BRAKING CONTROL DEVICE FOR A VEHICLE AND VEHICLE WITH BRAKING CONTROL

A vehicle includes a regenerative brake of a rotating electric machine and a friction brake which is a mechanical brake as braking means for applying a braking force to rotations of the left and right wheels at the front and rear of the vehicle. The vehicle also includes an SOC information obtaining part that obtains an amount of charge (SOC) of a battery of the vehicle and an ECU. The ECU may include a VSA modulator and an ACC-ECU that generate, without a braking operation of the driver, a regenerative braking force with the regenerative brake and a friction braking force with the friction brake. The ECU prohibits an operation of the VSA modulator and/or an operation of the ACC-ECU according to a temperature of the friction brake and the amount of charge (SOC) of the battery.

CROSS REFERENCE STATEMENT

The present application is based on, and claims priority from, Japanese Patent Application Number 2021-161723, filed Sep. 30, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

Technical Field

The disclosure is related to a braking control device for a vehicle and a vehicle with braking control.

Related Art

There are vehicles among hybrid electric vehicles (HEVs), which make a combined use of an engine and a rotating electric machine as a drive source, and electric vehicles (EVs), which only use a rotating electric machine as a drive source, that are capable of being accelerated and decelerated by a driver by operating an accelerator pedal alone.

Wheels of a vehicle are each installed with a friction brake such as a disc brake. Such a friction brake may include a brake disc that rotates with a wheel and brake pads that are configured so that the brake disc may be sandwiched between the brake pads. With this friction brake, when a driver presses a brake pedal, the brake pads become pressed against the brake disc through hydraulic pressure supplied from a master cylinder causing frictional resistance to be generated between the brake pads and the brake disc. Through this frictional resistance, braking force is applied to a rotation of the wheel causing the vehicle to decelerate or stop.

A travel control technology called Adaptive Cruise Control (ACC) is known as an elemental technology for realizing automated driving. With a travel control device that includes an ACC function, travel control including constant-speed travel control and follow-traffic-ahead travel control are realized through integrated control of the drive system and brake system of the vehicle installed with the travel control device (the “host vehicle”). Note that the constant-speed travel control controls the host vehicle to travel at constant speed based on a target vehicle speed and the follow-traffic-ahead travel control controls the host vehicle to travel by maintaining a predetermined vehicle-to-vehicle distance with another vehicle travelling ahead of the host vehicle. When it is detected that the host vehicle has become close to a preceding vehicle, the ACC controls the brake system of the host vehicle to automatically decelerate the host vehicle.

With such ACC, engine braking is also used in order to suppress the heating of brake pads and so on of the friction brake and to reduce deceleration shock at an early stage of deceleration. When a requested amount of deceleration from automated braking is less than a predetermined value (for example, a braking force limit of engine braking), braking force is applied using engine braking. When the requested amount of deceleration is equal to or greater than the predetermined value, deceleration is performed in accordance with the requested amount of deceleration from a constant speed travel / vehicle-to-vehicle distance control device by changing from engine braking to friction braking.

Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2020-199814) discloses a braking control device for a vehicle that is equipped with a regenerative brake and friction brake. When the temperature of the friction brake is low, the braking control device disclosed in Patent Literature 1 activates the friction brake to raise its temperature by reducing regenerative braking and so on.

FIG.10shows a relationship between brake pad friction (hereinafter “brake friction”) and brake pad temperature (hereinafter “brake temperature”).

When a vehicle (a “following vehicle”) with an ACC function performs the follow-traffic-ahead travel control with respect to a preceding vehicle, brake temperature of the following vehicle (with an ACC function) does not rise in the “normal usage region” that is indicated with an arrow a inFIG.10.

However, in cases where the following vehicle (with an ACC function) travels continuously along a downhill slope, brake temperature rises in the “continuous-downhill-slope usage region” that is indicated by an arrow b inFIG.10and effectiveness of the friction brake drops with a rise in brake temperature (see arrow c ofFIG.10).

