Brake control device for vehicle

Abstract

To provide a brake control device for a vehicle which can easily resolve, when a parking brake device is in a fixed state, the fixed state while suppressing overload of the drive motor and secure stable travel.SOLUTION: A brake control device for a vehicle comprises: a drive force control part which independently performs drive control of front and rear wheels; a parking brake device; and a control unit which includes at least a parking brake condition determination part and a road surface μ estimation part. The control unit controls the drive force control part to independently perform the drive control of the front and rear wheels based on the determination result of the parking brake condition determination part and the estimation result of the road surface μ estimation part. In a case of a fixed state determination of the parking brake device, the control unit performs the drive restriction of the front wheels and the drive control of the rear wheels when the estimated road surface μ is less than a specified threshold value, and performs the drive control of the front wheels only when the estimated road surface μ is the specified threshold value or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle brake control device that is applied to vehicles such as automobiles, and more particularly to the control of a parking brake device. [Background technology]

[0002] Generally, vehicles such as automobiles are equipped with a parking brake device for, for example, maintaining the vehicle in a parked state. If this type of parking brake device is left in an activated state for a long period of time in an extremely low temperature environment such as in a cold region, freezing may occur between a friction member (such as a brake shoe or brake pad) and a frictioned member (such as a brake drum or brake rotor), causing the friction member to stick. If such sticking occurs in the parking brake device, it may become impossible to release the activated state of the parking brake device.

[0003] In view of this, when this type of sticking occurs in a conventional parking brake device, various techniques have been proposed for eliminating the stuck state, for example, in JP 2010-241271 A.

[0004] The vehicle braking control device disclosed in JP 2010-241271 A and the like is designed to resolve the stuck condition of the parking brake device by generating a braking operation force greater than normal when the parking brake device is stuck due to freezing or the like.

[0005] Furthermore, in a conventional vehicle braking control device, for example, a technology for performing drive control to increase the drive torque when the vehicle starts, thereby resolving the stuck state of the parking brake device, is disclosed, for example, in JP 2014-226975 A.

[0006] Furthermore, in the vehicle braking control device disclosed in JP 2014-226975 A and the like, a technology is disclosed that suppresses the response delay in the rise in deceleration caused by the application of braking torque in response to the rise in acceleration that occurs when the stuck state of the parking brake device is released, thereby suppressing a sudden rise in acceleration. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-241271 A [Patent Document 2] JP 2014-226975 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, even if the conventional vehicle brake control devices disclosed in the above-mentioned JP 2010-241271 A and JP 2014-226975 A are used, it may be difficult to eliminate the stuck state of the parking brake device.

[0009] Furthermore, in a vehicle brake control device disclosed in JP 2014-226975 A and the like, a pre-fill control is performed to reduce the distance between a friction material and a frictioned material. For this reason, the technology disclosed in the publication has a problem in that highly accurate and complicated control is required.

[0010] Generally, parking brake devices applied to vehicles are normally provided to function on the two rear wheels, for example in the case of a general-type four-wheeled vehicle, etc. In addition, among conventional four-wheeled vehicles, in addition to so-called all-wheel drive vehicles that are structured so that all the wheels (four wheels), including the front and rear wheels, can be driven, so-called front-wheel drive vehicles in which the two front wheels are driven, are also widely used.

[0011] Therefore, for example, in an all-wheel drive or front-wheel drive vehicle, if the parking brake device is stuck and the road surface μ is in an extremely low condition (such as a frozen road surface), the vehicle may start moving due to the driving force applied to the front wheels even though the rear wheels are locked due to the stuck parking brake device.

[0012] Thus, if the vehicle starts to move with the rear wheels in a state where they cannot rotate (locked state), there is a problem in that the vehicle cannot run stably.

[0013] In addition, if the vehicle is an all-wheel drive vehicle, the driving force is also transmitted to the rear wheels. However, since the rear wheels are locked and cannot rotate, there is a problem that an overload is generated on the driving source.

[0014] On the other hand, when the parking brake device is released from its stuck state, a driving force is suddenly applied to the rear wheels, which were unable to rotate (locked), which may cause a sudden rise in acceleration. In such a case, there is a problem that the running of the vehicle becomes unstable.

[0015] It is therefore desirable to realize a control that can reliably suppress such a sudden rise in acceleration and ensure stable driving at all times.

[0016] The present invention aims to provide a vehicle braking control device applied to vehicles such as automobiles, which, when a parking brake device is stuck due to freezing or the like, can easily resolve the stuck state while suppressing overload on the vehicle's drive source, and which performs control to ensure stable driving of the vehicle. [Means for solving the problem]

[0017] In order to achieve the above-mentioned object, a vehicle braking control device of one embodiment of the present invention comprises a driving force control unit that controls the driving of the front wheels and the rear wheels separately, a parking brake device that maintains the parked state of the vehicle, and a control unit that includes at least a parking brake state determination unit that determines the state of the parking brake device and a road surface μ estimation unit that estimates the friction coefficient of the road surface, and the control unit controls the driving force control unit to drive and control the front wheels and the rear wheels respectively based on the determination result by the parking brake state determination unit and the estimation result by the road surface μ estimation unit, and in this case, if it is determined that the parking brake device is stuck and the estimated friction coefficient of the road surface is less than a predetermined threshold value, the driving force control unit limits the driving of the front wheels and performs drive control to drive the rear wheels, and if the estimated friction coefficient of the road surface is equal to or greater than a predetermined threshold value, the driving force control unit performs drive control to drive only the front wheels. Effect of the Invention

