Power distribution device

Abstract

A power distribution apparatus is provided: a first and a second power distribution apparatus. The first power distribution device includes: a first cutoff unit; and a first control unit that controls the first cutoff unit on the basis of the first cutoff characteristic. The second power distribution device includes: a second cutoff unit; and a second control unit that controls the second cutoff unit on the basis of the second cutoff characteristic. The first cutoff characteristic and the second cutoff characteristic are initially set such that the first cutoff time is longer than the second cutoff time. When the in-vehicle device is changed or added and the second cut-off characteristic is changed, and the first cut-off time is shorter than the second cut-off time, the first control unit performs a cut-off characteristic change process to change the first cut-off characteristic so that the first cut-off time is longer than the second cut-off time.

Description

Technical Field

[0001] The present disclosure relates to a power distribution device. Background Art

[0002] There is an on-vehicle power distribution device having a function of distributing electric power from a power source to a plurality of on-vehicle devices, which is intended to cope with additional connection of new on-vehicle devices (for example, see JP2023-014748A and JP2022-000363A).

[0003] In the power distribution device described in JP2023-014748A, conditions are set for the smoke characteristics of the electric wire on the upstream side, the fusing characteristics of the fuse on the upstream side, and the power control characteristics of the switch on the downstream side, and when the sum of the currents flowing through a plurality of vehicle-mounted devices approaches the power control characteristics of the switch on the downstream side, the power distribution to the vehicle-mounted devices is adjusted according to the priority. In the power distribution device described in JP2022-000363A, an extension including a fuse is provided in a relay device connected to the trunk power wiring, and the relay device is also connected via the extension portion.

[0004] In the power distribution device described in JP2023-014748A, the operation of a vehicle-mounted device with a low priority will be abandoned compared to a vehicle-mounted device with a high priority. In the power distribution device described in JP2022-000363A, each time a vehicle-mounted device is added or changed, the extension part in the relay device needs to be changed, which increases the burden of designing the power protection function. In the power distribution device described in JP2022-000363A, in the case where multiple relay devices are connected in series and in parallel, when a vehicle-mounted device is added or changed on the downstream side, the conditions for wire protection are not met not only in the relay device on the downstream side, but also in the relay device on the upstream side. In this case, there will be a problem that the switch or fuse on the upstream side is cut off at the same time or mistakenly cut off as the switch or fuse on the downstream side. Summary of the invention

[0005] The present disclosure aims to provide a power distribution device which can establish wire protection from the upstream side to the downstream side without redesigning the wire protection function when changing or adding a vehicle-mounted device.

[0006] According to an illustrative aspect of the present disclosure, a power distribution device includes: a first power distribution device configured to distribute power supplied from a power supply device; and a second power distribution device configured to distribute the power distributed from the first power distribution device to a vehicle-mounted device. The first power distribution device includes: a first cut-off unit configured to connect or cut off a first electric wire that supplies power from the power supply device to the second power distribution device; and a first control unit configured to control the first cut-off unit based on a first cut-off characteristic indicating a relationship between a heat of the first electric wire and a first cut-off time, the first cut-off time being a time from when power is started to the first electric wire until the first cut-off unit cuts off. The second power distribution device includes: a second cut-off unit configured to connect or cut off a second electric wire that supplies power from the first power distribution device to the vehicle-mounted device; and a second control unit configured to control the second cut-off unit based on a second cut-off characteristic indicating a relationship between a heat of the second electric wire and a second cut-off time, the second cut-off time being a time from when power is started to the second electric wire until the second cut-off unit cuts off. The first cut-off characteristic and the second cut-off characteristic are initially set so that the first cut-off time is longer than the second cut-off time. When the vehicle-mounted device is changed or added and the second cutoff characteristic is changed, and the first cutoff time is shorter than the second cutoff time, the first control unit performs a first cutoff characteristic change process to change the first cutoff characteristic so that the first cutoff time is longer than the second cutoff time.

[0007] According to the present disclosure, when the vehicle-mounted device is changed or added, the wire protection can be established from the upstream side to the downstream side without redesigning the wire protection function. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a block diagram illustrating a power distribution device according to an embodiment of the present disclosure.

[0009] Figure 2 It is a graph showing the relationship between the energization time of the electric wire and the heat change.

[0010] Figure 3 It is a logarithmic graph showing the relationship between the current flowing through the electric wire and the disconnection time of the disconnection unit.

[0011] Figure 4 This is a flowchart showing a process of changing the cutoff characteristics of the cutoff unit on the upstream side after the vehicle load on the downstream side is changed or added. DETAILED DESCRIPTION

[0012] Hereinafter, the present disclosure will be described with reference to preferred embodiments. The present disclosure is not limited to the embodiments shown below, and the embodiments shown below may be appropriately changed without departing from the gist of the present disclosure. In the embodiments described below, some configurations may not be described or shown in the drawings, and as for the details of the omitted technology, as long as they do not contradict the content described below, the known or well-known technology will be appropriately applied.