Conventional braking control devices for a vehicle have the following issues.(1) The braking control device for a vehicle disclosed in Patent Literature is not capable of responding to situations where the friction brake is at a high temperature.(2) In the case of vehicles that are capable of automated driving or ACC in which friction braking is applied regardless of an operation by a driver, frequent friction braking will cause the driver to feel discomfort when the driver operates the brake pedal. For example, as shown inFIG.10, when a vehicle continuously travels downhill, brake temperature rises and with this rise the effectiveness of the friction brake declines. When the driver is operating the brake, the driver will be able to feel the gradual decline in effectiveness of the friction brake. However, when the ACC (automated braking) is being used and the driver depresses the brake pedal, for example, to stop at a tollgate, the driver might experience discomfort or fear due to the decline in effectiveness. Therefore, there is a lack of predictability towards the decline in braking effectiveness.(3) In the case of vehicles that are equipped with a regenerative brake and friction brake, there is a need to appropriately actuate or cancel automated driving or ACC in accordance with an amount of charge of a battery, the regenerative brake, or the like.

SUMMARY

A braking control device for a vehicle according to an embodiment is a braking control device for a vehicle that includes a braking controller configured to generate, without a driver performing a braking operation, regenerative braking force from a regenerative brake and friction braking force from a friction brake. The braking control device for a vehicle includes: a battery charge amount obtaining part configured to obtain an amount of charge of a battery of the vehicle; and a processor. The processor is configured with a program to perform operations including: an operation as a brake temperature estimator configured to estimate a brake temperature of the friction brake; and an operation as a brake protection controller configured to prohibit an operation of the braking controller in accordance with a temperature of the friction brake and the amount of charge of the battery, the temperature of the friction brake being the brake temperature that has been estimated by the brake temperature estimator.

DETAILED DESCRIPTION

Embodiments of the disclosure will be described below with reference to the drawings as appropriate. In the drawings, common components will be designated with the same reference sign and overlapping explanations thereof will be omitted.

FIG.1is a plan view schematically showing an overall configuration of a vehicle that is installed with a braking control device for a vehicle that is in accordance with an embodiment. The braking control device for a vehicle is extensively integrated into the vehicle1. The braking control device for a vehicle may, due to the integrated nature thereof, be considered as the vehicle itself or may be considered as being installed on the vehicle1.

The vehicle1according to the embodiment is an electric vehicle (including a hybrid vehicle and a fuel-cell vehicle).

The vehicle1travels by applying a rotational drive to left and right rear wheels3using a rotating electric machine (a motor)2as a drive source. The rotating electric machine2functions as a generator as well. The rotating electric machine2is electrically connected to a battery4and operates with electricity supplied from the battery4.

The battery4is configured to supply electricity to individual components of the vehicle1(discharge of electricity) and to store regenerative electric power generated through regeneration control of the vehicle1(charging).

The amount of charge of the battery4(state of charge [SOC]; also referred to as the level of charge, rate of charge) is detected by an SOC information obtaining part50(battery charge amount obtaining part).

Rotational driving force outputted by the rotating electric machine2is distributed and transmitted individually to the left and right axles6by a differential device (a differential)5. Rotations of the left and right axles6are transmitted to the left and right rear wheels3that are attached to the ends of these axles6. In this way, the left and right rear wheels3are applied with rotational drive, and the vehicle1travels at a predetermined speed.

Left and right front wheels7and left and right rear wheels3of the vehicle1are each equipped with a friction brake8that is used to apply a mechanical brake to the above-described rotation. Each friction brake8is a disc brake and is configured to include a brake disc8aand brake pads (a brake caliper)8b. The disc brake8ais flat and circular in shape and is configured to rotate with a front wheel7or rear wheel3. The brake pads8bof each friction brake8are configured to sandwich and squeeze against a corresponding brake disc8awith hydraulic pressure so that frictional resistance is generated between the brake disc8aand the brake pads8b.

