JP2007030752A - Brake control system and method for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control system and method for a vehicle capable of properly shortening a stopping distance of the vehicle after a braking force is applied to the vehicle in an antilock brake control operation. <P>SOLUTION: When a vehicle body deceleration is equal to or more than a vehicle body deceleration threshold in a braking application to the vehicle, CPU determines it as high G braking, and repeatedly executes an operation for retaining and increasing braking force of front wheels so that slip ratio of the front wheels becomes equal to or more than a second slip ratio threshold and less than first slip ratio threshold. Then, if the slip ratio of the front wheels becomes equal to or more than slip ratio threshold of a control start time, and the vehicle body deceleration becomes more than the vehicle body deceleration threshold, CPU starts the antilock brake control. This means CPU starts the antilock brake control only after making a condition of increasing the braking force of the vehicle by maximally increasing vertical load of the front wheels. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle braking control device and a vehicle braking control method for controlling the locking of each wheel by controlling the braking force applied to each wheel of the vehicle during vehicle braking.

  In general, a braking control device for a vehicle that performs anti-lock brake control (also referred to as “ABS control”) that secures the steering of the vehicle by suppressing the locking of each wheel during vehicle braking (particularly during sudden braking). In addition, vehicle braking control methods are widely known. Such a vehicle brake control device performs anti-lock brake control during vehicle braking, thereby shortening the distance from when the passenger steps on the brake pedal until the vehicle stops (that is, the stop distance). (For example, Patent Document 1).

The vehicle braking control device disclosed in Patent Document 1 determines whether or not the vehicle body deceleration of the vehicle is higher than a predetermined value during vehicle braking (that is, whether or not high-G braking is performed), and the brake pedal is It is determined whether or not the amount of depression is greater than a predetermined amount (that is, whether or not sudden braking is performed). By the way, in the case of high G braking and sudden braking, the μ value on the front wheel side is slightly reduced, but the load on the vehicle moves to the front wheel side, resulting in a sufficiently increased ground contact load on the front wheel. As a result, the braking force value of the front wheels increases. On the other hand, when the load of the vehicle moves to the front wheel side, the ground contact load of the rear wheel decreases, and as a result, a phenomenon that the rear wheel side lifts up (so-called rear lift up) may occur. Therefore, the braking control device for a vehicle disclosed in Patent Document 1 temporarily holds the braking force of the front wheels when the braking is high G and the braking is sudden (that is, when the braking force value of the front wheels becomes high). Thus, load movement to the front wheel side during vehicle braking is suppressed, and rear lift up is avoided.
Japanese Patent No. 2727907 (Claim 2, paragraph number [0014])

  By the way, in the ABS control by the vehicle braking control apparatus described in Patent Document 1, when the value of the braking force of the front wheels is high, the braking force of the front wheels is temporarily held to avoid rear lift-up during vehicle braking. In addition, the stability of traveling in the vehicle is ensured. However, in this case, once the braking force of the front wheels is held, the deceleration of the vehicle body of the vehicle is lowered, so that even if antilock brake control is performed, the stopping distance may be extended.

  The present invention has been made in view of such circumstances, and an object of the present invention is to improve the distance from when a braking force is applied to the vehicle to when the vehicle stops when antilock brake control is performed. It is an object of the present invention to provide a vehicle braking control device and a vehicle braking control method that can be shortened.

  In order to achieve the above object, the invention according to claim 1 relating to a braking control device for a vehicle includes a braking means (18a, 18b, 18c, etc.) for applying a braking force to each wheel (FR, FL, RR, RL). 18d) and control start determination means (40) for determining whether or not an anti-lock brake control start condition for suppressing locking of each wheel (FR, FL, RR, RL) during vehicle braking is satisfied. When the determination result of the control start determining means (40) is negative, the braking means (18a, 18b, 18c, 18d) is such that the braking force of the front wheels (FR, FL) is held and increased. If the determination result of the control start determination means (40) is affirmative, the braking means (18a, 18b, 18c, 1) is started so as to start the antilock brake control. And summarized in that and a control means (40) for controlling the d).

  According to the first aspect of the present invention, when the determination result of the control start determination means is negative during vehicle braking, the braking force of the front wheels is repeatedly held and increased, so that the vehicle load is reduced to the front wheel side. As a result, the ground contact load of the front wheels increases, so that the braking force of the front wheels increases. And since anti-lock brake control is started in the state which the braking force of the vehicle increased in this way, the braking force of the vehicle by this anti-lock brake control is ensured suitably. Therefore, when the antilock brake control is performed, the distance from when the braking force is applied to the vehicle to when the vehicle stops can be favorably shortened.

