Method and device for controlling vehicle

Abstract

 A vehicle having an automated driving function comprises an alternator (2), a stator motor (5), a load group A (21) including one of two automated driving electrical loads forming a redundant system, a load B group (22) including the other load, a lead acid battery (6), and a backup lithium ion battery (7). During normal driving a circuit breaker switch (13) and a LiB relay (10) are ON. When the vehicle is restarted after idling stop control, the circuit breaker switch (13) is OFF, and electric power is supplied from the lead acid battery 6 to the stator motor (5). For a predetermined period after the restart, priority charging of the lead acid battery (6) is performed while the circuit breaker switch (13) remains OFF, after which the circuit breaker switch (13) is switched to ON and the lithium ion battery (7) is also charged. Even if the idling stop control and an accompanying restart are repeated, the state of charge of a first power storage device does not decrease excessively, and electric power supply to the automated driving electric loads can be reliably continued.

Description

Vehicle control method and device

[0001] The present invention relates to vehicle control that appropriately combines ensuring power supply to the autonomous driving electrical loads and idling stop control in a vehicle equipped with two power storage devices to reliably supply power to the autonomous driving electrical loads required for autonomous driving.

[0002] In vehicles with an autonomous driving function (including so-called driving assistance functions) in which a control system operates the vehicle's steering, brakes, etc., a highly reliable power supply configuration is required as the power source for the electric loads for autonomous driving, including the electric actuators that realize the operation and their control circuits.

[0003] Patent Document 1 discloses a configuration in which, in addition to a main battery consisting of a lead battery that supplies power to the electrical loads required for normal driving, an additional battery consisting of a lithium-ion battery that supplies power to electrical loads for automatic driving such as an ADAS actuator is provided. This configuration is divided into a first load circuit including the main battery and general electrical loads, and a second load circuit including the additional battery and electrical loads for automatic driving, and a circuit interruption mechanism is provided between the two. Voltage fluctuations in each load circuit are monitored to control the interruption and connection of both load circuits.

[0004] However, Patent Document 1 does not disclose anything about idling stop control, and does not disclose how to control the circuit interrupting mechanism when idling stop control is applied.

[0005] Patent Document 2 discloses a vehicle with an idling stop function, which is equipped with a main battery consisting of a lithium-ion battery and a sub-battery consisting of a lead battery. Normal power supply, including cranking, is performed using the main battery in the normal temperature range, and the sub-battery is used to supply power to the starter when the engine temperature is in the low or high range during starting.

[0006] However, in Patent Document 2, no particular consideration is given to ensuring a power source for maintaining the automatic driving function.

[0007] JP 2017-177857 A JP 2008-167652 A

[0008] A method for controlling a vehicle according to the present invention comprises an engine; a generator driven by the engine to generate electricity; a first power storage device and a second power storage device each charged with electricity generated by the generator and supplying electricity required for automatic driving of the vehicle to an electric load for automatic driving; and a disconnecting device provided between the first power storage device and the second power storage device, wherein when a predetermined condition is met while the vehicle is stopped, an idling stop control is executed to stop the engine; when the idling stop control is terminated and the engine is restarted, the engine is cranked using the electric power of the first power storage device with the disconnecting device in a disconnected state; and after the restart, for a predetermined period of time, the first power storage device is charged without charging the second power storage device, with the disconnecting device in a disconnected state.

[0009] When a predetermined condition is met while the vehicle is stopped, idling stop control is executed and the engine is stopped. When this idling stop control is terminated and the engine is restarted, the second power storage device is disconnected from the first power storage device because the disconnecting device is in the disconnected state, and even if power from the first power storage device is consumed by cranking, no power is carried over from the second power storage device to the first power storage device. Then, after the restart, the first power storage device is charged preferentially while the disconnecting device remains disconnected. Because the second power storage device is disconnected, the charge state of the first power storage device is quickly restored.

[0010] Therefore, even if idling stop control and the associated restarts are frequently repeated, the state of charge of the first power storage device will not decrease excessively, and power supply to the automatic driving electrical load can be reliably continued.

[0011] An explanatory diagram showing the system configuration of a power supply system according to an embodiment. An explanatory diagram showing the basic operation of a power supply system according to an embodiment. A time chart showing the charging and discharging of a lead-acid battery and a lithium-ion battery during idling stop control. An explanatory diagram showing the operation during idling stop control.

