects the error of the resistance value calculation formula D2 based on the first detected voltage value VU0 and the second detected voltage value VD0 output from the voltage detection unit 13 when the power supply through the electric wire 8 is interrupted. In this case, the voltage error ΔVE1 (=VU0-VD0) can be calculated by substituting zero, the first detected voltage value VU0, and the second detected voltage value VD0 into the detected current value A, the first detected voltage value VU, and the second detected voltage value VD of the resistance value calculation formula D2, respectively. This makes it possible to correct the voltage error ΔVE1 of the resistance value calculation formula D2. That is, it is possible to perform a zero point correction of the voltage detection unit 13 (in this embodiment, the first voltage detection unit 14 and the second voltage detection unit 16).

[0090] In addition, the power supply controller 18 corrects the error in the resistance value calculation formula D2 based on a plurality of different detected current values ​​A output from the current detection unit 12 at a plurality of different detection timings, a plurality of different first detected voltage values ​​VU output from the voltage detection unit 13 (in this embodiment, the first voltage detection unit 14) at a plurality of different detection timings, and a plurality of different second detected voltage values ​​VD output from the voltage detection unit 13 (in this embodiment, the second voltage detection unit 16) at a plurality of different detection timings.

[0091] For example, the power supply controller 18 corrects the voltage error ΔVE2 of the resistance value calculation formula D2 based on a plurality of different detected current values ​​A1 and A2 output from the current detection unit 12 at a plurality of different detection timings, a plurality of different first detected voltage values ​​VU1 and VU2, and a plurality of different second detected voltage values ​​VD1 and VD2. If the difference between the first detected voltage value VU1 and the second detected voltage value VD1 is ΔV1, the relationship between the difference ΔV1, the detected current value A1, and the resistance value R is expressed by the following formula (4).

[0092] R = (ΔV1 - ΔVE2) / A1 (4) If the difference between the first detected voltage value VU2 and the second detected voltage value VD2 is ΔV2, the relationship between the difference ΔV2, the detected current value A2, and the resistance value R is expressed by the following formula (5).

[0093] R = (ΔV2 - ΔVE2) / A2 (5) From equations (4) and (5), the voltage error ΔVE2 of equation (2) is expressed by the following equation (6).

[0094] ΔVE2=(ΔV2×A1-ΔV1×A2) / (A1-A2) (6) By using the voltage error ΔVE2 expressed by the formula (6), it is possible to correct the error in the resistance value calculation formula D2 expressed by the formula (2). That is, the power supply controller 18 can correct the voltage error ΔVE2 in the resistance value calculation formula D2 based on a plurality of different detected current values ​​A1 and A2, a plurality of different first detected voltage values ​​VU1 and VU2, and a plurality of different second detected voltage values ​​VD1 and VD2.

[0095] However, the above error correction is based on the premise that the resistance value R is constant, but the resistance value R in the resistance value calculation formula D2 of the electric wire 8 changes in response to a change in the temperature of the electric wire 8.

[0096] Therefore, the power supply controller 18 corrects the voltage error ΔVE2 during a period when the temperature of the electric wire 8 is assumed to be relatively low. A period when the detected current value A is relatively low may be considered as an example of a period when the temperature of the electric wire 8 is assumed to be relatively low.

[0097] For example, the power supply controller 18 corrects the error in the resistance value calculation formula D2 based on a plurality of different detected current values ​​A output from the current detection unit 12 at a plurality of different detection timings during the first judgment period P1 in which the detected current value A is equal to or less than the reference current value A0, a plurality of different first detected voltage values ​​VU output from the voltage detection unit 13 (in this embodiment, the first voltage detection unit 14) at a plurality of different detection timings during the first judgment period P1, and a plurality of different second detected voltage values ​​VD output from the voltage detection unit 13 (in this embodiment, the second voltage detection unit 16) at a plurality of different detection timings during the first judgment period P1.

