JP7439628B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device for a vehicle such as a hybrid system or a mild hybrid system that automatically stops and starts an engine while the vehicle is running.

Hybrid systems and mild hybrid systems are based on internal combustion engine vehicles, but have been put into practical use in various forms due to their advantages in dramatically improving fuel efficiency, such as control that automatically stops and starts the engine while driving and regenerative braking. ing.

For example, Patent Document 1 discloses that the power supply circuit of a motor generator, starter, etc. that automatically starts the engine is shared with auxiliary electrical equipment, and equipment (protected load ) discloses a system that switches to another power source (auxiliary power source) during automatic startup.

By adopting such a system, it is possible to configure a mild hybrid system using only a low-voltage power supply circuit, and as disclosed in Patent Document 1, a high-voltage power supply circuit for a drive motor generator can be installed in parallel. A hybrid system can be constructed without using a DC-DC converter.

Japanese Patent Application Publication No. 2017-105377

By the way, in the above system, if it takes time to automatically start the engine while driving due to some abnormality, the protected load is operating under a high load with large power consumption, or the auxiliary battery (auxiliary power source) has deteriorated or If the capacity is reduced, the power of the auxiliary battery may become insufficient, leading to a voltage drop in the protected load.

As a workaround to this problem, consideration was given to carrying out the first automatic engine start at a low vehicle speed after the vehicle starts driving, and checking whether it can be started within the normal time required. However, this workaround did not allow the engine to stop at medium to high vehicle speeds until the startup was confirmed, and regenerated power decreased due to engine friction during deceleration, leaving issues with fuel efficiency.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to optimize automatic start control after automatic engine stop in vehicles equipped with a hybrid system or mild hybrid system, thereby further improving fuel efficiency. The aim is to realize this.

In order to solve the above problems, the present invention
internal combustion engine,
a motor generator having a function of generating electricity by rotating an output shaft of the engine and a function of automatically starting the engine;
The motor generator is connected to the motor generator and the general load, is connectable to the protected load, is charged with the electric power generated by the motor generator, and is capable of supplying power to the motor generator, the general load, and the protected load. main battery,
an auxiliary battery connectable to the motor generator and the protected load, charged with the power generated by the motor generator, and capable of supplying power to the protected load;
A control device for a vehicle, comprising:
When the engine is automatically started, the protected load is disconnected from the main battery and connected to the auxiliary battery, and after the engine is automatically started, the protected load is controlled to be reconnected to the main battery,
When the automatic start condition for the engine is satisfied and the vehicle speed is equal to or higher than a predetermined value, determining whether the outputtable power of the auxiliary battery can cover the power consumption of the protected load;
(a) If possible, automatically start the engine using the motor generator;
(b) The vehicle control device is configured to stop automatic starting of the engine by the motor/generator if the problem cannot be handled.

According to the control device according to the present invention, when the engine automatic start condition is satisfied and the vehicle speed is equal to or higher than a predetermined value, it is determined whether the outputtable power of the auxiliary battery can cover the power consumption of the protected load, If this is not possible, automatic engine starting by the motor generator will be stopped, so even if it takes time to automatically start the engine while driving due to some abnormality, voltage drop in the protected load can be avoided. The system can immediately switch to automatic engine stop control even at medium to high vehicle speeds, and further improvements in fuel efficiency can be expected.

1 is a system configuration diagram of a vehicle in which the present invention is implemented. FIG. 3 is an auxiliary power supply circuit diagram during engine operation. FIG. 2 is an auxiliary power supply circuit diagram at the time of automatic engine stop/start. FIG. 3 is an auxiliary power supply circuit diagram when automatic engine starting is malfunctioning according to an embodiment of the present invention. It is a flowchart which shows engine automatic stop control. 3 is a flowchart showing automatic engine start control according to an embodiment of the present invention. 5 is a time chart showing control when an engine automatic start malfunctions according to an embodiment of the present invention.

Embodiments of the present invention will be described in detail below with reference to the drawings.
In FIG. 1, a vehicle 1 is configured as a parallel hybrid vehicle in which an engine 2 and a drive motor 4 can transmit power to drive wheels 5 via a transmission 3, and serves as a control device to control a hybrid system. An HCU (Hybrid Control Unit) 10 that controls the engine 2 and auxiliary equipment, an ECU (Engine Control Unit) 20 that controls the engine 2 and auxiliary equipment, and a TCU (Transmission Control Unit) 30 that controls the transmission 3.

