Brake control device

Abstract

The present invention provides a brake control device that appropriately decelerates and suppresses the intervention of anti-lock brake control even when the friction coefficient of the road surface is locally reduced. The brake control device comprises: a target vehicle speed setting unit (11) that sets a target position in front of the vehicle and sets a target vehicle speed when arriving; a brake control unit (12) that controls the braking force of the brake device in such a way that the vehicle speed of the vehicle when arriving at the target position is the target vehicle speed; a low friction coefficient area recognition unit (21) that recognizes a low friction coefficient area where the friction coefficient of the road surface between the current position of the vehicle and the target position is locally lower than that of other areas, and the brake control unit is configured to estimate the maximum deceleration when the vehicle is decelerated to the target vehicle speed at the target position after starting braking after passing through the low friction coefficient area, and when the maximum deceleration is less than a predetermined deceleration upper limit value, start generating the braking force after passing through the low friction coefficient area.

Description

Technical Field

[0001] The present invention relates to a brake control device for controlling a brake device (brake device) of a vehicle such as an automobile. Background Art

[0002] In the braking system of a car or other vehicle, if the rotation of the wheel is locked (locked) due to excessive braking force relative to the friction between the tire and the road surface, the steering of the vehicle fails, and the steering stability is impaired due to the cause of skidding, so anti-lock braking control is performed to suppress the locking of the wheel.

[0003] The anti-lock brake control monitors the rotation speed of each wheel, and when wheel locking or a precursor thereof is detected, the braking force of the wheel is periodically increased or decreased to achieve recovery of wheel rotation.

[0004] As a prior art for suppressing skidding during vehicle driving and ensuring the steering stability of the vehicle, for example, Patent Document 1 records: during acceleration or turning, engine torque control, throttle control and brake control are performed when passing over a metal structure on the road surface, and the acceleration of the vehicle is controlled to suppress the occurrence of skidding and / or idling.

[0005] Prior art literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-20293 Summary of the invention

[0007] Technical issues

[0008] Even during normal driving without emergency braking, the anti-lock braking control may intervene instantaneously when there is a low friction coefficient (μ) area on a part of the road surface, such as a wet metal structure (sewer, etc.) and / or ice slabs (ice cubes).

[0009] For example, when the vehicle is automatically braked for a target object such as a stop line during driving based on automatic driving control, if the vehicle passes over a wet metal structure, the anti-lock brake control will intervene instantly, resulting in a longer stopping distance.

[0010] In addition, the deceleration of the vehicle body increases or decreases suddenly, or the operating noise and / or vibration of equipment caused by the anti-lock brake control are generated, which may cause discomfort and anxiety to the occupants.

[0011] In view of the above problems, an object of the present invention is to provide a brake control device that appropriately decelerates the vehicle and suppresses intervention of anti-lock brake control even when the friction coefficient of the road surface decreases locally.

[0012] Technical Solution

[0013] The present invention solves the above-mentioned problems by the following solutions.

[0014] The invention of method 1 is a braking control device, characterized in that it comprises: a target vehicle speed setting unit, which sets a target position in front of the vehicle and sets a target vehicle speed when the vehicle reaches the target position; a braking control unit, which controls the braking force of the braking device in such a way that the vehicle speed when the vehicle reaches the target position becomes the target vehicle speed; and a low friction coefficient area recognition unit, which recognizes a low friction coefficient area in which the friction coefficient of the road surface between the current position of the vehicle and the target position is locally lower than that of other areas, the braking control unit estimates the maximum deceleration when decelerating from the target position to the target vehicle speed after braking is started after passing through the low friction coefficient area, and when the maximum deceleration is below a predetermined deceleration upper limit, the braking force is started after passing through the low friction coefficient area.

[0015] Therefore, by starting to generate braking force after the vehicle passes through the low friction coefficient area, wheel locking caused by passing through the low friction coefficient area under braking is suppressed, anti-lock braking control intervenes, and it is possible to prevent discomfort to the occupants or the generation of equipment-like operating noise and / or vibration caused by the anti-lock braking control.

[0016] Furthermore, by performing the above control only when the maximum deceleration at this time is equal to or less than a predetermined deceleration upper limit value, it is possible to prevent sudden deceleration from causing occupants to feel uneasy.

