Relay diagnosis device

Abstract

The invention relates to a relay diagnostic device. The relay diagnosis device is not actually connected with a relay, and diagnoses whether a cut-off line is valid in a state that the relay is cut off. A relay diagnostic device is included in a vehicle power supply system including: a relay attached to a power line closer to a battery than a smoothing capacitor; a driver that drives the relay; a first control unit; a second control unit which receives the instruction of the first control unit and outputs a driving signal to a driver; and a cut-off line that directly cuts off the relay by the first control unit prior to a drive signal from the second control unit to the driver. The first control unit outputs a disconnection command of the relay to the second control unit at the end of the system, sets the state of the disconnection line to the disconnection side after performing a welding diagnosis of the relay on the basis of the presence or absence of a voltage drop in the smoothing capacitor, and outputs a connection command of the relay to the second control unit. The output state of the driver is monitored to diagnose whether the cutoff line is valid.

Description

Technical Field

[0001] This disclosure relates to relay diagnostic devices. Background Technology

[0002] Conventionally, as such relay diagnostic devices, the following apparatus has been proposed: In an electric vehicle equipped with a drive motor, an inverter that drives the drive motor, a battery that supplies power to the inverter, first and second system main relays that open and close a pair of power lines connecting the battery and the inverter, a pre-charge relay connected in series with a pre-charge resistor in a circuit connected in parallel with the first system main relay, and two device relays that open and close a pair of branch lines branching from the pair of power lines, a diagnostic processing unit is provided for performing fuse diagnostic checks on the device relays (for example, see Patent Document 1). During system startup processing, the diagnostic processing unit identifies one of the two device relays as the diagnostic target, keeps the device relay and the first system main relay in a closed state, and switches the other device relay (not the diagnostic target), the second system main relay, and the pre-charge relay from closed to connected state. Then, it checks whether the voltage between the pair of branch lines has increased, thereby performing fuse diagnostic checks on one of the device relays. In addition, during the processing period after the use of the branch line ends, the diagnostic processing department takes the equipment relay of the other of the two equipment relays as the diagnostic target, keeps the control of the first system main relay, the second system main relay and the equipment relay of the other equipment relay which is not the diagnostic target connected, and switches the control of the other equipment relay which is the diagnostic target from connected to disconnected. Then, it checks whether the voltage between the pair of branch lines has dropped, thereby performing a welding diagnosis on the other equipment relay.

[0003] Existing technical documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-54160 Summary of the Invention

[0005] The problem that the invention aims to solve

[0006] In an electric vehicle comprising a drive unit, a battery, a smoothing capacitor mounted on a power line from the battery to the drive unit, a relay mounted on the power line closer to the battery side than the smoothing capacitor, and a driver that drives the relay, there exists an electric vehicle that has a control unit connected to the driver, which outputs a drive signal to the driver, and from which the relay's disconnect wire is directly disconnected. In this vehicle, in addition to checking the relay's fusion, it is preferable to check whether the disconnect wire is functioning effectively. Checking the relay's fusion when the system is stopped is performed by determining whether the voltage of the smoothing capacitor drops when the relay is disconnected. Therefore, if the disconnect wire is set to the disconnect side while the relay is connected, and the function of the disconnect wire is checked based on whether the voltage of the smoothing capacitor drops, then the relay needs to be reconnected for subsequent fusion checks, increasing the number of relay connections and potentially reducing the relay's lifespan.

[0007] The main purpose of the relay diagnostic device disclosed herein is to diagnose whether the disconnection line is effective when the relay is disconnected, without actually connecting the relay.

[0008] Methods for solving problems

[0009] The relay diagnostic device disclosed herein employs the following means to achieve the aforementioned main objectives.

[0010] The present invention discloses a relay diagnostic device for a vehicle drive system, the vehicle drive system comprising: a drive unit; a battery; a smoothing capacitor installed on a power line from the battery to the drive unit; a relay installed on the power line at a position closer to the battery side than the smoothing capacitor; a driver that drives the relay; a first control unit that controls the system; a second control unit that receives instructions from the first control unit and outputs a drive signal to the driver; and a disconnect line connected from the first control unit to the driver, which, by being set as the disconnect side by the first control unit, directly disconnects the relay prior to the drive signal from the second control unit to the driver. In the relay diagnostic device, when the first control unit disconnects the battery from the drive unit to terminate the system, it outputs a disconnect command for the relay to the second control unit. After diagnosing whether the relay is fused based on whether there is a voltage drop in the smoothing capacitor, it sets the state of the disconnect line to the disconnect side and outputs a connection command for the relay to the second control unit, monitors the output state of the driver, and thereby diagnoses whether the disconnect line is functioning effectively.