The engine 2 is, for example, a reciprocating internal combustion engine, and the ECU 20 performs engine control based on input signals from sensors that detect various state values that reflect the operating state of the engine 2.

For example, the ECU 20 detects the piston position and engine rotation speed based on input signals from a crank angle sensor and a cam angle sensor, and detects the piston position and engine rotation speed based on input signals from a crank angle sensor and a cam angle sensor, and detects an intake air amount sensor, an intake air temperature sensor, a water temperature sensor, an air-fuel ratio sensor, an accelerator opening sensor ( Optimizes engine operating conditions by determining fuel injection amount, fuel injection timing, ignition timing, and valve opening/closing timing based on detected values such as load demand) and outputting control signals to fuel injectors, spark plugs, etc. become

A starter 22 for cold starting is attached to the output side end (flywheel) of the crankshaft 21 that forms the output shaft of the engine 2, and a starter 22 is attached to the other end (pulley) of the crankshaft 21 via a belt. An ISG 23 capable of transmitting torque is attached.

The ISG (Integrated Starter Generator) 23 is a generator (motor generator, motor generator) with a starter function, is connected to the main battery 24 via the main power supply circuit 26, and is connected to the main battery 24 through the main power circuit 26. It has the function of a generator that charges the main battery 24 (and the auxiliary battery 25) with the power generated by the engine, and the function of a starter that starts the engine 2 with the power supplied from the main battery 24.

The output side end (flywheel) of the crankshaft 21 is connected to the input shaft 31 of the transmission 3 via a clutch 32 so as to be able to transmit torque. is blocked.

The transmission 3 is an automatic transmission (AT) equipped with a mechanism such as a gear or a belt between the input shaft 31 and the output shaft 34 to change the gear ratio, and can be of various types such as AMT, CVT, and planetary gear type. For example, it is configured as an AMT (Automated Manual Transmission) equipped with a constant-meshing transmission mechanism consisting of a parallel shaft gear mechanism, a shift actuator, and a clutch actuator (not shown), and the TCU 30 controls the shift actuator and clutch actuator to change speeds. It performs stage switching and disconnection from the engine 2.

The output shaft 34 of the transmission 3 has one end connected to the drive shaft 33 via a differential gear, and is capable of transmitting torque to the drive wheels 5. A driving motor 4 is connected to enable torque transmission.

A drive motor 4 (MGU; Motor Generator Unit) is connected to an inverter 41 and a drive battery 42 via a high voltage power supply circuit 43, and receives a high voltage power (MGU) supplied from the drive battery 42 according to a drive command from the HCU 10. For example, it is driven at 100 V), and also functions as a generator that performs regenerative power generation by rotating the drive shaft 33 (output shaft 34) and charges the drive battery 42 according to a regeneration command from the HCU 10.

The HCU 10, ECU 20, and TCU 30 include a CPU that performs arithmetic processing, a ROM that stores control programs and setting data, a RAM that reads control programs and setting data, and stores dynamic data and arithmetic processing results, and a communication I/F. The HCU 10 controls the hybrid system through cooperative control with the ECU 20 and the TCU 30.

With the above configuration, the vehicle 1 can run only by the engine torque generated by the engine 2, drive only by the motor torque generated by the drive motor 4 (EV running), and drive the drive motor 4 in power running mode. Driving in which the engine torque of the engine 2 is assisted (motor-assisted driving) is possible.

That is, the ECU 20 monitors vehicle information input through the in-vehicle network while the vehicle 1 is running, and when a predetermined engine stop condition is met, outputs a signal to automatically stop the engine 2 and When the motor 4 shifts to EV driving or regenerative braking (regenerative power generation) and predetermined automatic start conditions are met in those states or in a stopped state, a signal to automatically start the engine 2 is output to the ISG 23, and the engine 2 is activated. or motor-assisted driving using both the engine 2 and the drive motor 4.

By the way, as already mentioned, when automatically stopping/starting the engine, when the automatic stop preconditions are met before the engine is automatically stopped, the protected device cannot tolerate a voltage drop during driving of the ISG 23 (or starter 22). Control is performed to switch the power source of the load 7 from the main power source (main battery 24) to the auxiliary power source (auxiliary battery 25).