[0013] Figure 1 FIG. 1 is a block diagram showing a power distribution device 10 according to an embodiment of the present disclosure. Figure 1 As shown, the power distribution device 10 includes a first power distribution device 11, a second power distribution device 12 and a third power distribution device 13. The power distribution device 10 distributes the power supplied from the vehicle power supply device 1 to a plurality of vehicle devices (vehicle loads 2A, 2B, 2B', 2C, sensors 3A, 3C, electronic control unit (ECU) 4, etc.).

[0014] The power supply device 1 is a storage battery such as a lithium-ion battery, a power converter such as a DC / DC converter, and a generator such as an AC generator. The vehicle-mounted loads 2A, 2B, 2B′, and 2C are motors, air conditioners, lighting devices, and the like. Sensors 3A and 3C are various vehicle-mounted sensors, such as cameras, laser radars (LiDAR), millimeter-wave radars, ultrasonic sensors, global positioning system (GPS) sensors, acceleration and gyro sensors, wheel speed sensors, and air pressure sensors. The ECU 4 is an electronic control device including a microcomputer, a control area network (CAN) transceiver, an AD converter, and the like.

[0015] The first power distribution device 11 is connected to the power supply device 1 via a wire 14. The second power distribution device 12 is connected to the first power distribution device 11 via a wire 15. The third power distribution device 13 is connected to the first power distribution device 11 via a wire 16. That is, the second power distribution device 12 and the third power distribution device 13 are connected to the power supply device 1 via the first power distribution device 11.

[0016] The vehicle load 2A is connected to the first power distribution device 11 via the wire 17A. The sensor 3A is connected to the first power distribution device 11. The vehicle load 2B is connected to the second power distribution device 12 via the wire 17B. The ECU 4 is connected to the second power distribution device 12. The vehicle load 2C is connected to the third power distribution device 13 via the wire 17C. The sensor 3C is connected to the third power distribution device 13.

[0017] Here, there is a case where the vehicle-mounted devices connected to the first to third power distribution devices 11 to 13 are changed or added after the vehicle leaves the factory, for example, after the vehicle leaves the factory, the vehicle-mounted load 2B connected to the second power distribution device 12 is changed to the vehicle-mounted load 2B'. In this case, the characteristics of the wire protection function of the first to third power distribution devices 11 to 13 are automatically changed. This will be described in detail later.

[0018] The first power distribution device 11 includes a disconnection unit 111, a detection unit 112 and a control unit 113. The second power distribution device 12 includes a disconnection unit 121, a detection unit 122 and a control unit 123. The third power distribution device 13 includes a disconnection unit 131, a detection unit 132 and a control unit 133.

[0019] The disconnection units 111, 121, and 131 are relays such as semiconductor relays and mechanical relays. The disconnection unit 111 connects or disconnects the wire 14 and the wire 15, and connects or disconnects the wire 14 and the wire 16. The disconnection unit 121 connects or disconnects the wire 15 and the wire 17B. The disconnection unit 131 connects or disconnects the wire 16 and the wire 17C.

[0020] The sensor 3A is connected to the contact point on the upstream side of the cut-off unit 111. Thus, when the cut-off unit 111 is in the cut-off state, power is supplied from the power supply device 1 to the sensor 3A. The ECU 4 is connected to the contact point on the upstream side of the cut-off unit 121. Thus, when the cut-off unit 121 is in the cut-off state and the cut-off unit 111 is in the connected state, power is supplied from the power supply device 1 to the ECU 4. The sensor 3C is connected to the contact point on the upstream side of the cut-off unit 131. Thus, when the cut-off unit 131 is in the cut-off state and the cut-off unit 111 is in the connected state, power is supplied from the power supply device 1 to the sensor 3C.

[0021] On the other hand, the vehicle-mounted load 2A is connected to the contact point on the downstream side of the cut-off unit 111 through the electric wire 17A. Thus, when the cut-off unit 111 is in the cut-off state, power is not supplied from the power supply device 1 to the vehicle-mounted load 2A. The vehicle-mounted load 2B is connected to the contact point on the downstream side of the cut-off unit 121 through the electric wire 17B. Thus, when the cut-off unit 121 is in the cut-off state, power is not supplied from the power supply device 1 to the vehicle-mounted load 2B regardless of the state of the cut-off unit 111. The vehicle-mounted load 2C is connected to the contact point on the downstream side of the cut-off unit 131 through the electric wire 17C. Thus, when the cut-off unit 131 is in the cut-off state, power is not supplied from the power supply device 1 to the vehicle-mounted load 2C regardless of the state of the cut-off unit 111.