[0017] The invention of method 2 is a brake control device according to method 1, characterized in that the brake control device includes a subsequent vehicle identification unit for identifying a subsequent vehicle, and when the brake control unit identifies the subsequent vehicle, the brake control unit reduces the deceleration upper limit value compared to a case where the subsequent vehicle is not identified.

[0018] Thus, by limiting the deceleration when a following vehicle is recognized, it is possible to suppress the risk of the occupants of the following vehicle feeling uncomfortable or uneasy, or being damaged by a rear-end collision with the following vehicle.

[0019] The invention of method 3 is a braking control device according to method 1 or 2, characterized in that when the maximum deceleration exceeds the deceleration upper limit value, the braking control unit starts to generate braking force from the front side of the low friction coefficient area, and moves the position where the braking force starts to be generated in the direction away from the target position relative to the situation where the low friction coefficient area is not identified, and reduces the maximum deceleration during deceleration.

[0020] Thus, when braking is started after passing through the low friction coefficient region and emergency deceleration occurs, slow deceleration is performed in front of the low friction coefficient region, thereby preventing anti-lock brake control from intervening in the low friction coefficient region and appropriately performing deceleration.

[0021] The invention of mode 4 is a braking control device, characterized in that it comprises: a target vehicle speed setting unit, which sets a target position in front of the vehicle and sets a target vehicle speed when the vehicle reaches the target position; a braking control unit, which controls the braking force of the braking device in such a way that the vehicle speed when the vehicle reaches the target position reaches the target vehicle speed; and a low friction coefficient area recognition unit, which recognizes a low friction coefficient area through which the vehicle passes and whose friction coefficient is locally lower than that of other areas during the control of the braking force, and when the braking control unit recognizes the low friction coefficient area, the braking control unit moves the position where the braking force is started to be generated in a direction away from the target position at a position further ahead of the low friction coefficient area than when the low friction coefficient area is not recognized, and reduces the maximum deceleration during deceleration.

[0022] Thus, based on the recognition of the low friction coefficient region passed during braking, the vehicle can be decelerated slowly from the front side of the low friction coefficient region, thereby preventing the anti-lock brake control from intervening in the low friction coefficient region and appropriately performing deceleration.

[0023] The invention of method 5 is a braking control device according to claim 3 or 4, characterized in that the low friction coefficient area identification unit has a function of calculating the estimated friction coefficient of the low friction coefficient area, and the braking control unit, when the estimated friction coefficient is below a predetermined lower limit value of the friction coefficient, reduces the deceleration after starting to generate the braking force and before passing through the low friction coefficient area, and increases the deceleration after passing through the low friction coefficient area.

[0024] Therefore, in a case where the friction coefficient in the low friction coefficient area is particularly low, and if the deceleration is constantly maintained at a level that does not intervene in the anti-lock braking control in the low friction coefficient area, the braking distance will be too long, the deceleration can be reduced when passing through the low friction coefficient area and increased after passing through the low friction coefficient area, thereby achieving both prevention of anti-lock braking control intervention and ensuring the braking distance.

[0025] The invention of method 6 is a brake control device according to claim 5, characterized in that the brake control device includes a subsequent vehicle identification unit for identifying a subsequent vehicle, and when the brake control unit identifies the subsequent vehicle, the brake control unit increases the lower limit value of the friction coefficient compared to a case where the subsequent vehicle is not identified.

[0026] Thus, slow braking is performed in the presence of a following vehicle, thereby preventing the passengers of the following vehicle from feeling uncomfortable.

[0027] The invention of method 7 is a braking control device, characterized in that it comprises: a target vehicle speed setting unit, which sets a target position in front of the vehicle and sets a target vehicle speed when the vehicle reaches the target position; a braking control unit, which controls the braking force of the braking device in such a way that the vehicle speed when the vehicle reaches the target position becomes the target vehicle speed; and a low friction coefficient area identification unit, which identifies a low friction coefficient area through which the vehicle passes and whose friction coefficient is locally lower than that of other areas during the control of the braking force, and when the braking control unit identifies the low friction coefficient area, reduces the deceleration before passing through the low friction coefficient area and increases the deceleration after passing through the low friction coefficient area.

