Vehicle control system

Abstract

Provided is a vehicle control system capable of achieving an improvement in NV performance (Noise Vibe performance) while suppressing a deterioration in fuel efficiency or electric power efficiency with respect to a stop maintaining function of a vehicle. The vehicle control system of the present invention is a vehicle control system in a vehicle having an engine or a motor as a drive source of a wheel in the vehicle, and includes a target drive force calculation section, a calculation section, and a stop maintaining processing section. The calculation section performs, before a parking time, a pre-pressurization process of pre-pressurizing brake hydraulic pressure and setting a cancellation portion drive force that cancels a brake force for pre-pressurization as a required drive force, and controls the required brake force in the pre-pressurization process in such a manner that an increase in the brake force for pre-pressurization is performed within a range not exceeding a brake force threshold value that is a value smaller than a stop maintaining brake force.

Description

Technical Field

[0001] This invention relates to a vehicle control system in a vehicle having a stop-hold function for keeping the vehicle stopped, and particularly to the technical field related to the control of brake hydraulic pressure before stopping. Background Technology

[0002] Vehicles with a stop-and-hold function that keeps a stopped vehicle stationary are known. Such a stop-and-hold function works, for example, when parking based on a vehicle speed control function that follows the vehicle ahead, such as ACC (Adaptive Cruise Control: cruise control with distance control), or when parking based on a one-pedal function (a function that accelerates or decelerates the vehicle based on the operation of one pedal).

[0003] Due to limitations in the mechanism for maintaining brake hydraulic pressure, the stop-hold function sometimes requires a higher brake hydraulic pressure than is needed for stopping. In some cases, the hydraulic pressure is increased from the pressure required for stopping to enable the stop-hold function.

[0004] It should be noted that, regarding the relevant prior art, the following patent documents 1-3 can be cited.

[0005] Patent Document 1 discloses a hill-start stop control device for an electric vehicle that can reduce the power consumption of the electric motor when the electric vehicle is stopped on a hill while generating the driving torque of the electric motor.

[0006] Patent document 2 discloses a technique for calculating the driving force used to counteract the remaining braking force in the control of braking force used to keep the vehicle in a stopped state.

[0007] Patent document 3 discloses a technique for suppressing operating noise and / or power consumption generated in the working fluid supply unit during the hydraulic holding action of the brake working fluid in a braking control system.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2003-182404

[0011] Patent Document 2: Japanese Patent Application Publication No. 2010-280239

[0012] Patent Document 3: Japanese Patent Application Publication No. 2017-177870 Summary of the Invention

[0013] Technical issues

[0014] In recent years, electronically controlled (Electrically controlled) boosters have become the mainstream brake boosters, replacing the traditional negative pressure boosters. However, when using an electronically controlled booster to increase the brake fluid pressure during parking as described above, it may generate motor noise and / or vibration, causing discomfort to the user.

[0015] In order to mitigate the discomfort caused by the noise and / or vibration of the motor operating during such stop-and-hold operation, consideration is given to pre-pressurizing the brake hydraulic pressure in the stage just before stopping, thereby reducing the amount of hydraulic pressure boosted based on the stop-and-hold function.

[0016] However, when performing such hydraulic pre-pressurization before parking, a driving force is required to counteract the pre-pressurization portion of the hydraulic system. To completely prevent motor noise and / or vibration during stop holding, the pre-pressurization hydraulic pressure needs to be increased accordingly. However, this increases the driving force used to counteract the pre-pressurization, resulting in decreased fuel efficiency or electrical efficiency.

[0017] The present invention was made in view of the above-mentioned problems, and its object is to improve NV performance (Noise and Vibration performance) while suppressing the deterioration of fuel efficiency or electric efficiency in the vehicle's stop-and-hold function.

[0018] Technical solution

[0019] The vehicle control system of the present invention, as a vehicle control system in a vehicle, has an engine or motor as the drive source for the wheels of the vehicle, and includes: a target driving force calculation unit that calculates the target driving force of the vehicle; an arithmetic unit that calculates, based on the target driving force, a required driving force for drive control of the engine or motor and a required braking force for hydraulic braking control; and a stop-and-hold processing unit that, when the required braking force at the time of stopping (i.e., the braking force at the time of stopping is not greater than or equal to the stop-and-hold braking force that is sufficient to keep the vehicle in a stopped state), performs a process of pressurizing the brake hydraulic fluid to make the braking force greater than or equal to the stop-and-hold braking force to keep the vehicle in a stopped state. Before the time of stopping, the arithmetic unit performs a pre-pressurization process that pre-pressurizes the brake hydraulic fluid and sets the driving force that offsets the braking force used for pre-pressurization as the required driving force. In the pre-pressurization process, the required braking force is controlled such that the increase in the braking force used for pre-pressurization does not exceed a braking force threshold value that is smaller than the stop-and-hold braking force.

[0020] By performing the pre-boosting process described above, it is possible to reduce the amount of hydraulic boost after stopping based on the stop-and-hold function, and to improve NV performance (Noise Vibration Performance). In this pre-boosting process, the braking force not used for pre-boosting rises to the stop-and-hold braking force, but stops rising to a braking force lower than the stop-and-hold braking force. Therefore, it is possible to prevent excessive increase in the driving force used for counteracting this, and to suppress deterioration in fuel efficiency or electrical efficiency.

[0021] In the vehicle control system of the present invention described above, the calculation unit can be configured to control the required braking force so that the increase of the braking force for the pre-boost is within a range where the offset driving force does not exceed a predetermined upper limit of the offset driving force.

[0022] Therefore, it is possible to ensure that the offset driving force does not exceed the upper limit of driving force allowed from the perspective of fuel efficiency or electric efficiency.

[0023] In the vehicle control system of the present invention described above, it is possible to configure a first mode that prioritizes passenger comfort and a second mode that prioritizes fuel efficiency or electric efficiency as a mode related to the control of the vehicle. When the second mode is set, the calculation unit reduces the upper limit of the offset driving force compared to the case where the first mode is set.

[0024] Thus, in the second mode, which prioritizes fuel efficiency and / or electrical efficiency, the upper limit of the offset driving force can be reduced to suppress the rise of the offset driving force. Conversely, in the first mode, which prioritizes occupant comfort, the upper limit of the offset driving force can be increased, i.e., the pre-boost amount can be increased to suppress the hydraulic boost amount during stop holding.

[0025] In the vehicle control system of the present invention described above, the calculation unit can be configured to calculate the braking force threshold as a value obtained by subtracting the allowable braking force after stopping from the stop-holding braking force.

[0026] The permissible increase in braking force after stopping refers to the permissible increase in braking force when the vehicle is stopped and held.

[0027] In the vehicle control system of the present invention described above, the arithmetic unit can be configured to increase the allowable braking force for rising after stopping when the slope of the vehicle's driving road is large, compared to when the slope is small.

