Vehicle control system

Abstract

To reduce wear of a friction brake of an own vehicle when the own vehicle travels on a downhill road following a preceding vehicle and a charge amount of a battery of the own vehicle is a predetermined value or more.SOLUTION: In the driving assist control ECU36, when the ACC is on, the ACC is performed to cause the own vehicle to travel following the preceding vehicle, and the downhill determination section 50 determines whether the own vehicle is traveling on a downhill. The grille shutter 54 is provided at a front face portion of the vehicle, and is capable of being displaced between an open position that allows travelling wind to flow in to a location where a friction brake of the vehicle is installed, and a closed position that blocks entry of the travelling wind. The opening / closing controller 52 displaces the grille shutter 54 to the open position when the ACC is performed in the driving assistance control ECU36, the downhill determining module 50 determines that the vehicle is traveling on a downhill road, and the SOC value of the battery of the vehicle is equal to or greater than the predetermined value in the driving assistance control region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to vehicle control systems. [Background technology]

[0002] Patent Document 1 discloses a technology in which, when traveling downhill using ACC (Adaptive Cruise Control), if the battery is not fully charged, the vehicle decelerates using regenerative braking, and if the battery is fully charged, the regenerative braking is stopped and the vehicle decelerates using friction braking (paragraphs "0053", "0054", Figure 8, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-51192 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in Patent Document 1 has the problem that when the regenerative brake is stopped and deceleration is performed using the friction brake, the temperature of the rotor of the friction brake and other components rises excessively, causing the brake pads of the friction brake and other components to wear out prematurely.

[0005] The present disclosure has been made in consideration of the above facts, and aims to provide a vehicle control system that can reduce wear on the friction brakes of a vehicle when the vehicle is following a preceding vehicle and traveling downhill and the charge level of the battery of the vehicle is equal to or greater than a predetermined value. [Means for solving the problem]

[0006] A vehicle control system according to a first aspect includes a follow-up control unit that performs follow-up control to cause the host vehicle to follow a preceding vehicle; a downhill road determination unit that determines whether the host vehicle is traveling on a downhill road; an opening / closing member that is provided on the front of the host vehicle and can be displaced to an open position that allows running wind to flow into a location where a friction brake is installed on the host vehicle or to a closed position that blocks the flow of running wind; and an opening / closing control unit that displaces the opening / closing member to the open position when follow-up control is performed by the follow-up control unit, the downhill road determination unit determines that the host vehicle is traveling on a downhill road, and the charge level of the battery of the host vehicle is equal to or greater than a predetermined value.

[0007] In a first aspect, an opening / closing member is provided on the front of the host vehicle, and is displaceable between an open position that allows airflow to flow into the portion of the host vehicle where the friction brake is installed and a closed position that blocks airflow from flowing into the portion of the host vehicle where the friction brake is installed. The opening / closing control unit displaces the opening / closing member to the open position when the following control unit performs following control to cause the host vehicle to travel by following a preceding vehicle, the downhill road determination unit determines that the host vehicle is traveling on a downhill road, and the charge level of the battery of the host vehicle is equal to or greater than a predetermined value. This makes it possible to suppress a rise in temperature of the rotor of the friction brake of the host vehicle and reduce wear on the brake pads of the friction brake of the host vehicle when the host vehicle is traveling on a downhill road following a preceding vehicle and the charge level of the battery of the host vehicle is equal to or greater than a predetermined value. [Effects of the Invention]

[0008] The present disclosure has the effect of reducing wear on the friction brakes of a vehicle when the vehicle is following a preceding vehicle on a downhill road and the charge level of the battery of the vehicle is equal to or greater than a predetermined value. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a schematic configuration of an in-vehicle system according to an embodiment; [Figure 2] 4 is a flowchart showing a vehicle control process executed by a vehicle control ECU. DETAILED DESCRIPTION OF THE INVENTION

[0010] An example of an embodiment of the present invention will be described in detail below with reference to the drawings. An in-vehicle system 10 shown in Fig. 1 includes a bus 12 to which multiple ECUs (Electronic Control Units) that perform different controls and various sensors are connected. Note that Fig. 1 shows only a part of the in-vehicle system 10. In the following, a vehicle equipped with the in-vehicle system 10 will be referred to as a host vehicle. The in-vehicle system 10 is an example of a vehicle control system according to the present disclosure.

