Battery failure detection device

Abstract

To provide a battery failure determination device capable of avoiding erroneous determination.SOLUTION: In a power supply circuit 10, power is supplied to a load 11 by a second battery 15 and power is supplied to the load 11 from a first battery 13 after a voltage is stepped down or stepped up by a DC-DC converter 14. A battery failure determination device 20 determines a failure of the second battery 15 based on presence or absence of discharge from the second battery 15 when an output voltage of the DC-DC converter 14 is temporarily lowered. A cycle for temporarily lowering the output voltage of the DC-DC converter 14 is made irregular.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery failure determination device, and particularly to a determination period. [Background technology]

[0002] Some vehicles have an autonomous driving function. Such vehicles have a power supply circuit that supplies power to loads such as a steering device during autonomous driving and a control device that controls the autonomous driving. In the power supply circuit, the voltage from a lead battery is boosted by a DC-DC converter and power is supplied to the load, and power is also supplied to the same load by a lithium battery.

[0003] Patent Document 1 discloses a technique for determining a failure of the lithium battery in the power supply circuit based on whether or not there is discharge from the lithium battery when the output voltage of the DC-DC converter is temporarily lowered. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2016-528870 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the output voltage of the DC-DC converter cannot perfectly follow load fluctuations such as noise and disturbances. Therefore, if a load fluctuation occurs when the output voltage of the DC-DC converter is lowered, the discharge from the lithium battery will also fluctuate, which may result in an erroneous diagnosis of a lithium battery failure.

[0006] In the fault detection method disclosed in Patent Document 1, the output voltage of the DC-DC converter is temporarily reduced at regular intervals. If a load or sensor that operates at regular intervals is present in the power supply circuit, noise will occur at those intervals. Therefore, if the interval at which the output voltage of the DC-DC converter is temporarily reduced during fault detection is approximately synchronized with the load fluctuation interval, the discharge from the lithium battery will also fluctuate with each detection, which may lead to an erroneous detection of a fault in the lithium battery.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a battery failure determination device that can avoid erroneous determination. [Means for solving the problem]

[0008] The battery failure determination device of the present invention is a battery failure determination device that determines battery failure based on whether or not there is discharge from the battery when the output voltage of the DCDC converter is temporarily lowered in a circuit in which power is supplied to a load by a battery and the voltage is stepped up or down by a DCDC converter from a power source other than the battery and then supplied to the load, and is characterized in that the period during which the output voltage of the DCDC converter is temporarily lowered is irregular.

[0009] By adopting the above configuration, it is possible to avoid erroneous determination.

[0010] In the present invention, one of the periods is preferably determined using the battery temperature detected by a battery temperature sensor.

[0011] With the above configuration, the period is calculated using the detection value of the battery temperature sensor, which is susceptible to noise such as external disturbance, so that an irregular period can be reliably calculated. [Effects of the Invention]

[0012] According to the battery failure determination device of the present invention, erroneous determination can be avoided. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a circuit diagram illustrating a power supply circuit according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control unit. [Figure 3] 10 is a graph showing time-series changes in a determination signal. [Figure 4] FIG. 4 is a flowchart showing the flow of failure determination control. DETAILED DESCRIPTION OF THE INVENTION

[0014] An example of an embodiment of the present invention will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating understanding of the present invention, and can be appropriately changed according to the application, purpose, specifications, etc.

[0015] The battery failure determination device 20 determines a failure of the second battery 15 provided in the power supply circuit 10 that supplies power to the load 11 of the vehicle. The battery failure determination device 20 can avoid erroneous determination, as will be described in detail later. The battery failure determination device 20 of this embodiment is provided in a vehicle, but is not limited to this. It may also be provided in a device other than a vehicle that is equipped with a battery.

[0016] In this embodiment, the vehicle is a BEV (Battery Electric Vehicle) that runs by driving a motor (not shown) using only the power of a battery for driving. However, the vehicle of the present invention may also be an HEV (Hybrid Electric Vehicle) that runs by driving a gasoline engine and a motor. Furthermore, the vehicle of the present invention may also be an engine vehicle that runs by driving only a gasoline engine.

[0017] The vehicle of this embodiment has an automatic driving function. The automatic driving function is a function that allows the vehicle to travel automatically without the driver's intervention. The automatic driving function also includes a function that assists in any one of acceleration, steering, and braking.

[0018] [Power circuit] The power supply circuit 10 will be described with reference to FIG.

[0019] As described above, the power supply circuit 10 supplies power to the load 11 of the vehicle. More specifically, when the power supply circuit 10 supplies power via the DCDC converter 14, the power supply circuit 10 steps down or steps up the output voltage of the first battery 13 and supplies power to the load 11, and supplies power to the load 11 from the second battery 15. Note that when the power supply circuit 10 supplies power to the load 11 only from the first battery 13 without via the DCDC converter 14, power is not supplied from the second battery 15.

