Control device for hybrid vehicle

Abstract

To enable determination of deposition of an SMR-B which is one of contacts of an SMR even when an MG failure occurs.SOLUTION: A control device for a hybrid vehicle transmits power from a chargeable battery through an SMR to a power control unit for controlling an MG. The control unit can perform a process for detecting a failure of the MG during traveling of the vehicle to cut off the SMR, and driving a DCDC converter capable of reducing and transmitting an output voltage of the battery to a prescribed auxiliary machine after the traveling stop of the vehicle, thereby discharging a capacitor included in a power control unit, and a process for acquiring a voltage of the capacitor in a state where an SMR-R is conductive, determining that there is no deposition of an SMR-B if the voltage is lower than a prescribed value, and determining that there is deposition of the SMR-B if the voltage is higher than the prescribed value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to the control of a hybrid vehicle. [Background technology]

[0002] Patent Document 1 discloses a technology related to a hybrid vehicle in which power is transmitted from a rechargeable battery via a system main relay (hereinafter referred to as SMR) to a power control unit that controls a motor generator (hereinafter referred to as MG). In a hybrid vehicle, if the MG fails while the vehicle is running, the SMR is shut off and the vehicle then runs evacuated and stops. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-160626 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, the welding determination to determine whether SMR-B (positive side relay), one of the contacts of the SMR, is welded, has been performed by shutting off the SMR after the vehicle has stopped running, discharging the capacitor included in the power control unit using MG, and setting the voltage of the capacitor to 0 V. In this case, SMR-P (pre-charge relay), one of the contacts of the SMR, is made conductive, and if the voltage does not rise above a predetermined level, it is determined that SMR-B is not welded.

[0005] However, as described above, if the SMR is shut off due to a malfunction of the MG while the vehicle is running and the vehicle is stopped as an evacuation measure, a charge remains in the capacitor and the MG also malfunctions, making it impossible to perform a welding determination after that.This specification presents a technology that makes it possible to perform a welding determination in such a situation where a welding determination was not possible in the past. [Means for solving the problem]

[0006] This specification discloses a control device for a hybrid vehicle that transmits power from a rechargeable battery via an SMR to a power control unit that controls a motor drive. The control device includes a control unit and a DC-DC converter that can step down the battery's output voltage and transmit the power to a predetermined auxiliary device. The SMR has a first contact connected to the positive terminal of the battery, a second contact connected to the negative terminal of the battery, a third contact connected in parallel with the second contact to the negative terminal of the battery, and a limiting resistor connected in series with the third contact and in parallel with the second contact to the negative terminal of the battery. The control unit is capable of detecting a failure of the motor drive while the vehicle is traveling and shutting off the SMR. After the vehicle stops traveling, the control unit drives the DC-DC converter to discharge a capacitor included in the power control unit. The control unit also obtains the voltage of the capacitor while the third contact is conductive, and determines that the first contact is not welded if the voltage is below a predetermined value, and determines that the first contact is welded if the voltage is above the predetermined value.

[0007] According to the above configuration, the control unit detects a failure of the MG while the vehicle is running and shuts off the SMR, and after the vehicle stops running, drives the DC-DC converter to discharge the capacitor, thereby enabling the control unit to determine whether the first contact has welded. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a partial configuration of a vehicle including a control device. [Figure 2] 4 is a flowchart showing processing executed in the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present embodiment will be described with reference to the drawings. Each drawing is merely an example, and the present embodiment is not limited to the contents shown in the drawings. Furthermore, since each drawing is an example, the shapes shown in the drawings may not necessarily be accurate, and some parts may be omitted.

[0010] 1 shows a partial configuration of a vehicle 1 including a control device 10 according to this embodiment. The vehicle 1 is a hybrid vehicle equipped with a battery, such as a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV).