As shown in FIG. 1, the low voltage (for example, 12V) auxiliary power supply circuit includes a main power supply circuit 26 and an auxiliary power supply circuit 27. Low-voltage devices such as the starter 22 and the general load 6 are connected to the main power circuit 26, and power can be supplied to these devices from the main battery 24. The main battery 24 can be, for example, a lead battery. The general loads 6 include, among auxiliary equipment, equipment that can tolerate a voltage drop during driving, such as the ISG 23, and equipment that does not affect the driving performance of the vehicle 1, such as a blower of an air conditioner, a defogger, and the like.

An auxiliary power circuit 27 can be connected to the main power circuit 26 via the first switch SW1, and the protected load 7 is connected to the auxiliary power circuit 27, and an auxiliary battery 25 is connected to the main power circuit 26 via the second switch SW2. It is possible to connect to As the auxiliary battery 25, for example, a lithium ion battery (LiB) can be used.

With the above configuration, as shown in FIG. 2, when the first switch SW1 and the second switch SW2 are closed, the auxiliary battery 25 can be charged by the power generated by the ISG 23, and the protected load 7 is can be supplied. When the auxiliary battery 25 becomes fully charged (the charging rate SOC is equal to or higher than a predetermined value), the second switch SW2 is opened to prevent overcharging.

Further, as shown in FIG. 3, even if the first switch SW1 is open, if the second switch SW2 is closed, power can be supplied from the auxiliary battery 25 to the protected load 7. The protected load 7 includes auxiliary equipment such as starter 22 and ISG 23, which cannot tolerate a voltage drop during operation, and equipment that affects the driving performance of the vehicle 1, such as EPS (electric power steering), ESP, etc. (registered trademark; electronic stability program, vehicle behavior stability control system), navigation systems, and lights such as headlights and taillights.

FIG. 5 is a flowchart showing automatic engine stop control. The ECU 20 constantly monitors the state of the engine 2, and when the engine 2 is in operation (step 100), if a predetermined stop condition is satisfied (for example, If automatic stopping becomes possible due to a decrease in the driver's requested torque while the clutch 32 is connected and power running is performed (step 110), first, the protected load 7 is connected to the main power circuit 26 as described above. (ISG 23, main battery 24) and performs control to switch to the auxiliary power supply circuit 27 (auxiliary battery 25) (step 120).

Next, the ECU 20 acquires the connection/disengagement state of the clutch 32 from the TCU 30, and if the clutch 32 is in the engaged state, the ECU 20 gradually reduces the engine torque to 0 and then issues a command to the TCU 30 to release the clutch 32, thereby disengaging the clutch 32. At the same time, fuel injection is stopped to automatically stop the engine 2 (step 121).

FIG. 6 is a flowchart showing automatic engine start control. During automatic stop of the engine 2 (step 200), when a predetermined starting condition is satisfied (for example, during EV driving, the driver requested torque is set to a specified value). If the vehicle speed exceeds a predetermined value (step 210), first, it is checked whether the vehicle speed is equal to or higher than a predetermined value (step 212).

When the vehicle is running at a low speed less than a predetermined value, even if it becomes difficult to maintain the minimum voltage of the protected load 7, the vehicle can be stopped or evacuated, and the control continues.

On the other hand, if the vehicle speed is greater than or equal to the predetermined value, it is determined whether the outputtable power of the auxiliary battery 25 is greater than or equal to the power consumption of the protected load 7 (step 213).

In other words, the auxiliary battery is capable of maintaining the minimum voltage of the protected load 7 after the engine 2 starts until the protected load 7 is reconnected to the main battery 24 (main power circuit 26) (about 1 second). 25 is calculated from the temperature, charging rate, internal resistance (charging current, charging voltage), etc. of the auxiliary battery 25, and is compared with the current power consumption of the protected load 7.

In step 213, if the outputtable power of the auxiliary battery 25 is greater than or equal to the power consumption of the protected load 7, or if it is determined in step 212 that the vehicle speed is less than a predetermined value, the protected load 7 is connected to the main power supply circuit 26. (ISG 23, main battery 24) is checked (step 220), and if the disconnection is not completed such as when the engine is automatically stopped, disconnection from the main power circuit 26 is executed ( Step 221).