[0020] The load 11 is an electronic device installed in the vehicle. For example, the load 11 is any 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, or a control device that controls automatic driving. The load 11 also includes a load that operates only during manual driving, a load that operates only during automatic driving, and a load that operates in both manual and automatic driving.

[0021] The first battery 13 is a lead battery and is the main power source for the load 11. The first battery 13 supplies power to the load 11 via either an electric path passing through the relay R or an electric path passing through the DC-DC converter 14.

[0022] The DC-DC converter 14 increases or decreases the voltage of the DC current supplied from the first battery 13 according to the load 11. The DC-DC converter 14 is provided on an electric path from the first battery 13 to the load 11, and is connected in parallel with a relay R with respect to the load 11.

[0023] The second battery 15 is a lithium ion battery and serves as an auxiliary power source for the load 11. The second battery 15 is connected to the load 11 in parallel with the first battery 13.

[0024] In the power supply circuit 10, when the vehicle is being manually driven, the relay R is turned on. This causes the first battery 13 to supply power to the load 11 through an electrical path passing through the relay R. At this time, no current flows through the electrical path of the DC-DC converter 14, so the DC-DC converter 14 is not driven. Also, no power is supplied from the second battery 15 to the load 11.

[0025] On the other hand, when the vehicle is in autonomous driving mode, the relay R is turned off. As a result, no current flows through the electrical path passing through the relay R, and the first battery 13 supplies power to the load 11 via the DC-DC converter 14. At this time, the DC-DC converter 14 increases or decreases the voltage to a level appropriate for the load 11. Power is also supplied to the load 11 from the second battery 15.

[0026] [Battery failure detection device] The battery failure determination device 20 will be described with reference to FIGS.

[0027] 1, a battery failure determination device 20 determines a failure of a second battery 15 provided in a power supply circuit 10 that supplies power to a vehicle load 11. The battery failure determination device 20 can avoid erroneous determination, as will be described in detail later.

[0028] As shown in FIGS. 1 and 2, the battery failure determination device 20 includes a voltage sensor 21, a current sensor 22, a battery temperature sensor 23, and an ECU (Electronic Control Unit) 30 as a control unit, each of which will be described in detail later.

[0029] The voltage sensor 21 detects the output voltage of the DCDC converter 14. The voltage sensor 21 is provided between the DCDC converter 14 and the load 11. The current sensor 22 detects the discharge current of the second battery 15. The current sensor 22 is provided between the second battery 15 and the load 11. The battery temperature sensor 23 is a thermistor and detects the temperature of the second battery 15. The battery temperature sensor 23 is provided near the second battery 15.

[0030] During the autonomous driving of the vehicle, the ECU 30 determines whether the second battery 15 has failed. More specifically, as shown in Fig. 3, the ECU 30 determines whether the second battery 15 has failed based on whether or not the second battery 15 has discharged when the output voltage of the DC-DC converter 14 is temporarily lowered during the autonomous driving of the vehicle.

[0031] The ECU 30 has a CPU (Central Processing Unit) which is an arithmetic processing unit, and storage units such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and performs signal processing according to a program pre-stored in the ROM while utilizing the temporary storage function of the RAM.

[0032] 2, the ECU 30 has an automatic driving determination unit 31, a period calculation unit 32, a period elapsed time determination unit 33, and a failure determination unit 34, each of which will be described in detail later. The automatic driving determination unit 31, the period calculation unit 32, the period elapsed time determination unit 33, and the failure determination unit 34 are realized by the CPU executing programs stored in the ROM or RAM.

[0033] The autonomous driving determination unit 31 determines whether the vehicle is performing autonomous driving. Specifically, if the occupant has set the autonomous driving mode using a setting switch or the like, it determines that the vehicle is performing autonomous driving.

[0034] As shown in FIG. 3, the period calculation unit 32 calculates the period λ n is irregular with a period λ n Calculate the period λ n is the period for temporarily lowering the output voltage of the DC-DC converter 14 when determining whether or not there is a failure in the second battery 15. According to the period calculation unit 32, the period λ for temporarily lowering the output voltage of the DC-DC converter 14 is n By making the period irregular, it is possible to avoid erroneous determination.

[0035] Conventionally, when determining whether or not the second battery 15 is faulty based on whether or not there is discharge from the second battery 15 when the output voltage of the DCDC converter 14 is temporarily lowered, the period for temporarily lowering the output voltage of the DCDC converter 14 is constant.

[0036] Here, since the output voltage of the DCDC converter 14 cannot completely follow load fluctuations such as noise or disturbances, if a load fluctuation occurs when the output voltage of the DCDC converter 14 is lowered, the discharge from the second battery 15 also fluctuates, which may result in an erroneous determination of a failure of the second battery 15.