[0012] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0013] FIG. 1 is an explanatory diagram showing the system configuration of a power supply system in a vehicle with an automatic driving function according to one embodiment. The vehicle of this embodiment is a vehicle that is basically powered by an engine 1. The engine 1 may be, for example, a spark-ignition engine, i.e., a gasoline engine, or may be a diesel engine that uses compression autoignition. The engine 1 includes a generator, for example, an alternator 2. The alternator 2 is driven by a crank pulley 4 of the engine 1 via a belt transmission mechanism 3. The engine 1 also includes a starter motor 5 as a starting motor. The starter motor 5 is of a general type that includes a pinion that engages and disengages with a ring gear (not shown) of the engine 1.

[0014] A vehicle includes many electrical loads, which in one embodiment are roughly divided into a load A group 21 and a load B group 22, as shown in Fig. 1. The load A group 21 includes various electrical loads required for general vehicle operation, such as the fuel system, ignition system, and control system of the engine 1, as well as electrical equipment such as lighting, air conditioning, and audio. The load A group 21 further includes a load (corresponding to a first electrical load in the claims) of one system of automatic driving electrical loads required for automatic driving of the vehicle, which are configured as a redundant system.

[0015] The load B group 22 includes the load of the other system of the automatic driving electric loads necessary for the automatic driving of the vehicle, which is configured as a redundant system (corresponding to the second electric load in the claims).

[0016] These two electric loads for autonomous driving, configured as a redundant system, have substantially the same functions. For example, in a level 2 autonomous driving function, the throttle valve of the engine 1 and the vehicle brakes are controlled by a driving assistance system via electric actuators, and the steering operation of the vehicle is controlled by the driving assistance system via an electric power steering device. The actuators, control circuits, etc. that are responsible for such autonomous driving require a redundant system so that if one fails, the other can maintain its function.

[0017] For example, an electric power steering device may be configured with two motor units and two motor drive control circuit units that are redundant with respect to each other. In this case, one motor unit and its corresponding drive control circuit unit correspond to one of the automatic driving electric loads included in load A group 21, and the other motor unit and its corresponding drive control circuit unit correspond to the other automatic driving electric load included in load B group 22.

[0018] The power supply system of one embodiment includes two secondary batteries for temporarily storing power generated by the alternator 2. Specifically, the system includes a lead-acid battery 6, which corresponds to the first power storage device in the claims, and a lithium-ion battery 7, which corresponds to the second power storage device. The lead-acid battery 6 is a so-called 12V battery commonly used as an on-board battery in automobiles, and is a battery with an appropriate capacity taking into account the overall loads A group 21 and B group 22. The lithium-ion battery 7 is a type of backup power supply primarily used to secure power for the electric loads for automatic driving in the load B group 22. For example, a battery with a capacity relatively smaller than that of the lead-acid battery 6 is used. Generally, lithium-ion batteries have lower internal resistance and superior charge / discharge characteristics compared to lead-acid batteries. The lithium-ion battery 7 has a voltage equivalent to that of the lead-acid battery 6 by adjusting the number of cells.

[0019] The lead-acid battery 6 incorporates a current / voltage sensor 8 that detects the current and voltage of the lead-acid battery 6. This current / voltage sensor 8 detects the current and voltage during charging and discharging, and the state of charge (SOC) of the lead-acid battery 6 is estimated based on these data. The lithium-ion battery 7 incorporates a battery management system (BMS) 9 and an LiB relay 10 in a battery pack containing cells. The battery management system 9 detects the voltage and current of each cell, suppresses overcharging and overdischarging, equalizes cell voltages, calculates the state of charge (SOC), and performs other functions. It also detects cell temperature and monitors overcurrent, protecting the lithium-ion battery 7 by shutting off the LiB relay 10 in the event of, for example, an abnormally high temperature or an overcurrent. The LiB relay 10 is a contact relay and corresponds to the second disconnecting device in the claims.