The vehicle1is equipped with an accelerator pedal9and a brake pedal10that are operable by a driver of the vehicle1. Close to the accelerator pedal9is installed an accelerator position detection sensor11that is configured to detect an amount by which the accelerator pedal9is depressed (accelerator position). The brake pedal10is equipped with a brake switch12that is configured to detect whether the brake pedal10is depressed (ON/OFF). The accelerator position detection sensor11and brake switch12are electrically connected to an electronic control unit (ECU)13(braking control device for a vehicle, brake protection controller) that make up the braking control device for a vehicle according to an embodiment. The amount of charge of the battery4is detected with an SOC information obtaining part50and is inputted to the ECU13.

Electronic Control Unit (ECU)13

The ECU13is activated (the power thereof is turned on) when an ignition switch IG is on (ON) and stops operating (the power thereof is turned off) when the ignition switch IG is off (OFF). The ECU13performs various types of control over the vehicle1from when the ECU13is activated by turning on (ON) the ignition switch IG to when the ECU13stops operation by turning off (OFF) the ignition switch IG.

The ECU13is an electronic control device that is composed of a microcomputer. The ECU13is configured from an LSI device that includes a microprocessor, ROM (read-only memory), RAM (random-access memory), a timer that is configured to measure time from when the brake switch12becomes OFF, a brake temperature estimator that is configured to estimate a temperature of the friction brake8, and an ACC brake protection controller. The ECU13, for example, realizes a braking controller, a brake temperature estimator, and a brake protection controller (described below) by executing a program stored in the ROM.

The ECU13includes a braking controller that generates a regenerative braking force from a regenerative brake and a friction braking force from a friction brake8without a braking operation of a driver.

The braking controller is composed of a VSA modulator (a vehicle behavior stabilizing device; “VSA” is a registered trademark of the Applicant)100(braking controller, braking control device for a vehicle), an ACC-ECU200(braking controller, braking control device for a vehicle). The VSA modulator100and ACC-ECU200will be described later with reference toFIG.2.

In some embodiments, the ECU13is configured to include the ACC-ECU200(braking controller, braking control device for a vehicle) that will be described later with reference toFIG.2.

The ECU13includes a function as a brake protection controller that is configured to prohibit an operation of the VSA modulator100or an operation of the ACC-ECU200or operations of the VSA modulator100and ACC-ECU200according to the amount of charge of a battery4and the temperature of the friction brake8.

As the brake protection controller, the ECU13prohibits the operation of the braking controller when the temperature of the friction brake8is equal to or greater than a predetermined temperature and the amount of charge of the battery4is equal to or greater than a predetermined amount.

As the brake protection controller, the ECU13operates the regenerative brake to a second predetermined amount (for example, SOC of approximately 90%) that is greater than a first predetermined amount (for example, SOC of approximately 80%) when the temperature of the friction brake8is equal to or greater than the predetermined temperature and the amount of charge of the battery4is equal to or greater than the first predetermined amount.

As the brake protection controller, the ECU13determines that the vehicle1is travelling on a downhill slope (the vehicle1is descending) when the amount of charge of the battery4increases continuously.

As the brake protection controller, the ECU13sets, as a threshold temperature, a brake temperature at which a decline in effectiveness of the friction brake8is permissible. Furthermore, the threshold temperature is made variable and is changed by the ECU13according to the amount of charge of the battery4. When the brake temperature that is estimated by an estimated temperature calculator110(seeFIG.2) exceeds the threshold temperature, the ECU13sets up a flag and prohibits an operation of the braking controller.

This prohibiting of the operation of the braking controller involves disabling an operation of the VSA modulator100or an operation of the ACC-ECU200or operations of the VSA modulator100and ACC-ECU200or cancelling an operation of the VSA modulator100that is running or an operation of the ACC-ECU200that is running or operations of the VSA modulator100and ACC-ECU200that are running.

A master cylinder15is connected to the brake pedal10via a brake booster14. A hydraulic piping16that extends from the master cylinder15is connected to a hydraulic unit (H/U)17. Four sets of hydraulic piping18that extends from the hydraulic unit (H/U)17are connected to the brake pads8bof individual friction brakes8. A hydraulic pump19is connected to the hydraulic unit (H/U)17. This hydraulic pump19is connected to the hydraulic unit (H/U)17via hydraulic piping20. The driving of the hydraulic pump19is controlled through an instruction from the ECU13. The master cylinder15is installed with a hydraulic pressure sensor21that detects hydraulic pressure within the master cylinder15. This hydraulic pressure sensor21is connected electrically to the ECU13.