[0028] Thus, by reducing the deceleration when passing through the low friction coefficient region during braking and increasing the deceleration after passing through, it is possible to achieve both prevention of intervention of the anti-lock brake control and securing of the braking distance.

[0029] Technical Effects

[0030] As described above, according to the present invention, it is possible to provide a brake control device that appropriately decelerates the vehicle and suppresses intervention of anti-lock brake control even when the friction coefficient of the road surface is locally reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a block diagram schematically showing the configuration of an embodiment of a brake control device to which the present invention is applied.

[0032] Figure 2 It is a flowchart showing the operation of the brake control device according to the embodiment.

[0033] Figure 3 It is a diagram schematically showing the positional relationship between the low μ region, the braking start position, and the braking end position in each braking control of the brake control device according to the embodiment.

[0034] Figure 4 1 is a diagram schematically showing changes in deceleration corresponding to the travel distance of the vehicle when the brake start delay control of the brake control device according to the embodiment is executed.

[0035] Figure 5 1 is a diagram schematically showing changes in deceleration corresponding to the travel distance of the vehicle when the deceleration reduction control of the brake control device according to the embodiment is executed.

[0036] Figure 61 is a diagram schematically showing changes in deceleration corresponding to the travel distance of the vehicle when the deceleration change control of the brake control device according to the embodiment is executed. DETAILED DESCRIPTION

[0037] Hereinafter, an embodiment of a brake control device to which the present invention is applied will be described.

[0038] The brake control device of the embodiment is provided as a part of an automatic driving control device of a vehicle such as a passenger car having an engine-electric hybrid powertrain.

[0039] Figure 1 It is a block diagram schematically showing the configuration of the brake control device according to the embodiment.

[0040] The automatic driving control device 1 including the brake control device is configured to include an automatic driving control unit 10, an environment recognition unit 20, an engine control unit 30, a motor generator control unit 40, a transmission control unit 50, a steering control unit 60, a hydraulic control unit 70, and the like.

[0041] Each unit is configured to have an information processing unit such as a CPU, a storage unit such as a RAM and / or ROM, an input / output interface, and a bus connecting these, and can communicate with each other via an in-vehicle LAN such as a CAN communication system, or by direct connection.

[0042] The automatic driving control unit 10 issues instructions to each unit based on the result of the recognition of the environment around the host vehicle obtained by the environment recognition unit 20, so as to make the vehicle travel automatically.

[0043] The automatic driving control unit 10 includes a target driving state generating unit 11 , a braking control unit 12 , and the like.

[0044] The target driving state generation unit 11 generates an automatic driving scenario (target driving state change plan) based on the recognition result of the environment recognition unit 20. The automatic driving scenario includes information related to the vehicle state, such as the target driving trajectory of the vehicle and the target vehicle speed at each point on the target driving trajectory.

[0045] The automatic driving control unit 10 issues instructions to each unit to perform driving actions of the vehicle so that the vehicle travels faithfully according to the automatic driving scenario generated by the target driving state generation unit 11 .

[0046] The target traveling state generating unit 11 functions as a target vehicle speed setting unit in the present invention.

[0047] The brake control unit 12 sequentially controls whether or not to generate a braking force on the vehicle, the magnitude of the braking force when the braking force is generated, and the like.

[0048] In an embodiment, the vehicle coordinates control of a service brake having a hydraulic disc brake and a regenerative brake using a regenerative power generation function of an electric generator, thereby controlling the electric generator control unit 40 and the hydraulic control unit 70 in a manner that makes the actual deceleration of the vehicle consistent with the target deceleration set by the brake control unit 12.

[0049] The environment recognition unit 20 recognizes the environment around the vehicle using sensors mounted on the vehicle and / or road-to-vehicle communication, vehicle-to-vehicle communication, and the like.

[0050] The environment recognition unit 20 has a low μ (friction coefficient) region recognition portion 21 .

[0051] The low μ area recognition unit 21 identifies whether there is a low μ area on the target driving trajectory of the vehicle where the friction coefficient (μ) is locally lowered relative to other road surfaces based on information related to the environment surrounding the identified vehicle, and calculates the relative position and estimated friction coefficient of the vehicle if it is identified.