[0018] According to the present invention, it is possible to provide a vehicle braking control device that, for example, when a parking brake device is stuck due to freezing or the like, can easily resolve the stuck state while suppressing overload on the vehicle's drive source, and performs control that can ensure stable driving of the vehicle. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle equipped with a vehicle brake control device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a block diagram showing a schematic configuration of a vehicle driving control device including a vehicle brake control device according to an embodiment of the present invention; [Diagram 3] 1 is a flowchart showing control of a parking brake device among the operations of a vehicle driving control device including a vehicle brake control device according to an embodiment of the present invention; [Figure 4] 4 is a flowchart showing a sub-sequence of the adhesion removal process in step S8 of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described below with reference to the illustrated embodiments. The drawings used in the following description are schematic, and the dimensional relationship and scale of each component may be different for each component in order to show each component at a size that can be recognized on the drawing. Therefore, the present invention is not limited to the illustrated form with respect to the quantity of each component, the shape of each component, the size ratio of each component, the relative positional relationship of each component, etc. shown in each drawing.

[0021] First, the schematic configuration of a vehicle equipped with a vehicle brake control device according to one embodiment of the present invention and the schematic configuration of a vehicle driving control device including the vehicle brake control device will be described below with reference to Figures 1 and 2. Figure 1 is a schematic configuration diagram of a vehicle equipped with a vehicle brake control device according to one embodiment of the present invention. Figure 2 is a block configuration diagram showing the schematic configuration of a vehicle driving control device including a vehicle brake control device according to one embodiment of the present invention.

[0022] The basic configurations of the vehicle shown in Fig. 1 and the vehicle driving control device shown in Fig. 2 are substantially similar to those of conventional vehicles and vehicle driving control devices of the same type. Therefore, in Fig. 1 and Fig. 2 and the following description, illustration and detailed description of general components in conventional vehicles and vehicle driving control devices are omitted. Only main components directly related to the present invention are illustrated in Fig. 1 and Fig. 2 and will be described below.

[0023] A vehicle driving control device 1 including a vehicle braking control device of this embodiment has a camera unit 10 (see FIG. 2) which is an in-vehicle camera device including a stereo camera 11 fixed to the upper central part near the front of the passenger compartment of a vehicle M (see FIG. 1) in which the vehicle driving control device 1 is mounted.

[0024] In Fig. 1, the arrow F indicates the traveling direction (forward) of the vehicle M. Also in Fig. 1, the arrow FR indicates the front right wheel of the vehicle M. Similarly, the arrow FL indicates the front left wheel of the vehicle M. The arrow RR indicates the rear right wheel of the vehicle M. The arrow RL indicates the rear left wheel of the vehicle M.

[0025] As shown in Fig. 1, braking devices 7F, 7R are provided for each wheel (FR, FL, RR, RL) of a vehicle M. Among them, the braking device 7F is provided for each of the front wheels FR, FL, and the braking device 7R is provided for each of the rear wheels RR, RL.

[0026] These brake devices 7F, 7R are composed of friction members (brake shoes or brake pads, etc.), frictioned members (brake drums or brake rotors, etc.), and actuators that operate the friction members (brake boosters, master cylinders, brake fluid piping, wheel cylinders or brake calipers, etc.; not shown). The configuration example of the brake devices (7F, 7R) shown in Figure 1 is illustrated assuming brake pads as friction members and brake rotors as frictioned members.

[0027] The brake devices (7F, 7R) themselves are assumed to have the same configuration as conventional brake devices, and detailed illustrations and explanations thereof will be omitted.

[0028] The brake device 7R corresponding to the rear wheels RR, RL is also configured to function as a parking brake device. Here, the parking brake device is a device for maintaining the vehicle M in a parked or stopped state.

[0029] In a vehicle M equipped with a vehicle travel control device 1 including the vehicle brake control device of this embodiment, a so-called electric parking brake (EPB) device is applied as a parking brake device. This type of parking brake device has a configuration in which it can be activated by turning on a specific parking brake operation switch, for example, and can be released from the activated state by turning off the switch.

[0030] In this case, an ON signal (hereinafter referred to as a parking brake ON signal) generated by turning on the parking brake operation switch is output to a brake control unit (BK_ECU) 23 described later. Upon receiving the parking brake ON signal, the brake control unit 23 executes control for a brake actuator 33 described later to drive the brake device 7R of the rear wheels RR, RL as a parking brake. As a result, the brake device 7R functions as a parking brake device.

[0031] As shown in Fig. 2, the camera unit 10 is configured to include a stereo camera 11, an image processing unit (referred to as "IPU" in Fig. 2) 12, an image recognition unit 13, and a control unit (referred to as "M_ECU" in Fig. 1) 14. Note that the image processing unit 12 and the image recognition unit 13 are omitted in Fig. 1 to avoid complicating the drawing.

[0032] The stereo camera 11 is formed with two cameras, a main camera 11a and a sub camera 11b. The main camera 11a and the sub camera 11b are arranged, for example, in symmetrical positions with respect to the center in the vehicle width direction in the cabin of the vehicle M, facing the front of the vehicle M (the traveling direction; see arrow F in FIG. 1). Each of the main camera 11a and the sub camera 11b is composed of, for example, an imaging optical system, an imaging element such as a CMOS image sensor, and a processing circuit that processes imaging signals, etc. (detailed configurations are not shown).

