Sticking diagnosis method and sticking diagnosis device

Abstract

This sticking diagnosis method includes: a step for detecting currents respectively flowing through a plurality of battery pack circuits M1-Mn by all current sensors S1-Sn included in the plurality of battery pack circuits M1-Mn in a state where all positive electrode relays P1-Pn and all negative electrode relays N1-Nn included in the plurality of battery pack circuits M1-Mn are turned on; and a diagnosis step for diagnosing whether the positive electrode relays P1-Pn and the negative electrode relays N1-Nn are in a stuck-off state on the basis of the currents detected by the current sensors S1-Sn.

Description

Method and device for diagnosing sticking

[0001] The present invention relates to a method and an apparatus for diagnosing a stuck state.

[0002] Conventionally, there have been known power supply circuit control devices that determine whether a relay is welded. For example, in a power supply circuit control device described in Patent Document 1, the power supply circuit includes a first relay that controls electrical conduction / de-energization between a load and one pole of a power storage mechanism, a circuit having a resistor connected in series with the first relay, a second relay connected in parallel with the circuit, and a third relay that controls electrical conduction / de-energization between the load and the other pole of the power storage mechanism, and the control device distinguishes between a fixation on the energized side and a fixation on the non-energized side of the relay to determine an abnormality in the relay (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-081340

[0004] However, when a power supply circuit is configured by connecting multiple parallel circuits, each including a first relay, a second relay, a third relay, and a resistor, in parallel, if a relay included in one of the multiple parallel circuits becomes stuck off, excessive current will flow in the other parallel circuits, causing a problem of applying a large load to the relays.

[0005] The problem to be solved by the present invention is to provide a method and an apparatus for diagnosing a stuck state that prevent a large load from being applied to a relay.

[0006] The present invention solves the above problem by detecting the current flowing through each of a plurality of battery pack circuits using all current sensors included in the plurality of battery pack circuits while all positive electrode relays and all negative electrode relays are turned on while the battery pack is being discharged or charged in response to input / output requests to the battery pack, and diagnosing whether the positive electrode relays and negative electrode relays are stuck off based on the currents detected by the current sensors.

[0007] According to the present invention, it is possible to prevent a large load from being applied to the relay.

[0008] Fig. 1 is a block diagram of a vehicle power supply system according to an embodiment of the present invention. Fig. 2 is a flowchart showing steps of a method for diagnosing a stuck battery according to an embodiment of the present invention. Fig. 3 is a graph showing characteristics of input / output values ​​of a battery pack. Fig. 4 is a graph showing characteristics of current or remaining capacity of the battery pack.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a vehicle power supply system according to an embodiment of the present invention.

[0010] The vehicle power supply system 1 according to this embodiment includes multiple battery pack circuits M1-Mn, an inverter 2, a capacitor 3, a voltage sensor 5, and a controller 10. The vehicle power supply system is installed in a vehicle and supplies power to a load installed in the vehicle. The multiple battery pack circuits M1-Mn are configured as multiple parallel circuits in which the battery pack circuits M1-Mn are connected in parallel. The multiple battery pack circuits M1-Mn are circuits that switch between supplying and cutting off power between a vehicle power source and the load. The multiple battery pack circuits M1-Mn correspond to the "battery pack parallel circuits" of the present invention, and the circuit including the multiple battery pack circuits M1-Mn and the capacitor 3 corresponds to the "power supply circuit" of the present invention. Furthermore, the device including the multiple battery pack circuits M1-Mn, the capacitor 3, and the controller 10 corresponds to the "sticking diagnosis device" of the present invention.

[0011] The battery pack circuit M1 includes a battery pack B1, a positive electrode relay P1, a negative electrode relay N1, a charging relay C1, and a charging resistor R1. The positive electrode relay P1, the negative electrode relay N1, and the charging relay C1 are relay switches with mechanical contacts, and are switched on and off under the control of the controller 10. Note that the positive electrode relay P1, the negative electrode relay N1, and the charging relay C1 may also be semiconductor switches. The battery pack B1 is a battery group in which multiple secondary batteries, such as lithium-ion batteries or lead batteries, are connected in parallel and / or series. The battery pack B1 corresponds to a vehicle power source. The battery pack B1 is electrically connected to the positive electrode relay P1 and other circuit elements included in the battery pack circuit M1, and to the capacitor 3.