[0020] The lead-acid battery 6 is connected to the alternator 2, starter motor 5, and load group A 21 as a main circuit 11. The lithium-ion battery 7 incorporating the LiB relay 10 is connected to load group B 22 as a backup circuit 12. The main circuit 11 and backup circuit 12 are connected to each other via a circuit breaker switch 13 (corresponding to the disconnecting device in the claims). The circuit breaker switch 13 is made of a semiconductor switch in consideration of responsiveness. As shown in FIG. 1 , the circuit breaker switch 13 is disposed between the lead-acid battery 6 for supplying power to the starter motor 5 and load group B 22, which is mainly composed of electrical loads for automatic driving.

[0021] The connection and disconnection of the circuit breaker switch 13 and the LiB relay 10 are controlled by a controller 14 that controls the power supply. The controller 14 also controls the voltage and power generation amount of the alternator 2, and further controls the starter motor 5 when starting the engine 1 (initial start and restart after idling stop). The controller 14 may be composed of multiple modules or controllers.

[0022] FIG. 2 is an explanatory diagram illustrating the basic operation of the power supply system of one embodiment shown in FIG. 1 . In the following explanatory diagrams, including FIG. 2 , arrows indicate the flow of main currents. FIG. 2(a) shows a state in which the vehicle ignition switch is OFF. In this ignition switch OFF state, the circuit breaker switch 13 is ON (conducting state), and the LiB relay 10 is controlled to OFF (disconnecting state). In this ignition switch OFF state, many electrical loads do not require power, but some electrical loads consume power even during standby, resulting in so-called standby current flowing through the circuit. As shown by the arrows in FIG. 2(a), the lead-acid battery 6 supplies the necessary power to both load group A 21 and load group B 22 during standby. Because the LiB relay 10 is in the disconnecting state, the charge level of the lithium-ion battery 7 does not decrease.

[0023] When the ignition switch is turned ON, as shown by the arrow in Fig. 2(b), power is supplied from the lead-acid battery 6 to the starter motor 5, and cranking and starting (initial starting) of the engine 1 is performed. During cranking, the LiB relay 10 remains OFF, and power from the lithium-ion battery 7 is not consumed.

[0024] When starting is complete, the LiB relay 10 is turned ON as shown in Figure 2(c). Therefore, as shown by the arrows, both the lead-acid battery 6 and the lithium-ion battery 7 are charged by power generation from the alternator 2. The voltage is controlled so that the charge of the lead-acid battery 6, which is reduced due to power consumption while the ignition switch is OFF and during cranking, and the charge of the lithium-ion battery 7, which is slightly reduced due to natural discharge, are quickly restored.

[0025] 2(d) shows a normal driving state in which the lead-acid battery 6 and the lithium-ion battery 7 are sufficiently charged. The circuit breaker switch 13 and the LiB relay 10 are both in the ON state. In this state, power is basically supplied from the alternator 2 to the load A group 21 and the load B group 22. If the lithium-ion battery 7 is sufficiently charged, the use of the automatic driving function is permitted. Furthermore, if the lead-acid battery 6 is sufficiently charged, idling stop control, which stops operation of the engine 1 when the vehicle is stopped at an intersection, is permitted.

[0026] When the vehicle stops from the control state of FIG. 2(d) and the ignition switch is turned off, the LiB relay 10 is turned off and the state returns to the state of FIG. 2(a).

[0027] Next, power supply control during idling stop control, which is a main part of the present invention, will be described with reference to the time chart of FIG. 3 and the operation explanatory diagram of FIG.

[0028] Idling stop control is an effective means for reducing fuel consumption of a vehicle, and is executed when several idling stop conditions are simultaneously met (so-called AND conditions), such as when the vehicle speed is approximately 0, after warm-up is complete, the accelerator pedal is OFF, the brake pedal is ON, and the charge amount of the lead-acid battery 6 or the lithium-ion battery 7 is equal to or greater than a predetermined level (LABSOC2, LiBSOC1, described later), and the engine 1 is automatically stopped. After that, automatic restart is performed when any one of several restart conditions is met (so-called OR conditions), such as when the brake pedal is OFF or a start request is received from the air conditioning system.