[0011] In the relay diagnostic device disclosed herein, when the system is terminated by disconnecting the battery from the drive unit, the first control unit outputs a relay disconnection command to the second control unit, and diagnoses whether the relay is fused based on whether there is a voltage drop in the smoothing capacitor. Then, the first control unit sets the disconnection line to the disconnected side and outputs a relay connection command to the second control unit, monitoring the output status of the driver, thereby diagnosing whether the disconnection line is functioning effectively. Thus, without actually connecting the relay, it is possible to diagnose whether the disconnection line is functioning effectively while the relay is disconnected. Furthermore, since the relay is connected when the system is terminated by disconnecting the battery from the drive unit, by performing a disconnection line diagnosing after diagnosing relay fusion, it is possible to avoid reconnecting the relay for fusion diagnosing.

[0012] In the relay diagnostic device disclosed herein, the relay may include: a first relay, installed on one of the positive and negative terminals of the power line that is closer to the battery side than the smoothing capacitor; and a second relay, installed on the other terminal of the positive and negative terminals where the first relay is not installed. The driver includes a first driver for driving the first relay and a second driver for driving the second relay. When the first control unit disconnects the battery from the driving device to terminate the system, it outputs a disconnect command to the second control unit. Based on whether the smoothing capacitor has a voltage drop, it diagnoses whether the first relay is fused. If the diagnosis indicates that the first relay is not fused, the disconnect line is set to the disconnect side, and a connection command for the second relay is output to the second control unit. If the output state of the second driver is in the output state that disconnects the second relay, it is diagnosed that the disconnect line is functioning effectively. Since the first relay is confirmed to be fused and disconnected, even if the disconnect line is faulty and the second relay is connected via the connection command, a closed circuit between the smoothing capacitor and the battery can be avoided. As a result, damage to the relay caused by inrush current can be avoided.

[0013] In the relay diagnostic device disclosed herein, the relay may include: a first relay, installed on one of the positive and negative terminals of the power line that are closer to the battery side than the smoothing capacitor; a second relay, installed on the other terminal of the positive and negative terminals where the first relay is not installed; and a pre-charge circuit, which is a circuit formed by connecting a pre-charge resistor in series with a pre-charge third relay in a manner that bypasses the second relay. The driver includes: a first driver that drives the first relay; a second driver that drives the second relay; and a third driver that drives the third relay. When the first control unit disconnects the battery from the drive device to terminate the system, it outputs a disconnect command for the second relay to the second control unit. It diagnoses whether the second relay is fused based on whether there is a voltage drop in the capacitor. If the diagnosis result indicates that the second relay is not fused, it sets the disconnect line to disconnect. The first control unit first outputs a disconnect command to the second relay, and after confirming that the second relay is not fused by the first driver's output state, it diagnoses that the disconnect line is effectively functioning for the first driver. Upon receiving this diagnosis, it outputs a connection command for the third relay to the second control unit. It then diagnoses whether the first relay is fused based on whether the capacitor voltage rises. If the first relay is not fused, it sets the disconnect line to the disconnect side and outputs connection commands for both the second and third relays to the second control unit. If both the second and third driver output states are in a state that disconnects the second relay, it diagnoses that the disconnect line is effectively functioning for both the second and third drivers. In other words, the first control unit first outputs a disconnect command to the second relay, performs a fusion check on the second relay to confirm that it is not fused, sets the disconnect line to the disconnect side, and outputs a connection command for the first relay, thereby diagnosing whether the disconnect line is effectively functioning for the first driver. Therefore, even if the third relay is fused, or there is an abnormality in the cut-off line, and the first relay is connected according to the connection command of the first relay, a closed circuit is only formed between the battery and the smoothing capacitor via the pre-charge resistor, which can avoid the generation of inrush current on the power line.In addition, the first control unit outputs a connection command for the third relay to perform a welding test on the first relay (a test to determine if the voltage of the smoothing capacitor has increased due to pre-charging). After confirming that the first relay is not welded and is disconnected, the disconnect line is set as the disconnect side, and connection commands for the second and third relays are output to diagnose whether the disconnect line effectively functions for the second and third drivers. Therefore, even if the disconnect line is faulty and the second and third relays are connected via connection commands, a closed circuit between the battery and the smoothing capacitor can be avoided. Furthermore, since the effective functioning of the disconnect line is diagnosed for both the second and third drivers simultaneously, the diagnostic time can be shortened. Attached Figure Description