When a driver presses down on the brake pedal10, a hydraulic pressure of a size corresponding to the amount of depression of the brake pedal10is generated in the master cylinder15. This hydraulic pressure is supplied to each friction brake8via the hydraulic piping16, hydraulic unit (H/U)17, and hydraulic piping18, and the brake pads8bof each friction brake8are pressed against a corresponding brake disc8a. As a result, frictional resistance (frictional braking force) is generated by individual friction brakes8, and braking force is applied with this frictional resistance to the rotations of the left and right front wheels7and left and right rear wheels3.

The ECU13is capable, when required to as will be described later, of driving the hydraulic pump19to drive the friction brake8so that braking force is applied to the rotations of the left and right front wheels7and left and right rear wheels3without having the brake pedal10depressed by the driver.

When the vehicle1decelerates, the rotating electric machine2functions as a generator and recovers a part of kinetic energy as electrical energy (regenerative energy), during which time the rotating electric machine (generator)2functions as a regenerative brake.

FIG.2is a block diagram showing a configuration of a vehicle1installed with a braking control device for a vehicle that is in accordance with an embodiment.

As shown inFIG.2, the vehicle1that is installed with a braking control device for a vehicle includes a VSA modulator100and an ACC-ECU200. The VSA modulator100is configured to stabilize vehicle behavior by controlling braking fluid pressure of a fluid supply path of a braking fluid pressure system. The ACC-ECU200is configured to perform adaptive cruise control (ACC) that includes: constant-speed travel control that controls the host vehicle (the vehicle installed with the ACC function) to travel at constant speed based on a vehicle speed that is set beforehand; and follow-traffic-ahead travel control that controls the host vehicle to follow a preceding vehicle that travels in the same direction in the same lane as the host vehicle by maintaining a predetermined vehicle-to-vehicle distance with the preceding vehicle.

The VSA modulator100is configured to include: an input part (omitted in the figure); an estimated temperature calculator110(brake temperature estimator); an estimated temperature comparing part120(brake protection controller), an ACC prohibit threshold121, an ACC return threshold122, a temperature rise flag123. The input part detects, as input elements, ON activation (power on) of the ignition switch IG101; an estimated temperature when engine is OFF102; a calculated initial estimated temperature103, a brake fluid pressure104, and vehicle speed105. The calculated initial estimated temperature103is calculated from the estimated temperature when engine is OFF102at the time of ON activation of the ignition switch IG101.

The estimated temperature calculator110calculates an estimated temperature of the friction brake8(seeFIG.1) based on the calculated initial estimated temperature103, brake fluid pressure104, and vehicle speed105.

The estimated temperature comparing part120compares the estimated temperature of the friction brake8that is estimated by the estimated temperature calculator110with the ACC prohibit threshold121and ACC return threshold122. When the brake temperature that is estimated by the estimated temperature calculator110exceeds the ACC prohibit threshold121or ACC return threshold122or the ACC prohibit threshold121and ACC return threshold122(threshold temperatures), the temperature rise flag123is set up.

The ACC prohibit threshold121is a control parameter that is used to prohibit the ACC based on the SOC information obtaining part50. The ACC return threshold122is a control parameter that is used to return to the ACC based on the SOC information obtaining part50.

The ACC-ECU200sets an ACC set condition201according to whether the temperature rise flag123is set up. The ACC-ECU200sets an ACC cancel condition202according to whether the temperature rise flag123is set up.

The ECU13may be configured to include the ACC-ECU200.

An operation of a brake protection controller of a braking control device for a vehicle (a vehicle) will be described below.

ACC Brake Protection Control of Comparative Example

An ACC brake protection control of a comparative example will be described below.

A braking control device for a vehicle (a vehicle) according to the comparative example is configured in the same way as the braking control device for a vehicle (a vehicle) as shown inFIG.2but with the SOC information obtaining part50removed.

