Electric vehicle control device

Abstract

To provide an electric vehicle control device capable of determining whether or not a system main relay is welded at an appropriate timing while suppressing a decrease in durability of the system main relay.SOLUTION: A weld check control of determining whether or not a contact of a relay is welded is executed, during the process of transitioning from a traveling mode to a pumping mode, on the basis of an execution flag for determining whether or not to execute the weld check control. When a request is made to change from the traveling mode to the pumping mode, the execution flag switches from an off state of not requesting the execution of the weld check control to an on state of requesting the execution of the weld check control, and when it is determined that the relay is not welded, the execution flag switches from the on state to the off state.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for an electric vehicle that includes a motor as a driving force source and a relay that selectively connects or disconnects an electric storage device to or from the motor, auxiliary machinery, and the like. [Background technology]

[0002] Patent Document 1 describes a control device for an electric vehicle in which a control unit, an auxiliary battery, or multiple auxiliary devices are connected via a system main relay to a high-voltage battery that functions as a battery for driving the vehicle. This control device is configured to perform pumping control to supply power from the high-voltage battery to an auxiliary load that operates when passengers get on or off the vehicle, and is configured to maintain the system main relay in a conductive state and perform pumping processing when a pumping request is made when the system main relay is in a conductive state because the traveling system is operating and the main switch is turned off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-156719 Summary of the Invention [Problem to be solved by the invention]

[0004] The control device described in Patent Document 1 can transition from a running state to pumping control while maintaining the system main relay in a conductive state, thereby reducing the number of system main relay operations and suppressing a decrease in the durability of the system main relay. However, since the system main relay typically conducts electricity by bringing contacts made of metal into contact with each other, if the system main relay remains in a conductive state for a long period of time, the contacts of the system main relay may partially weld. Therefore, if the control device described in Patent Document 1 transitions from a running state to pumping control while maintaining the system main relay in a conductive state, there are fewer opportunities to determine whether the system main relay has welded, which may delay the timing of determining whether the system main relay has welded.

[0005] The present invention has been made in light of the above-mentioned technical problems, and aims to provide a control device for an electric vehicle that can determine whether or not a system main relay has welded at an appropriate timing while suppressing a decrease in the durability of the system main relay. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a control device for an electric vehicle which includes a motor as a driving force source, a battery which supplies power to the motor, a relay which selectively cuts off the exchange of power between the motor and the battery, and an auxiliary device which is supplied with power from the battery by bringing the relay into a conductive state, and which is capable of setting a driving mode in which power is supplied from the battery to the motor by bringing the relay into a conductive state, and a pumping mode in which power is supplied from the battery to the auxiliary device, the control device including a controller which controls the relay, and the controller is configured to execute a welding check control which determines whether or not there is welding by bringing the contacts of the relay into a non-conductive state, during the process of transitioning from the driving mode to the pumping mode, based on an execution flag which determines whether or not the welding check control is to be executed, and the execution flag is switched from an off state which does not request the execution of the welding check control to an on state which requests the execution of the welding check control when a mode change from the driving mode to the pumping mode is requested, and is switched from the on state to the off state when it is determined that there is no welding in the relay. [Effects of the Invention]

[0007] According to the present invention, whether or not to execute the welding check control, which determines whether or not the relay contacts are welded by bringing the relay contacts into a non-conductive state, during the transition from the traveling mode to the pumping mode is determined based on an execution flag. Furthermore, the execution flag switches from an off state, which does not request the execution of the welding check control, to an on state, which requests the execution of the welding check control, when a mode transition from the traveling mode to the pumping mode is requested, and then switches from the on state to the off state when it is determined that the relay is not welded. Therefore, even if the traveling mode and the pumping mode, in which the relay is in a conductive state, are repeatedly switched, the welding check control can be sequentially executed and not executed when switching from the traveling mode to the pumping mode. In other words, multiple switchings from the traveling mode to the pumping mode while maintaining the relay in a conductive state can be prevented. As a result, the presence or absence of welding of the relay can be periodically determined, and a decrease in durability due to frequent relay operation can be prevented. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an example of a power supply system for an electric vehicle according to an embodiment of the present invention. [Figure 2] 4 is a flowchart illustrating an example of control executed by a control device according to an embodiment of the present invention. [Figure 3] 3 is a time chart for explaining the operating states of the SMRB, SMRG, and SMRP, whether or not welding checks are performed for the SMRB, SMRG, and SMRP, and changes in the state of the welding check execution flag when the control example shown in FIG. 2 is executed. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention and are not intended to limit the present invention.