  According to a second aspect of the present invention, in the vehicle braking control apparatus according to the first aspect, slip ratio detecting means (SLF, SLR) for detecting the slip ratio (SLF, SLR) of each wheel (FR, FL, RR, RL). 40) and whether the slip ratio (SLF) of the front wheels (FR, FL) detected by the slip ratio detection means (40) during vehicle braking is equal to or greater than a preset first slip ratio threshold (KSLF1). The braking force holding determining means (40) for determining whether or not, and the slip ratio (SLF) of the front wheels (FR, FL) detected by the slip ratio detecting means (40) during vehicle braking are the first slip ratio. Brake force increase determination means (40) for determining whether or not it is less than a second slip ratio threshold value (KSLF2) that is smaller than the threshold value (KSLF1), the control means (40) When the determination result of the control start determination means (40) is negative and the determination result of the braking force holding determination means (40) is affirmative, the braking force of the front wheels (FR, FL) is increased. While controlling the braking means (18a, 18b, 18c, 18d) to hold, when the determination result of the braking force increase determination means (40) is affirmative, the braking force of the front wheels (FR, FL) The gist is to control the braking means (18a, 18b, 18c, 18d) so as to increase the torque.

  In the invention according to claim 2, when the determination result of the control start determination means is negative, the slip ratio of the front wheels is equal to or greater than the second slip ratio threshold and less than the first slip ratio threshold. The braking means is controlled. As a result, the load on the vehicle based on the braking of the vehicle increases the ground contact load of the front wheels to the maximum, so that the braking force of the vehicle can be increased to the maximum. That is, since anti-lock brake control is started in a state where the braking force of the vehicle reaches the maximum value, the braking force of the vehicle can be sufficiently ensured.

  According to a third aspect of the present invention, in the vehicle brake control device according to the first or second aspect, the control means (40) is configured to start the antilock brake control so that the brake means (18a, When the rear wheel braking force increase control for increasing the braking force of the rear wheels (RR, RL) is performed for the first time after the control of 18b, 18c, 18d) is started, the timing to end the rear wheel braking force increase control The main point is to delay the process.

  In the third aspect of the invention, when the determination result of the control start determining means is affirmative and the anti-lock brake control is started, the load of the vehicle moves from the front wheel side to the rear wheel side. The grounding load increases (returns). In order to cope with the return of the ground load of the rear wheel, the control means delays the timing for ending the rear wheel braking force increase control which is performed for the first time after the antilock brake control is started. That is, the braking force of the rear wheel is further increased in order to cope with the return of the ground load on the rear wheel side. Therefore, the braking force of the rear wheel can be ensured when the ground load on the rear wheel returns.

  According to a fourth aspect of the present invention, in the vehicle braking control device according to any one of the first to third aspects, the vehicle body deceleration detecting means (40) for detecting the vehicle body deceleration (DVS) of the vehicle. , SE1, SE2, SE3, SE4) and the vehicle body deceleration (DVS) detected by the vehicle body deceleration detecting means (40, SE1, SE2, SE3, SE4). KG) or more, a vehicle body deceleration determining means (40) for determining whether or not the vehicle body deceleration determining means (40) is positive. The gist of the present invention is to determine whether or not the anti-lock brake control start condition is satisfied.

  According to the fourth aspect of the present invention, when the determination result of the vehicle body deceleration determination means is affirmative, control for increasing the contact load on the front wheels and anti-lock brake control are performed. That is, each control described above is performed when the vehicle body deceleration of the vehicle is high (that is, in the case of high G braking). Therefore, in the case of high G braking, the present invention can favorably shorten the distance from when the braking force is applied to the vehicle until the vehicle stops.

  On the other hand, according to the fifth aspect of the invention relating to the vehicle braking control method, the anti-lock brake control start condition for suppressing the lock of each wheel (FR, FL, RR, RL) is established during vehicle braking. If not, the braking force of the front wheels (FR, FL) is held and increased, and then the antilock brake control is started when the antilock brake control start condition is satisfied. Is the gist.

  In the invention according to the fifth aspect, the same effect as that of the invention according to the first aspect can be obtained.

  Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. In the following description of the present specification, the traveling direction (forward direction) of the vehicle is assumed to be the front (front of the vehicle). Unless otherwise specified, the left-right direction in the following description is the same as the left-right direction in the vehicle traveling direction.

  As shown in FIG. 1, the vehicle braking control device 11 according to this embodiment includes a plurality of (four in this embodiment) wheels (a right front wheel FR, a left front wheel FL, a right rear wheel RR, and a left rear wheel RL). It is mounted on the vehicle that has it. The vehicle braking control device 11 includes a hydraulic pressure generating device 14 having a master cylinder 12 and a booster 13 and a hydraulic pressure control device (indicated by a two-dot chain line in FIG. 1) 17 having two hydraulic pressure circuits 15 and 16. I have. The hydraulic circuits 15 and 16 are connected to the hydraulic pressure generator 14 and are connected to wheel cylinders (braking means) 18a, 18b, 18c, and 18d provided corresponding to the wheels FR, FL, RR, and RL. It is connected. Further, the vehicle braking control device 11 is provided with an electronic control device (also referred to as “ECU”) 19 for controlling the hydraulic pressure control device 17.