[0033] With this configuration, the stereo camera 11 acquires two image data from two different viewpoints targeting a predetermined range of the surrounding environment in front of the vehicle outside at a predetermined imaging period synchronized with each other by the main camera 11a and the sub camera 11b. Then, stereo image data is generated based on the two image data acquired in this manner. This stereo image data is surrounding environment information that represents the surrounding environment while the vehicle M is traveling. The surrounding environment information (image data) generated by the stereo camera 11 is output to the image processing unit 12.

[0034] The image processing unit 12 is a configuration unit or a circuit unit that performs predetermined image processing on the surrounding environment information (image data representing the surrounding environment while the vehicle M is traveling) acquired by the stereo camera 11. The image processing unit 12 performs, for example, processing to detect edges of various objects (objects, lane lines, etc.) displayed on the image.

[0035] The image processing unit 12 also acquires distance information based on the amount of positional shift of corresponding edges on the left and right images based on the stereo image data, and generates image information including the distance information (distance image information). The distance image information generated in the image processing unit 12 is output to the image recognition unit 13.

[0036] The image recognition unit 13 calculates the road curvature [1 / m] of the left and right dividing lines of the road (host vehicle road) on which the vehicle M is traveling, the width between the left and right dividing lines (lane width), etc., based on the distance image information, etc. input from the image processing unit 12. Various well-known means are used to calculate the road curvature and lane width.

[0037] In addition, the image recognition unit 13 performs predetermined pattern matching based on the distance image information acquired by the stereo camera 11 to recognize three-dimensional objects (such as guardrails, curbs, and other surrounding vehicles) extending along the road, parking frame lines marked by dividing lines on the road surface of a parking lot or the like, three-dimensional structures such as car stops that define parking space areas, or gap spaces between adjacent vehicles, etc. In addition, the image recognition unit 13 also recognizes the conditions of the road surface around the vehicle M (hereinafter referred to as road surface conditions, etc.).

[0038] Here, the recognition of three-dimensional objects (object recognition) in the image recognition unit 13 recognizes, for example, the type of three-dimensional object, the height of the three-dimensional object, the width dimension of the three-dimensional object, the distance from the vehicle M to the three-dimensional object, the moving speed of the three-dimensional object, the relative speed between the three-dimensional object and the vehicle M, and the relative distance between three-dimensional objects (for example, the lateral distance between a curb on the side of the road and a dividing line nearby).

[0039] The road surface conditions recognized by the image recognition unit 13 include, for example, a condition in which the road surface is wet due to rain or melting snow, a rainfall condition, a snow accumulation condition, a packed snow condition, a frozen road condition, etc. These road surface conditions are estimated based on, for example, the brightness difference of the images.

[0040] Various pieces of information recognized by the image recognition unit 13 are output as surrounding environment information to the control unit 14. In this case, the camera unit 10 including the image recognition unit 13 functions as a surrounding environment recognition device that recognizes the surrounding environment of the vehicle.

[0041] The control unit 14 included in the camera unit 10 is a configuration unit or circuit unit that controls the camera unit 10 and also comprehensively controls the entire vehicle driving control device 1 including the vehicle brake control device of this embodiment.

[0042] This control unit 14 is connected to various control units, such as a cockpit control unit (CP_ECU) 21, a drive motor control unit (D / M_ECU) 22, and a brake control unit (BK_ECU) 23, via an in-vehicle communication line such as a CAN (Controller Area Network) 40.

[0043] A human-machine interface (HMI) 31 arranged around the driver's seat is connected to the CP_ECU 21. The HMI 31 is configured to include, for example, various operating members, various sensing devices, various alarm devices 31a (denoted as "ALARM" in FIG. 1), and the like.

[0044] Here, the various operating members include, for example, a parking brake operating switch for turning the operation of the parking brake device on and off, an operating switch for instructing the execution and stopping of various driving assistance controls, a mode change switch for switching driving modes, etc.

[0045] In addition, various sensing devices include a steering touch sensor that detects the driver's steering state, a driver monitoring system (DMS) that detects the driver's facial recognition and line of sight, and an in-vehicle monitor system consisting of an in-vehicle camera that recognizes the riding status of passengers including the driver.

[0046] The various notification devices 31a include a touch panel display device (visual display device), a sound output device (auditory display device) including a speaker, etc., and a combination meter combining various instruments.

[0047] The CP_ECU 21 is a structural unit or circuit unit that, upon receiving a control signal from the control unit 14, appropriately notifies the driver of various information (e.g., various alarms, the implementation status of driving assistance control, and various information regarding the surrounding environment of the vehicle M, etc.) in a predetermined form (visual or auditory display) using the notification device 31a included in the HMI 31.

[0048] In addition, the CP_ECU 21 outputs various input information of instruction signals (e.g., on / off instructions for the parking brake device, on / off instructions for various driving assistance controls, etc.) input by the driver using various operating members included in the HMI 31 to the control unit 14.

[0049] The output side of the D / M_ECU 22 is connected to the drive motors (32F, 32R) that are drive sources for the vehicle M. In addition, the input side of the D / M_ECU 22 is connected to various sensors such as an accelerator sensor (not shown).

[0050] Here, the drive motors include a front drive motor (FD / M) 32F and a rear drive motor (RD / M) 32R. The front drive motor 32F is a drive source that drives the front wheels FR, FL through the front axle 3F. The rear drive motor 32R is a drive source that drives the rear wheels RR, RL through the rear axle 3R.

