Power management device and power management system

Abstract

In a power management device (10) provided with a processor (100) for managing a power supply (1) mounted in a vehicle, the processor (100) determines the state of the vehicle, and switches the voltage used for managing the power supply among the voltages detected respectively by a plurality of different voltage detection means according to the state of the vehicle.

Description

Power management device and power management system

[0001] The present invention relates to a power management device and a power management system.

[0002] A technology is known that stores information on an abnormality that occurs during engine start-up if the sampled value of the battery voltage detected after power reception for engine start-up begins falls below a predetermined threshold and engine start-up based on power reception is not completed even after a predetermined time has elapsed (Patent Document 1).

[0003] Patent No. 4538852

[0004] However, although the appropriate method for detecting battery voltage varies depending on the state of the vehicle, the technology described in Patent Document 1 has the problem that it only has one means for detecting battery voltage, and therefore cannot detect battery voltage using a means appropriate for each state of the vehicle.

[0005] An object of the present invention is to provide a power supply management device and a power supply management system that can detect the voltage of a power supply by a means suitable for the state of a vehicle.

[0006] The present invention solves the above-mentioned problem by determining the state of the vehicle and switching the voltage used to manage the power supply from among the voltages detected by a plurality of different voltage detection means in accordance with the state of the vehicle.

[0007] According to the present invention, the voltage of the power supply can be detected by a means suitable for the state of the vehicle.

[0008] Fig. 1 is a schematic diagram of a power supply management system according to this embodiment. Fig. 2 is a diagram showing the sampling period for detecting each voltage in this embodiment. Fig. 3 is a diagram for explaining changes in the sampling frequency for detecting each voltage in this embodiment. Fig. 4 is a flowchart showing the control procedure of a voltage detection method at engine start executed by a power supply management device according to this embodiment.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a power supply management system according to the present invention will be described with reference to the accompanying drawings.

[0010] FIG. 1 is a schematic diagram of a power supply management system according to this embodiment. In this embodiment, the power supply management system is installed in a vehicle equipped with a battery. As shown in FIG. 1, the power supply management system 1000 includes a battery 1, a battery sensor 2, a battery fuse terminal (BFT) 3, a fuse box 4, a starter motor 5, a start switch 6, an alternator 7, an auxiliary battery 8, a relay 9, a power supply management device 10, loads 21 to 25, a power line 30, and a communication network 40. The power line 30 is a harness, a bus bar, or the like. The communication network 40 is an in-vehicle communication network such as CAN or LIN. In FIG. 1, the thick lines correspond to the power line 30, and the dotted lines correspond to the communication network 40.

[0011] The battery 1 is a low-voltage power supply for operating the starter motor 5, the power management device 10, and the loads 21 to 25, such as auxiliary equipment. The battery 1 is electrically connected to the starter motor 5, the alternator 7, the auxiliary battery 8, the power management device 10, and the loads 21 to 25. The battery 1 is a battery of 60 volts or less, such as a 12 V battery, and is, for example, a secondary battery such as a lithium-ion battery or a lead battery.

[0012] A battery sensor 2 is connected to the battery 1. Specifically, the battery sensor 2 is electrically connected to one of the positive terminal or the negative terminal of the battery 1. The other terminal of the battery 1 is connected to the BFT 3 or the fuse box 4. The battery sensor 2 is, for example, an IBS (Intelligent Battery Sensor). The battery sensor 2 detects the voltage of the battery 1. The battery sensor 2 transmits the detected voltage value to the power supply management device 10 via the communication network 40. As will be described later, the battery sensor 2 is one of voltage detection means, and when the loads 22 to 24 are operating, the voltage detected by the battery sensor 2 is used to manage the battery 1. The battery sensor 2 is an example of a "sensor connected to a power source" as defined in the claims. The battery sensor 2 is not limited to detecting the voltage of the battery 1, and may also detect the current of the battery 1.