[0022] The detection unit 112 detects the voltage and current of the cut-off unit 111, and sends the detection values ​​to the control unit 113. The detection unit 122 detects the voltage and current of the cut-off unit 121, and sends the detection values ​​to the control unit 123. The detection unit 132 detects the voltage and current of the cut-off unit 131, and sends the detection values ​​to the control unit 133.

[0023] The control unit 113 includes a timer for measuring the power-on time of the electric wires 15 and 16, and a memory for storing information such as the cut-off characteristics of the cut-off unit 111. The control unit 113 determines the connection and cut-off of the cut-off unit 111 based on the power-on time measured by the timer, the detection value of the detection unit 112, and the cut-off characteristics of the cut-off unit 111 stored in the memory, and sends a control signal to the cut-off unit 111. The control unit 113 can calculate the temperature (heat) of the connected electric wires 15 and 16 based on the information obtained by the detection unit 112.

[0024] The control unit 123 includes a timer for measuring the energization time of the electric wire 17B and a memory for storing information such as the cut-off characteristics of the cut-off unit 121. The control unit 123 determines the connection and cut-off of the cut-off unit 121 based on the energization time measured by the timer, the detection value of the detection unit 122, and the cut-off characteristics of the cut-off unit 121 stored in the memory, and sends a control signal to the cut-off unit 121. The control unit 123 can calculate the temperature (heat) of the connected electric wire 17B based on the information obtained by the detection unit 122.

[0025] The control unit 133 includes a timer for measuring the energization time of the electric wire 17C and a memory for storing information such as the cut-off characteristics of the cut-off unit 131. The control unit 133 determines the connection and cut-off of the cut-off unit 131 based on the energization time measured by the timer, the detection value of the detection unit 132, and the cut-off characteristics of the cut-off unit 131 stored in the memory, and sends a control signal to the cut-off unit 131. The control unit 133 can calculate the temperature (heat) of the connected electric wire 17C based on the information obtained by the detection unit 132.

[0026] Figure 2 Graph showing the relationship between the energization time of the electric wire 15 and the heat change.

[0027] Figure 3 1 is a logarithmic graph showing the relationship between the energized current of the electric wires 15 and 17B and the cutoff time (time from the start of energization to cutoff) of the cutoff units 111 and 121. The vertical axis of the graph is a logarithmic scale.

[0028] like Figure 2As shown by the single-dot chain line and the double-dot chain line in the graph of , the cutting characteristic of the cutting unit 111 is defined by a curve representing the relationship between the heat of the electric wire 15 and the cutting time of the cutting unit 111. Figure 2 As shown by the solid line and the dotted line in the graph of , the cut-off characteristic of the cut-off unit 121 is defined by a curve representing the relationship between the heat of the electric wires 17B and 17B′ and the cut-off time of the cut-off unit 121. Figure 2 Although not shown in the graph of FIG. 17C , the cut-off characteristic of the cut-off unit 131 is defined by a curve representing the relationship between the amount of heat of the electric wire 17C and the cut-off time of the cut-off unit 131 .

[0029] The control unit 113 of the first power distribution device 11 reads the cut-off time (threshold) corresponding to the temperature (heat) of the electric wires 15 and 16 calculated based on the detection value of the energized current detected by the detection unit 112 from the cut-off characteristics of the cut-off unit 111, and when the energized time measured by the timer exceeds the threshold, determines the cut-off of the cut-off unit 111, and sends a cut-off signal to the cut-off unit 111. The control unit 123 of the second power distribution device 12 reads the cut-off time (threshold) corresponding to the temperature (heat) of the electric wire 17B calculated based on the detection value of the energized current detected by the detection unit 122 from the cut-off characteristics of the cut-off unit 121, and when the energized time measured by the timer exceeds the threshold, determines the cut-off of the cut-off unit 121, and sends a cut-off signal to the cut-off unit 121. The control unit 133 of the third power distribution device 13 reads the cut-off time (threshold) corresponding to the temperature (heat) of the electric wire 17C calculated based on the detection value of the power-on current detected by the detection unit 132 from the cut-off characteristics of the cut-off unit 131, and when the power-on time measured by the timer exceeds the threshold, determines the cut-off of the cut-off unit 131 and sends a cut-off signal to the cut-off unit 131.

[0030] like Figure 1 As shown, the control unit 113 of the first power distribution device 11, the control unit 123 of the second power distribution device 12, and the control unit 133 of the third power distribution device 13 are communicably connected. The control unit 123 of the second power distribution device 12 sends the detection value of the open circuit voltage of the cut-off unit 121 detected by the detection unit 122 to the control unit 113 of the first power distribution device 11. The control unit 133 of the third power distribution device 13 sends the detection value of the open circuit voltage of the cut-off unit 131 detected by the detection unit 132 to the control unit 113 of the first power distribution device 11.

