Relay diagnostic device

Abstract

This method diagnoses whether a circuit breaker wire is effective while the relay is disconnected, without actually connecting the relay. [Solution] In a vehicle power supply system comprising a relay attached to the battery side of the smoothing capacitor of the power line, a driver that drives the relay, a first control unit, a second control unit that receives a command from the first control unit and outputs a drive signal to the driver, and a cutoff wire that the first control unit uses to directly cut off the relay in priority to the drive signal from the second control unit to the driver, the first control unit, when terminating the system, outputs a command to cut off the relay to the second control unit, diagnoses whether the relay is welded based on whether or not there is a voltage drop in the smoothing capacitor, sets the cutoff wire to the cutoff side and outputs a command to connect the relay to the second control unit, and monitors the output status of the driver to diagnose whether or not the cutoff wire is effective.

Description

Technical Field

[0001] The present disclosure relates to a relay diagnostic device.

Background Art

[0002] Conventionally, as this type of relay diagnostic device, there has been proposed a device provided with a running motor, an inverter that drives the running motor, a battery that supplies power to the inverter, first and second system main relays that respectively open and close a pair of power lines connecting the battery and the inverter, a precharge relay connected in series with a precharge resistor in a circuit connected in parallel with the first system main relay, and two device relays that respectively open and close a pair of branch lines branched from the pair of power lines, and a diagnostic processing unit that performs welding diagnosis of the device relays (see, for example, Patent Document 1). During the processing period of system startup, the diagnostic processing unit targets one of the two device relays for diagnosis, keeps the first system main relay and the diagnosed device relay under cutoff control, switches the second system main relay, the precharge relay, and the other device relay that is not the diagnosis target from cutoff to connection control, and then performs welding diagnosis of one device relay by inspecting whether the voltage between the pair of branch lines has risen. Further, during the processing period at the end of use of the branch line, the diagnostic processing unit targets the other device relay of the two device relays for diagnosis, keeps the first system main relay, the second system main relay, and the one device relay that is not the diagnosis target under connection control, switches the other device relay that is the diagnosis target from connection to cutoff control, and then performs welding diagnosis of the other device relay by inspecting whether the voltage between the pair of branch lines has dropped.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In an electric vehicle comprising a drive unit, a storage battery, a smoothing capacitor attached to the power line from the storage battery to the drive unit, a relay attached to the storage battery side of the power line beyond the smoothing capacitor, and a driver that drives the relay, there is a circuit breaker wire connected to the driver from a control unit separate from the control unit that outputs the drive signal to the driver, and this separate control unit directly disconnects the relay. In such a vehicle, it is desirable to diagnose whether the circuit breaker wire is functioning effectively, in addition to diagnosing the welding of the relay. Diagnosing the welding of the relay when the system stops is performed by disconnecting the relay and determining whether the voltage of the smoothing capacitor drops. Therefore, if the circuit breaker wire is set to the disconnected position while the relay is connected and the diagnosis of whether the circuit breaker wire is functioning effectively is performed by determining whether the voltage of the smoothing capacitor drops, it will be necessary to reconnect the relay in order to perform the welding diagnosis of the relay afterward, which will increase the number of times the relay is connected and may reduce the lifespan of the relay.

[0005] The relay diagnostic device of this disclosure is primarily intended to diagnose whether a circuit breaker is effective when the relay is disconnected, without actually connecting the relay. [Means for solving the problem]

[0006] The relay diagnostic device of this disclosure employs the following means to achieve the main objective described above.

[0007] The relay diagnostic device of the present disclosure is a relay diagnostic device in a vehicle drive system, comprising: a drive unit; a storage battery; a smoothing capacitor attached to a power line from the storage battery to the drive unit; a relay attached to the power line on the storage battery side of the smoothing capacitor; a driver for driving the relay; a first control unit for controlling the system; a second control unit that receives a command from the first control unit and outputs a drive signal to the driver; and a cutoff wire connected from the first control unit to the driver, which is set to the cutoff side by the first control unit to directly cut off the relay in priority to the drive signal from the second control unit to the driver, wherein the first control unit, when disconnecting the storage battery from the drive unit to terminate the system, outputs a command to cut off the relay to the second control unit, diagnoses whether the relay is welded based on whether or not there is a voltage drop in the smoothing capacitor, sets the state of the cutoff wire to the cutoff side and outputs a command to connect the relay to the second control unit, and diagnoses whether or not the cutoff wire is functioning effectively by monitoring the output state of the driver.