[0051] The D / M_ECU 22 is a configuration unit or circuit unit that controls the drive of the drive motors (32F, 32R) based on control signals from the control unit 14 or detection signals from various sensors. The D / M_ECU 22 functions as a drive force control unit that controls the drive of the front wheels FR, FL and the rear wheels RR, RL separately. The D / M_ECU 22 also outputs signals such as the accelerator opening degree detected by the various sensors to the control unit 14.

[0052] A brake actuator 33 (denoted as "BK_AC" in FIG. 1) is connected to the output side of the BK_ECU 23. The brake actuator 33 is an actuator for adjusting the hydraulic pressure of brake fluid output to pistons in brake wheel cylinders or pistons (not shown) in brake calipers included in the brake devices 7F, 7R provided on each wheel (FR, FL, RR, RL). In addition, various sensors such as a brake pedal sensor, a yaw rate sensor, a longitudinal acceleration sensor, and a vehicle speed sensor (not shown) are connected to the input side of the BK_ECU 23.

[0053] The BK_ECU 23 is a configuration unit or circuit unit that performs vehicle braking control by controlling the drive of the brake actuator 33 based on a control signal from the control unit 14 or detection signals from various sensors. As a result, the BK_ECU 23 appropriately generates braking forces on each wheel (FR, FL, RR, RL) for performing forced braking control, yaw rate control, etc. on the vehicle M. In addition, the BK_ECU 23 outputs signals of the brake operation state, yaw rate, longitudinal acceleration, vehicle speed (host vehicle speed), etc. detected by various sensors to the control unit 14.

[0054] Furthermore, the BK_ECU 23 also has a function of activating the brake device 7R corresponding to the rear wheels RR, RL as a parking brake when the BK_ECU 23 receives an activation signal for the parking brake device.

[0055] In addition, various sensors 17 and a wheel speed sensor 18 are connected to the control unit 14. Here, the various sensors 17 include, for example, a locator unit, an in-vehicle radar device, a rear image sensor, a LiDAR (Light Detection And Ranging) device, a near-infrared sensor, an outside air temperature sensor, and the like, although not shown.

[0056] The wheel speed sensor 18 is a sensor that detects the wheel rotation speed by detecting a pulse signal (wheel speed pulse) that is generated in proportion to the rotation speed of each wheel (FR, FL, RR, RL) of the vehicle M, and thereby detects the vehicle speed of the vehicle M.

[0057] The control unit 14 executes vehicle driving control based on the various information acquired by the camera unit 10 and the various sensors 17, etc. In this case, the driving control includes, for example, output control of the drive motors (32F, 32R) by the D / M_ECU 22, torque distribution control of each drive wheel, and individual braking control (brake control) of each wheel (FR, FL, RR, RL) by the BK_ECU 23, and is vehicle driving control that is required appropriately.

[0058] Furthermore, as shown in FIG. 2, the control unit 14 includes therein a brake state determination section (denoted as "BK state determination section" in FIG. 1), a road surface μ estimation section 16, and the like.

[0059] The brake state determination unit 15 is a structural unit or circuit unit that determines the operating state of the brake devices (7F, 7R) for each wheel (FR, FL, RR, RL), the operating state of the parking brake device (7R), etc., as well as the state of the parking brake device (7R), such as sticking, based on various information acquired by various sensors 17, etc.

[0060] For example, the brake state determination unit 15 detects or determines the operation state of the parking brake devices (7F, 7R) by detecting an on signal or an off signal of a parking brake operation switch (not shown) included in the HMI 31, for example.

[0061] The brake state determination unit 15 also detects or determines a state such as sticking caused by freezing between a friction member and a frictioned member in the parking brake device (7R). Specifically, the brake state determination unit 15 detects or determines a state such as sticking of the parking brake device (7R) from a detection value of a rotation angle of the drive motor 32R in response to a drive control signal for the drive motor 32R output from the D / M_ECU 22, or a detection value of a wheel speed sensor 18 corresponding to the rear wheels RR, RL.

[0062] The road surface μ estimating unit 16 is a configuration unit or a circuit unit that estimates the friction coefficient of the road surface (hereinafter referred to as road surface μ) based on various information acquired by various sensors 17 and the like.

[0063] Specifically, for example, the road surface μ estimation unit 16 estimates the road surface μ by detecting the degree of spinning of the front wheels FR, FL from the detection value of the rotation angle of the drive motor 32F in response to the drive control signal output from the D / M_ECU 22 to the drive motor 32F, or the detection value of the wheel speed sensor 18 corresponding to the front wheels FR, FL.

[0064] In this case, when estimating road surface μ, the road surface μ estimation unit 16 may further refer to information regarding the road surface conditions recognized by the image recognition unit 13, and detection values ​​of the near-infrared sensor, outside air temperature sensor, etc. included in the various sensors 17.

[0065] The road surface μ estimating unit 16 may use, for example, a luminance difference or the like of the image of the road surface captured by the stereo camera 11 as an auxiliary criterion for determining whether the road surface is a dry road surface, a wet road surface, a snowy road surface, or an icy road surface. In this case, for example, a dry road surface or a wet road surface is determined as an auxiliary criterion for determining that the road surface μ is high, and a snowy road surface or an icy road surface is determined as an auxiliary criterion for determining that the road surface μ is low.