[0031] The control unit 113 of the first power distribution device 11 compares the detection value of the open circuit voltage of the disconnection unit 121 received from the control unit 123 of the second power distribution device 12 with the detection value of the open circuit voltage of the disconnection unit 111 received from the detection unit 112. When the open circuit voltage of the disconnection unit 111 is higher than the open circuit voltage of the disconnection unit 121, the control unit 113 of the first power distribution device 11 determines that the disconnection unit 111 is located upstream of the disconnection unit 121.

[0032] The control unit 113 of the first power distribution device 11 compares the detection value of the open circuit voltage of the cut-off unit 131 received from the control unit 133 of the third power distribution device 13 with the detection value of the open circuit voltage of the cut-off unit 111 received from the detection unit 112. When the open circuit voltage of the cut-off unit 111 is higher than the open circuit voltage of the cut-off unit 131, the control unit 113 of the first power distribution device 11 determines that the cut-off unit 111 is located upstream of the cut-off unit 131. The method of determining the upstream and downstream relationship between the cut-off unit 111 and the cut-off units 121 and 131 is not limited to the method based on the open circuit voltage, and may be replaced by other methods, such as pre-storing information indicating the relationship of the upstream and downstream.

[0033] The control units 113, 123 and 133 are communicably connected to Figure 1 The vehicle-mounted communication device 18 shown. The communication device 18 is communicatively connected to the data center DC via a wireless communication network such as a mobile phone network. The control units 113, 123 and 133 are capable of sending an acquisition request for information related to changes in the vehicle-mounted loads 2A, 2B and 2C (hereinafter referred to as load change information) to the communication device 18. The communication device 18 is capable of sending an acquisition request for the load change information received from the control units 113, 123 and 133 to the data center DC. The data center DC stores the load change information related to the cut-off characteristics of the cut-off units 111, 121 and 131, and can send the load change information to the communication device 18 in response to the received acquisition request. The communication device 18 is capable of sending the load change information received from the data center DC to the control units 113, 123 and 133.

[0034] The control units 113, 123 and 133 can communicate with the service terminal ST in a wired or wireless manner. The control units 113, 123 and 133 can send an acquisition request for load change information to the service terminal ST. The service terminal ST stores the load change information related to the disconnection characteristics of the disconnection units 111, 121 and 131, and can send the load change information to the control units 113, 123 and 133 in response to the received acquisition request.

[0035] Here, a case where the vehicle-mounted load 2B connected to the cut-off unit 121 of the second power distribution device 12 is changed to the vehicle-mounted load 2B′ will be described. Assume an example in which a state where a small lighting device lit with a relatively small current, that is, the vehicle-mounted load 2B, is connected to the cut-off unit 121 through an electric wire 17B of a specification matching the small current, is changed to a state where a large lighting device lit with a relatively large current, that is, the vehicle-mounted load 2B′, is connected to the cut-off unit 121 through an electric wire 17B′ of a specification matching the large current.

[0036] In this hypothetical example, if Figure 3 As shown by the solid line in the graph of , the relationship between the current and the cut-off time of the cut-off unit 121 corresponding to the vehicle load 2B before the change is initially set based on the relatively small current (I2), that is, the current. Figure 3 As shown by the dotted line in the graph, the relationship between the energized current and the cut-off time of the cut-off portion 121 corresponding to the changed vehicle load 2B′ is set based on the relatively large current (I2′), that is, the energized current.

[0037] Initial Settings Figure 2 The dotted line in the graph shows the smoke characteristics of the electric wire 15 (the relationship between the heat and the time from the start of power-on to smoke generation (hereinafter referred to as the smoke generation time)). Figure 3 In the graph of FIG. 1 , the curve indicating the relationship between the current before the change and the cutoff time of the cutoff unit 111 indicated by the single-dot chain line is initially set to fall between the curve indicating the relationship between the voltage before the change and the cutoff time of the cutoff unit 121 and the curve indicating the relationship between the current of the electric wire 15 and the time until smoke is emitted. Figure 3 Although not shown in the graph of FIG. 1 , the curve representing the relationship between the energized current and the cut-off time before the change of the cut-off unit 111 is initially set to fall between the curve representing the relationship between the energized voltage and the cut-off time of the cut-off unit 131 and the curve representing the relationship between the amount of energized current of the electric wire 15 and the time until smoke is emitted. That is, the relationship between the energized current and the cut-off time of the cut-off units 111, 121, and 131 is initially set so that the cut-off time of the cut-off unit 111 is shorter than the smoke emission time of the electric wire 15, and longer than the cut-off time of the cut-off units 121 and 131.