[0008] In the relay diagnostic device of this disclosure, when the battery is disconnected from the drive unit and the system is terminated, the first control unit outputs a relay disconnection command to the second control unit and diagnoses whether the relay is welded based on whether or not there is a voltage drop in the smoothing capacitor. Subsequently, the first control unit sets the state of the disconnection wire to the disconnected side and outputs a relay connection command to the second control unit, and diagnoses whether or not the disconnection wire is functioning effectively by monitoring the output state of the driver. This makes it possible to diagnose whether or not the disconnection wire is functioning effectively while the relay is disconnected, without actually connecting the relay. Furthermore, when the battery is disconnected from the drive unit and the system is terminated, the relay is connected, so by performing a relay welding diagnosis first and then diagnosing whether or not the disconnection wire is effective, it is possible to eliminate the need to reconnect the relay for relay welding diagnosis.

[0009] In the relay diagnostic device of this disclosure, the relays include a first relay attached to one of the positive and negative lines of the power line on the battery side from the smoothing capacitor, and a second relay attached to the other of the positive and negative lines on which the first relay is not attached. The drivers include 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 to terminate the system, it outputs a cutoff command for the first relay to the second control unit, diagnoses whether the first relay is welded based on whether or not there is a voltage drop in the smoothing capacitor, and if a diagnosis result is obtained that there is no welding of the first relay, it sets the state of the cutoff wire to the cutoff 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 an output state that cuts off the second relay, it may diagnose that the cutoff wire is functioning effectively. Since the first relay is confirmed to be disconnected and not welded, even if there is a problem with the disconnection wire and the second relay is connected by a connection command for the second relay, a closed circuit will not be formed between the smoothing capacitor and the battery. As a result, damage to the relay due to inrush current can be avoided.

[0010] The relay diagnostic device of this disclosure includes, as relays, a first relay attached to one of the positive and negative lines of the power line on the battery side from the smoothing capacitor, a second relay attached to the other of the positive and negative lines on which the first relay is not attached, and a precharge circuit in which a precharge resistor and a third relay for precharging are connected in series to bypass the second relay, and as drivers, 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, and when the battery is disconnected from the drive device and the system is terminated, the first control unit outputs a cutoff command for the second relay to the second control unit and diagnoses whether the second relay is welded based on whether or not there is a voltage drop in the capacitor, and a diagnosis result is obtained that there is no welding of the second relay If this occurs, the circuit breaker wire may be set to the circuit breaker side and a connection command for the first relay may be output to the second control unit. If the output state of the first driver is in an output state that causes the first relay to shut off, it may be diagnosed that the circuit breaker wire functions effectively for the first driver. If a diagnosis result is obtained indicating that the circuit breaker wire functions effectively for the first driver, a connection command for the third relay may be output to the second control unit to diagnose whether the first relay is welded based on whether the capacitor voltage rises or not. If a diagnosis result is obtained indicating that the first relay is not welded, the circuit breaker wire may be set to the circuit breaker side and connection commands for the second and third relays may be output to the second control unit. If the output state of the second driver is in an output state that causes the second relay to shut off and the output state of the third driver is in an output state that causes the third relay to shut off, it may be diagnosed that the circuit breaker wire functions effectively for the second and third drivers. In other words, the first control unit first outputs a tripping command to the second relay, performs a welding diagnosis of the second relay to confirm that there is no welding of the second relay, and then sets the tripping wire to the tripping side and outputs a connection command to the first relay to diagnose whether the tripping wire is functioning effectively for the first driver.As a result, even if the third relay is welded and there is a problem with the disconnection wire, causing the first relay to be connected by a connection command for the first relay, only a closed circuit is formed between the battery and the smoothing capacitor via the precharge resistor, preventing inrush current from occurring in the power line. Furthermore, the first control unit outputs a connection command for the third relay, performs a welding diagnosis of the first relay (diagnosing whether the voltage of the smoothing capacitor rises due to precharging) to confirm that the first relay is not welded and is disconnected, then sets the disconnection wire to the disconnected position and outputs connection commands for the second and third relays to diagnose whether the disconnection wire functions effectively for the second and third drivers. As a result, even if there is a problem with the disconnection wire and the second or third relay is connected by a connection command for the second or third relay, a closed circuit is not formed between the battery and the smoothing capacitor. In addition, since the diagnosis of whether the disconnection wire functions effectively for the second and third drivers is performed together, the time required for diagnosis can be shortened. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of a vehicle drive system including the relay diagnostic device of this disclosure. [Figure 2] This is a flowchart showing an example of a diagnostic process. [Figure 3] This is a schematic diagram of a vehicle drive system, including other relay diagnostic devices. [Figure 4] The flowchart shows other diagnostic processes. [Figure 5] This flowchart shows other related diagnostic processes. [Modes for carrying out the invention]