[0098] Furthermore, a period during which the temperature of the electric wire 8 is assumed to be relatively low may be, for example, immediately after the start-up of the vehicle 2 (for example, a period from the start-up of the vehicle 2 until a predetermined time has elapsed). Here, the start-up of the vehicle 2 includes, for example, the start-up of the drive system of the vehicle 2 in response to a user's operation on the start-up operation unit 2A (for example, see FIG. 1). An example of the start-up of the drive system of the vehicle 2 includes the system of the vehicle 2 switching from an off state to a state in which the vehicle 2 is capable of running. More specifically, an example of the start-up of the drive system of the vehicle 2 includes the start-up of the engine of the vehicle 2, and the system of the vehicle 2 switching from an off state to a state in which power supply to the vehicle drive motor can begin.

[0099] As shown in FIG. 8, the power supply controller 18 corrects an error in the resistance value calculation formula D2 based on a plurality of different detected current values ​​A output from the current detection unit 12 at a plurality of different detection timings during a first judgment period P1 in which the detected current value A is equal to or less than the reference current value A0 and during a second judgment period P2 from the start of the vehicle 2 until a predetermined time has elapsed, a plurality of different first detected voltage values ​​VU output from the voltage detection unit 13 (in this embodiment, the first voltage detection unit 14) at a plurality of different detection timings during the first judgment period P1 and the second judgment period P2, and a plurality of different second detected voltage values ​​VD output from the voltage detection unit 13 (in this embodiment, the second voltage detection unit 16) at a plurality of different detection timings during the first judgment period P1 and the second judgment period P2.

[0100] Here, the second judgment period P2 includes an inrush current period P21 during which the current detection unit 12 detects the inrush current value, and a steady current period P22 during which the current detection unit 12 detects the steady current value after the inrush current period P21. The inrush current value is different from the steady current value. For example, the inrush current value has a peak, and the maximum value of the inrush current value is higher than the maximum value of the steady current value. Since the difference between the inrush current value and the steady current value is relatively large, the difference between the inrush voltage value corresponding to the inrush current value and the steady voltage value corresponding to the steady current value is also relatively large. It can be expected that the accuracy of the correction of the voltage error ΔVE2 will increase as the difference between the inrush current value and the steady current value increases.

[0101] Therefore, the power supply controller 18 corrects the error of the resistance value calculation formula D2 using the detected current value A, the first detected voltage value VU, and the second detected voltage value VD in the inrush current period P21 and the steady current period P22, respectively. Specifically, the multiple different detected current values ​​A include an inrush current value (e.g., A1) and a steady current value (e.g., A2). The multiple different first detected voltage values ​​VU include a first inrush voltage value (e.g., VU1) and a first steady voltage value (e.g., VD1) corresponding to the inrush current value A1 and the steady current value A2, respectively. The multiple different second detected voltage values ​​VD include a second inrush voltage value (e.g., VU2) and a second steady voltage value (e.g., VD2) corresponding to the inrush current value A1 and the steady current value A2, respectively. The power supply controller 18 corrects the error in the resistance value calculation formula D2 based on the inrush current value A1, the steady-state current value A2, the first inrush voltage value VU1, the first steady-state voltage value VD1, the second inrush voltage value VU2, and the second steady-state voltage value VD2. In this case, the above-mentioned formula (5) is used to correct the voltage error ΔVE2 in the resistance value calculation formula D2.

[0102] For example, the power supply controller 18 monitors the detected current value A, the first detected voltage value VU, and the second detected voltage value VD from the start of the vehicle 2 until the second determination period P2 has elapsed. The power supply controller 18 stores in the memory 18M the maximum value A1 of the detected current value A, the first detected voltage value VU1 corresponding to the maximum value A1 of the detected current value A, and the second detected voltage value VD1 corresponding to the maximum value A1 of the detected current value A. The maximum value A1 of the detected current value A is usually detected in the inrush current period P21.

[0103] Furthermore, after detecting the maximum value of the detected current value A, the power supply controller 18 stores in the memory 18M the minimum value A2 of the detected current value A, a first detected voltage value VU2 corresponding to the minimum value A2 of the detected current value A, and a second detected voltage value VD2 corresponding to the minimum value A2 of the detected current value A. The minimum value A2 of the detected current value A is usually detected in the steady current period P22.

[0104] After the second determination period P2 has elapsed, the power supply controller 18 calculates the voltage error ΔVE2 of the resistance value calculation formula D2 using the formula (5). In this way, the power supply controller 18 corrects the voltage error ΔVE2 of the resistance value calculation formula D2 immediately after the vehicle 2 is started.

