Deterioration detection device

Abstract

Provided is a deterioration determination device capable of more appropriately determining element deterioration.　A deterioration determination device (1) determines whether each of a first switch (33A) and a fuse (F) provided in a power path (11) that is a path for transmitting power from a power supply unit (10) to a load is in a deteriorated state or not. The power path (11) has a positive electrode-side power line (17) and a negative electrode-side power line (20). The first switch (33A) and the fuse (F) are provided in the negative electrode-side power line (20). The deterioration determination device (1) comprises: a first potential detection unit (39A) that detects a first potential on one end side of the first switch (33A) and a second potential on the other end side; a second potential detection unit (39B) that detects a first potential on one end side of the fuse (F) and a second potential on the other end side; and a control unit (15) that, on the basis of a potential difference (V1, V2) between the first potential and the second potential, determines whether each of the first switch (33A) and the fuse (F) is in a deteriorated state or not.

Description

[Technical Field]

[0001] The present disclosure relates to a deterioration determination device. [Background technology]

[0002] Patent Document 1 discloses a technique for optimizing the deterioration degree of a relay by adjusting the precharge time when an inverter is precharged by a precharge circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-78196 Summary of the Invention [Problem to be solved by the invention]

[0004] One known method for determining whether a device satisfies the required performance is to determine whether the device satisfies the required performance by predetermining an upper limit on the number of times that current is passed through the device and comparing the number of times that current is passed through the device with the upper limit. However, this method does not take into account the magnitude of the current flowing through the device or the potential difference between both terminals of the device. Therefore, this method may not be able to accurately determine whether the device satisfies the required performance in a manner that is appropriate for the actual device usage.

[0005] The present disclosure has been made in light of the above-mentioned circumstances, and aims to provide a degradation determination device that can more appropriately determine degradation of an element. [Means for solving the problem]

[0006] The deterioration determination device of the present disclosure includes: A deterioration determination device that determines whether an element provided in a power path, which is a path that transmits power from a power supply unit to a load, is in a deteriorated state, the power path includes a positive power line connected to a positive terminal of the power supply unit and a negative power line connected to a negative terminal of the power supply unit, the element is provided on the negative power line, a potential detection unit that detects a first potential on one end side of the element and a second potential on the other end side of the element; and a control unit that determines whether the element is in a deteriorated state based on a potential difference between the first potential and the second potential. [Effects of the Invention]

[0007] According to the present disclosure, deterioration of an element can be determined more appropriately. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram illustrating a vehicle power supply system including a deterioration determination device according to the first embodiment. [Figure 2] FIG. 2 is a flowchart showing an example of control by the control unit in the deterioration determining device of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A deterioration determination device that determines whether an element provided in a power path, which is a path that transmits power from a power supply unit to a load, is in a deteriorated state, the power path includes a positive power line connected to a positive terminal of the power supply unit and a negative power line connected to a negative terminal of the power supply unit, the element is provided on the negative power line, a potential detection unit that detects a first potential on one end side of the element and a second potential on the other end side of the element; a control unit that determines whether the element is in a deteriorated state based on a potential difference between the first potential and the second potential.

[0011] In the deterioration determination device (1), since the element is installed on the negative power line, even if the voltage applied to the element fluctuates at a predetermined rate, the fluctuation range is smaller than when the voltage on the positive power line fluctuates at a predetermined rate. Therefore, it is easy to keep the fluctuation range of the calculated resistance value of the element installed on the negative power line small.

[0012] (2) the element is a first element; a second element different from the first element is provided on the positive power line, further comprising a temperature detection unit that detects the temperature of each of the first element and the second element; The deterioration determination device according to (1), wherein the control unit determines whether the second element is in a deteriorated state based on the potential difference and the temperature value detected by the temperature detection unit.

[0013] The potential difference between the two terminals of the second element fluctuates more widely than that of the first element, which raises concerns about the possibility of greater variations in resistance value. For this reason, the deterioration determination device (2) can easily determine whether the second element is in a deteriorated state by using a temperature detection unit.

