Vehicle control system

Abstract

The purpose is to reduce the impact when restarting the engine while the engine is under engine shutdown control in a vehicle in autonomous driving mode. [Solution] The vehicle control device comprises an engine which is an internal combustion engine, a rotating electric machine which is provided to start the engine, and an automatic driving mechanism which accelerates and decelerates the vehicle without the driver's will, and when the vehicle is in automatic driving by the automatic driving mechanism and the engine is being stopped, the control device detects that the rotational speed of the engine has fallen below a predetermined value, and then causes the rotating electric machine to output a torque that cancels out the shock torque generated in the crankshaft of the engine when the engine is started.

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle.

Background Art

[0002] Conventionally, there is known a control device for a vehicle that restarts the engine during engine stop control (see, for example, Patent Document 1). In Patent Document 1, when a restart request for the engine is made during the engine stop operation, if the rotational speed of the engine is within a predetermined range based on the resonance generation region of the drive device, the restart of the engine is suppressed, and if the rotational speed of the engine is outside the predetermined range, a start operation is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when restarting the engine during engine stop control, factors other than the relationship between the rotational speed of the engine and the resonance generation region of the drive device may cause impact. Therefore, even if the proposal of Patent Document 1 is applied, it is conceivable that an impact will occur with the restart of the engine during engine stop control. In addition, in the proposal of Patent Document 1, a case where the start operation of the engine itself is not performed is also assumed. In this case, for example, even when it is considered that the driver steps on the accelerator during engine stop control and the required output of the vehicle increases, it is assumed that the engine does not start and the desired accelerating force cannot be immediately obtained. Therefore, for example, when the required output of the vehicle is large, it is conceivable to prioritize the realization of a better accelerating force rather than shock reduction.

[0005] Incidentally, with the recent advancements in autonomous driving technology, there are cases where the engine is restarted while engine stop control is in place in a vehicle in autonomous driving mode. If the increase in the vehicle's required power output is due to autonomous driving control, even if impact reduction is prioritized over achieving good acceleration, the driver is unlikely to notice any discomfort with the vehicle's acceleration.

[0006] Conventional control devices, including the one proposed in Patent Document 1, do not consider restarting the engine during engine stop control in an automated driving state.

[0007] Therefore, the present invention aims to reduce the impact that occurs when the engine is restarted during engine stop control in a vehicle that is in an autonomous driving state. [Means for solving the problem]

[0008] The above objective is achieved by a vehicle control device comprising an engine which is an internal combustion engine, a rotating electric machine provided to start the engine, and an automatic driving mechanism that accelerates and decelerates the vehicle without the driver's will, wherein when the vehicle is in automatic driving by the automatic driving mechanism and the engine is being stopped, the requested output to the vehicle exceeds a predetermined value, and after detecting that the engine's rotational speed has fallen below a predetermined value, the vehicle control device causes the rotating electric machine to output a torque that cancels out the shock torque generated in the crankshaft of the engine when the engine is started. [Effects of the Invention]

[0009] In vehicles operating in autonomous driving mode, this technology can reduce the impact when restarting the engine during engine shutdown control. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram illustrating a hybrid vehicle to which the vehicle control device of the embodiment is applied. [Figure 2]Figure 2 is a schematic diagram of the engine configuration. [Figure 3] Figure 3 is a flowchart illustrating the processes performed by the vehicle control device of the embodiment. [Modes for carrying out the invention]

[0011] (Embodiment) The control device of the vehicle according to the embodiment will be described below with reference to the drawings.

[0012] [Configuration of Hybrid Vehicle] Figure 1 is a schematic diagram illustrating a hybrid electric vehicle (hereinafter simply referred to as "vehicle") 1. Vehicle 1 comprises an engine 10, a first motor generator (hereinafter referred to as the first MG) 61, a second motor generator (hereinafter referred to as the second MG) 62, a planetary gear mechanism 63, a transmission mechanism 64, and drive wheels 70. Vehicle 1 also comprises an HVECU (Hybrid Vehicle Electronic Control Unit) 20, an engine ECU 30, a PCU (Power Control Unit) 40, an autonomous driving ECU 50, a battery 80, and a battery ECU 81. Furthermore, Vehicle 1 comprises an object detection sensor 91, a vehicle speed sensor 92, a GPS receiver 93, a communication antenna 94, a navigation system 95, and a crank angle sensor 96.