[0066] Alternatively, the road surface μ estimation unit 16 uses a judgment assistance criterion that, for example, when the outside air temperature is equal to or higher than a predetermined threshold, the road surface μ is high, and when the outside air temperature is lower than the predetermined threshold, the road surface μ is low.

[0067] All or some of the image recognition unit 13, control unit 14, brake state determination unit 15, road surface μ estimation unit 16, CP_ECU 21, D / M_ECU 22, BK_ECU 23, etc. are configured by a processor including hardware.

[0068] Here, the processor is configured by a well-known configuration including, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a non-volatile memory, a non-volatile storage device, a non-transitory computer readable medium, and the like, and peripheral devices thereof.

[0069] Software programs executed by the CPU and fixed data such as data tables are stored in advance in the ROM, non-volatile memory, non-volatile storage device, etc. Then, the CPU reads out the software programs stored in the ROM, etc., expands them in the RAM, and executes them, and the software programs appropriately refer to various data, etc., thereby realizing the functions of the above-mentioned components and components (13-16, 21-23), etc.

[0070] The processor may be configured with a semiconductor chip such as a Field Programmable Gate Array (FPGA), etc. Each of the above components and components (13 to 16, 21 to 23) may be configured with an electronic circuit.

[0071] Furthermore, the software program may be in a form in which the whole or part is recorded as a computer program product on a portable disk medium such as a flexible disk, CD-ROM, or DVD-ROM, or on a non-transitory computer readable medium such as a card-type memory, an HDD (Hard Disk Drive) device, or an SSD (Solid State Drive) device.

[0072] Next, the control of the parking brake device among the operations of the vehicle driving control device 1 including the vehicle braking control device of one embodiment of the present invention will be described below. Note that Fig. 3 is a flowchart showing the control of the parking brake device among the operations of the vehicle driving control device including the vehicle braking control device of one embodiment of the present invention. Fig. 4 is a flowchart showing a sub-sequence of the fixation resolution process of step S8 in Fig. 3.

[0073] First, the vehicle M is in a parked state with the parking brake device operating (i.e., the rear wheels RR and RL are braked by the parking brake device (7R)). At this time, the vehicle M is in a system-off state.

[0074] When the vehicle M is in such a state, first, in step S1 in Fig. 3, the control unit 14 checks whether or not a system start instruction signal for the vehicle M has been generated. If it is confirmed that a system start instruction signal for the vehicle M has been generated, the process proceeds to step S2. If a system start instruction signal for the vehicle M has not been generated, the confirmation process of step S1 is repeated.

[0075] Next, in step S2, the control unit 14 checks whether a predetermined signal for releasing the parking brake device from its operating state (hereinafter referred to as a parking brake release signal) has been generated. Here, the parking brake release signal is generated in the following cases. That is, (1) When the driver uses the parking brake operation switch to release the parking brake device, (2) When the driver selects and sets a desired driving range (e.g., D range or R range, etc.) using the selector lever and depresses the accelerator pedal, etc.

[0076] If it is confirmed in step S2 that the parking brake release signal has been generated, the process proceeds to step S3, and if the parking brake release signal has not been generated, the process in step S2 is repeated.

[0077] Next, in step S3, the control unit 14 checks whether or not an instruction signal (hereinafter, referred to as a drive motor on signal) for driving each of the drive motors 32F, 32R is generated. Here, the drive motor on signal is an instruction signal for driving each of the drive motors 32F, 32R, and is a predetermined control signal for controlling each of the drive motors 32F, 32R separately. The drive motor on signal is generated as follows.

[0078] First, the driver depresses the accelerator pedal. Then, an accelerator sensor (not shown) detects the depression of the accelerator pedal (accelerator ON confirmation process). This causes the accelerator sensor to generate a predetermined command signal. The accelerator sensor command signal thus generated is input to the D / M_ECU 22. In response to this accelerator sensor command signal, the D / M_ECU 22 issues a predetermined drive motor ON signal.

[0079] The drive motor on signal is output to each of the drive motors 32F, 32R from the D / M_ECU 22. Upon receiving the drive motor on signal, each of the drive motors 32F, 32R is controlled to be driven.

[0080] If it is confirmed in step S3 that the drive motor ON signal is generated, the process proceeds to step S4, or if the drive motor ON signal is not generated, the process of step S3 is repeated.

[0081] In step S4, the control unit 14 executes a parking brake state confirmation process to confirm the state of the parking brake. Here, the parking brake state confirmation process is a process for confirming whether or not the parking brake device (the brake device 7R of the rear wheels RR, RL) is stuck due to freezing or the like.

[0082] To this end, in the process of step S4, the control unit 14 detects the rotation angles of the front drive motor 32F and the rear drive motor 32R.

[0083] Next, in step S5, the control unit 14, through the brake state determination unit 15, determines whether or not the parking brake device has stuck based on the detection results (the rotation angles of each drive motor 32F, 32R) in the processing of the above-mentioned step S4.

[0084] Here, the detection result of the process in step S4 described above is, for example, (a) There is a change in the rotation angle of the front drive motor 32F, and (b) When there is no change in the rotation angle of the rear drive motor 32R In step S100, it is determined that the brake device 7R for the rear wheels RR, RL has become stuck, and the process proceeds to step S6.