[0013] The BFT 3 is connected to the battery 1 and includes a fuse with a high voltage resistance. Multiple fuses are connected to the branch of the power line 30. The branched power line 30 is connected to the starter motor 5, alternator 7, auxiliary battery 8, and fuse box 4. If a large current exceeding the rated current flows through these branch wirings, the fuse melts to cut off the current, protecting the electric wires, loads, and various devices connected downstream of the fuse. The fuse box 4 further branches one branch of the power line 30 connected to the battery 1 downstream of the BFT 3. The power management device 10 and the load 21 are connected to the power line 30 branched by the fuse box 4. The fuse box 4 includes multiple fuses with a smaller current capacity than the fuses included in the BFT 3. Each of the multiple fuses is connected to a branch of the power line 30.

[0014] The starter motor 5 is a motor for starting an engine (not shown), which is a drive source of the vehicle, when the vehicle starts. In this embodiment, when a start signal indicating that the engine should be started is transmitted from the power management device 10 to the starter motor 5 via the communication network 40, the starter motor 5 starts the engine by receiving power from the battery 1.

[0015] The start switch 6 is a switch required to start the vehicle engine. A vehicle user can start the vehicle engine by pressing the start switch 6. When the start switch 6 detects that it has been pressed by the user, it transmits a start signal indicating that the engine should be started to the power management device 10 via the communication network 40.

[0016] The alternator 7 is a generator that generates electricity based on the power of the vehicle engine. The alternator 7 supplies the generated power to the battery 1 to charge the battery 1. In this embodiment, when the alternator 7 is in a normal state, the battery 1 is charged by receiving power supplied by the alternator 7.

[0017] The auxiliary battery 8 is a battery that shuts off the relay 9 and supplies power from the auxiliary battery 8 to the load 25 to continue functioning in the event of, for example, a short circuit failure in the circuit on the BFT 3 side of the relay 9. The auxiliary battery 8 is electrically connected to the battery 1 via the relay 9. The auxiliary battery 8 is not particularly limited and may be any primary battery, secondary battery, or the like. However, it is preferable to use a battery with at least one of an output and a capacity smaller than that of the battery 1. In this embodiment, the auxiliary battery 8 supplies power to the load as a backup in the event of a failure of the alternator 7. The relay 9 is an element that switches the electrical circuit on and off and may be, for example, a semiconductor switching element such as an FET or an IPD, or a mechanical relay having an operating contact and a coil. In the event of a failure of the alternator 7, the relay 9 is turned off to prevent power from the auxiliary battery 8 from flowing to the BFT 3 side via the contacts of the relay 9.

[0018] The power management device 10 is a device that manages a battery 1, which is a power source. For example, the power management device 10 is an electronic control unit (ECU) such as an engine control module (ECM). The power management device 10 is configured by a microcomputer that integrates a CPU, a ROM, a RAM, and the like. The CPU, which is a processor 100, reads program code of software that realizes each function of this embodiment from the ROM, loads it into the RAM, and executes each function. In this embodiment, the processor 100 manages the battery 1 by monitoring the state of the battery 1 and performing abnormality diagnosis and charging control of the battery 1. More specifically, the processor 100 monitors the voltage of the battery 1 and performs abnormality diagnosis and charging control of the battery 1 based on the voltage of the battery 1. In this embodiment, the power management device 10 also controls engine start. Specifically, when the processor 100 receives a start signal from a start switch 6, it transmits a start signal to a starter motor 5.

[0019] In this embodiment, the power supply management system 1000 includes a plurality of different voltage detection means. The voltage detection means detect the voltage of the battery 1 using respective methods. The processor 100 manages the battery 1 using the voltages detected by the plurality of voltage detection means. Specifically, the processor 100 determines the state of the vehicle and switches the voltage used to manage the battery 1 from among the voltages detected by the plurality of voltage detection means according to the state of the vehicle. A plurality of different vehicle states are set in advance, and for each vehicle state, corresponding determination conditions and corresponding voltage detection means are pre-stored in memory. That is, the processor 100 acquires vehicle information, determines the vehicle state based on the vehicle information and the determination conditions, and switches the voltage used to manage the battery 1 to the voltage detected by the voltage detection means corresponding to the vehicle state. The vehicle information is information transmitted from various devices mounted on the vehicle, such as the engine, loads, and other ECUs.