[0014] Figure 1 This is a schematic structural diagram of a vehicle drive system including the relay diagnostic device disclosed herein.

[0015] Figure 2 This is a flowchart illustrating an example of diagnostic treatment.

[0016] Figure 3 This is a schematic diagram of the structure of a vehicle drive system, including other relay diagnostic devices.

[0017] Figure 4 This is a flowchart representing other diagnostic procedures.

[0018] Figure 5 This is a flowchart representing other related diagnostic procedures.

[0019] Explanation of reference numerals in the attached figures

[0020] 10 Vehicle drive system, 22 Battery, 24 Power line, 26 Capacitor, 30 EVECU, 40 Battery ECU, 42 Microcomputer, 44 SMRB drive driver, 46 SMRG drive driver, 51 SMR cut-off line, SMR system main relay. Detailed Implementation

[0021] Next, the manner in which this disclosure is implemented will be described. Figure 1 This is a schematic structural diagram of a vehicle drive system 10 including the relay diagnostic device disclosed herein. The vehicle drive system 10 includes a drive unit 12, a battery 22, a capacitor 26, a system main relay SMR, a hybrid power electronic control unit (hereinafter referred to as "HVECU") 30, and a battery electronic control unit (hereinafter referred to as "battery ECU") 40.

[0022] The battery 22 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the drive device 12, which has an engine, motor, etc., via the power line 24. The capacitor 26 is connected to the positive terminal line 24b and the negative terminal line 24g of the power line 24 to smooth the voltage between the positive terminal line 24b and the negative terminal line 24g.

[0023] The system main relay SMR is installed on the capacitor 26 of the power line 24 near the battery 22 side. The system main relay SMR consists of a positive side relay SMRB installed on the positive side line 24b and a negative side relay SMRG installed on the negative side line 24g.

[0024] Although not shown, the HVECU30 is configured as a CPU-centric microprocessor. In addition to the CPU, it includes a ROM for storing processing programs, RAM for temporary data storage, input ports, output ports, and a communication port. The HVECU30 receives signals from various sensors on the drive unit 12 that detect the status of the engine and motor. Based on these signals, it generates control signals and outputs them to the drive unit of the engine and motor. Furthermore, the HVECU30 receives the capacitor voltage Vc from a voltage sensor 28 mounted between the terminals of the capacitor 26. Additionally, the EVECU30 communicates with the battery ECU40 via the communication port.

[0025] The battery ECU 40 includes: a microcomputer (hereinafter referred to as "microcomputer") 42 comprising a CPU, ROM, RAM, input ports, output ports, and communication ports; a driver for driving the positive-side relay (hereinafter referred to as "SMRB driver") 44; a driver for driving the negative-side relay (hereinafter referred to as "SMRG driver") 46; and a relay disconnection circuit 50. The microcomputer 42 communicates with the HVECU 30, receiving instructions from the HVECU 30 and outputting signals to the SMRG driver 44 and SMRG driver 46. Specifically, when the microcomputer 52 receives a connection command for the positive-side relay SMB from the HVECU 30, it outputs a high output to the SMRB driver 44 via signal line 45; when it receives a disconnection command for the positive-side relay SMB from the HVECU 30, it outputs a low output to the SMRB driver 44 via signal line 45. When the SMRB drive driver 44 receives a high output signal from the microcomputer 42, it connects the positive-side relay SMRB; when it receives a low output signal from the microcomputer 42, it disconnects the positive-side relay SMRB. Conversely, when the microcomputer 42 receives a connection command for the negative-side relay SMRG from the HVECU 30, it outputs a high output to the SMRG drive driver 46 via signal line 47; when it receives a disconnect command for the negative-side relay SMRG from the HVECU 30, it outputs a low output to the SMRG drive driver 46 via signal line 47. The SMRG drive driver 46 connects the negative-side relay SMRG when it receives a high output signal from the microcomputer 42, and disconnects the negative-side relay SMRG when it receives a low output signal from the microcomputer 42.