  The hydraulic pressure generating device 14 is provided with a brake pedal 20, and the master cylinder 12 and the booster 13 of the hydraulic pressure generating device 14 are driven based on the operation of the brake pedal 20 by a vehicle occupant. It has become. The master cylinder 12 is provided with two output ports 12a and 12b. The first hydraulic circuit 15 is connected to one of the output ports 12a and 12b, and the other of the output ports 12a and 12b. A second hydraulic circuit 16 is connected to the output port 12b. Further, the hydraulic pressure generator 14 is provided with a brake switch SW1 that transmits a signal for starting braking control to the electronic control unit 19 when the brake pedal 20 is operated.

  The hydraulic pressure control device 17 includes a pump 21 for increasing the brake hydraulic pressure in the first hydraulic pressure circuit 15, a pump 22 for increasing the brake hydraulic pressure in the second hydraulic pressure circuit 16, and each pump. A motor M for simultaneously driving 21 and 22 is provided. In addition, reservoirs 23 and 24 for storing brake oil are provided on the hydraulic circuits 15 and 16, and the brake oil in the reservoirs 23 and 24 is supplied to the hydraulic circuits based on driving of the pumps 21 and 22. 15 and 16 are supplied. The hydraulic pressure circuits 15 and 16 are provided with hydraulic pressure sensors PS1 and PS2 for detecting the brake hydraulic pressure in the master cylinder 12.

  The first hydraulic circuit 15 includes a right front wheel path 15a for the wheel cylinder 18a (for the right front wheel FR) connected to the wheel cylinder 18a corresponding to the right front wheel FR, and a wheel cylinder 18d corresponding to the left rear wheel RL. And a left rear wheel path 15b for the wheel cylinder 18d (for the left rear wheel RL) connected to. On each of these paths 15a and 15b, normally open solenoid valves 25 and 26 and normally closed solenoid valves 27 and 28 are provided, respectively.

  Similarly, the second hydraulic circuit 16 corresponds to the left front wheel path 16a for the wheel cylinder 18b (for the left front wheel FL) connected to the wheel cylinder 18b corresponding to the left front wheel FL, and the right rear wheel RR. A right rear wheel path 16b for the wheel cylinder 18c (for the right rear wheel RR) connected to the wheel cylinder 18c is formed. On each of the paths 16a and 16b, normally open solenoid valves 29 and 30 and normally closed solenoid valves 31 and 32 are provided, respectively.

  Here, changes in the brake fluid pressure in the wheel cylinders 18a to 18d when the solenoid coils of the solenoid valves 25 to 32 are in the energized state and in the non-energized state will be described.

  First, when all the solenoid coils of the solenoid valves 25 to 32 are in a non-energized state, the normally open solenoid valves 25, 26, 29, and 30 remain open, and the normally closed solenoid valves. 27, 28, 31, 32 remain closed. Therefore, brake oil flows from the master cylinder 12 into the wheel cylinders 18a to 18d via the paths 15a, 15b, 16a, and 16b, and the brake hydraulic pressure in the wheel cylinders 18a to 18d increases.

  On the other hand, when all the solenoid coils of the solenoid valves 25 to 32 are energized, the normally open solenoid valves 25, 26, 29, and 30 are closed, and the normally closed solenoid valves 27 and 28 are closed. , 31 and 32 are opened. Therefore, brake oil flows from the wheel cylinders 18a to 18d to the reservoirs 23 and 24 via the paths 15a, 15b, 16a, and 16b, and the brake hydraulic pressure in the wheel cylinders 18a to 18d decreases. Become.

  When only the solenoid coils of the normally open solenoid valves 25, 26, 29, and 30 among the solenoid valves 25 to 32 are energized, all the solenoid valves 25 to 32 are closed. Therefore, the flow of brake oil through each path 15a, 15b, 16a, 16b is restricted. As a result, the brake fluid pressure in each wheel cylinder 18a-18d is maintained at its fluid pressure level.

  As shown in FIG. 2, the electronic control device 19 is mainly configured by a digital computer including a CPU 40, a ROM 41, and a RAM 42 as control means, and a drive circuit (not shown) for driving each device. ing. The ROM 41 includes a control program for controlling the hydraulic pressure control device 17 (driving the motor M and the electromagnetic valves 25 to 32), and various threshold values (a first slip ratio threshold value, a second slip ratio threshold value described later, and Vehicle body deceleration threshold etc.) is stored. The RAM 42 stores various information that can be appropriately rewritten while the vehicle braking control device 11 is being driven.

