Current path control device and vehicle power supply system

Abstract

This current path control device is provided in a vehicle power supply system including a plurality of power distribution devices for respectively distributing power to loads of a vehicle, a power supply trunk line for mutually connecting the plurality of power distribution devices, and a plurality of power supply devices capable of respectively supplying power to the power distribution devices via the power supply trunk line, and controls current paths when power is supplied from the power supply devices to the power distribution devices in the vehicle power supply system. The current path control device switches the current paths on the basis of a demand change in load currents flowing from the power distribution devices to the loads.

Description

Current path control device, vehicle power supply system

[0001] The present invention relates to a device for controlling a current path in a vehicle power supply system, and a vehicle power supply system including the device.

[0002] In recent years, advances in the electrification and autonomous driving of automobiles have led to an increase in the number of onboard devices installed in automobiles. This has led to demands for a reduction in the number of wire harnesses used to supply power to each onboard device, as well as for higher reliability and lower loss in onboard power net systems. However, conventional 12V onboard power net systems often use a method in which a relay box or fuse box is installed near the battery, and power cables are individually connected from there to onboard devices such as various sensors and actuators installed in various locations throughout the vehicle. However, this conventional method of supplying power to onboard devices poses the problem of requiring a huge number of wire harnesses due to the increase in the number of onboard devices to be powered and the need for redundant power supply paths for higher reliability.

[0003] To address this issue, a method has been proposed in which a vehicle is divided into multiple zones, a power distribution device that distributes power to onboard devices is installed in each zone, and these power distribution devices are connected in a ring shape by a power trunk line to form a power grid. By installing a power distribution device in each zone in this way, power is distributed near various sensors and actuators, which shortens the total length of the wiring harness. Furthermore, by interconnecting the power distribution devices in a ring shape, power interruptions due to failures in the power trunk line can be avoided.

[0004] The following prior art is known as background art in this technical field: Patent Document 1 describes an in-vehicle power supply system in which the output of an in-vehicle battery is branched into multiple power supply lines at a fuse unit or the like, an inter-path connection switch is provided that enables the two power supply lines to be connected via a power distribution device in a previous stage, and if one of the power supply lines is disconnected, the circuit of the inter-path connection switch is closed to transmit power through the multiple paths.

[0005] Japanese Patent Application Publication No. 2023-19095

[0006] In the onboard power supply system described in Patent Document 1, multiple power lines are provided from a fuse unit to a power distribution device at a preceding stage, and by allowing the multiple power lines to be used simultaneously, power loss due to the power lines can be reduced. However, this configuration requires multiple power lines for each power conversion device, and also requires a backflow prevention diode to electrically disconnect a broken power line, so there is room for further improvement in realizing a low-loss and efficient vehicle power supply system.

[0007] A current path control device according to the present invention is provided in a vehicle power supply system including a plurality of power distribution devices that distribute power to vehicle loads, a power supply trunk line connecting the plurality of power distribution devices to each other, and a plurality of power supply devices that can each supply power to the power distribution devices via the power supply trunk line, and is a device for controlling a current path when power is supplied from the power supply devices to the power distribution devices in the vehicle power supply system, and switches the current path based on changes in demand for load current flowing from the power distribution devices to the loads. The vehicle power supply system according to the present invention includes the current path control device, a plurality of power distribution devices that distribute power to the vehicle loads, a power supply trunk line connecting the plurality of power distribution devices to each other, and a plurality of power supply devices that can each supply power to the power distribution devices via the power supply trunk line.

[0008] According to the present invention, a low-loss and efficient vehicle power supply system can be realized.

[0009] FIG. 1 is a configuration diagram of an in-vehicle power net system according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of a change in a current path in the in-vehicle power net system according to the first embodiment of the present invention. FIG. 3 is a diagram showing the functional configuration of a power distribution device and a current path control device according to the first embodiment of the present invention. FIG. 4 is a timing chart showing an example of the timing at which an update determination unit issues an instruction to update a current path to a path calculation unit. FIG. 5 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a second embodiment of the present invention. FIG. 6 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a third embodiment of the present invention. FIG. 7 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a fourth embodiment of the present invention. FIG. 8 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a fifth embodiment of the present invention. FIG. 9 is a diagram showing a modified system configuration. FIG. 10 is a diagram showing a modified method of acquiring a load current.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] (First Embodiment) Fig. 1 is a configuration diagram of an in-vehicle power net system according to a first embodiment of the present invention. The in-vehicle power net system 100 shown in Fig. 1 is an example of an in-vehicle power net system that forms a power grid suitable for applying the present invention, and is mounted on a vehicle such as an automobile for use. The in-vehicle power net system 100 is configured to include power distribution devices 1a, 1b, 1c, and 1d, power supply trunk lines 3a, 3b, 3c, 3d, 3e, and 3f, a battery 4, a DC / DC converter 5, and a current path control device 8.

[0012] When the vehicle is divided into four zones, namely, the front right side, the front left side, the rear right side, and the rear left side, the power distribution devices 1a to 1d are installed in each zone, respectively, and distribute power to the vehicle loads 2a to 2d in each zone. The battery 4 and the DC / DC converter 5 function as power supply devices in the in-vehicle power net system 100 that can supply power to the vehicle loads 2a to 2d via the power distribution devices 1a to 1d, respectively.

[0013] Power distribution devices 1a to 1d, battery 4, and DC / DC converter 5 are interconnected in a ring shape by power supply trunk lines 3a to 3f. Specifically, power supply trunk line 3a connects battery 4 to power distribution device 1a. Power supply trunk line 3b connects power distribution device 1a to power distribution device 1b. Power supply trunk lines 3c and 3d connect power distribution device 1b to power distribution device 1c. A DC / DC converter 5 is connected between power distribution device 1b and power distribution device 1c via power supply trunk lines 3c and 3d. Power distribution device 1c and power distribution device 1d are interconnected by power supply trunk line 3e. Power distribution device 1d is connected to battery 4 by power supply trunk line 3f. These connections form a ring-shaped in-vehicle power net system 100.