[0011] The vehicle 1 includes a battery 11, an SMR (System Main Relay) 12, a DC-DC converter 13, a power control unit 14, an MG 15, a control unit 16, etc. The power control unit 14 is also called a PCU (Power Control Unit). The control unit 16 may be understood as one or more ECUs (Electronic Control Units) having a processor or the like. The control unit 16 is capable of controlling the SMR 12, the DC-DC converter 13, the power control unit 14, the MG 15, etc.

[0012] The battery 11 is a high-voltage battery that can be charged and discharged. For example, a lithium-ion battery pack, a nickel-metal hydride battery pack, a nickel-cadmium battery, a lead-acid battery, etc. can be used as the battery 11. In FIG. 1, a configuration including the SMR 12, the DC-DC converter 13, the control unit 16, etc. is considered to be an example of the control device 10.

[0013] The SMR 12 is composed of an SMR-B 12a as a first contact, an SMR-G 12b as a second contact, an SMR-P 12c as a third contact, a limiting resistor R1, etc. The SMR-B 12a is connected to the positive electrode side of the battery 11 and transmits power from the battery 11 to the power control unit 14. The SMR-G 12b is connected to the negative electrode side of the battery 11 and transmits power from the power control unit 14 to the battery 11.

[0014] The SMR-P12c and limiting resistor R1 are connected in parallel with the SMR-G12b to the negative electrode of the battery 11, and transmit power from the power control unit 14 to the battery 11. The SMR-P12c and limiting resistor R1 are connected in series. The limiting resistor R1 is used to suppress the flow of inrush current when the battery 11 is connected to the power control unit 14. Each of the SMR-B12a, SMR-G12b, and SMR-P12c switches between an ON state and an OFF state upon receiving a control signal from the control unit 16.

[0015] The DC-DC converter 13 can step down the output voltage of the battery 11 and transmit the power to a predetermined auxiliary device 20. In FIG. 1, the auxiliary device 20 is assumed to be a lead-acid battery. To the auxiliary device 20, for example, a starter motor 21 and an alternator 22 are connected. The starter motor 21 is a motor for starting the engine 23, and receives power from the auxiliary device 20. The alternator 22 is a generator that generates power using power generated by the engine 23 and charges the auxiliary device 20. The auxiliary device 20 may also include various other loads in the vehicle 1 that consume power for purposes other than driving.

[0016] The power control unit 14 is composed of a smoothing capacitor C1, a boost circuit 17, a smoothing capacitor C2, an inverter 18, etc. The smoothing capacitor C1 is provided as a capacitor that smoothes the voltage between the battery 11 and the boost circuit 17. The voltage of the smoothing capacitor C1 is represented as voltage VL. The boost circuit 17 can boost the output voltage of the battery 11 and output the boosted power to the inverter 18, or can lower the output voltage of the inverter 18 and output the lowered power to the battery 11.

[0017] Smoothing capacitor C2 is provided as a capacitor that smoothes the voltage between boost circuit 17 and inverter 18. The voltage of smoothing capacitor C2 is denoted as voltage VH. Inverter 18 converts DC power from battery 11 into AC power and supplies it to MG 15. Inverter 18 is configured by an inverter circuit equipped with multiple switching elements so that current for each phase (U phase, V phase, W phase) can be applied to each of the three-phase coils of MG 15.

[0018] The MG 15 and the engine 23 are connected to a drive shaft 24, and driving force for traveling is transmitted to the drive shaft 24. The vehicle 1 travels using driving force from at least one of the engine 23 and the MG 15. Furthermore, the MG 15 generates electricity using the rotational force received from the drive shaft 24 when braking the vehicle 1, etc. The power generated by the MG 15 is converted into DC power by the inverter 18 and charged into the battery 11. The control unit 16 can acquire the latest voltages VL and VH detected at any time by each voltage sensor (not shown).

[0019] 2 is a flowchart showing the processing executed by the vehicle 1 in this embodiment. The flowchart includes a welding determination process for determining whether the SMR-B 12a is welded. The flowchart is executed when the vehicle 1 is stopped.