[0011] A prime mover control ECU 16 is connected to the bus 12, and controls the driving force generated by a prime mover 14 mounted on the vehicle. In this embodiment, the prime mover 14 includes at least an MG (motor generator). That is, the prime mover 14 may be composed of an MG alone, or may be a hybrid system combining an MG with an internal combustion engine. Furthermore, the electric power supplied to the MG may be stored in a battery 26 (described later) mounted on the vehicle, or may be generated using fuel (e.g., fossil fuel or hydrogen) stored in a tank mounted on the vehicle. When the vehicle is decelerating and a State Of Charge (SOC) value indicating the state of charge of the battery 26 is equal to or greater than a predetermined value, the prime mover control ECU 16 causes the MG to generate electric power and charges the battery 26 with the electric power generated by the MG (regenerative electric power).

[0012] Also connected to the bus 12 are a braking control ECU 20, a steering control ECU 24, a battery management ECU 28, a group of surrounding condition acquisition devices 30, a group of driving state detection sensors 32, an ACC setting switch 34, a driving assistance control ECU 36, and a vehicle control ECU 38. The braking control ECU 20 controls the braking force generated by a friction brake device 18 mounted on the host vehicle, and the steering control ECU 24 controls the steering assistance force generated by a steering device 22 mounted on the host vehicle. The battery management ECU 28 detects and manages the temperature and SOC value of a battery 26 mounted on the host vehicle.

[0013] The surrounding condition acquisition device group 30 includes devices for acquiring information about the surrounding environment of the vehicle, such as a GNSS (Global Navigation Satellite System) device, a navigation system, a radar device, and a camera. The GNSS device receives GNSS signals from multiple GNSS satellites to determine the position of the vehicle. The navigation system displays the position of the vehicle on a map and provides guidance on a planned route to a destination based on the position information obtained from the GNSS device and map information previously stored in a storage unit. The radar device detects objects such as pedestrians and other vehicles around the vehicle and determines the relative position and speed of the detected objects and the vehicle. The camera captures images of the surroundings of the vehicle and outputs the captured images.

[0014] The driving condition detection sensor group 32 includes a steering angle sensor that detects the steering angle of the vehicle, a vehicle speed sensor that detects the driving speed of the vehicle, and an acceleration sensor that detects the acceleration applied to the vehicle, as multiple sensors that acquire the driving condition of the vehicle. The ACC setting switch 34 is a switch that can be set to switch the ACC on and off.

[0015] When the ACC is turned on via the ACC setting switch 34, the driving assistance control ECU 36 controls the driving of the host vehicle so that the detected value of the inter-vehicle distance or inter-vehicle time between the host vehicle and another vehicle (a preceding vehicle to be followed) traveling ahead in the traveling direction of the host vehicle corresponds to a preset specified value of the inter-vehicle distance or inter-vehicle time. Specifically, the driving assistance control ECU 36 controls the driving (acceleration / deceleration amount) of the host vehicle via the motor control ECU 16 and the braking control ECU 20 based on information obtained from the surrounding condition acquisition device group 30 and the traveling state detection sensor group 32 so that the detected value of the inter-vehicle distance or inter-vehicle time between the host vehicle and the preceding vehicle to be followed corresponds to the preset specified value of the inter-vehicle distance or inter-vehicle time. The driving assistance control ECU 36 is an example of a following control unit in the present disclosure.

[0016] The vehicle control ECU 38 includes a CPU (Central Processing Unit) 40, a memory 42 such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a storage 44 such as a HDD (Hard Disk Drive) or an SSD (Solid State Drive), and a communication I / F (Interface) 46. A vehicle control program 48 is stored in the storage 44, and the CPU 40 executes the vehicle control program 48 to function as a downhill road determination unit 50 and an opening / closing control unit 52, and to perform vehicle control processing, which will be described later.