[0038] on the other hand, Figure 3The curve indicating the relationship between the current before the change and the cut-off time of the cut-off unit 111, shown by the single-point dashed line in the curve diagram, intersects with the curve indicating the relationship between the current after the change and the cut-off time of the cut-off unit 121 when the current is I3 (>I2'>I2), and does not fall between the curve indicating the relationship between the current after the change and the cut-off time of the cut-off unit 121 and the curve indicating the relationship between the current amount of the electric wire 15 and the time until smoke is emitted. That is, when the current is equal to or greater than I3, the cut-off time of the cut-off unit 111 is shorter than the cut-off time of the cut-off unit 121. Thus, when the current is I3, the cut-off unit 111 and the cut-off unit 121 are cut off at the same time, resulting in a situation in which not only the on-vehicle load 2B′ but also the ECU 4 cannot operate at the same time when an abnormality occurs in the on-vehicle load 2B′.

[0039] Therefore, in the power distribution device 10 according to the present embodiment, when the on-vehicle loads 2B and 2C on the downstream side change, not only the cut-off characteristics of the cut-off units 121 and 131 corresponding to the changed on-vehicle loads 2B and 2C change, but also the cut-off characteristics of the cut-off unit 111 on the upstream side change. Specifically, first, each time the power distribution device 1 is reset, the control units 113, 123, and 133 acquire the detection values ​​of the voltage and current of the cut-off units 111, 121, and 131 from the detection units 112, 122, and 132. The control units 113, 123, and 133 determine whether the change processing of the cut-off characteristics of the cut-off units 111 and 131 is required based on the amount of change in the detection values ​​of the voltage and current of the cut-off units 111, 121, and 131. In the above hypothetical example, since the detected values ​​of the voltage and current of the cutoff unit 121 change when the vehicle-mounted load 2B connected to the cutoff unit 121 becomes the vehicle-mounted load 2B′, the control unit 123 determines that the change process of the cutoff characteristic of the cutoff unit 121 is required.

[0040] When the control units 113, 123 and 133 determine that the cut-off characteristics of the cut-off units 111, 121 and 131 need to be changed, the control units 113, 123 and 133 send a request to obtain load change information to the data center DC or the service terminal ST, and receive load change information from the data center DC or the service terminal ST. The control units 113, 123 and 133 change the cut-off characteristics of the cut-off units 111, 121 and 131 according to the received load change information.

[0041] Next, the control unit 113 of the first power distribution device 11 changes the cutoff characteristics of the cutoff unit 111 so that the curve representing the relationship between the energized current of the cutoff unit 111 and the cutoff time falls between the curve representing the relationship between the changed energized current and the cutoff time of the cutoff units 121 and 131 and the curve representing the relationship between the energized current of the electric wire 15 and the time until the smoke is emitted. Hereinafter, the process of changing the cutoff characteristics of the cutoff unit 111 on the upstream side after changing or adding the onboard loads 2B and 3B on the downstream side will be described.

[0042] Figure 4 1 is a flowchart showing a process of changing the cutoff characteristic of the cutoff unit 111 on the upstream side after the vehicle-mounted loads 2B and 3B on the downstream side are changed or added. The process shown in the flowchart starts when the power supply device 1 is reset.

[0043] First, the control units 113, 123, and 133 acquire the detected values ​​of the voltage and current of the cut-off units 111, 121, and 131 from the detection units 112, 122, and 132, and determine whether the change amount of the detected value since the last reset of the power supply device 1 exceeds the threshold value (step S1). If it is determined to be "yes" in step S1, the process proceeds to step S2, and if it is determined to be "no" in step S2, the process proceeds to normal processing.

[0044] Next, the control units 113, 123 and 133 send a request to obtain load change information to the data center DC or the service terminal ST, and obtain load change information such as the cut-off characteristics of the vehicle load after the change (step S2). Next, the control units 113, 123 and 133 change the cut-off characteristics of the corresponding cut-off units 111, 121 and 131 based on the obtained load change information (step S3).

[0045] Next, the control unit 113 acquires detection values ​​of the open circuit voltages of the cutoff units 111, 121, and 131 detected by the detection units 112, 122, and 132, and determines upstream and downstream relationships of the cutoff units 111, 121, and 131 based on the acquired detection values ​​(step S4).

[0046] Next, the control unit 123 sends the cut-off characteristic of the cut-off unit 121 to the control unit 113, and the control unit 133 sends the cut-off characteristic of the cut-off unit 131 to the control unit 113 (step S5). Next, the control unit 113 calculates the heat of the wires 15, 17B, 17B' and 17C (hereinafter referred to as the wires 15, etc.) when the virtual stabilization current flows through the wires 15, 17B, 17B' and 17C using the following formulas (1) to (6) (step S6).

