Deterioration determination device

Abstract

To provide a deterioration determination device that can operate a relay for a longer period of time by appropriately determining the deterioration state of the relay.SOLUTION: A deterioration determination device 1 is used in an in-vehicle system 100 including a power path 11, which is a path for transmitting power from a power source unit 10 to a load 35, and a first switch 33A and a second switch 33B provided on the power path 11. The deterioration determination device 1 includes a constant current circuit 16 that controls a current flowing through the first switch 33A and the second switch 33B to be constant, and a control unit 15 (control device C2) that controls the constant current circuit 16. The control unit 15 measures the resistance values R1 and R2 between both terminals of the first switch 33A and the second switch 33B while controlling the constant current circuit 16 such that the current flowing through the first switch 33A and the second switch 33B is constant.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a deterioration determining device. [Background technology]

[0002] Patent Document 1 discloses a technique for a control device that estimates the deterioration level of a relay. This control device estimates the deterioration level of a relay based on a history of the number of times the relay is turned on and off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-164189 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of the relay disclosed in Patent Document 1, even if the contacts in the relay are not worn out and the required performance is satisfied (i.e., the relay is usable), when the number of opening and closing times reaches an upper limit, it may be determined that the required performance is no longer satisfied. For this reason, a method of operating a relay while further enhancing its durability is desired.

[0005] The present disclosure has been made based on the above-mentioned circumstances, and aims to provide a deterioration determination device that can appropriately determine the deterioration state of a relay, thereby enabling the relay to be operated for a longer period of time. [Means for solving the problem]

[0006] The deterioration determination device of the present disclosure is A deterioration determination device for use in an in-vehicle system including a power path that is a path for transmitting power from a power supply unit to a load and a relay provided in the power path, a constant current circuit for controlling a current flowing through the relay at a constant level; A control unit that controls the constant current circuit; Equipped with The control unit measures a resistance value between both terminals of the relay while controlling the constant current circuit so that the current flowing through the relay is constant. Effect of the Invention

[0007] According to the present disclosure, the deterioration state of a switch can be appropriately determined, thereby enabling the switch to be operated for a longer period of time. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram illustrating an in-vehicle system including a deterioration determining device according to the first embodiment. [Diagram 2] FIG. 2 is a flowchart showing an example of control by the control unit in the deterioration determining device of the first embodiment. [Diagram 3] FIG. 3 is a circuit diagram illustrating an in-vehicle system including the deterioration determining device of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] In the following, embodiments of the present disclosure are listed and illustrated.

[0010] (1) A deterioration determination device for use in an in-vehicle system including a power path that is a path for transmitting power from a power supply unit to a load and a relay provided in the power path, a constant current circuit for controlling a current flowing through the relay at a constant level; A control unit that controls the constant current circuit; Equipped with The control unit measures a resistance value between both terminals of the relay while controlling the constant current circuit so that a current flowing through the relay is constant.

[0011] In the deterioration determination device of (1), the current flowing through the power path is kept constant by the constant current circuit, so the current flowing through the relay is also kept constant. When the relay is in this state, the resistance value between both terminals of the relay is measured, so the effect on the resistance value of the relay caused by the heat generated by the current flow is also kept constant. Therefore, with this configuration, the resistance value of the relay can be measured in a manner that suppresses variations in heat generation due to differences in the magnitude of the current. Here, "constant" is not limited to the case where the current value flowing through the relay is constant, but also includes a state in which the magnitude of the current is maintained within a predetermined range.

[0012] (2) The deterioration determination device of (1), wherein the control unit performs an abnormality response process when a determination value based on the measured resistance value exceeds a threshold value.

[0013] The deterioration determination device of (2) performs an abnormality response process, making it easy to take appropriate action in response to the resistance value exceeding the threshold value (i.e., the relay is deteriorated).

[0014] (3) The deterioration determination device according to (2), wherein the control unit determines the determination value based on the resistance value measured after a predetermined time has elapsed since a current began to flow through the relay.

[0015] When current begins to flow through a relay, the magnitude of the current fluctuates due to an inrush current, and then the current fluctuations settle down. Therefore, the deterioration determination device of (3) waits a predetermined time after current begins to flow before measuring the resistance value, thereby eliminating the effect of fluctuations in the magnitude of the current.

[0016] (4) The control unit is configured to continuously measure the resistance value, The deterioration determination device according to (3), wherein after the predetermined time has elapsed, the control unit specifies the determination value based on the resistance value whose fluctuation rate with respect to the previously measured resistance value is equal to or less than a fluctuation threshold value.

[0017] (4) The deterioration determination device can further eliminate fluctuations in the resistance value after the inrush current has settled down. Here, the fluctuation rate is calculated by dividing the currently measured resistance value by the previously measured resistance value, and the closer it is to 1, the smaller the fluctuation rate is, and the farther it is from 1, the larger the fluctuation rate is.

[0018] (5) The control unit is configured to continuously measure the resistance value, The control unit determines the determination value based on the resistance value whose fluctuation rate with respect to the previously measured resistance value is equal to or less than a fluctuation threshold value.