[0028] When driving on a steep incline, a large value is set as the stopping and holding braking force. However, if the stopping and holding braking force increases without increasing the allowable braking force after stopping, the braking force threshold calculated based on "stopping and holding braking force - allowable braking force after stopping" will increase. This would increase the amount of driving force needed to offset the increase in braking force, potentially leading to increased fuel or electricity consumption to offset the pre-boost. Therefore, in situations with steep inclines as described above, the allowable braking force after stopping is increased to prevent the braking force threshold from becoming excessive.

[0029] In the vehicle control system of the present invention described above, the vehicle can be configured as a hybrid vehicle having an engine and a motor as the drive source for the wheels, and can be configured to operate the engine to drive the wheels in an engine driving mode and to stop the engine and drive the wheels by the motor in an EV driving mode. In the pre-boosting process, the calculation unit reduces the braking force threshold when in the engine driving mode compared to when in the EV driving mode.

[0030] In engine driving mode, the sound of the motor operating during hydraulic boost when the vehicle is stopped is difficult for occupants to perceive due to the engine noise. Therefore, in engine driving mode as described above, the braking force threshold is reduced, and the offset driving force during pre-boost is also reduced.

[0031] Invention Effects

[0032] According to the present invention, the stop-and-hold function of a vehicle can improve NV performance (Noise Vibe performance) while seeking to suppress the deterioration of fuel efficiency or electric efficiency. Attached Figure Description

[0033] Figure 1 A block diagram illustrating the general structure of a vehicle control system as an embodiment of the present invention.

[0034] Figure 2 This is an illustration of the stop-and-hold function.

[0035] Figure 3 This is a functional block diagram used to explain the pre-boosting process as an implementation method.

[0036] Figure 4 This is a diagram used to illustrate the overview of the pre-boosting process.

[0037] Figure 5 This is an explanatory diagram regarding the braking force threshold in the implementation method.

[0038] Figure 6This is an explanatory diagram of the upper limit of the offsetting driving force in the implementation method.

[0039] Figure 7 This is an explanatory diagram illustrating an example of the allowable braking force for ascent after stopping, corresponding to the slope.

[0040] Figure 8 This diagram illustrates the function of variable control of the braking force allowed for ascent after stopping, corresponding to the gradient.

[0041] Figure 9 The diagram illustrates the relationship between the upper limit of the offset driving force set in the second mode (ECO mode) and the upper limit of the offset driving force set in the first mode (COMFORT mode).

[0042] Figure 10 This diagram illustrates the effect of setting a limit on the offsetting driving force for different modes, namely the first and second modes.

[0043] Figure 11 The following diagram illustrates the relationship between the braking force thresholds set in engine driving mode and EV driving mode.

[0044] Figure 12 A flowchart illustrating a specific processing sequence example for implementing the pre-boosting process as an implementation method.

[0045] Figure 13 To and Figure 12 Together, a flowchart is shown as an example of a specific processing sequence for implementing the pre-boosting process as an implementation method.

[0046] Symbol Explanation

[0047] 1: Vehicle Control System

[0048] 2: Driver Assist Control Unit

[0049] 21: Filming Department

[0050] 22: Image Processing Department

[0051] 23: Control Department

[0052] 3: HEV control unit

[0053] 4: Engine Control Unit

[0054] 5: Motor control unit

[0055] 6: Driving Stability Control Unit

[0056] 7: Engine-associated actuator

[0057] 8: Motor drive unit

[0058] 9: Brake-related actuator

[0059] 10: MG (Electric Generator)

[0060] 11: Sensors / Operating Elements

[0061] 11a: Vehicle speed sensor

[0062] 11b: Accelerator opening sensor

[0063] 11c: Brake switch

[0064] 11d: Motion sensor

[0065] 12: Bus

[0066] F1: Target Driving Force Calculation Unit

[0067] F2: Driving Mode Selection Unit

[0068] F3: Arithmetic Unit

[0069] Tp: Stop maintaining braking force

[0070] Nth, Nth1, Nth2, Nth_eg, Nth_mt: NV braking force threshold

[0071] Um, Um1, Um2, Um_eg, Um_mt: Allowable braking force for ascent after stopping.

[0072] Dth, Dth_E, Dth_C: These offset part of the upper limit of the driving force.

[0073] U, Uc, Ue: Increase in braking force Detailed Implementation

[0074] <1. Composition of Vehicle Control System>

[0075] Figure 1 This is a block diagram illustrating the general structure of a vehicle control system 1, which is an embodiment of the present invention. It should be noted that... Figure 1 In this paper, only the main components of the vehicle control system 1 that are relevant to the present invention are shown.

[0076] The vehicle control system 1 of the embodiment is provided in a hybrid electric vehicle (H EV) that has an engine and an electric generator (hereinafter referred to as MG10) as the drive source for the wheels.

[0077] like Figure 1As shown, the vehicle control system 1 includes: a driver assistance control unit 2, an HEV control unit 3, an engine control unit 4, a motor control unit 5, a driving stability control unit 6, an engine-related actuator 7, a motor drive unit 8, a brake-related actuator 9, an MG (electric generator) 10, a sensor / operating element class 11, and a bus 12.

[0078] The driving assistance control unit 2 includes a camera unit 21, an image processing unit 22, and a control unit 23, and performs various control processes for driving assistance (hereinafter referred to as "driving assistance control processes").

[0079] The imaging unit 21 acquires image data by photographing the direction of travel of the vehicle (forward in this example). In this example, the imaging unit 21 has two camera units, each equipped with a camera optical system and an imaging element such as a CCD (Charge-Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor). In each camera unit, the camera optical system images the subject on the imaging surface of the imaging element, and obtains an electrical signal corresponding to the amount of light received in pixels. Each camera unit is configured to perform distance measurement using a so-called stereoscopic imaging method. The electrical signals obtained by each camera unit are subjected to A / D (Analog / Digital) conversion and / or predetermined correction processing, and supplied to the image processing unit 22 as a digital image signal (image data) representing a predetermined grayscale value in pixels.

[0080] The image processing unit 22 is configured to have a microcomputer or DSP (Digital Signal Processor) equipped with, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and to perform predetermined image processing related to the recognition of the vehicle's external environment based on the captured image data obtained by the imaging unit 21.

[0081] Specifically, the image processing unit 22 performs various image processing operations based on the image data obtained through stereoscopic imaging, and identifies information such as three-dimensional object data and / or white line data in front of the vehicle, and infers the vehicle's driving path based on this identified information. Furthermore, the image processing unit 22 detects vehicles traveling ahead on the vehicle's driving path based on the identified three-dimensional object data, etc.