[0012] Next, an embodiment for implementing this disclosure will be described. Figure 1 is a schematic diagram of a vehicle drive system 10 including the relay diagnostic device of this disclosure. The vehicle drive system 10 comprises a drive unit 12, a battery 22, a capacitor 26, a system main relay SMR, a hybrid electronic control unit (hereinafter referred to as "HVECU") 30, and a battery electronic control unit (hereinafter referred to as "battery ECU") 40.

[0013] 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 unit 12, which has an engine or motor, via a power line 24. The capacitor 26 is connected to the positive electrode line 24b and the negative electrode line 24g of the power line 24, and smooths the voltage between the positive electrode line 24b and the negative electrode line 24g.

[0014] The system main relay SMR is mounted on the battery 22 side of the power line 24, beyond the capacitor 26. The system main relay SMR consists of a positive-side relay SMRB mounted on the positive-side line 24b and a negative-side relay SMRG mounted on the negative-side line 24g.

[0015] HVECU30, although not shown in the diagram, is configured as a microprocessor centered around a CPU. In addition to the CPU, it includes ROM for storing processing programs, ROM for temporarily storing data, input ports, output ports, and communication ports. HVECU30 receives signals from various sensors that detect the status of the engine and motor of the drive unit 12, generates control signals based on the signals received from the various sensors, and outputs them to the drive unit of the engine and motor. HVECU30 also receives the capacitor voltage Vc from a voltage sensor 28 attached between the terminals of the capacitor 26. Furthermore, HVECU30 communicates with the battery ECU40 via its communication port.

[0016] The battery ECU 40 includes a microcomputer (hereinafter referred to as "microcontroller") 42, which includes a CPU, ROM, RAM, input ports, output ports, and communication ports; a positive-side relay drive driver (hereinafter referred to as "SMRB drive driver") 44; a negative-side relay drive driver (hereinafter referred to as "SMRG drive driver") 46; and a relay disconnection circuit 50. The microcontroller 42 communicates with the HVECU 30 and outputs signals to the SMRG drive driver 44 and SMRG drive driver 46 upon receiving commands from the HVECU 30. Specifically, when the microcontroller 52 receives a connection command for the positive-side relay SMRB from the HVECU 30, it outputs a high signal to the SMRB drive driver 44 via the signal line 45, and when it receives a disconnection command for the positive-side relay SMRB from the HVECU 30, it outputs a low signal to the SMRB drive driver 44 via the signal line 45. The SMRB drive driver 44 connects the positive side relay SMRB when it receives a high output signal from the microcontroller 42, and disconnects the positive side relay SMRB when it receives a low output signal from the microcontroller 42. The microcontroller 42 also outputs a high signal to the SMRG drive driver 46 via signal line 47 when it receives a connection command for the negative side relay SMRG from the HVECU 30, and outputs a low signal to the SMRG drive driver 46 via signal line 47 when it receives a disconnection command for the negative side relay SMRG from the HVECU 30. The SMRG drive driver 46 connects the negative side relay SMRG when it receives a high output signal from the microcontroller 42, and disconnects the negative side relay SMRG when it receives a low output signal from the microcontroller 42.