[0019] The deterioration determining device of (5) can determine the deterioration of the relay by using the resistance value from which fluctuations have been eliminated.

[0020] (6) Further, a temperature detection unit is provided to detect a temperature of the relay, The deterioration determination device according to (2), wherein the control unit determines the determination value based on the measured resistance value and the temperature value of the relay detected by the temperature detection unit.

[0021] (6) The deterioration determination device enables processing that eliminates the effect of temperature on the measured resistance value.

[0022] (7) The power supply unit is a battery, the in-vehicle system includes a charging inlet to which a charging connector provided outside the vehicle is connected; The relay is provided between the charging inlet and the battery, the constant current circuit is provided between the relay and the charging inlet, The control unit measures the resistance value while controlling the constant current circuit so as to flow a constant current to the relay and the battery based on power supplied from outside the vehicle via the charging inlet.

[0023] The deterioration determination device of (7) can measure the resistance value of the relay while controlling the current flowing through the relay to a constant value by utilizing a constant current circuit used for charging from outside the vehicle.

[0024] (8) The deterioration determination device according to any one of (1) to (6), wherein a precharge circuit is connected to the power path so as to be in parallel with the relay.

[0025] In the deterioration determination device of (8), a relay connected in parallel to a precharge circuit is susceptible to inrush current and therefore is susceptible to deterioration. Therefore, by measuring the resistance of a relay connected in parallel to a precharge circuit, it is possible to determine whether a relay that is susceptible to deterioration is in a deteriorated state.

[0026] <Embodiment 1> [Configuration of the Deterioration Determination Device] The in-vehicle system 100 shown in Fig. 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, a constant current circuit 16, and a control unit 15. The deterioration determination device 1 is used in the in-vehicle system 100. The potential detection unit 39 includes a first potential detection unit 39A and a second potential detection unit 39B. The in-vehicle system 100 is configured to be able to supply power from the power supply unit 10 to the 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.

[0027] 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 formed by combining a plurality of unit cells, such as lithium ion batteries or nickel hydride batteries, in series.

[0028] 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 a high potential 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 a low potential terminal of the power supply unit 10. The negative power line 20 has a lower potential than the positive power line 17. The low potential 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 high potential terminal and the low potential terminal. The power path 11 is a path for transmitting power from the power supply unit 10 to the load 35. A fuse F is provided in the positive power line 17. The fuse F cuts off the current flowing through the positive power line 17 when an excessive current flows through the positive power line 17. The fuse F may be, for example, a thermal fuse.

[0029] 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 is not limited to this configuration. For example, "electrically connected" may mean a configuration in which the two connection objects are connected in a state in which the two connection objects can be conductive with an electric component interposed between them.

[0030] 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 it 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 it 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 provides a rotational force to the wheels of the vehicle. The current output from the high potential terminal of the power supply unit 10 flows through the positive power line 17, the load 35, the negative power line 20, and the low potential terminal of the power supply unit 10 in this order.

[0031] The system main relay 33 is provided 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 has a first switch 33A which is a relay, a second switch 33B which is a relay, and a parallel switching path 33C. The first switch 33A and the second switch 33B are mechanical relay switches having contacts therein that are physically switched between a contacted state and a separated state, for example. The parallel switching path 33C has 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 a configuration similar to that of the first switch 33A and the second switch 33B. The third switch 33E is a so-called precharge relay.

[0032] The first switch 33A is provided on the positive power line 17 on the opposite side of the power supply unit 10, with the fuse F interposed therebetween. The second switch 33B is provided on the negative power line 20. The resistor 33D and the third switch 33E of the parallel switching path 33C are electrically connected to the positive power line 17 so as to be in parallel with the first switch 33A. The parallel switching path 33C is a so-called precharge circuit. The first switch 33A, the second switch 33B, and the third switch 33E are controlled by a predetermined control device C1 (hereinafter, also simply referred to as the control device C1) so as to switch between an on state and an off state. The control device C1 is configured as, for example, a microcomputer, and includes a CPU, a ROM, a RAM, a non-volatile memory, and the like. The control device C1 is included in the configuration of the control unit 15. The first switch 33A, the second switch 33B, and the third switch 33E switch between an on state and an off state, thereby switching the power path 11 between a conductive state and a cut-off state.

[0033] The temperature detection units 37 are provided for the first switch 33A and the second switch 33B, respectively, 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 the detected temperatures as temperature values ​​indicating the temperatures.

[0034] The current detection unit 38 is provided on the negative power line 20 closer to the power supply unit 10 than the second switch 33B. 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 the current value A.

[0035] 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 the power supply unit 10 side, which is a terminal on one end of the first switch 33A, and a second potential at a terminal on the load 35 side, which is a terminal on the other end, and output a potential difference V1 between the first potential and the second potential. In other words, the first potential detection unit 39A detects a potential difference V1 between both terminals on the power supply unit 10 side and the load 35 side of the first switch 33A (terminals on both sides of the side where power is supplied to the first switch 33A and the side where power is output).