[0082] Specifically, as a process for processing the image data captured in stereoscopic photography, the image processing unit 22 performs the following processing: First, for each pair of camera images, distance information is generated based on the offset (parallax) of the corresponding position using the principle of triangulation. Then, the distance information is subjected to known grouping processing, and the distance information obtained from the grouping processing is compared with pre-stored three-dimensional road shape data and / or three-dimensional object data to extract white line data, sidewall data such as guardrails and curbs existing along the road, and three-dimensional object data such as vehicles. Further, the image processing unit 22 estimates the vehicle's travel path based on the white line data and / or sidewall data, and extracts (detects) three-dimensional objects existing on the vehicle's travel path that are moving at a predetermined speed (e.g., 0 km / h or more) in approximately the same direction as the vehicle. Then, when a vehicle ahead is detected, the following information about the vehicle ahead is calculated: the inter-vehicle distance cd (= the inter-vehicle distance between the vehicle and itself), the relative speed ds (= the rate of change of the inter-vehicle distance cd), the speed of the vehicle ahead ss (relative speed ds + current vehicle speed js), and the acceleration of the vehicle ahead sac (= the derivative of the speed of the vehicle ahead ss). It should be noted that the current vehicle speed js is the vehicle speed detected by the vehicle speed sensor 11a (described later, relative to the set vehicle speed St, which can be referred to as the "actual vehicle speed"). Furthermore, the image processing unit 22 identifies vehicles that are moving forward, especially those with a speed of ss below a predetermined value (e.g., below 4 km / h) and not accelerating, as vehicles that are in a state of near-stopping motion.

[0083] The image processing unit 22 calculates the aforementioned forward vehicle information for each frame of, for example, captured image data, and stores the calculated forward vehicle information sequentially.

[0084] The control unit 23 is configured to have a microcomputer equipped with, for example, a CPU, ROM, RAM, etc., and performs driving assistance control processing based on the results of image processing performed by the image processing unit 22, detection information obtained by the sensor / operation element class 11, operation input information, etc.

[0085] Here, the control unit 23 is connected via bus 12 to the HEV control unit 3, engine control unit 4, motor control unit 5, and driving stability control unit 6, which are also configured with microcomputers, and is capable of data communication with these control units. The control unit 23 instructs the necessary control units among the aforementioned control units to perform driving assistance-related actions.

[0086] As one of the driver assistance control processes, the control unit 23 performs adaptive cruise control. That is, it controls the speed of the vehicle in a manner that meets specified driving conditions. In particular, in this example, the control unit 23 performs processing for implementing ACC (Adaptive Cruise Control) as adaptive cruise control.

[0087] In ACC, the target vehicle speed St and target inter-vehicle distance Dt are set based on the operation input made using a predetermined operating element set in the sensor / operating element class 11. It should be noted that in this example, the driver can select any inter-vehicle distance mode from three inter-vehicle distance modes, such as "long", "medium" and "short", through operation, and the control unit 23 sets a different target inter-vehicle distance Dt for each selected mode, for example, according to the vehicle speed js.

[0088] It should be noted that, in the following text, "target speed St" will be referred to as "set speed St".

[0089] In ACC, if no vehicle ahead is detected, the control unit 23 performs constant speed driving control to bring the vehicle speed js to a set vehicle speed St.

[0090] Furthermore, when the control unit 23 detects a vehicle ahead during constant speed driving control, it performs follow-driving control to converge the inter-vehicle distance cd between itself and the vehicle ahead to a target inter-vehicle distance Dt. As such follow-driving control, in this example, the control unit 23 performs control to stop and start following the vehicle ahead. That is, it stops the vehicle when the vehicle ahead stops, and then continues to follow the vehicle ahead when it starts moving again.

[0091] The control unit 23 calculates the target driving force in the ACC to achieve the constant speed driving control and following driving control as described above.

[0092] In addition, in states other than ACC (states where the vehicle's acceleration and / or deceleration are controlled based on the driver's acceleration and / or braking operations), the control unit 23 calculates the target driving force based on the driver's acceleration and / or braking operations.

[0093] Here, regarding the target driving force, for example, it is calculated as a positive value if it is on the acceleration side and a negative value if it is on the deceleration side, etc., and values ​​with different polarities are calculated on the acceleration side and the deceleration side.

[0094] In this example, the control unit 23 calculates the required driving force and the required braking force based on the calculated target driving force. The required driving force is the driving force of the vehicle required to achieve the target driving force. In the case of this example vehicle, which has an engine and MG10 as the driving source for the wheels, it is calculated as the combined driving force of the engine and MG10.

[0095] The required braking force is the braking force required to achieve the target driving force.

[0096] Here, in the case of HEV, in addition to hydraulic braking mechanisms such as disc brakes, there is also a regenerative brake utilizing the MG10 as the vehicle's braking unit. Therefore, when the vehicle decelerates, not only is the required braking force calculated, but the required driving force is also calculated to achieve a deceleration state corresponding to the calculated target driving force.

[0097] Furthermore, in this example, the control unit 23 can be set to a COMFORT mode that prioritizes occupant comfort and an ECO mode that prioritizes fuel efficiency and / or electrical efficiency, as a mode related to vehicle control. In this example, the control unit 23 sets these COMFORT and ECO modes based on the occupant's input.

[0098] Furthermore, in this example, the control unit 23 performs a pre-boosting process for the brake hydraulic pressure generated by the stop-hold function described later as a process to suppress the deterioration of fuel efficiency and / or electrical efficiency while seeking to improve NV performance (Noise Vibe performance), but this will be explained later.

[0099] The sensor / operating element class 11 comprehensively represents various sensors and / or operating elements installed in this vehicle. Sensors included in the sensor / operating element class 11 include a speed sensor 11a that detects the vehicle's speed as the vehicle speed js, an accelerator opening sensor 11b that detects the accelerator opening based on the amount of accelerator pedal depressed, a brake switch 11c that opens / closes based on the operation / non-operation of the brake pedal, and an action sensor 11d that has, for example, an acceleration sensor and / or an angular velocity sensor and detects the vehicle's movement.

[0100] In addition, although the illustration is omitted, the sensor / operating element class 11, as other sensors, also includes: an engine speed sensor for detecting engine speed, an intake air volume sensor for detecting the amount of air entering the engine, a throttle valve opening sensor for detecting the opening of a throttle valve that is clamped in the intake passage and adjusts the amount of air supplied to each cylinder of the engine, a coolant temperature sensor for detecting coolant temperature indicating engine temperature, an outside air temperature sensor for detecting outside air temperature, and a slope sensor for detecting the gradient of the road on which the vehicle is traveling.

[0101] In addition, as operating elements, there are start switches for indicating the start / stop of the vehicle control system 1, and operating elements for performing the aforementioned ACC-related operations. Furthermore, as operating elements, there are also operating elements for setting the aforementioned COMFORT mode and ECO mode.