[0010] Fig. 1 is a schematic diagram of an electric circuit for explaining an example of a power supply system for an electric vehicle according to an embodiment of the present invention. The power supply system shown in Fig. 1 is configured to supply power to a motor generator (MG) 1, which serves as a driving force source for the electric vehicle, and to charge the power generated by the motor generator 1. The power supply system includes a main battery 2, which serves as a power source for supplying and receiving power to and from the motor generator 1.

[0011] This motor generator (hereinafter referred to as motor) 1 can be configured in the same manner as motors provided as driving power sources for conventional electric vehicles, hybrid vehicles, etc., and is configured to function as a motor that outputs driving torque when power is supplied from the main battery 2, and as a generator that converts at least a portion of the power into electricity when an output shaft (not shown) is rotated to charge the main battery 2. Specifically, it is configured as an AC motor such as a permanent magnet synchronous motor or induction motor.

[0012] The main battery 2 can be configured in the same manner as batteries provided as driving power sources in conventional electric vehicles, hybrid vehicles, etc. That is, it can be configured using secondary batteries such as lithium-ion batteries, capacitors, or all-solid-state batteries. The main battery 2 may also be configured using a battery pack in which multiple secondary batteries are connected in series.

[0013] The motor 1 and main battery 2 are connected via a power control unit (hereinafter referred to as PCU) 3. This PCU 3 is made up of a converter (not shown) for changing the voltage input to the motor 1, a relatively large-capacity capacitor (not shown), an inverter (not shown) for converting DC power charged in the main battery 2 into AC power and outputting it to the motor 1, or converting AC power generated by the motor 1 into DC power and outputting it to the main battery 2, and the like.

[0014] 1 is provided with a positive electrode wire 4 connecting the positive electrode of the main battery 2 and the positive electrode of the PCU 3, and a negative electrode wire 5 connecting the negative electrode of the main battery 2 and the negative electrode of the PCU 3. The positive electrode wire 4 is provided with a positive electrode side system main relay (hereinafter referred to as SMRB) 6 that can selectively cut off the connection between the positive electrode of the main battery 2 and the positive electrode of the PCU 3, and similarly, the negative electrode wire 5 is provided with a negative electrode side system main relay (hereinafter referred to as SMRG) 7 that can selectively cut off the connection between the negative electrode of the main battery 2 and the negative electrode of the PCU 3.

[0015] On the other hand, if the SMRB 6 and the SMRG 7 are brought into a conductive state when there is a difference between the voltage of the main battery 2 and the charge voltage of the capacitor provided in the PCU 3, an overcurrent will flow through the SMRB 6 and the SMRG 7. For this reason, in the example shown in FIG. 1 , a precharge circuit is provided to charge the capacitor provided in the PCU 3. Specifically, the precharge circuit is configured by a bypass wire 8 connected between the main battery 2 side of the SMRG 7 and the PCU 3 in the negative electrode wire 5, an electrical resistance member 9 provided on the main battery 2 side of the bypass wire 8, and a precharge system main relay (hereinafter referred to as SMRP) 10 connected in series with the electrical resistance member 9 and selectively interrupting the bypass wire 8. The SMRB 6, SMRG 7, and SMRP 10 correspond to the “relay” in the embodiment of the present invention. Note that, in a configuration in which the capacitor provided in the PCU 3 can be charged by an auxiliary battery 11 (described later), the SMRP 10 may not be provided.

[0016] The SMRB6, SMRG7, and SMRP10 are configured similarly to conventional relays, and are configured so that, for example, when a solenoid (not shown) is energized, a movable member made of a magnetic material moves by electromagnetic force, closing (bringing into conduction) contacts made of a metallic material. That is, when the SMRB6 and the SMRG7 or SMRP10 are brought into conduction, the main battery 2 and the PCU 3 are brought into conduction, and therefore, by controlling the PCU 3, a desired amount of power can be supplied to the motor 1.