[0047] When the electric wire 15 etc. starts to be energized, the control unit 113 calculates the heat generation amount X1 per unit length of the electric wire 15 etc. using the following formula (1).

[0048] [Formula 1]

[0049] X1=I 2 ×R on Δt…(1)

[0050] Where, I is the detection value of the current of the detection units 112, 122 and 132, R on is the resistance per unit length of the electric wire 15 or the like, and Δt is the sampling time (eg, 5 milliseconds).

[0051] The control unit 113 calculates the heat release amount Y1 of the electric wire 15 and the like using the following formula (2).

[0052] [Formula 2]

[0053] Y1=Q / (C th * ×R th / Δt)…(2)

[0054] Among them, C th * is the pseudo heat capacity per unit length of the electric wire 15, etc., R th is the thermal resistance per unit length of the wire 15 etc., Δt is the sampling time (e.g., 5 milliseconds), and Q is the heat per unit length of the wire 15 etc. and is obtained by multiplying the wire temperature by the pseudo heat capacity C th * The value obtained.

[0055] The control unit 113 calculates the wire temperature T using the following formula (3): n .

[0056] [Formula 3]

[0057] T n =T p +(X1-Y1) / C th * …(3)

[0058] Among them, T p It is the temperature of the electric wire 15 etc. at the time of the previous measurement.

[0059] That is, every time the sampling time Δt elapses, the control unit 113 calculates the temperature T of the electric wire 15 and the like at the time of the previous measurement. p Add the heat generation X1 or subtract the heat generation Y1 to calculate the wire temperature T of wire 15, etc. during this measurement. n .

[0060] In the following, the calculation of the pseudo heat capacity C will be described. th * Methods. Figure 2 As shown by the single-point dashed line curve in the graph of , when any current continues to flow through the wire 15, etc., the heat of the wire 15, etc. increases. It can be understood that the temperature T2 of the wire 15, etc. at this time is expressed by the following formula (4).

[0061] [Formula 4]

[0062]

[0063] T1 is the ambient temperature, C th is the heat capacity per unit length of the electric wire 15 etc., and t is the elapsed time.

[0064] The control unit 113 determines the continuous current I of a fuse that can be energized based on the current I of a fuse that is commonly used in a standard manner for the electric wire 15 or the like. max , calculate the temperature threshold ΔT expressed by the following formula (5) max The continuous current I of the fuse max This can be obtained by actually passing current through the fuse and measuring the current and time until the fuse blows.

[0065] [Formula 5]

[0066] ΔT max =R th ×R on ×I max 2 …(5)

[0067] Temperature threshold ΔT max The upper limit of the temperature rise ΔT relative to the ambient temperature. If the temperature rise ΔT exceeds ΔT max When the cut-off unit 111 is cut off in the case of a fault, the cut-off unit 111 is cut off with characteristics equivalent to those of the above-mentioned fuse.

[0068] In the above formula (4), when T2-T1=ΔT, the following formula (4') is obtained.

[0069] [Formula 6]

[0070]

[0071] By appropriately changing the current I in the above formula (4'), increasing the elapsed time t of each current I, and plotting the temperature rise Δt when it reaches the temperature threshold ΔT max time, get Figure 3 The curve diagram shows the relationship between the on-current and the off-time. maxMultiplying by the mass and specific heat of wire 15, etc., we get Figure 2 The heat thresholds (cut-off threshold A, cut-off threshold A', cut-off threshold B and cut-off threshold B') are shown in the curve graph.

[0072] The temperature threshold ΔT calculated by the above formula (5) max Substitute the value of into ΔT in the above formula (4') and transform the formula so that the left side becomes the heat capacity C th Then use the pseudo heat capacity C th * Replacement heat capacity C th , and we get the following formula (6).

[0073] [Formula 7]

[0074]

[0075] like Figure 4 As shown in the flowchart in, the control unit 113 calculates the cut-off time of each cut-off unit 111, 121 and 131 when the virtual stable current flows through the wire 15, etc. based on the heat and cut-off threshold of each cut-off unit 111, 121 and 131 (step S7).

[0076] Next, the control unit 113 determines whether the cut-off time of the cut-off units 121 and 131 is longer than the cut-off time of the cut-off unit 111 (step S8). Figure 2 As shown in the curve diagram in , in the initial setting, the cut-off time T1 of the cut-off unit 111 is longer than the cut-off time T2 of the cut-off unit 121, but after the vehicle load 2B changes, the cut-off time T1 of the cut-off unit 111 is expected to be shorter than the cut-off time T2' of the cut-off unit 121. Figure 4 As shown in the flowchart in , if the determination in step S8 is “Yes”, the process proceeds to step S9, and if the determination in step S8 is “No”, the process enters the normal process.