[0102] The HEV control unit 3 controls the vehicle's actions by issuing instructions to the engine control unit 4 and the motor control unit 5 based on the required driving force calculated by the control unit 23 in the driver assistance control unit 2.

[0103] Based on the required driving force input from the control unit 23, the HEV control unit 3 calculates the required driving force of the engine (i.e., the required driving force of the engine) and the required driving force of the MG10 (i.e., the required driving force of the motor), and respectively instructs the required driving force of the engine to the engine control unit 4 and the required driving force of the motor to the motor control unit 5.

[0104] The engine control unit 4 controls various actuators installed as engine-associated actuators 7 based on the engine-required driving force indicated by the HEV control unit 3. The engine-associated actuator 7 includes various actuators related to engine drive, such as a throttle valve actuator that drives the throttle valve and / or an injector that performs fuel injection.

[0105] The engine control unit 4 controls the engine output by controlling fuel injection timing, fuel injection pulse width, throttle valve opening, etc., based on the engine's required driving force. Furthermore, the engine control unit 4 can control the engine's start / stop.

[0106] The motor control unit 5 controls the motor drive unit 8 based on the motor drive force requested by the HEV control unit 3, thereby controlling the operation of the MG10. The motor drive unit 8 is configured as an electrical circuit unit having a drive circuit for the MG10.

[0107] The motor control unit 5, based on the motor's required driving force, instructs the motor drive unit 8 to make the MG10 rotate in a powered manner when the MG10 should be rotated in a powered manner, and instructs the motor drive unit 8 to make the MG10 rotate in a regenerative manner when the MG10 should be rotated in a regenerative manner.

[0108] Although the illustration is omitted here, a driving battery that serves as the power source for the MG10 is provided in the vehicle control system 1. The driving battery is charged based on the electricity generated by the regenerative rotation of the MG10.

[0109] The driving stability control unit 6 is configured to perform controls related to vehicle driving stability, such as VDC (Vehicle Dynamics Control). As one of the controls related to vehicle driving stability, the driving stability control unit 6 controls the hydraulic brakes. As for controlling these brakes, the driving stability control unit 6 controls an actuator provided as a brake-associated actuator 9 based on the required braking force indicated from the control unit 23. The brake-associated actuator 9 may be, for example, a hydraulic control actuator for controlling the hydraulic pressure output from the brake booster to the master cylinder and / or the hydraulic pressure in the brake fluid piping, or various other brake-associated actuators. Specifically, the driving stability control unit 6 controls the aforementioned hydraulic control actuator based on the required braking force to brake the vehicle.

[0110] Here, the vehicle control system 1 in this example has a stop-and-hold function. The stop-and-hold function is a function that keeps a stopped vehicle in a stopped state. Specifically, when the required braking force at the time of stopping, i.e., the braking force at the time of stopping, is not a braking force sufficient to keep the vehicle in a stopped state (hereinafter referred to as "stop-and-hold braking force Tp"), the function increases the brake hydraulic pressure to make the braking force Tp or higher, thereby keeping the vehicle in a stopped state.

[0111] Reference Figure 2 The stop-and-hold function will be explained.

[0112] Here, we illustrate the changes in vehicle speed (the vehicle speed js) as the vehicle decelerates until it comes to a stop, and the changes in braking force after the vehicle stops.

[0113] The stop-and-hold function is a function that, when the required braking force at the time of stopping (i.e., when the braking force at the time of stopping is not greater than or equal to the predetermined braking force Tp for stop-and-holding), pressurizes the brake hydraulic fluid to make the braking force equal to or greater than the stop-and-holding braking force Tp, thereby keeping the vehicle in a stopped state.

[0114] The stop-and-hold braking force Tp can be defined as the braking force required to keep the vehicle at a stop. This stop-and-hold braking force Tp can be defined either as the limit value (lower limit) of the braking force used to keep the vehicle at a stop, or as a value that takes a margin into account (limit value + margin).

[0115] In this example, a condition related to vehicle speed is defined as the criterion for determining whether a vehicle is stopped. Specifically, in this example, a vehicle is considered to be stopped when its speed is below a first speed threshold. Here, the first speed threshold is not limited to strictly defining the moment when the speed reaches 0 km / h; it can be set to any moment that can be considered a stopped state. As an example, the first speed threshold is considered to be a value within the range of 0 km / h to 1 km / h. In this example, the first speed threshold is set to 0.5 km / h.

[0116] In the diagram, the time of stopping is denoted as time t1.

[0117] In the stop-and-hold function, it is determined whether the required braking force at the moment of stopping (stopping braking force) is greater than or equal to the stop-and-hold braking force Tp. In the illustrated example, assuming the stopping braking force is "0", in this case, the stopping braking force is less than the stop-and-hold braking force Tp. Therefore, through the stop-and-hold function, the required braking force is controlled to be greater than or equal to the stop-and-hold braking force Tp, the brake hydraulic pressure is increased to be greater than or equal to the hydraulic pressure required for stop-and-hold, and the vehicle is stopped and held by the brake hydraulic pressure obtained by this increased pressure.

[0118] Here, in the stop-and-hold function in this example, if the braking force when the vehicle is stopped is greater than or equal to the stop-and-hold braking force Tp, the braking force will be required to remain at the stopping braking force.

[0119] In this example, the processing for implementing the stop-and-hold function described above, specifically, the execution entity for each of the following processes—determining whether it is a stop, determining whether pressure boosting is required based on the stop-and-hold braking force Tp, and controlling the pressure boosting of the brake hydraulic fluid when pressure boosting is required—is, for example, the driving stability control unit 6.

[0120] It should be noted that the execution subject for implementing the stop-and-hold function is not limited to the driving stability control unit 6; for example, other computer devices such as the control unit 23 may also be used as the execution subject.

[0121] <2. Regarding the pre-pressurization process as an implementation method>

[0122] Next, the pre-pressurization process as an implementation method will be explained.

[0123] Figure 3 This is a functional block diagram for explaining the pre-boosting process as an embodiment, and the functions related to the pre-boosting process of the control unit 23 of the driving assistance control unit 2 are shown in the block diagram.

[0124] As shown in the figure, the control unit 23 has a target driving force calculation unit F1, a driving mode selection unit F2, and a calculation unit F3.

[0125] The target driving force calculation unit F1 performs the above-mentioned target driving force calculation.

[0126] As a vehicle driving mode selection function, the driving mode selection unit F2 allows users to choose between engine driving mode and EV (Electric Vehicle) driving mode. Engine driving mode is the mode in which the engine is running while driving, while EV driving mode is the mode in which the engine is off and the vehicle is driven by the MG10.

[0127] It should be noted that in hybrid vehicles, there are various well-known methods for selecting engine driving mode and EV driving mode, and it is not limited to any one specific method.

[0128] The computation unit F3 calculates the required driving force for drive control of the MG10 and the required braking force for hydraulic brake control based on the target driving force.

