JP7622668B2 - Diagnostic device for auxiliary battery - Google Patents

Description

The present invention relates to a diagnostic device for an auxiliary battery mounted on a vehicle, and in particular to determining the timing of diagnosis.

A vehicle is provided with an auxiliary battery as a power source for various auxiliary devices mounted on the vehicle. Since this auxiliary battery deteriorates with use, it is preferable to diagnose its condition. Patent Document 1 describes a device that detects the battery condition of a backup battery during autonomous driving. That is, the battery condition can be grasped by detecting the physical condition such as the internal resistance value, and the detection of the internal resistance can be performed by changing the charging and discharging current of the battery using the output from a DC-DC converter. When the physical condition is being detected by the DC-DC converter, fluctuations in the power consumption state that accompanies driving are undesirable, and therefore it is shown that detection of the physical condition is prohibited when the fluctuations are large.

JP 2019-126208 A

In Patent Document 1, the timing for detecting the battery state is limited, and depending on the driving conditions, diagnosis may not be performed at the appropriate time. In addition, because the output of the DCDC converter is changed to detect the battery state, appropriate power usage may not be achieved depending on the driving conditions.

The present invention is an auxiliary battery diagnostic device for diagnosing an auxiliary battery in a power supply system in which a DCDC converter, a load, and an auxiliary battery are electrically connected and power can be exchanged between them, the device comprising: an estimation unit that estimates the future driving of the vehicle to obtain an estimated driving condition; a prediction unit that predicts whether there is a condition in which the auxiliary battery will be charged or discharged suitable for diagnosing the auxiliary battery based on the estimated driving condition estimated by the estimation unit; a control unit that controls the DCDC converter to charge or discharge the auxiliary battery by exchanging power with the load at a timing when the condition in which the auxiliary battery will be charged or discharged suitable for diagnosing the auxiliary battery predicted by the prediction unit is present; and a diagnosis unit that detects the charge and discharge characteristics of the auxiliary battery and performs a diagnosis while the control unit is charging or discharging the auxiliary battery by exchanging power with the load.

Furthermore, the vehicle may have a memory unit that monitors the current flowing through the load during driving, and determines whether there is a situation in which the auxiliary battery is being charged or discharged that is suitable for diagnosing the auxiliary battery, and stores the determination result. The prediction unit may use the determination result stored in the memory unit for prediction.

Furthermore, the vehicle may have a traffic information acquisition unit that acquires traffic information, and the prediction unit may determine whether there is a situation in which the auxiliary battery is suitable for diagnosing the auxiliary battery and is being charged or discharged, based on the traffic information acquired by the traffic information acquisition unit.

According to the present invention, when a diagnosis is requested, diagnosis of the auxiliary battery can be performed in a location suitable for the diagnosis.

1 is a block diagram showing a configuration of a vehicle including a diagnostic device for an auxiliary battery according to an embodiment; 4 is a diagram showing the relationship between a battery current due to charging and discharging of a battery and a battery voltage. FIG. 4 is a chart showing timing of diagnosis of the auxiliary battery 22; 13 is a flowchart showing a periodic diagnosis process. 1 is a flow chart of a process for performing a diagnosis at a location suitable for the diagnosis. 11 is a flowchart for performing a diagnosis at a location suitable for the diagnosis, including a determination as to whether or not a set route is being traveled. 10 is a flowchart illustrating storage of locations suitable for diagnosis when a route to a destination has been set.

The following describes an embodiment of the present invention with reference to the drawings. Note that the present invention is not limited to the embodiment described here.

"Overall Configuration"
FIG. 1 is a block diagram showing the configuration of a vehicle including an auxiliary battery diagnostic device according to an embodiment of the present invention.

The vehicle 10 is equipped with a large-capacity main battery 12 that has a high-voltage output of several hundred volts or more. A drive motor 16 is connected to the main battery 12 via an inverter 14, and the power of the main battery 12 is converted by the inverter 14 to the desired power and supplied to the drive motor 16, causing the wheels mechanically connected to the drive motor 16 to rotate and the vehicle 10 to travel. In addition, during regenerative braking of the vehicle, the main battery 12 is charged by regenerative power from the drive motor 16.