[0085] Otherwise, i.e., (a1) There is a change in the rotation angle of the front drive motor 32F, and (b1) When there is a change in the rotation angle of the rear drive motor 32R In the next step, it is determined that no sticking or the like has occurred in the braking device 7R of the rear wheels RR, RL, and the series of processes is terminated, and the process returns to the predetermined main sequence (RETURN).

[0086] In addition, since a situation in which the parking brake device may become stuck or the like is assumed here, a situation in which there is no change in the rotation angle of the front drive motor 32F is not taken into consideration as it is unlikely to occur.

[0087] In step S6, the control unit 14 executes a predetermined road surface μ estimation process through the road surface μ estimating section 16. The estimation of the road surface μ performed by the road surface μ estimating section 16 is as described above.

[0088] Next, in step S7, the control unit 14 checks whether the road surface μ estimated in the process of step S6 described above is a μ value lower than a predetermined threshold value. If it is confirmed that the estimated road surface μ is a μ value lower than the predetermined threshold value, the process proceeds to step S8. If the estimated road surface μ is a μ value higher than the predetermined threshold value, the process proceeds to step S21 in FIG. 4 (see circle 4 in FIG. 3 and FIG. 4).

[0089] In step S8 of FIG. 3, the control unit 14 controls the driving of the drive motor 32R through the D / M_ECU 22, and executes a process for eliminating the sticking of the parking brake device (the brake device 7R of the rear wheels RR, RL).

[0090] FIG. 4 shows a sub-sequence of the above-mentioned step S8 for removing the stuck state.

[0091] Proceeding to step S8 in FIG. 3, first, in step S11 in FIG. 4, the D / M_ECU 22 of the control unit 14 limits the driving force of the front drive motor 32F (or may cut off the driving force), and at the same time starts control to drive the rear drive motor 32R with a predetermined driving force for a predetermined time (T1).

[0092] The drive control carried out here is a control process that applies a predetermined drive force mainly to the rear wheels RR, RL for a predetermined time (T1) to eliminate the stuck state.

[0093] As described above, the situation at this time is determined to be that the brake device 7R of the rear wheels RR, RL is in a stuck state. Therefore, applying a driving force to the rear wheels RR, RL for a long period of time will overload the rear drive motor 32R. Therefore, taking this into consideration, the drive control of the rear drive motor 32R performed here is limited to a predetermined time (T1) that does not adversely affect the rear drive motor 32R.

[0094] The driving force of the front drive motor 32F is limited (or cut off) for the following reason. As described above, in this situation, the road surface μ is lower than a predetermined threshold value. Therefore, if the driving force of the front drive motor 32F is applied to the front wheels FR, FL at this time, there is a possibility that the vehicle will start moving with the rear wheels RR, RL remaining locked. Therefore, by limiting (or cutting off) the driving force of the front drive motor 32F, the vehicle is prevented from moving.

[0095] The above-mentioned predetermined time (T1) is determined by, for example, referring to an internal clock (not shown) of the control unit 14. For this reason, in the process of step S11 described above, the control unit 14 performs processes such as starting timer timekeeping by the internal clock at the start of the drive control process of the drive motor.

[0096] During the execution of the drive control process in step S11 (during a predetermined time (T1)), the processes in the following steps S12 to S18 intervene.

[0097] That is, when the process of step S11 is started, in step S12, the control unit 14 continuously detects the rotation angle of the rear drive motor 32R at predetermined time intervals.

[0098] Next, in step S13, the control unit 14 continuously checks whether or not a change has occurred in the rotation angle of the rear drive motor 32R for each detection process in step S12 described above. This check process makes it possible to determine whether or not the stuck state of the brake device 7R of the rear wheels RR, RL has been resolved.

[0099] If a change in the rotation angle of the rear drive motor 32R is confirmed, it is determined that the stuck state is being resolved. In this case, the process proceeds to the next step S14. If no change in the rotation angle of the rear drive motor 32R is confirmed, it is determined that the stuck state continues. In this case, the process proceeds to step S18.

[0100] Next, in step S14, the D / M_ECU 22 of the control unit 14 continues to perform control to drive the rear drive motor 32R while suppressing the drive force of the rear drive motor 32R.

[0101] When a change in the rotation angle of the rear drive motor 32R is confirmed in the process of step S13 described above, it can be determined that the stuck state of the parking brake device is being released. When the stuck state of the parking brake device is released, the driving force of the rear drive motor 32R is transmitted to the rear wheels RR, RL. At this time, if the predetermined driving force of the rear drive motor 32R is suddenly transmitted to the rear wheels RR, RL, the vehicle M will suddenly start moving.

[0102] Therefore, when a change in the rotation angle of the rear drive motor 32R is confirmed in the process of step S13 described above, the drive force of the rear drive motor 32R is suppressed in the process of the next step S14. Here, for example, drive control is performed to gradually attenuate the drive force applied to the rear drive motor 32R in response to the change in the rotation angle of the rear drive motor 32R.

[0103] In addition to this, for example, when a change occurs in the rotation angle of the rear drive motor 32R, the drive force of the rear drive motor 32R may be temporarily cut off, and then a drive force that is reduced compared to the previous time may immediately be applied.

[0104] Then, in the next step S15, the control unit 14 detects the rotation angle of the rear drive motor 32R again.