[0036] The second potential detection section 39B is configured as a potential detection circuit similar to that of the first potential detection section 39A, for example. The second potential detection section 39B is configured to detect a first voltage at a terminal on the power supply unit 10 side, which is one end terminal of the second switch 33B, and a second potential at a terminal on the load 35 side, which is the other end terminal, and output a potential difference V2 between the first potential and the second potential. In other words, the second potential detection section 39B detects a potential difference V2 between both terminals on the power supply unit 10 side and the load 35 side of the second switch 33B (terminals on both sides of the side where power is supplied to the second switch 33B and the side where power is output).

[0037] The potential differences V1, 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 conversion of the first potential and the second potential, respectively.

[0038] The constant current circuit 16 may be, for example, a known on-board charger. The constant current circuit 16 is electrically connected to a positive power line 17 and a negative power line 20. The constant current circuit 16 is electrically connected in parallel to a load 35. A charging inlet 18 is electrically connected to the constant current circuit 16. The constant current circuit 16 is provided between a first switch 33A and a second switch 33B and the charging inlet 18. The first switch 33A and the second switch 33B are provided between the charging inlet 18 and the power supply unit 10 (battery). The charging inlet 18 is provided in the in-vehicle system 100.

[0039] For example, a charging connector 19 of a charging device (not shown) installed outside the vehicle is connected to charging inlet 18 of a vehicle with the start switch in an off state. The charging device is, for example, configured with an AC commercial power source. At this time, when charging connector 19 is connected to charging inlet 18, AC power is supplied from the charging device to constant current circuit 16. Based on the AC power from the charging device, constant current circuit 16 causes a DC current of constant magnitude to flow through power path 11 (first switch 33A and second switch 33B). In this way, constant current circuit 16 controls the current flowing through first switch 33A and second switch 33B to be constant.

[0040] The constant current circuit 16 is configured to be controlled by a predetermined control device C2 (hereinafter, simply referred to as the control device C2). As a result, the constant current circuit 16 is controlled so that the current flowing through each of the first switch 33A provided on the positive power line 17 and the second switch 33B provided on the negative power line 20 is constant based on the power supplied from outside the vehicle by the control device C2. The control device C2 is configured as, for example, a microcomputer and includes a CPU, a ROM, a RAM, a non-volatile memory, and the like. The control device C2 is included in the configuration of the control unit 15. The control device C2 is also configured to be able to detect that the charging connector 19 is connected to the charging inlet 18. The control device C2 is configured to be able to notify the control device C1 and the control unit 15 described later that the charging connector 19 is connected to the charging inlet 18.

[0041] The control unit 15 is configured as, for example, a microcomputer and includes a CPU, a ROM, a RAM, a storage unit 15D including 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.

[0042] The resistance value calculation unit 15A is configured to receive the current value A, the potential difference V1, and the 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 second switch 33B based on these values ​​(current value A, potential differences V1, V2). In the resistance value calculation unit 15A, calculating and obtaining the resistance values ​​R1, R2 is the same as measuring the resistance values ​​R1, R2. For example, the resistance value R1 of the first switch 33A is obtained by dividing the potential difference V1 by the current value A. The resistance value R2 of the second switch 33B is obtained by dividing the potential difference V2 by the current value A. That is, the control unit 15 calculates the resistance values ​​R1, R2 of the first switch 33A and the second switch 33B based on the potential differences V1, V2 between the first potential and the second potential. For example, the first switch 33A and the second switch 33B have a characteristic that the resistance values ​​R1, R2 gradually increase when the current is turned on and off repeatedly. The control unit 15 calculates the resistance values ​​R1, R2 to grasp the degree of deterioration of the first switch 33A and the second switch 33B.

[0043] The control unit 15 has a function of storing the resistance values ​​R1 and R2 calculated in the resistance value calculation unit 15A in the memory unit 15D. In detail, when the control unit 15 stores the resistance values ​​R1 and R2 calculated in the resistance value calculation unit 15A in the memory unit 15D, the control unit 15 erases the resistance values ​​R1 and R2 already stored in the memory unit 15D. The resistance value calculation unit 15A is configured to calculate the fluctuation rate Rv1 of the resistance value R1 by dividing the resistance value R1 measured this time by the resistance value R1 (the resistance value R1 measured last time) stored in the memory unit 15D, and to calculate the fluctuation rate Rv2 of the resistance value R2 by dividing the resistance value R2 measured this time by the resistance value R2 (the resistance value R2 measured last time) stored in the memory unit 15D. For example, when the fluctuation rates Rv1 and Rv2 are 1, the resistance values ​​R1 and R2 have not changed since the last measurement. Furthermore, when the fluctuation rates Rv1, Rv2 are greater than 1 or less than 1, it indicates that the resistance values ​​R1, R2 have fluctuated since the previous measurement, and the further away from 1 the values ​​are, the greater the fluctuation rates Rv1, Rv2 are. For example, the control unit 15 is configured to store an upper fluctuation threshold Th13 and a lower fluctuation threshold Th14 for comparison with the fluctuation rates Rv1, Rv2 in the memory unit 15D. For example, a predetermined value greater than 1 is adopted for the upper fluctuation threshold Th13, and a predetermined value less than 1 and greater than 0 is adopted for the lower fluctuation threshold Th14.