[0017] The relay interruption circuit 50 directly interrupts the positive-side relay SMRB and the negative-side relay SMRG from the HVECU 30, and has transistors 52, 54, and 56 as shown in Figure 1. The relay interruption circuit 50 also includes resistors and capacitors, but these are not shown in the illustration. The base of transistor 52 is connected to the output port of the HVECU 30 via the system main relay interruption line (hereinafter referred to as the "SMR interruption line") 51, the emitter side of transistor 52 is connected to the voltage source Vcc, and the collector side of transistor 52 is connected to the base side of transistor 54 and the base side of transistor 56. The collector side of transistor 54 is connected to the signal line 45 from the microcontroller 42 to the SMRB drive driver 44, and the emitter side of transistor 54 is grounded. The collector side of transistor 56 is connected to the signal line 47 from the microcontroller 42 to the SMRG drive driver 46, and the emitter side of transistor 56 is grounded. As a result, when a high output is sent from HVECU30 to the SMR cutoff line 51, even if a high output is also sent from the microcontroller 42, the potential of the signal lines 45 and 47 drops to ground. Therefore, a low output signal is input to the SMRB drive driver 44 and the SMRG drive driver 46, and the positive side relay SMRB and the negative side relay SMRG are tripped. Consequently, HVECU30 can directly trip the system main relay SMR in emergencies, such as when a failure occurs in the microcontroller 42 of the battery ECU40.

[0018] In the vehicle drive system 10 of this embodiment, when the start switch is turned on, an ON signal is input to a power supply ECU (not shown), and an ST signal is output from the power supply ECU to the HVECU 30. After receiving the ST signal, the HVECU 30 checks for any abnormalities in the drive unit 12, etc., then precharges the capacitor 26 and outputs connection commands for the positive side relay SMRB and the negative side relay SMRG to the battery ECU 40, thereby connecting the positive side relay SMRB and the negative side relay SMRG. The precharge of the capacitor 26 can be performed, for example, by boosting the power from an auxiliary battery connected to the power line 24 via a DC / DC converter and supplying it to the capacitor 26. The HVECU 30 then outputs a READY signal to the power supply ECU indicating that the system startup is complete. Thus, the system startup is completed.

[0019] Next, we will describe the welding diagnosis of the system main relay SMR and the diagnosis of the SMR shutoff wire 51, which are performed when the system main relay SMR is shut off during system shutdown. Figure 2 is a flowchart of an example of the diagnostic process performed by the HVECU 30. The welding diagnosis of the system main relay SMR is performed by shutting off one of the positive-side relay SMRB and the negative-side relay SMRG during system shutdown, discharging the capacitor 26, and determining whether the capacitor voltage Vc from the voltage sensor 28 has decreased. The discharge of the capacitor 26 can be performed by dissipating the heat from equipment in the drive unit 12. In this embodiment, the welding diagnosis of the positive-side relay SMRB and the welding diagnosis of the negative-side relay SMRG are performed alternately, one at a time, each time the system is shut off.

[0020] When the diagnostic process is executed, the HVECU 30 first determines whether or not it executed the welding diagnosis of the positive-side relay SMRB at the previous system stop (step S100). When the HVECU 30 determines that it executed the welding diagnosis of the positive-side relay SMRB at the previous system stop, it decides to execute the welding diagnosis of the negative-side relay SMRG at the current system stop, and outputs a disconnection command for the negative-side relay SMRG to the microcomputer 42 of the battery ECU 40 via communication (step S102). The microcomputer 42 that has received the disconnection command outputs a low output to the SMRG drive driver 46 to disconnect the negative-side relay SMRG. Then, the HVECU 30 inputs the capacitor voltage Vc from the voltage sensor 28 (step S104) and determines whether or not the input capacitor voltage Vc has decreased (step S106). When the HVECU 30 determines that the capacitor voltage Vc has not decreased, it determines that an abnormality due to welding has occurred in the negative-side relay SMRG (step S108) and ends the diagnostic process.