[0105] Furthermore, the resistance value R in the resistance value calculation formula D2 of the electric wire 8 may be affected by the environmental temperature. Therefore, as shown in Fig. 6 and Fig. 9, the power supply controller 18 corrects the error of the resistance value calculation formula D2 based on the multiple different detected current values ​​A, the multiple different first detected voltage values ​​VU, the multiple different second detected voltage values ​​VD, and the detected environmental temperature TE. Specifically, the power supply controller 18 corrects the error of the resistance value calculation formula D2 based on the multiple different detected current values ​​A, the multiple different first detected voltage values ​​VU, the multiple different second detected voltage values ​​VD, and the detected environmental temperature TE output from the temperature sensor 26 during the second determination period P2.

[0106] For example, the power supply controller 18 stores a plurality of resistance value calculation formulas D2 in the memory 18M. The plurality of resistance value calculation formulas D2 include a resistance value calculation formula D21 corresponding to the detected environmental temperature TE1 and a resistance value calculation formula D22 corresponding to the detected environmental temperature TE2. The power supply controller 18 stores the resistance value calculation formulas D21 and D22 in the memory 18M in association with the detected environmental temperature TE. The detected environmental temperature TE1 is lower than the reference environmental temperature TE0. The detected environmental temperature TE2 is equal to or higher than the reference environmental temperature TE0. However, the plurality of resistance value calculation formulas D2 are not limited to the resistance value calculation formulas D21 and D22. The power supply controller 18 may store one resistance value calculation formula D2 in the memory 18M, or may store three or more resistance value calculation formulas D2 in the memory 18M.

[0107] As shown in FIG. 6, if the resistance value R of the resistance value calculation formula D21 corresponding to the detected environmental temperature TE1 is R1, the following formula (6) is stored as the resistance value calculation formula D21.

[0108] ΔV=A×R1+ΔVE2 (6) As shown in FIG. 9, if the resistance value R of the resistance value calculation formula D22 corresponding to the detected environmental temperature TE2 is R2, the following formula (7) is stored as the resistance value calculation formula D22.

[0109] ΔV=A×R2+ΔVE2 (7) As shown in FIG. 6 and FIG. 9, the correction of the voltage error ΔVE2 is performed on the resistance value calculation formula D21 in the case of the detected environmental temperature TE1, and on the resistance value calculation formula D22 in the case of the detected environmental temperature TE2. For example, after the vehicle 2 is started, the temperature sensor 26 starts detecting the environmental temperature. The power supply controller 18 selects the resistance value calculation formula D2 corresponding to the detected environmental temperature TE output from the temperature sensor 26. For example, the power supply controller 18 compares the detected environmental temperature TE with the reference environmental temperature TE0 at a predetermined period, and selects one of the resistance value calculation formulas D21 and D22 as the resistance value calculation formula D2 corresponding to the detected environmental temperature TE based on the comparison result. Note that the number of the resistance value calculation formulas D2 is not limited to two, the resistance value calculation formulas D21 and D22.

[0110] The operation of the wire protection device 10 will be described with reference to FIGS.

[0111] 10, after the vehicle 2 is started, power supply to the wire protection device 10 is started (steps S1 and S2). At this time, power supply to the load 6 is cut off by the wire protection device 10. In the wire protection device 10, detection of the current value A, the voltage value VU, the voltage value VD, and the environmental temperature TE is started by the current detection unit 12, the voltage detection unit 13 (in this embodiment, the first voltage detection unit 14 and the second voltage detection unit 16), and the temperature sensor 26 (step S3).

[0112] The detected current value A, the first detected voltage value VU, the second detected voltage value VD, and the detected environmental temperature TE output from the current detection unit 12, the first voltage detection unit 14, the second voltage detection unit 16, and the temperature sensor 26 are input to the power supply controller 18 at a predetermined cycle. The detected current value A, the first detected voltage value VU, the second detected voltage value VD, and the detected environmental temperature TE input to the power supply controller 18 at the same timing are stored in memory 18M of the power supply controller 18 in association with each other. The latest detected current value A, the latest first detected voltage value VU, the latest second detected voltage value VD, and the latest detected environmental temperature TE are stored in memory 18M of the power supply controller 18 in association with each other.