[0013] The first MG61 and the second MG62 are rotating electric machines, each connected to the battery 80 via the PCU40, HVECU20, and battery ECU81. The first MG61 and the second MG62 function as motors that generate vehicle driving force in response to power supplied from the battery 80. Furthermore, the first MG61 and the second MG62 also function as generators that generate regenerative power to charge the battery 80 in response to power transmission from the engine 10 and drive wheels 70. The power exchanged between the first MG61 and the second MG62 and the battery 80 is regulated by the PCU40. The first MG61 also functions as a starter when starting the engine 10.

[0014] PCU40 is a power control device configured to control the input and output of power between the first MG61 and the second MG62 and the battery 80. Although not shown in the diagram, PCU40 includes an inverter, a boost converter, an SMR (System Main Relay), a motor ECU, and the like.

[0015] The planetary gear mechanism 63 mechanically connects the crankshaft of the engine 10, the rotating shaft of the first MG 61, the rotating shaft of the second MG 62, and the output shaft of the planetary gear mechanism 63. The planetary gear mechanism 63 includes a sun gear that rotates on its own axis, a ring gear that rotates coaxially with the sun gear, a pinion gear interposed between the sun gear and the ring gear and revolving around the sun gear, and a carrier that rotates coaxially with the sun gear in accordance with the revolution of the pinion gear. The carrier is connected to the crankshaft of the engine 10. The sun gear is connected to the rotating shaft of the first MG 61. The ring gear is linked to the rotating shaft of the second MG 62. The driving forces of the engine 10, the first MG 61, and the second MG 62 are transmitted to the drive wheels 70 via the transmission mechanism 64.

[0016] The engine 10 is controlled by the engine ECU 30. The engine ECU 30 controls the engine speed and engine torque by controlling the throttle actuator, fuel injection device, ignition device, etc., provided in the engine 10. Figure 2 is a schematic diagram of the engine 10 of this embodiment. The engine 10 is a gasoline engine having a plurality of cylinders 11, but is not limited to this and may be a diesel engine. Inside the cylinder 11, the piston 12 reciprocates in conjunction with the crankshaft 14. The tip of the spark plug 13 that ignites the air-fuel mixture is exposed in the combustion chamber 15 formed inside the cylinder 11. An intake pipe 21 and an exhaust pipe 22 are connected to the cylinder 11. The intake valve 31 opens and closes the connection between the intake pipe 21 and the cylinder 11. The exhaust valve 32 opens and closes the connection between the exhaust pipe 22 and the cylinder 11. The engine 10 can be started by the first MG 61 rotating the crankshaft 14. The crank angle sensor 96 can detect the rotational speed of the engine 10 by detecting the rotational angle of the crankshaft 14.

[0017] Vehicle 1 is equipped with an automatic driving mechanism that can accelerate and decelerate without relying on the driver's intention. The HVECU 20, the automatic driving ECU 50, the object detection sensor 91, the vehicle speed sensor 92, the GPS receiver 93, the communication antenna 94, and the navigation system 95 are included in the automatic driving mechanism.

[0018] The automatic driving ECU 50 is electrically connected to the object detection sensor 91. The object detection sensor 91 detects objects existing around the vehicle 1. Instead of the object detection sensor 91, or together with the object detection sensor 91, an in-vehicle camera may be electrically connected to the automatic driving ECU 50.

[0019] The HVECU 20 is electrically connected to the vehicle speed sensor 92, the GPS receiver 93, the communication antenna 94, and the navigation system 95. The HVECU 20 is also electrically connected to the above-mentioned object detection sensor 91. When an in-vehicle camera is installed in the vehicle 1, the HVECU 20 is also electrically connected to the in-vehicle camera. The vehicle speed sensor 92 detects the vehicle speed of the vehicle 1. The GPS receiver 93 receives radio waves transmitted by GPS (Global Positioning System) satellites and identifies the current position of the vehicle 1 on the ground surface or on a map based on the received radio waves.

[0020] The communication antenna 94 receives road traffic information transmitted from a road traffic information communication system installed outside the vehicle 1. The road traffic information includes, for example, information such as traffic jams, accidents, construction work, required passing times, and parking lots on the road. The navigation system 95 stores road map information such as road information and facility information. The road information includes information such as the types of roads, such as urban roads, suburban roads, mountain roads, and highways, road branches and merges, road gradients, speed limits, and traffic signal lights. The facility information includes information such as the types, locations, and names of bases such as supermarkets, shops, restaurants, parking lots, parks, and service areas.