[0012] In the battery pack circuit M1, a positive electrode relay P1 is connected in parallel to a series circuit connecting a charging relay C1 and a charging resistor R1 in series, and a battery pack B1 and a negative electrode relay N1 are connected to a parallel circuit connecting the series circuit of the charging relay C1 and the charging resistor R1 and the positive electrode relay P1 in parallel. The series circuit of the charging relay C1 and the charging resistor R1 is a pre-charge circuit that charges the capacitor 3. The charging resistor R1 limits the current value during capacitor charging. The charging relay C1 and the positive electrode relay P1 are connected in series with the positive electrode of the battery pack B1. The negative electrode relay N1 is connected in series with the negative electrode of the battery pack B1. The charging relay C1, the positive electrode relay P1, and the negative electrode relay are also electrically connected to the inverter 2. When charging the capacitor 3, the paired negative electrode relay N1 and charging relay C1 are turned on. After the capacitor 3 is charged, the negative and positive relays N1 and P1, which form a pair, are turned on when power from the battery pack B1 is supplied to the inverter 2. The current sensor S1 is connected to the battery pack B1 and detects the charge / discharge current of the battery pack B1.

[0013] The battery pack circuits M2 and Mn have the same circuit configuration as the battery pack circuit M1, and include battery packs B2 and Bn, positive electrode relays P1 and Pn, negative electrode relays N1 and Nn, charging relays C1 and Cn, and charging resistors R1 and Rn. n represents the number of battery pack circuits incorporated in the power supply circuit. As shown in Figure 1, the battery pack circuits M1, M2, and Mn are connected in parallel to a capacitor 3 and arranged in order from the first battery pack circuit M1 to the second battery pack circuit M2, and finally to the nth battery pack circuit Mn.

[0014] The connection lines (C, N lines) electrically connecting the charging relays C1 to Cn and the negative relays N1 to Nn in series are charging lines (charging circuits) for precharging. The connection lines (P, N lines) electrically connecting the positive relays P1 to Pn and the negative relays N1 to Nn in series are high-voltage lines (high-voltage circuits) for supplying current when the vehicle is running or the battery is being charged. In other words, the power supply circuit included in the vehicle power supply system includes n connection lines (C, N lines) and n connection lines (P, N lines).

[0015] The inverter 2 is an example of a load of the vehicle, includes a power conversion circuit, converts the power output from the assembled batteries B1 to Bn, and outputs the converted power to the motor. During regenerative operation of the motor, the inverter 2 converts the power generated by the motor and outputs the converted power to the assembled batteries B1 to Bn.

[0016] A smoothing capacitor 3 is connected to the input side of the inverter 2 (the connection side of the assembled batteries B1 to Bn). The capacitor 3 is connected in parallel to a parallel battery circuit in which a plurality of assembled battery circuits M1 to Mn are connected in parallel. A voltage sensor 5 is a sensor that detects the voltage of the capacitor 3, and is connected in parallel to the capacitor 3. Note that while the capacitor 3 and the voltage sensor 5 are shown in FIG. 1 as components outside the inverter 2 circuit, the capacitor 3 and the voltage sensor 5 may be components inside the inverter 2 circuit or outside the inverter 2 circuit.

[0017] The controller 10 has functions such as switching the charging relays C1 to Cn, positive electrode relays P1 to Pn, and negative electrode relays N1 to Nn on and off, diagnosing whether the charging relays C1 to Cn, positive electrode relays P1 to Pn, and negative electrode relays N1 to Nn are stuck, and managing the state of the capacitor 3. The controller 10 has a processor for implementing the various functions, a memory that stores programs executed by the processor, and the like. The controller 10 acquires information about the current flowing through the battery pack circuits M1 to Mn from current sensors S1 to Sn, and acquires voltage information about the capacitor 3 from a voltage sensor 5. Note that the controller 10 is not limited to the function of switching the relays on and off, and may also have a function of managing the state of the battery packs B1 to Bn, for example.