[0044] Furthermore, the resistance value calculation unit 15A is configured to perform temperature correction on the resistance values ​​R1 and R2 based on the temperature value from the second temperature detection unit 37B and the temperature value from the first temperature detection unit 37A to calculate the judgment values ​​Jv1 and Jv2. The first switch 33A and the second switch 33B have a characteristic that the temperature rises when a current flows through them, and the resistance values ​​R1 and R2 change according to the temperature rise. Therefore, the resistance value calculation unit 15A performs temperature correction on the calculated resistance values ​​R1 and R2 to calculate the judgment values ​​Jv1 and Jv2 that eliminate the influence of the temperature rise from the resistance values ​​R1 and R2. For example, the temperature correction may be a method in which the judgment values ​​Jv1 and Jv2 are determined by a predetermined calculation formula with the temperature value detected by the temperature detection unit 37 as a variable, or table data that associates the resistance values ​​R1 and R2 with the judgment values ​​Jv1 and Jv2.

[0045] The deterioration detection unit 15B is configured to be able to execute a deterioration determination process, which is a process of comparing a determination value Jv1 calculated by the resistance value calculation unit 15A with a resistance threshold value Th11 stored in the storage unit 15D, and comparing a determination value Jv2 calculated by the resistance value calculation unit 15A with a resistance threshold value Th12 stored in the storage unit 15D.

[0046] For example, the deterioration detection unit 15B is configured to output a deterioration signal Sd when it is determined that the judgment value Jv1 exceeds the resistance threshold Th11 or the judgment value Jv2 exceeds the resistance threshold Th12. The deterioration signal Sd is output when the first switch 33A or the second switch 33B is in a deteriorated state. That is, the control unit 15 determines that the first switch 33A is in a deteriorated state when the judgment value Jv1 exceeds the resistance threshold Th11, and determines that the second switch 33B is in a deteriorated state when the judgment value Jv2 exceeds the resistance threshold Th12. When the deterioration detection unit 15B determines in the deterioration determination process that the magnitude of the judgment value Jv1 is equal to or less than the resistance threshold Th11 and the magnitude of the judgment value Jv2 is equal to or less than the resistance threshold Th12, it does not output the deterioration signal Sd. In this case, the control unit 15 determines that the first switch 33A and the second switch 33B are not in a deteriorated state. In this manner, the control unit 15 determines whether or not each of the first switch 33A and the second switch 33B is in a deteriorated state.

[0047] 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 input of the deterioration signal Sd from the deterioration detection unit 15B. That is, the control unit 15 performs the abnormality response process when either the determination value Jv1 exceeds the resistance threshold value Th11 or the determination value Jv2 exceeds the resistance threshold value Th12.

[0048] [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 in-vehicle 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 the 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.

[0049] From this state, first, step S1 is executed, and the control device C2 included in the configuration of the control unit 15 determines whether or not the charging connector 19 is connected to the charging inlet 18. If the control device C2 determines in step S1 that the charging connector 19 is not connected to the charging inlet 18 (No in step S1), the process of step S1 is repeated. If the control device C2 determines in step S1 that the charging connector 19 is connected to the charging inlet 18 (Yes in step S1), the process proceeds to step S2. At this time, the control device C2 transmits to the control device C1 and the control unit 15 that the charging connector 19 is connected to the charging inlet 18.

[0050] Next, when the process proceeds to step S2, the control device C1 outputs an on signal Son (see FIG. 1) to the first switch 33A, the second switch 33B, and the third switch 33E to execute switching control for switching the system main relay 33 from an off state to an on state. The switching control is executed based on the information transmitted from the control device C2 that the charging connector 19 is connected to the charging inlet 18. In the switching control, the first switch 33A is switched to an on state while the second switch 33B and the third switch 33E are switched to an off state to start energizing the power path 11, and then the first switch 33A is switched to an on state while maintaining the second switch 33B and the third switch 33E in an on state. In other words, the first switch 33A is switched from an off state to an on state after the second switch 33B.

[0051] When the second switch 33B and the third switch 33E are turned on, the power path 11 starts to be energized. Since the resistor 33D is connected in series to the third switch 33E, the current starts to flow gently in the power path 11 so that the current gradually increases. Furthermore, when the first switch 33A is turned on, the power path 11 is in a conductive state that allows the constant current circuit 16 to supply power to the power supply unit 10. Prior to the switching control, a switch (not shown) provided in the conductive path leading to the load 35 is turned off so that the charging current does not flow from the constant current circuit 16 to the load 35.

[0052] When the first switch 33A is switched 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 suddenly. In this manner, the switching control is executed, and the start of current flow in the power path 11 or a current rise occurs.