[0017] The downhill road determination unit 50 determines whether the host vehicle is traveling on a downhill road. The opening / closing control unit 52 displaces a grille shutter 54 (described later) to an open position when the driving assistance control ECU 36 is performing ACC, the downhill road determination unit 50 determines that the host vehicle is traveling on a downhill road, and the SOC value of the host vehicle's battery 26 is equal to or greater than a predetermined value.

[0018] The vehicle is also provided with grille shutters 54 near both left and right ends of the front of the vehicle. The grille shutters 54 are movable between an open position that allows airflow to flow into the areas where the friction brakes on the front wheels of the vehicle are located, and a closed position that blocks airflow from flowing into the areas where the friction brakes are located. The grille shutters 54 are an example of an opening / closing member in the present disclosure. The vehicle is also provided with a grille shutter opening / closing actuator 56 that moves the grille shutters 54 between the open position and the closed position. The grille shutter opening / closing actuator 56 is connected to the bus 12.

[0019] Next, as an operation of this embodiment, a vehicle control process that is repeatedly executed by the vehicle control ECU 38 while the ignition switch of the host vehicle is on will be described with reference to Figure 2. In step 70 of the vehicle control process, the downhill road determination unit 50 estimates the road surface gradient of the road on which the host vehicle is traveling based on the detection value of the acceleration sensor, and determines whether the host vehicle is traveling on a downhill road from the estimated road surface gradient.

[0020] In step 72, the switching control unit 52 obtains the SOC value of the battery 26 from the battery management ECU 28. In step 74, the switching control unit 52 obtains information indicating the execution state of ACC from the driving assistance control ECU 36, and determines whether the current state of the host vehicle is that ACC is being executed, the host vehicle is traveling downhill, and the SOC value is equal to or greater than a predetermined value.

[0021] If the determination in step 72 is negative, regenerative braking due to power generation by the MG and friction braking by the friction brake device 18 are used in combination during vehicle deceleration in ACC, thereby suppressing a temperature rise in the rotor of the friction brake device 18. For this reason, if the determination in step 72 is negative, the process proceeds to step 80, where the opening / closing control unit 52 displaces the grille shutter 54 to the closed position using the grille shutter opening / closing ACT 56. This reduces the air resistance (running resistance) of the vehicle compared to when the grille shutter 54 is in the open position, improving power consumption or fuel economy. Furthermore, in the next step 82, the opening / closing control unit 52 sets a preset cooling coefficient for when the grille shutter is closed as the brake cooling coefficient bv.

[0022] On the other hand, if the determination in step 72 is positive, when the vehicle decelerates in ACC, no power is generated by the MG, regenerative braking is stopped, and braking is performed only by friction braking by the friction brake device 18, which causes a significant rise in the temperature of the rotor of the friction brake device 18. For this reason, if the determination in step 72 is positive, the process proceeds to step 76, where the opening / closing control unit 52 displaces the grille shutter 54 to the open position using the grille shutter opening / closing ACT 56. This allows airflow from the vehicle traveling toward the locations where the friction brakes are installed on the front wheels of the vehicle, thereby suppressing a rise in the temperature of the rotor of the friction brake device 18 and reducing wear on the brake pads of the friction brake device 18.

[0023] In the next step 78, the opening / closing control unit 52 sets a preset cooling coefficient when the grille shutter is open as the brake cooling coefficient bv. Note that the cooling coefficient when the grille shutter is open is greater than the cooling coefficient when the grille shutter is closed.

[0024] After the processing of step 82 or step 78 is performed, the process proceeds to step 64, where the opening / closing control unit 52 estimates the temperature T of the rotor of the friction brake device 18 using equations (1) and (2) described below.

[0025] The friction brake device 18 converts kinetic energy into thermal energy. If the heat capacity of the rotor (the weight of the sliding part of the rotor) is Wb (kg), the temperature change ΔT of the rotor is UP can be calculated using the following equation (1): 1 / 2×M×V 2 ×n=η×J×C×ΔT UP ×Wb×2 …(1) where M is the vehicle mass, V is the vehicle speed, n is the braking distribution, η is the heat loss coefficient, J is the thermal work equivalent, and C is the specific heat of the rotor. The rotor heat capacity Wb is the rotor temperature rise change ΔT when the vehicle is fully braked from its maximum speed (Vmax single braking). UP is set to be equal to or lower than a predetermined temperature (for example, 330°C).