[0018] In the following description, when referring to the charging relays C1 to Cn collectively, or when referring to a charging relay without specifying a relay among the charging relays C1 to Cn, the symbols for the charging relays C1 to Cn will be written as "C1 to Cn." For example, when referring to turning on the charging relays C1 to Cn, it is sufficient that at least one of the charging relays C1 to Cn is turned on. When referring to turning on one charging relay C1 to Cn, it is sufficient that one of the charging relays C1 to Cn is turned on. When referring to turning on all the charging relays C1 to Cn, it is sufficient that n charging relays C1 to Cn are turned on. The symbol notations for the negative and positive relays, "N1 to Nn" and "P1 to Pn," are the same as the symbol notations for the charging relays.

[0019] The relay fixation diagnosis function will now be described. The controller 10 diagnoses whether the charging relays C1-Cn, the positive electrode relays P1-Pn, and the negative electrode relays N1-Nn are fixed based on the currents detected by the current sensors S1-Sn and / or the voltages detected by the voltage sensor 5. For example, to charge the capacitor 3, the controller 10 turns on all the charging relays C1-Cn and all the negative electrode relays N1-Nn and uses the current sensors S1-Sn to detect the current flowing through the assembled battery circuits M1-Mn. If the current detected by the current sensors S1-Sn is equal to or less than a predetermined value, the controller 10 determines that at least one of the charging relays C1-Cn and the negative electrode relays N1-Nn is fixed off. The predetermined value is a current threshold for determining whether the relay is fixed off, a current value close to zero, such as several amperes or several milliamperes. For example, if the current detected by the current sensor S2 is equal to or less than the predetermined value, the controller 10 determines that at least one of the charging relay C2 and the negative electrode relay N2 is fixed off.

[0020] It should be noted that when charging the capacitor 3, the controller 10 does not necessarily need to turn on all of the charging relays C1 to Cn and all of the negative electrode relays N1 to Nn, but may turn on multiple charging relays C1 to Cn and multiple negative electrode relays N1 to Nn and diagnose whether the charging relays C1 to Cn and the negative electrode relays N1 to Nn are stuck off in the same manner as described above.

[0021] The controller 10 diagnoses whether the positive electrode relays P1-Pn and the negative electrode relays N1-Nn are stuck off based on the detected currents detected by the current sensors S1-Sn while discharging or charging the battery packs B1-Bn in response to input / output requests for the battery packs B1-Bn. When the vehicle starts, the controller 10 turns on all charging relays C1-Cn and all negative electrode relays N1-Nn to start charging the capacitor 3 (pre-charge start). When charging of the capacitor 3 is completed (pre-charge completion), the controller 10 turns on all positive electrode relays P1-Pn and turns off all charging relays C1-Cn. The battery packs B1-Bn input and output power in response to input / output requests. Input / output requests include system requests from the system, such as requests from user operations such as the vehicle's main switch (vehicle start), accelerator, and brake, requests from user operations of auxiliary devices such as the navigation system, charging of the auxiliary battery, and vehicle driving. Examples of input / output requests include DCDC startup current, motor excitation current, and driving / charging current. When an input / output request is made to the battery packs B1-Bn, the controller 10 controls the vehicle load so that the input / output values ​​(input / output power) from the battery packs B1-Bn correspond to the input / output request. The controller 10 detects the current flowing through the battery pack circuits M1-Mn using current sensors S1-Sn while the battery packs B1-Bn are being discharged or charged. If the current detected by the current sensors S1-Sn is equal to or less than a predetermined value, the controller 10 determines that at least one of the positive electrode relays P1-Pn and the negative electrode relays N1-Nn is stuck off. The controller 10 may diagnose whether the positive electrode relays P1-Pn and the negative electrode relays N1-Nn are stuck off based on the current detected by the current sensors S1-Sn while the battery packs B1-Bn are being charged.

[0022] The following describes the function of managing the states of the capacitor 3 and the battery packs B1 to Bn. While the controller 10 is charging the capacitor 3 with the charging relays C1 to Cn and the negative electrode relays N1 to Nn turned on, it acquires the detected voltage from the voltage sensor 5 and manages the charging state of the capacitor 3. When the charging state of the capacitor 3 reaches full charge, the controller 10 switches the positive electrode relays P1 to Pn from off to on and switches the charging relays C1 to Cn off.

[0023] Next, the method for diagnosing a stuck state according to this embodiment will be described. Fig. 2 is a flowchart showing the steps of the method for diagnosing a stuck state. The controller 10 executes the control flow shown in Fig. 2.