Next, as shown in FIG. 3, the ISG 23 is driven by the electric power supplied from the main battery 24, automatic starting of the engine 2 is executed (step 222), and it is determined whether the automatic starting of the engine 2 is completed. (step 230).

When the automatic start of the engine 2 is completed, the drive of the ISG 23 is stopped (step 231), and as shown in FIG. 2, the first switch SW1 is closed and the auxiliary power circuit 27 is connected to the main power circuit 26 ( In step 232), power is supplied from the main battery 24 to the protected load 7, and the auxiliary battery 25 is charged.

On the other hand, if the automatic start of the engine 2 is not completed in step 230, it is checked again whether the vehicle speed is equal to or higher than the predetermined value (step 212), and if the vehicle speed is less than the predetermined value, the engine 2 is started by the ISG 23. Continued.

Before that, if it is determined in step 212 that the vehicle speed is equal to or higher than a predetermined value, and it is determined in step 213 that the outputtable power of the auxiliary battery 25 is less than the power consumption of the protected load 7, that is, the protected load If it is determined that the power consumption of ISG 7 is greater than the outputtable power of auxiliary battery 25, driving of ISG 23 is stopped (step 214).

Furthermore, as shown in FIG. 4, the first switch SW1 is closed and the auxiliary power supply circuit 27 is connected to the main power supply circuit 26 (step 215). As a result, the power of the main battery 24 is supplied to the protected load 7, and the voltage of the protected load 7 can be maintained for a long time until the power of the main battery 24 is exhausted. Further, the auxiliary battery 25 is charged by the power of the main battery 24.

Thereafter, in step 212, if the vehicle speed decreases to a low vehicle speed below a predetermined value, or if in step 213, the power consumption of the protected load 7 decreases to less than the output power of the auxiliary battery 25, step 221 Then, the power source of the protected load 7 is switched to the auxiliary battery 25 again, and the engine 2 is restarted by driving the ISG 23.

Next, FIG. 7 is a time chart showing control when the engine automatic start is malfunctioning. The power consumption of the protected load 7 increases rapidly, and as a result, the engine automatic start condition is satisfied, and the engine is automatically started by driving the ISG 23. This assumes that the engine is starting. In the figure, the solid line indicates the control according to the embodiment of the present invention described above (FIG. 6), and the broken line indicates the control when steps 212, 213 to 215 are not included, as a comparative example.

In such a situation, for example, when the headlights are turned on with high beam and the ESP hydraulic pump is activated when driving on a low μ road such as a snowy road, at the same time, the driver needs to correct the steering wheel to prevent it from moving into a deep rut. When the EPS (Electric Power Steering) is activated, the electric power of the protected load increases, and the engine may not start for a short period of time due to some kind of failure or fuel shortage.

In this case, due to the high-load operation of the protected load 7, the outputtable power (charged amount) of the auxiliary battery 25 begins to decrease at (a) in the figure, and before the start is completed, the protected load starts to decrease at (b) in the figure. The power consumption will be lower than that of 7.

However, in the present invention, the drive of the ISG 23 is stopped at this point and the protected load 7 is reconnected to the main battery 24, so the power consumption of the auxiliary battery 25 and the voltage drop of the protected load 7 are corrected, and the main battery By being charged from the auxiliary battery 24, the outputtable power (charged amount) of the auxiliary battery 25 gradually recovers.

After that, in (d) of the figure, the power consumption of the protected load 7 has decreased to less than the output power of the auxiliary battery 25, so the power source of the protected load 7 is switched from the main battery 24 to the auxiliary battery 25, and the ISG 23 is switched from the main battery 24 to the auxiliary battery 25. The engine 2 is automatically started by the drive, and then the start of the engine 2 is completed, and at (f) in the figure, the drive of the ISG 23 is stopped, the protected load 7 is reconnected to the main battery 24, and the engine starts running. do.

On the other hand, in the comparative example shown by the broken line in the figure, since the control in steps 212, 213 to 215 is not included, the ISG 23 continues to be driven even in (b) in the figure, and the engine 2 is then started. , the outputtable power (charged amount) of the auxiliary battery 25 further decreases, and in (c) in the figure, it drops to the lowest operating voltage of the protected load (controller) 7, and the protected load (controller) 7 stops.