[0014] Battery 4 is a chargeable and dischargeable secondary battery that supplies power to each of vehicle loads 2a to 2d by discharging the charged power. Examples of battery 4 that can be used include lead-acid batteries, nickel-metal hydride batteries, and lithium-ion batteries. DC / DC converter 5 reduces the DC voltage from a high-voltage battery HV (not shown) (e.g., a 400V lithium-ion battery) to a predetermined voltage, e.g., 12V, and supplies the reduced DC power to each of vehicle loads 2a to 2d. The high-voltage battery HV has a higher output voltage than battery 4. For example, a battery that supplies power to a traction motor of an electric vehicle or hybrid vehicle equipped with on-vehicle power net system 100 can be used as the high-voltage battery HV.

[0015] 1 illustrates the battery 4 and the DC / DC converter 5 as examples of power supply devices for the in-vehicle power net system 100, but an alternator that generates power using the driving force of the vehicle's engine can be used instead of or in addition to the battery 4 or the DC / DC converter 5. In other words, any power supply device that can generate power from different energy sources can be appropriately selected from various types of power supply devices and connected to the in-vehicle power net system 100 to be used as a power supply device that supplies power to the vehicle loads 2a to 2d. Also, in FIG. 1, the battery 4 is connected to the power supply trunk lines 3a and 3f, and the DC / DC converter 5 is connected to the power supply trunk lines 3c and 3d, but the power supply trunk lines connected to the battery 4 and the DC / DC converter 5 are not limited to these, and they may be connected to other power supply trunk lines.

[0016] In the in-vehicle power net system 100 shown in FIG. 1, if any of the power supply trunks 3a-3f is broken, the broken location is disconnected, and power can be continued to be supplied to the vehicle loads 2a-2d beyond the broken location by detouring the power from another route. For example, in FIG. 1, if the power supply trunk 3a between the battery 4 and the power distribution device 1a is broken, current flows from the battery 4 to the power distribution device 1a via the power supply trunks 3f, 3e, 3d, 3c, and 3b, and the power thus supplied is distributed from the power distribution device 1a to the vehicle load 2a, thereby continuing the power supply to the vehicle load 2a. Furthermore, if either the battery 4 or the DC / DC converter 5 fails, the other power supply device can be used to continue the power supply to the vehicle loads 2a-2d. 1, if battery 4 fails, current flows from DC / DC converter 5 to power distribution device 1a via power supply trunk lines 3c and 3b, and the power thus supplied is distributed from power distribution device 1a to vehicle load 2a, thereby allowing power supply to vehicle load 2a to continue. Control of the current path during power supply to vehicle loads 2a to 2d is performed by current path control device 8, as will be described later.

[0017] The power distribution device 1a includes a switch element 6a that electrically opens and closes the connection with the power supply trunk line 3a, and a switch element 6b that electrically opens and closes the connection with the power supply trunk line 3b. One end of the switch element 6a is connected to the power supply trunk line 3a, and the other end is connected to the switch element 6b. One end of the switch element 6b is connected to the power supply trunk line 3b, and the other end is connected to the switch element 6a. A vehicle load 2a is connected to the connection line between the switch element 6a and the switch element 6b. The switch elements 6a and 6b may be semiconductor switches such as power MOSFETs or GaN transistors, for example.

[0018] The power distribution device 1a also includes a current detection element 7a that detects a load current Ia flowing from the power supply trunk 3a or 3b to the vehicle load 2a. The load current Ia is the sum of the currents supplied to the multiple on-board loads connected to the power distribution device 1a. This load current Ia is transmitted to a current path control device 8. The current path control device 8 detects changes in the load current Ia as changes in current demand in the power distribution device 1a. The changes in current demand are information indicating changes in load current due to the operation or stop of the loads connected to the power distribution device. The other power distribution devices 1b to 1d also include similar current detection elements 7b to 7d, which transmit the load currents Ib to Id of each power distribution device to the current path control device 8, and the current path control device 8 detects changes in the load currents Ib to Ic as changes in current demand for each power distribution device. The current detection element 7a can be, for example, a shunt resistor or a Hall element. While this embodiment illustrates a configuration in which one current detection element is provided for multiple loads, the present invention is not limited to this configuration. For example, a current detection element may be provided for each load connected to the power distribution device, and the load current may be obtained from the total value of the currents detected by the current detection elements.

[0019] The other power distribution devices 1b to 1d have the same configuration as power distribution device 1a. That is, power distribution device 1b includes a switch element 6c that electrically opens and closes the connection with power supply trunk line 3b, a switch element 6d that electrically opens and closes the connection with power supply trunk line 3c, and a current detection element 7b that detects a load current Ib flowing from power supply trunk line 3b or 3c to vehicle load 2b. Power distribution device 1c includes a switch element 6e that electrically opens and closes the connection with power supply trunk line 3d, a switch element 6f that electrically opens and closes the connection with power supply trunk line 3e, and a current detection element 7c that detects a load current Ic flowing from power supply trunk line 3d or 3e to vehicle load 2c. Power distribution device 1d includes a switch element 6g that electrically opens and closes the connection with power supply trunk line 3e, a switch element 6h that electrically opens and closes the connection with power supply trunk line 3f, and a current detection element 7d that detects a load current Id flowing from power supply trunk line 3e or 3f to vehicle load 2d.