[0014] (3) The deterioration determination device according to (2), wherein the element is at least one of a relay and a fuse.

[0015] There is a concern that if the electrical characteristics of relays and fuses change due to deterioration, they may no longer be able to cut off the power path as specified. However, the deterioration determination device (3) can determine whether each relay and fuse is in a deteriorated state, making it easier to address such concerns before they arise.

[0016] (4) the element and the second element are the relay; The deterioration determination device of (3), wherein a precharge circuit is connected to the power path so as to be in parallel with the element.

[0017] In the deterioration determination device of (4), relays connected in parallel to precharge circuits are prone to deterioration because inrush currents tend to flow easily. Therefore, by measuring the resistance of relays connected in parallel to precharge circuits, the deterioration level of relays that are prone to deterioration can be determined.

[0018] (5) The deterioration determination device according to any one of (1) to (4), wherein the control unit performs abnormality response processing when determining that the element is in a deteriorated state.

[0019] The deterioration determination device (5) can easily take appropriate measures in response to deterioration of the element by performing abnormality response processing.

[0020] [Details of the embodiments of the present disclosure] Specific examples of the present disclosure will be described below with reference to the drawings. However, the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0021] <Embodiment 1> [Configuration of the deterioration determination device] 1 is a power supply system mounted on a vehicle, and includes a power supply unit 10, a power path 11, a system main relay 33, and a deterioration determination device 1. The deterioration determination device 1 includes a temperature detection unit 37, a current detection unit 38, a potential detection unit 39, and a control unit 15. The potential detection unit 39 includes a first potential detection unit 39A and a second potential detection unit 39B. The vehicle power supply system 100 is configured to supply power from the power supply unit 10 to a load 35 via the power path 11, which is a path along which power is transmitted between the power supply unit 10 and the load 35.

[0022] The power supply unit 10 is a battery capable of supplying power to the load 35. The power supply unit 10 may be, for example, a lead battery or a battery pack configured by combining a plurality of unit cells, such as lithium ion batteries or nickel-metal hydride batteries, in series.

[0023] The power path 11 includes a positive power line 17 and a negative power line 20. The positive power line 17 is electrically connected to the positive terminal of the power supply unit 10. The output voltage of the power supply unit 10 is applied to the positive power line 17. The negative power line 20 is electrically connected to the negative terminal of the power supply unit 10. The negative power line 20 has a lower potential than the positive power line 17. The negative terminal of the power supply unit 10 is electrically connected to, for example, a metal body of a vehicle and has the same potential as the metal body of the vehicle. The output voltage of the power supply unit 10 corresponds to the potential difference between the positive terminal and the negative terminal. The power path 11 is a path for transmitting power from the power supply unit 10 to a load 35. A fuse F, which is a first element, is provided in the negative power line 20. The fuse F cuts off the power to the negative power line 20 when excessive current flows through the negative power line 20. The fuse F may be, for example, a thermal fuse.

[0024] In the present disclosure, "electrically connected" preferably means a configuration in which the connection objects are connected in a mutually conductive state (a state in which a current can flow) so that the potentials of both connection objects are equal. However, this configuration is not limited to this. For example, "electrically connected" may also mean a configuration in which the connection objects are connected in a state in which the two connection objects can be electrically connected with an electrical component interposed between them.

[0025] A load 35 is electrically connected to the positive power line 17 and the negative power line 20. The load 35 is an in-vehicle electronic component, and is applicable to products such as electric components, ECUs, and ADAS target components. In the first embodiment, the load 35 includes an inverter 35A having a capacitor 35C and a motor 35B. The capacitor 35C smoothes the voltage based on the power supply unit 10 and supplies the smoothed voltage to the inverter 35A. The inverter 35A is electrically connected to the power path 11. The inverter 35A generates an AC voltage (e.g., three-phase AC) from a DC voltage based on the voltage supplied from the power supply unit 10 and supplies the AC voltage to the motor 35B. The motor 35B is, for example, a main motor. The motor 35B rotates based on the power supplied from the power supply unit 10 and applies a rotational force to the wheels of the vehicle. The current output from the positive terminal of the power supply unit 10 flows through the positive power line 17, the load 35, the negative power line 20, and the negative terminal of the power supply unit 10 in this order.