[0021] On the other hand, when the HVECU 30 determines that the capacitor voltage Vc has decreased, it determines that the negative-side relay SMRG has been normally disconnected and is not welded (step S110). Next, it performs a diagnosis of the SMR disconnection line 51. That is, the HVECU 30 sets the SMR disconnection line 51 to the disconnection side (step S112), and outputs a connection command for the positive-side relay SMRB and a disconnection command for the negative-side relay SMRG to the microcomputer 42 of the battery ECU 40 via communication (step S114), and monitors the output state of the SMRB drive driver 44 (step S116). When the HVECU 30 determines that the output state of the SMRB drive driver 44 is not an output state that disconnects the positive-side relay SMRB (NO in step S118), it determines that the SMR disconnection line 51 is not functioning effectively for the SMRB drive driver 44 and that an abnormality has occurred (step S120) and ends the diagnostic process. On the other hand, when the HVECU 30 determines that the output state of the SMRB drive driver 44 is an output state that disconnects the positive-side relay SMRB (YES in step S118), it determines that the SMR disconnection line 51 is functioning effectively for the SMRB drive driver 44 (step S122) and ends the diagnostic process.

[0022] When the HVECU 30 determines in step S100 that the welding diagnosis of the negative-side relay SMRG instead of the positive-side relay SMRB was executed at the previous system stop, it determines that the welding diagnosis of the positive-side relay SMRB will be executed at the current system stop, and outputs a disconnection command for the positive-side relay SMRB to the microcomputer 42 of the battery ECU 40 by communication (step S124). The microcomputer 42 that has received the disconnection command outputs a low output to the SMRB drive driver 44 to disconnect the positive-side relay SMRB. Then, the HVECU 30 inputs the capacitor voltage Vc from the voltage sensor 28 (step S126), and determines whether or not the input capacitor voltage Vc has decreased (step S128). When the HVECU 30 determines that the capacitor voltage Vc has not decreased, it determines that there is an abnormality due to welding in the positive-side relay SMRB (step S130), and ends the diagnosis process.

[0023] On the other hand, when the HVECU 30 determines that the capacitor voltage Vc has decreased, it determines that the positive-side relay SMRB has been normally disconnected and is not welded (step S132), and performs a diagnosis of the SMR disconnection line 51. That is, the HVECU 30 sets the SMR disconnection line 51 to the disconnection side (step S134), outputs a connection command for the negative-side relay SMRG and a disconnection command for the positive-side relay SMRB to the battery ECU 40 by communication (step S136), and monitors the output state of the SMRG drive driver 46 (step S138). When the HVECU 30 determines that the output state of the SMRG drive driver 46 is not an output state that disconnects the negative-side relay SMRG (NO in step S118), it determines that the SMR disconnection line 51 is not functioning effectively and an abnormality has occurred in the SMRG drive driver 46 (step S120), and ends the diagnosis process. On the other hand, when the HVECU 30 determines that the output state of the SMRG drive driver 46 is an output state that disconnects the negative-side relay SMRG (YES in step S118), it determines that the SMR disconnection line 51 is functioning effectively in the SMRG drive driver 46 (step S122), and ends the diagnosis process.

[0024] In this way, when the system is shut down, the HVECU30 disconnects one of the two relays, the positive-side relay SRMB and the negative-side relay SMRG, by outputting a disconnection command to the microcontroller 42 of the battery ECU40, while diagnosing whether the relay is welded or not. After confirming that the relay is not welded and is properly disconnected, the HVECU30 sets the SMR disconnection wire 51 to the disconnected position and outputs a connection command to the microcontroller 42 of the battery ECU40 for the other relay, diagnoses whether the SMR disconnection wire 51 is functioning effectively for the other relay. Therefore, reconnection of the positive-side relay SRMB and the negative-side relay SMRG for diagnosis is unnecessary, and the reduction in lifespan due to an increase in the number of connection cycles of the positive-side relay SRMB and the negative-side relay SMRG can be suppressed. Furthermore, since it is confirmed that one of the relays is not welded and is properly interrupted, even if there is a problem with the SMR interruption wire 51 and the other relay is connected by a connection command from the HVECU 30, a closed circuit will not be formed between the battery 22 and the capacitor 26.