[0020] The in-vehicle power net system 100 of this embodiment further includes a current path control device 8. The current path control device 8 acquires information on the load currents Ia to Id from the power distribution devices 1a to 1d, respectively, and determines the opening and closing patterns of the switch elements 6a to 6h included in the power distribution devices 1a to 1d based on the acquired information on the load currents Ia to Ib. The information on the opening and closing patterns of the switch elements determined by the current path control device 8 is transmitted to each power distribution device as switch information Sa to Sd. Based on the received switch information Sa to Sd, the power distribution devices 1a to 1d open and close the switch elements included in each power distribution device according to the opening and closing patterns determined by the current path control device 8. The information on the load currents Ia to Ib and the switch information Sa to Sd are transmitted and received between the current path control device 8 and each power distribution device via communication lines 9a to 9d. For transmitting and receiving this information via the communication lines 9a to 9d, communication standards such as CAN (Controller Area Network) and Ethernet (registered trademark) can be used.

[0021] 2A and 2B are diagrams illustrating an example of a change in a current path in the in-vehicle power net system according to the first embodiment of the present invention. FIG. 2A illustrates an example of the state of the current path before switch information Sa to Sd is transmitted from the current path control device 8 to the power distribution devices 1a to 1d. In this state, a load current Id is supplied from the battery 4 via the power supply trunk line 3f to the vehicle load 2d connected to the power distribution device 1d. Furthermore, a load current Ic is supplied from the battery 4 via the power supply trunk line 3f and the power supply trunk line 3e to the vehicle load 2c connected to the power distribution device 1c. At this time, because both the load current Ic and the load current Id pass through the power supply trunk line 3f, current is concentrated in the power supply trunk line 3f, resulting in increased transmission loss.

[0022] In the state shown in FIG. 2(a), the current path control device 8 acquires information on the load currents Ia to Id from the power distribution devices 1a to 1d, respectively, and calculates the magnitude of the current flowing through the power trunks 3a to 3f according to the load currents Ia to Id for each switching pattern of the switch elements 6a to 6h. Then, based on the calculated current values ​​in the power trunks 3a to 3f for each switching pattern and the preset conductor resistance values ​​of the power trunks 3a to 3f, the current path control device 8 calculates the total power loss (transmission loss) occurring in the power trunks 3a to 3f for each switching pattern. Based on this calculation result, the current path control device 8 selects the switching pattern of the switch elements 6a to 6h that minimizes power loss and transmits switch information Sa to Sd to the power distribution devices 1a to 1d, respectively, according to the selected switching pattern. This allows the current path control device 8 to control the switching of the switch elements 6a to 6h to disperse current concentrations occurring in the power trunks 3a to 3f, thereby switching the current path.

[0023] Note that when calculating the current values ​​of the power supply trunks 3a to 3f for each switching pattern of the switch elements 6a to 6h, the current path control device 8 does not necessarily need to calculate the current values ​​for all switching patterns. For example, for combinations of switch elements, such as switch elements 6b and 6c or switch elements 6f and 6g, where turning off one of the switch elements prevents current from flowing through the corresponding power supply trunks 3b and 3e, there is no need to duplicate the current value calculation for the switching pattern of that combination. Furthermore, in the state shown in FIG. 2(a), the load currents Ia and Ib distributed from the power distribution devices 1a and 1b to the vehicle loads 2a and 2b, respectively, are zero, so no current needs to flow through the power supply trunks 3a to 3c connected to the power distribution devices 1a and 1b. In this way, the switching patterns of the switch elements 6a to 6d connected to the power supply trunks 3a to 3c with zero current may be excluded from the current value calculation. Furthermore, for switching patterns that clearly result in increased power loss compared to the original state, such as when the current path is significantly longer than in FIG. 2(a), the current value calculation may be omitted. In addition to the above, it is possible to limit the opening and closing patterns of the switch elements 6a to 6h for which current values ​​are to be calculated by any method.

[0024] Through the above-described processing, the current path control device 8 selects, for example, an opening / closing pattern in which switch elements 6e and 6h are turned ON and switch elements 6f and 6g are turned OFF for load currents Ic and Id as a pattern that minimizes power loss. At this time, the current path control device 8 outputs switch information Sc to power distribution device 1c, switching element 6e ON and switch element 6f OFF, and outputs switch information Sd to power distribution device 1d, switching element 6g OFF and switch element 6h ON. The switch information Sc and Sd are transmitted from the current path control device 8 to power distribution devices 1c and 1d via communication lines 9c and 9d (see FIG. 1), respectively.

[0025] Upon receiving the switch information Sc, the power distribution device 1c switches the switch element 6e ON and the switch element 6f OFF according to the opening / closing pattern indicated by the switch information Sc. Furthermore, upon receiving the switch information Sd, the power distribution device 1d switches the switch element 6g OFF and the switch element 6h ON according to the opening / closing pattern indicated by the switch information Sd. This changes the state of the current path from that shown in FIG. 2(a) to that shown in FIG. 2(b). At this time, the power distribution device 1c distributes the current supplied from the DC / DC converter 5 via the power supply trunk line 3d to the vehicle load 2c as the load current Ic. Furthermore, the power distribution device 1d distributes the current supplied from the battery 4 via the power supply trunk line 3f to the vehicle load 2d as the load current Id. As a result, while current concentration occurs in the power supply trunk line 3f in the state shown in FIG. 2(a) before the current path is switched, in the state shown in FIG. 2(b) after the current path is switched, the current is dispersed between the power supply trunk line 3f and the power supply trunk line 3d, reducing transmission loss and temperature rise.

[0026] In the in-vehicle power net system 100 of this embodiment, the current path control device 8 controls the switching of the current paths so as to distribute the current flowing through the power supply trunks 3a to 3f based on the conductor resistance values ​​of the power supply trunks 3a to 3f and demand changes of the load currents Ia to Id flowing from the power distribution devices 1a to 1d to the vehicle loads 2a to 2d as described above. This reduces transmission loss throughout the in-vehicle power net system 100 and makes it possible to avoid local temperature increases due to current concentration.