[0020] First, when an occupant of the vehicle 1 presses the ignition switch of the vehicle 1, a predetermined IG signal is transmitted, the vehicle 1 enters an IG ON state, and the control unit 16 recognizes the IG ON state (step S100). Furthermore, the starter motor 21 starts, and the control unit 16 recognizes the ST ON state (step S110).

[0021] In step S120, control unit 16 acquires voltage VH and determines whether voltage VH is less than a predetermined value. Step S120 is a process for determining whether a predetermined capacitor included in power control unit 14 is being discharged, and in this case, the value of voltage VH of smoothing capacitor C2 is evaluated. If voltage VH is less than the predetermined value, control unit 16 determines "Yes" in step S120 and proceeds to step S140. On the other hand, if voltage VH exceeds the predetermined value, control unit 16 determines "No" in step S120 and proceeds to step S130.

[0022] In step S130, the control unit 16 drives the DC-DC converter 13 to discharge the smoothing capacitor C2. The control unit 16 performs the discharge by driving the switching element of the DC-DC converter 13. After step S130, the control unit 16 performs the determination of step S120 again.

[0023] In step S140, the control unit 16 determines whether or not evacuation driving was performed during the previous (most recent) driving of the vehicle 1. Evacuation driving refers to detecting a malfunction of the MG 15 while the vehicle 1 is driving, immediately shutting off the SMR 12 in response to the detection of the malfunction, and then safely stopping the driving of the vehicle 1. Evacuation driving may be considered as a driving mode different from normal driving. In this embodiment, there is no particular restriction on the method for detecting a malfunction of the MG 15. There is also no particular restriction on the type of malfunction of the MG 15. Shutting down the SMR 12 refers to switching each of the SMR-B 12a, SMR-G 12b, and SMR-P 12c to the off state.

[0024] When the vehicle 1 performs evacuation running, information indicating that evacuation running has been performed is recorded in, for example, a memory included in the control unit 16. Therefore, the control unit 16 can check whether or not evacuation running was performed during the previous run by referring to the memory. If evacuation running was performed during the previous run, the control unit 16 proceeds to step S150 from the determination of "Yes" in step S140, whereas if evacuation running was not performed during the previous run, the control unit 16 proceeds to step S170 from the determination of "No" in step S140.

[0025] Thus, the determination of "Yes" in each of steps S120 and S140 is a prerequisite for proceeding to step S150. In step S150, the control unit 16 turns on the SMR-P 12c to make it conductive. Subsequently, in step S160, the control unit 16 acquires the voltage VH and determines whether the voltage VH is less than a predetermined value. The predetermined value used for the determination in step S160 may be the same as the predetermined value used for the determination in step S120. If the voltage VH is less than the predetermined value, the control unit 16 determines "Yes" in step S160 and proceeds to step S170. On the other hand, if the voltage VH exceeds the predetermined value, the control unit 16 determines "No" in step S160 and proceeds to step S220. In each of steps S120 and S160, the control unit 16 may, for example, determine "Yes" if the voltage VH is 0 V, or "No" if the voltage VH exceeds 0 V.

[0026] In step S220, the control unit 16 determines that the SMR-B 12a is welded, and ends the flowchart of Fig. 2. When the control unit 16 ends the flowchart in step S220, it determines that the vehicle 1 cannot start traveling. In this case, the control unit 16 may, for example, issue a warning to the occupant that the vehicle 1 cannot travel.

[0027] If the process proceeds from "Yes" in step S160 to step S170, the control unit 16 determines that the SMR-B 12a is not welded. Also, if the process proceeds from "Yes" in step S160 to step S170, the control unit 16 switches the SMR-P 12c to the off state.

[0028] Steps S170 to S210 are a normal SMR connection sequence executed when starting up MG 15. In step S170, control unit 16 turns on SMR-B 12a. Subsequently, in step S180, control unit 16 turns on SMR-P 12c. This allows smoothing capacitor C1 to be precharged using power output from auxiliary device 20.