FIG.3is a timing chart for describing an ACC brake protection control of the braking control device for a vehicle (a vehicle) of the comparative example. An estimated brake temperature and vehicle speed are shown on the vertical axes and time is shown on the horizontal axis.

As shown in the upper part ofFIG.3, the vehicle of the comparative example repeats acceleration (see parts of the line for vehicle speed where the line is drawn with smaller thickness) and braking (see parts of the line for vehicle speed where the line is drawn with greater thickness) through adaptive cruise control (ACC) that controls a host vehicle (a vehicle installed with the ACC function) to travel at constant speed based on a predetermined vehicle speed.

The VSA modulator of the vehicle according to the comparative example estimates brake temperature from vehicle speed and brake fluid pressure. The VSA modulator of the vehicle according to the comparative example sets, as an ACC cancel threshold temperature, a brake temperature at which a decline in braking effectiveness is permissible.

As shown in the lower part ofFIG.3, temperature of the friction brake8(estimated brake temperature) rises gradually. When the estimated brake temperature exceeds the ACC cancel threshold temperature, the VSA modulator of the vehicle according to the comparative example sets up a temperature rise flag (see reference sign d ofFIG.3) and cancels the ACC function.

Points Regarding ACC Brake Protection Control

Points to note regarding the ACC brake protection control will be described below.

FIG.4is a timing chart for describing notable points regarding the ACC brake protection control. InFIG.4, actual brake pad temperature is shown on the vertical axis and time from t0, time when a downhill slope travel starts, to t1, time when the downhill slope travel ends, is shown on the horizontal axis.

A threshold temperature Y °C for satisfying requirement A for performance guarantee is set for the actual brake pad temperature. The threshold temperature Y °C is used to ensure the performance of the friction brake. For a guaranteed performance of the friction brake, the actual brake pad temperature should not exceed the threshold temperature Y °C.

The thick line that is indicated with a reference sign e inFIG.4shows a rise in brake temperature when automated braking (ACC) is used but ACC is later cancelled while travelling on a downhill slope.

The thick dotted lines indicated with reference signs f and g show rises in brake temperature when a driver is operating the braking of a vehicle. The thick dotted line indicated with reference sign f inFIG.4shows a brake temperature rise for a case where braking operation is carried out by the driver alone from time t0, time when a downhill slope travel starts, to time t1, time when the downhill slope travel ends. The thick dotted line indicated with reference sign g inFIG.4shows a brake temperature rise during a period when braking operation is performed by the driver from the time when operation is transferred from the ACC to the driver until time t1 (time when the downhill slope travel ends).

The brake temperature rise of the line with reference sign e (ofFIG.4) is a case where automated braking (ACC) is used. The brake temperature rises of the lines with reference signs f and g (ofFIG.4) are cases where braking operation is carried out by the driver. By comparing the brake temperature rise of reference sign e with the brake temperature rises of reference signs f and g, it can be seen that the brake temperature rise is steeper for a case where automated braking (ACC) is used. In other words, when ACC is used and the vehicle travels under the follow-traffic-ahead travel control, brake temperature becomes higher compared to when braking is carried out through driver operation. The reason why brake temperature is prone to rise when ACC is in use while a vehicle travels continuously on a downhill slope will be described later.

When the actual brake pad temperature exceeds X °C, a temperature that meets a performance requirement for a braking-effectiveness-feel change, the ACC function is cancelled (see reference sign h ofFIG.4), and operation is transferred from the ACC to the driver (see reference sign i ofFIG.4). The driver to whom the operation is transferred is able to predict a decline in braking effectiveness.

When the actual brake pad temperature exceeds the temperature X °C, which is the temperature at which the ACC function is cancelled due to performance (braking-effectiveness-feel change), braking effectiveness gradually declines (see reference sign j ofFIG.4).

Braking performance after the ACC function is cancelled is as follows.

After the ACC function is cancelled, operation is performed by the driver as indicated by reference sign g ofFIG.4. By keeping the maximum brake temperature below or at Y °C while the vehicle is travelling on the downhill slope, braking efficiency and so on are guaranteed through brake temperature.

