Power supply system for vehicle

Abstract

To provide a power supply system for a vehicle which can calculate a scale of electric power of a DCDC converter for consumption power of an auxiliary machinery without a current sensor monitoring the DCDC converter at the time of engine stop of an intermittent operation.SOLUTION: A power supply system for a vehicle comprises: an auxiliary apparatus 11 including an auxiliary load 12, auxiliary battery 13 supplying the auxiliary load with electric power; and an alternator 15 which supplies the auxiliary apparatus 11 with electric power generated by rotation of an engine 14; and a DCDC converter 17 connected in parallel with the alternator 15 which converts voltage of the electric power of a drive battery 16 to be supplied to the auxiliary apparatus 11. While the engine 14 is stopped during an intermittent operation of the engine 14, a case that the electric power of the DCDC converter 17 is smaller than consumption power of the auxiliary load 12 is determined based on the difference between the voltage value of the electric power of the DCDC converter 17 and voltage value of the auxiliary battery 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle power supply system. [Background technology]

[0002] A vehicle power supply system installed in a hybrid electric vehicle (HEV) or plug-in hybrid electric vehicle (PHEV) has a DC-DC converter that converts the voltage of the electric power of a drive battery and supplies it to auxiliary equipment, and an alternator that supplies electric power generated by the rotation of the engine to the auxiliary equipment. The auxiliary equipment includes an auxiliary load and an auxiliary battery.

[0003] In the HEV or PHEV, the engine is operated intermittently while the vehicle is running in order to improve fuel efficiency and reduce exhaust gas. In the vehicle power supply system, when the engine is stopped during intermittent engine operation and the supply power of the DC-DC converter 17 is smaller than the power consumption of the auxiliary equipment, the engine is started and the power generated by the alternator is supplied to the auxiliary equipment.

[0004] For example, in the vehicle power supply system described in Patent Document 1, in order to determine when the power supplied by the DCDC converter 17 is smaller than the power consumption of the auxiliary equipment, the power supplied by the DCDC converter is detected using a current sensor that monitors the DCDC converter. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-195237 A Summary of the Invention [Problem to be solved by the invention]

[0006] Here, if it is possible to determine when the power supplied by the DCDC converter is smaller than the power consumed by the auxiliary equipment without using a current sensor to monitor the DCDC converter, costs can be reduced by not having to install a current sensor to monitor the DCDC converter.

[0007] Therefore, an object of the present invention is to provide a vehicle power supply system that can determine when the power supplied by the DCDC converter is smaller than the power consumed by the auxiliary equipment while the engine is stopped during intermittent operation of the engine, without using a current sensor that monitors the DCDC converter. [Means for solving the problem]

[0008] The vehicle power supply system of the present invention comprises an auxiliary device including an auxiliary load and an auxiliary battery that supplies power to the auxiliary load, an alternator that supplies power generated by the rotation of the engine to the auxiliary device, and a DCDC converter connected in parallel to the alternator that converts the voltage of the power of the drive battery and supplies it to the auxiliary device, and is characterized in that, while the engine is stopped during intermittent operation of the engine, the system determines a case where the supply power of the DCDC converter is smaller than the power consumed by the auxiliary device based on the difference between the voltage value of the power supplied by the DCDC converter and the voltage value of the auxiliary battery. Effect of the Invention

[0009] According to the vehicle power supply system of the present invention, it is possible to determine when the power supplied by the DCDC converter is smaller than the power consumed by the auxiliary equipment while the engine is stopped during intermittent operation of the engine, without using a current sensor that monitors the DCDC converter. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a vehicle power supply system according to an embodiment; [Diagram 2] 1 is a block diagram showing a configuration of an ECU according to an embodiment; [Diagram 3]FIG. 2 is a flow chart showing a flow of an intermittent engine operation control according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An example of an embodiment of the present invention will be described in detail below. In the following description, specific shapes, materials, directions, values, etc. are merely examples for the purpose of easily understanding the present invention, and can be appropriately changed according to the application, purpose, specifications, etc.