[0026] The relay disconnect circuit 50 directly disconnects the positive-side relay SMRB and the negative-side relay SMRG from the HVECU30, such as... Figure 1As shown, transistors 52, 54, and 56 are included. Additionally, the relay cut-off circuit 50 includes resistors and capacitors, but their illustrations are omitted. The base of transistor 52 is connected to the output port of HVECU 30 via the system main relay cut-off line (hereinafter referred to as the "SMR cut-off line") 51. The emitter of transistor 52 is connected to the voltage source Vcc. The collector of transistor 52 is connected to the base of transistors 54 and 56. The collector of transistor 54 is connected to signal line 45 from microcomputer 42 to SMRB drive driver 44, and the emitter of transistor 54 is grounded. The collector of transistor 56 is connected to signal line 47 from microcomputer 42 to SMRB drive driver 46, and the emitter of transistor 56 is grounded. Therefore, when a high output is sent from HVECU30 to SMR cutoff line 51, even if a high output is sent from microcomputer 42, the potential of signal lines 45 and 47 drops to ground potential. Consequently, a low output signal is input to the SMRB drive driver 44 and SMRG drive driver 46, and the positive-side relay SMRB and negative-side relay SMRG are cut off. Thus, in emergencies such as a malfunction of the microcomputer 42 in battery ECU40, HVECU30 can directly cut off the system main relay SMR.

[0027] In the vehicle drive system 10 of this embodiment, when the start switch is turned on, an on signal is input to the power ECU (not shown), and the power ECU outputs an ST signal to the HVECU 30. After checking for any abnormalities in the drive unit 12, the HVECU 30, having received the ST signal, pre-charges the capacitor 26 and outputs connection commands for the positive-side relay SMB and the negative-side relay SMRG to the battery ECU 40, thereby connecting the positive-side relay SMB and the negative-side relay SMRG. Furthermore, the pre-charging of the capacitor 26 can be performed, for example, by boosting the power from the auxiliary battery connected to the power line 24 via a DC / DC converter and supplying it to the capacitor 26. Then, the HVECU 30 outputs a READY signal to the power ECU indicating that the system startup is complete. Thus, the system startup is complete.

[0028] Next, the welding diagnosis of the system main relay SMR and the diagnosis of SMR disconnection line 51, which are performed when the system stops and disconnects the system main relay SMR, will be described. Figure 2This is a flowchart illustrating an example of the diagnostic processing performed by the HVECU 30. The fusion diagnosis of the system main relay SMR is performed by disconnecting one of the positive-side relay SMB and the negative-side relay SMRG when the system stops, causing capacitor 26 to discharge, and determining whether the capacitor voltage Vc from the voltage sensor 28 has decreased. The discharge of capacitor 26 can be achieved by dissipating it as heat in a device such as the drive unit 12. In this embodiment, the fusion diagnosis of the positive-side relay SMB and the negative-side relay SMRG are performed alternately, one after the other, each time the system stops.

[0029] When performing diagnostic processing, HVECU30 first determines whether a welding diagnosis of the positive-side relay SMB was performed during the last system stop (step S100). If HVECU30 determines that a welding diagnosis of the positive-side relay SMB was performed during the last system stop, it determines that a welding diagnosis of the negative-side relay SMRG will be performed during the current system stop, and outputs a disconnect command for the negative-side relay SMRG to the microcomputer 42 of the battery ECU40 via communication (step S102). The microcomputer 42, which input the disconnect command, disconnects the negative-side relay SMRG by outputting a low output to the SMRG drive driver 46. Then, HVECU30 inputs the capacitor voltage Vc from the voltage sensor 28 (step S104) and determines whether the input capacitor voltage Vc has decreased (step S106). If HVECU30 determines that the capacitor voltage Vc has not decreased, it determines that the negative-side relay SMRG has an abnormality caused by welding (step S108) and ends the diagnostic processing.