[0025] Next, a relay diagnostic device according to another embodiment will be described. Figure 3 is a schematic diagram of a vehicle drive system 10B including a relay diagnostic device according to another embodiment. As shown in the figure, in the vehicle drive system 10B, the system main relay SMR includes a precharge circuit in which a precharge resistor R and a precharge relay SMRP are connected in series to the negative terminal line 24g of the power line 24, bypassing the negative terminal relay SMRG, in addition to the positive terminal relay SMRB and the negative terminal relay SMRG. The battery ECU 40B also includes a precharge relay driver (hereinafter referred to as "SMRP driver") 48 in addition to the SMRB drive driver 44 and the SMRG drive driver 46, which connects the precharge relay SMRP when a high output signal is input from the microcontroller 42 and disconnects the precharge relay SMRP when a low output signal is input from the microcontroller 42. Furthermore, the battery ECU 40B includes a relay disconnection circuit 50B having transistors 52, 54, and 56, as well as a transistor 58 whose base side is connected to the collector side of transistor 52. The collector side of transistor 58 is connected to the signal line 49 from the microcontroller 42 to the SMRP drive driver 48, and the emitter side of transistor 58 is grounded. As a result, when a high output is given from HVECU 30 to the SMR cutoff line 51, even if a high output is given from the microcontroller 42, the potential of signal lines 45, 47, and 49 drops to ground, so a low output signal is input to the SMRB drive driver 44, SMRG drive driver 46, and SMRP drive driver 48, and the positive side relay SMRB, the negative side relay SMRG, and the precharge relay SMRP are cut off.

[0026] Figures 4 and 5 are flowcharts illustrating diagnostic processes according to other embodiments. In these embodiments, the following steps are performed in this order: welding diagnosis of the negative electrode relay SMRG, diagnosis of whether the SMR shutoff wire 51 functions effectively for the positive electrode relay SMRB, welding diagnosis of the positive electrode relay SMRB, and diagnosis of whether the SMR shutoff wire 51 functions effectively for the negative electrode relay SMRG and the precharge relay SMRP.

[0027] When the diagnostic process is executed, the HVECU30 first performs a welding diagnosis of the negative electrode relay SMRG by the same process as steps S102 to S110 of the diagnostic process in Figure 2 (steps S200 to S208). After confirming that the negative electrode relay SMRG is not welded, the HVECU30 performs a diagnosis to determine whether the SMR cutoff wire 51 functions effectively for the SMRB drive driver 44 by the same process as steps S112 to S122 of the diagnostic process in Figure 2 (steps S210 to S220).

[0028] When the HVECU30 confirms that the SMR cutoff wire 51 is functioning effectively with respect to the SMRB drive driver 44, it outputs a connection command for the precharge relay SMRP to the microcontroller 42 of the battery ECU40 via communication (step S222). Next, the HVECU30 receives the capacitor voltage Vc from the voltage sensor 28 as input (step S224) and determines whether the input capacitor voltage Vc has risen or not (step S226). If the HVECU30 determines that the capacitor voltage Vc has risen, it determines that an abnormality due to welding has occurred in the positive electrode relay SMRB (step S228) and terminates the diagnostic process. At this point, the negative electrode relay SMRG was cut off in steps S200 to S208 by a cutoff command from the HVECU30 to the microcontroller 42 of the battery ECU40, and it was confirmed that no abnormality due to welding had occurred because the capacitor voltage Vc decreased at that time. If the positive-side relay SMRB is not welded and the SMR disconnection wire 51 is functioning correctly, the positive-side relay SMRB will be disconnected in steps S210 and S212. Therefore, even if the pre-charge relay SMRP is connected afterward, the capacitor voltage Vc will not rise. For this reason, by determining whether or not the capacitor voltage Vc rises when the pre-charge relay SMRP is connected, it is possible to diagnose whether or not the positive-side relay SMRB is welded. Even if the positive-side relay SMRB is welded, when the pre-charge relay SMRP is connected, power from the battery 22 is supplied to the capacitor 26 via the pre-charge resistor R, so no inrush current is generated in the power line 24.