[0053] The inrush current continues to flow for a predetermined short time after the first switch 33A is switched to the on state, and after the predetermined short time has elapsed, the current flowing through the first switch 33A settles to remain within a predetermined range smaller than the magnitude of the inrush current. Thus, the first switch 33A is switched to the on state, and a current flows through the power path 11.

[0054] When the process proceeds to step S3, the control unit 15 determines whether or not a charging current has started to flow from the constant current circuit 16 to the power path 11. The control unit 15 is notified by the control device C2 that the charging connector 19 is connected to the charging inlet 18. When the control unit 15 detects that the current value A has changed from 0 to a predetermined magnitude after being notified that the charging connector 19 is connected to the charging inlet 18, it determines that a charging current has started to flow from the constant current circuit 16 to the power path 11 (Yes in step S3). For example, in step S3, the control unit 15 detects that an inrush current has started to flow, thereby determining that a charging current has started to flow to the power path 11. When the control unit 15 determines in step S3 that a charging current has not started to flow from the constant current circuit 16 to the power path 11 (No in step S3), the control unit 15 repeats the process of step S3.

[0055] Then, the process proceeds to step S4. The control unit 15 has a timer function, and starts measuring a predetermined short period of time from when the current value A changes from 0 to a predetermined magnitude. The predetermined short period of time 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.

[0056] When the process proceeds to step S5, the control unit 15 judges whether or not a predetermined short time has elapsed since the charging current from the constant current circuit 16 started to flow to the power path 11 (the current value A changed from 0 to a predetermined magnitude). Step S5 is a process for waiting for the predetermined short time to elapse, so as to wait 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, when the control unit 15 judges in step S5 that the predetermined short time has not elapsed since the current value A changed from 0 to the predetermined magnitude (No in step S5), the control unit 15 proceeds again to step S4. When the process proceeds again to step S4, the control unit 15 advances the count of a timer included in the control unit 15, and then repeats the process of step S5 again.

[0057] In step S5, when the control unit 15 determines that a predetermined short time has elapsed since the charging current from the constant current circuit 16 started to flow through the power path 11 (Yes in step S5), the process proceeds to step S6. In step S6, the control unit 15 calculates the resistance values ​​R1 and R2 in the resistance value calculation unit 15A based on the current value A input from the current detection unit 38, the first potential detection unit 39A, and the second potential detection unit 39B, and the potential differences V1 and V2. In this way, the control unit 15 controls the constant current circuit 16 so as to pass a constant current to the first switch 33A and the second switch 33B (relays) and the power supply unit 10 (battery) side based on the power supplied from outside the vehicle via the charging inlet 18. Then, the resistance values ​​R1 and R2 are measured after a predetermined time has elapsed since the current started to flow through the power path 11. Then, the process proceeds to step S7.

[0058] When the process proceeds to step S7, the control unit 15 determines in the resistance value calculation unit 15A whether the fluctuation rates Rv1, Rv2 of the resistance values ​​R1, R2 are equal to or lower than a predetermined upper fluctuation threshold Th13 and equal to or higher than a lower fluctuation threshold Th14.

[0059] In step S7, when the control unit 15 determines that the fluctuation rates Rv1 and Rv2 are greater than the upper fluctuation threshold Th13 or less than the lower fluctuation threshold Th14 (No in step S7), the process proceeds to step S8, where the control unit 15 resets the count of the timer included in the control unit 15. At this time, the control unit 15 erases the resistance values ​​R1 and R2 already stored in the storage unit 15D, and stores the resistance values ​​R1 and R2 calculated this time in the storage unit 15D. After that, the control unit 15 executes the process of step S6 again to calculate the resistance values ​​R1 and R2, and then executes step S7 again to newly calculate the fluctuation rates Rv1 and Rv2. Then, the control unit 15 repeats the process of determining whether the fluctuation rates Rv1 and Rv2 are equal to or less than the upper fluctuation threshold Th13 and equal to or more than the lower fluctuation threshold Th14. In other words, the control unit 15 is configured to continuously measure the resistance values ​​R1 and R2.

[0060] In step S7, when the control unit 15 determines that the fluctuation rates Rv1, Rv2 are equal to or lower than the upper fluctuation threshold Th13 and equal to or higher than the lower fluctuation threshold Th14 (Yes in step S7), the process proceeds to step S9. Then, the control unit 15 advances the count of its own timer to continue measuring the predetermined time. At this time, the control unit 15 erases the resistance values ​​R1, R2 already stored in the memory unit 15D, and stores the currently calculated resistance values ​​R1, R2 in the memory unit 15D.

[0061] Then, when the process proceeds to step S10, the control unit 15 judges whether or not a predetermined time has elapsed. Specifically, the control unit 15 judges whether or not the result of continuing counting by the timer included in the control unit 15 exceeds the predetermined time. If the control unit 15 judges in step S10 that the predetermined time has not elapsed (No in step S10), the process proceeds again to step S6.