[0030] On the other hand, when it is determined that the capacitor voltage Vc has dropped, the HVECU30 determines that the negative side relay SMRG has been normally disconnected and has not been fused (step S110). Then, it performs a diagnosis of the SMR disconnection line 51. That is, the HVECU30 sets the SMR disconnection line 51 to the disconnection side (step S112) and outputs the connection command of the positive side relay SMB and the disconnection command of the negative side relay SMRG to the microcomputer 42 of the battery ECU40 via communication (step S114), and monitors the output status of the SMB drive driver 44 (step S116). When it is determined that the output status of the SMB drive driver 44 is not the output status that causes the positive side relay SMB to disconnect ("No" in step S118), the HVECU30 determines that the SMR disconnection line 51 has not functioned effectively relative to the SMB drive driver 44 and has malfunctioned (step S120), and ends the diagnostic process. On the other hand, when it is determined that the output state of the SMRB drive driver 44 is the output state that cuts off the positive side relay SMRB ("Yes" in step S118), the HVECU 30 determines that the SMR cut-off line 51 is effectively functioning relative to the SMRB drive driver 44 (step S122) and ends the diagnostic process.

[0031] When HVECU30 determines in step S100 that it performed a welding diagnosis on the negative side relay SMRG instead of the positive side relay SMB during the previous system stop, it determines that a welding diagnosis on the positive side relay SMB will be performed during the current system stop, and outputs a disconnect command for the positive side relay SMB to the microcomputer 42 of the battery ECU40 via communication (step S124). The microcomputer 42, having input the disconnect command, disconnects the positive side relay SMB by outputting a low output to the SMB drive driver 44. Then, HVECU30 inputs the capacitor voltage Vc from the voltage sensor 28 (step S126) and determines whether the input capacitor voltage Vc has decreased (step S128). If HVECU30 determines that the capacitor voltage Vc has not decreased, it determines that the positive side relay SMB has generated an abnormality caused by welding (step S130) and ends the diagnostic process.

[0032] On the other hand, when it is determined that the capacitor voltage Vc has dropped, the HVECU30 determines that the positive side relay SMRB is normally disconnected but not fused (step S132) and performs a diagnosis of the SMR disconnection line 51. That is, the HVECU30 sets the SMR disconnection line 51 to the disconnection side (step S134) and outputs the connection command of the negative side relay SMRG and the disconnection command of the positive side relay SMRB to the battery ECU40 via communication (step S136), and monitors the output status of the SMRG drive driver 46 (step S138). When it is determined that the output status of the SMRG drive driver 46 is not the output status that disconnects the negative side relay SMRG ("No" in step S118), the HVECU30 determines that the SMR disconnection line 51 has not functioned effectively relative to the SMRG drive driver 46 and has caused an abnormality (step S120), and ends the diagnostic process. On the other hand, when it is determined that the output state of the SMRG drive driver 46 is the output state that cuts off the negative side relay SMRG ("Yes" in step S118), the HVECU30 determines that the SMR cut-off line 51 is effectively functioning relative to the SMRG drive driver 46 (step S122) and ends the diagnostic process.

[0033] In this way, when the system stops, HVECU30 disconnects one of the positive-side relays SRMB and SMRG by outputting a disconnect command to the microcomputer 42 of battery ECU40, while simultaneously performing a welding test on that relay. Furthermore, after confirming that the relay has disconnected normally without welding, HVECU30 sets the SMR disconnect line 51 to the disconnect side and outputs a connection command to the other relay of the positive-side relay SRMB and negative-side relay SMRG to the microcomputer 42 of battery ECU40, thus diagnosing whether the SMR disconnect line 51 is effectively functioning relative to that other relay. Therefore, reconnection of the positive-side relay SRMB and negative-side relay SMRG for diagnostic purposes is unnecessary, suppressing the reduction in lifespan caused by the increased number of connections of the positive-side relay SRMB and negative-side relay SMRG. Furthermore, since it is confirmed that the relay on one side is not fused and is normally disconnected, even if there is an abnormality in the SMR disconnect line 51 and the relay on the other side is connected according to the connection command from the HVECU 30, a closed circuit can be prevented from forming between the battery 22 and the capacitor 26.