[0029] On the other hand, if the HVECU30 determines that the capacitor voltage Vc has not risen, it determines that the positive side relay SMRB is properly shut off and not welded (step S230), and then diagnoses the SMR shut-off wire 51. Specifically, the HVECU30 sets the SMR shut-off wire 51 to the shut-off position (step S232), and outputs the connection command for the negative side relay SMRG, the connection command for the pre-charge relay SMRP, and the shut-off command for 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). If the HVECU30 determines that the output state of the SMRG drive driver 46 is not in a state that would interrupt the negative-side relay SMRG, or that the output state of the SMRP drive driver 48 is not in a state that would interrupt the pre-charge relay SMRP (NO in step S238), it determines that the SMR interruption wire 51 is not functioning effectively for the SMRG drive driver 46 or the SMRP drive driver 48, and that an abnormality has occurred (step S240), and terminates the diagnostic process. At this point, the positive-side relay SMRB has been interrupted in steps S210 and S212, and it has been confirmed that no abnormality has occurred due to welding. Therefore, even if there is an abnormality in the SMR interruption wire 51 and the negative-side relay SMRG is connected by the connection command for the negative-side relay SMRG output from the HVECU30 to the microcontroller 42 of the battery ECU40 in step S234, a closed circuit will not be formed between the battery 22 and the capacitor 26, and no inrush current will occur in the power line 24.

[0030] On the other hand, if the HVECU 30 determines that the output state of the SMRG drive driver 46 is such that it shuts off the negative side relay SMRG, and that the output state of the SMRP drive driver 48 is such that it shuts off the precharge relay SMRP (YES in step S238), it determines that the SMR shut-off wire 51 is functioning effectively for both the SMRG drive driver 46 and the SMRP drive driver 48 (step S242), and terminates the diagnostic process.

[0031] In this way, when the system is stopped, the HVECU30 performs a welding diagnosis of the negative electrode relay SMRG while shutting it off by outputting a shut-off command to the microcontroller 42 of the battery ECU40. After confirming that the negative electrode relay SMRG is not welded and is properly shut off, the HVECU30 sets the SMR shut-off wire 51 to the shut-off position and outputs a connection command to the microcontroller 42 of the battery ECU40 for the positive electrode relay SMRB, diagnosing whether the SMR shut-off wire 51 functions effectively for the positive electrode relay SMRB. Since it has been confirmed that the negative electrode relay SMRG is not welded and is properly shut off, even if there is a problem with the SMR shut-off wire 51 and the positive electrode relay SMRB is connected by a connection command from the HVECU30, a closed circuit will not be formed between the battery 22 and the capacitor 26. Then, the HVECU30, while connecting the pre-charge relay SMRP based on the output of a connection command to the battery ECU40, performs a welding diagnosis of the positive side relay SMRB. After confirming that the positive side relay SMRB is not welded and is properly interrupted, the HVECU30 sets the SMR interruption wire 51 to the interrupted position and outputs connection commands for the negative side relay SMRG and pre-charge relay SMRP to the microcontroller 42 of the battery ECU40 to diagnose whether the SMR interruption wire 51 is functioning effectively for the negative side relay SMRG and pre-charge relay SMRP. Since it has been confirmed that the positive side relay SMRB is not welded and is properly interrupted, even if there is a problem with the SMR interruption wire 51 and the negative side relay SMRG or pre-charge relay SMRP is connected by a connection command from the HVECU30, a closed circuit will not be formed between the battery 22 and the capacitor 26.

[0032] In other embodiments, the HVECU30 sequentially performs welding diagnosis of the negative electrode relay SMRG, diagnosis of whether the SMR cutoff wire 51 functions effectively for the positive electrode relay SMRB, welding diagnosis of the positive electrode relay SMRB, and diagnosis of whether the SMR cutoff wire 51 functions effectively for the negative electrode relay SMRG and precharge relay SMRP. However, the HVECU30 may first perform welding diagnosis of the negative electrode relay SMRG and welding diagnosis of the positive electrode relay SMRB, and then sequentially perform diagnosis of whether the SMR cutoff wire 51 functions effectively for the positive electrode relay SMRB and diagnosis of whether the SMR cutoff wire 51 functions effectively for the negative electrode relay SMRG and precharge relay SMRP. In this case, the HVECU30 can perform a welding diagnosis of the negative side relay SMRG, then output a shut-off command for the positive side relay SMRB to the microcontroller 42 of the battery ECU40, and then output a connection command for the pre-charge relay SMRP to the microcontroller 42 of the battery ECU40 to perform a welding diagnosis of the positive side relay SMRB. Note that the diagnosis of whether the SMR shut-off wire 51 functions effectively for the positive side relay SMRB and the diagnosis of whether the SMR shut-off wire 51 functions effectively for the negative side relay SMRG and pre-charge relay SMRP may be performed alternately each time the system is shut down.