[0129] Here, the calculation unit F3 performs a pre-boost process, which pre-boosts the brake hydraulic fluid before the stopping time. Specifically, the pre-boost process refers to pre-boosting the brake hydraulic fluid before the stopping time and setting the driving force that offsets the braking force used for pre-boosting to the required driving force.

[0130] Figure 4 This diagram illustrates the general outline of the pre-boost process and shows the changes in vehicle speed, braking force, and offset driving force during the period from when the vehicle gradually decelerates until it is brought to a stop by the stop-hold function.

[0131] First, in this example, the pre-boost process begins at the closest possible moment before stopping. The determination of whether it is the moment before stopping is based on whether the accelerator is off and the vehicle speed is below a second speed threshold. Here, the second speed threshold is set to a value greater than the first speed threshold mentioned above. For example, consider setting the second speed threshold to a value within the range of 2 km / h to 10 km / h.

[0132] In the figure, the moment just before stopping, determined based on such a second speed threshold and vehicle speed, is denoted as time t2.

[0133] Here, we assume the braking force at time t2, just before stopping, is "0". However, due to the pre-boost process, the braking force gradually increases towards the stopping time (time t1). Furthermore, during the pre-boost process, as shown in the diagram of the change in the offsetting driving force, a driving force that offsets the braking force is output. Specifically, a process is performed to set the offsetting driving force to the required driving force. Thus, consistency with the target driving force is achieved.

[0134] By performing pre-pressurization, the braking force during parking can be increased, and the amount of hydraulic pressurization required to increase the braking force to the stop-hold braking force Tp through the stop-hold function can be reduced. That is, this reduces the operating noise and / or vibration of the motor used for brake hydraulic pressurization during stop-hold, and improves NV performance (Noise Vibe) for the stop-hold function.

[0135] Ideally, to improve NV performance, the braking force when stopped should be increased to above the stop-hold braking force Tp, i.e., the hydraulic boost should be set to "0". However, in this case, it is possible that some of the driving force becomes too large, leading to poor fuel efficiency and / or electrical efficiency.

[0136] Therefore, in this embodiment, the arithmetic unit F3 performs the following control during the pre-boost process: The required braking force is controlled such that the increase in braking force for pre-boost is within the range of an NV braking force threshold Nth that is less than the stop holding braking force Tp.

[0137] Figure 5 This is an explanatory diagram regarding the NV braking force threshold Nth.

[0138] In this example, the NV braking force threshold Nth is calculated based on the stop-and-hold braking force Tp and the allowable braking force Um after stopping. Here, the allowable braking force Um after stopping refers to the permissible amount of braking force increase when the vehicle is stopped. By appropriately setting this post-stop increase, it is possible to prevent the NV performance during stop-and-hold from falling below the permissible performance.

[0139] In this example, the NV braking force threshold Nth is calculated as the value obtained by subtracting the allowable braking force for rising after stopping from the stop-holding braking force. That is, "NV braking force threshold Nth = Stop-holding braking force Tp - Allowable braking force for rising after stopping Um".

[0140] Therefore, the NV braking force threshold Nth is calculated to be a value smaller than the stop-hold braking force Tp, and the increase in braking force during pre-boost processing stops at a level smaller than the stop-hold braking force Tp. Thus, it is possible to prevent excessive increase in the offset driving force and to suppress deterioration in fuel efficiency and / or electrical efficiency.

[0141] Furthermore, by calculating the NV braking force threshold Nth as described above, it is possible to ensure that the increase in braking force after stopping (i.e., the increase in braking force based on the stop-hold function) does not exceed the allowable increase in braking force Um after stopping. Therefore, it is possible to ensure that the NV performance is not lower than the allowable performance.

[0142] Furthermore, in this example, in order to improve the suppression effect of deterioration in fuel efficiency and / or electrical efficiency, the calculation unit F3 also controls the increase in braking force during the pre-boost process based on the offset driving force. Specifically, the calculation unit F3 controls the required braking force in such a way that the increase in braking force for pre-boost is within the range where the offset driving force does not exceed a predetermined upper limit Dth of the offset driving force.

[0143] Figure 6 An explanatory diagram to offset part of the upper limit of the driving force Dth.

[0144] The upper limit of the offset driving force Dth is a specified upper limit value for the offset driving force. By specifying the upper limit of the offset driving force Dth and controlling it in a way that the offset driving force does not exceed the upper limit of the offset driving force Dth, it is possible to ensure that the offset driving force does not exceed the upper limit allowed in terms of fuel efficiency and / or electrical efficiency.

[0145] Furthermore, in this example, the calculation unit F3 controls the increase of the allowable braking force Um after stopping when the slope of the road on which the vehicle is traveling is large, compared to the case of a small slope.

[0146] It should be noted that the slope information here can be obtained using either real-time information detected by the slope sensor or predicted information obtained by predicting the slope at the time of parking. The slope prediction can be performed, for example, by image recognition processing performed by the image processing unit 22.

[0147] Figure 7 The following diagram illustrates the allowable braking force Um1 for a stop and ascent after a small slope and the allowable braking force Um2 for a stop and ascent after a large slope.

[0148] As shown in the figure, the allowable braking force Um2 after stopping and ascending under a steep gradient is greater than that under a gentle gradient, which is Um1. Hereinafter, the NV braking force threshold Nth calculated based on the allowable braking force Um1 after stopping and ascending corresponding to the gentle gradient will be denoted as "Nth1", and the NV braking force threshold Nth calculated based on the allowable braking force Um2 after stopping and ascending corresponding to the steep gradient will be denoted as "Nth2".

[0149] Here, when the driving road has a large gradient, a large value is set as the stop-hold braking force Tp. Thus, if the stop-hold braking force Tp increases without increasing the allowable rebound braking force Um, the NV braking force threshold Nth calculated based on "stop-hold braking force Tp - allowable rebound braking force Um" will increase. This increases the amount of driving force used to offset the increase in the braking force, potentially leading to increased fuel and / or electricity consumption to offset the pre-boost. Therefore, in this example, as described above, when the gradient is large, the allowable rebound braking force Um is increased to prevent the NV braking force threshold Nth from becoming too large.

[0150] Therefore, it is possible to mitigate the deterioration of fuel efficiency and electrical efficiency when seeking to improve NV performance regarding stop-and-go on inclines.

[0151] Figure 8 This diagram illustrates the effect of variable control of the braking force Um that allows for ascent after stopping, corresponding to the aforementioned slope.

[0152] Regarding the braking force and the offsetting driving force in the diagram, the dashed line represents the case of a small slope, and the solid line represents the case of a large slope. As shown in the figure, under the condition of a large slope, the increase in braking force generated by the pre-boosting process is suppressed. Along with this, the increase in offsetting driving force is also suppressed.