[0029] 4 is an explanatory diagram for explaining operation during idle stop control, and when the idle stop condition is met from the normal control state shown in FIG. 2(d) described above and idle stop control is initiated, the circuit breaker switch 13 is turned OFF as shown in FIG. 4(a). The LiB relay 10 remains in the ON state. During idle stop control, the engine 1 is stopped and power generation by the alternator 2 is stopped, so that power is supplied to the load group A 21 from the lead-acid battery 6 and to the load group B 22 from the lithium-ion battery 7. This ensures that power is reliably supplied to the two mutually redundant automatic driving electric loads included in the load group A 21 and the load group B 22, respectively.

[0030] It is preferable that the condition that the LiB relay 10 is actually ON be included as one of the idling stop conditions. In other words, it is desirable to prevent the idling stop control from being started in a state in which power supply from the lithium ion battery 7 to the load B group 22 is not possible.

[0031] Next, when the restart conditions are met and the vehicle is restarted, as shown in FIG. 4B , power is supplied from the lead-acid battery 6 to the starter motor 5, and cranking for the restart is performed. At this time, the circuit breaker switch 13 remains OFF, and the LiB relay 10 remains ON. Therefore, while power continues to be supplied from the lithium-ion battery 7 to the automatic driving electrical loads of the load group B 22, the lithium-ion battery 7 is disconnected from the starter motor 5 and the lead-acid battery 6, and no power is transferred from the lithium-ion battery 7 to the main circuit 11. In particular, because the lithium-ion battery 7 has a lower internal resistance than the lead-acid battery 6, if both the lead-acid battery 6 and the lithium-ion battery 7 were connected to the starter motor 5, power from the lithium-ion battery 7 would be consumed preferentially. Because the circuit breaker switch 13 is OFF, the lithium-ion battery 7 is not affected during the restart.

[0032] In the above embodiment, the circuit breaker switch 13 is turned OFF substantially simultaneously with the start of the idling stop control in preparation for restart. Therefore, there is no delay in switching the circuit breaker switch 13 OFF when a restart request is made, and restart can be started promptly. In addition, there is no concern about power being drawn from the lithium-ion battery 7 to the load A group 21 during the idling stop control.

[0033] In the present invention, the circuit breaker switch 13 may be turned off with a delay from the start of the idling stop control, as long as the circuit breaker switch 13 is in the cut-off state at least during cranking for restart.

[0034] FIG. 4C shows the control state immediately after restart. After restart, charging of the lead-acid battery 6 is prioritized. Therefore, the circuit breaker switch 13 remains OFF for a predetermined period after restart. The lead-acid battery 6 is charged by the power generated by the alternator 2. During this period, the load group B 22 receives power from the lithium-ion battery 7. By prioritizing charging of the lead-acid battery 6 with the circuit breaker switch 13 OFF, the charge state of the lead-acid battery 6, which has been significantly reduced by cranking during restart, is quickly restored. If the lithium-ion battery 7 is connected to the alternator 2 along with the lead-acid battery 6, charging of the lithium-ion battery 7 is also performed in parallel, slowing down the charging of the lead-acid battery 6. In particular, in the embodiment in which the lithium-ion battery 7 is combined with the lead-acid battery 6, the internal resistance of the lead-acid battery 6 is greater than that of the lithium-ion battery 7. This means that charging of the lithium-ion battery 7 proceeds relatively quickly, and charging of the lead-acid battery 6 tends to be slower. In the above embodiment, by prioritizing charging of the lead-acid battery 6 with the circuit breaker switch 13 turned off immediately after restarting, the charge state of the lead-acid battery 6 can be maintained at a level that allows restarting even if idling stop control is frequently repeated.

[0035] After the lead-acid battery 6 has been charged preferentially, the circuit breaker switch 13 is controlled to be ON, as shown in FIG. 4( d ), and the charging process shifts to charging both the lead-acid battery 6 and the lithium-ion battery 7 .

[0036] 3 is a time chart showing power supply control during idle stop control, and in this example, idle stop control is executed twice. The period marked "IS" in the top row (a) is the idle stop control period (corresponding to FIG. 4(a)), the period marked "LAB charging" is the priority charging period for the lead-acid battery 6 (corresponding to FIG. 4(c)), and the period marked "LiB+LAB charging" is the charging period for both the lithium-ion battery 7 and the lead-acid battery 6 (corresponding to FIG. 4(d)). As described above, after the end of idle stop control, the lead-acid battery 6 is prioritized for charging for a predetermined period, and then the system transitions to charging both the lithium-ion battery 7 and the lead-acid battery 6.