[0012] [Vehicle power supply system] A vehicle power supply system 10 will be described with reference to FIG.

[0013] The vehicle power supply system 10 is mounted on a vehicle. The vehicle is an HEV that runs by driving an engine 14 and a motor (not shown). The vehicle may be a PHEV that runs by driving an engine 14 and a motor and can charge the drive battery 16 using a plug from an electrical outlet.

[0014] According to the vehicle power supply system 10, as will be described in detail later, during an intermittent stop of the engine 14, it is possible to determine when the supply power of the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12 without using a current sensor that monitors the DCDC converter 17.

[0015] The vehicle power supply system 10 includes an auxiliary load 12, an auxiliary device 11 including an auxiliary device battery 13, an alternator 15 that supplies power generated by the rotation of an engine 14 to the auxiliary device 11, a DC-DC converter 17 connected in parallel to the alternator 15 and converts the voltage of the power of a drive battery 16 and supplies it to the auxiliary device 11, and an ECU (Electronic Control Unit) 20 that performs engine intermittent operation control, which will be described in detail later.

[0016] The auxiliary load 12 is a device that consumes power, such as an electrical component in the vehicle, a control device that controls the electrical component, a control device related to driving, a control device that controls automatic driving, etc., such as a brake motor, a power steering motor, etc.

[0017] The auxiliary battery 13 supplies power to the auxiliary load 12, and is a battery with a lower voltage and smaller capacity than the drive battery 16 described below. A lead battery, a lithium ion battery, or the like is preferably used as the auxiliary battery 13. The auxiliary battery 13 is provided with a battery voltage sensor 18 that detects the voltage value of the auxiliary battery 13.

[0018] The alternator 15 is a generator that generates electricity by the rotation of the engine 14, and supplies electric power to the auxiliary device 11. The alternator 15 may be connected to a crankshaft of the engine 14 by a belt. The alternator 15 is connected in parallel with the DC-DC converter 17 with respect to the auxiliary device 11.

[0019] The drive battery 16 supplies power to a motor that drives the vehicle. As the drive battery 16, a lithium ion battery or the like is preferably used.

[0020] The DCDC converter 17 steps down the voltage of the high-voltage DC power of the drive battery 16 to a low-voltage DC power voltage and supplies it to the auxiliary device 11. The DCDC converter 17 is connected to the auxiliary device 11 in parallel with the alternator 15.

[0021] In the vehicle power supply system 10, the voltage of the power of the drive battery 16 is normally converted by the DCDC converter 17 and supplied to the auxiliary equipment 11. When the power supplied by the DCDC converter 17 is smaller than the power consumption of the auxiliary equipment load 12, the engine 14 is driven to supply the power generated by the alternator 15 to the auxiliary equipment 11.

[0022] [ECU] The ECU 20 will be described with reference to FIG.

[0023] During the stop of the engine 14 in the intermittent operation of the engine 14, the ECU 20 determines whether the supply power of the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12 based on the difference between the voltage command value of the DCDC converter 17 and the voltage value of the auxiliary battery 13. This makes it possible to determine whether the supply power of the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12 without using a current sensor that monitors the DCDC converter 17.

[0024] The ECU 20 may be composed of a plurality of ECUs that control the devices of the vehicle. The ECU 20 has a central processing unit (CPU) that is an arithmetic processing unit, and storage units such as a random access memory (RAM) and a read only memory (ROM), and performs signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM.

[0025] The ECU 20 is connected to the engine 14, the alternator 15, and the DCDC converter 17. The ECU 20 can instruct the engine 14 to start or stop. The ECU 20 can also instruct the alternator 15 to suppress power generation. Furthermore, the ECU 20 can instruct the DCDC converter 17 to a voltage value after conversion.

[0026] A battery voltage sensor 18 is connected to the ECU 20. The ECU 20 acquires the voltage value of the auxiliary battery 13 detected by the battery voltage sensor 18.