[0153] Furthermore, regarding the control of braking force during pre-boosting, the calculation unit F3 in this example performs control corresponding to the aforementioned COMFORT mode and ECO mode. Specifically, when ECO mode is set, the calculation unit F3 performs control that reduces the upper limit Dth of the offset driving force compared to when COMFORT mode is set.

[0154] Figure 9 This shows the relationship between the upper limit of the offset driving force Dth_E set in ECO mode and the upper limit of the offset driving force Dth_C set in COMFO RT mode.

[0155] Figure 10 This diagram illustrates the role of setting the upper limits of these offset driving forces, Dth_E and Dth_C.

[0156] Regarding the offsetting driving force and braking force in the diagram, the dashed line represents the ECO mode and the solid line represents the COMFORT mode.

[0157] As described above, in this example, the braking force during pre-boosting is controlled in such a way that the amount of driving force to be offset does not exceed the upper limit Dt h of the amount of driving force to be offset. Therefore, in the ECO mode where the upper limit Dth_E of the amount of driving force to be offset is set small, the increase in the amount of driving force to be offset during the pre-boosting process is suppressed, and the suppression effect of deterioration in fuel efficiency and / or electric power efficiency is improved.

[0158] On the other hand, in the COMFORT mode where the upper limit Dth_C of the amount of driving force to be offset is set large, the amount of increase in the braking force during the pre-boosting process becomes larger. In the figure, as the amount of increase U in the braking force for stopping the holding function by hydraulic boosting, the amount of increase Ue in the braking force in the ECO mode is expressed as "U e", and the amount of increase Uc in the braking force in the COMFORT mode is expressed as "Uc". However, in the COMFORT mode where the amount of increase in the braking force during the pre-boosting process becomes larger, the amount of increase U in the braking force becomes smaller (Uc < Ue). That is, the amount of hydraulic boosting based on the stop holding function can be suppressed, and thus, in the COMFORT mode, the suppression effect of noise and / or vibration when the stop holding function is exerted is improved.

[0159] Furthermore, as the control of the braking force during the pre-boosting process, the arithmetic unit F3 in this example performs control corresponding to the engine driving mode and the EV driving mode. Specifically, when in the engine driving mode, the arithmetic unit F3 performs control to reduce the NV braking force threshold Nth compared to when in the EV driving mode.

[0160] Figure 11 Shows the relationship between the NV braking force threshold Nth_eg set in the engine driving mode and the NV braking force threshold Nth_mt set in the EV driving mode.

[0161] In this example, these NV braking force thresholds Nth_eg and Nth_mt are calculated using the post-stop rise allowable braking force Um for the engine driving mode and the EV driving mode, respectively. Specifically, the post-stop rise allowable braking force Um for the engine driving mode as shown by "Um_eg" in the figure and the post-stop rise allowable braking force Um for the EV driving mode as shown by "Um_mt" in the figure are defined. At this time, "Um_eg > Um_mt".

[0162] Moreover, regarding the NV braking force threshold Nth_eg for the engine driving mode, it is calculated using the stop holding braking force Tp and the post-stop rise allowable braking force Um_eg ("Nth_eg = Tp - Um_eg"), and regarding the NV braking force threshold Nth_mt for the EV driving mode, it is calculated using the stop holding braking force Tp and the post-stop rise allowable braking force Um_mt ("Nth_mt = Tp - Um_mt").

[0163] Here, in engine driving mode, the sound of the motor operating during hydraulic boost when the vehicle is stopped is difficult for occupants to perceive due to the engine noise. Therefore, in engine driving mode as described above, the NV braking force threshold Nth_eg is reduced, and the offset driving force during pre-boost is reduced. This suppresses engine fuel consumption during pre-boost and helps to mitigate fuel efficiency degradation.

[0164] <3. Example of processing order>

[0165] Reference Figure 12 and Figure 13 A specific processing sequence example for implementing the pre-pressurization process described above will be explained.

[0166] It should be noted that in this example, these Figure 12 and Figure 13 The series of processes shown are executed based on a program stored in a predetermined storage device such as a ROM within the control unit 23 itself. The control unit 23 repeatedly executes these processes at time intervals, for example, at predetermined periods. Figure 12 and Figure 13 The series of processes shown.

[0167] exist Figure 12 In step S101, the control unit 23 calculates the target driving force. As described above, the target driving force is calculated in ACC as a target value for achieving constant speed driving control and following driving control. Furthermore, in states other than ACC, the calculation is based on acceleration and / or braking operations performed by the driver.

[0168] In step S102, following step S101, the control unit 23 determines whether it is the moment before stopping. Specifically, in this example, the determination is made based on whether the accelerator is off and the vehicle speed is below the aforementioned second vehicle speed threshold.

[0169] In step S102, if it is determined that the moment before stopping is not imminent, the control unit 23 proceeds to step S103, sets the target driving force to the required driving force, sets "0" to the required braking force, and ends the process. Figure 12 and Figure 13 The series of processes shown.

[0170] That is, in the state just before the stop (time t2), no braking force for pre-boosting and / or control to offset part of the driving force are applied.

[0171] On the other hand, in step S102, if it is determined that it is just before stopping, the control unit 23 proceeds to step S104 to confirm the driving mode. That is, it determines whether the current driving mode is engine driving mode or EV driving mode.

[0172] In step S104, if it is determined that the engine driving mode is in progress, the control unit 23 proceeds to step S105 to determine whether there is a slope. Specifically, in this example, it is determined whether the slope value (%) of the driving road detected by the slope sensor is greater than or equal to a predetermined value (for example, an absolute value of 3% or more).

[0173] In step S105, if it is determined that there is a slope, the control unit 23 enters step S106 and sets a first value (for example, a value equivalent to 100N: N is Newton) as the allowable braking force Um after stopping and ascending, and then enters step S111.

[0174] On the other hand, if it is determined that there is no slope, the control unit 23 moves from step S105 to step S107 and sets a second value (for example, a value equivalent to 75N) as the allowable braking force Um after stopping and moves to step S111.

[0175] In addition, if it is determined to be in EV driving mode in step S104, the control unit 23 enters step S108 and determines whether there is a slope by the same process as in the previous step S105.

[0176] In step S108, if it is determined that there is a slope, the control unit 23 enters step S109 and sets a third value (for example, a value equivalent to 50N) as the allowable braking force Um after stopping and enters step S111.

[0177] On the other hand, if it is determined in step S108 that there is no slope, the control unit 23 enters step S110 and sets a fourth value (for example, a value equivalent to 25N) as the allowable braking force Um after stopping and enters step S111.

[0178] Here, comparing a set of steps S106 and S107, and a set of steps S109 and S110, it can be seen that in this example, when in engine driving mode, compared to when in EV driving mode, the value of the allowable braking force Um after stopping is increased. That is, when in engine driving mode, compared to when in EV driving mode, the NV braking force threshold Nth is decreased (refer to...). Figure 11 ).