[0017] 1 includes an auxiliary battery 11 and various auxiliaries 12 and 13, and is configured so that the auxiliary battery 11 is charged by supplying power from the main battery 2, and the auxiliaries 12 and 13 are operated by supplying power from the main battery 2 to the auxiliaries 12 and 13. The auxiliaries 12 and 13 include electronic exterior mirrors and a vehicle exit assistance system that operate in conjunction with standard operating patterns such as when the vehicle doors are opened or closed or when the ignition switch is turned on or off.

[0018] Specifically, the positive electrode wire 4 branches off from between the SMRB 6 and the PCU 3, and similarly, the negative electrode wire 5 branches off from between the SMRG 6 or the SMRP 10 and the PCU 3. A DC-DC converter 14 that changes and outputs the output voltage of the main battery 2 is connected to the branched positive electrode wire 4 and negative electrode wire 5. The DC-DC converter 14 is then connected to the auxiliary battery 11, the auxiliary devices 12 and 13, and the like.

[0019] Also provided is an electronic control device (hereinafter referred to as the controller) 15 for controlling the above-mentioned SMRB6, SMRG7, and SMRP10. Like controllers provided in conventional vehicles, this controller 15 can be configured mainly with a microcomputer, and is configured to receive signals from various sensors provided in the vehicle (power supply system), determine the conductive or non-conductive state of SMRB6, SMRG7, and SMRP10 based on the received signals and pre-stored maps, arithmetic expressions, etc., and output signals corresponding to the determined conductive or non-conductive state to SMRB6, SMRG7, and SMRP10.

[0020] The power supply system configured as described above can be set to a driving mode in which power is exchanged between the motor 1 and the main battery 2, and a pumping mode in which power is supplied from the main battery 2 to the auxiliary battery 11 and the auxiliary devices 12 and 13.

[0021] The pumping mode is a mode that is set when the main switch of the vehicle is off and the vehicle is unable to travel, and is set, for example, when the charging power of the auxiliary battery 11 is equal to or less than a predetermined power and there is a request to charge the auxiliary battery 11 using the main battery 2, or when the power required for the accessories 12, 13 cannot be met by the auxiliary battery 11 and there is a request to supply power from the main battery 2 to the accessories 12, 13. In other words, the pumping mode is mainly set when getting on or off the vehicle.

[0022] Therefore, the above-mentioned running mode and pumping mode connect the SMRB6 and the SMRG7 or SMRP10. However, since the SMRB6, SMRG7, and SMRP10 are configured to be in a conductive state by closing contacts formed of a metallic material as described above, there is a possibility that the contacts will weld based on the time that the conductive state is maintained and the value of the current passed through the SMRB6, SMRG7, and SMRP10. In particular, since the power passed through the SMRB6, SMRG7, and SMRP10 tends to be high in the running mode, there is a possibility that the contacts will weld during the running mode.

[0023] Therefore, the control device for an electric vehicle in an embodiment of the present invention is configured to check whether the SMRB6, SMRG7, and SMRP10 are welded during the process of transitioning from the travel mode to the pumping mode. FIG. 2 shows a flowchart for explaining an example of this control. The control example shown in FIG. 2 is configured to check whether the SMRB6, SMRG7, and SMRP10 are welded as one form of processing to end the travel mode, and therefore the control example shown in FIG. 2 is executed when it is determined that the travel mode has been completed. The travel mode is completed, for example, when the position of the shift device is switched to the parking position or when the main switch of the vehicle is turned off (IG-OFF).

[0024] 2 is executed, the controller 10 determines whether there is a mode change request to the pumping mode (step S1). Specifically, the controller 10 determines that there is a mode change request to the pumping mode when, for example, the remaining charge of the auxiliary battery 11 drops below a predetermined level and there is a request to supply power from the main battery 2 to the auxiliary battery 11 to charge the auxiliary battery 11, or when the power stored in the auxiliary battery 11 is insufficient to drive the auxiliary devices 12 and 13, such as the electronic exterior mirrors that operate when the driver gets off the vehicle and the vehicle dismount assistance system, and there is a request to supply power from the main battery 2 to the auxiliary devices 12 and 13.

[0025] If the answer to step S1 is negative because there is no request to switch to the pumping mode, the routine executes a process to terminate the running mode, such as switching off SMRB6, SMRG7, and SMRP10, and then ends this routine.