[0024] In step S1, the controller 10 determines that the vehicle has been started. If the vehicle has not been started, the controller 10 enters a sleep state and the control flow waits in step S1. The controller 10 determines that the vehicle has been started by receiving an ON command from the vehicle's main switch. Alternatively, all negative relays N1 to Nn may be turned ON to diagnose whether the charging relays C1 to Cn are stuck ON.

[0025] In step S2, the controller 10 turns on all the charging relays C1 to Cn and all the negative electrode relays N1 to Nn to charge the capacitor 3. In step S3, the controller 10 determines whether the capacitor 3 has reached full charge based on the voltage detected by the voltage sensor 5. If the capacitor 3 has not reached full charge, the control flow waits in step S3, and charging of the capacitor 3 continues. Note that while the capacitor 3 is being charged, the controller 10 may perform a stuck-off diagnosis of all the charging relays C1 to Cn and all the negative electrode relays N1 to Nn.

[0026] For example, while the capacitor 3 is being charged, the controller 10 diagnoses whether the charging relay C1 and the negative relay N1 are stuck-off based on the detected voltage of the capacitor 3 and the detected current of the current sensor S1. If the detected voltage of the capacitor 3 does not increase while the capacitor 3 is being charged and the current detected by the current sensor S1 is equal to or less than a predetermined value, the controller 10 determines that at least one of the charging relay C1 and the negative relay N1 is stuck-off. The controller 10 may also diagnose whether the charging relays C2 to Cn and the negative relays N2 to Nn are stuck-off using a method similar to the method for diagnosing whether the charging relay C1 and the negative relay N1 are stuck-off.

[0027] Before executing the control flow of step S2, the controller 10 may charge the capacitor 3 using at least one of the n charging lines and diagnose whether a relay included in the charging line used to charge the capacitor 3 is stuck off. For example, the controller 10 charges the capacitor 3 with the charging relay C1 and the negative electrode relay N1 turned on and detects the capacitor voltage using the voltage sensor 5. If the detected voltage from the voltage sensor 5 does not increase, the controller 10 determines that at least one of the charging relay C1 and the negative electrode relay N1 is stuck off. On the other hand, if the detected voltage from the voltage sensor 5 increases, the controller 10 determines that the charging relay C1 and the negative electrode relay N1 are normal. The controller 10 may also diagnose whether the charging relays C2 to Cn and the negative electrode relays N2 to Nn are stuck off using the same diagnostic method as for the stuck-off of the charging relay C1 and the negative electrode relay N1. When diagnosing whether a relay included in at least one charging line is stuck off, for example, if the negative relay N1 is the target of diagnosis, the controller 10 may turn on all charging relays C1 to Cn and the negative relay N1 to charge the capacitor 3, and diagnose whether the charging relay C1 and the negative relay N1 are stuck off while charging the capacitor 3. Furthermore, the controller 10 does not necessarily have to diagnose whether a relay is stuck off for each individual charging line, and may perform a single diagnosis of whether the relays included in all charging lines are stuck off.

[0028] When the capacitor 3 reaches full charge, the controller 10 turns on all positive relays P1-Pn and all negative relays N1-Nn and turns off all charging relays C1-Cn (step S4). In step S5, while discharging or charging the assembled batteries B1-Bn in response to input / output requests for the assembled batteries B1-Bn, the controller 10 starts a stuck-off diagnosis of the relays with all positive relays P1-Pn and all negative relays N1-Nn turned on. The controller 10 detects the currents flowing through the assembled battery circuits M1-Mn using all current sensors S1-Sn included in the assembled battery circuits M1-Mn. The controller 10 also diagnoses whether the positive relays P1-Pn and the negative relays N1-Nn are stuck-off based on the currents detected by the current sensors S1-Sn. If the detected currents detected by the current sensors S1-Sn are equal to or less than a predetermined value, the controller 10 counts up the number of times the relays have been determined to be stuck-off. For example, if the detected current of the current sensor S1 is below a predetermined value, the controller 10 determines that there is a possibility that either the positive relay P1 or the negative relay N1 is stuck off, and counts up the number of times that the relay has been determined to be stuck off.