[0020] The vehicle state includes a state in which the vehicle engine is running (engine start), a state in which a load mounted on the vehicle is operating (load operation), a state in which one of the multiple voltage detection means is malfunctioning (failure), and a state in which the auxiliary battery 8 is performing backup operation (backup operation). Engine start refers to the period from when the engine begins to start until engine start is completed. Load operation refers to a state in which the engine is running after engine start is completed, including normal vehicle driving and vehicle parking. For example, when the processor 100 acquires a start signal from the start switch 6 as vehicle information, it determines that the vehicle state is in a state in which the vehicle engine is running. Furthermore, the processor 100 acquires engine speed information from the engine as vehicle information, and when the engine speed reaches a certain speed or higher, it determines that the vehicle state is in a state in which a load mounted on the vehicle is operating.

[0021] The multiple voltage detection means include, for example, the power supply terminal of the power management device 10 itself, the battery sensor 2, and an ECU other than the power management device 10. The voltage detected by the power supply terminal of the power management device 10 is the power supply voltage input from the battery 1 to the power supply terminal of the power management device 10. In other words, the power supply voltage detection of the power management device 10 itself detects the voltage input to the power supply terminal of the power management device 10.

[0022] In this embodiment, when the vehicle's engine is running, the processor 100 manages the voltage of the battery 1 based on the voltage detected by the power supply terminal of the power supply management device 10. First, when a start signal indicating that the engine should be started is transmitted from the start switch 6, the processor 100 starts the engine by transmitting a start signal to the starter motor 5. Then, when the vehicle's engine is starting, the power supply terminal of the power supply management device 10 detects the voltage input to the power supply terminal at a predetermined sampling frequency. At this time, when the vehicle's engine is starting, the sampling frequency is changed to twice or more than twice the value obtained by multiplying the current fluctuation period of the starter motor 5 by the rotation speed of the starter motor 5.

[0023] Here, the sampling period of the power supply voltage detection by the power management device 10 and the voltage detection by the battery sensor 2 will be described using FIG. 2 . FIG. 2 is a diagram illustrating the sampling period of each voltage detection in this embodiment. In FIG. 2 , the horizontal axis represents time and the vertical axis represents voltage. FIG. 2 shows a graph illustrating voltage fluctuations during engine start-up. In FIG. 2 , S1 indicates that voltage detection by the battery sensor 2 is repeatedly performed at a predetermined sampling period. S2 indicates that power supply voltage detection by the power management device 10 is repeatedly performed at a predetermined sampling period. The sampling frequency of voltage detection by the battery sensor 2 is lower than the sampling frequency of power supply voltage detection by the power management device 10. In other words, the sampling period of voltage detection by the battery sensor 2 is longer than the sampling period of power supply voltage detection by the power management device 10. As shown in FIG. 2 , when the engine starts, the voltage temporarily drops sharply. At this time, the sampling period of the battery sensor 2 detects the voltage drop at time T2, which delays the timing of detecting the sudden voltage change. As a result, the voltage at time T1, when the voltage is at its lowest, cannot be detected.

[0024] In order for the battery sensor 2 to accurately detect the sudden voltage change during engine start, the processor 100 must change the sampling frequency of the battery sensor 2 to a frequency higher than the normal sampling frequency. However, this change requires communication time. This creates a waiting time before the engine starts, which can be dissatisfying for the user. This waiting time cannot be reduced unless the power management device 10 includes another voltage detection means. To avoid this situation, in this embodiment, the processor 100 manages the voltage of the battery 1 during engine start using the power supply voltage detected by the power terminal of the power management device 10 itself. As shown in FIG. 2 , the sampling frequency of the power supply voltage detection by the power management device 10 can detect the voltage at time T1, when the voltage is at its lowest, even if the voltage temporarily drops suddenly during engine start.