[0037] In the control of temporarily lowering the output voltage of the DC-DC converter 14 at regular intervals, if a load or sensor that operates at regular intervals is present in the power supply circuit 10, noise occurs at those intervals. Therefore, if the interval at which the output voltage of the DC-DC converter 14 is temporarily lowered during failure determination is approximately synchronized with the interval of load fluctuations, the discharge from the second battery 15 also fluctuates for each determination, which may lead to an erroneous determination of a failure in the second battery 15.

[0038] According to the cycle calculation unit 32, the cycle λ for temporarily lowering the output voltage of the DC-DC converter 14 when determining whether there is a failure in the second battery 15 is n By making the period of time irregular, it is not synchronized with the period of operation of the load or sensor present in the power supply circuit 10, and the above-mentioned erroneous determination can be avoided.

[0039] Specifically, the period calculation unit 32 calculates the period λ using the following equation (1): n Calculate. λ n =λ min +mod(R n , (λ max -λ min ))···(1) In equation (1), λ min is the minimum period and is determined based on the performance of the ECU 30. max is the maximum period and is determined from a safety standpoint. nis a random value between 0 and 1. mod(R n , (λ max -λ min )) is a modular function in R n λ max -λ min The remainder is the remainder when divided by λ max -λ min In other words, equation (1) is min λ max -λ min The value is the sum of the two smaller random values.

[0040] Furthermore, the cycle calculation unit 32 calculates R1, which is the cycle from the first judgment to the second judgment (first cycle), using the following formula (2): R0, which is the cycle from when the power is turned on to the first judgment, is a predetermined cycle. R1=Rand(ΣT batt )···(2) In equation (2), ΣT batt is the integrated value of the battery temperature detected by the battery temperature sensor 23 during a certain time period. batt ) is the seed value of ΣT batt This is the random number obtained when

[0041] Here, sensors such as thermistors that transmit detection values ​​using a weak current, such as battery temperature sensor 23, tend to be susceptible to noise such as external disturbances. By using the detection value of battery temperature sensor 23, which is prone to noise, to calculate the initial period, period calculation unit 32 can reliably calculate an irregular initial period.

[0042] Furthermore, the period calculation unit 32 calculates R2 and subsequent periods, which are the periods from the second determination to the third determination, using the following equation (3). R n =Rand(R n―1 )···(3) In equation (3), Rand(R n―1 ) sets the seed value to the previous random value, R n―1 This is the random number obtained when

[0043] The period elapse determination unit 33 determines whether the irregular period calculated by the period calculation unit 32 has elapsed.

[0044] The failure determination unit 34 temporarily reduces the output voltage of the DC-DC converter 14 (generates a detection pulse). At this time, since the voltage of the second battery 15 is the highest, if the second battery 15 is normal, the failure determination unit 34 discharges from the second battery 15. Specifically, if a current value equal to or greater than a predetermined value is measured from the current sensor 22, the second battery 15 is determined to be normal. On the other hand, if a current value equal to or greater than the predetermined value is not measured from the current sensor 22, the second battery 15 is determined to be abnormal.

[0045] [Battery failure detection control] The flow of the battery failure determination control will be described with reference to FIG.

[0046] In the battery failure determination control, the battery failure determination device 20 determines whether or not there is a failure in the second battery 15 based on the functions of the ECU 30 described above according to the following procedure. In step S11, the automatic driving determination unit 31 determines whether or not automatic driving is being performed. If automatic driving is being performed, the process proceeds to step S12.

[0047] In step S12, the period calculation unit 32 calculates an irregular period for temporarily lowering the output voltage of the DC-DC converter 14. In step S13, the period elapse determination unit 33 determines whether the calculated period has elapsed. If the period has elapsed, the process proceeds to step S14.

[0048] In step S14, the failure determination unit 34 temporarily reduces the output voltage of the DC-DC converter 14, detects whether or not there is discharge from the second battery 15, and determines whether or not there is a failure in the second battery 15. In step S15, the current cycle is reset.

[0049] It should be noted that the present invention is not limited to the above-described embodiment and its modifications, and various changes and modifications are possible within the scope of the claims of this application. [Explanation of symbols]

[0050] 10 power supply circuit, 11 load, 13 first battery (power supply separate from battery), 14 DC-DC converter, 15 second battery (battery), 20 battery failure determination device, 21 voltage sensor, 22 current sensor, 23 battery temperature sensor, 30 ECU, 31 automatic driving determination unit, 32 period calculation unit, 33 period elapse determination unit, 34 failure determination unit

Claims

1. A battery failure determination device for a power supply circuit in which power is supplied to a load by a battery, and a voltage is stepped up or stepped down by a DC-DC converter from a power source other than the battery and then supplied to the load, the device determining a failure of the battery based on whether or not there is discharge from the battery when the output voltage of the DC-DC converter is temporarily lowered, comprising: The output voltage of the DC-DC converter is temporarily reduced at an irregular interval. Battery failure determination device.

2. 2. The battery failure determination device according to claim 1, one of the periods is determined using a battery temperature detected by a battery temperature sensor; Battery failure determination device.

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