[0029] The controller 10 executes a fixed-off diagnosis of the positive relays P1 to Pn and the negative relays N1 to Nn a predetermined number of times, and when the number of fixed-off determinations reaches a predetermined threshold, it determines that either the positive relays P1 to Pn or the negative relays N1 to Nn is fixed-off. Note that while the fixed-off diagnosis has been executed a predetermined number of times, if the detected current of the current sensors S1 to Sn for a relay for which the number of fixed-off determinations has been counted up, the number of determinations may be reset. For example, suppose that the detected current of the current sensor S1 falls below a predetermined value and the number of determinations for the positive relay P1 and the negative relay N1 is counted up. If the detected current of the current sensor S1 becomes higher than the predetermined value during the next diagnosis, the number of determinations for the positive relay P1 and the negative relay N1 may be reset. In other words, when the controller 10 detects a state in which the detected current of the current sensor S1 is below a predetermined value multiple times in succession until the predetermined number of times reaches a threshold value, it determines that either the positive electrode relays P1 to Pn or the negative electrode relays N1 to Nn are stuck off.

[0030] The controller 10 limits the input / output values ​​of the battery packs B1 to Bn until the first stuck-off diagnosis after the vehicle start is completed (step S6). Specifically, the controller 10 limits the input / output values ​​of the battery packs to input / output upper limit values ​​that are lower than the maximum input / output values ​​of the components on the circuit. In step S7, it is determined whether the stuck-off diagnosis is completed. If the stuck-off diagnosis is completed, the controller 10 releases the limit on the input / output values ​​of the battery packs B1 to Bn imposed in step S6 and executes the control flow in step S8. If the stuck-off diagnosis is not completed, the controller 10 continues the stuck-off diagnosis, and the control flow returns to step S6.

[0031] The limitations on input / output values ​​until the first stuck-off diagnosis is completed will be described with reference to Figure 3. Figure 3 is a graph showing the characteristics of the input / output values ​​of battery packs B1 to Bn. In Figure 3, Pn represents the input / output value requested of battery packs B1 to Bn by user operation or the system. In the example of Figure 3, it is assumed that an output request is made to battery packs B1 to Bn to output the maximum vehicle output.

[0032] Pc is a predetermined input / output upper limit. Pc is set to a value lower than the maximum input / output value of the components on the circuit and corresponds to the power (current value) at which the components, harnesses, and other components included in the battery pack circuits M1-Mn, on the power supply circuit, do not malfunction or deteriorate. The input / output upper limit (Pc) is set to a value lower than the maximum input / output value of the components on the circuit. If all of the positive relays P1-Pn and negative relays N1-Nn are normal, all of the battery packs B1-Bn output power according to the input / output requirements. On the other hand, if a fixed-off state occurs in any of the positive relays P1-Pn and negative relays N1-Nn, the battery pack circuits M1-Mn cannot pass current through the fixed-off relay. After starting the vehicle, there is a possibility that a fixed-off state occurs in any of the positive relays P1-Pn and negative relays N1-Nn until the first fixed-off diagnosis is completed. Therefore, when an attempt is made to input or output power from or to the battery packs B1-Bn in response to input / output requests when any of the positive electrode relays P1-Pn and the negative electrode relays N1-Nn is stuck off, the input / output per battery pack B1-Bn becomes larger than when all relays are normal. Furthermore, the input / output per battery pack B1-Bn becomes larger as the number of battery pack circuits M1-Mn in which current cannot flow due to the stuck-off relay increases.

[0033] Therefore, in this embodiment, an input / output upper limit value (Pc) is set in advance to prepare for the possibility of a stuck-off state until the first stuck-off diagnosis after vehicle start is completed. Until the stuck-off diagnosis is completed, the controller 10 compares the input / output demand values ​​for the battery packs B1 to Bn with the input / output upper limit value (Pc), and if the input / output demand values ​​are greater than the input / output upper limit value (Pc), the controller 10 limits the input / output demand values ​​to be equal to or less than the input / output upper limit value (Pc). If the input / output demand values ​​are equal to or less than the input / output upper limit value (Pc), the controller 10 does not limit the input / output demand values.