[0052] For example, a region where μ is so low that the anti-lock brake control intervenes due to the braking force in the brake control under normal autonomous driving control (normal brake control) is identified as a low μ region.

[0053] The presence of the low μ region can be determined by, for example, performing image processing on an image captured by an imaging device such as the stereo camera device 22 .

[0054] In addition, the low μ area can be identified based on information obtained through communication with a ground station owned by a road manager or the like (roadside-to-vehicle communication).

[0055] Alternatively, the low μ area may be identified based on information obtained through communication with another vehicle that has passed through the low μ area before the own vehicle (inter-vehicle communication).

[0056] As a method of estimating the friction coefficient (μ), for example, when determining the attributes of the low μ region (wet metal structure, ice, snow, etc.) by image processing or the like, a value preset for each attribute can be used as the estimated μ.

[0057] Furthermore, when the tire slip state (such as the operating state of the ABS and / or traction control or behavior control device) can be obtained from another vehicle passing through the low μ area through inter-vehicle communication, the estimated μ is obtained based on the information.

[0058] The environment recognition unit 20 is connected to a stereo camera device 22 , a road-to-vehicle communication device 23 , a vehicle-to-vehicle communication device 24 , a rear radar 25 , and the like.

[0059] The stereo camera device 22 includes a pair of cameras that are arranged so as to be separated in the vehicle width direction with their imaging ranges directed toward the front of the vehicle, and an image processing unit that performs known stereo image processing on images captured by the cameras.

[0060] The stereo camera device 22 can recognize the low friction coefficient area through image processing and calculate the relative position of the low friction coefficient area with respect to the host vehicle.

[0061] The road-to-vehicle communication device 23 communicates with a ground station installed by a road manager or the like, and acquires information on the position of the low friction coefficient area and its estimated friction coefficient.

[0062] The inter-vehicle communication device 24 communicates with a road-to-vehicle communication device installed in another vehicle, and acquires information on the position of the low friction coefficient area passed by the other vehicle, the estimated friction coefficient, and the like.

[0063] The rear radar 25 is a millimeter wave radar arranged toward the rear of the host vehicle.

[0064] The rear radar 25 is a following vehicle recognition unit having a function of recognizing a following vehicle that is following the own vehicle at the rear side of the own vehicle.

[0065] In addition, in some cases, other sensors such as a millimeter wave radar device or a laser scanning device (LIDAR) disposed toward the front of the vehicle may be connected to the environment recognition unit 20 .

[0066] The engine control unit 30 performs centralized control of an engine serving as a first driving power source of the vehicle and its auxiliary equipment.

[0067] The engine control unit 30 has a function of adjusting the output of the engine so that the actual output torque of the engine matches the requested torque issued from the automatic driving control unit 10 during the automatic driving control of the vehicle.

[0068] As the engine, for example, an internal combustion engine other than a four-stroke direct injection gasoline engine can be used.

[0069] The motor generator control unit 40 performs overall control of the motor generator as a second driving power source of the vehicle and its auxiliary equipment.

[0070] As the motor generator, for example, a rotating electrical machine such as a permanent magnet synchronous motor can be used.

[0071] The motor generator control unit 40 has a function of adjusting the output of the motor generator so that the actual output torque of the motor generator matches the requested torque issued from the automatic driving control unit 10 during the automatic driving control of the vehicle.

[0072] Furthermore, the motor generator can also be used as a regenerative brake that is controlled in coordination with the hydraulic brake by utilizing torque absorption based on regenerative power generation.

[0073] At this time, the motor generator control unit 40 has a function of controlling the amount of regenerative power generated by the motor generator in accordance with the requested braking force from the brake control unit 12 of the automatic driving control unit 10 .

[0074] The transmission control unit 50 centrally controls the transmission (gearbox) and auxiliary equipment thereof, which changes the speed of the output of the engine and the motor generator and transmits the output to each driving wheel.

[0075] The transmission control unit 50 controls the gear ratio of the transmission mechanism, the engagement force of the lockup clutch of the torque converter provided at the input part from the engine, the engagement force of the transfer clutch of the AWD transfer case that distributes the driving force to the front wheels and the rear wheels, etc. according to the instructions from the automatic driving control unit 10 and / or the driving status of other vehicles.