[0025] Furthermore, the power supply voltage detected by another ECU may be used to manage the battery 1. For example, the processor 100 acquires a detected value of the voltage input to the load 21 from another ECU that controls the load 21 via the communication network 40. In this embodiment, when there is a difference between the power supply voltage of the power management device 10 and the voltage detected by the battery sensor 2, the processor 100 may compare the detected voltage value acquired from the other ECU to determine which of the power supply voltage of the power management device 10 and the voltage detected by the battery sensor 2 is normal. The processor 100 also acquires a detected value of the voltage of the auxiliary battery 8 from another ECU that controls the load 25. In this embodiment, when power supply from the auxiliary battery 8 to the load 25 starts (during backup operation), the processor 100 acquires a detected value of the voltage of the auxiliary battery 8 from the other ECU that controls the load 25. As a result, the state of the auxiliary battery 8 can be monitored even when the relay 9 is turned off due to backup operation.

[0026] Next, the sampling frequencies of the power supply voltage detection by the power management device 10 and the voltage detection by the battery sensor 2 at engine start will be described using FIG. 3 . FIG. 3 is a diagram for explaining changes in the sampling frequencies of each voltage detection in this embodiment. In FIG. 3 , graph A shows the on / off state of the start switch 6. When the signal of the start switch 6 is at a high level, the start switch 6 is in an on state. When the signal of the start switch 6 is at a low level, the start switch 6 is in an off state. Graph B shows the state of the sampling frequency of the power supply voltage detection by the power management device 10. The sampling frequency of the power supply voltage detection by the power management device 10 switches between a low-level frequency and a high-level frequency that is higher than the low-level frequency. The sampling frequency of the voltage detection by the battery sensor 2 switches between a low-level frequency and a high-level frequency that is higher than the low-level frequency.

[0027] 3, at time T1, the start switch 6 transitions from low to high, switching from an off state to an on state. When the start switch 6 transitions to the on state, the sampling frequency of the power supply voltage detection by the power management device 10 is changed from low to high. The processor 100 also transmits a change instruction S to the battery sensor 2 via the communication network 40, instructing the battery sensor 2 to change the sampling frequency. When the battery sensor 2 receives the change instruction S, the battery sensor 2 changes the sampling period. Because a time lag occurs due to communication time and the like between the battery sensor 2 and the power management device 10 when the sampling period of the battery sensor 2 is changed, the sampling frequency of the battery sensor 2 is changed from low to high at time T2, which is later than time T1.

[0028] Here, an example of power supply voltage detection at engine start by the power management device according to this embodiment will be described. FIG. 4 is a flowchart showing the control procedure of a voltage detection method at engine start executed by the power management device according to this embodiment. When the start switch 6 is pressed, the processor 100 starts the control flow from step S1. Specifically, when the processor 100 receives a start signal from the start switch 6 indicating that the engine is to be started, the processor 100 recognizes that the start switch 6 has been pressed. Note that, in this embodiment, the power supply voltage detection by the power management device 10 is repeatedly performed at a constant sampling frequency. Furthermore, when the processor 100 recognizes that the start switch 6 has been pressed, the processor 100 separately executes control to start the engine in parallel with the control flow of FIG. 4 .

[0029] In step S1, the processor 100 changes the sampling frequency of the power supply voltage detection currently being executed by the power management device 10. Specifically, the sampling frequency is changed to twice or more than twice the value obtained by multiplying the current fluctuation period of the starter motor 5 by the rotation speed of the starter motor 5. As a result, the power supply voltage detection of the power management device 10 is repeatedly executed at the changed sampling frequency. In step S2, the processor 100 determines whether engine start is complete. For example, if the engine rotation speed is equal to or greater than a certain rotation speed, the processor 100 determines that engine start is complete. If the engine rotation speed is less than the certain rotation speed, the processor 100 determines that engine start is not complete. If it is determined that engine start is complete, the processor 100 proceeds to step S3. If it is determined that engine start is not complete, the processor 100 returns to step S2 and repeats the following flow until engine start is complete.