A DC-DC converter 20 is connected to the main battery 12 and controls the power exchange between the low-voltage system (e.g., 12 V system) that is the output voltage of the auxiliary battery 22 and the main battery 12.

The high-voltage side of the DCDC converter 20 is connected to the main battery 12, and the low-voltage side is connected to the auxiliary battery 22. The low-voltage side of the DCDC converter 20 is connected to the auxiliary battery 22 via an auxiliary power supply line 26, and various auxiliary devices 24 (24-1 to 24-n) are connected to this auxiliary power supply line 26 as loads. Examples of the auxiliary devices 24 include power steering, air conditioners, audio equipment, and various lighting fixtures.

The auxiliary battery 22 is a secondary battery, such as a lithium-ion battery or a nickel-metal hydride battery, and has multiple battery cells connected in series and parallel to ensure a predetermined output voltage and battery capacity.

The auxiliary battery 22 includes a battery cell section 22-1 consisting of multiple battery cells, an internal relay 22-2 that turns on and off external electrical connections, and a monitoring ECU 22-3 that detects the state of the battery cell section 22-1, in particular the state of charge (SOC) that indicates the remaining capacity relative to the battery capacity.

The vehicle 10 also has a current position detection device 30, a navigation device 32, and a communication device 34. The current position detection device 30 is composed of a position detection device such as a GPS, and detects the current location of the vehicle 10. The navigation device 32 has map data and the like, and recognizes the current position on the map, and when a destination is set, stores the set route on the map. Then, when driving along the set route, the current position and the set route are displayed on the map on a display inside the vehicle, providing driving support.

The communication device 34 can connect to traffic information centers, weather forecast sites, and the like via communication lines such as wireless base stations and the Internet, and obtain various types of information. In particular, the traffic information center can provide information on traffic congestion for the planned route to be traveled.

The vehicle 10 is provided with an overall control unit 40, which controls the operation of the DCDC converter 20 according to the state of the auxiliary battery 22, etc. The overall control unit 40 has an estimation unit 40-1, a prediction unit 40-2, a memory unit 40-3, a diagnosis unit 40-4, and a control unit 40-5, and performs various processes.

The current position detection device 30, navigation device 32, and communication device 34 are connected to the overall control unit 40, and various information is provided to the overall control unit 40.

The estimation unit 40-1 of the overall control unit 40 estimates the planned driving route of the vehicle 10 based on information from the navigation device 32, etc. If a destination has been set, the set route may be used as the estimation result as is. The planned driving route may also be estimated based on the driving state of the vehicle 10 and the state of the road branches ahead. Furthermore, the past driving routes of the vehicle 10 may be stored, and the planned driving route may be estimated based on the relationship between the stored driving route and the current driving path. For example, even if a route has not been set, if the same route has been traveled many times in the past, the past route may be estimated as the planned driving route. The estimation unit 40-1 may be provided inside the navigation device 32.

The communication device 34 can also be connected to the outside world via the Internet, etc., and the general control unit 40 can connect to an external site such as an external traffic information center via the communication device 34 to acquire traffic information, i.e., function as a traffic information acquisition unit.

The prediction unit 40-2 predicts the location where the diagnosis of the auxiliary battery 22 will be performed. In other words, it is preferable to perform the diagnosis of the auxiliary battery 22 when traveling through a location where a specified charge/discharge is performed. Therefore, it is determined whether there is a location (area) where a specified charge/discharge is performed on the planned traveling route estimated by the estimation unit 40-1, and predicts that location.

The memory unit 40-3 stores various information. For example, it stores information about past driving routes, set destinations, traffic congestion conditions on driving routes, driving speed, and other information. In addition, for driving patterns that are repeated daily, such as commuting, it is advisable to store the driving conditions in relation to the battery's charging and discharging current.

The diagnostic unit 40-4 controls the DCDC converter 20 to control the charging and discharging of the auxiliary battery 22, and at the same time, measures the battery current and battery voltage of the auxiliary battery 22 to detect the internal resistance of the auxiliary battery 22.