[0076] The steering control unit 60 centrally controls an electric steering device that drives a steering gear box that steers the direction of the front wheels of the vehicle through an electric actuator such as an electric motor, and its auxiliary equipment.

[0077] During automatic driving of the vehicle, the electric power steering device is controlled so that the actual steering angle coincides with the target steering angle issued from the automatic driving control unit 10 .

[0078] The hydraulic control unit 70 is a hydraulic pressure generating device having a function of controlling the wheel cylinder hydraulic pressure of a hydraulic service brake such as a disc brake for each wheel.

[0079] The hydraulic control unit 70 is configured to include, for example, an electric pump for pressurizing the brake fluid, and a pressure-increasing valve, a pressure-reducing valve, and the like for adjusting the hydraulic pressure of each wheel cylinder.

[0080] The hydraulic control unit 70 has a function of controlling the wheel cylinder hydraulic pressure of each wheel based on the target braking force issued from the automatic driving control unit 10 to generate and change the braking force.

[0081] When the hydraulic control unit 70 detects wheel locking (rotation lock) or a precursor thereof during braking, it performs anti-lock braking control for periodically increasing and decreasing the wheel cylinder hydraulic pressure of the wheel to change the braking force and restore the rotation of the wheel.

[0082] The brake control device of the present embodiment performs the control described below to suppress intervention of anti-lock brake control when the vehicle passes through a low μ region where μ of the road surface is locally lower than other portions during braking in an automatic driving operation.

[0083] Figure 2 It is a flowchart showing the operation of the brake control device according to the embodiment.

[0084] Below, each step is described in order.

[0085] <Step S01: Determine the braking plan for automatic driving>

[0086] The automatic driving control unit 10 determines whether braking is planned in the automatic driving scenario generated by the target driving state generating unit 11 .

[0087] For example, braking is planned when the vehicle stops at a red light, a stop sign, or the like, or when the vehicle decelerates when entering a corner (curve).

[0088] The target position at the end of braking and the target vehicle speed at the end of braking are set according to the braking plan.

[0089] For example, when the vehicle stops at a red light, the target position at the end of braking is the position where the front end of the vehicle body is about to reach the stop line, and the target vehicle speed at the end of braking is zero (stop).

[0090] If braking based on automatic driving is planned, the process proceeds to step S02 , and in other cases, the series of processes is terminated (return).

[0091] <Step S02: Determine and identify low μ area>

[0092] The automatic driving control unit 10 determines whether the low μ region recognition unit 21 of the environment recognition unit 20 recognizes the low μ region passed through during braking when the normal braking control is executed.

[0093] If the low μ region identifying unit 21 identifies a low μ region, the process proceeds to step S03 . Otherwise, the process proceeds to step S09 .

[0094] <Step S03: Calculating the maximum deceleration when braking is started after passing through the low μ region>

[0095] The automatic driving control unit 10 calculates the maximum deceleration assumed when the target position at the end of braking reaches the target vehicle speed at the end of braking after the low μ region is passed and braking is started.

[0096] Then proceed to step S04.

[0097] <Step S04: Setting the deceleration upper limit value according to the presence or absence of a following vehicle>

[0098] The automatic driving control unit 10 sets a deceleration upper limit value permitted when executing a brake start delay control in which braking is started after passing through a low μ region.

[0099] The deceleration upper limit value is set in advance in consideration of, for example, the vehicle being in an emergency braking state and causing unstable behavior, or causing discomfort or uneasiness to the occupants.

[0100] In addition, when the rear radar 25 identifies a following vehicle following the vehicle at a vehicle-to-vehicle distance less than a predetermined value, the deceleration upper limit value is set lower than when no following vehicle is identified in order to suppress the risk of rear-end damage caused by the following vehicle.

[0101] Then proceed to step S05.

[0102] <Step S05: Comparing the maximum deceleration with the deceleration upper limit value>

[0103] The automatic driving control unit 10 compares the maximum deceleration obtained in step S03 with the deceleration upper limit value set in step S04 .