[0037] Column (b) shows the change in the state of charge (SOC) of the lead-acid battery 6 (abbreviated as LAB in the figure). LABSOC1 is the target SOC of the lead-acid battery 6 for terminating the priority charging of the lead-acid battery 6 after restart (corresponding to the first predetermined value in the claims). LABSOC2 is the idling stop prohibition SOC of the lead-acid battery 6, which is one of the idling stop conditions. LABSOC2 is set to a value lower than LABSOC1. When the state of charge (SOC) of the lead-acid battery 6 falls below LABSOC2, idling stop control is prohibited. Thereafter, idling stop control remains prohibited due to so-called hysteresis until the state of charge returns to LABSOC1. The state of charge of the lead-acid battery 6 decreases due to power consumption by the load A group 21 during idling stop control and cranking at restart, and then increases during the subsequent charging period. In the illustrated example, the priority charging period for the lead-acid battery 6 after the first idling stop control ends at time t3 when the charge amount of the lead-acid battery 6 reaches LABSOC1. In other words, it is considered that the predetermined period for priority charging of the lead-acid battery 6 has elapsed when the charge amount (SOC) of the lead-acid battery 6 reaches the charge target LABSOC1.

[0038] The first idling stop control ends at time t2 when, for example, the driver releases the brake pedal. The second idling stop control ends at time t5 when the charge amount of the lead-acid battery 6 drops to LABSOC2.

[0039] Column (c) shows the change in the state of charge (SOC) of the lithium-ion battery 7 (abbreviated as LiB in the figure). LiBSOC1 is the idling stop prohibition SOC below which idling stop control is prohibited. This LiBSOC1 is also the lower limit SOC (corresponding to the second predetermined value in the claims) at which the lithium-ion battery 7 should be charged. If the charge level of the lithium-ion battery 7 drops to LiBSOC1 while the lead-acid battery 6 is being preferentially charged after idling stop control, the system switches to charging both the lithium-ion battery 7 and the lead-acid battery 6. LiBSOC2 is the automatic driving warning SOC, which is the lower limit at which the power required for the automatic driving function can be output to the automatic driving electrical loads of the load group B 22. If the charge level of the lithium-ion battery 7 falls below this LiBSOC2 during automatic driving, an alert (audio, screen display, etc.) is issued to the driver urging them to switch from automatic driving to manual driving. LiBSOC1 is set to a value higher than LiBSOC2 so as to provide an appropriate margin of time before an alert is issued. The charge amount of the lithium-ion battery 7 decreases due to power consumption by the load group B 22 during the idle-stop control and the subsequent priority charging period of the lead-acid battery 6, and increases during the charging periods of both the lithium-ion battery 7 and the lead-acid battery 6. In the illustrated example, the priority charging period of the lead-acid battery 6 after the second idle-stop control ends at time t6 when the charge amount of the lithium-ion battery 7 has decreased to LiBSOC1. In other words, it is considered here that the predetermined period for priority charging of the lead-acid battery 6 has elapsed when the charge amount (SOC) of the lithium-ion battery 7 has decreased to LiBSOC1.

[0040] The predetermined period for preferentially charging the lead-acid battery 6 may be determined by its duration. In this case, the preferential charging of the lead-acid battery 6 ends after a certain period of time has elapsed, and the charging process shifts to charging both the lithium-ion battery 7 and the lead-acid battery 6. In particular, it is desirable to set an appropriate upper limit time for the preferential charging of the lead-acid battery 6 in order to avoid a situation in which the charging process does not shift to both the lithium-ion battery 7 and the lead-acid battery 6 due to some abnormality.

[0041] Column (d) indicates whether the alternator 2 (abbreviated as ALT in the drawing) is in a generating state (Generate) or a non-generating state (Not Generate). During idling stop control, power generation stops.

[0042] Column (e) shows the open / closed state of the circuit breaker switch 13 (abbreviated as HNS in the figure). The circuit breaker switch 13 is open (OFF) during idling stop control and during the period in which the lead-acid battery 6 is being preferentially charged, and is closed (ON) during the period in which both the lithium-ion battery 7 and the lead-acid battery 6 are being charged. Column (f) shows the open / closed state of the LiB relay 10. The LiB relay 10 remains closed (ON) during the period shown in the time chart.