  Further, the input side interface (not shown) of the electronic control unit 19 includes the brake switch SW1, the hydraulic pressure sensors PS1 and PS2, and a wheel speed sensor for detecting the wheel speeds of the wheels FL, FR, RL, and RR. SE1, SE2, SE3, and SE4 are connected to each other. That is, the CPU 40 receives signals from the brake switch SW1, the hydraulic pressure sensors PS1 and PS2, and the wheel speed sensors SE1 to SE4. On the other hand, to the output side interface (not shown) of the electronic control unit 19, a motor M for driving the pumps 21 and 22 and the electromagnetic valves 25 to 32 are connected. The CPU 40 individually controls the operation of the motor M and the electromagnetic valves 25 to 32 based on the input signals from the switch SW1 and the sensors PS1, PS2, SE1 to SE4.

  Next, among the control processing routines executed by the CPU 40 of the present embodiment, the anti-lock brake control processing routine executed when the CPU 40 receives a signal from the brake switch SW1 is a flowchart shown in FIGS. 3 and 4 and FIG. This will be described below with reference to the timing chart shown in FIG.

  Now, the CPU 40 executes an anti-lock brake control processing routine every predetermined cycle. In this antilock brake control processing routine, the CPU 40 first detects the wheel speed VW of each wheel FR, FL, RR, RL based on the signal received from each wheel speed sensor SE1 to SE4 (step S10). . In this embodiment, for convenience of explanation, the wheel speed VW of the right front wheel FR and the wheel speed VW of the left front wheel FL have the same value, and the wheel speed VW of the right rear wheel RR and the left rear wheel RL The wheel speed VW is assumed to be the same value.

  Subsequently, the CPU 40 detects a vehicle body speed (estimated vehicle body speed) VS of the vehicle (step S11). Specifically, the CPU 40 sets the vehicle speed VS of the vehicle having the largest value among the wheel speeds VW of the wheels FR, FL, RR, RL detected in step S10. Then, the CPU 40 differentiates the vehicle body speed VS detected in step S11 to detect (calculate) the vehicle body deceleration (estimated vehicle body deceleration) DVS of the vehicle (step S12). In this regard, in the present embodiment, the wheel speed sensors SE1 to SE4 and the CPU 40 function as vehicle body deceleration detecting means for detecting the vehicle body deceleration DVS of the vehicle.

  Subsequently, the CPU 40 determines whether the vehicle body deceleration DVS detected in step S12 is the ROM 41 in order to determine whether or not high-G braking is being performed (that is, whether or not the vehicle body deceleration DVS of the vehicle is large). It is determined whether or not the vehicle body deceleration threshold value KG is preset or not (step S13). The vehicle body deceleration threshold value KG is a threshold value for determining whether or not the high-G braking is performed, and is set by experiment, simulation, or the like. If the determination result in step S13 is negative (DVS <KG), the CPU 40 determines that it is not high G braking and ends the antilock brake control processing routine. On the other hand, when the determination result of step S13 is affirmative (DVS ≧ KG), the CPU 40 determines that the high-G braking is performed, and the process proceeds to step S14 described later. In this regard, in the present embodiment, the CPU 40 functions as a vehicle body deceleration determination unit.

  Here, in the case of high G braking, as shown in FIGS. 5 (a) and 5 (d), the vehicle load moves to the front wheels FR, FL side. That is, as shown in FIGS. 5B and 5E, as the braking force of each wheel FR, FL, RR, RL increases based on the increase of the brake fluid pressure in the wheel cylinders 18a-18d, the vehicle load increases. Moves from the rear wheels RR and RL to the front wheels FR and FL. Then, the ground load on the front wheels FR and FL gradually increases, and the ground load on the rear wheels RR and RL gradually decreases.

  In step S14, the CPU 40 detects (calculates) the slip ratio SLF of the front wheels FR and FL and the slip ratio SLR of the rear wheels RR and RL. Specifically, the CPU 40 calculates the slip ratio SLF of the front wheels FR and FL and the slip ratio SLR of the rear wheels RR and RL with respect to the vehicle body speed VS. In this regard, in this embodiment, the CPU 40 detects the slip ratios SLF and SLR of the wheels FR, FL, RR, and RL based on the wheel speed VW of the wheels FR, FL, RR, and RL detected in step S10. It also functions as a slip ratio detecting means. Here, the slip ratio SLF of the front wheels FR and FL and the slip ratio SLR of the rear wheels RR and RL are respectively calculated based on the following conditional expressions.