[0104] When the maximum deceleration is equal to or less than the deceleration upper limit value, the process proceeds to step S10 , and otherwise, the process proceeds to step S06 .

[0105] <Step S06: Estimating μ in low μ region>

[0106] The low μ region recognition unit of the environment recognition unit 20 estimates μ of the low μ region by the above-described method, and obtains the estimated μ.

[0107] Then proceed to step S07.

[0108] <Step S07: Setting μ lower limit value according to presence or absence of following vehicle>

[0109] The automatic driving control unit 10 sets a lower limit value (μ lower limit value) of the estimated μ in the low μ region allowed for executing the deceleration reduction control.

[0110] The μ lower limit is set in consideration of the fact that μ is low in the low μ region and that the braking distance is too long and impractical when deceleration is performed while maintaining a low deceleration rate such that the antilock brake control does not intervene in the low μ region.

[0111] In particular, when there is a following vehicle, such slow deceleration may give a sense of discomfort or uneasiness to the occupants of the following vehicle, so the μ lower limit value is set higher than when there is no following vehicle.

[0112] Then proceed to step S08.

[0113] <Step S08: Comparison of estimated μ and μ lower limit value>

[0114] The automatic driving control unit 10 compares the estimated μ obtained in step S06 with the μ lower limit value set in step S07 .

[0115] When the estimated μ is equal to or greater than the μ lower limit value, the process proceeds to step S11 , and otherwise, the process proceeds to step S12 .

[0116] <Step S09: Execute normal braking control>

[0117] The brake control unit 12 of the automatic driving control unit 10 performs normal brake control.

[0118] It should be noted that this control and each control described below will be described in detail later.

[0119] Then, a series of processing is ended.

[0120] <Step S10: Executing brake start delay control>

[0121] The brake control unit 12 of the automatic driving control unit 10 executes a brake start delay control that delays the start of braking relative to the normal brake control and starts braking after passing through the low μ region.

[0122] Then, a series of processing is ended.

[0123] <Step S11: Execute deceleration reduction control>

[0124] The brake control unit 12 of the automatic driving control unit 10 executes a deceleration reduction control that starts braking earlier than normal braking control and performs braking at a deceleration lower than that of normal braking control to such an extent that the anti-lock braking control is not intervened in the low μ region.

[0125] Then, a series of processing is ended.

[0126] <Step S12: Execute deceleration change control>

[0127] The braking control unit 12 of the automatic driving control unit 10 performs a deceleration change control, which causes the braking start to be advanced relative to the normal braking control, and brakes at a deceleration that can intervene in the anti-lock braking control in the low μ area, and temporarily suppresses the deceleration to a level where the anti-lock braking control does not intervene before passing through the low μ area, and then increases the deceleration after passing through the low μ area.

[0128] Then, a series of processing is ended.

[0129] Hereinafter, the above-mentioned brake start delay control, deceleration reduction control and deceleration variation control will be described in more detail.

[0130] Figure 3 1 is a diagram schematically showing the positional relationship between the low μ region, the braking start position, and the braking end position in each braking control of the brake control device according to the embodiment.

[0131] Figure 4 , Figure 5 , Figure 6 The diagram schematically shows changes in deceleration corresponding to the travel distance of the vehicle when the brake start delay control, the deceleration reduction control, and the deceleration change control of the brake control device according to the embodiment are executed.

[0132] exist Figure 4 , Figure 5 , Figure 6 In the figure, the horizontal axis represents the travel distance, and the vertical axis represents the deceleration (the acceleration acting on the vehicle body in the deceleration direction).

[0133] exist Figure 4 , Figure 5 , Figure 6 In FIG. 1 , the state of normal brake control is indicated by a dotted line.

[0134] Normal braking control is the control usually used when the low μ area is not identified. The braking force is controlled in such a way that a constant target deceleration is maintained during most of the braking period, and the braking force is controlled in such a way that the deceleration increases and decreases approximately linearly over a predetermined time at the beginning and end of braking.

[0135] The braking start position can be obtained by calculation based on the target deceleration, the braking end target position and the braking end target vehicle speed.

