Method for detecting ON sticking of the system main relay

Abstract

This invention provides a method for detecting the ON state of a system main relay, which can detect the ON state of the system main relay without being affected by residual voltage, even when there is a capacitor component in the power supply circuit. [Solution] A method for detecting ON sticking of a system main relay that controls the power transfer state of a lithium-ion battery, comprising: a first step of using a motor generator capable of charging a lithium-ion battery by voltage control to turn the vehicle's ignition switch to the ON state and then giving an OFF state instruction to the system main relay; a second step of voltage control of the motor generator to output a target voltage higher than the battery voltage of the lithium-ion battery; and a third step of determining that the system main relay is stuck ON if there is a change in battery voltage after the second step.

Description

Technical Field

[0001] The present disclosure relates to a method for detecting ON sticking of a system main relay that controls the power supply and reception state of a battery.

Background Art

[0002] Patent Document 1 discloses a technique for detecting a stuck state of a power relay provided in a power supply circuit. In this technique, after operating the power relay to OFF in response to an OFF input of an ignition switch, if the power supply voltage of the power supply circuit is equal to or higher than a determination threshold value, it is described that it is determined that the power relay is in an ON stuck state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, detection of ON sticking of the power relay is performed by comparing the power supply voltage of the power supply circuit with a determination threshold value. Therefore, when there is a capacitor component that can store charge on the power supply circuit, if there is charge remaining in the capacitor at the time of determining the presence or absence of ON sticking of the power relay, such as immediately after the ignition switch is turned OFF, there is a problem that an incorrect determination of ON sticking may be made due to the influence of the residual voltage.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a method for detecting ON sticking of a system main relay that can detect the ON sticking state of the system main relay without being affected by the residual voltage even when there is a capacitor component on the power supply circuit.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the disclosed technology is a method for detecting ON sticking of a system main relay that controls the power transfer state of a lithium-ion battery, comprising: a first step of using a motor generator capable of charging a lithium-ion battery by voltage control to turn the vehicle's ignition switch to the ON state and then giving an OFF state instruction to the system main relay; a second step of voltage control of the motor generator to output a target voltage higher than the battery voltage of the lithium-ion battery; and a third step of determining that the system main relay is stuck ON if there is a change in battery voltage after the second step. [Effects of the Invention]

[0007] According to the method for detecting the ON state of the system main relay described above, the ON state of the system main relay can be detected without being affected by residual voltage, even when there is a capacitor component in the power supply circuit. [Brief explanation of the drawing]

[0008] [Figure 1] Schematic diagram for realizing an ON-fixed detection method for a system main relay according to one embodiment of the present disclosure. [Figure 2] This flowchart illustrates the process for detecting when the main relay of this system is stuck in the ON position. [Figure 3] This timing chart explains the method for detecting the ON-fixed state of the main relay in this system. [Modes for carrying out the invention]

[0009] The method for detecting ON sticking of the system main relay described herein involves controlling the voltage of the motor generator when the vehicle's ignition switch is turned ON, and detecting a voltage rise in the lithium-ion battery before torque is generated by the motor generator, thereby determining whether the system main relay is stuck ON. This makes it possible to determine whether the system main relay is stuck ON without being affected by residual voltage due to the capacitor component in the power supply circuit. The embodiments of this disclosure will be described in detail below with reference to the drawings.

[0010] <Embodiment> [composition] Figure 1 is a schematic diagram showing a system configuration for realizing an ON-fixed detection method for a system main relay according to one embodiment of the present disclosure. The system illustrated in Figure 1 comprises an engine 10, a motor generator (MG) 20, an MG control unit 30, a lithium-ion battery 40, a system main relay (SMR) 50, a control microcontroller 60, an auxiliary battery 70, a DC-DC converter (DDC) 80, and a capacitor 90. In Figure 1, signal lines related to power are shown as solid lines, and signal lines related to control / communication are shown as dotted lines.

[0011] Engine 10 is an internal combustion engine that serves as the power source for the vehicle. This engine 10 transmits the necessary power (rotation) to the motor generator 20.

[0012] The motor generator 20 is an electric generator that combines an electric function for starting the engine 10 and a power generation function that generates electricity driven by the power or regenerative operation of the engine 10. The operation (power generation / discharge) of this motor generator 20 is controlled by instructions from the MG control unit 30.

[0013] The MG control unit 30 performs MG control based on instructions from the control microcontroller 60. This MG control includes voltage control, which controls the output voltage of the lithium-ion battery 40, "MG voltage," to match the MG target voltage instructed by the control microcontroller 60, and torque control, which controls the amount of power generated by the motor generator 20 according to the MG target torque instructed by the control microcontroller 60.

[0014] The lithium-ion battery 40 is a rechargeable secondary battery. The output voltage of this lithium-ion battery 40, known as the "battery voltage," is monitored by the control microcontroller 60. Examples of lithium-ion batteries 40 installed in a vehicle include high-voltage batteries and drive batteries.