[0030] In step S3, processor 100 returns the sampling frequency of the power supply voltage detection being executed by power management device 10 to the sampling frequency before the change in step S1. In step S4, processor 100 determines the state of battery 1 based on the voltage and current at the timing when the voltage was lowest among the voltages detected by power supply voltage detection by power management device 10 during engine start.

[0031] Next, we will explain power management in a state where the loads are operating after the engine start is complete. When the power management device 10 detects the power supply voltage while the loads 21 to 24 are operating, the error in the detected value of the power supply voltage relative to the actual voltage of the battery 1 increases due to increases or decreases in the current consumption of the power management device 10. As a result, if the processor 100 monitors the status of the battery 1 using the power supply voltage of the power management device 10 itself, it may make an erroneous determination, such as determining that the battery 1 is not faulty when it is, or determining that the battery 1 is faulty when it is not. Furthermore, if the processor 100 controls the charging voltage of the battery 1 using voltage information with a large error, the voltage applied to the battery 1 may become too high or too low, accelerating the deterioration of the battery 1. However, the power management device 10 cannot correct or compensate for such errors without other voltage detection means other than the power terminals of the power management device 10.

[0032] To avoid such a situation, when the vehicle is in a state in which the loads 21 to 24 are operating, the processor 100 manages the battery 1 using the voltage detected by the battery sensor 2. For example, the processor 100 receives a detected voltage value from the battery sensor 2 via the communication network 40. The battery sensor 2 detects the voltage of the battery 1 at a constant sampling frequency and transmits the detected voltage to the power management device 10.

[0033] Furthermore, when the vehicle is in a state where one of the plurality of voltage detection means is faulty, the processor 100 uses the voltage detected by the voltage detection means other than the faulty voltage detection means to manage the battery 1. For example, when one of the voltage detection means of the power supply terminal of the power management device 10 and the battery sensor 2 is faulty, the processor 100 uses the voltage detected by the other voltage detection means (the voltage detection means other than the faulty voltage detection means).

[0034] Furthermore, when the vehicle is in a state in which the auxiliary battery 8 is operating instead of the alternator 7 to supply power to the load 25, the processor 100 may acquire the voltage of the auxiliary battery 8 from the load 25 that monitors the voltage of the auxiliary battery 8. In this embodiment, when the alternator 7 fails, the power supply to the load 25 is switched from the alternator 7 to the auxiliary battery 8.

[0035] As described above, the processor 100 switches the voltage used to manage the battery 1 from among the voltages detected by the multiple voltage detection means according to the state of the vehicle, thereby reducing measurement errors of the voltage of the battery 1 regardless of the state of the vehicle. Therefore, in this embodiment, the amount of stress on the battery 1 while the vehicle is running is reduced, thereby extending the life of the battery 1. Furthermore, the processor 100 can prevent the life of the battery 1 from being shortened by switching to fuel efficiency control when the capacity of the battery 1 is low, and can prevent fuel efficiency from being worsened by not switching to fuel efficiency control when the capacity of the battery 1 is high. Furthermore, the power management device 10 can continue managing the battery 1 even if any of the voltage detection means fails.

[0036] The loads 21 to 25 are loads for operating on-board devices of the vehicle. In this embodiment, the loads 22 to 24 are connected downstream of the power management device 10. The processor 100 controls the operating states of the loads 22 to 24. The processor 100 supplies power from the battery 1 to the loads 22, 23, and 24 to be operated, thereby making them operable.

[0037] The load 21 is electrically connected to the battery 1 without going through the power management device 10, and receives a supply of power from the battery 1. The load 21 is provided with another ECU that controls the load 21. The load 21 is connected to the power management device 10 via a communication network 40. The other ECU that controls the load 21 obtains a detected value of the voltage input to the load 21, and transmits the obtained detected voltage value to the power management device 10 via the communication network 40.

[0038] The load 25 is connected to a power line 30 between the battery 1 and the auxiliary battery 8. The load 25 is provided with another ECU that controls the load 25. The load 25 is connected to the power management device 10 via a communication network 40. The other ECU that controls the load 25 acquires a detected value of the voltage of the auxiliary battery 8 and transmits the detected voltage value to the power management device 10 via the communication network 40.