[0026] The rotor also functions as a heat sink, and the cooling performance of the rotor significantly affects the fade resistance of the friction brake device 18. DOWN can be calculated using the following equation (2). ΔT DOWN = (rotor temperature - atmospheric temperature) × (1 - exp(-bv × t)) ... (2) However, the brake cooling coefficient bv = (H × A) / (Wb × C), where H is the heat transfer coefficient and A is the surface area of ​​the rotor's sliding part. The brake cooling coefficient bv improves (cools easier) when the heat transfer coefficient H and the surface area A of the rotor's sliding part are increased, but deteriorates (cools more difficult) when the heat capacity is increased.

[0027] In step 86, the opening / closing control unit 52 determines whether the rotor temperature T of the friction brake device 18 estimated in step 84 is less than a preset allowable temperature. If the determination in step 86 is affirmative, the process proceeds to step 88, where the opening / closing control unit 52 sets the friction brake control flag to a value indicating that the friction brake device 18 is to continue operating, and then ends the vehicle control process. If the determination in step 86 is negative, the process proceeds to step 90, where the opening / closing control unit 52 sets the friction brake control flag to a value indicating that the friction brake device 18 is to be deactivated, and then ends the vehicle control process.

[0028] The vehicle control ECU 38 controls the activation / deactivation of the friction brake device via the brake control ECU 20 according to the value of the friction brake control flag set in step 88 or step 90. However, when ACC is being executed, the vehicle is traveling downhill, and the SOC value is equal to or greater than a predetermined value, the grille shutter 54 is displaced to the open position to allow airflow toward the location where the friction brake is installed, thereby suppressing a temperature rise in the rotor and lengthening the time until the friction brake device 18 is switched to deactivation.

[0029] As described above, in this embodiment, the driving assistance control ECU 36 performs ACC to cause the host vehicle to follow a preceding vehicle when the ACC is on, the downhill road determination unit 50 determines whether the host vehicle is traveling downhill, and the grille shutter 54 is provided on the front of the host vehicle and is movable between an open position that allows traveling wind to flow into the portion of the host vehicle where the friction brake is installed and a closed position that blocks the flow of traveling wind. The opening / closing control unit 52 moves the grille shutter 54 to the open position when the driving assistance control ECU 36 performs ACC, the downhill road determination unit 50 determines that the host vehicle is traveling downhill, and the SOC value of the host vehicle's battery is equal to or greater than a predetermined value. This reduces wear on the friction brake of the host vehicle when the host vehicle is traveling downhill following a preceding vehicle and the charge level of the host vehicle's battery is equal to or greater than a predetermined value.

[0030] In the above embodiment, the friction brake device 18 is described as being configured as a disc brake, but the present disclosure is not limited to this, and the friction brake device 18 may also be configured as a drum brake. [Explanation of symbols]

[0031] 10 In-vehicle systems (vehicle control systems) 18 Friction brake device 20 Braking control ECU 26 Battery 36 Driving assistance control ECU (following control unit) 38 Vehicle Control ECU 50 Downhill road determination section 52 Opening and closing control section 54 Grill shutter (opening and closing member)

Claims

[Claim 1] a follow-up control unit that performs follow-up control to make the host vehicle follow a preceding vehicle; a downhill road determination unit that determines whether the host vehicle is traveling on a downhill road; an opening / closing member provided on a front portion of the vehicle and displaceable between an open position that allows airflow to flow into a portion of the vehicle where a friction brake is installed and a closed position that blocks the airflow from flowing into the portion of the vehicle where a friction brake is installed; an opening / closing control unit that displaces the opening / closing member to the open position when the following control unit is performing the following control, the downhill road determination unit determines that the vehicle is traveling on a downhill road, and the charge amount of the battery of the vehicle is equal to or greater than a predetermined value; A vehicle control system including:

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