[0062] In step S10, when the control unit 15 determines that the predetermined time has elapsed (Yes in step S10), the process proceeds to step S11. Yes in step S10 means that the fluctuation rates Rv1 and Rv2 of the resistance values ​​R1 and R2 have remained equal to or lower than the upper fluctuation threshold Th13 and equal to or higher than the lower fluctuation threshold Th14 for the predetermined time, and the fluctuations of the fluctuation rates Rv1 and Rv2 have stabilized.

[0063] When proceeding to step S11, the control unit 15, in the resistance value calculation unit 15A, performs temperature correction on the resistance values ​​R1, R2 based on the temperature value from the second temperature detection unit 37B and the temperature value from the first temperature detection unit 37A, to calculate the judgment values ​​Jv1, Jv2.

[0064] In this way, after a predetermined time has elapsed since the charging current started to flow through the power path 11, the control unit 15 determines the judgment values ​​Jv1 and Jv2 based on the current resistance values ​​R1 and R2 whose fluctuation rates Rv1 and Rv2 with respect to the previously measured resistance values ​​R1 and R2 are equal to or lower than the upper fluctuation threshold Th13 and equal to or higher than the lower fluctuation threshold Th14, and the temperature values ​​of the first switch 33A and the second switch 33B detected by the temperature detection unit 37. In other words, the control unit 15 measures the resistance values ​​R1 and R2 after a predetermined time has elapsed since the current started to flow through the first switch 33A and the second switch 33B while controlling the constant current circuit 16 so that the current flowing through the first switch 33A and the second switch 33B is constant, and determines the judgment values ​​Jv1 and Jv2 based on the measured resistance values ​​R1 and R2.

[0065] When the process proceeds to step S12, the control unit 15 executes a degradation determination process in which the deterioration detection unit 15B compares a judgment value Jv1 calculated by temperature correction with a resistance threshold Th11, and compares a judgment value Jv2 calculated by temperature correction with a resistance threshold Th12. For example, in the degradation determination process, when it is determined that the judgment value Jv1 is equal to or greater than the resistance threshold Th11 or that the judgment value Jv2 is equal to or greater than the resistance threshold Th12 (Yes in step S12), the process proceeds to step S13, and the deterioration detection unit 15B outputs a degradation signal Sd.

[0066] On the other hand, if it is determined in the deterioration determination process that the determination value Jv1 is smaller than the resistance threshold Th11 and the determination value Jv2 is smaller than the resistance threshold Th12 (No in step S12), the process shown in FIG. 2 is terminated.

[0067] 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 an abnormality response process to notify the outside that the device is in a deteriorated state when the judgment values ​​Jv1 and Jv2 based on the resistance values ​​R1 and R2 exceed the resistance threshold values ​​Th11 and Th12. In this way, the process shown in FIG. 2 is completed.

[0068] Next, the effects of this configuration will be illustrated. The deterioration determination device 1 is used in an in-vehicle system 100 including a power path 11, which is a path for transmitting power from a power source unit 10 to a load 35, and a first switch 33A and a second switch 33B provided on the power path 11. The deterioration determination device 1 includes a constant current circuit 16 that controls the current flowing through the first switch 33A and the second switch 33B to be constant, and a control unit 15 (control device C2) that controls the constant current circuit 16. The control unit 15 measures resistance values ​​R1 and R2 between both terminals of the first switch 33A and the second switch 33B while controlling the constant current circuit 16 so that the current flowing through the first switch 33A and the second switch 33B is constant.

[0069] In the deterioration determination device 1, the current flowing through the power path 11 is constant due to the constant current circuit 16, so the current flowing through the first switch 33A and the second switch 33B is also constant. Since the resistance values ​​R1 and R2 are measured when the first switch 33A and the second switch 33B are in such a state, the influence of the heat generated by the first switch 33A and the second switch 33B caused by the current flowing on the resistance values ​​R1 and R2 is also constant. Therefore, according to this configuration, the resistance values ​​R1 and R2 of the first switch 33A and the second switch 33B can be measured in a state in which the variation in heat generation due to differences in the magnitude of the current is suppressed. Here, "constant" is not limited to the case where the value of the current flowing through the first switch 33A and the second switch 33B is a single value, but also includes a state in which the magnitude of the current is maintained within a predetermined range.

[0070] The control unit 15 performs an abnormality response process when the determination value Jv1 based on the measured resistance value R1 exceeds the resistance threshold value Th11, or when the determination value Jv2 based on the measured resistance value R2 exceeds the resistance threshold value Th12. Therefore, by performing the abnormality response process, the deterioration determination device 1 can easily take a response appropriate to the fact that the resistance values ​​R1, R2 have exceeded the resistance threshold values ​​Th11, Th12 (i.e., the first switch 33A and the second switch 33B have deteriorated).

[0071] The control unit 15 determines the judgment values ​​Jv1, Jv2 based on the resistance values ​​R1, R2 measured after a predetermined time has elapsed since the current started to flow through the first switch 33A and the second switch 33B. When the current starts to flow through the first switch 33A and the second switch 33B, the magnitude of the current fluctuates due to an inrush current, and the current fluctuations thereafter settle down. Therefore, the deterioration judgment device 1 waits a predetermined time after the current starts to flow before measuring the resistance values ​​R1, R2, and therefore can eliminate the influence of fluctuations in the magnitude of the current.