[0105] Next, in step S16, the control unit 14 checks whether the detected value of the rotation angle obtained in the process of step S15 above corresponds to the rotation angle corresponding to the driving force applied to the rear drive motor 32R. In other words, this check makes it possible to check whether the driving force of the rear drive motor 32R is transmitted to the rear wheels RR, RL without resistance. If it is confirmed that the detected value of the rotation angle of the rear drive motor 32R corresponds to the rotation angle corresponding to the driving force applied to the rear drive motor 32R, the process proceeds to the next step S17. If the rotation angle and the driving force do not correspond to each other, the process returns to step S14 and repeats the subsequent processes.

[0106] In step S17, the control unit 14, the D / M_ECU 22, starts drive control during normal driving, in which the front drive motor 32F and the rear drive motor 32R are output with normal drive force distribution and drive force according to the accelerator opening degree. This causes the vehicle M to start driving under normal driving control. After that, the series of processes is ended, and the process returns to the predetermined main sequence (RETURN).

[0107] On the other hand, if it is determined in the process of step S13 that the stuck state continues and the process proceeds to step S18, the control unit 14 checks whether or not a predetermined time (T1) has elapsed in this step S18. If it is confirmed that the predetermined time (T1) has elapsed, the process proceeds to the next step S19. If the predetermined time (T1) has not elapsed, the process returns to the process of step S11 and repeats the subsequent processes.

[0108] Then, in step S19, the control unit 14 controls the notification device 31a included in the HMI 31 through the CP_ECU 21 to display a predetermined notification such as a warning. The notification displayed here is, for example, a notification that the parking brake is stuck. In addition, the notification may also display, for example, a method of resolving the stuck state of the parking brake and the procedure for doing so. Thereafter, the series of processes ends, and the process returns to the predetermined main sequence (RETURN).

[0109] On the other hand, if the estimated road surface μ is higher than the predetermined threshold value in the processing of step S7 in Figure 3, the process proceeds to the processing of step S21 in Figure 4, in which the D / M_ECU 22 of the control unit 14 drives and controls only the front drive motor 32F to drive the vehicle M for a predetermined time (T2).

[0110] At this time, the road surface μ is higher than a predetermined threshold value, so the road surface reaction force is large. Therefore, a driving force is applied to the front wheels FR, FL for a predetermined time (T2) to drive the vehicle M for a predetermined distance. This causes the rear wheels RR, RL to rotate before the static friction force is exceeded, thereby performing control to release the parking brake (7R) from sticking.

[0111] During the execution of the drive control process in step S21 (during a predetermined time (T2)), the processes in the following steps S22 to S24 are carried out.

[0112] That is, when the process of step S21 is started, in step S22, the control unit 14 continues to detect the rotation of the rear wheels RR, RL at predetermined time intervals.

[0113] Next, in step S23, the control unit 14 continuously checks whether the rear wheels RR, RL have rotated or not for each detection process in step S22 described above. This check process makes it possible to determine whether the stuck state of the brake device 7R of the rear wheels RR, RL has been resolved or not.

[0114] If the rotation of the rear wheels RR, RL is confirmed, it is determined that the stuck state has been resolved, and the process proceeds to step S17.

[0115] If the rotation of the rear wheels RR, RL is not confirmed, it is determined that the stuck state continues, and the process proceeds to step S24.

[0116] Next, in step S24, the control unit 14 checks whether or not a predetermined time (T2) has elapsed. If it is confirmed that the predetermined time (T2) has elapsed, the process proceeds to the next step S25. If the predetermined time (T2) has not elapsed, the process returns to the above-mentioned step S21, and the subsequent steps are repeated.

[0117] Then, in step S25, the control unit 14 controls the notification device 31a included in the HMI 31 through the CP_ECU 21 to display a predetermined notification such as a warning. The notification display performed here is the same as the process of step S19 described above. After that, the series of processes is terminated and the process returns to the predetermined main sequence (RETURN).

[0118] As described above, according to the embodiment, a vehicle brake control device applied to a vehicle such as an automobile includes a driving force control unit (D / M_ECU 22) that separately drives and controls the front wheels FR, FL and the rear wheels RR, RL, a parking brake device (brake device 7R) that maintains a parked state of the vehicle M, and a control unit 14 that includes at least a brake state determination unit 15 that determines the state of the parking brake device and a road surface μ estimation unit 16 that estimates the friction coefficient of the road surface. Then, based on the determination result by the brake state determination unit 15 and the estimation result by the road surface μ estimation unit 16, the control unit 14 controls the driving force control unit (22) to drive and control the front wheels FR, FL and the rear wheels RR, RL, respectively.

[0119] In this case, when it is determined that the parking brake device is stuck, if the estimated friction coefficient of the road surface (road surface μ) is less than a predetermined threshold, the driving force control unit (22) performs drive control to limit the drive of the front wheels FR, FL and drive the rear wheels RR, RL. On the other hand, if the estimated friction coefficient of the road surface (road surface μ) is equal to or greater than the predetermined threshold, the driving force control unit (22) performs drive control to drive only the front wheels FR, FL.

[0120] In this manner, in the vehicle brake control device of this embodiment, even if the brake device is stuck due to freezing or the like, the brake device's state is automatically detected, and if it is stuck, a control process for removing the stuck state is automatically executed, so that the stuck state can be more reliably removed.

[0121] Moreover, by performing such drive control, the vehicle brake control device of this embodiment can suppress overload on the rear drive motor 32R. Furthermore, when the estimated road surface μ is low, the drive of the front drive motor 32F is limited, so that the front wheels FR, FL are driven and the vehicle M is prevented from starting to run. Therefore, stable running can be ensured.