[0033] In the other embodiments described above, the precharge circuit (precharge resistor R and precharge relay SMRP) was connected in parallel with the negative-side relay SMRG, but it may also be connected in parallel with the positive-side relay SMRB.

[0034] The above describes the forms for implementing this disclosure using examples, but this disclosure is not limited in any way to these examples, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0035] This disclosure is applicable to the relay diagnostic equipment manufacturing industry. [Explanation of Symbols]

[0036] 10 Vehicle drive system, 22 Battery, 24 Power line, 26 Capacitor, 30 EVECU, 40 Battery ECU, 42 Microcontroller, 44 SMRB drive driver, 46 SMRG drive driver, 51 SMR break wire, SMR, System main relay.

Claims

1. A relay diagnostic device for a vehicle drive system, comprising: a drive unit; a storage battery; a smoothing capacitor attached to a power line from the storage battery to the drive unit; a relay attached to the power line on the storage battery side of the smoothing capacitor; a driver for driving the relay; a first control unit for controlling the system; a second control unit that receives a command from the first control unit and outputs a drive signal to the driver; and a disconnect wire connected from the first control unit to the driver, which, when set to the disconnected side by the first control unit, directly disconnects the relay in priority to the drive signal from the second control unit to the driver, When the first control unit disconnects the battery from the drive device and terminates the system, it outputs a relay disconnection command to the second control unit, diagnoses whether the relay is welded based on whether or not the voltage of the smoothing capacitor drops, sets the state of the disconnection wire to the disconnected side, outputs a relay connection command to the second control unit, and diagnoses whether or not the disconnection wire is functioning effectively by monitoring the output state of the driver. Relay diagnostic device.

2. A relay diagnostic device according to claim 1, The relay comprises a first relay attached to one of the positive and negative lines of the power line, on the battery side of the smoothing capacitor, and a second relay attached to the other line of the positive and negative lines, on which the first relay is not attached. The driver comprises 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 cutoff command for the first relay to the second control unit, diagnoses whether the first relay is welded based on whether or not the voltage of the smoothing capacitor drops, and if it obtains a diagnosis that the first relay is not welded, it sets the state of the cutoff wire to the cutoff side and outputs a connection command for the second relay to the second control unit, and diagnoses that the cutoff wire is functioning effectively when the output state of the second driver is in an output state that cuts off the second relay. Relay diagnostic device.

3. A relay diagnostic device according to claim 1, The relay comprises a first relay attached to one of the positive and negative lines of the power line on the battery side from the smoothing capacitor, a second relay attached to the other of the positive and negative lines on which the first relay is not attached, and a precharge circuit in which a precharge resistor and a third relay for precharging are connected in series to bypass the second relay. The driver comprises 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 cutoff command for the second relay to the second control unit to diagnose whether the second relay is welded based on the voltage drop of the capacitor, and if a diagnosis result is obtained indicating that the second relay is not welded, it sets the cutoff wire to the cutoff side and outputs a connection command for the first relay to the second control unit, and if the output state of the first driver is in an output state that cuts off the first relay, it diagnoses that the cutoff wire is functioning effectively for the first driver, and outputs a diagnosis to the first driver indicating that the cutoff wire is functioning effectively. If a diagnostic result is obtained, a connection command for the third relay is output to the second control unit to diagnose whether the first relay is welded based on whether or not the capacitor voltage rises. If a diagnostic result is obtained indicating that the first relay is not welded, the disconnect wire is set to the disconnected position and connection commands for the second and third relays are output to the second control unit. If the output state of the second driver is in a state that disconnects the second relay and the output state of the third driver is in a state that disconnects the third relay, it is diagnosed that the disconnect wire is functioning effectively for the second and third drivers. Relay diagnostic device.

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