[0015] The system main relay 50 is a switching element for controlling the power transfer state of the lithium-ion battery 40, and is installed between the lithium-ion battery 40 and the MG control unit 30. An example of the system main relay 50 is a mechanical relay having movable terminals and fixed terminals. This system main relay 50 can switch between a state in which the input / output terminals are electrically connected (ON state) and a state in which the input / output terminals are electrically disconnected (OFF state) based on instructions from the control microcontroller 60.

[0016] The control microcontroller 60 controls the electrical connection state between the lithium-ion battery 40, the MG control unit 30, and the DC-DC converter 80 by operating the ON / OFF operation of the system main relay 50 using relay control signals. The control microcontroller 60 also performs the necessary communication to control the MG control unit 30. This communication is performed, for example, using CAN (Controller Area Network) communication. Furthermore, the control microcontroller 60 can determine whether the movable and fixed terminals of the system main relay 50 are stuck together or not. In addition, the control microcontroller 60 monitors the battery voltage of the lithium-ion battery 40.

[0017] The auxiliary battery 70 is a secondary battery configured to be chargeable and dischargeable, such as a lead-acid battery or a lithium-ion battery. This auxiliary battery 70 is connected to the system main relay 50 and the MG control unit 30 via a DCDC converter 80.

[0018] The DCDC converter 80 is a power converter that can convert the input power into power of a predetermined voltage and output it. One end of this DCDC converter 80 is connected to the lithium-ion battery 40 via the system main relay 50 and to the motor generator 20 via the MG control unit 30, respectively, and the other end is connected to the auxiliary battery 70. As one of the roles of the DCDC converter 80 in the present embodiment, a function of consuming the power generated by the motor generator 20 when the system main relay 50 is in the OFF state by stepping down the power to a power of a predetermined voltage and supplying it to the auxiliary battery 70 can be exemplified.

[0019] The capacitor 90 is a charge storage element for stabilizing the MG voltage output by the MG control unit 30. This capacitor 90 is provided at the output stage of the MG control unit 30.

[0020] Note that part or all of the above-described MG control unit 30 and control microcomputer 60 can typically be configured by an electronic control unit (ECU: Electronic Control Unit) including a processor, a memory, an input / output interface, and the like. This electronic control device can realize part or all of the above-described functions by the processor reading and executing the program stored in the memory.

[0021] [Control] Next, referring further to FIGS. 2 and 3, a method for detecting ON sticking of a system main relay according to an embodiment of the present disclosure will be described. FIG. 2 is a flowchart for explaining a processing procedure of ON sticking detection control of the system main relay 50 executed by the control microcomputer 60. FIG. 3 is a timing chart for explaining a processing procedure of ON sticking detection control of the system main relay 50 executed by the control microcomputer 60.

[0022] The ON sticking detection control of the system main relay 50 illustrated in FIG. 2 is performed when the ignition switch of the vehicle is in the OFF state and the system main relay 50 is in the OFF state (open).

[0023] (Step S201) The control microcomputer 60 determines whether the ignition switch (IG) has become ON. This determination can be made by monitoring the state of an IG signal (not shown). If the ignition switch has become ON (Yes in Step S201), the process proceeds to Step S202.

[0024] (Step S202) The control microcomputer 60 makes the motor generator 20 controllable and instructs the MG control unit 30 to start MG control. Refer to time t0 in FIG. 3. This instruction can be made, for example, by turning on the starter SW. Also, the control microcomputer 60 controls the system main relay 50 to maintain the OFF state by a relay control signal. When the MG control of the MG control unit 30 is started under the control of the OFF state of the system main relay 50, the process proceeds to Step S203.

[0025] (Step S203) The control microcontroller 60 instructs the MG control unit 30 to perform voltage control using the MG target voltage. See time t1 in Figure 3. This MG target voltage is set to a voltage that is α higher than the current battery voltage of the lithium-ion battery 40, which is being monitored by the control microcontroller 60. The value α (>0) is set appropriately considering detection errors and the accuracy of MG control. Once the MG control unit 30 is instructed to perform voltage control using the MG target voltage, the process proceeds to step S204.

[0026] (Step S204) The control microcontroller 60 determines whether a predetermined time has elapsed since instructing the MG control unit 30 to perform voltage control using the MG target voltage, or in other words, since the MG control unit 30 started voltage control using the MG target voltage. This determination is made in order to accurately determine the change in battery voltage that occurs when the system main relay 50 is stuck ON. Therefore, the predetermined time is set appropriately according to the capacity of the lithium-ion battery 40 and the charging speed based on the MG target voltage. If the predetermined time has elapsed since the MG control unit 30 started voltage control using the MG target voltage (step S204, yes), the process proceeds to step S205.