[0136] Here, when the low μ region is passed during braking, the anti-lock brake control intervenes, the deceleration of the vehicle body changes suddenly, or driving noise and / or vibration of the device accompanying the execution of the anti-lock brake control are generated, which may cause discomfort or uneasiness to the occupants.

[0137] In this regard, Figure 3 , Figure 4 In the brake start delay control shown, by delaying the braking start position and time relative to the normal braking control, and starting braking (deceleration) after passing through the low μ area, it is possible to reach the target vehicle speed at the end of braking (for example, stopping the vehicle at a stop position) at a substantially constant deceleration at the end of braking target position without intervening anti-lock braking control.

[0138] It should be noted that when executing brake start delay control, although the deceleration increases compared to normal braking control, by setting the deceleration upper limit value, control is performed in a manner that does not produce deceleration exceeding the upper limit value, thereby preventing emergency braking from causing occupants to feel uneasy or making the vehicle behavior unstable.

[0139] In particular, when a following vehicle is recognized, the risk of rear-end damage can be suppressed by suppressing the deceleration upper limit value.

[0140] It should be noted that, in order to suppress the occupant's sense of emergency deceleration in the brake start delay control, it is preferable to adjust the deceleration increase slope ( Figure 4 The inclination of the curve is also corrected toward the gentler side.

[0141] In addition, Figure 3 , Figure 5 In the deceleration reduction control shown, the position and time of starting braking are advanced relative to the normal braking control, and the deceleration during braking is suppressed to a level that does not intervene in the anti-lock braking control in the low μ area, so that the target vehicle speed at the end of braking can be reached at a substantially constant deceleration at the target position at the end of braking without intervening the anti-lock braking control.

[0142] Furthermore, by setting the μ lower limit value, such control is performed when the low μ region is a road surface with extremely low μ, such as a smooth road surface, to prevent the braking distance from being excessively long.

[0143] It should be explained that Figure 5 The deceleration lower limit value is a deceleration that is a threshold value at which anti-lock braking does not intervene when it is assumed that the μ of the road surface in the low μ region is the μ lower limit value.

[0144] In particular, when a following vehicle is recognized, the μ lower limit value is increased, thereby preventing the occupants from feeling uncomfortable or uneasy.

[0145] In addition, Figure 3 , Figure 6 In the deceleration change control shown, the braking start position and time are advanced relative to the normal braking control, and the deceleration (braking force) is reduced before entering the low μ area to a level where the anti-lock braking control does not intervene in the low μ area. After passing through the low μ area, the deceleration (braking force) is increased. As a result, even if μ is low in the low μ area, the braking distance will not be too long, and the target vehicle speed at the end of braking can be achieved at the target position at the end of braking without intervening the anti-lock braking control.

[0146] It should be noted that in the deceleration change control, when the deceleration is reduced by passing through the low μ region and then increased again, the increased deceleration is increased relative to the deceleration before passing through the low μ region. Figure 6 As shown, the deceleration after passing through the low μ region can be set to be the same as the maximum deceleration of the normal braking control.

[0147] In this case, it is possible to suppress the extension of the braking distance due to the temporary reduction of the deceleration.

[0148] In general, in a vehicle that coordinates the regenerative brake using the motor generator and the hydraulic brake, anti-lock brake control often uses a simple hydraulic brake to control the braking force of each wheel with high responsiveness.

[0149] In this regard, according to the present embodiment, intervention of the anti-lock brake control can be suppressed, thereby expanding the braking region using the regenerative brake, increasing the amount of power generation (energy regeneration amount), and improving the energy efficiency of the vehicle.

[0150] (Variation Example)

[0151] The present invention is not limited to the above-described embodiments, and various modifications and / or changes are possible, which are also within the technical scope of the present invention.

[0152] (1) The configurations of the brake control device, the automatic driving control device, and the vehicle are not limited to those of the above-described embodiment, and can be modified as appropriate.

[0153] For example, in the embodiment, the vehicle is an engine-electric hybrid vehicle, but the present invention is not limited thereto, and can also be applied to a vehicle that uses only an engine or an electric motor as a driving power source.

[0154] (2) The method of identifying the low friction coefficient region and estimating the friction coefficient in the embodiment is an example and can be modified as appropriate.