[0122] In addition, after starting the drive control of the front wheels FR, FL and the rear wheels RR, RL by the drive force control section (22), the control unit 14 again performs state determination by the brake state determination section 15, and if it is determined that the sticking of the parking brake device has been resolved, the control unit 14 performs drive control to gradually reduce the drive force applied to the rear wheels RR, RL by the drive force control section (22).

[0123] By performing such drive control, the locking is eliminated, and it is possible to suppress abrupt transmission of drive force to the rear wheels RR, RL, which would otherwise cause the vehicle M to suddenly accelerate, thereby ensuring stable running.

[0124] The brake state determination unit 15 further includes an alarm device 31a. When the brake state determination unit 15 determines again that the brake is stuck, the control unit 14 issues a predetermined warning by the alarm device 31a.

[0125] By performing such control, if the parking brake device cannot be resolved by the resolve-stick process, a predetermined warning message can be displayed to the driver, allowing the driver to obtain specific information about the problem occurring in the vehicle and quickly take measures to address the problem.

[0126] The brake state determination unit 15 detects a change in the rotation angle of the rear drive motor 32R that drives the rear wheels RR, RL. Based on the detection information obtained in this way, the brake state determination unit 15 can easily and accurately determine the state of the braking device.

[0127] The present invention is not limited to the above-mentioned embodiment, and various modifications and applications can be implemented within the scope of the gist of the invention. Furthermore, the above-mentioned embodiment includes inventions at various stages, and various inventions can be extracted by appropriate combinations of the disclosed multiple constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the above-mentioned one embodiment, if the problem to be solved by the invention can be solved and the effect of the invention can be obtained, the configuration from which the constituent elements are deleted can be extracted as the invention. Furthermore, the constituent elements across different embodiments may be appropriately combined. The present invention is not restricted by its specific embodiment except as limited by the attached claims.

[0128] For example, in the above-described embodiment, a configuration example in which, for example, an electric parking brake device is applied as one form of the parking brake device is shown. However, the present invention is not limited to the above-described exemplary form. As another form to which the present invention can be applied, for example, the present invention can be applied in substantially the same manner to a vehicle equipped with a mechanical parking brake device configured using a tow wire or the like.

[0129] In the above embodiment, the vehicle M equipped with the vehicle travel control device 1 including the brake control device of the present invention is described as a so-called battery electric vehicle (BEV) having a plurality of drive motors (32F, 32R) as a drive source, but the vehicle to which the vehicle brake control device of the present invention is applied is not limited to the configuration example of the above embodiment. For example, the present invention can be appropriately applied to so-called hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), fuel cell electric vehicles (FCEV), etc. that have an internal combustion engine and an electric motor as drive sources, as well as conventional types of automobiles that have only an internal combustion engine that uses fossil fuels such as gasoline as a drive source. [Explanation of symbols]

[0130] 1...Vehicle driving control device 3F…Front axle 3R…Rear axle 7F, 7R…Brake device 10...Camera unit 11...Stereo camera 11a…Main camera 11b…Sub camera 12...Image processing unit 13...Image recognition unit 14…Control unit 15...Brake state determination unit 16…Road surface μ estimation unit 17...Various sensors 18...Wheel speed sensor 21...Cockpit control unit (CP_ECU) 22...Drive motor control unit (D / M_ECU) 23...Brake control unit (BK_ECU) 31…Human Machine Interface (HMI) 31a…Alarm device 32F…Front drive motor 32R…Rear drive motor 33...Brake actuator FR,FL…Front wheel RR,RL…Rear wheel M…Vehicle

Claims

1. a driving force control unit that controls the driving of the front wheels and the rear wheels separately; A parking brake device for maintaining a parked state of a vehicle; A control unit including at least a parking brake state determination unit that determines a state of the parking brake device and a road surface μ estimation unit that estimates a friction coefficient of a road surface; Equipped with The control unit controls the driving force control unit based on the determination result by the parking brake state determination unit and the estimation result by the road surface μ estimation unit to drive and control the front wheels and the rear wheels, respectively; In this case, When it is determined that the parking brake device is stuck, When the estimated friction coefficient of the road surface is less than a predetermined threshold, the driving force control unit performs a drive control to limit the drive of the front wheels and drive the rear wheels, When the estimated friction coefficient of the road surface is equal to or greater than a predetermined threshold, the driving force control unit performs a driving control to drive only the front wheels. A vehicle brake control device comprising:

2. 2. The vehicle brake control device according to claim 1, wherein when the parking brake device is determined to be stuck and the estimated friction coefficient of the road surface is less than a predetermined threshold, the limitation of the drive of the front wheels performed by the driving force control unit is to cut off the driving force.

3. The control unit After the driving force control unit starts driving control of the front wheels and the rear wheels, the parking brake state determination unit performs state determination again, 2. The vehicle brake control device according to claim 1, wherein when it is determined that the parking brake device has been released from its stuck state, a drive control is performed to gradually reduce the drive force applied to the rear wheels by the drive force control unit.

4. Further comprising an alarm device, 4. The vehicle brake control device according to claim 3, wherein the control unit issues a predetermined warning by the notification device when the parking brake state determination section determines again that the parking brake is stuck.

5. 2. The vehicle brake control device according to claim 1, wherein the parking brake state determination unit detects a change in a rotation angle of a drive motor that drives the rear wheels.

Images