[0026] The system main relay 33 is disposed between the power supply unit 10 and the load 35, interposed between the positive power line 17 and the negative power line 20. The system main relay 33 includes a first switch 33A, which is a first element and a relay, a second switch 33B, which is a second element and a relay, and a parallel switching path 33C. That is, the first element includes the first switch 33A and a fuse F. The second switch 33B is an element different from the first switch 33A. The first switch 33A and the second switch 33B are, for example, mechanical relay switches having internal contacts that physically switch between a contacted state and a separated state. The parallel switching path 33C is a so-called precharge circuit. The parallel switching path 33C includes a resistor 33D and a third switch 33E, which is a relay connected in series to the resistor 33D. The third switch 33E is a mechanical relay switch having the same configuration as the first switch 33A and the second switch 33B. The third switch 33E is a so-called pre-charge relay.

[0027] The first switch 33A is provided on the negative power line 20 opposite the power supply unit 10, with a fuse F sandwiched therebetween. The second switch 33B is provided on the positive power line 17. The resistor 33D and the third switch 33E of the parallel switching path 33C are electrically connected to the negative power line 20 so as to be in parallel with the first switch 33A. The first switch 33A, the second switch 33B, and the third switch 33E are controlled by a predetermined control device C (hereinafter simply referred to as the control device C) to switch between an ON state and an OFF state. The first switch 33A, the second switch 33B, and the third switch 33E switch the power path 11 between a conductive state and a cut-off state by switching between an ON state and an OFF state.

[0028] The temperature detection units 37 are provided individually for the first switch 33A and the second switch 33B, and detect the temperatures of the contacts in the first switch 33A and the second switch 33B when the corresponding first switch 33A and second switch 33B are in the on state. The temperature detection units 37 have a first temperature detection unit 37A provided for the first switch 33A and a second temperature detection unit 37B provided for the second switch 33B. The first temperature detection unit 37A and the second temperature detection unit 37B output temperature values ​​indicating the detected temperatures. The control unit 15 determines the temperatures of the contacts in the first switch 33A and the second switch 33B when they are in the on state, based on the temperature values ​​of the first temperature detection unit 37A and the second temperature detection unit 37B.

[0029] The current detection unit 38 is provided on the negative power line 20 closer to the power supply unit 10 than the first switch 33A. The current detection unit 38 has, for example, a resistor and a differential amplifier, and is configured to be able to output a value indicating the current flowing through the negative power line 20 (specifically, an analog voltage corresponding to the value of the current flowing through the negative power line 20) as a current value A. In other words, the current detection unit 38 detects the current state of the current flowing through the power path 11 as a current value A.

[0030] The first potential detection unit 39A is configured as, for example, a potential detection circuit. The first potential detection unit 39A is configured to detect a first potential at a terminal on one end of the first switch 33A, which is the terminal on the power supply unit 10 side, and a second potential at a terminal on the other end, which is the terminal on the load 35 side, and to output a potential difference V1 between these first and second potentials. In other words, the first potential detection unit 39A detects the potential difference V1 between both the terminals on the power supply unit 10 side and the terminals on the load 35 side of the first switch 33A (the terminals on both the side where power is supplied to the first switch 33A and the terminals on the side where power is output from the first switch 33A).

[0031] The second potential detection unit 39B is configured, for example, as a potential detection circuit similar to the first potential detection unit 39A. The second potential detection unit 39B is configured to detect a first voltage at one end of the fuse F, which is the terminal on the power supply unit 10 side, and a second potential at the other end of the fuse F, which is the terminal on the load 35 side, and output a potential difference V2 between these first and second potentials. In other words, the second potential detection unit 39B detects the potential difference V2 between the terminals of the fuse F on the power supply unit 10 side and the load 35 side (the terminals on both the side where power is supplied to the fuse F and the terminals where power is output from the fuse F).