[0027] 3 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a first embodiment of the present invention. As shown in FIG. 3, power distribution devices 1a to 1d of this embodiment detect values ​​of load currents Ia to Ib to be distributed to vehicle loads 2a to 2d, respectively, and transmit information indicating the detection results to a current path control device 8. The current path control device 8 of this embodiment also includes functional blocks of a path calculation unit 10 and an update determination unit 20. In the current path control device 8, these functional blocks are implemented, for example, by a CPU executing a predetermined program.

[0028] In the current path control device 8 of this embodiment, the path calculation unit 10 has a current path selection unit 11. The current path selection unit 11 selects a current path based on information on load currents Ia to Id acquired from the power distribution devices 1a to 1d. The path calculation unit 10 stores network configuration information 12 indicating the connection relationships between the power distribution devices 1a to 1d, the battery 4, and the DC / DC converter 5 via the power supply trunk lines 3a to 3f in the in-vehicle power net system 100, and network parameter information 13 indicating the conductor resistance values ​​of the power supply trunk lines 3a to 3f. The current path selection unit 11 selects a current path that distributes current within the in-vehicle power net system 100 based on the information on the load currents Ia to Id and this information stored in advance in the path calculation unit 10. Specifically, for example, as described above, the power loss due to the power supply trunk lines 3a to 3f in the entire in-vehicle power net system 100 that satisfies the load currents Ia to Id is calculated for each opening and closing pattern of the switch elements 6a to 6h, and the current path can be determined by selecting the opening and closing pattern that results in the smallest loss.

[0029] Update determination unit 20 monitors information on load currents Ia to Id transmitted from power distribution devices 1a to 1d at predetermined time intervals, and when a fluctuation of a predetermined value or more occurs in at least one of load currents Ia to Id, determines that there has been a change in demand for that load current, and issues a current path update instruction to path calculation unit 10. In response to this update instruction, path calculation unit 10 calculates a current path, current path selection unit 11 determines the subsequent current path, and current path control device 8 transmits switch information Sa to Sd to power distribution devices 1a to 1d, respectively.

[0030] 4 is a timing chart showing an example of the timing at which the update determination unit 20 issues a current path update instruction to the path calculation unit 10. In each of the timing charts in FIG. 4(a) to FIG. 4(d), from top to bottom, the relationship between the time changes in the load currents Ia, Ib, Ic, and Id and the timing at which the current path update instruction is issued is illustrated.

[0031] When the current path control device 8 is activated in the in-vehicle power net system 100, the update determination unit 20 acquires information on the load currents Ia to Id from the power distribution devices 1a to 1d and monitors the states of the load currents Ia to Id. As a result, as shown in FIG. 4D, for example, suppose that a fluctuation in the load current Id occurs at time t1, and the amount of this fluctuation (the amount of change in the current value per unit time) is equal to or greater than a predetermined threshold value Ith. In this case, the update determination unit 20 determines that time t1 is the timing to update the current path, and outputs an update instruction to the path calculation unit 10.

[0032] 4C, for example, if a fluctuation in the load current Ic occurs at time t2 and the amount of this fluctuation is less than the threshold value Ith, the update determination unit 20 determines that time t2 is not the timing to update the current path, and does not output an update instruction to the path calculation unit 10.

[0033] 4A, for example, fluctuations in load current Ia occur at times t3, t5, and t6, and the amounts of these fluctuations are all equal to or greater than threshold value Ith. In this case, update determination unit 20 determines that it is time to update the current path at each time and outputs an update instruction to path calculation unit 10. Similarly, as shown in FIG. 4B, for example, fluctuations in load current Ib occur at times t4 and t7, and the amounts of these fluctuations are all equal to or greater than threshold value Ith. In this case, update determination unit 20 determines that it is time to update the current path at each time and outputs an update instruction to path calculation unit 10.

[0034] When an update instruction is input from the update determination unit 20 based on the update determination described above, the path calculation unit 10 calculates the total power loss in the power supply trunk lines 3a-3f based on information on the load currents Ia-Id. If the result shows that power loss can be reduced by switching the current path, the path calculation unit 10 transmits switch information Sa-Sd to each power distribution device and switches the current path. That is, by including the update determination unit 20, the current path control device 8 of this embodiment determines that a current path update is necessary when the fluctuation amount of the load currents Ia-Id flowing from the power distribution devices 1a-1d to the vehicle loads 2a-2d exceeds a predetermined value, and the path calculation unit 10 executes current path calculation processing. Therefore, since the path calculation unit 10 does not need to constantly execute calculation processing, the processing load and power consumption of the CPU in the current path control device 8 can be reduced.

[0035] According to the first embodiment of the present invention described above, the following advantageous effects are achieved.

[0036] (1) The current path control device 8 is provided in an in-vehicle power net system 100, which is a vehicle power supply system including power distribution devices 1a-1d that distribute power to vehicle loads 2a-2d, power supply trunk lines 3a-3f that interconnect the power distribution devices 1a-1d, and a plurality of power supply devices (battery 4 and DC / DC converter 5) that can supply power to the power distribution devices 1a-1d via the power supply trunk lines 3a-3f. The current path control device 8 controls the current path when power is supplied from the battery 4 and the DC / DC converter 5 to the power distribution devices 1a-1d in the in-vehicle power net system 100. The current path control device 8 switches the current path of the in-vehicle power net system 100 based on demand changes in the load currents Ia-Id that flow from the power distribution devices 1a-1d to the vehicle loads 2a-2d. This configuration allows the in-vehicle power net system 100 to be realized as a low-loss, efficient vehicle power supply system.