[0034] As shown in FIG. 3 , the controller 10 starts the stuck-off diagnosis at time t0 and ends the first stuck-off diagnosis at time te. During the stuck-off diagnosis, an input / output demand value (Pn) for each of the battery packs B1 to Bn is input in response to a user operation or a request from the system. Until time te, an input / output upper limit value (Pc) is set, and the controller 10 limits the input / output demand value (Pn) to the input / output upper limit value (Pc). After time te has elapsed, the controller 10 releases the limit of the input / output upper limit value (Pc) and controls the vehicle load so that each of the battery packs B1 to Bn inputs and outputs the input / output demand value (Pn). Note that, as will be described later, if a relay is diagnosed as being stuck-off, the controller 10 limits the input / output demand value (Pn) using a different limiting method from the limiting method using the input / output upper limit value (Pc).

[0035] When the stuck-off diagnosis is completed, the controller 10 determines whether or not there is a relay that is stuck-off based on the stuck-off diagnosis result (step S8). If there is a relay that is stuck-off, the controller 10 executes the control flow of step S9. If there is no relay that is stuck-off, the controller 10 executes the control flow of step S10 without executing the control flow of step S9. If there is a relay that is stuck-off, the controller 10 limits the input / output values ​​of the assembled batteries B1 to Bn in step S9. The controller 10 limits the input / output values ​​of the assembled batteries B1 to Bn according to the number of circuits in the assembled battery circuits M1 to Mn that include the relay that is determined to be stuck-off. Specifically, the controller 10 limits the input / output values ​​of the assembled batteries B1 to Bn so that the input / output values ​​are equal to the input / output required values ​​for the assembled batteries B1 to B3 multiplied by (n - m / n), where m is the number of circuits in the assembled battery circuits M1 to Mn that include the relay that is stuck-off. As a specific example, suppose a power supply circuit is configured with three battery pack circuits M1 to M3 in parallel, and two positive relays P2 and P3 are stuck off. Also, suppose there is an output demand for 300 A from battery packs B1 to B3. In this specific example, because two battery pack circuits M2 and M3 include a stuck-off relay, battery packs B2 and B3 cannot output power to the load, and the output demand must be met only by battery pack B1. Therefore, controller 10 multiplies the input / output demand value (300 A) by 1 / 3 to obtain 100 A, which is the limited input / output demand value, and controls the vehicle load so that battery pack B1 outputs the limited input / output demand value.

[0036] If the stuck-off diagnosis result indicates that all of the positive relays P1 to Pn and negative relays N1 to Nn are normal, the controller 10 does not limit the input / output values ​​of the multiple battery packs B1 to Bn. Also, if the stuck-off diagnosis result indicates that either the positive relays P1 to Pn or the negative relays N1 to Nn in each of the battery pack circuits B1 to Bn is in a stuck-off state, the controller 10 executes a vehicle stop mode to stop the vehicle.

[0037] In step S10, the controller 10 determines whether the vehicle's main switch (main SW) is off. If the main switch is on, in step S11, the controller 10 diagnoses the positive relays P1 to Pn and the negative relays N1 to Nn for stuck-off status. The method for diagnosing stuck-off status is the same as the method for diagnosing stuck-off status in the control flow of step S5. After executing the control flow of step S11, the controller 10 executes the control flow of step S8. If any relay is stuck-off, in the control flow of step S9, the controller 10 limits the input / output values ​​of the multiple assembled batteries B1 to Bn depending on the number of assembled battery circuits M1 to Mn that include the relay determined to be stuck-off. That is, while the vehicle is running, the controller 10 repeatedly executes the control flow of steps S8 to S11 to diagnose the relays for stuck-off status and limits the input / output values ​​of the assembled batteries B1 to Bn depending on the results of the stuck-off status diagnosis. If it is determined in the control flow of step S10 that the main switch (main SW) of the vehicle is off, the controller 10 ends the control flow shown in FIG.

[0038] As described above, the fixation diagnosis method or fixation diagnosis device according to this embodiment includes the steps of detecting currents flowing through the plurality of battery pack circuits M1-Mn using all current sensors S1-Sn included in the plurality of battery pack circuits M1-Mn while all positive electrode relays P1-Pn and all negative electrode relays N1-Nn are turned on while the battery packs B1-Bn are being discharged or charged in response to input / output requests to the battery packs B1-Bn, and diagnosing whether the positive electrode relays P1-Pn and the negative electrode relays N1-Nn are stuck off based on the currents detected by the current sensors S1-Sn. This makes it possible to prevent a large load from being applied to the relays, such as excessive current flow, based on the diagnostic results.