As described above, in the engine automatic start control according to the present invention, when the automatic start by the ISG 23 is prolonged, the start by the IGS 23 is interrupted, the protected load 7 is reconnected to the main battery 24, and the output of the auxiliary battery 25 is Since available power can be restored, the engine can be automatically started while avoiding any influence on the operation of the protected load 7.

In the above embodiment, a case has been described in which the hybrid vehicle is equipped with the drive motor 4 connected to the inverter 41 and the drive battery 42 via the high voltage power supply circuit 43, but the IGS 23 is not equipped with these. It can also be applied to mild hybrid vehicles that use assisted driving, regenerative braking, or creep driving.

Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and it is understood that various modifications and changes can be made based on the technical idea of the present invention. I would like to add.

1 Vehicle 2 Engine 3 Transmission 4 Drive motor 5 Drive wheel 6 General load 7 Protected load 10 HCU
20 ECUs
21 Crankshaft 22 Starter 23 ISG (motor generator)
24 Main battery 25 Auxiliary battery 26 Main power circuit 27 Auxiliary power circuit 30 TCU
32 Clutch 41 Inverter 42 Drive battery 43 High voltage power supply circuit SW1 First switch SW2 Second switch

Claims (8)

internal combustion engine,
a motor generator having a function of generating electricity by rotating an output shaft of the engine and a function of automatically starting the engine;
The motor generator is connected to the motor generator and the general load, is connectable to the protected load, is charged with the electric power generated by the motor generator, and is capable of supplying power to the motor generator, the general load, and the protected load. main battery,
an auxiliary battery connectable to the motor generator and the protected load, charged with the power generated by the motor generator, and capable of supplying power to the protected load;
A control device for a vehicle, comprising:
When the engine is automatically started, the protected load is disconnected from the main battery and connected to the auxiliary battery, and after the engine is automatically started, the protected load is controlled to be reconnected to the main battery,
When the automatic start condition for the engine is satisfied and the vehicle speed is equal to or higher than a predetermined value, determining whether the outputtable power of the auxiliary battery can cover the power consumption of the protected load;
(a) If possible, automatically start the engine using the motor generator;
(b) A vehicle control device configured to stop automatic starting of the engine by the motor/generator if the motor/generator cannot handle the situation. The vehicle control device according to claim 1 , configured to reconnect the protected load to the main battery after stopping automatic starting of the engine by the motor generator. After reconnecting the protected load to the main battery, if the power consumption of the protected load decreases below the output power that can be handled by the auxiliary battery or the vehicle speed decelerates below a predetermined value, the 3. The vehicle control device according to claim 2, wherein the device is configured to disconnect the protected load from the main battery, connect it to the auxiliary battery, and restart starting of the engine by the motor generator. Any one of claims 1 to 3, wherein the auxiliary battery and the protected load are connected when the auxiliary battery is disconnected from the motor generator in conjunction with the disconnection of the protected load from the main battery. 2. The vehicle control device according to item 1. 5. The auxiliary battery according to claim 1, wherein the auxiliary battery is configured to be disconnected from the main battery, the motor generator, and the protected load when fully charged even when the engine is operating. The vehicle control device according to any one of the items. The vehicle includes a main power circuit in which the motor generator and the general load are connected to the main battery, an auxiliary power circuit for connecting the protected load to the auxiliary battery, the main power circuit and the general load. a first switch for connecting/disconnecting the auxiliary power circuit; and a second switch for connecting/disconnecting the auxiliary power circuit between the first switch and the auxiliary battery; is connected when the engine is running, but is disconnected from automatic stop to automatic start of the engine, and the second switch is disconnected when the auxiliary battery is fully charged even when the engine is running. The vehicle control device according to any one of claims 1 to 5, wherein the controller is configured to be in a connected state when the first switch is disconnected. The vehicle includes a drive motor-generator capable of transmitting power to a drive shaft separately from the engine, and a high-voltage battery connected to the drive motor-generator via an inverter. The control device for a vehicle according to any one of claims 1 to 6, which is a hybrid vehicle capable of performing mechanical power running and regenerative braking. 7. The vehicle control device according to claim 1, wherein the vehicle is a mild hybrid vehicle capable of performing drive assist for the engine and regenerative braking by the motor/generator.