[0037] (2) The current path control device 8 includes an update determination unit 20 that determines whether the current path needs to be updated, and a path calculation unit 10 that calculates the current path after switching. When the update determination unit 20 determines that the current path needs to be updated, the path calculation unit 10 calculates the current path after switching. This eliminates the need to constantly execute the processing of the path calculation unit 10, and as a result, the processing load and power consumption of the CPU in the current path control device 8 can be reduced.

[0038] (3) The update determination unit 20 determines whether or not the current path needs to be updated based on the amount of fluctuation in the load currents Ia to Id. This makes it possible to reliably determine the timing when the current path needs to be updated.

[0039] Second Embodiment Next, a second embodiment of the present invention will be described. In this embodiment, an example will be described in which the current path control device 8 changes the current path so as to reduce transmission loss in the entire in-vehicle power net system 100, further taking into consideration the environmental temperature when each power distribution device is mounted on a vehicle. The configuration of the in-vehicle power net system 100 in this embodiment is the same as that of the first embodiment. Therefore, in the following, this embodiment will be described using the configuration diagram of FIG. 1 described in the first embodiment as the configuration diagram of the in-vehicle power net system 100 according to this embodiment.

[0040] 5 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a second embodiment of the present invention. As shown in FIG. 5, power distribution devices 1a to 1d of this embodiment detect the values ​​of load currents Ia to Id distributed to vehicle loads 2a to 2d, respectively, and transmit information indicating the detection results to current path control device 8. Also, power distribution devices 1a to 1d detect the temperatures at the locations where they are installed as in-vehicle environmental temperatures Ta to Td, respectively, and transmit information indicating the detection results to current path control device 8. Current path control device 8 of this embodiment includes functional blocks of a path calculation unit 10 and an update determination unit 20. These functional blocks in current path control device 8 are implemented, for example, by a CPU executing a predetermined program.

[0041] In the current path control device 8 of this embodiment, the path calculation unit 10 includes a current path selection unit 11 and also a wire temperature calculation unit 14. The wire temperature calculation unit 14 estimates and calculates the temperatures of the power supply trunk lines 3a to 3f for each opening and closing pattern of the switch elements 6a to 6h based on information on the load currents Ia to Id and the environmental temperatures Ta to Td acquired from the power distribution units 1a to 1d. Specifically, for example, the wire temperature Twb of the power supply trunk line 3b connecting the power distribution unit 1a and the power distribution unit 1b can be calculated by the following formula (1): Twb=kb·Iab 2 +Tab...(1)

[0042] In the above formula (1), the first term on the right side represents the temperature rise due to Joule heat when current Iab flows through the power supply trunk line 3b. Here, constant kb is a constant corresponding to the conductor resistance value of the power supply trunk line 3b, which is determined by the wire thickness and material. Furthermore, the second term Tab on the right side represents a value indicating the ambient temperature at the location where the power supply trunk line 3b is installed inside the vehicle. Because the power supply trunk line 3b is connected between the power distribution device 1a and the power distribution device 1b, the value of Tab is determined by the ambient temperatures Ta and Tb obtained from these power distribution devices. As an example, the higher of the ambient temperatures Ta and Tb can be selected as Tab. Calculations can be performed for other power supply trunk lines in the same manner as in the above formula (1).

[0043] The current path selection unit 11 selects a current path so as to reduce the current of the power supply trunk line 3a-3f that has the highest temperature, based on the temperatures of the power supply trunk lines 3a-3f calculated by the electric wire temperature calculation unit 14, the network configuration information 12, and the network parameter information 13. In other words, the current path selection unit 11 selects a current path that distributes the current within the in-vehicle power net system 100, based on the conductor resistance of the power supply trunk lines 3a-3f indicated by the network parameter information 13, the environmental temperatures Ta-Td, and demand changes in the load currents Ia-Id that flow from the power distribution devices 1a-1d to the vehicle loads 2a-2d.

[0044] As in the first embodiment, the update determination unit 20 monitors information on the load currents Ia to Id at predetermined time intervals, and when a fluctuation of a predetermined value or more occurs in at least one of the load currents Ia to Id, issues an instruction to update the current path to the path calculation unit 10. In response to this update instruction, the path calculation unit 10 performs calculation of the current path.

[0045] According to the second embodiment of the present invention described above, the current path control device 8 switches the current paths of the in-vehicle power net system 100 so as to distribute the current flowing through the power supply trunks 3a to 3f based on the conductor resistance of the power supply trunks 3a to 3f, the ambient temperatures Ta to Td when the power distribution devices 1a to 1d are mounted on the vehicle, and demand changes in the load currents Ia to Id. Specifically, the current path control device 8 calculates the temperature of each power supply trunk 3a to 3f based on the conductor resistance of the power supply trunks 3a to 3f and the ambient temperatures Ta to Td, and switches the current path of the in-vehicle power net system 100 so as to reduce the current through the power supply trunk 3a to 3f with the highest temperature. This allows the current to be distributed so that the temperature of the power supply trunks 3a to 3f does not exceed the allowable temperature. As a result, power can be distributed from the power distribution devices 1a to 1d to the vehicle loads 2a to 2d so as to reduce deterioration of the electric wires caused by high temperatures in the power supply trunks 3a to 3f.

[0046] Generally, the ambient temperature inside a vehicle varies greatly depending on the location due to factors such as the influence of other surrounding devices. For example, the ambient temperature tends to be high under the front hood where the powertrain is located, while the ambient temperature tends to be low (or high) in the passenger compartment where an air conditioner is installed. Furthermore, the ambient temperature inside the vehicle also varies greatly depending on the vehicle's driving state, such as whether the vehicle is moving or stopped. Therefore, in order to properly manage the temperature state of the power supply trunk lines 3a to 3f, it is necessary to consider the ambient temperature at the location where each power supply trunk line is located. According to this embodiment, the temperature of the power supply trunk lines 3a to 3f can be estimated with high accuracy by taking the ambient temperature into account through the processing described above, thereby reliably preventing the wire temperatures of the power supply trunk lines 3a to 3f from becoming too high due to current concentration.