[0027] The ECU 20 has an intermittent engine operation unit 21, a supply power determination unit 22, an engine start-up unit 23, and an engine stop unit 24, each of which will be described in detail below. The intermittent engine operation unit 21, the supply power determination unit 22, the engine start-up unit 23, and the engine stop unit 24 are realized by the CPU executing programs stored in the ROM or RAM.

[0028] The intermittent engine operation unit 21 repeatedly operates and stops the engine 14 at predetermined time intervals while the vehicle is traveling. The intermittent engine operation unit 21 can improve the fuel efficiency performance of the vehicle and reduce exhaust gas.

[0029] The supply power determination unit 22 determines, while the engine 14 is stopped during intermittent operation of the engine 14 by the engine intermittent operation unit 21, whether the supply power of the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12 based on the difference between the supply voltage value of the DCDC converter 17 and the voltage value of the auxiliary battery 13.

[0030] Here, if the power supplied by the DCDC converter 17 is smaller than the power consumed by the auxiliary load 12, i.e., if the power consumed by the auxiliary load 12 cannot be covered by the power supplied by the DCDC converter 17 alone, power is supplied from the auxiliary battery 13 to the auxiliary load 12, causing the auxiliary battery 13 to enter a discharged state, and the voltage value of the auxiliary battery 13 becomes smaller than the voltage value instructed to the DCDC converter 17.

[0031] Therefore, when the engine 14 is stopped during intermittent operation of the engine 14, if the voltage value of the auxiliary battery 13 is smaller than the voltage value instructed to the DCDC converter 17 and the difference between the voltage value instructed to the DCDC converter 17 and the voltage value of the auxiliary battery 13 remains equal to or greater than a predetermined voltage value for a predetermined period of time, the supply power determination unit 22 determines that the power supplied by the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12.

[0032] In addition, the supply power determination unit 22 can determine the case where the supply power of the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12, without picking up the transient fluctuation of the voltage value of the auxiliary battery 13, by continuously monitoring the difference between the voltage command value of the DCDC converter 17 and the voltage value of the auxiliary battery 13 for a predetermined time. Examples of the transient fluctuation of the voltage value of the auxiliary battery 13 include the power consumption of the brake motor during sudden braking and the power consumption of the power steering motor during sharp turns.

[0033] On the other hand, when the power supplied by the DCDC converter 17 is greater than the power consumed by the auxiliary load 12, that is, when the power consumed by the auxiliary load 12 can be covered by the power supplied by the DCDC converter 17, power is supplied from the DCDC converter 17 to the auxiliary battery 13, so that the auxiliary battery 13 is in a charging state, and the voltage value instructed to the DCDC converter 17 becomes approximately the same as the voltage value of the auxiliary battery 13.

[0034] Therefore, when the engine 14 is stopped during intermittent operation of the engine 14, if the voltage value instructed to the DCDC converter 17 and the voltage value of the auxiliary battery 13 are approximately the same and the difference between the voltage value instructed to the DCDC converter 17 and the voltage value of the auxiliary battery 13 is within a predetermined voltage value and this state continues for a predetermined time, the supply power determination unit 22 determines that the supply power of the DCDC converter 17 is greater than the power consumption of the auxiliary load 12.

[0035] When the supply power determination unit 22 determines that the power supplied by the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12 while the engine 14 is stopped during the intermittent operation of the engine 14 by the engine intermittent operation unit 21, the engine starting unit 23 starts and operates the engine 14. As a result, when the power supplied by the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12, power can be supplied to the auxiliary load 12 by the power generation of the alternator 15.

[0036] While the engine 14 is being operated by the engine starting unit 23, the engine stopping unit 24 stops the engine 14 if the supply power determination unit 22 determines that the supply power of the DCDC converter 17 is greater than the power consumption of the auxiliary load 12. This allows the engine 14 to be restarted from being stopped during the intermittent operation of the engine 14, thereby improving the fuel efficiency of the vehicle and reducing exhaust gas.