In this way, braking performance and predictability of a decline in braking effectiveness are secured through ACC brake protection control.

Reason Why Brake Temperature Is Prone to Rise During ACC Use When Travelling on A Downhill Slope

The reason why brake temperature is prone to rise during ACC use when a vehicle is travelling on a downhill slope will be described.

FIG.5shows a drawing of two vehicles: a preceding vehicle; and a following vehicle that is installed with an ACC function and is traveling behind the preceding vehicle. The drawing shows the following vehicle (ACC) performing the follow-traffic-ahead travel control with respect to the preceding vehicle along a continuously downhill slope.

FIG.6shows a timing chart that describes why brake temperature is prone to increase during ACC use when a vehicle is travelling on a continuously downhill slope ofFIG.5. The vertical axis shows brake temperature (estimated brake temperatures) and vehicle speed for the preceding vehicle and following vehicle (ACC), and the horizontal axis shows time.

As shown in the upper part ofFIG.6, brake temperature of the preceding vehicle rises through the use of ACC during downhill slope travel. The lower part ofFIG.6shows brake temperature of the preceding vehicle and the following vehicle (ACC). As shown in the lower part ofFIG.6, brake temperature of the following vehicle (ACC) rises through the use ACC during downhill slope travel.

As shown in the lower part ofFIG.6, a vehicle speed profile of the following vehicle (ACC) widens ( = deceleration width increases). Because of this, brake temperature of the following vehicle (ACC) is prone to rise when using the ACC.

Behavior Change During Downhill Slope Travel When Battery Becomes Fully Charged (State of Regeneration Restriction)

A change in behavior during downhill slope travel when a battery becomes fully charged (a state of regeneration restriction) will be described.

FIG.7shows a drawing in which a driver request is to keep a constant speed for a vehicle travelling along a slope with a 5% gradient.

FIG.8is a timing chart showing an amount of battery charge (state of charge, SOC) behavior, AP-OFF deceleration behavior due to regeneration, deceleration behavior due to a friction brake, and vehicle speed behavior over time when a vehicle is travelling on a slope as shown inFIG.7and the battery becomes fully charged (a state where regeneration is restricted).

As indicated by the “vehicle speed” ofFIG.8, a request of the driver is to maintain a constant speed. Because the vehicle is travelling on a downhill slope, an engine brake or a regenerative brake and a friction brake are used to maintain the constant speed.

When Battery Is Not Fully Charged

As shown by the “amount of charge of battery (SOC)” ofFIG.8, when the battery of the vehicle is not fully charged, AP-OFF deceleration through regeneration is possible, and AP-OFF deceleration through regeneration is performed. Accordingly, as shown by “deceleration from friction brake” ofFIG.8, deceleration through a friction brake is not performed. Note that an amount of AP-OFF deceleration through regeneration is small and is shown inFIG.8as a deceleration amount ZG.

When Battery Is Fully Charged

As shown by the “amount of charge of battery (SOC)” ofFIG.8, when the battery of the vehicle is fully charged, the vehicle is in a state where regeneration is not possible (in the same state as neutral), and AP-OFF deceleration through regeneration cannot be obtained. As shown by “deceleration from friction brake” ofFIG.8, deceleration through the friction brake is used to cover the lack of deceleration through regeneration. Because of this, brake temperature rises.

When a vehicle travels on a downhill slope such as that shown inFIG.7, a rise in brake temperature becomes high when the battery is in a fully charged state and the driver request is to maintain a constant speed.

Flow Chart

FIG.9is a flow chart showing an operation of a brake protection control of a braking control device for a vehicle (a vehicle) in accordance with an embodiment.

In step S1, the ECU13(brake protection controller) determines whether braking control has begun while the vehicle1is travelling. In the case where the braking control does not start while vehicle1is travelling, the process of the flow chart ends.

When the braking control has begun, the estimated temperature calculator110(brake temperature estimator) of the VSA modulator100(seeFIG.2) calculates, in step S2, estimated temperature of the friction brake8(seeFIG.1) based on the calculated initial estimated temperature103, brake fluid pressure104, and vehicle speed105.