(Slip ratio SLF of front wheels FR, FL) = ((wheel speed VW of front wheels FR, FL) − (vehicle speed VS of vehicle)) / (vehicle speed VS of vehicle) (1)
(Slip ratio SLR of rear wheels RR, RL) = ((wheel speed VW of rear wheels RR, RL) − (vehicle speed VS of vehicle)) / (vehicle speed VS of vehicle) (2)
Subsequently, the CPU 40 differentiates the wheel speed VW of each wheel FR, FL, RR, RL detected in step S10, thereby detecting the wheel deceleration DVW of each wheel FR, FL, RR, RL ( (Calculation) (step S15). Then, the CPU 40 determines whether or not the ABS flag ABSF is “OFF” (step S16). The ABS flag ABSF is a flag for determining whether or not the anti-lock brake control for suppressing the locking of the wheels FR, FL, RR, and RL during vehicle braking is performed. FIG. As shown in FIG. 5, when the anti-lock brake control start condition is satisfied, it is set to “ON”. If the determination result in step S16 is negative (ABSF = “ON”), the CPU 40 proceeds to step S25, which will be described later.

  On the other hand, if the determination result in step S16 is affirmative (ASF = “OFF”), the CPU 40 determines from the control start slip ratio threshold value KSLF that the slip ratio SLF of the front wheels FR and FL detected in step S14 is set in advance. Is also larger (step S17). The control start slip ratio threshold value KSLF is a threshold value that is a necessary condition for starting the antilock brake control, and is set by experiment, simulation, or the like. And when the determination result of step S17 is negative determination (SLF <= KSLF), CPU40 transfers the process to step S20 mentioned later.

  On the other hand, if the determination result in step S17 is affirmative (SLF> KSLF), the CPU 40 determines that the wheel deceleration DVW of the front wheels FR and FL detected in step S15 is greater than the wheel deceleration threshold value KDVW preset in the ROM 41. Is also larger (step S18). The wheel deceleration threshold value KDVW is a threshold value that is a necessary condition for starting the anti-lock brake control, and is set by experiment, simulation, or the like. If the determination result in step S18 is affirmative (DVW> KDVW), the CPU 40 sets the ABS flag ABSF to “ON” in order to start the antilock brake control (step S19). The process proceeds to step S24 described later. That is, when either one of steps S17 and S18 is negative, the CPU 40 determines that the anti-lock brake control start condition is not satisfied, while the determination results in steps S17 and S18 are both. If the determination is affirmative, it is determined that the anti-lock brake control start condition is satisfied. In this regard, in the present embodiment, the CPU 40 also functions as a control start determination unit that determines whether or not a start condition for the antilock brake control is satisfied.

  On the other hand, if the determination result in step S17 is negative (SLF ≦ KSLF) or the determination result in step S18 is negative (DVW ≦ KDVW), the CPU 40 detects the slip ratio SLF of the front wheels FR and FL detected in step S14. Is greater than or equal to a first slip ratio threshold value KSLF1 preset in the ROM 41 (step S20). In this regard, in this embodiment, the CPU 40 also functions as a braking force holding determination unit. Note that the first slip ratio threshold value KSLF1 investigates the relationship between the μ value of a tire (not shown) attached to the front wheels FR and FL and the slip ratio, and immediately before the μ value becomes maximum (so-called μ peak). Set to slip ratio. Therefore, when the slip rate SLF of the front wheels FR and FL is less than the first slip rate threshold value KSLF1, there is no possibility of a rear lift-up phenomenon (a phenomenon in which the rear wheels RR and RL are lifted), and the vehicle travels. Stability is sufficiently secured.

  If the determination result in step S20 is affirmative (SLF ≧ KSLF1), the CPU 40 performs front wheel braking force holding control to hold the braking force of the front wheels FR and FL (step S21). Specifically, the CPU 40 retains (holds) the brake fluid pressure in the wheel cylinders 18a and 18b that applies braking force to the front wheels FR and FL, and the electromagnetic valve 25 and the left on the right front wheel path 15a. By energizing each solenoid of the electromagnetic valve 29 on the front wheel path 16a, the electromagnetic valves 25 and 29 are closed. Thereafter, the CPU 40 shifts the process to step S22 described later. On the other hand, when the determination result of step S20 is negative (SLF <KSLF1), the CPU 40 proceeds to step S22 without executing step S21.

  In step S22, the CPU 40 determines whether or not the slip ratio SLF of the front wheels FR and FL detected in step S14 is less than a second slip ratio KSLF2 (<first slip ratio threshold KSLF1) preset in the ROM 41. Determine. In this regard, in this embodiment, the CPU 40 also functions as a braking force increase determination unit. The second slip ratio threshold value KSLF2 is a value that ensures a sufficient braking force of the vehicle when the slip ratio SLF of the front wheels FR and FL is equal to or greater than the second slip ratio threshold value KSLF2. Set by experiment or simulation.