[0032] The potential differences V1 and V2 between the first potential and the second potential may be values ​​calculated by an analog circuit (e.g., a differential amplifier circuit), or may be values ​​calculated by a digital circuit after AD converting the first potential and the second potential, respectively.

[0033] The control unit 15 is configured as, for example, a microcomputer and includes a CPU and a storage unit 15D configured by a ROM, a RAM, a non-volatile memory, etc. The control unit 15 includes a resistance value calculation unit 15A, a deterioration detection unit 15B, and a notification function unit 15C.

[0034] The resistance value calculation unit 15A is configured to receive the current value A, potential difference V1, and potential difference V2 from the current detection unit 38, the first potential detection unit 39A, and the second potential detection unit 39B, respectively. The resistance value calculation unit 15A calculates the resistance value R1 of the first switch 33A and the resistance value R2 of the fuse F based on these values ​​(current value A, potential differences V1 and V2). For example, the resistance value R1 of the first switch 33A is calculated by dividing the potential difference V1 by the current value A. The resistance value R2 of the fuse F is calculated by dividing the potential difference V2 by the current value A. In other words, the control unit 15 calculates the resistance values ​​R1 and R2 of the first element, the first switch 33A and the fuse F, based on the potential differences V1 and V2 between the first potential and the second potential. For example, the first switch 33A and the fuse F have the characteristic that the resistance values ​​R1 and R2 gradually increase as they are repeatedly energized and deenergized. That is, the control unit 15 calculates the resistance values ​​R1 and R2 to determine the degree of deterioration of each of the first switch 33A and the fuse F.

[0035] The deterioration detection unit 15B is configured to be able to execute a deterioration determination process, which is a process of comparing the resistance value R1 calculated by the resistance value calculation unit 15A with a resistance threshold value Th11 stored in the memory unit 15D of the control unit 15, and comparing the resistance value R2 calculated by the resistance value calculation unit 15A with a resistance threshold value Th12 stored in the memory unit 15D of the control unit 15.

[0036] For example, the deterioration detection unit 15B is configured to output a deterioration signal Sd when it determines that the resistance value R1 exceeds the resistance threshold Th11 or that the resistance value R2 exceeds the resistance threshold Th12. The deterioration signal Sd is output when either the first switch 33A or the fuse F is in a deteriorated state. That is, the control unit 15 determines that the first switch 33A is in a deteriorated state when the resistance value R1 exceeds the resistance threshold Th11, and determines that the fuse F is in a deteriorated state when the resistance value R2 exceeds the resistance threshold Th12. If the deterioration detection unit 15B determines in the deterioration determination process that the resistance value R1 is equal to or less than the resistance threshold Th11 and the resistance value R2 is equal to or less than the resistance threshold Th12, the deterioration detection unit 15B does not output the deterioration signal Sd. In this case, the control unit 15 determines that the first switch 33A and the fuse F are not in a deteriorated state. In this way, the control unit 15 determines whether each of the first switch 33A and the fuse F is in a deteriorated state.

[0037] The notification function unit 15C is configured to perform an abnormality response process by transmitting information to an external device (not shown) such as a BMS (battery management system) based on the degradation signal Sd input from the degradation detection unit 15B. That is, the control unit 15 performs the abnormality response process when the resistance value R1 exceeds the resistance threshold value Th11 and the first switch 33A is determined to be in a degraded state, or when the resistance value R2 exceeds the resistance threshold value Th12 and the fuse F is determined to be in a degraded state.

[0038] [Regarding control in the control unit] Next, an example of control executed by the control unit 15 will be described with reference to Fig. 2 etc. For example, in a vehicle equipped with the vehicle power supply system 100, when the start switch is off, the first switch 33A, the second switch 33B of the system main relay 33, and the third switch 33E of the parallel switching path 33C are maintained in an off state. At this time, the power path 11 is in a cutoff state in which the supply of power from the power supply unit 10 to the load 35 is cut off.