[0039] As described above, the power supply management device according to this embodiment includes a processor that manages the power supply mounted on the vehicle, and the processor determines the state of the vehicle and switches the voltage used to manage the power supply from among the voltages detected by the different voltage detection means according to the state of the vehicle. This allows the power supply voltage to be detected by a means appropriate for the state of the vehicle.

[0040] In the power management device according to this embodiment, the voltage detection means includes a power terminal of the power management device, and when the processor determines that the vehicle state is at the start of the vehicle engine, it manages the power supply using the voltage detected by the power terminal, thereby managing the voltage of the power supply at the start of the vehicle engine.

[0041] In the power supply management device according to this embodiment, the voltage detection means includes a sensor connected to the power supply, and when the processor determines that the vehicle state is a state in which a load mounted on the vehicle is operating, it manages the power supply using the voltage detected by the sensor, thereby making it possible to manage the voltage of the power supply when the load on the vehicle is operating.

[0042] Furthermore, in the power supply management device according to this embodiment, when the processor determines that the vehicle is in a state in which one of the voltage detection means is malfunctioning, the processor manages the power supply using the voltage detected by the voltage detection means other than the malfunctioning voltage detection means, thereby making it possible to manage the voltage of the power supply when a voltage detection means is malfunctioning.

[0043] Furthermore, in the power supply management device according to this embodiment, when the processor determines that the vehicle is in the engine start state, the power supply terminal changes the sampling frequency for detecting the voltage input to the power supply terminal to twice or more than twice the value obtained by multiplying the current fluctuation period of the starter motor of the vehicle by the rotation speed of the starter motor, thereby enabling more accurate understanding of the change in power supply voltage when the vehicle engine is started.

[0044] The power supply management system according to this embodiment includes a processor that manages the power supply mounted on the vehicle and a plurality of different voltage detection means, and the processor determines the state of the vehicle and switches the voltage used to manage the power supply from among the voltages detected by the plurality of voltage detection means according to the state of the vehicle. This allows the power supply voltage to be detected by a means appropriate for the state of the vehicle.

[0045] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0046] REFERENCE SIGNS LIST 1000... Power supply management system 1... Battery 2... Battery sensor 3... BFT 4... Fuse box 5... Starter motor 6... Start switch 10... Power supply management device 100... Processor 21 to 25... Load 30... Power line 40... Communication network

Claims

1. A power supply management device having a processor that manages a power supply mounted on a vehicle, wherein the processor determines the state of the vehicle and switches the voltage used to manage the power supply from among voltages detected by a plurality of different voltage detection means according to the state of the vehicle.

2. A power supply management device according to claim 1, wherein the voltage detection means includes a power supply terminal of the power supply management device, and when the processor determines that the state of the vehicle is that of the engine of the vehicle starting, the processor manages the power supply using the voltage detected by the power supply terminal.

3. A power supply management device according to claim 1 or 2, wherein the voltage detection means includes a sensor connected to the power supply, and when the processor determines that the state of the vehicle is such that a load mounted on the vehicle is operating, the power supply management device manages the power supply using the voltage detected by the sensor.

4. A power supply management device according to any one of claims 1 to 3, wherein when the processor determines that the state of the vehicle is such that one of the plurality of voltage detection means is malfunctioning, the processor manages the power supply using the voltage detected by a voltage detection means other than the malfunctioning voltage detection means.

5. A power supply management device as claimed in claim 2, wherein when the processor determines that the state of the vehicle is that of the vehicle's engine starting, the processor changes the sampling frequency for detecting the voltage input to the power supply terminal by the power supply terminal to twice or more than twice the value obtained by multiplying the current fluctuation period of the starter motor of the vehicle by the rotation speed of the starter motor.

6. A power supply management system comprising: a processor that manages a power supply mounted on a vehicle; and a plurality of different voltage detection means, wherein the processor determines the state of the vehicle; and switches the voltage used to manage the power supply from among the voltages detected by the plurality of voltage detection means according to the state of the vehicle.

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