[0043] In this way, in the above embodiment, the predetermined period for the priority charging of the lead-acid battery 6 is determined to have elapsed when any one of the following conditions is met: the charge amount of the lead-acid battery 6 has reached LABSOC1, the charge amount of the lithium-ion battery 7 has fallen to LiBSOC1, or the duration of the priority charging of the lead-acid battery 6 has reached a predetermined upper limit time. In the present invention, it is not necessary to rely on these three OR conditions, and any suitable single condition or combination of multiple conditions can be used.

[0044] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the lead-acid battery 6 is used as the first power storage device and the lithium-ion battery 7 is used as the second power storage device, but the power storage device may be of any type, such as an appropriate secondary battery or a capacitor.

[0045] In the above embodiment, the alternator 2 is simply a generator, and cranking is performed by the starter motor 5. However, cranking at start-up can also be performed by using a motor-generator that functions as a generator. Alternatively, a motor-generator that functions as a generator and a starter motor can be provided, and initial starting can be performed by the starter motor, and restarting after idling stop control can be performed by the motor-generator.

[0046] Furthermore, in the above embodiment, the electric load for automatic driving is divided into two redundant electric loads, but the present invention is not limited to such a redundant system and can be applied to other systems.

Claims

1. The engine, a generator driven by the engine to generate electricity; a first power storage device and a second power storage device that are respectively charged with the power generated by the generator and supply power required for the automatic driving of the vehicle to an automatic driving electrical load; A disconnecting device provided between the first power storage device and the second power storage device; Equipped with When a predetermined condition is satisfied while the vehicle is stopped, an idling stop control is executed to stop the engine. when the idling stop control is ended and the engine is restarted, cranking the engine using electric power from the first power storage device with the disconnecting device in a disconnected state; After the restart, for a predetermined period of time, the first power storage device is charged without charging the second power storage device while keeping the disconnecting device in a disconnected state, After the predetermined period has elapsed, the disconnecting device is brought into a conductive state to charge both the first power storage device and the second power storage device, The predetermined period is determined to have elapsed when the state of charge of the second power storage device has decreased to a second predetermined value, and the second predetermined value is set to a value higher than an automatic driving warning SOC that issues an alert to prompt switching to manual driving. How to control a vehicle.

2. The disconnecting device is brought into a disconnected state substantially simultaneously with the start of the idling stop control. The method for controlling a vehicle according to claim 1 .

3. (delete)

4. The predetermined period is determined to have elapsed when a charge state of the first power storage device reaches a first predetermined value. The method for controlling a vehicle according to claim 1 .

5. (delete)

6. The autonomous driving electric load includes a first electric load and a second electric load which mutually constitute a redundant system, When the disconnecting device is in a disconnected state, the first electrical load receives a supply of electric power from the first power storage device, and the second electrical load receives a supply of electric power from the second power storage device. The method for controlling a vehicle according to claim 1 .

7. a second disconnecting device provided between the second electric load and the second power storage device; The predetermined condition includes one condition that the second disconnecting device is in a conductive state. The method for controlling a vehicle according to claim 1 .

8. The engine, a generator driven by the engine to generate electricity; a first power storage device and a second power storage device that are charged with the power generated by the generator and supply power required for the automatic driving of the vehicle to an automatic driving electrical load; A disconnecting device provided between the first power storage device and the second power storage device; A controller; Equipped with The above controller is When a predetermined condition is satisfied while the vehicle is stopped, an idling stop control is executed to stop the engine. when the idling stop control is ended and the engine is restarted, cranking the engine using electric power from the first power storage device with the disconnecting device in a disconnected state; After the restart, for a predetermined period of time, the first power storage device is charged without charging the second power storage device while keeping the disconnecting device in a disconnected state, After the predetermined period has elapsed, the disconnecting device is brought into a conductive state to charge both the first power storage device and the second power storage device, The predetermined period is determined to have elapsed when the state of charge of the second power storage device has decreased to a second predetermined value, and the second predetermined value is set to a value higher than an automatic driving warning SOC that issues an alert to prompt switching to manual driving. Vehicle control device.