[0113] Before power supply to the load 6 is started, the voltage error ΔVE1 of the resistance value calculation formula D2 is corrected by the power supply controller 18 based on the first detected voltage value VU and the second detected voltage value VD (step S5). In this embodiment, the voltage error ΔVE1 of each of the multiple resistance value calculation formulas D2 (resistance value calculation formulas D21 and D22) is corrected by the power supply controller 18 based on the first detected voltage value VU and the second detected voltage value VD.

[0114] After the error correction of the resistance value calculation formula D2, the voltage line VL4 is connected by the switch circuit 24 of the power supply controller 18, and power supply to the load 6 is started (step S5). After the power supply to the load 6 is started, the maximum value of the inrush current value is determined by the power supply controller 18 during the inrush current period P21 (step S6). The first detection voltage value VU input to the power supply controller 18 at the same timing as the maximum value of the inrush current value is selected by the power supply controller 18 as the first detection voltage value VU corresponding to the maximum value of the inrush current value (step S7). Similarly, the second detection voltage value VD input to the power supply controller 18 at the same timing as the maximum value of the inrush current value is selected by the power supply controller 18 as the second detection voltage value VD corresponding to the maximum value of the inrush current value (step S8). The maximum value of the inrush current value, the first detection voltage value VU corresponding to the maximum value of the inrush current value, and the second detection voltage value VD corresponding to the maximum value of the inrush current value are stored in the memory 18M of the power supply controller 18.

[0115] After the inrush current period P21 has elapsed, the minimum value of the steady-state current value is determined by the power supply controller 18 during the steady-state current period P22 (step S9). The first detected voltage value VU input to the power supply controller 18 at the same timing as the minimum value of the steady-state current value is selected by the power supply controller 18 as the first detected voltage value VU corresponding to the minimum value of the steady-state current value (step S10). Similarly, the second detected voltage value VD input to the power supply controller 18 at the same timing as the minimum value of the steady-state current value is selected by the power supply controller 18 as the second detected voltage value VD corresponding to the minimum value of the steady-state current value (step S11). The minimum value of the steady-state current value, the first detected voltage value VU corresponding to the minimum value of the steady-state current value, and the second detected voltage value VD corresponding to the minimum value of the steady-state current value are stored in the memory 18M of the power supply controller 18.

[0116] 11, the power supply controller 18 selects a resistance value calculation formula D2 corresponding to the detected environmental temperature TE from a plurality of resistance value calculation formulas D2 (resistance value calculation formulas D21 and D22 in this embodiment) based on the detected environmental temperature TE (step S12). The power supply controller 18 determines whether the detected current value A is equal to or less than the reference current value A0 (step S13). If the detected current value A is equal to or less than the reference current value A0, the power supply controller 18 corrects the voltage error ΔVE2 of the resistance value calculation formula D2 based on the detected current value A, the first detected voltage value VU, and the second detected voltage value VD (steps S13 and S14). On the other hand, if the detected current value A exceeds the reference current value A0, the voltage error ΔVE2 of the resistance value calculation formula D2 is not corrected by the power supply controller 18 (step S13).

[0117] The power supply controller 18 calculates the resistance value RC based on the resistance value calculation formula D2, the detected current value A, the first detected voltage value VU, and the second detected voltage value VD (step S15). The power supply controller 18 calculates the temperature TC of the electric wire 8 based on the calculated resistance value RC and the resistance temperature characteristic D1 (step S16). If the calculated electric wire temperature TC exceeds the temperature threshold value T0, the power supply to the load 6 is cut off (step S17). If the calculated electric wire temperature TC is equal to or lower than the temperature threshold value T0, the power supply to the load 6 is not cut off, and the process returns to step S12. Steps S12 to S17 are repeated until the calculated electric wire temperature TC exceeds the temperature threshold value T0 or until the vehicle 2 is turned OFF.

[0118] In this manner, in the wire protection device 10, the power supply controller 18 calculates the resistance value of the wire 8 as the calculated resistance value RC based on the detected current value A, the first detected voltage value VU, and the second detected voltage value VD, and limits the power supply through the wire 8 based on the calculated resistance value RC. This makes it possible to more accurately grasp the state of the wire 8 and more appropriately protect the wire 8 from overheating.