[0034] Next, other embodiments of the relay diagnostic device will be described. Figure 3This is a schematic structural diagram of a vehicle drive system 10B including relay diagnostic devices in other embodiments. As shown, in the vehicle drive system 10B, the system main relay SMR, in addition to the positive-side relay SMB and the negative-side relay SMRG, also includes a pre-charge circuit. This pre-charge circuit is formed by connecting a pre-charge resistor R and a pre-charge relay SMRP in series on the negative-side line 24g of the power line 24, bypassing the negative-side relay SMRG. Furthermore, in addition to the SMB drive driver 44 and the SMRG drive driver 46, the battery ECU 40B also includes a pre-charge relay drive driver (hereinafter referred to as the "SMRP drive driver") 48. This pre-charge relay drive driver 48 connects the pre-charge relay SMRP when a high output signal is input from the microcomputer 42, and disconnects the pre-charge relay SMRP when a low output signal is input from the microcomputer 42. Furthermore, in addition to transistors 52, 54, and 56, the battery ECU 40B also includes a relay cut-off circuit 50B. This relay cut-off circuit 50B has a transistor 58 whose base side is connected to the collector side of transistor 52. The collector side of transistor 58 is connected to signal line 49 from microcomputer 42 to SMRP drive driver 48, and the emitter side of transistor 58 is grounded. Therefore, when a high output is made from HVECU 30 to SMR cut-off line 51, even if a high output is made from microcomputer 42, the potential of signal lines 45, 47, and 49 drops to ground potential. Thus, a low output signal is input to SMRB drive driver 44, SMRG drive driver 46, and SMRP drive driver 48, and the positive-side relay SMRB, negative-side relay SMRG, and pre-charge relay SMRP are cut off.

[0035] Figure 4 and Figure 5 This is a flowchart illustrating the diagnostic processing involved in other embodiments. In other embodiments, the following are performed sequentially: a welding diagnosis of the negative-side relay SMRG, a diagnosis of whether the SMR disconnect line 51 effectively functions for the positive-side relay SMRB, a welding diagnosis of the positive-side relay SMRB, and a diagnosis of whether the SMR disconnect line 51 effectively functions for the negative-side relay SMRG and the pre-charge relay SMRP.

[0036] When performing diagnostic processing, the HVECU30 first communicates with... Figure 2 The same diagnostic process as steps S102-S110 is performed to check the fusion of the negative side relay SMRG (steps S200-S208). When HVECU30 confirms that the negative side relay SMRG is not fused, it connects with... Figure 2The diagnostic process steps S112~S122 are the same, and the diagnosis of whether the SMR cut-off line 51 effectively functions the SMRB drive driver 44 is performed (steps S210~S220).

[0037] When it is confirmed that the SMR disconnect line 51 is effectively functioning for the SMRB drive driver 44, the HVECU 30 outputs a connection command for the precharge relay SMRP to the microcomputer 42 of the battery ECU 40 via communication (step S222). Next, the HVECU 30 inputs the capacitor voltage Vc from the voltage sensor 28 (step S224) and determines whether the input capacitor voltage Vc has increased (step S226). When the HVECU 30 determines that the capacitor voltage Vc has increased, it determines that the positive-side relay SMRB has experienced an abnormality caused by welding (step S228) and ends the diagnostic process. Here, the negative-side relay SMRG is disconnected in steps S200-S208 according to the disconnect command from the HVECU 30 to the microcomputer 42 of the battery ECU 40. At this time, the capacitor voltage Vc decreases, thereby confirming that no abnormality caused by welding has occurred. If the positive-side relay SMRB is not fused, and the SMR disconnect line 51 functions effectively, then through steps S210 and S212, the positive-side relay SMRB is disconnected. Therefore, even if the pre-charge relay SMRP is connected afterward, the capacitor voltage Vc will not rise. Thus, by determining whether the capacitor voltage Vc rises by connecting the pre-charge relay SMRP, it is possible to diagnose whether the positive-side relay SMRB is fused. Furthermore, even if the positive-side relay SMRB is fused, by connecting the pre-charge relay SMRP, the power from battery 22 is supplied to capacitor 26 via pre-charge resistor R, therefore no inrush current is generated in power line 24.