[0039] From this state, first, step S1 is executed to switch the start switch from off to on. Next, when the process proceeds to step S2, an on signal Son (see FIG. 1) is output from the control device C, and switching control is executed in which the first contactor 33A, the second contactor 33B, and the third contactor 33E are switched from off to on based on the on signal Son. Specifically, the switching control is a control in which the first contactor 33A is turned off while the second contactor 33B and the third contactor 33E are turned on to start energizing the power path 11, and then the first contactor 33A is switched on while the second contactor 33B and the third contactor 33E are maintained in the on state. In other words, the first contactor 33A is switched from off to on after the second contactor 33B.

[0040] When the second switch 33B and the third switch 33E are turned on, current begins to flow through the power path 11. Because the resistor 33D is connected in series with the third switch 33E, the current begins to flow slowly through the power path 11 so as to gradually increase.

[0041] Furthermore, when the first switch 33A is switched to the ON state, the power path 11 enters a conductive state that allows power to be supplied from the power supply unit 10 to the load 35. When the first switch 33A switches to the ON state, an inrush current immediately flows through the first switch 33A. At this time, a current rise occurs, in which the current value A flowing through the power path 11 rises sharply. In this way, switching control is executed, and the power path 11 begins to conduct electricity or a current rise occurs. The inrush current continues to flow for a predetermined short time after the first switch 33A switches to the ON state, and after the predetermined short time has elapsed, the current flowing through the first switch 33A settles so as to remain within a predetermined range that is smaller than the magnitude of the inrush current. In this way, the first switch 33A switches to the ON state, and a current flows through the power path 11.

[0042] Then, the process proceeds to step S3. The control unit 15 has a timer function, and starts measuring a predetermined short period from the time when the current value A changes from 0 to a predetermined magnitude. The predetermined short period is the time it takes for the current flowing through the first switch 33A to settle within a predetermined range that is smaller than the magnitude of the inrush current.

[0043] Then, when the process proceeds to step S4, the control unit 15 determines whether a predetermined short time has elapsed since the current value A in the power path 11 changed from 0 to a predetermined magnitude. Step S4 is a process for waiting for the predetermined short time to elapse, thereby waiting for the current flowing through the first switch 33A to settle within a predetermined range that is smaller than the magnitude of the inrush current. For example, if the control unit 15 determines in step S4 that the predetermined short time has not elapsed since the current value A in the power path 11 changed from 0 to the predetermined magnitude (No in step S4), the process proceeds again to step S3. When the process proceeds again to step S3, the control unit 15 advances the count of a timer included in the control unit 15, and then repeats the process of step S4 again.

[0044] Then, in step S4, if the control unit 15 determines that a predetermined short time has elapsed since the current value A in the power path 11 changed from 0 to a predetermined value (Yes in step S4), the process proceeds to step S5. In step S5, the control unit 15 determines whether the current value A remains within a predetermined range. For example, the control unit 15 is configured to compare the current value A input from the current detection unit 38 with a current threshold value Th13 and an upper current threshold value Th14 that is greater than the current threshold value Th13, both of which are stored in the memory unit 15D of the control unit 15. For example, the control unit 15 is configured to use its own timer function to determine whether the state in which the current value A is greater than or equal to the current threshold value Th13 and less than the upper current threshold value Th14 has continued for a predetermined time (i.e., whether fluctuations in the current flowing through the power path 11 have settled down). In step S5, if the control unit 15 determines that the state in which the magnitude of the current value A is equal to or greater than the current threshold Th13 and smaller than the upper limit current threshold Th14 has not continued for a predetermined time (No in step S5), the processing of step S5 is repeated.