In step S3, the SOC information obtaining part50(seeFIG.2) obtains an amount of charge (state of charge, SOC) of the battery4(seeFIG.1) and introduces the amount of charge to the VSA modulator100(seeFIG.2) as a new control parameter.

In step S4, the ECU13(brake protection controller) sets a brake temperature at which a decline in effectiveness of the friction brake8is permissible as a threshold temperature and varies the threshold temperature according to the amount of charge of the battery4.

In step S5, the ECU13sets the ACC prohibit threshold121, a threshold at which the VSA modulator100prohibits the ACC, and the ACC return threshold122, a threshold at which the VSA modulator100returns the ACC, based on the amount of charge of the battery4(state of charge, SOC).

In step S6, the estimated temperature comparing part120(brake protection controller) of the VSA modulator100compares the estimated temperature of the friction brake8that has been estimated by the estimated temperature calculator110with the ACC prohibit threshold121and ACC return threshold122. When the estimated brake temperature exceeds either of or both of the threshold temperatures (the ACC prohibit threshold121and ACC return threshold122), the estimated temperature comparing part120(brake protection controller) sets up a temperature rise flag123.

In step S7, the ACC-ECU200determines whether the temperature rise flag123has been set up by the VSA modulator100based on the friction brake temperature and the amount of charge of the battery4. When the temperature rise flag123has not been set up, the process of the flow chart ends.

When the temperature rise flag123has been set up, the ACC-ECU200, in step S8, sets an ACC set condition201according to the temperature rise flag123and sets an ACC cancel condition202according to the temperature rise flag123and ends the process of the flow chart.

In this way, the ECU13(brake protection controller) sets up a flag when the brake temperature that has been estimated by the estimated temperature calculator110exceeds a threshold temperature (at least one of the ACC prohibit threshold121or the ACC return threshold122) and prohibits an operation of the VSA modulator100(braking controller).

Advantageous Effect

The object of the disclosure is to provide a braking control device for a vehicle and a vehicle capable of braking control that enable a driver of the vehicle to recognize a current operational state of a brake.

An embodiment according to the disclosure enables a driver to recognize the current operational state of the brake.

As described above, a vehicle1(braking control device for a vehicle) according to an embodiment (seeFIG.1) includes the following braking means for applying a braking force to the rotations of the left and right front wheels7and left and right rear wheels3: a regenerative brake by a rotating electric machine2; and a friction brake8that is a mechanical brake. The vehicle1according to the embodiment also includes an SOC information obtaining part50that obtains an amount of charge (SOC) of a battery4of the vehicle1and an ECU13(brake protection controller). The ECU13includes a VSA modulator100and an ACC-ECU200(FIG.2) that generate a regenerative braking force (with the regenerative brake by the rotating electric machine2) and a friction braking force (with the friction brake8) without a braking operation of the driver. The ECU13prohibits an operation of the VSA modulator100or an operation of the ACC-ECU200or operations of the VSA modulator100and ACC-ECU200according to a temperature of the friction brake8and an amount of charge (state of charge, SOC) of a battery4of the vehicle1. The prohibiting of operation by the ECU13includes, for example, disabling at least one of an operation of the VSA modulator100or an operation of the ACC-ECU200or cancelling at least one of a running operation of the VSA modulator100or a running operation of the ACC-ECU200.

Through the configuration described above, the vehicle1according to an embodiment performs brake protection control not only based on brake temperature (as is the case with conventional technology), but also on a state of charge (SOC) of the battery4. In one or more embodiments, a slope descent is determined based on a change (an increase) in the SOC, and an ACC function is terminated in accordance with the SOC and a determination of a slope descent. In this way, the driver is able to recognize the current operational state of the brake. For example, a vehicle1according to an embodiment can lessen in advance a decline in braking effectiveness when the driver presses down on the brake pedal after the vehicle1has been travelling continuously on a downhill slope, thereby preventing an unexpected brake feel.