  If the determination result in step S22 is affirmative (SLF <KSLF2), the CPU 40 performs front wheel braking force increase control in order to increase the braking force of the front wheels FR and FL (step S23). Specifically, the CPU 40 increases the brake fluid pressure in the wheel cylinders 18a and 18b that applies the braking force to the front wheels FR and FL, and the electromagnetic valve 25 on the right front wheel path 15a and the left front wheel path 16a. The solenoid valves 25 and 29 are opened by turning off the solenoids of the upper solenoid valve 29. Thereafter, the CPU 40 ends the antilock brake control processing routine. On the other hand, when the determination result of step S22 is negative (SLF ≧ KSLF2), the CPU 40 ends the antilock brake control processing routine without executing step S23.

  Here, when either one of steps S17 and S18 is negative, the CPU 40 determines that the braking force of the front wheels FR and FL is maintained and increased as shown in FIG. 5B. The brake fluid pressure in 18a and 18b is repeatedly held and increased. That is, the CPU 40 starts the front wheel braking force holding control when a time t1 after the signal from the brake switch SW1 is received (hereinafter referred to as “elapsed time”) t1, and the elapsed time t2 (> When t1) has elapsed, the front wheel braking force increase control is started. The CPU 40 starts the front wheel braking force holding control when the elapsed time t3 (> t2) has elapsed, and starts the front wheel braking force increase control when the elapsed time t4 (> t3) has elapsed, and the elapsed time t5. When (> t4) has elapsed, front wheel braking force holding control is started.

  When the control is performed in this way, the vehicle load moves from the rear wheels RR and RL to the front wheels FR and FL as shown by the solid line in FIG. 5A, and the ground load of the front wheels FR and FL gradually increases. . In addition, a sufficiently large value of the grounding load of the front wheels FR and FL can be obtained as compared with the grounding load of the front wheels FR and FL in the case of the conventional braking control method (indicated by a one-dot chain line in FIG. 5A). . That is, in the braking control method according to the present embodiment, it is possible to obtain a contact load having a value larger than the contact load of the front wheels FR and FL when the tire mounted on the front wheels FR and FL has a μ peak.

  On the other hand, when the determination result of step S18 is affirmative, the CPU 40 executes antilock brake control after executing step S19 as described above (step S24). That is, as shown in FIGS. 5B and 5E, the CPU 40 repeatedly decreases and holds the braking force of the front wheels FR and FL, and sequentially increases, holds and decreases the braking force of the rear wheels RR and RL. . Thereafter, the CPU 40 ends the antilock brake control processing routine.

  Here, immediately after the start condition of the anti-lock brake control is established, as shown by the solid line in FIG. 5A, the ground load of the front wheels FR and FL becomes maximum. At that timing, in order to avoid locking of the wheels FR, FL, RR, RL, the CPU 40, as shown in FIGS. 5B and 5C, based on the start of the anti-lock brake control, , RR, RL, the brake fluid pressure in each wheel cylinder 18a-18d is reduced in order to reduce the braking force. Then, as shown in FIGS. 5A and 5D, the ground load on the front wheels FR and FL starts to decrease, and the ground load on the rear wheels RR and RL starts to increase (return). Subsequently, the anti-lock brake control is continuously executed, so that the ground loads of the wheels FR, FL, RR, and RL become substantially stable.

  On the other hand, when the determination result of step S16 is negative, the CPU 40 does not increase the rear wheel braking force (control for increasing the braking force of the rear wheels RR and RL) for the first time after the ABS flag ABSF is set to “ON”. ) Is being executed (step S25). Specifically, the CPU 40 determines whether or not the rear wheels RR and RL solenoid valves 26, 28, 30, and 32 are all in a non-energized state for the first time after the ABS flag ABSF is set to “ON”. . That is, when all the solenoid valves 26, 28, 30, and 32 for the rear wheels RR and RL are not energized for the first time after the ABS flag ABSF is set to “ON”, the determination flag is “ON”. The CPU 40 determines whether or not the determination flag is “ON”. If the determination result in step S25 is negative (determination flag = “OFF”), the CPU 40 proceeds to step S24.

  On the other hand, when the determination result of step S25 is affirmative (determination flag = “ON”), the CPU 40 executes rear wheel braking force increase assist control (step S26). Specifically, the CPU 40 delays the timing for ending the rear wheel braking force increase control by a predetermined time T1. That is, the CPU 40 delays the timing for energizing the solenoid valve 26 on the left rear wheel path 15b and the solenoid valve 30 on the right rear wheel path 16b by a predetermined time T1. Thereafter, the CPU 40 ends the antilock brake control processing routine.