The control unit 40-5 controls the operation of the DCDC converter 20 and charges and discharges the auxiliary battery 22 by exchanging power with the auxiliary 24.

"Diagnosis of auxiliary battery 22"
A battery deteriorates with use, and the full charge capacity decreases. This deterioration is detected as the physical state of the battery. In this embodiment, the internal resistance of the battery is used as the physical state of the battery. That is, as the internal resistance of the battery increases due to deterioration, the battery is diagnosed by detecting the value of the internal resistance. In this embodiment, the internal resistance of the auxiliary battery 22 is detected, and the auxiliary battery 22 is diagnosed according to the value.

Here, the internal resistance of the battery can be calculated from the relationship between the battery voltage and the battery current (charge and discharge characteristics). Figure 2 shows the relationship between the battery current due to charging and discharging the battery and the battery voltage. In this way, when a battery is charged and discharged, a voltage is generated according to the product of this internal resistance and the battery current, so if the discharge current is large, the battery voltage drops, and if the charge current is large, the battery voltage rises. Therefore, the internal resistance can be calculated from the relationship internal resistance = (amount of change in battery voltage) / (amount of change in battery current). At this time, the larger the amount of change in the battery current, the larger the amount of change in the battery voltage, and the accuracy of the detected internal resistance value also improves.

Therefore, when detecting the internal resistance of a battery, i.e. diagnosing the battery, there is a demand to ensure that the amount of change (variation range) of the battery current is as large as possible and that it is within a certain fluctuation range, for example the range shown as "variation range" in Figure 2.

"Diagnosis of auxiliary battery 22"
In the power supply system according to the embodiment, the auxiliary battery 22 is connected to the DCDC converter 20 by an auxiliary power line 26. Various auxiliary devices 24 are connected to the auxiliary power line 26, and power is supplied to the auxiliary devices 24 via the auxiliary power line 26. Normally, the general control unit 40 controls the operation of the DCDC converter 20 so that the voltage of the auxiliary power line 26 is maintained at a constant value. Note that the DCDC converter 20 may be controlled based on the measurement of the current value in the auxiliary power line 26 or the detection of the charge/discharge current of the auxiliary battery 22. The DCDC converter 20 may also have a dedicated control unit and maintain the voltage on the low-voltage side.

By this type of control, the output from the DC-DC converter 20 to the low-voltage side is commensurate with the power consumption of the auxiliary 24 connected to the auxiliary power line 26, and the charge/discharge current of the auxiliary battery 22 does not become too large.

On the other hand, as mentioned above, when diagnosing the auxiliary battery 22, it is necessary to ensure a certain fluctuation range for the battery current (charge/discharge current).

In this embodiment, the auxiliary battery 22 is diagnosed while driving by ensuring a certain fluctuation range of the charge/discharge current of the auxiliary battery 22.

<Prediction of suitable locations for diagnosis>
As described above, in order to diagnose the auxiliary battery 22, it is necessary to be in a state in which the charge/discharge current (battery current) of the auxiliary battery 22 is large. To achieve this, the operation of the DCDC converter 20 needs to be controlled.

In this embodiment, the auxiliary battery 22 is charged and discharged based on power consumption according to the vehicle's driving conditions. Therefore, the auxiliary battery 22 can be diagnosed without reducing the overall energy efficiency of the vehicle 10.

<Charging the auxiliary battery 22>
(i) Supply of charging current from the DCDC converter 20 When the vehicle 10 is decelerating, a regenerative current is generated by regenerative braking of the drive motor. Normally, this regenerative current is used to charge the main battery 12, but the DCDC converter 20 can use this regenerative current to charge the auxiliary battery 22.

(ii) Regenerative current from auxiliary equipment 24 such as electric power steering Electric power steering performs steering using the output of a motor, but regenerative current is generated when a reaction force is received from the tire side. This regenerative current can be used to charge the auxiliary battery 22. In this case, the DCDC converter 20 may stop outputting to the low voltage side, but may also increase the charging current of the auxiliary battery 22 at a predetermined output.