[0039] Furthermore, in this embodiment, the controller 10 limits the input / output values ​​of the battery packs B1 to Bn to a predetermined input / output upper limit or less until the first fixed-off diagnosis is completed, thereby preventing excessive thermal load from being applied to the circuit components until the fixed-off diagnosis of the positive electrode relays P1 to Pn and the negative electrode relays N1 to Nn is completed.

[0040] In this embodiment, the controller 10 limits the input / output values ​​of the battery packs B1 to Bn depending on the number of battery pack circuits M1 to Mn that include a relay determined to be stuck off, thereby preventing excessive thermal load from being applied to a normal relay.

[0041] In a first modification of this embodiment, the controller 10 may temporarily suspend the stuck-off diagnosis without executing the control flow of steps S5 to S7 or the diagnostic steps corresponding to steps S8 and S9 when the current flowing through the assembled battery circuits M1 to Mn is equal to or less than a predetermined lower current limit. The lower current limit is a preset lower limit of the current necessary to avoid false detection in the stuck-off diagnosis. When the current flowing through the assembled battery circuits M1 to Mn is equal to or less than the lower current limit, the current detected by the current sensors S1 to Sn is small, which may result in false detection when performing the stuck-off diagnosis. Therefore, in the first modification, the controller 10 suspends the stuck-off diagnosis when the current flowing through the assembled battery circuits M1 to Mn is equal to or less than the predetermined lower current limit. This prevents false detection of a stuck-off state in the positive relays P1 to Pn or the negative relays N1 to Nn.

[0042] Furthermore, as a second modification of this embodiment, when the current difference between the currents flowing through the plurality of assembled battery circuits M1 to Mn or the remaining capacity difference between the plurality of assembled batteries B1 to Bn is equal to or greater than a predetermined value, the controller 10 may limit the input / output values ​​of the plurality of assembled batteries B1 to Bn by turning off the positive electrode relays P1 to Pn and / or negative electrode relays N1 to Nn connected to the assembled battery B1 to Bn with the lower current or remaining capacity.

[0043] FIG. 4 is a graph showing the current or remaining capacity characteristics of battery packs B1 to B4. (a) shows the characteristics when there is no variation, and (b) shows the characteristics when there is a large variation. In the example of FIG. 4, the power supply circuit is composed of four battery pack circuits M1 to M4 connected in parallel. The degree of deterioration of each battery pack M1 to M4 varies depending on the battery's operating conditions and individual differences. In the initial state of the battery packs M1 to M4, as shown in FIG. 4(a), the variation in the current or remaining capacity of the battery packs B1 to B4 is small. On the other hand, as the battery packs B1 to B4 deteriorate, the variation in the current or remaining capacity of the battery packs B1 to B4 increases. In the example of FIG. 4(b), the current difference or remaining capacity (ΔQ) between battery packs B1 and B4 is the largest. When the current difference or remaining capacity (ΔQ) is equal to or greater than a predetermined value, the controller 10 turns off the positive relay P2 and / or the negative relay N2. Furthermore, if input / output demand values ​​are output from the batteries B1, B3, and B4 while the relay of the battery pack circuit B2 is turned off, a large thermal load is placed on the components on the battery pack circuits M1, M3, and M4. In Modification 2, the controller 10 limits the input / output values ​​of the batteries B1 to Bn depending on the number of circuits in the battery pack circuits M1, M3, and M4 that include on-state relays (positive relays P1, P3, and P4 and negative relays N1, N3, and N4). Specifically, the controller 10 limits the input / output values ​​of the batteries B1 to Bn so that the input / output demand values ​​for the batteries B1 to B4 are multiplied by (n-p / n), where p is the number of circuits in the battery pack circuits M1 to Mn that include fixed-off relays. When the relay included in the battery pack circuit M2 is turned off and the relays included in the battery pack circuits M1, M3, and M4 are turned on, the input / output demand values ​​are limited to ¾. This prevents excessive thermal load from being placed on normal relays. Furthermore, deterioration of the battery packs B1 to B4 can be prevented.