[0077] The control unit 113 changes the time constant τ shown in the following equation (7) to change the cut-off characteristic of the cut-off unit 111 so that the cut-off characteristic of the cut-off unit 111 falls between the cut-off characteristics after the change of the cut-off units 121 and 131 and the smoke characteristic of the electric wire 15 (step S9). Figure 2 As shown in the curve diagram in , the cut-off time T1 ′ of the cut-off unit 111 is longer than the cut-off time T2 ′ of the cut-off unit 121 .

[0078] [Formula 8]

[0079]

[0080] t 2B′This is the cut-off time of the cut-off unit 121 when the changed vehicle-mounted load 2B' is connected via the wire 17B'. t W This is the smoke generation time of the wire 15. I 15 This is the initial set value of the energizing current of the wire 15. I sim This is the virtual steady current. x is a real number in the range of 0 < x < ∞. When x approaches 0, the cut-off characteristic of the cut-off unit 111 approaches the changed cut-off characteristic of the cut-off unit 121. On the contrary, when x approaches ∞, the cut-off characteristic of the cut-off unit 111 approaches the smoke generation characteristic of the wire 15.

[0081] The above formula (7) is obtained by converting the above formula (6) into the following formula (8) with ΔT max as the left side, then converting the following formula (8) into a formula with the time constant τ as the left side, and then converting ΔT max into the value between the temperature threshold of the changed cut-off unit 121 of the vehicle-mounted load 2B' and the temperature threshold of the smoke generation characteristic of the wire 15.

[0082] [Formula 9]

[0083]

[0084] As Figure 4 shown in the flowchart in, the control unit 113 determines whether the cut-off time of the cut-off unit 111 is longer than the cut-off times of the cut-off units 121 and 131 (step S10). If it is determined as "yes" in step S10, the process proceeds to the normal process. If it is determined as "no" in step S10, the alarm process is executed (step S11), and the process proceeds to the normal process.

[0085] As described above, in the power distribution device 10 according to the present embodiment, when the vehicle-mounted loads 2B and 2C connected to the second power distribution device 12 and the third power distribution device 13 on the downstream side are changed or added, the cut-off characteristics of the cut-off units 121 and 131 of the second power distribution device 12 and the third power distribution device 13 are changed. In this case, when the cut-off time of the cut-off unit 111 of the first power distribution device 11 on the upstream side is shorter than the cut-off time of the cut-off units 121 and 131, the control unit 113 of the first power distribution device 11 on the upstream side changes the cut-off characteristics of the cut-off unit 111 so that the cut-off time of the cut-off unit 111 is longer than the cut-off time of the cut-off units 121 and 131. Therefore, when the vehicle-mounted loads 2B and 2C connected to the second power distribution device 12 and the third power distribution device 13 on the downstream side are added or changed, it is possible to protect the electric wires 15 and the like from the upstream side to the downstream side without redesigning the cut-off units 111, 121, and 131. It is also possible to prevent simultaneous cutting between the cutting unit 111 on the upstream side and the cutting devices 121 and 131 on the downstream side.

[0086] In the power distribution device 10 according to the present embodiment, the cut-off characteristics of the cut-off unit 111 on the upstream side and the cut-off units 121 and 131 on the downstream side are initially set so that the cut-off time of the cut-off unit 111 and the cut-off devices 121 and 131 is shorter than the smoke emission time, which is the time from the start of energization to the emission of smoke from the electric wire 15. The cut-off characteristics of the cut-off unit 111 and the cut-off units 121 and 131 are initially set so that the cut-off time of the cut-off unit 111 is longer than the cut-off time of the cut-off units 121 and 131. On the contrary, in the case where the vehicle-mounted loads 2B and 2C connected to the second power distribution device 12 and the third power distribution device 13 on the downstream side are changed or added, and the cut-off characteristics of the cut-off units 121 and 131 are changed, when the cut-off time of the cut-off unit 111 is shorter than the cut-off time of the cut-off units 121 and 131, the control unit 113 changes the cut-off characteristics of the cut-off unit 111 so that the cut-off time of the cut-off unit 111 is longer than the cut-off time of the cut-off units 121 and 131 and shorter than the smoke emission time of the electric wire 15. This prevents the upstream cutoff unit 111 and the downstream cutoff units 121 and 131 from cutting off at the same time, and reliably prevents the electric wire 15 from smoking.