[0119] In this application, the term "comprise" and its derivatives are non-restrictive terms that describe the presence of elements and do not exclude the presence of other elements not described. This also applies to the terms "have", "include" and their derivatives.

[0120] In this application, ordinal numbers such as "first" and "second" are merely terms for identifying components and do not have any other meaning (e.g., a particular order, etc.). For example, the presence of a "first element" does not imply the presence of a "second element," and the presence of a "second element" does not imply the presence of a "first element."

[0121] Words expressing degrees such as "substantially," "about," and "approximately" can refer to reasonable deviations that do not significantly change the end result. All numerical values ​​described in this application can be interpreted to include words such as "substantially," "about," and "approximately."

[0122] In addition, the expression "at least one of A and B" in this disclosure includes, for example, any of (1) A only, (2) B only, and (3) both A and B. The expression "at least one of A, B, and C" includes, for example, any of (1) A only, (2) B only, (3) C only, (4) A and B, (5) B and C, (6) A and C, and (7) all of A, B, and C. In this disclosure, the expression "at least one of A and B" is not to be interpreted as "at least one of A and at least one of B."

[0123] It is apparent that various changes and modifications of the present invention are possible in light of the above disclosure, and therefore, the present invention may be practiced otherwise than as specifically disclosed herein without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0124] 2: Vehicle 4:Power supply 6: Load 8:Electric wire 8U: First voltage detection point 8D: Second voltage detection point 10: Wire protection device 12: Current detection section 13: Voltage detection section 14: First voltage detection unit 16: Second voltage detection section 18: Power supply controller 20: First Unit 22: Second Unit 26: Temperature sensor A, A1, A2: Detected current value A0: Reference current value D1: Resistance temperature characteristics D2, D21, D22: Resistance value calculation formula P1: First judgment period P2: 2nd judgment period P21: Inrush current period P22: Steady current period RC: Calculated resistance value RP1: 1st reference point RP2: 2nd reference point T0: Temperature threshold TC: Calculated wire temperature TE, TE1, TE2: Detected ambient temperature TE0: Reference environmental temperature VU, VU1, VU2: First detection voltage value VD, VD1, VD2: Second detection voltage value

Claims

1. a current detection unit that detects a current value of an electric wire connecting the power supply device to a load as a detected current value; a voltage detection unit that detects a voltage value at a first voltage detection point provided between the power supply device and the electric wire as a first detected voltage value, and detects a voltage value at a second voltage detection point provided between the electric wire and the load as a second detected voltage value; a power supply controller that calculates a resistance value of the electric wire as a calculated resistance value based on the detected current value, the first detected voltage value, and the second detected voltage value, and limits power supply through the electric wire based on the calculated resistance value, the power supply controller calculates the calculated resistance value based on a resistance value calculation formula that indicates a relationship between the detected current value, the first detected voltage value, and the second detected voltage value; the power supply controller corrects an error in the resistance value calculation formula based on the first detected voltage value and the second detected voltage value output from the voltage detection unit in a state in which the power supply via the electric wire is interrupted. Wire protection device.

2. the power supply controller calculates a temperature of the electric wire as a calculated electric wire temperature based on a resistance-temperature characteristic indicating a relationship between a resistance value and a temperature of the electric wire and the calculated resistance value, and limits the power supply performed through the electric wire based on the calculated electric wire temperature. The wire protection device of claim 1 .

3. The power supply controller cuts off the power supply through the power line when the calculated power line temperature exceeds a temperature threshold. The wire protection device according to claim 2 .

4. The power supply controller allows the power supply through the electric wire when the calculated electric wire temperature is equal to or lower than the temperature threshold. The wire protection device according to claim 3.

5. the power supply controller includes a memory that stores the resistance-temperature characteristic; The wire protection device according to any one of claims 2 to 4.

6. the power supply controller corrects an error in the resistance value calculation formula based on a plurality of different detected current values ​​output from the current detection unit at a plurality of different detection timings, a plurality of different first detected voltage values ​​output from the voltage detection unit at the plurality of different detection timings, and a plurality of different second detected voltage values ​​output from the voltage detection unit at the plurality of different detection timings. The wire protection device according to any one of claims 1 to 5.