[0047] In this embodiment, for example, a temperature sensor is provided in each of the power distribution devices 1a to 1d, and the environmental temperatures Ta to Td around the power distribution devices 1a to 1d detected by the temperature sensor can be used to obtain the environmental temperature of the locations where the power supply trunk lines 3a to 3f are located. Other methods can also be used as long as the environmental temperatures of the locations where the power supply trunk lines 3a to 3f are installed can be obtained. For example, an outside air temperature sensor or a temperature sensor mounted on an air conditioner in the vehicle cabin can be used to estimate the environmental temperatures of the power supply trunk lines 3a to 3f.

[0048] Third Embodiment Next, a third embodiment of the present invention will be described. In this embodiment, an example will be described in which the timing to update the current path is determined in the current path control device 8 based on the operating states of the vehicle loads 2a to 2d. The configuration of the in-vehicle power net system 100 in this embodiment is the same as that in the first embodiment. Therefore, in the following, this embodiment will be described using the configuration diagram of FIG. 1 described in the first embodiment as the configuration diagram of the in-vehicle power net system 100 according to this embodiment.

[0049] FIG. 6 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a third embodiment of the present invention. As shown in FIG. 6, the power distribution devices 1a to 1d of this embodiment detect the values ​​of load currents Ia to Id distributed to the vehicle loads 2a to 2d, respectively, and transmit information indicating the detection results to the current path control device 8. Furthermore, a load switch 15 is provided between each of the load elements constituting the vehicle loads 2a to 2d, and the ON / OFF state of this load switch 15 is controlled to switch on or off the supply of power to each load element. The power distribution devices 1a to 1d of this embodiment transmit load operation information indicating the ON / OFF state of each load switch 15 to the current path control device 8. The current path control device 8 of this embodiment includes functional blocks of a path calculation unit 10 and an update determination unit 20. In the current path control device 8, these functional blocks are implemented, for example, by a CPU executing a predetermined program.

[0050] In the current path control device 8 of this embodiment, the update determination unit 20 monitors whether or not there is a change in the open / close state of any of the load switches 15, based on the load operation information transmitted from the power distribution devices 1a to 1d. If there is a change in the open / close state of any of the load switches 15, the update determination unit 20 determines that the operation of the vehicle loads 2a to 2d has changed, resulting in a change in current demand, and issues a current path update instruction to the path calculation unit 10. In response to this update instruction, the path calculation unit 10 calculates the current path, the current path selection unit 11 determines the subsequent current path, and the current path control device 8 transmits switch information Sa to Sd to the power distribution devices 1a to 1d, respectively.

[0051] Because the load currents Ia to Id change depending on the operating states of the vehicle loads 2a to 2d, changes in the load currents Ia to Id can also be detected using load operation information indicating the ON / OFF states of the load switches 15 in the power distribution devices 1a to 1d as described above. Therefore, in the current path control device 8 of this embodiment, the update determination unit 20 acquires load operation information indicating the operating states of the vehicle loads 2a to 2d connected to the power distribution devices 1a to 1d and uses this information to determine whether or not the current path needs to be updated.

[0052] In the current path control device 8 of this embodiment, the update determination unit 20 performs the above processing, and as in the first embodiment, the path calculation unit 10 executes path calculation at the timing when the current states of the power supply trunk lines 3a to 3f change. Therefore, it is not necessary to execute the calculation processing of the path calculation unit 10 all the time, and it is possible to reduce the processing load and power consumption of the CPU in the current path control device 8. Furthermore, by using the load operation information, circuit elements such as sensors that acquire values ​​of the load currents Ia to Id are not required in the power distribution devices 1a to 1d, and it is possible to perform update determination of the current path with a simpler configuration.

[0053] According to the third embodiment of the present invention described above, the update determination unit 20 determines whether or not the current path needs to be updated based on the operating states of the vehicle loads 2 a to 2 d. This makes it possible to determine the timing when the current path needs to be updated with a simpler configuration than in the first embodiment.

[0054] (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. In this embodiment, an example will be described in which the timing to update the current path is determined in the current path control device 8 based on the output current of the power supply device that supplies power to the vehicle loads 2a to 2d. Note that the configuration of the in-vehicle power net system 100 in this embodiment is the same as that in the first embodiment. Therefore, in the following, this embodiment will be described using the configuration diagram of FIG. 1 described in the first embodiment as the configuration diagram of the in-vehicle power net system 100 according to this embodiment.

[0055] FIG. 7 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a fourth embodiment of the present invention. As shown in FIG. 7 , a current path control device 8 according to this embodiment acquires current information Ibt and Idc indicating the output currents of the battery 4 (power supply device 1) and the DC / DC converter 5 (power supply device 2), which are power supply devices in an in-vehicle power net system 100. The current information Ibt can be acquired, for example, from a current sensor provided in the battery 4. The current information Idc can be acquired, for example, from a current sensor provided inside the DC / DC converter 5 or at the output section of the DC / DC converter 5. The current path control device 8 includes functional blocks of a path calculation unit 10 and an update determination unit 20. In the current path control device 8, these functional blocks are implemented, for example, by a CPU executing a predetermined program.