[0027] (Step S205) The control microcontroller 60 determines whether or not the battery voltage of the lithium-ion battery 40 has changed. See time t2 in Figure 3. This determination is made to determine whether or not the system main relay 50 is stuck in the ON position.

[0028] Here, the system main relay 50 is controlled to remain in the OFF state by the relay control signal, so if the system main relay 50 is not stuck ON, there will be no change in the battery voltage (note that minute changes such as natural discharge are excluded here). However, if the system main relay 50 is stuck ON, an MG target voltage higher than the battery voltage is applied to the lithium-ion battery 40, causing the lithium-ion battery 40 to charge and the battery voltage to rise. Whether or not the battery voltage has changed can be determined, for example, by comparing a predetermined threshold with the increase in battery voltage over a predetermined time. This threshold is set to an arbitrary value that can accurately determine the increase in battery voltage.

[0029] If it is determined that the battery voltage of the lithium-ion battery 40 has changed (step S205, yes), the process proceeds to step S206. On the other hand, if it is determined that the battery voltage of the lithium-ion battery 40 has not changed (step S205, no), the process proceeds to step S207.

[0030] (Step S206) The control microcontroller 60 determines that the system main relay 50 is stuck in the ON position. Once it is determined that the system main relay 50 is stuck in the ON position, the process proceeds to step S208. In this case, it is possible to prompt the vehicle driver to inspect or repair the system as soon as possible through alarms or warnings using voice or displays.

[0031] (Step S207) The control microcontroller 60 determines that there is no ON lockout in the system main relay 50. Once it is determined that there is no ON lockout in the system main relay 50, the process proceeds to step S208.

[0032] (Step S208) The control microcontroller 60 controls the system main relay 50 to maintain the ON state using relay control signals. This control ensures that the lithium-ion battery 40 is electrically connected to the MG control unit 30 and the DCDC converter 80, and normal control (torque control) is performed, regardless of whether or not the system main relay 50 is stuck ON. See time t3 in Figure 3. When the system main relay 50 is controlled to the ON state, the ON-fixed detection control for the system main relay 50 ends.

[0033] <Effects and Actions> As described above, according to the ON-fixed detection method for the system main relay according to one embodiment of the present disclosure, when the vehicle's ignition switch is ON and the system main relay 50 is OFF, the MG control unit 30 is voltage-controlled to output a target voltage (battery voltage + α) higher than the battery voltage of the lithium-ion battery 40. If the battery voltage of the lithium-ion battery 40 increases as a result of the voltage control, it is determined that the system main relay 50 is stuck in the ON position. This control makes it possible to detect the ON-fixed state of the system main relay 50 with high accuracy without being affected by residual voltage, even when there is a capacitor component in the power supply circuit.

[0034] Furthermore, with the ON-fixed detection method for the system main relay according to this embodiment, it is no longer necessary to wait for the capacitor component on the power supply circuit to discharge before determining whether the system main relay 50 is ON-fixed, as in the conventional method. Therefore, problems such as misjudgment due to insufficient voltage drop (influence of residual voltage) because the discharge waiting time is too short (quick IG-OFF → IG-ON) or prolonged determination due to a long discharge waiting time are eliminated. In addition, the problem of being unable to make a determination when the capacitor component cannot be discharged due to hardware constraints is also solved.

[0035] Although one embodiment of the present disclosure has been described above, the present disclosure can be understood not only as a method for detecting the ON-fixed state of a system main relay, but also as a program for executing this method, a computer-readable non-temporary storage medium storing the program, and an electronic control device for executing the ON-fixed state detection method of the system main relay. [Industrial applicability]

[0036] This disclosure can be used when you want to detect the ON state of a system main relay that controls the power transfer state of a lithium-ion battery or the like. [Explanation of Symbols]

[0037] 10 Engines 20 Motor Generator (MG) 30 MG control unit 40 Lithium-ion batteries 50 System Main Relay (SMR) 60 Control Microcontrollers 70 Auxiliary Battery 80 DC-DC Converter (DDC) 90 Capacitors

Claims

1. A method for detecting ON-fixation of a system main relay that controls the power transfer state of a lithium-ion battery, Using a motor generator capable of charging the lithium-ion battery by voltage control, The first step involves turning the vehicle's ignition switch to the ON position and then instructing the system main relay to be in the OFF position, A second step involves voltage control of the motor generator so that it outputs a target voltage higher than the battery voltage of the lithium-ion battery, The process includes, if there is a change in the battery voltage after the second step, determining that the system main relay is stuck ON, Method for detecting ON-fixed state of the system's main relay.

2. The third step involves determining that the system main relay is stuck ON when the battery voltage changes to rise to a threshold based on the target voltage. A method for detecting ON lock of a system main relay according to claim 1.

3. The third step involves determining the change in the battery voltage after a predetermined time has elapsed since the start of voltage control of the motor generator in the second step. The method for detecting ON sticking of a system main relay according to claim 2.

Images