[0045] In step S5, if control unit 15 determines that the state in which current value A is equal to or greater than current threshold value Th13 and smaller than upper current threshold value Th14 has continued for a predetermined time (Yes in step S5), control unit 15 proceeds to step S6. In step S6, control unit 15 causes resistance value calculation unit 15A to calculate resistance values ​​R1 and R2 based on the current value A and potential differences V1 and V2 input from current detection unit 38, first potential detection unit 39A, and second potential detection unit 39B, respectively. Then, control unit 15 proceeds to step S7.

[0046] When the process proceeds to step S7, the control unit 15 executes a deterioration determination process in which the deterioration detection unit 15B compares the resistance value R1 with a resistance threshold value Th11 and compares the resistance value R2 with a resistance threshold value Th12. The control unit 15 executes the deterioration determination process in which the resistance values ​​R1 and R2 when switching control is executed by the control device C are compared with the resistance threshold values ​​Th11 and Th12. For example, in the deterioration determination process, if the control unit 15 determines that the magnitude of the resistance value R1 is equal to or greater than the resistance threshold value Th11 or that the magnitude of the resistance value R2 is equal to or greater than the resistance threshold value Th12 (Yes in step S7), the process proceeds to step S8, and the deterioration detection unit 15B outputs a deterioration signal Sd.

[0047] On the other hand, if the controller 15 determines in the degradation determination process that the resistance value R1 is smaller than the resistance threshold value Th11 and the resistance value R2 is smaller than the resistance threshold value Th12 (No in step S7), the controller 15 does not output the degradation signal Sd and ends the process shown in FIG. 2. In this manner, the controller 15 calculates the resistance value R1 of the first switch 33A using the potential difference V1 between the first potential on one end side of the first switch 33A and the second potential on the other end side of the first switch 33A. The controller 15 then compares the resistance value R1 with the resistance threshold value Th11 to determine whether the first switch 33A is in a degraded state. The controller 15 then calculates the resistance value R2 of the fuse F using the potential difference V2 between the first potential on one end side of the fuse F and the second potential on the other end side of the fuse F. The controller 15 then compares the resistance value R2 with the resistance threshold value Th12 to determine whether the fuse F is in a degraded state.

[0048] Next, when the deterioration signal Sd is input to the notification function unit 15C, the notification function unit 15C transmits information to an external device (not shown). That is, the notification function unit 15C of the control unit 15 performs abnormality response processing to notify the outside that either the resistance value R1 exceeds the resistance threshold value Th11 and the first switch 33A is in a deteriorated state, or the resistance value R2 exceeds the resistance threshold value Th12 and the fuse F is in a deteriorated state. In this way, the processing shown in FIG. 2 ends.

[0049] 2, the control unit 15 performs a process of comparing the temperature value from the first temperature detection unit 37A with the temperature value from the second temperature detection unit 37B. Through this process, the control unit 15 compares the temperature of the first switch 33A with the temperature of the second switch 33B. For example, the control unit 15 may be configured to estimate that the degree of deterioration of the second switch 33B is greater than the degree of deterioration of the first switch 33A when it determines that the temperature value from the second temperature detection unit 37B is greater than the temperature value from the first temperature detection unit 37A (i.e., the temperature of the second switch 33B is greater than the temperature of the first switch 33A).

[0050] The control unit 15 may also be configured to calculate the temperature difference between the first switch 33A and the second switch 33B using the temperature value from the second temperature detection unit 37B and the temperature value from the first temperature detection unit 37A. Furthermore, the control unit 15 may be configured to perform temperature correction on the calculated resistance value R1 of the first switch 33A using the temperature difference, and then calculate the resistance value of the second switch 33B. In other words, the control unit 15 determines whether the second switch 33B (second element) is in a deteriorated state based on the resistance value R1 calculated based on the potential difference V1 and the temperature value detected by the temperature detection unit 37.