[0029] Next, the control unit 16 turns on the SMR-G 12b in step S190 and turns off the SMR-P 12c in step S200. This connects the battery 11 to the power control unit 14, starts the MG 15, and puts the vehicle 1 in a Ready ON state where it can travel (step S210). When the flowchart of FIG. 2 is completed in step S210, the vehicle 1 starts traveling.

[0030] Regarding the flowchart of Figure 2, it may be considered that steps S120 to S160 and S220 are executed, for example, when vehicle 1 stops after completing the above-mentioned evacuation driving, rather than when the stopped vehicle 1 is started as described above. Power control unit 14 may be configured without boost circuit 17. If boost circuit 17 is not included, power control unit 14 may have only one of smoothing capacitors C1 and C2. This one capacitor included in power control unit 14 is then subject to discharge in step S130, and is subject to determination in steps S120 and S160 as to whether or not the voltage is less than a predetermined value.

[0031] As described above, this embodiment discloses a control device 10 for a hybrid vehicle 1 that transmits power from a rechargeable battery 11 via an SMR 12 to an electric power control unit 14 that controls an MG 15. The control device 10 includes a control unit 16 and a DC-DC converter 13 that can step down the output voltage of the battery 11 and transmit the power to a predetermined auxiliary device 20. The SMR 12 has a first contact (SMR-B 12a) connected to the positive electrode side of the battery 11, a second contact (SMR-G 12b) connected to the negative electrode side of the battery 11, a third contact (SMR-P 12c) connected in parallel with the second contact on the negative electrode side of the battery 11, and a limiting resistor R1 connected in series with the third contact and in parallel with the second contact on the negative electrode side of the battery 11. The control unit 16 detects a failure of the MG 15 while the vehicle 1 is running and cuts off the SMR 12, and after the vehicle 1 has stopped running, it drives the DCDC converter 13 to discharge the capacitor of the power control unit 14, and acquires the voltage of the capacitor while the third contact is conductive, and if the voltage is less than a predetermined value, determines that the first contact is not welded, and if the voltage exceeds the predetermined value, determines that the first contact is welded.

[0032] According to the above configuration, the control unit 16 detects a failure of the MG 15 while the vehicle 1 is traveling and cuts off the SMR 12. After the vehicle 1 has evacuated and stopped, the control unit 16 drives the DC-DC converter 13 to discharge the capacitor. This enables the control unit 16 to determine whether the first contact has welded. That is, even if a conventional system falls into a situation where it would be impossible to determine whether the first contact has welded, the present embodiment makes it possible to perform the determination.

[0033] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of those objectives itself has technical utility. [Explanation of symbols]

[0034] 1: vehicle, 10: control device, 11: battery, 12: SMR, 12a: SMR-B, 12b: SMR-G, 12c: SMR-P, 13: DC-DC converter, 14: power control unit, 15: MG, 16: control unit, 17: boost circuit, 18: inverter, 20: auxiliary equipment, 21: starter motor, 22: alternator, 23: engine, C1, C2: smoothing capacitor, R1: limiting resistor

Claims

[Claim 1] A control device for a hybrid vehicle that transmits power from a rechargeable battery to a power control unit that controls a motor generator via a system main relay, A control unit; a DC-DC converter capable of stepping down the output voltage of the battery and transmitting the power to a predetermined auxiliary device, the system main relay has a first contact connected to the positive electrode side of the battery, a second contact connected to the negative electrode side of the battery, a third contact connected in parallel with the second contact on the negative electrode side of the battery, and a limiting resistor connected in series with the third contact and in parallel with the second contact on the negative electrode side of the battery, The control unit a fault in the motor generator is detected while the vehicle is running, and the system main relay is shut off, and after the vehicle stops running, A process of discharging a capacitor included in the power control unit by driving the DC-DC converter; The control device is capable of executing a process of acquiring the voltage of the capacitor with the third contact being conductive, determining that the first contact is not welded if the voltage is less than a predetermined value, and determining that the first contact is welded if the voltage exceeds the predetermined value.

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