[0072] The control unit 15 is configured to continuously measure the resistance values ​​R1, R2. After a predetermined time has elapsed since the current started to flow through the first switch 33A and the second switch 33B, the control unit 15 specifies the judgment values ​​Jv1, Jv2 based on the resistance values ​​R1, R2 whose fluctuation rates Rv1, Rv2 with respect to the previously measured resistance values ​​R1, R2 are equal to or lower than the upper fluctuation threshold Th13 and equal to or higher than the lower fluctuation threshold Th14. With this configuration, it is possible to further eliminate the fluctuation of the resistance values ​​R1, R2 after the inrush current has settled down. Here, the fluctuation rates Rv1, Rv2 are calculated by the resistance value R1 measured this time / the resistance value R1 measured last time, and the resistance value R2 measured this time / the resistance value R2 measured last time. The closer the fluctuation rates Rv1, Rv2 are to 1, the smaller the fluctuation of the resistance values ​​R1, R2 over time becomes, and the farther they are from 1, the larger the fluctuation of the resistance values ​​R1, R2 over time becomes.

[0073] The control unit 15 is configured to continuously measure the resistance values ​​R1, R2. The control unit 15 specifies the judgment values ​​Jv1, Jv2 based on the resistance values ​​R1, R2 whose fluctuation rates Rv1, Rv2 with respect to the previously measured resistance values ​​R1, R2 are equal to or lower than the upper fluctuation threshold Th13 and equal to or higher than the lower fluctuation threshold Th14. With this configuration, the deterioration of the first switch 33A and the second switch 33B can be judged by using the resistance values ​​R1, R2 from which fluctuations have been eliminated.

[0074] Furthermore, the deterioration determination device 1 includes a first temperature detection unit 37A and a second temperature detection unit 37B that detect the temperatures of the first switch 33A and the second switch 33B. The control unit 15 specifies the determination values ​​Jv1 and Jv2 based on the measured resistance values ​​R1 and R2 and the respective temperature values ​​of the first switch 33A and the second switch 33B detected by the first temperature detection unit 37A and the second temperature detection unit 37B. This configuration enables processing that eliminates the effect of temperature on the measured resistance values ​​R1 and R2.

[0075] The power supply unit 10 is a battery, and the in-vehicle system 100 includes a charging inlet 18 to which a charging connector 19 provided outside the vehicle is connected, and a first switch 33A and a second switch 33B are provided between the charging inlet 18 and the battery. A constant current circuit 16 is provided between the first switch 33A and the second switch 33B and the charging inlet 18. The control unit 15 (control device C2) controls the constant current circuit 16 so as to pass a constant current to the first switch 33A, the second switch 33B and the battery side based on power supplied from outside the vehicle via the charging inlet 18. At the same time, the control unit 15 (control device C2) measures resistance values ​​R1 and R2 between both terminals of each of the first switch 33A and the second switch 33B. According to this configuration, the resistance values ​​R1, R2 of the first switch 33A and the second switch 33B can be measured while controlling the current flowing through the first switch 33A and the second switch 33B to a constant value by utilizing the constant current circuit 16 used for charging from outside the vehicle.

[0076] 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. According to this configuration, the first switch 33A to which the parallel switching path 33C is connected in parallel is susceptible to inrush current flow and is therefore susceptible to deterioration. Therefore, by measuring the resistance value R1 of the first switch 33A to which the parallel switching path 33C is connected in parallel, it is possible to know whether the first switch 33A, which is susceptible to deterioration, is in a deteriorated state.

[0077] <Embodiment 2> The deterioration determination device 2 of the second embodiment is different from the first embodiment in that the load 36 is connected to the power path 11 via a constant current circuit 116, but is otherwise common to both embodiments. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0078] The deterioration determination device 2 provided in the in-vehicle system 200 shown in FIG. 3 is provided with a load 36 in addition to the load 35. For example, a device that can be driven by a low current, such as a heater or an air conditioner, is applied to the load 36. The load 36 is electrically connected to the positive power line 17 and the negative power line 20 via a constant current circuit 116. A known constant current circuit is used for the constant current circuit 116. The constant current circuit 116 is connected in parallel to the load 35. The deterioration determination device 2 measures the resistance values ​​R1 and R2 of the first switch 33A and the second switch 33B while the start switch of the vehicle is turned on and the vehicle is stopped. When the vehicle is stopped, it is easy to stabilize the magnitude of the current flowing through the power path 11 at a predetermined magnitude. For example, during a part of the period when the vehicle is stopped, the constant current circuit 116 is controlled by the control device C2 to flow a constant current to the positive power line 17 and the negative power line 20 based on the power supplied from the power supply unit 10. This makes it possible to measure the resistance values ​​R1, R2 of the first switch 33A and the second switch 33B.

[0079] <Other embodiments> The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, but is indicated by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

[0080] Unlike the first embodiment, the voltage detection unit may be connected to any location that can be regarded as having the same potential as the terminals on both sides of the first switch.