[0179] Furthermore, based on the comparison between steps S106 and S107, and between steps S109 and S110, it can be seen that in this example, under the condition of a large slope (a sloped road), compared with the condition of a small slope (a flat road), the allowable braking force Um after stopping is increased (refer to...). Figure 7 , Figure 8 ).

[0180] It should be noted that for each of steps S106, S107, S109, and S110, the allowable braking force Um after stopping can also be set to a value equivalent to the braking hydraulic pressure (MPa) and / or electrical force (kW). For example, if it is electrical, it can be set to 1kW, 0.75kW, 0.5kW, 0.25kW, etc., respectively, as set in S106, S107, S109, and S110.

[0181] The processing of step S111 and the subsequent step S112 becomes the processing for calculating the NV braking force threshold Nth based on the set allowable braking force Um after stopping.

[0182] Specifically, in step S111, the control unit 23 calculates the stop-holding braking force Tp. The stop-holding braking force Tp is calculated based on information such as the gradient.

[0183] In step S112, the control unit 23 calculates the NV braking force threshold Nth. Specifically, it calculates "NV braking force threshold Nth = stop holding braking force Tp - allowable braking force Um after stopping".

[0184] In response to the calculation of the NV braking force threshold Nth in step S112, the control unit 23 initiates processing. Figure 13 Step S113 is shown.

[0185] exist Figure 13 In step S113, the control unit 23 determines whether the current braking force is less than the NV braking force threshold Nth. The current braking force refers to the braking force that is being output based on the required braking force.

[0186] In step S113, if it is determined that the current braking force is less than the NV braking force threshold Nth, the control unit 23 enters step S114 and sets "current braking force + α" as the provisional required braking force.

[0187] Here, in this example, the pre-boost process is performed by gradually increasing the braking force from the moment just before stopping, but the "α" mentioned above refers to the value specifying the rate of increase in braking force at this time (the rate of increase per unit time). Although this is repeated as described above... Figure 12 and Figure 13The process is shown as a series of processes, but by sequentially executing the process of step S114, the braking force increases by α each time and gradually approaches the NV braking force threshold Nth.

[0188] It should be noted that α can be a fixed value or a variable value. When α is set to a fixed value, the rate of increase of braking force during the pre-boost process can be made variable depending on certain conditions.

[0189] In step S114, the control unit 23 uses such a value of α to set "current braking force + α" as a provisional required braking force.

[0190] It should be noted that the value is set to "provisional" because, according to the branch processing of step S118 described later, there may be a situation where the value calculated in step S114 is not set as the required braking force.

[0191] Here, if the control unit 23 determines in step S113 that the current braking force is not less than the NV braking force threshold Nth, it causes the processing to proceed to step S120, where it sets the "target driving force + current braking force" as the required driving force and sets the current braking force as the required braking force, and then ends the process. Figure 12 and Figure 13 The series of processes shown.

[0192] Therefore, when the current braking force reaches the NV braking force threshold Nth, the increase in braking force using the aforementioned α is stopped, and the hydraulic pressure boosting performed by the pre-pressurization process is completed.

[0193] Furthermore, if the control unit 23 determines that the current braking force is less than the NV braking force threshold Nth and has performed the above-mentioned step S114, the process proceeds to step S115.

[0194] In step S115, the control unit 23 confirms whether it is ECO mode or COMFORT mode. In step S115, if it is determined to be COMFORT mode, the control unit 23 sets the above-mentioned "Dth_C" (e.g., 500N) as the upper limit of the offset driving force Dth in step S116, and proceeds to step S118.

[0195] On the other hand, in step S115, if it is determined to be ECO mode, the control unit 23 sets the above-mentioned "Dth_E" (e.g., 200N) as the upper limit of the driving force Dth to offset part of the drive force in step S117, and proceeds to step S118.

[0196] It should be noted that for each step of S116 and S117, the value of the brake hydraulic pressure and / or electrical pressure that offsets the upper limit of the driving force can also be set accordingly. For example, if it is electrical, consider setting 5kW for S116 and 2kW for S117.

[0197] In step S118, the control unit 23 determines whether the driving force of the offset braking force increase portion is less than the upper limit Dth of the offset driving force. That is, it determines whether the provisional required braking force set in the previous step S114 is less than the upper limit Dth of the offset driving force set in step S116 or S117.

[0198] In step S118, if it is determined that the driving force of the offsetting braking force rises is less than the upper limit Dth of the offsetting driving force, the control unit 23 proceeds to step S119, sets "target driving force + provisional required braking force" as the required driving force, sets the provisional required braking force as the required braking force, and ends the process. Figure 12 and Figure 13 The series of processes shown.

[0199] That is, if the "provisional required braking force" set in step S114 has not yet reached the upper limit Dth of the offset driving force, the "provisional required braking force" is set as the required braking force, and the braking force is increased by an amount of "α" to the current braking force.

[0200] On the other hand, if in step S118 it is determined that the driving force for offsetting the increased braking force is not less than the upper limit Dth of the offset driving force, the control unit 23 proceeds to the previously described step S120, sets "target driving force + current braking force" as the required driving force, sets the current braking force as the required braking force, and ends the process. Figure 12 and Figure 13 The series of processes shown.

[0201] That is, when the "provisional required braking force" reaches the upper limit of the driving force Dth to offset part of the braking force, the increase of braking force using α is stopped, and the hydraulic pressure is increased by the pre-pressurization process.

[0202] <4. Variations>

[0203] It should be noted that, as an implementation method, it is not limited to the specific examples exemplified above, and various variations can be selected.

[0204] For example, the above example illustrates the pre-boost process used as an implementation method for parking in ACC (Adaptive Cruise Control), but this pre-boost process can also be applied to parking based on autonomous driving technology and parking using the one-pedal function. It should be noted that the one-pedal function refers to the function of accelerating or decelerating the vehicle based on the operation of a single pedal.

[0205] Furthermore, while examples of the vehicle control system of the present invention being applied to hybrid vehicles have been given above, the vehicle control system of the present invention can also be adapted to EVs without an engine and / or motor vehicles without a motor as a drive source for the wheels.