[0051] Next, the effects of this configuration will be illustrated. The deterioration determination device 1 determines whether a first switch 33A and a fuse F (element) provided on a power path 11, which is a path for transmitting power from a power supply unit 10 to a load 35, are in a deteriorated state. The power path 11 has a positive power line 17 connected to a positive terminal of the power supply unit 10 and a negative power line 20 connected to a negative terminal of the power supply unit 10. The first switch 33A and the fuse F (element) are provided on the negative power line 20. The deterioration determination device 1 includes a first potential detection unit 39A, a second potential detection unit 39B, and a control unit 15. The first potential detection unit 39A detects a first potential on one end of the first switch 33A and a second potential on the other end of the first switch 33A. The second potential detection unit 39B detects a first potential on one end of the fuse F and a second potential on the other end of the fuse F. The control unit 15 determines whether or not each of the first switch 33A and the fuse F is in a deteriorated state based on the potential differences V1 and V2 between the first potential and the second potential.

[0052] In the deterioration determination device 1, the first switch 33A and the fuse F are provided on the negative power line 20. Therefore, even if the voltages applied to the first switch 33A and the fuse F fluctuate at a predetermined rate of fluctuation, the fluctuation range is smaller than the fluctuation range of the voltage on the positive power line 17. Therefore, it is easy to keep the fluctuation range of the calculated resistance values ​​R1, R2 of the first switch 33A and the fuse F provided on the negative power line 20 small.

[0053] The first switch 33A and the fuse F are first elements, and a second switch 33B (second element) different from the first switch 33A and the fuse F is provided on the positive power line 17. Furthermore, the deterioration determination device 1 includes a temperature detection unit 37 that detects the temperatures of the first switch 33A and the second switch 33B. The control unit 15 determines whether the second switch 33B is in a deteriorated state based on the potential difference V1 and the temperature value detected by the temperature detection unit 37.

[0054] The potential difference between both terminals of the second switch 33B fluctuates more widely than the first switch 33A, and there is a concern that the resistance value of the second switch 33B may vary more. For this reason, the deterioration determination device 1 can use the temperature detection unit 37 to simply determine whether the second switch 33B is in a deteriorated state.

[0055] The elements are a first switch 33A and a fuse F.

[0056] There is a concern that if the electrical characteristics of the first switch 33A and the fuse F change due to deterioration, they may not be able to cut off the power path 11 as specified. However, the deterioration determination device 1 determines whether each of the first switch 33A and the fuse F is in a deteriorated state, making it easier to address such concerns before they arise.

[0057] The first element is a first switch 33A which is a relay, and the second element is a second switch 33B which is also a relay. A parallel switching path 33C (precharge circuit) is connected to the power path 11 so as to be in parallel with the first switch 33A (first element).

[0058] In the deterioration determination device 1, the first switch 33A connected in parallel to the parallel switching path 33C is prone to deterioration because an inrush current easily flows through it. Therefore, by measuring the resistance value R1 of the first switch 33A connected in parallel to the parallel switching path 33C, it is possible to determine the degree of deterioration of the first switch 33A, which is prone to deterioration.

[0059] The control unit 15 performs abnormality response processing when either the resistance value R1 of the first switch 33A exceeds the resistance threshold value Th11 and determines that the first switch 33A is in a deteriorated state, or the resistance value R2 of the fuse F exceeds the resistance threshold value Th12 and determines that the fuse F is in a deteriorated state.

[0060] According to this configuration, by performing the abnormality response process, it is easy to take a response appropriate to the deterioration of either the first switch 33A or the fuse F.

[0061] [Another embodiment of the present disclosure] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive.

[0062] Unlike the first embodiment, the voltage detection unit may be connected to any location that can be considered to have the same potential as the terminals on both sides of the first switch.

[0063] Unlike the first embodiment, the notification function unit may be configured as a display unit such as a lamp or a display device, and may be configured to notify by display. The notification function unit may be configured as an audio device such as a speaker, and may be configured to notify by audio.

[0064] Unlike the first embodiment, the resistance value calculation unit, the deterioration detection unit, and the notification function unit may be configured as separate information processing devices (separate microcomputers, etc.).

[0065] Unlike the first embodiment, the control unit and the control device may be configured as one microcomputer.