[0081] 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.

[0082] Unlike the first embodiment, the resistance value calculation unit, the degradation detection unit, and the notification function unit may be configured as separate information processing devices (separate microcomputers, etc.).

[0083] Unlike the first embodiment, the first switch may be provided on the negative power line and the second switch may be provided on the positive power line. In this case, it is preferable that the parallel switching path is also provided on the negative power line.

[0084] Unlike the first embodiment, the control unit and the control device may be configured as one microcomputer.

[0085] Unlike the embodiment 1, a configuration without the third switch may be used. In this case, a current rise occurs in which the value of the current flowing through the power path rises suddenly as a result of the switching control being executed.

[0086] Unlike the first embodiment, table data in which resistance values ​​corresponding to current values ​​and voltage values ​​are determined may be stored in advance in a storage unit, and the resistance value corresponding to the current value and voltage value may be adopted from the table data.

[0087] Unlike the first embodiment, the resistance value may be used as the judgment value itself without temperature correction.

[0088] Unlike the first embodiment, a configuration may be adopted in which the resistance value of only one of the first switch or the second switch is measured.

[0089] Unlike the first embodiment, the variation rate may be calculated using the resistance values ​​each time charging is performed (each time the charging connector is connected to the charging inlet).

[0090] Unlike the first embodiment, the initial resistance values ​​of the first and second switches before they are mounted on the vehicle (i.e., before they are used) may be stored in a storage unit, and the resistance values ​​of the first and second switches after they are mounted on the vehicle may be measured, and the fluctuation rate may be calculated by (measured resistance value / initial resistance value). In this case, the measured resistance value is greater than the initial resistance value, so the fluctuation rate is 1 or more. For this reason, the control unit is configured to specify the determination value based on the resistance value when the fluctuation rate is equal to or less than an upper limit fluctuation threshold value greater than 1. [Explanation of symbols]

[0091] 1,2...Deterioration determination device 10…Power supply unit (battery) 11…Power line 15...Control section 15A…Resistance value calculation section 15B…Deterioration detection section 15C…Notification function section 15D…Storage section 16,116…constant current circuit 17…Positive power line (power path) 18…Charging inlet 19…Charging connector 20...Negative power line (power path) 33…System main relay 33A…First switch (relay) 33B…Second switch (relay) 33C…Parallel switching path (precharge circuit) 33D…Resistor 33E…Third switch 35,36…Load 35A…Inverter 35B…Motor 35C…Capacitor 37…Temperature detection section 37A…First temperature detection section 37B…Second temperature detection section 38...Current detection section 39... Potential detection section 39A…First potential detection section 39B...Second potential detection unit 100,200…In-vehicle system A…Current value C1, C2: Control device (control unit) F…Fuse Jv1, Jv2...Judgement value R1, R2…Resistance value Rv1, Rv2…Fluctuation rate Sd…degraded signal Son…On signal Th11, Th12: Resistance threshold Th13: Upper limit fluctuation threshold Th14: Lower fluctuation threshold V1,V2…potential difference

Claims

1. A deterioration determination device for use in an in-vehicle system including a power path that is a path for transmitting power from a power supply unit to a load and a relay provided in the power path, a constant current circuit for controlling a current flowing through the relay at a constant level; A control unit that controls the constant current circuit; Equipped with The control unit measures a resistance value between both terminals of the relay while controlling the constant current circuit so that a current flowing through the relay is constant.

2. The degradation determining device according to claim 1 , wherein the control unit performs an abnormality response process when a determination value based on the measured resistance value exceeds a threshold value.

3. The deterioration determining device according to claim 2 , wherein the control unit specifies the determination value based on the resistance value measured after a predetermined time has elapsed since a current started to flow through the relay.

4. The control unit is configured to continuously measure the resistance value, The degradation determining device according to claim 3 , wherein after the predetermined time has elapsed, the control unit specifies the determination value based on the resistance value whose rate of fluctuation with respect to the previously measured resistance value is equal to or less than a fluctuation threshold value.

5. The control unit is configured to continuously measure the resistance value, The degradation determining device according to claim 2 , wherein the control unit specifies the determination value based on the resistance value whose fluctuation rate with respect to the previously measured resistance value is equal to or less than a fluctuation threshold value.

6. Further, a temperature detection unit is provided to detect a temperature of the relay, The deterioration determining device according to claim 2 , wherein the control unit determines the determination value based on the measured resistance value and a temperature value of the relay detected by the temperature detection unit.

7. the power supply unit is a battery, the in-vehicle system includes a charging inlet to which a charging connector provided outside the vehicle is connected; The relay is provided between the charging inlet and the battery, the constant current circuit is provided between the relay and the charging inlet, 7. The deterioration determination device according to claim 1, wherein the control unit measures the resistance value while controlling the constant current circuit so as to flow a constant current to the relay and the battery based on power supplied from outside the vehicle via the charging inlet.

8. 7. The deterioration determination device according to claim 1, wherein a precharge circuit is connected to the power path in parallel with the relay.

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