[0021] The automatic driving ECU 50 calculates a vehicle required output required for traveling by automatic driving of the vehicle 1 based on object information. The automatic driving ECU 50 manages the calculated vehicle required output.

[0022] The HV ECU 20 switches the driving mode of the vehicle 1 to the motor driving mode or the hybrid driving mode. In the motor driving mode, traveling is performed with the second MG 62 as a power source while the engine 10 is stopped. In the hybrid driving mode, the engine 10 is driven and traveling is performed with the engine 10 as a power source. Even when at least one of the first MG 61 and the second MG 62 is used in combination with the engine 10, it is included in the hybrid driving mode.

[0023] The switching of the driving mode is performed based on the required torque to the hybrid vehicle 1 obtained from the vehicle speed and the accelerator opening. For example, when the required torque is less than the starting threshold for starting the engine 10, the motor driving mode in which the engine 10 is stopped is selected to improve fuel efficiency. When the required torque is greater than or equal to the starting threshold for starting the engine 10, the hybrid driving mode in which the engine 10 is started is selected.

[0024] When the vehicle 1 shifts from the hybrid driving mode to the motor driving mode, stop control of the engine 10 is performed. Here, during the stop control of the engine 10, a re-start of the engine may be required again. In this specification, such an engine start request will be referred to as an engine re-start request.

[0025] The driving mode of the vehicle 1 may be switched not only when the vehicle 1 is being driven by a driver but also when the vehicle 1 is in an automatic driving state. For this reason, even when the vehicle 1 is in an automatic driving state, an engine re-start request may be issued.

[0026] [Vehicle Control] Next, an example of the process executed by the vehicle control device of the present embodiment will be described.

[0027] Figure 3 is a flowchart illustrating the process performed by the vehicle control device of the embodiment. First, in step S1, the HVECU20 determines whether engine stop control is in progress and whether the vehicle request output is greater than a predetermined threshold. If the result in step S1 is positive (Yes), it means there is an engine restart request. The threshold is the value at which it is determined that the engine 10 needs to be running in order to obtain the vehicle request output. If the result in step S1 is Yes, the process proceeds to step S2. On the other hand, if the result in step S1 is negative (No), the process proceeds to step S9. In step S9, the engine restart is not performed.

[0028] Now, let's explain engine restart. Engine 10 will eventually reach a state where the rotation of the crankshaft 14 has stopped due to the stop control. Engine restart refers to starting engine 10 again before it is determined that the rotation of the crankshaft 14 has stopped. Note that, in contrast to this type of engine starting, starting engine 10 again after it has been determined that the rotation of the crankshaft 14 has stopped will be distinguished from engine restart and will simply be referred to as engine start. After step S9, the process ends.

[0029] In step S2, the HVECU20 determines whether vehicle 1 is in autonomous driving mode. If the determination in step S2 is Yes, the process proceeds to step S3. If the determination in step S2 is No, the process proceeds to step S7.

[0030] In step S3, the HVECU20 prohibits restarting the engine. That is, it prohibits restarting the engine 10 before it is determined that the rotation of the crankshaft 14 has stopped. After executing the process in step S3, the HVECU20 proceeds to step S4.

[0031] In step S4, the HVECU 20 determines whether the engine speed is 0 rpm or less based on the value detected by the crank angle sensor 96. This determines that the engine 10 has stopped because it has fallen below a predetermined value. In this embodiment, it is determined that the engine speed is 0 rpm or less, but any value other than 0 rpm may be set as long as it is a value that can be determined to indicate that the engine 10 has stopped. If the determination in step S4 is Yes, the process proceeds to step S5. If the determination in step S4 is No, the process ends.

[0032] In step S5, the HVECU20 starts the engine 10. The engine 10 in step S5 is not restarted, but started. In other words, the engine 10 is started from a state where it had been stopped. After executing the process in step S5, the HVECU20 proceeds to step S6.