[0087] In the power distribution device 10 of the present embodiment, the control unit 113 on the upstream side is communicably connected to the control units 123 and 133 on the downstream side. The control unit 113 on the upstream side receives the cut-off characteristics of the cut-off units 121 and 131 on the downstream side from the control units 123 and 133 on the downstream side. The control unit 113 on the upstream side calculates the cut-off time of the cut-off units 121 and 131 when a predetermined energizing current flows through the electric wires 17B, 17B′, and 17C based on the cut-off characteristics of the cut-off units 121 and 131 received. The control unit 113 on the upstream side calculates the cut-off time of the cut-off unit 111 when a predetermined energizing current flows through the electric wires 15 and 16 based on the cut-off characteristics of the cut-off unit 111. When the calculated cut-off time of the cut-off unit 111 is shorter than the calculated cut-off time of the cut-off units 121 and 131, the control unit 113 on the upstream side changes the cut-off characteristics of the cut-off unit 111 so that the cut-off time in the cut-off unit 111 is longer than the cut-off time in the cut-off units 121 and 131. Thus, it is possible to compare the cutoff times of the cutoff units 111 , 121 , and 131 after the vehicle-mounted loads 2B and 2C are changed or added, and change the cutoff characteristics of the cutoff unit 111 based on the comparison result.

[0088] In the power distribution device 10 according to the present embodiment, the first power distribution device 11 on the upstream side includes a detection unit 112 that detects the voltage and current of the cut-off unit 111, and the second power distribution device 12 and the third power distribution device 13 on the downstream side include detection units 122 and 132 that detect the voltage and current of the cut-off units 121 and 131. The control unit 113 of the first power distribution device 11 receives the detection values ​​of the voltage and current of the cut-off units 121 and 131 detected by the detection units 122 and 132 from the control units 123 and 133 of the second power distribution device 12 and the third power distribution device 13. Thus, the control unit 113 of the first power distribution device 11 can determine the upstream and downstream relationship of the cut-off units 111, 121, and 131 by comparing the voltage of the cut-off unit 111 on the upstream side with the voltage of the cut-off devices 121 and 131 on the downstream side. The control unit 113 of the first power distribution device 11 can calculate the heat of the electric wire 15, etc. based on the current of the cut-off units 111, 121, and 131.

[0089] The present disclosure has been described above based on the above embodiments, but the present disclosure is not limited to the above embodiments, and the above embodiments may be modified, and known or well-known technologies may be appropriately combined within a scope not departing from the gist of the present disclosure.

Claims

1. A power distribution device, comprising: a first power distribution device configured to distribute power supplied from the power supply device; as well as The second power distribution device is configured to distribute the power distributed from the first power distribution device to the vehicle-mounted device, wherein: The first power distribution device comprises: a first disconnection unit configured to connect or disconnect a first electric wire that supplies power from the power supply device to the second power distribution device; and a first control unit configured to control the first cutting unit based on a first cutting characteristic indicating a relationship between a heat amount of the first electric wire and a first cutting time, the first cutting time being a time from when power is supplied to the first electric wire to when the first cutting unit cuts off the first electric wire; The second power distribution device comprises: a second disconnection unit configured to connect or disconnect a second electric wire that supplies power from the first power distribution device to the in-vehicle device; and a second control unit configured to control the second cutting unit based on a second cutting characteristic indicating a relationship between a heat amount of the second electric wire and a second cutting time, the second cutting time being a time from when power is supplied to the second electric wire to when the second cutting unit cuts off the wire; The first cutoff characteristic and the second cutoff characteristic are initially set such that the first cutoff time is longer than the second cutoff time, When the vehicle-mounted device is changed or added and the second cutoff characteristic is changed, and the first cutoff time is shorter than the second cutoff time, the first control unit performs a first cutoff characteristic change process to change the first cutoff characteristic so that the first cutoff time is longer than the second cutoff time.

2. The power distribution device according to claim 1, wherein: The first cutoff characteristic and the second cutoff characteristic are initially set so that the first cutoff time and the second cutoff time are shorter than a smoke generation time, which is a time from when power is supplied to the first electric wire to when smoke is generated, and The first control unit changes the first cutoff characteristic in the first cutoff characteristic changing process so that the first cutoff time is longer than the second cutoff time and shorter than the smoking time.

3. The power distribution device according to claim 1 or 2, wherein: The first control unit and the second control unit are communicatively connected, and The first control unit is configured to: receiving the second cut-off characteristic from the second control unit; calculating the first cutoff time when a predetermined energizing current flows through the first electric wire based on the first cutoff characteristic; calculating the second cutoff time when the predetermined energizing current flows through the second electric wire based on the second cutoff characteristic; When the calculated first cutoff time is shorter than the calculated second cutoff time, the first cutoff characteristic changing process is performed.

4. The power distribution device according to claim 3, wherein: The first power distribution device includes a first detection unit configured to detect a voltage and a current of the first cut-off unit, The second power distribution device includes a second detection unit configured to detect a voltage and a current of the second cut-off unit, and The first control unit receives, from the second control unit, detection values ​​of the voltage and the current of the second cutoff unit detected by the second detection unit.

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