<Discharging of auxiliary battery 22>
(i) Output to High Voltage Side by the DCDC Converter 20 When the vehicle 10 is accelerating, a drive current is supplied to the drive motor 16. Normally, this drive current is supplied by discharging the main battery 12, but a part of this drive current can be supplied by the discharge current of the auxiliary battery 22 via the DCDC converter 20.

(ii) Supply of drive current for auxiliary devices 24 such as electric power steering When turning right or left, the motor drive current for the electric power steering is supplied by the discharge current from the auxiliary battery 22. At this time, it is preferable that the DCDC converter 20 stops operating.

<Consideration of driving conditions>
(i) During stable driving For example, when the vehicle is on a highway and auto-cruise control is being performed, the vehicle does not accelerate, decelerate, or operate the steering wheel as described above. Therefore, the charge/discharge current of the auxiliary battery 22 does not fluctuate widely. For this reason, if the auxiliary battery 22 is to be diagnosed, the charge/discharge current of the auxiliary battery 22 is generated in a predetermined pattern (predetermined fluctuation range) by the DCDC converter 20, and the internal resistance of the auxiliary battery 22 is detected based on the voltage of the auxiliary battery 22 at that time.

(ii) When turning right or left When turning right or left at a relatively wide intersection, the power steering generates a drive current when turning right or left and a regenerative current when returning the steering wheel. At this time, a discharge current and a charge current are generated in the auxiliary battery 22. Therefore, at a large intersection, the fluctuation range of the battery current of the auxiliary battery 22 may exceed a predetermined value.

(iii) Slopes When going uphill, the output of the drive motor 16 is large, and the drive current is large. When going downhill, the regenerative current is large due to regenerative braking of the drive motor 16. Therefore, by controlling the DCDC converter 20 so that a predetermined range of discharge is performed from the auxiliary battery 22 when going uphill and a predetermined range of charge is performed from the auxiliary battery 22 when going downhill, the auxiliary battery 22 can be charged and discharged according to the running state of the vehicle 10, and the auxiliary battery 22 can be diagnosed at this time.

(iv) Tunnels during the day The headlights are turned on when driving through a tunnel. Therefore, when driving through a tunnel, a state in which the current consumption of the auxiliary device 24 is large is likely to occur. Therefore, the inside of the tunnel can be used as a sampling point for a large discharge current, and the outside of the tunnel can be used as a sampling point for a charge current.

(v) Traffic jam information When traffic is heavy and congested, there is little change in the driving conditions and little change in the power consumption of the vehicle 10. Therefore, even if the location is normally suitable for diagnosing the auxiliary battery 22, there is a high possibility that the predetermined fluctuation range for the charge/discharge current cannot be ensured.

<Learning the power consumption status of the auxiliary device 24>
(i) Driving along a set route when a destination is set in the navigation device 32, when the destination is set and the vehicle is traveling along the set route to the destination, it is advisable to store the charge/discharge currents of the main battery 12 and the auxiliary battery 22 and the current consumption of the auxiliary battery 24 in association with the traveling position, traveling speed, etc., as needed.

If such information is stored, it can be analyzed to determine a suitable location for diagnosing the auxiliary battery 22. Therefore, when driving along the same set route, it is possible to predict in advance a suitable location for diagnosing the auxiliary battery 22, and the diagnosis can be performed at that location.

(ii) Frequently traveled roads Even if a route is not set, it is a good idea to determine, while traveling, where a location is suitable for diagnosing the auxiliary battery 22, and if a suitable location is found, to store that location.

Regardless of whether a set route has been set or not, if it is estimated that the vehicle will travel through that location, the auxiliary battery 22 can be diagnosed at that location.

In particular, if the location is one that is frequently passed by, it is preferable to be able to diagnose the auxiliary battery 22 when necessary.

(iii) Learning It is preferable to learn and store suitable locations for diagnosing the auxiliary battery 22 as needed while the vehicle 10 is running. This allows a diagnosis to be performed relatively quickly when it is necessary.