[0038] On the other hand, when it is determined that the capacitor voltage Vc has not risen, the HVECU30 determines that the positive side relay SMRB has been normally disconnected and has not been fused (step S230). Then, it performs a diagnosis of the SMR disconnection line 51. That is, the HVECU30 sets the SMR disconnection line 51 to the disconnection side (step S232) and outputs the connection command of the negative side relay SMRG, the connection command of the precharge relay SMRP, and the disconnection command of the positive side relay SMRB to the battery ECU40 via communication (step S234), and monitors the output status of the SMRG drive driver 46 and the output status of the SMRP drive driver 48 (step S236). When HVECU30 determines that the output state of SMRG drive driver 46 is not in the output state that cuts off the negative side relay SMRG, and determines that the output state of SMRP drive driver 48 is not in the output state that cuts off the pre-charge relay SMRP (No in step S238), it determines that SMR cut-off line 51 has not functioned effectively relative to SMRG drive driver 46 or SMRP drive driver 48 and has caused an abnormality (step S240), and ends the diagnostic process. Here, the positive side relay SMRB is confirmed to be cut off without causing an abnormality caused by welding through steps S210 and S212. Therefore, even if there is an abnormality in SMR cut-off line 51, connecting the negative side relay SMRG according to the connection command of negative side relay SMRG output from HVECU30 to the microcomputer 42 of battery ECU40 through step S234 will not form a closed circuit between battery 22 and capacitor 26, and will not generate inrush current in power line 24.

[0039] On the other hand, when it is determined that the output state of the SMRG drive driver 46 is the output state that cuts off the negative side relay SMRG and the output state of the SMRP drive driver 48 is the output state that cuts off the pre-charge relay SMRP ("Yes" in step S238), the HVECU 30 determines that the SMR cut-off line 51 is effectively functioning relative to the SMRG drive driver 46 and the SMRP drive driver 48 (step S242), and ends the diagnostic process.

[0040] In this way, when the system stops, HVECU30 simultaneously disconnects the negative-side relay SMRG by outputting a disconnect command to the microcomputer 42 of battery ECU40, and performs a welding test on the negative-side relay SMRG. After confirming that the negative-side relay SMRG has not welded and has been normally disconnected, it sets the SMR disconnect line 51 as the disconnect side and outputs a connection command to the positive-side relay SMRB to the microcomputer 42 of battery ECU40 to diagnose whether the SMR disconnect line 51 is effectively functioning relative to the positive-side relay SMRB. Since it is confirmed that the negative-side relay SMRG has not welded and has been normally disconnected, even if the SMR disconnect line 51 is abnormal and the positive-side relay SMRB is connected according to the connection command from HVECU30, a closed circuit can be avoided between battery 22 and capacitor 26. Then, while HVECU30 connects the pre-charge relay SMRP by outputting a connection command to battery ECU40, it performs a welding test on the positive side relay SMB. After confirming that the positive side relay SMB is not welded and is normally disconnected, it sets SMR disconnect line 51 as the disconnect side and outputs connection commands for the negative side relay SMRG and pre-charge relay SMRP to the microcomputer 42 of battery ECU40 to diagnose whether SMR disconnect line 51 effectively functions for the negative side relay SMRG and pre-charge relay SMRP. Since it is confirmed that the positive side relay SMRB is not welded and is normally disconnected, even if there is an abnormality in SMR disconnect line 51 and the negative side relay SMRG and pre-charge relay SMRP are connected according to the connection command from HVECU30, a closed circuit can be avoided between battery 22 and capacitor 26.

[0041] In other embodiments, the HVECU30 sequentially performs diagnoses of the fusion of the negative-side relay SMRG, the effective functioning of the SMR disconnect line 51 relative to the positive-side relay SMRB, the fusion of the positive-side relay SMRB, and the effective functioning of the SMR disconnect line 51 relative to both the negative-side relay SMRG and the pre-charge relay SMRP. However, the HVECU30 may also perform diagnoses of the effective functioning of the SMR disconnect line 51 relative to both the positive-side relay SMRB and the pre-charge relay SMRP after performing fusion diagnoses of the negative-side relay SMRG and the positive-side relay SMRB. In this case, after performing the fusion diagnoses of the negative-side relay SMRG, the HVECU30 outputs a disconnect command for the positive-side relay SMRB to the microcomputer 42 of the battery ECU40, and then outputs a connection command for the pre-charge relay SMRP to the microcomputer 42 of the battery ECU40, thereby performing the fusion diagnoses of the positive-side relay SMRB. Furthermore, the diagnostics of whether the SMR disconnect line 51 effectively functions for the positive side relay SMRB and whether the SMR disconnect line 51 effectively functions for the negative side relay SMRG and the pre-charge relay SMRP can also be performed alternately each time the system stops.