[0056] In the current path control device 8 of this embodiment, the update determination unit 20 monitors fluctuations in the current value indicated by the current information Ibt and the current information Idc, based on these current information. As a result, if there is a change in the current information Ibt or the current information Idc, it is determined that there has been a change in the current demand in each power distribution device, and an instruction to update the current path is issued to the path calculation unit 10. In response to this update instruction, the path calculation unit 10 calculates the current path, the current path selection unit 11 determines the subsequent current path, and the current path control device 8 transmits switch information Sa to Sd to the power distribution devices 1a to 1d, respectively.

[0057] Because the output currents of the battery 4 and DC / DC converter 5 vary depending on the operating states of the vehicle loads 2a-2d, changes in the load currents Ia-Id can also be detected using the current information Ibt and current information Idc. Therefore, in the current path control device 8 of this embodiment, the update determination unit 20 acquires the current information Ibt and current information Idc, which indicate the magnitude of the output currents of the battery 4 and DC / DC converter 5, respectively, and uses these information to determine whether a current path update is necessary. Because the battery 4 exists in both a discharged and a charged state, it is preferable that the current information Ibt represent the discharged and charged states with different values. In this way, the update determination unit 20 can detect the timing at which the charge / discharge state of the battery 4 switches from a discharged state to a charged state, or from a charged state to a discharged state, and issue an update instruction to the path calculation unit 10 according to that timing. The charge / discharge state of the battery 4 can be determined, for example, by detecting the direction of current flow using a current sensor provided in the battery 4.

[0058] In the current path control device 8 of this embodiment, the update determination unit 20 performs the above processing, and as in the first embodiment, the path calculation unit 10 executes path calculation at the timing when the current states of the power supply trunk lines 3a to 3f change. Therefore, it is not necessary to constantly execute the calculation processing of the path calculation unit 10, and it is possible to reduce the processing load and power consumption of the CPU in the current path control device 8. Furthermore, by using the current information Ibt and Idc output from the battery 4 and DC / DC converter 5, which are power supply devices, circuit elements such as sensors that acquire values ​​of the load currents Ia to Id are not required in the power distribution devices 1a to 1d, and it is possible to perform update determination of the current path with a simpler configuration.

[0059] According to the fourth embodiment of the present invention described above, the update determination unit 20 determines whether or not the current path needs to be updated based on fluctuations in the current values ​​of the power supply devices, that is, the battery 4 and the DC / DC converter 5. In this way, it is possible to determine the timing when the current path needs to be updated with a simpler configuration than in the first embodiment.

[0060] Fifth Embodiment Next, a fifth embodiment of the present invention will be described. In this embodiment, an example will be described in which the current path control device 8 determines the timing to update the current path based on vehicle travel plan information acquired from the outside. The configuration of the in-vehicle power net system 100 in this embodiment is the same as that in the first embodiment. Therefore, in the following, this embodiment will be described using the configuration diagram of FIG. 1 described in the first embodiment as the configuration diagram of the in-vehicle power net system 100 according to this embodiment.

[0061] FIG. 8 is a diagram showing the functional configuration of a power distribution device and a current path control device according to a fifth embodiment of the present invention. As shown in FIG. 8, the current path control device 8 of this embodiment acquires vehicle trip plan information from a trip planner 16 installed inside or outside the vehicle. The trip planner 16 is, for example, a car navigation device or an automatic driving control device, and outputs, as the trip plan information, information such as the roads on which the vehicle will travel and the traveling speed. The current path control device 8 includes the functional blocks of a route calculation unit 10 and an update determination unit 20. In the current path control device 8, these functional blocks are realized, for example, by a CPU executing a predetermined program.

[0062] In the current path control device 8 of this embodiment, the update determination unit 20 predicts future vehicle movements based on the driving plan information acquired from the driving plan device 16 and estimates the operating states of the vehicle loads 2a to 2d according to the prediction results. This allows the timing of changes in the load currents Ia to Id according to the operating states of the vehicle loads 2a to 2d to be predicted, and a current path update instruction is issued to the path calculation unit 10 in accordance with this change timing. Specifically, for example, by predicting the timing of vehicle steering or braking operations in accordance with a curve in the road from the curvature of the road, the distance traveled to the curve, the vehicle's traveling speed, and other factors included in the driving plan information, the timing of changes in the load currents Ia to Id can be predicted and a current path update instruction can be issued. In response to this update instruction, the path calculation unit 10 calculates the current path, the current path selection unit 11 determines the subsequent current path, and the current path control device 8 transmits switch information Sa to Sd to the power distribution devices 1a to 1d, respectively.

[0063] Because the operating states of the vehicle loads 2a to 2d change depending on the vehicle's driving state, future changes in the load currents Ia to Id can be predicted using the vehicle's driving plan information. Therefore, in the current path control device 8 of this embodiment, the update determination unit 20 acquires the vehicle's driving plan information from the driving plan device 16 and uses it to predict the timing of changes in the load current, thereby determining whether or not a current path update is necessary. This eliminates the need for the path calculation unit 10 to constantly execute its calculation process, thereby reducing the CPU processing load and power consumption in the current path control device 8. Furthermore, because a current path can be selected and prepared before the load currents Ia to Id actually change, power loss due to delays in switching the current path can be reduced.

[0064] According to the fifth embodiment of the present invention described above, the update determination unit 20 predicts the timing of changes in the load currents Ia to Id based on the vehicle's trip plan information transmitted from the trip planner 16, and determines whether or not the current path needs to be updated at the timing of the changes. This makes it possible to predict in advance the timing when the current path needs to be updated.

[0065] The following modifications may be applied to each of the first to fifth embodiments described above.