[0044] In this embodiment, the power supply circuit included in the vehicle power supply system 1 is not limited to the circuit configuration shown in FIG. 1 and may have other circuit configurations. For example, the battery packs B1-Bn do not necessarily have to be provided in each of the battery pack circuits M1-Mm. For example, the battery packs B1-Bn may be connected in series or in parallel to form a single battery, and the single battery may be connected to a parallel circuit of the battery pack circuits M1-Mm that does not include the battery packs B1-Bn. Furthermore, the battery pack circuits M1-Mm may be divided into a first parallel circuit including charging relays C1-Cn, charging resistors R1-Rn, and positive relays P1-Pn, and a second parallel circuit including negative relays N1-Nn. Furthermore, a battery formed by connecting the battery packs B1-Bn in series or in parallel may be connected between the first parallel circuit and the second parallel circuit.

[0045] In this embodiment, the controller 10 does not need to execute all of the control flows shown in FIG. 2, and some of the control flows may be omitted, or the order of the control flows may be changed.

[0046] REFERENCE SIGNS LIST 1 Vehicle power supply system 2 Inverter 3 Capacitor 5 Voltage sensor 10 Controller B1 to Bn Assembled battery C1 to Cn Charging relay M1 to Mn Assembled battery circuit N1 to Nn Negative electrode relay P1 to Pn Positive electrode relay R1 to Rn Charging resistor

Claims

1. A method for diagnosing a stuck state of a relay included in a power supply circuit mounted on a vehicle, wherein the power supply circuit has: an assembled battery parallel circuit in which assembled battery circuits, each including a positive relay, a negative relay, a charging relay, and a charging resistor, are connected in parallel; a capacitor connected in parallel to the assembled battery parallel circuit; and an assembled battery electrically connected to the assembled battery circuit and the capacitor; the assembled battery circuit has: the positive relay connected in parallel to a series circuit that connects the charging relay and the charging resistor in series; and the negative relay connected to a parallel circuit that connects the series circuit and the positive relay in parallel; the stuck state diagnosis method includes the steps of: detecting currents flowing through each of the plurality of assembled battery circuits by all current sensors included in the plurality of assembled battery circuits with all of the positive relays and all of the negative relays turned on while the assembled battery is being discharged or charged in response to an input / output request for the assembled battery; and diagnosing whether the positive relay and the negative relay are stuck off based on the current detected by the current sensors.

2. A method for diagnosing a stuck state as claimed in claim 1, comprising the step of limiting the input / output values ​​of the battery pack to a predetermined input / output upper limit value or less until the first diagnosis of the stuck-off state after starting the vehicle is completed, wherein the input / output upper limit value is lower than the maximum input / output value of a component on the circuit.

3. A method for diagnosing a stuck state according to claim 1 or 2, wherein the input / output values ​​of the battery pack are limited depending on the number of circuits in the battery pack circuit that include the relay determined to be stuck off.

4. A method for diagnosing a stuck state according to any one of claims 1 to 3, wherein the diagnostic step is not executed when the current flowing through the battery pack circuit is equal to or less than a predetermined lower limit current value.

5. A method for diagnosing a stuck state according to any one of claims 1 to 4, comprising the step of, when the difference between the currents flowing through the plurality of battery pack circuits or the difference between the remaining capacities of the plurality of battery packs is equal to or greater than a predetermined value, turning off the positive electrode relay and / or the negative electrode relay connected to the battery pack with the lower current or lower remaining capacity, thereby limiting the input / output values ​​of the plurality of battery packs.

6. A sticking diagnosis device comprising: a battery pack parallel circuit in which battery pack circuits each including a positive electrode relay, a negative electrode relay, a charging relay, and a charging resistor are connected in parallel; a capacitor connected in parallel to the battery pack parallel circuit; a battery pack electrically connected to the battery pack circuit and the capacitor; and a controller that switches the positive electrode relay, the negative electrode relay, and the charging relay on and off, wherein the battery pack circuit connects the positive electrode relay in parallel to a series circuit that connects the charging relay and the charging resistor in series, and connects the negative electrode relay to a parallel circuit that connects the series circuit and the positive electrode relay in parallel, and the controller detects currents flowing through each of the multiple battery pack circuits using all current sensors included in the multiple battery pack circuits with all of the positive electrode relays and all of the negative electrode relays turned on while the multiple battery packs are being discharged or charged in response to input / output requests for the multiple battery packs, and diagnoses whether the positive electrode relay and the negative electrode relay are stuck off based on the current detected by the current sensors.

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