[0155] (3) In the embodiment, the braking control device is configured as a part of the automatic driving control device as an example, and performs braking based on the automatic driving control. However, the present invention is not limited to such automatic driving, and can also be applied to driving assistance devices such as adaptive cruise control that controls the speed of the vehicle following the preceding vehicle.

[0156] (4) In the embodiment, the same brake control device is configured to perform all of the brake start delay control, the deceleration reduction control, and the deceleration variation control. However, the device may be configured to perform only some of these controls.

Claims

1. A brake control device, characterized in that: have: A target vehicle speed setting unit that sets a target position in front of the host vehicle and sets a target vehicle speed when the host vehicle reaches the target position; a brake control unit that controls the braking force of the brake device so that the vehicle speed when the host vehicle reaches the target position becomes the target vehicle speed; as well as The low friction coefficient area recognition unit recognizes a low friction coefficient area having a friction coefficient locally lower than other areas on a road surface between a current position of the host vehicle and the target position, The brake control unit estimates a maximum deceleration when the vehicle decelerates from the target position to the target vehicle speed after starting braking after passing through the low friction coefficient area, and starts generating the braking force after passing through the low friction coefficient area when the maximum deceleration is equal to or less than a predetermined deceleration upper limit value.

2. The brake control device according to claim 1, characterized in that: The brake control device includes a following vehicle identification unit for identifying a following vehicle. The brake control unit, when the following vehicle is recognized, reduces the deceleration upper limit value compared to a case where the following vehicle is not recognized.

3. The brake control device according to claim 1, characterized in that: When the maximum deceleration exceeds the deceleration upper limit value, the braking control unit starts to generate braking force from the front side of the low friction coefficient area, and moves the position where the braking force is started to be generated in the direction away from the target position, and reduces the maximum deceleration during deceleration, compared to a case where the low friction coefficient area is not identified.

4. The brake control device according to claim 2, characterized in that: When the maximum deceleration exceeds the deceleration upper limit value, the braking control unit starts to generate braking force from the front side of the low friction coefficient area, and moves the position where the braking force is started to be generated in the direction away from the target position, and reduces the maximum deceleration during deceleration, compared to a case where the low friction coefficient area is not identified.

5. A brake control device, characterized in that: have: A target vehicle speed setting unit that sets a target position in front of the host vehicle and sets a target vehicle speed when the host vehicle reaches the target position; a brake control unit that controls the braking force of the brake device so that the vehicle speed reaches the target vehicle speed when the vehicle reaches the target position; as well as a low friction coefficient region identifying unit that identifies a low friction coefficient region through which the vehicle passes during the control of the braking force and in which the friction coefficient is locally lower than that of other regions, When the brake control unit identifies the low friction coefficient area, the position where the braking force is started to be generated moves in a direction away from the target position at a position further ahead of the low friction coefficient area than when the low friction coefficient area is not identified, and the maximum deceleration during deceleration is reduced.

6. The brake control device according to any one of claims 3 to 5, characterized in that: The low friction coefficient region identification unit has a function of obtaining an estimated friction coefficient of the low friction coefficient region. The brake control unit reduces the deceleration after starting to generate the braking force and before passing through the low friction coefficient region when the estimated friction coefficient is equal to or less than a predetermined friction coefficient lower limit value, and increases the deceleration after passing through the low friction coefficient region.

7. The brake control device according to claim 6, characterized in that: The brake control device includes a following vehicle identification unit for identifying a following vehicle. The brake control unit increases the friction coefficient lower limit value when the following vehicle is recognized, compared to a case where the following vehicle is not recognized.

8. A brake control device, characterized in that: have: A target vehicle speed setting unit that sets a target position in front of the host vehicle and sets a target vehicle speed when the host vehicle reaches the target position; a brake control unit that controls the braking force of the brake device so that the vehicle speed when the host vehicle reaches the target position becomes the target vehicle speed; as well as a low friction coefficient region identifying unit that identifies a low friction coefficient region through which the vehicle passes during the control of the braking force and in which the friction coefficient is locally lower than that of other regions, When the brake control unit recognizes the low friction coefficient region, it reduces the deceleration before passing through the low friction coefficient region and increases the deceleration after passing through the low friction coefficient region.

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