[0042] In other embodiments described above, the pre-charge circuit (pre-charge resistor R and pre-charge relay SMRP) is connected in parallel with the negative-side relay SMRG, but it can also be connected in parallel with the positive-side relay SMRB.

[0043] The above examples illustrate the methods for implementing this disclosure, but this disclosure is not limited to such embodiments and can certainly be implemented in various ways without departing from the spirit of this disclosure.

[0044] Industrial availability

[0045] This disclosure can be applied to the manufacturing industry of relay diagnostic devices.

Claims

1. A relay diagnostic device for a vehicle drive system, the vehicle drive system comprising: a drive unit; a battery; a smoothing capacitor mounted on a power line from the battery to the drive unit; a relay mounted on the power line at a position closer to the battery side than the smoothing capacitor; a driver for driving the relay; a first control unit for controlling the system; a second control unit for receiving instructions from the first control unit and outputting a drive signal to the driver; and a cut-off line connected from the first control unit to the driver, which, by being set as the cut-off side by the first control unit, directly cuts off the relay prior to the drive signal from the second control unit to the driver. In the relay diagnostic device When the first control unit disconnects the battery from the drive device and terminates the system, it outputs a disconnect command for the relay to the second control unit. After diagnosing whether the relay is fused based on whether there is a voltage drop in the smoothing capacitor, it sets the state of the disconnect line to the disconnect side and outputs a connection command for the relay to the second control unit. It monitors the output state of the driver to diagnose whether the disconnect line is functioning effectively.

2. The relay diagnostic device according to claim 1, The relay includes a first relay and a second relay. The first relay is installed on one of the positive and negative terminals of the power line that is closer to the battery side than the smoothing capacitor. The second relay is installed on the other terminal of the positive and negative terminals where the first relay is not installed. As the driver, it has a first driver for driving the first relay and a second driver for driving the second relay. When the first control unit disconnects the battery from the drive device and terminates the system, it outputs a disconnect command for the first relay to the second control unit. It diagnoses whether the first relay is fused based on whether there is a voltage drop in the smoothing capacitor. If the diagnosis result indicates that the first relay is not fused, it sets the state of the disconnect line to the disconnect side and outputs a connection command for the second relay to the second control unit. If the output state of the second driver is in the output state that disconnects the second relay, it is diagnosed that the disconnect line is functioning effectively.

3. The relay diagnostic device according to claim 1, The relay comprises a first relay, a second relay, and a pre-charge circuit. The first relay is installed on one of the positive and negative terminals of the power line that is closer to the battery side than the smoothing capacitor. The second relay is installed on the other terminal of the positive and negative terminals where the first relay is not installed. The pre-charge circuit is formed by connecting a pre-charge resistor in series with a third pre-charge relay, bypassing the second relay. The driver includes a first driver for driving the first relay, a second driver for driving the second relay, and a third driver for driving the third relay. When the first control unit disconnects the battery from the drive device and terminates the system, it outputs a cut-off command for the second relay to the second control unit. It diagnoses whether the second relay is fused based on whether the capacitor voltage drops. If the diagnosis indicates that the second relay is not fused, it sets the cut-off line to the cut-off side and outputs a connection command for the first relay to the second control unit. If the output state of the first driver is in an output state that cuts off the first relay, it is diagnosed that the cut-off line is effectively functioning for the first driver. If the diagnosis indicates that the cut-off line is effectively functioning for the first driver, it outputs a connection command for the third relay to the second control unit. It diagnoses whether the first relay is fused based on whether the capacitor voltage rises. If the diagnosis indicates that the first relay is not fused, it sets the cut-off line to the cut-off side and outputs connection commands for the second and third relays to the second control unit. If the output state of the second driver is in an output state that cuts off the second relay and the output state of the third driver is in an output state that cuts off the third relay, it is diagnosed that the cut-off line is effectively functioning for both the second and third drivers.

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