Timing of diagnosis
FIG. 3 is a chart showing the timing of diagnosis of the auxiliary battery 22. In FIG.

When a diagnosis is performed, the date and time of the diagnosis is stored in the general control unit 40, and timing begins without a request to perform a diagnosis. Then, after a predetermined period of time (several months) has elapsed, a request to perform a diagnosis is generated, and the state becomes one in which a request to perform a diagnosis is made.

When a diagnosis request is made, the general control unit 40 finds a time when the diagnosis can be performed and performs the diagnosis. When the diagnosis is performed, the date and time of the diagnosis are stored, and the timing starts without a diagnosis request.

In this way, the auxiliary battery 22 can be diagnosed periodically.

"Diagnostics Processing"
<Regular checkups>
FIG. 4 is a flow chart showing the operation of the general control unit 40 in the periodic diagnosis process shown in the timing chart of FIG.

First, the time is measured from the previous diagnosis (S11), and it is determined whether a predetermined period of time has elapsed (S12). If the result is NO, the process returns to S11.

If S12 is YES, a request to perform diagnosis is generated (S13). Then, it is determined whether a diagnosis completion signal has been received (S14), and if NO, the process returns to S13.

If S14 is YES, the auxiliary battery 22 has been diagnosed, and the time measurement is reset (S15). Then, it is determined whether the process is finished (S16), and if NO, the process returns to S11. S16 may be set to YES when the auxiliary battery 22 is replaced, for example. For a new auxiliary battery 22, an initial diagnosis may be performed and the initial internal resistance value may be stored, after which the process of S11 may be started. The initial internal resistance value may be used as a reference value, and the degree of deterioration may be diagnosed by comparing it with subsequent internal resistance values. For example, the degree of deterioration may be determined by the percentage increase in the initial internal resistance value.

<Diagnosis implementation>
FIG. 5 is a flow chart showing the operation of the general control unit 40 in the process of performing a diagnosis at a location suitable for the diagnosis.

It is determined whether there is a request to perform a diagnosis (S21), and if it is NO, a diagnosis is not necessary and the process ends. If the determination in S21 is YES, the current driving conditions are obtained (S22). The driving conditions include the current location, traveling direction, driving speed, etc.

Next, traffic information is obtained (S23). The traffic information includes congestion information, etc. Then, it is determined whether the location is suitable for diagnosis (S24). In other words, it is determined whether it is appropriate to perform a diagnosis based on the current driving conditions. If this determination is NO, the process returns to S22. For example, if it is determined that the vehicle is entering an intersection and will soon turn right or left, the determination in S24 can be YES.

The judgment in S24 is preferably made by having the estimation unit 40-1 estimate the vehicle's future travel to obtain an estimated travel situation, and the prediction unit 40-2 predicts whether there is a situation in which the auxiliary battery is suitable for diagnosing the auxiliary battery, based on the estimated travel situation obtained by the estimation unit 40-1, to determine a location suitable for diagnosis by predicting whether there is a situation in which the auxiliary battery is suitable for diagnosing the auxiliary battery and the result is YES when the current location reaches the suitable location.

If the determination in S24 is YES, a diagnosis is performed by detecting the internal resistance of the auxiliary battery 22 (S25). Then, it is determined whether the diagnosis is complete (S26), and if it is complete (YES in S26), the process ends.

Figure 6 is a flowchart showing the process of performing a diagnosis at a location suitable for diagnosis, including determining whether the vehicle is traveling along a set route.

It is determined whether the vehicle is traveling along a set route (S31), and if so, it is determined whether a location suitable for diagnosis has been stored along the set route (S32). If the determination in S32 is YES, the stored location suitable for diagnosis is read out (S33).

If the determination in S31 is NO, the driving route at this time is estimated (34). If a route has been estimated in S34 or if the determination in S32 is NO, it is determined whether there is a location suitable for diagnosing the road to be traveled from now on (S35). If the determination in S32 is NO, the determination is made on the set route that will be adopted as the estimated route, and in the case of S34, the determination is made on roads that may be traveled in the direction of travel. If the determination in S35 is NO, there is no location to diagnose, so the process ends.