[0033] In step S6, the HVECU20 performs shock reduction control. Shock reduction control causes the first MG61 to output a torque that cancels out the shock torque generated in the crankshaft 14 of the engine 10 when the engine 10 is started. This shock reduction control includes two types of control. The first is to control the torque output by the first MG61 so as to cancel out the torque generated in the crankshaft 14 when the first MG61 is used as a starter for the engine 10. In the engine 10, when the crankshaft 14 rotates and the piston 12 reciprocates within the cylinder 11, engine torque pulsation is generated as air is compressed within the cylinder 11. When the first MG61 rotates the crankshaft 14, a correction torque in the opposite phase to the engine torque pulsation is output to the first MG61 as a feedforward torque to cancel out the engine torque pulsation. This reduces the shock. Secondly, a correction torque, which is in the opposite phase to the initial engine combustion torque, is output to the first MG61 as a feedforward torque to counteract the initial engine combustion torque during engine startup. This reduces the shock. Through these two control mechanisms, the shock is reduced.

[0034] Furthermore, similar shock reduction control is also performed when the engine 10 is started under normal conditions. Here, "starting the engine 10 under normal conditions" refers to the state in which the engine 10 is started after it is determined that the effects of the previous engine operation have disappeared. In other words, immediately after the engine 10 stops, negative pressure remains in the cylinder 11, but the state in which this negative pressure condition has been resolved is considered to be the start of the engine 10 under normal conditions.

[0035] Thus, the negative pressure state in cylinder 11 differs between engine startup immediately after engine shutdown in autonomous driving and normal engine startup. Therefore, two correction torque values ​​are prepared: a correction torque value for autonomous driving and a correction torque value for normal engine startup. In the impact reduction control in step S6, the first MG61 is driven based on the correction torque value for autonomous driving, which takes into account the residual negative pressure in cylinder 11. This effectively reduces impact during autonomous driving.

[0036] HVECU20 terminates after executing the process in step S6.

[0037] In step S7, the HVECU20 restarts the engine. That is, it restarts the engine 10 again before it is determined that the rotation of the crankshaft 14 has stopped. After executing the process in step S7, the HVECU20 proceeds to step S8.

[0038] In step S8, the HVECU20 prohibits shock reduction control. When the engine is restarted, it is difficult to estimate engine torque pulsation, and consequently, it is difficult to define the corrective torque. Also, when the engine is restarted, the amount of air in cylinder 11 changes, and the initial combustion torque also changes, making it difficult to define an appropriate corrective torque. For these reasons, it is difficult to perform shock reduction control in step S8 as is done in step S6, and therefore shock reduction control is prohibited. The processing in steps S7 and S8 is performed when the driver is pressing the accelerator pedal with the intention to accelerate, rather than in autonomous driving. In this case, the priority is given to achieving good acceleration force rather than shock reduction.

[0039] HVECU20 terminates processing after executing the process in step S8.

[0040] [Effect] In the embodiment, when the vehicle 1 is in automatic driving mode by the automatic driving mechanism and the engine 10 is under stop control, if the requested output to the vehicle 1 exceeds a predetermined value, the control device detects that the rotational speed of the engine 10 has fallen below a predetermined value, and then causes the first MG61 to output a torque that cancels out the shock torque generated in the crankshaft 14 when the engine 10 is started. This reduces the shock when the engine 10 is restarted during engine stop control.

[0041] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0042] 1...Hybrid vehicle, 10...Engine, 11...Cylinder, 12...Piston, 13...Spark plug, 14...Crankshaft, 15...Combustion chamber, 20...HVECU, 21...Intake pipe, 22...Exhaust pipe, 30...Engine ECU, 31...Intake valve, 32...Exhaust valve, 40...PCU, 50...Autonomous driving ECU, 61...First MG, 62...Second MG, 63...Planetary gear mechanism, 64...Transmission mechanism, 70...Drive wheel, 80...Battery, 81...Battery ECU, 96...Crank angle sensor

Claims

[Claim 1] A control device for a vehicle comprising an internal combustion engine, a rotating electric machine capable of starting the engine, and an automatic driving mechanism that accelerates and decelerates the vehicle independently of the driver's will, The control device, when the vehicle is in automatic driving mode by the automatic driving mechanism and the engine is being stopped, will, if the requested output to the vehicle exceeds a predetermined value, After detecting that the rotational speed of the engine falls below a predetermined value, the rotating electric machine is instructed to output a torque that counteracts the shock torque generated in the crankshaft of the engine when the engine is started. Vehicle control system.

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