[0026] On the other hand, if the answer to step S1 is YES because there is a mode change request to the pumping mode, it is determined whether the welding check execution flag is on (step S2). This welding check execution flag is configured to switch from an off state, which does not request the execution of welding check control to determine the presence or absence of welding, to an on state, which requests the execution of welding check control, when there is a mode change request from the travel mode to the pumping mode, and is also configured to switch from the on state to the off state when it is determined that none of SMRB6, SMRG7, and SMRP10 are welded.

[0027] If the welding check execution flag is on and the result of the determination in step S2 is affirmative, welding check control is executed to determine whether welding exists (step S3). This welding check control outputs a signal to a relay that is in a conductive state to switch it off (to a non-conductive state), and determines whether the value of the current flowing through the positive electrode wire 4 and the negative electrode wire 5 at that time has become "0". Note that a relay that is in a non-conductive state may be determined to be free of welding, or may be switched to a conductive state once and then switched back to a non-conductive state, and it may be determined whether the value of the current flowing through the positive electrode wire 4 and the negative electrode wire 5 at that time has become "0".

[0028] To explain this in detail using an example, when the driving mode is first set after the main switch is turned on, the capacitor provided in the PCU 3 is usually not charged. Therefore, to prevent an overcurrent from flowing through the relay, the SMRB6 and SMRP10 are brought into a conductive state to charge the capacitor. If a mode change request from the driving mode to the pumping mode is made at that time and the welding check implementation flag is on, the SMRB6 and SMRP10 are switched into a non-conductive state and then restored to a conductive state. Note that it is preferable to determine whether or not each relay is welded by sequentially switching between the conductive and non-conductive states, such as by switching the SMRB6 into a non-conductive state and maintaining the SMRP10 in a conductive state to determine whether or not the SMRB6 is welded, and then switching the SMRB6 into a conductive state and the SMRP10 into a non-conductive state to determine whether or not the SMRP10 is welded.

[0029] Furthermore, as described above, during the traveling mode, the capacitor is charged when a predetermined time has elapsed since the SMRB6 and SMRP10 were brought into a conductive state. Therefore, if the traveling mode continues for a predetermined time or longer, the SMRP10 is switched to a non-conductive state and the SMRG7 is switched to a conductive state. If a mode change request from the traveling mode to the pumping mode is made while the SMRB6 and SMRG7 are in a conductive state and the welding check execution flag is on, the SMRB6 and SMRG7 are switched to a non-conductive state and then restored to a conductive state. It is preferable to determine whether or not each relay is welded by sequentially switching between the conductive and non-conductive states, such as by switching the SMRB6 to a non-conductive state and maintaining the SMRG7 in a conductive state to determine whether or not the SMRB6 is welded, and then switching the SMRB6 to a conductive state and the SMRG7 to a non-conductive state to determine whether or not the SMRG7 is welded.

[0030] Next, it is determined whether all the relays are welded (step S4). That is, it is determined whether the value of the current flowing through the positive electrode wire 4 or the negative electrode wire 5 does not become "0" despite the output of a signal to turn off any of the relays. This step S4 can be determined, for example, by providing a flag for each relay that indicates the result of the determination of whether or not there is welding. Note that, when the welding check execution flag is switched on, simultaneously, a flag provided for each relay is switched off, indicating that the welding check has not been performed, and a flag corresponding to a relay for which the welding check has been completed because the welding check execution flag is on is switched on, indicating that the welding check has been performed.

[0031] If the determination in step S4 is affirmative because none of the relays are welded, the welding check execution flag is switched off, the system transitions to the pumping mode (step S5), and this routine ends temporarily. Conversely, if the determination in step S4 is negative because any of the relays is welded, a warning is issued to the occupant (step S6), and this routine ends temporarily.

[0032] On the other hand, if the welding check execution flag is off and the result of the determination in step S2 is negative, in order to suppress a decrease in the durability of the relay due to switching of the relay between a conductive state and a non-conductive state, or to shorten the transition time to the pumping mode due to the switching, the relay that is in a conductive state is maintained in the conductive state, the mode is transitioned to the pumping mode, the welding check execution flag is switched on (step S7), and this routine is temporarily terminated.