[0037] The flow of the intermittent engine operation control will be described with reference to FIG.

[0038] The engine intermittent operation control determines, based on the functions of the ECU 20 described above according to the following procedure, when the engine 14 is stopped during intermittent operation of the engine 14, based on the difference between the voltage command value of the DCDC converter 17 and the voltage value of the auxiliary battery 13, whether the supply power of the DCDC converter 17 is smaller than the power consumption of the auxiliary load 12.

[0039] In step S11, it is confirmed whether or not the engine 14 is in intermittent operation by the intermittent engine operation unit 21. If the engine 14 is in intermittent operation, the process proceeds to step S12.

[0040] In step S12, it is confirmed whether or not the engine 14 is stopped during the intermittent operation of the engine 14. If the engine 14 is stopped during the intermittent operation, the process proceeds to step S13.

[0041] In step S13, the supply power determination unit 22 checks whether the difference between the voltage value instructed to the DCDC converter 17 and the voltage value of the auxiliary battery 13 is equal to or greater than a predetermined voltage value. If the difference is equal to or greater than the predetermined voltage value, power is supplied from the auxiliary battery 13 to the auxiliary load 12, the auxiliary battery 13 is in a discharging state, and the power supplied by the DCDC converter 17 is smaller than the power consumed by the auxiliary load 12. Therefore, the power consumed by the auxiliary load 12 cannot be covered by the power supplied by the DCDC converter 17 alone. In this case, the process proceeds to step S14.

[0042] In step S14, the engine 14 is started and operated by the engine starting unit 23, and the alternator 15 generates power to supply electric power to the auxiliary load 12.

[0043] In step S15, it is confirmed whether a predetermined time has elapsed in a state where power is being supplied to the auxiliary load 12 by the DC-DC converter 17 and the alternator 15. If the predetermined time has elapsed, the process proceeds to step S16.

[0044] In step S16, the engine 14 is kept in operation while the power generation of the alternator 15 is suppressed, and the auxiliary load 12 is supplied with electric power only by the DC-DC converter 17.

[0045] In step S17, the supply power determination unit 22 checks whether the difference between the voltage value instructed to the DCDC converter 17 and the voltage value of the auxiliary battery 13 is within a predetermined voltage value. If it is within the predetermined voltage value, power is supplied from the DCDC converter 17 to the auxiliary battery 13, the auxiliary battery 13 is in a charging state, and the supply power of the DCDC converter 17 is greater than the power consumption of the auxiliary load 12. Therefore, the power consumption of the auxiliary load 12 is covered by the supply power of the DCDC converter 17. In this case, the process proceeds to step S18.

[0046] In step S18, the engine 14 is stopped by the engine stopping unit 24, and the stopping of the engine 14 during the intermittent operation of the engine 14 is resumed.

[0047] It should be noted that the present invention is not limited to the above-described embodiment and its modified examples, and it is of course possible to make various modifications and improvements within the scope of the matters described in the claims of this application. [Explanation of symbols]

[0048] 10 Vehicle power supply system, 11 Auxiliary equipment, 12 Auxiliary load, 13 Auxiliary equipment battery, 14 Engine, 15 Alternator, 16 Drive battery, 17 DCDC converter, 18 Battery voltage sensor, 20 ECU, 21 Engine intermittent operation unit, 22 Supply power determination unit, 23 Engine start unit, 24 Engine stop unit

Claims

[Claim 1] An auxiliary device including an auxiliary load and an auxiliary battery that supplies power to the auxiliary load; an alternator that supplies electric power generated by the rotation of the engine to the auxiliary machinery; a DC-DC converter connected in parallel with the alternator to convert the voltage of the power of the drive battery and supply the converted voltage to the auxiliary equipment; Equipped with determining, while the engine is stopped during intermittent operation of the engine, a case in which the supply power of the DCDC converter is smaller than the power consumption of the auxiliary load based on a difference between a voltage value of the supply power of the DCDC converter and a voltage value of the auxiliary battery; Vehicle power supply system.

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