If S35 is YES, traffic information is obtained (S36). As described above, traffic information includes congestion information, and the location is judged to be suitable for diagnosis taking the traffic information into consideration. In other words, it is judged whether there is any problem in performing diagnosis based on the current driving conditions (S37). If this judgment is NO, the process ends, and if YES, it is judged whether a location suitable for diagnosis has been reached (S38). If this judgment is NO, the process returns to S31, and if the situation has not changed, the process returns to the judgment of S38.

If the determination in S38 is YES, diagnosis is performed by detecting the internal resistance of the auxiliary battery 22 (S39).

In this way, diagnosis of the auxiliary battery 22 can be performed in a location suitable for diagnosis.

Figure 7 is a flowchart that explains how to store locations suitable for diagnosis when a route to a destination has been set.

First, it is determined whether a route has been set (S41). If the determination is NO, the process ends.

If the determination in S41 is YES, the driving conditions are detected (S42) and it is determined whether or not the conditions are suitable for diagnosis (S43). If the determination in S43 is YES, a location suitable for diagnosis is stored (S44). When storing of locations suitable for diagnosis in S44 is finished or if the determination in S43 is NO, it is determined whether driving of the set route has ended (S45), and if NO, the process returns to S42 and repeats. If the determination in S45 is YES, the process ends.

In this way, when driving along a set route, locations suitable for diagnosis can be stored. These locations suitable for diagnosis can be stored together with the set route, and the next time the same route is set, the locations suitable for diagnosis can also be read out. Therefore, when a diagnosis is requested, a diagnosis can be performed promptly.

In the above process, a location suitable for diagnosis is stored when a route is set in S41, but even if a route is not set, a location suitable for diagnosis may be stored automatically or when a switch for storing is turned on. This makes it possible to perform a diagnosis of the auxiliary battery 22 when traveling through a stored location in response to a diagnosis request.

10: vehicle, 12: main battery, 14: inverter, 16: drive motor, 20: DCDC converter, 22: auxiliary battery, 22-1: battery cell section, 22-2: built-in relay, 22-3: monitoring ECU, 24: auxiliary, 26: auxiliary power line, 30: current position detection device, 32: navigation device, 34: communication device, 40: overall control unit, 40-1: estimation section, 40-2: prediction section, 40-3: memory section, 40-4: diagnosis section, 40-5: control section.

Claims (3)

A diagnostic device for an auxiliary battery in a power supply system in which a DC-DC converter, a load, and an auxiliary battery are electrically connected and power can be exchanged between them, the diagnostic device comprising:
an estimation unit that estimates future travel of the vehicle to obtain an estimated travel situation;
a prediction unit that predicts whether there is a situation in which the auxiliary battery is to be charged or discharged, which is suitable for diagnosing the auxiliary battery, based on the estimated traveling situation estimated by the estimation unit;
a control unit that controls the DCDC converter to charge and discharge the auxiliary battery by exchanging power with the load at a timing when the auxiliary battery is in a state where charging and discharging are performed that is suitable for diagnosing the auxiliary battery as predicted by the prediction unit;
a diagnosis unit that detects and diagnoses a charge/discharge characteristic of the auxiliary battery while the control unit is causing the auxiliary battery to charge and discharge by exchanging power with the load;
Equipped with
Diagnostic device for auxiliary batteries. 2. The diagnostic device for an auxiliary battery according to claim 1,
moreover,
a storage unit that monitors a current flowing through the load during running, and determines whether there is a situation in which the auxiliary battery is being charged or discharged that is suitable for diagnosing the auxiliary battery, and stores the determined result;
The prediction unit uses the determination result stored in the storage unit for prediction.
Diagnostic device for auxiliary batteries. 3. The diagnostic device for an auxiliary battery according to claim 1,
Further, a traffic information acquisition unit for acquiring traffic information is provided,
The prediction unit determines whether there is a situation in which the auxiliary battery is to be charged or discharged, which is suitable for diagnosing the auxiliary battery, based on the traffic information acquired by the traffic information acquisition unit.
Diagnostic device for auxiliary batteries.

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