[0066] Unlike the first embodiment, the degradation determination process may be performed after determining that the rate of increase in the current in the power path is equal to or less than a certain value. For example, the change in current Ki in the power path per unit time is calculated using the following formula 1: Ki = |A1-A2| / ΔT... (Formula 1) where A1 is the current value A1 detected this time by the current detection unit, A2 is the current value A2 detected last time by the current detection unit, and ΔT is the period ΔT over which the current detection unit repeatedly detects the current value. The current value A2 may be stored, for example, in the RAM of the control unit. The change Ki is the absolute value of the difference between the current values ​​A1 and A2 divided by the period ΔT. For example, if the change Ki remains smaller than a threshold value stored in the memory of the control unit for a predetermined period of time, it may be determined that the fluctuation in the current flowing in the power path has stabilized, and the resistance value of the first switch may then be calculated.

[0067] Unlike the first embodiment, the third switch may not be provided. In this case, the execution of the switching control causes a current rise in which the value of the current flowing through the power path rises sharply.

[0068] Unlike the first embodiment, table data that defines resistance values ​​corresponding to current values ​​and voltage values ​​may be stored in advance in a storage unit, and the resistance values ​​corresponding to the current values ​​and voltage values ​​may be adopted from the table data.

[0069] Unlike the first embodiment, a configuration may be adopted in which the potential difference of only one of the first switch and the fuse is detected to determine whether or not only one of them is in a deteriorated state.

[0070] The deterioration state may be the potential difference itself, the resistance value, or a value obtained by calculation using the potential difference or the resistance value as a variable. [Explanation of symbols]

[0071] 1...Deterioration determination device 10...Power supply section 11…Power line 15...Control unit 15A...Resistance value calculation section 15B…Deterioration detection unit 15C…Notification function section 15D…Storage section 17...Positive power line (power path) 20...Negative power line (power path) 33...System main relay 33A…1st switch 33B…Second switch 33C...Parallel switching path (precharge circuit) 33D...Resistor 33E…Third switch 35...Load 37...Temperature detection unit 37A...First temperature detection unit (temperature detection unit) 37B... Second temperature detection unit (temperature detection unit) 38...Current detection unit 39... Potential detection unit 39A...First potential detection unit (potential detection unit) 39B...Second potential detection unit (potential detection unit) 100...Vehicle power supply system A, A1, A2...Current value C…control device F...Fuse Ki…Amount of change R1, R2...resistance value Sd...degraded signal Son...On signal Th11, Th12...Resistance threshold Th13: Current threshold Th14: Upper limit current threshold V1,V2…potential difference ΔT…period

Claims

1. A deterioration determination device that determines whether an element provided in a power path, which is a path that transmits power from a power supply unit to a load, is in a deteriorated state, the power path includes a positive power line connected to a positive terminal of the power supply unit and a negative power line connected to a negative terminal of the power supply unit, the element is provided on the negative power line, a potential detection unit that detects a first potential on one end side of the element and a second potential on the other end side of the element; a control unit that determines whether the element is in a deteriorated state based on a potential difference between the first potential and the second potential, The control unit determines whether the element is in a deteriorated state based on the potential difference between the first potential and the second potential after determining that the current value in the power path has remained within a range greater than or equal to a current threshold and less than an upper current threshold for a predetermined period of time.

2. the element is a first element, a second element different from the first element is provided on the positive power line, further comprising a temperature detection unit that detects the temperature of each of the first element and the second element; The deterioration determining device according to claim 1 , wherein the control unit determines whether the second element is in a deteriorated state based on the potential difference and the temperature value detected by the temperature detection unit.

3. The deterioration determining device according to claim 2 , wherein the element is at least one of a relay and a fuse.

4. the first element and the second element are the relay, 4. The deterioration determining device according to claim 3, wherein a precharge circuit is connected to the power path in parallel with the first element.

5. The deterioration determination device according to claim 1 , wherein the control unit performs an abnormality response process when it is determined that the element is in a deteriorated state.

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