  Here, when the antilock brake control is started, as described above, the ground load of the rear wheels RR and RL increases (returns). Therefore, in the present embodiment, by executing the rear wheel braking force increase assist control, the timing for ending the rear wheel braking force increase control for the first time after the ABS flag ABSF is set to “ON” The method is delayed by a predetermined time T1 as compared with the case of the method (indicated by a broken line in FIG. 5E). Therefore, the brake fluid pressure in the wheel cylinders 18c, 18d for the rear wheels RR, RL increases.

  In this embodiment, when the CPU 40 stops receiving the signal from the brake switch SW1, the CPU 40 sets the ABS flag ABSF to “OFF” and stops the antilock brake control.

Next, a vehicle braking control method according to this embodiment will be described with reference to FIG.
Now, when a passenger steps on the brake pedal 20 while the vehicle is running, braking force is applied to the wheels FR, FL, RR, and RL from the wheel cylinders 18a to 18d. In addition, in the case of high G braking (vehicle deceleration DVS ≧ vehicle deceleration threshold KG), the vehicle load increases from the rear wheels RR and RL to the front wheels FR and FL as the vehicle braking force increases. Move to. That is, the ground load on the front wheels FR and FL increases, and the ground load on the rear wheels RR and RL decreases (see FIGS. 5A and 5D). Further, as indicated by a solid line in FIG. 6, the slip ratio SLF of the front wheels FR and FL increases with an increase in the braking force of the vehicle.

  When the slip ratio SLF of the front wheels FR and FL is equal to or greater than the first slip ratio threshold value KSLF1, the braking force of the front wheels FR and FL is held to hold the braking force of the vehicle. That is, the electromagnetic valves 25 and 29 are closed so as to maintain the brake fluid pressure in the wheel cylinders 18a and 18b for the front wheels FR and FL. Then, the slip ratio SLF of the front wheels FR and FL decreases (see FIG. 6), and the ground load of the front wheels FR and FL increases (see FIG. 5 (a)).

  When the slip ratio SLF of the front wheels FR and FL is smaller than the second slip ratio threshold value KSLF2, the braking force of the front wheels FR and FL is increased in order to increase the braking force of the vehicle. That is, the electromagnetic valves 25 and 29 are opened so as to increase the brake fluid pressure in the wheel cylinders 18a and 18b for the front wheels FR and FL. Then, the slip ratio SLF of the front wheels FR and FL increases (see FIG. 6), and the ground load of the front wheels FR and FL increases (see FIG. 5 (a)).

  When the front wheel braking force holding control and the front wheel braking force increase control are repeatedly executed in this way, the ground contact load of the front wheels FR and FL increases to the maximum. As a result, as shown in FIG. 6, the braking force of the front wheels FR and FL is increased. Increases as compared to the case where the above-described controls are not executed. Then, when the slip ratio SLF of the front wheels FR and FL is greater than the control start slip ratio threshold value KSLF, and the wheel deceleration DVW> the wheel deceleration threshold value KDVW, the antilock brake control is started.

  That is, first, the braking force of each wheel FR, FL, RR, RL is reduced in order to suppress the lock of each wheel FR, FL, RR, RL. Then, the direction of load movement of the vehicle is reversed, and the ground load of the rear wheels RR and RL starts to increase. Next, the brake fluid pressure in each of the wheel cylinders 18a to 18d is held (holding pressure) so as to hold the braking force of each of the wheels FR, FL, RR, and RL, and then the rear wheels RR and RL are controlled. In order to increase the power, the brake fluid pressure in the wheel cylinders 18c, 18d for the rear wheels RR, RL is increased. That is, on the rear wheels RR and RL side, the rear wheel braking force increase control is performed only after the antilock brake control is started. At this time, in the braking force control method of the present embodiment, the rear wheel braking force increase control is performed longer than the conventional braking control method by a predetermined time T1. Therefore, when the ground load of the rear wheels RR and RL increases (returns) based on the start of the antilock brake control, the braking force of the rear wheels RR and RL is ensured satisfactorily.

  Next, on the rear wheels RR, RL side, the brake fluid pressure in the wheel cylinders 18c, 18d for the rear wheels RR, RL is maintained in order to maintain the braking force of the rear wheels RR, RL. Thereafter, the antilock brake control for each wheel FR, FL, RR, RL is continued. At this time, the braking force of the vehicle at the start of the antilock brake control in the present embodiment is sufficiently increased as compared with the braking force of the vehicle at the start of the antilock brake control in the conventional braking control method ( (See FIG. 6). For this reason, in the braking control method of the present embodiment, the distance from when the passenger steps on the brake pedal 20 until the vehicle stops (so-called stopping distance) is favorably shortened compared to the conventional braking control method. The

Therefore, in this embodiment, the following effects can be obtained.
(1) During vehicle braking, if the determination result of either one of steps S17 and S18 is negative, the braking force of the front wheels FR and FL is repeatedly held and increased, so that the vehicle load is As a result of the movement to the FR, FL side, the ground load on the front wheels FR, FL increases, so that the braking force of the vehicle (particularly, the braking force of the front wheels FR, FL) increases. Since the determination result of steps S17 and S18 is both affirmative and the antilock brake control is started in the state where the braking force of the vehicle is increased in this way, the braking force of the vehicle by the antilock brake control is ensured. The Therefore, when the antilock brake control is performed, the distance from when the braking force is applied to the vehicle to when the vehicle stops can be favorably shortened.