[0206] <5. Summary of Implementation Methods>

[0207] As described above, the vehicle control system (1) of the embodiment has an engine or motor as the drive source for the wheels of the vehicle, and includes: a target driving force calculation unit (F1) that calculates the target driving force of the vehicle; an arithmetic unit (F3) that calculates the required driving force for the drive control of the engine or motor and the required braking force for the hydraulic braking control based on the target driving force; and a stop-and-hold processing unit (e.g., a driving stability control unit 6) that, when the required braking force at the time of stopping, i.e., the braking force at the time of stopping, is not above the stop-and-hold braking force that can keep the vehicle in a stopped state, performs a process of pressurizing the brake hydraulic fluid to make the braking force above the stop-and-hold braking force to keep the vehicle in a stopped state. The arithmetic unit performs a pre-pressurization process before the time of stopping, and in the pre-pressurization process, controls the required braking force in such a way that the increase of the braking force for pre-pressurization does not exceed a braking force threshold value that is smaller than the stop-and-hold braking force. The pre-pressurization process is a process of pre-pressurizing the brake hydraulic fluid and setting the driving force that offsets the braking force for pre-pressurization as the required driving force.

[0208] By performing the pre-boosting process described above, it is possible to reduce the amount of hydraulic boost after stopping based on the stop-and-hold function, and thus improve NV performance. In this pre-boosting process, the braking force not used for pre-boosting rises to the stop-and-hold braking force, but stops rising to a level lower than the stop-and-hold braking force. Therefore, it is possible to prevent excessive increase in the driving force used for offsetting this effect, and to suppress deterioration in fuel efficiency or electrical efficiency.

[0209] Therefore, the vehicle's stop-and-hold function can improve NV performance while seeking to suppress the deterioration of fuel efficiency or electric efficiency.

[0210] Furthermore, in the vehicle control system implemented as an example, the arithmetic unit controls the required braking force in such a way that the increase of the braking force used for pre-boosting is within a range where the offset driving force does not exceed a predetermined upper limit of the offset driving force (see steps S118 to S120).

[0211] Therefore, it is possible to ensure that the offset driving force does not exceed the upper limit of driving force allowed from the perspective of fuel efficiency or electric efficiency.

[0212] Therefore, it is possible to seek ways to improve fuel efficiency or mitigate the decline in electricity efficiency.

[0213] Furthermore, in the vehicle control system implemented as an example, as a mode related to vehicle control, a first mode (COMFORT mode) that emphasizes passenger comfort and a second mode (ECO mode) that emphasizes fuel efficiency or electric efficiency can be set. When the second mode is set, the calculation unit will offset part of the reduction in the upper limit of driving force compared to the case where the first mode is set (see steps S115 to S117).

[0214] Thus, in the second mode, which prioritizes fuel efficiency and / or electrical efficiency, the upper limit of the offset driving force can be reduced to suppress the rise of the offset driving force. Conversely, in the first mode, which prioritizes occupant comfort, the upper limit of the offset driving force can be increased, i.e., the pre-boost amount can be increased to suppress the hydraulic boost amount during stop holding.

[0215] Therefore, it is possible to achieve appropriate pre-boosting treatment corresponding to the characteristics of the first mode and the second mode respectively.

[0216] Furthermore, in the vehicle control system implemented as an example, the calculation unit calculates the braking force threshold as a value obtained by subtracting the allowable braking force after stopping from the stop holding braking force (see step S112).

[0217] The permissible increase in braking force after stopping refers to the permissible increase in braking force when the vehicle is stopped and held.

[0218] As described above, by calculating the braking force threshold as a value obtained by subtracting the allowable braking force after stopping from the stop-hold braking force, it is possible to prevent NV performance from falling below the allowable performance.

[0219] Furthermore, in the vehicle control system implemented as an example, the arithmetic unit increases the allowable braking force for rising after stopping when the slope of the vehicle's travel path is large, compared to when the slope is small (see steps S105 to S110).

[0220] When driving on a steep incline, a large value is set as the stopping and holding braking force. However, if the stopping and holding braking force increases without increasing the allowable braking force after stopping, the braking force threshold calculated based on "stopping and holding braking force - allowable braking force after stopping" will increase. This would increase the amount of driving force needed to offset the increase in braking force, potentially leading to increased fuel or electricity consumption to offset the pre-boost. Therefore, in situations with steep inclines as described above, the allowable braking force after stopping is increased to prevent the braking force threshold from becoming excessive.

[0221] Therefore, it is possible to mitigate the deterioration of fuel efficiency or electric efficiency when seeking to improve NV performance regarding stop-and-hold performance on inclines.

[0222] Furthermore, in the vehicle control system of the embodiment, the vehicle is configured as a hybrid vehicle having an engine and a motor as the driving source of the wheels, and can be set to a driving mode in which the engine operates to drive the wheels, namely an engine driving mode, and a driving mode in which the engine stops and the wheels are driven by the motor, namely an EV driving mode. In the pre-boost processing, when in the engine driving mode, the arithmetic unit reduces the braking force threshold compared to when in the EV driving mode (see steps S104 to S110).

[0223] In engine driving mode, the sound of the motor operating during hydraulic boost when the vehicle is stopped is difficult for occupants to perceive due to the engine noise. Therefore, in engine driving mode as described above, the braking force threshold is reduced, and the offset driving force during pre-boost is also reduced.

[0224] Therefore, it is possible to improve the effect of suppressing the decline in fuel efficiency.

Claims

1. A vehicle control system, characterized in that, It is the vehicle control system in the vehicle. It has an engine or motor as the driving source for the wheels in the vehicle. And possesses: A target driving force calculation unit calculates the target driving force of the vehicle. The computing unit calculates the required driving force for drive control of the engine or motor and the required braking force for hydraulic braking control based on the target driving force. as well as The stop-and-hold processing unit, when the required braking force during a stop is not a stop-and-hold braking force sufficient to keep the vehicle stationary, performs a process to increase the brake hydraulic pressure to make the braking force equal to or greater than the stop-and-hold braking force, thereby keeping the vehicle stationary. Before the stopping moment, the calculation unit performs a pre-boosting process that pre-boosts the brake hydraulic fluid and sets the offsetting driving force that counteracts the braking force used for pre-boosting to the required driving force. In the pre-boosting process, the required braking force is controlled such that the increase in the braking force used for pre-boosting does not exceed a braking force threshold value that is smaller than the stop holding braking force.

2. The vehicle control system according to claim 1, characterized in that, The calculation unit controls the required braking force in such a way that the increase in the braking force used for the pre-boost is within the range where the offset driving force does not exceed a predetermined upper limit of the offset driving force.

3. The vehicle control system according to claim 2, characterized in that, As a control-related mode for the vehicle, it is possible to set a first mode that prioritizes occupant comfort and a second mode that prioritizes fuel efficiency or electric efficiency performance. When the second mode is set, the arithmetic unit reduces the upper limit of the offset driving force compared to when the first mode is set.

4. The vehicle control system according to any one of claims 1 to 3, characterized in that, The calculation unit calculates the braking force threshold as a value obtained by subtracting the allowable braking force after stopping from the stop-hold braking force.

5. The vehicle control system according to claim 4, characterized in that, The calculation unit increases the allowable braking force for rising after stopping when the slope of the road the vehicle is traveling on is large, compared to when the slope of the road is small.

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