[0066] (Variation 1) In each of the first to fifth embodiments, an example of application to an in-vehicle power net system 100 having a system configuration in which four power distribution devices 1a to 1d are interconnected in a ring shape as shown in FIG. 1 has been described. However, the system configuration for applying the present invention is not limited to this. For example, as shown in FIG. 9( a), the present invention can also be applied to an in-vehicle power net system 100a having a system configuration in which power distribution device 1a is connected to power distribution devices 1b and 1c by power supply trunk lines 3b and 3c, respectively, and power distribution device 1d is connected to power distribution devices 1b and 1c by power supply trunk lines 3d and 3e, respectively. Furthermore, as shown in FIG. 9( b), the present invention can also be applied to an in-vehicle power net system 100b having a system configuration in which two power distribution devices 1a and 1b, each connected to a battery 4 and a DC / DC converter 5, are interconnected by power supply trunk line 3b. In addition to this, the present invention can be applied to any system configuration as long as it is a vehicle power supply system in which multiple power distribution devices and multiple power supply devices mounted on a vehicle are interconnected by power supply trunk lines.

[0067] (Variation 2) In each of the first to fifth embodiments, as shown in FIG. 1, the load currents Ia to Id are acquired by current detection elements 7a to 7d, which are respectively installed immediately before the branch points of the power supply lines from the power distribution devices 1a to 1d to the load elements of the vehicle loads 2a to 2d. However, the method of acquiring the load currents Ia to Id is not limited to this. For example, as shown in FIG. 10, the power distribution device 1a may be provided with a current detection element 7e that detects the current Iin flowing through the power supply trunk line 3a and a current detection element 7f that detects the current Iout flowing through the power supply trunk line 3b, and the load current Ia flowing to the vehicle load 2a may be calculated from the difference Iin - Iout between these currents. Any other method may also be used to acquire the load currents Ia to Id.

[0068] As described above, an in-vehicle power net system incorporating the present invention can realize a low-loss, efficient vehicle power supply system. Furthermore, if damage occurs to one of the power trunks, a power supply path can be secured using another power trunk, and maximum power supply can be continued without exceeding the allowable current of the power trunk. Furthermore, even if the demand current increases due to the replacement of in-vehicle devices with updated equipment or the addition of new in-vehicle equipment, an appropriate power supply path can be selected in response to the increase in demand current, allowing operation using the existing power supply network without replacing the power distribution device. Therefore, by standardizing the power supply network design across multiple vehicle models, it is also possible to reduce the man-hours required to optimize the layout of various vehicle loads, wiring, and the like within the vehicle for each vehicle model.

[0069] The present invention is not limited to the various embodiments and modifications described above, and includes various other modifications. For example, the above-described embodiments have been specifically described to clearly explain the present invention, and are not necessarily limited to those having all of the described configurations. Furthermore, part of the configuration of one embodiment can be replaced with part of the configuration of another embodiment. Furthermore, the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, part of the configuration of each embodiment can be deleted, and part of another configuration can be added or replaced with part of another configuration.

[0070] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0071] DESCRIPTION OF SYMBOLS 1a to 1d: Power distribution device, 2a to 2d: Vehicle load, 3a to 3f: Power supply main line, 4: Battery, 5: DC / DC converter, 6a to 6h: Switch element, 7a to 7f: Current detection element, 8: Current path control device, 9a to 9d: Communication line, 10: Path calculation unit, 11: Current path selection unit, 12: Network configuration information, 13: Network parameter information, 14: Electric wire temperature calculation unit, 15: Load switch, 16: Travel planning device, 20: Update determination unit, 100 to 100b: In-vehicle power net system, Ia to Ib: Load current, Sa to Sd: Switch information, Ta to Td: Environmental temperature.

Claims

1. A current path control device that is provided in a vehicle power supply system having a plurality of power distribution devices that each distribute power to a vehicle load, a power supply trunk that connects the plurality of power distribution devices to each other, and a plurality of power supply devices that can each supply power to the power distribution devices via the power supply trunk, and controls a current path when power is supplied from the power supply devices to the power distribution devices in the vehicle power supply system, and switches the current path based on changes in demand for the load current flowing from the power distribution device to the load.

2. A current path control device as claimed in claim 1, which switches the current path so as to distribute the current flowing through the power supply main line based on the conductor resistance of the power supply main line, the ambient temperature when the power distribution device is mounted on the vehicle, and changes in demand for the load current.

3. A current path control device as claimed in claim 2, wherein the temperature of each power supply trunk is calculated based on the conductor resistance and the environmental temperature, and the current path is switched so as to reduce the current in the power supply trunk having the highest temperature among the plurality of power supply trunks.

4. A current path control device as claimed in claim 1, comprising: an update determination unit which determines whether the current path needs to be updated; and a path calculation unit which calculates the current path after switching, wherein the path calculation unit calculates the current path after switching when the update determination unit determines that the current path needs to be updated.

5. A current path control device according to claim 4, wherein the update determination unit determines whether or not the current path needs to be updated based on an amount of fluctuation in the load current.

6. A current path control device according to claim 4, wherein the update determination unit determines whether or not the current path needs to be updated based on an operating state of the load.

7. A current path control device according to claim 4, wherein the update determination unit determines whether or not the current path needs to be updated based on a fluctuation in a current value of the power supply device.

8. A current path control device as claimed in claim 4, wherein the power supply device is a rechargeable secondary battery, and the update determination unit determines whether or not the current path needs to be updated based on the timing at which the power supply device switches between a charging state and a discharging state.

9. A current path control device according to claim 4, wherein the update determination unit predicts a timing of a change in the load current based on driving plan information of the vehicle, and determines whether or not the current path needs to be updated at the timing of the change.

10. A vehicle power supply system comprising: a current path control device as claimed in claim 1; a plurality of power distribution devices each distributing power to a load of a vehicle; a power supply trunk line interconnecting the plurality of power distribution devices; and a plurality of power supply devices each capable of supplying power to the power distribution devices via the power supply trunk line.

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