7. the power supply controller corrects an error in the resistance value calculation formula based on the multiple different detected current values ​​output from the current detection unit at the multiple different detection timings in a first determination period in which the detected current value is equal to or less than a reference current value, the multiple different first detected voltage values ​​output from the voltage detection unit at the multiple different detection timings in the first determination period, and the multiple different second detected voltage values ​​output from the voltage detection unit at the multiple different detection timings in the first determination period. The wire protection device according to claim 6.

8. the power supply controller corrects an error in the resistance value calculation formula based on the multiple different detected current values ​​output from the current detection unit at the multiple different detection timings during the first judgment period in which the detected current value is equal to or less than the reference current value and during the second judgment period until a predetermined time has elapsed since the start of the vehicle, the multiple different first detected voltage values ​​output from the voltage detection unit at the multiple different detection timings during the first judgment period and the second judgment period, and the multiple different second detected voltage values ​​output from the voltage detection unit at the multiple different detection timings during the first judgment period and the second judgment period.

8. The wire protection device of claim 7.

9. the second determination period includes an inrush current period in which the current detection unit detects an inrush current value, and a steady current period in which the current detection unit detects a steady current value after the inrush current period, the plurality of different detected current values ​​include the inrush current value and the steady-state current value; the plurality of different first detected voltage values ​​include a first inrush voltage value and a first steady-state voltage value corresponding to the inrush current value and the steady-state current value, respectively; the plurality of different second detected voltage values ​​include a second inrush voltage value and a second steady-state voltage value corresponding to the inrush current value and the steady-state current value, respectively; the power supply controller corrects an error in the resistance value calculation formula based on the inrush current value, the steady-state current value, the first inrush voltage value, the first steady-state voltage value, the second inrush voltage value, and the second steady-state voltage value.

9. The wire protection device of claim 8.

10. A temperature sensor is further provided to detect an environmental temperature of the electric wire as a detected environmental temperature. the power supply controller corrects an error in the resistance value calculation formula based on the plurality of different detected current values, the plurality of different first detected voltage values, the plurality of different second detected voltage values, and the detected environmental temperature output from the temperature sensor during the second determination period.

10. The wire protection device according to claim 8 or 9.

11. A temperature sensor is further provided to detect an environmental temperature of the electric wire as a detected environmental temperature. the power supply controller corrects an error in the resistance value calculation formula based on the plurality of different detected current values, the plurality of different first detected voltage values, the plurality of different second detected voltage values, and the detected environmental temperature. The wire protection device according to any one of claims 6 to 10.

12. the voltage detection unit includes a first voltage detection unit that detects a voltage value at the first voltage detection point as the first detected voltage value, and a second voltage detection unit that detects a voltage value at the second voltage detection point as the second detected voltage value. The wire protection device according to any one of claims 1 to 11.

13. the first voltage detection unit is connected to the first voltage detection point that is disposed on a voltage line provided between the power supply device and the load, and to a first reference point that is disposed on a ground line provided between the power supply device and the load and serves as a reference for the first detected voltage value; the second voltage detection unit is connected to the second voltage detection point disposed on the voltage line and to a second reference point disposed on the ground line and serving as a reference for the second detected voltage value; 13. The wire protection device of claim 12.

14. the second reference point is provided at a position on the ground line different from a position of the first reference point; 14. The wire protection device of claim 13.

15. the second voltage detection unit is connected to a line connecting the first voltage detection unit and the first reference point, and corrects the second detected voltage value based on a potential difference between the first reference point and the second reference point.

15. The wire protection device of claim 14.

16. The second reference point is provided on a line connecting the first voltage detection unit and the first reference point.

14. The wire protection device of claim 13.

17. The second reference point is provided at the same position as the first reference point.

17. The wire protection device of claim 16.

18. The first voltage detection unit and the second voltage detection unit are configured as an integral unit.

18. A wire protection device according to any one of claims 12 to 17.

19. A first unit; A second unit disposed at a position distant from the first unit, the first unit includes the first voltage detection unit, The second unit includes the second voltage detection unit.

18. A wire protection device according to any one of claims 12 to 17.

20. The power supply device; The load; The electric wire; The wire protection device according to any one of claims 1 to 19, The wire protection device is electrically connected to the power supply device, The wire protection device is electrically connected to the load, No other device is electrically connected between the power supply device and the wire protection device, No other equipment is electrically connected between the wire protection device and the load. In-vehicle systems.

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