In one or more embodiments, the ECU13sets an ACC prohibit threshold121and ACC return threshold122, which are used by the VSA modulator100to prohibit the ACC and return the ACC respectively, based on the amount of charge (SOC) of the battery4. The ACC prohibit threshold121and ACC return threshold122are control parameters that have been used in conventional technology, although in conventional technology the amount of charge (SOC) of the battery4is not taken into account in said control parameters. Because of this, the brake protection control according to an embodiment is usable as an extension to conventional control methods, is versatile, and is applicable at a low cost and without requiring a system change.

The ECU13(brake protection controller) of a vehicle1(braking control device for a vehicle) according to an embodiment prohibits an operation of the VSA modulator100(braking controller) or an operation of the ACC-ECU200(braking controller) or operations of the VSA modulator100and ACC-ECU200when a temperature of the friction brake8is equal to or greater than a predetermined temperature and an amount of charge (SOC) of the battery4is equal to or greater than a predetermined amount.

As shown inFIG.8, when the battery4is fully charged, the regenerative brake cannot operate and braking can be performed by the friction brake8only. By cancelling automated driving or the like before the rise in brake temperature becomes large, the vehicle1according to an embodiment enables the driver to recognize the operational state of the brake.

The ECU13(brake protection controller) of a vehicle1(braking control device for a vehicle) according to an embodiment operates the regenerative brake until the amount of charge (state of charge, SOC) of the battery4reaches a second predetermined amount that is greater than a first predetermined amount when a temperature of the friction brake8is greater or equal to a predetermined temperature and the amount of charge (state of charge, SOC) of the battery4is greater or equal to the first predetermined amount.

Ordinarily, in order to protect the battery4, an SOC of approximately 80% (the first predetermined amount) is considered to indicate a fully charged battery4(for example, a driver of the vehicle1is given indication that the battery4is fully charged when the SOC is approximately 80%), and regenerative braking is discontinued thereat. However, because the battery4is still functionally capable of recharging, regeneration is continued until the SOC reaches 90% (the second predetermined amount), thereby protecting the friction brake8(in other words, priority is given to protecting the friction brake8over protecting the battery4). In this way, the driver is capable of recognizing the current operational state of the brake more clearly.

The ECU13(brake protection controller) of a vehicle1(braking control device for a vehicle) according to an embodiment determines that the vehicle1is travelling on a downhill slope when the amount of charge (state of charge, SOC) of the battery4increases successively.

For example, by determining a downhill slope ofFIG.5, when the vehicle1according to an embodiment is the following vehicle (ACC) ofFIG.6, brake protection control can be applied promptly and the rise in brake temperature that arise from a following vehicle (ACC) using ACC can be suppressed more quickly.

The ECU13(brake protection controller) of a vehicle1(braking control device for a vehicle) according to an embodiment sets a brake temperature at which a decline in effectiveness of the friction brake8is allowable as a threshold temperature and varies the threshold temperature according to the amount of charge (SOC) of the battery4. When the brake temperature that has been estimated by the estimated temperature calculator110exceeds the threshold temperature, the ECU13sets a flag up and prohibits an operation of the VSA modulator100(braking controller) or an operation of the ACC-ECU200(braking controller) or operations of the VSA modulator100and ACC-ECU200(braking controller). The prohibiting of operation by the ECU13(brake protection controller) includes, for example, disabling an operation of the VSA modulator100(braking controller) or an operation of the ACC-ECU200(braking controller) or operations of the VSA modulator100and ACC-ECU200(braking controller) or cancelling a running operation of the VSA modulator100(braking controller) or a running operation of the ACC-ECU200(braking controller) or running operations of the VSA modulator100and ACC-ECU200(braking controller).

In this way, the ECU13(brake protection controller) disables an operation of the VSA modulator100and/or an operation of the ACC-ECU200(disables an operation of the braking controller) or cancels a running operation of the VSA modulator100and/or a running operation of the ACC-ECU200(cancels a running operation of the braking controller).

The above embodiments have been described with details provided to aid the understanding of the disclosure. Embodiments of the disclosure are not limited to those with all the described configurations. For example, the embodiments have been described using a downhill slope as an example but are applicable to flat roads as well.