[0033] 3 shows a time chart for explaining the operating states of SMRB6, SMRG7, and SMRP10, whether or not welding checks are performed for SMRB6, SMRG7, and SMRP10, and changes in the state of the welding check execution flag when the above control example is executed. Note that the vehicle mode is shown with one trip defined as the period from the start of the driving mode.

[0034] 3, at time t0, the driving mode is set, so that SMRB6 and SMRG7 are connected (ON), and SMRP10 is disconnected (OFF). Also, the welding check execution flag is set to ON.

[0035] In this state, when the traveling mode is completed and a mode change request to the pumping mode is made (time t1), the presence or absence of welding of each relay 6, 7, 10 is checked during the traveling mode termination process shown in hatched in Figure 3. In the example shown in Figure 3, SMRB6 is temporarily switched to a non-conductive state and then switched back to a conductive state to determine that it is not welded, and then SMRG is temporarily switched to a non-conductive state and then switched back to a conductive state to determine that it is not welded. Furthermore, in the example shown here, SMRP10 is temporarily switched to a conductive state and then switched back to a non-conductive state to determine that it is not welded.

[0036] Then, when it is determined that all of the relays 6, 7, and 10 are not welded (at time t2), that is, when the flags indicating the welding check implementation status corresponding to all of the relays 6, 7, and 10 are turned on (performed), the welding check implementation flag is switched off.

[0037] On the other hand, at time t3, although the driving mode is set, when the driving mode is switched to the pumping mode, it is determined that the relays 6, 7, and 10 are not welded, and the welding check execution flag is switched off. Therefore, since the determination in step S2 is negative, at time t3, it is not determined whether the relays 6, 7, and 10 are welded. In other words, SMRB6 and SMRG7, which are in a conductive state, remain in a conductive state, and the vehicle mode transitions to the pumping mode (time t4). At time t4, the welding check execution flag is switched on.

[0038] Therefore, if there is a mode change request from the driving mode to the pumping mode in the subsequent trip (time t5), similarly to time t1, the presence or absence of welding of each of the relays 6, 7, 10 is determined, and the vehicle mode transitions to the pumping mode (time t6).

[0039] As described above, the welding check control is performed based on the welding check execution flag, which is configured to switch from OFF to ON when a mode change request from the traveling mode to the pumping mode is made and to switch OFF when it is determined that none of the SMRB 6, SMRG 7, and SMRP 10 are welded. This allows the welding check control to be alternately performed and not performed when switching from the traveling mode to the pumping mode, even when the traveling mode in which the SMRB 6 and the SMRG 7 or SMRP 10 are connected are repeatedly switched to the pumping mode. In other words, it is possible to prevent multiple switchings from the traveling mode to the pumping mode while maintaining the connection between the SMRB 6 and the SMRG 7 or SMRP 10. As a result, it is possible to periodically determine whether each relay 6, 7, and 10 is welded, and it is possible to prevent a decrease in durability due to frequent operation of each relay 6, 7, and 10.

[0040] The electrically powered vehicle in the embodiment of the present invention may be an electric vehicle equipped with only a motor as a driving force source, or may be a hybrid vehicle equipped with a motor and an engine as driving force sources. [Explanation of symbols]

[0041] 1 motor 2 Main battery 4 Positive wire 5 Negative wire 6, 7, 10 relay 11 Auxiliary battery 12,13 Auxiliary equipment 15 Controller

Claims

[Claim 1] A control device for an electric vehicle includes a motor as a driving force source, a battery that supplies power to the motor, a relay that selectively cuts off the exchange of power between the motor and the battery, and an accessory that is supplied with power from the battery by bringing the relay into a conductive state, and is capable of setting a driving mode in which power is supplied from the battery to the motor and the accessory by bringing the relay into a conductive state, and a pumping mode in which power is supplied from the battery to the accessory, a controller for controlling the relay; The controller a welding check control for determining whether or not welding has occurred by bringing the contacts of the relay into a non-conductive state is executed based on an execution flag for determining whether or not the welding check control is executed during a process of transitioning from the traveling mode to the pumping mode; The execution flag is switched from an off state, which does not request execution of the welding check control, to an on state, which requests execution of the welding check control, when a mode change from the traveling mode to the pumping mode is requested, and is switched from the on state to the off state when it is determined that the relay is not welded. A control device for an electric vehicle.

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