  (2) When the determination result of any one of steps S17 and S18 is negative, the slip ratio SLF of the front wheels FR and FL is equal to or greater than the second slip ratio threshold value KSLF2, and the first slip ratio threshold value KSLF1. The brake fluid pressure in each wheel cylinder (braking means) 18a, 18b is controlled so as to be less than the above. Therefore, as a result of maximizing the ground load of the front wheels FR and FL by moving the vehicle load based on the braking of the vehicle, the braking force of the vehicle can be maximized. That is, since the anti-lock brake control is started in a state where the braking force of the front wheels FR and FL reaches the maximum value, the braking force of the vehicle can be sufficiently ensured.

  (3) When the determination results of steps S17 and S18 are both affirmative and anti-lock brake control is started, the load of the vehicle moves from the front wheels FR and FL to the rear wheels RR and RL. The ground load of RR and RL increases (returns). In order to cope with the return of the ground load of the rear wheels RR and RL, the CPU (control means) 40 sets a predetermined timing for ending the rear wheel braking force increase control which is performed for the first time after the antilock brake control is started. Delayed by time T1. That is, the braking force of the rear wheels RR and RL is increased in order to cope with the return of the ground load of the rear wheels RR and RL. Therefore, when the ground load of the rear wheels RR and RL is restored, the braking force of the rear wheels RR and RL can be ensured.

  (4) If the determination result in step S13 is affirmative, control for increasing the ground load of the front wheels FR and FL and antilock brake control are performed. That is, each control described above is performed when the vehicle body deceleration DVS of the vehicle is high (that is, in the case of high G braking). Therefore, in the case of high G braking, this embodiment can favorably shorten the distance from when the braking force is applied to the vehicle until the vehicle stops.

The embodiment may be changed to another embodiment (another example) as follows.
In the embodiment, when the braking control device 11 is mounted on a vehicle having a relatively high center of gravity (for example, a high center of gravity vehicle such as a 1BOX vehicle), step S13 may be omitted. That is, in the case of a high center of gravity vehicle, even when the vehicle body deceleration DVS is small (that is, in the case of low G braking), the vehicle load may greatly move toward the front wheels FR and FL during vehicle braking. Therefore, even in the case of low G braking, the distance from when the braking force is applied to the vehicle until the vehicle stops can be shortened.

In the embodiment, the rear wheel braking force increase assist control (step S26) is not necessarily executed.
-In embodiment, it is not necessary to memorize | store the 1st slip ratio threshold value KSLF1 and the 2nd slip ratio threshold value KSLF2 in ROM41. In this case, even if it is determined in step S13 that the braking is high G, the brake fluid pressure in each wheel cylinder 18a, 18b is controlled so as to repeatedly hold and increase the braking force of the front wheels FR, FL. Good.

-In embodiment, when either one of step S17, S18 is affirmation determination, you may make it start anti-lock brake control.
In the embodiment, a vehicle body deceleration sensor (also referred to as “G sensor”) may be provided on the vehicle body, and the vehicle body deceleration sensor DVS may be detected by the vehicle body deceleration sensor.

  In the embodiment, the first hydraulic circuit 15 is connected to the wheel cylinder 18a for the right front wheel FR and the wheel cylinder 18b for the left front wheel FL, and the second hydraulic circuit 16 is for the right rear wheel RR. The wheel cylinder 18c and the wheel cylinder 18d for the left rear wheel RL may be connected.

1 is a block diagram of a vehicle braking control device in the present embodiment. The block diagram of the electronic control apparatus in this embodiment. The flowchart which shows an anti-lock brake control processing routine (first half part). The flowchart (second half part) which shows an anti-lock brake control processing routine. (A) is a timing chart showing changes in the ground contact load of the front wheels, (b) is a timing chart showing changes in the braking force of the front wheels, (c) is a timing chart showing ON / OFF switching of the ABS flag, and (d). Is a timing chart showing the change in the ground contact load of the rear wheel, (e) is a timing chart showing the change in the braking force of the rear wheel. The graph which shows the relationship between the slip ratio of a front wheel and the braking force of a vehicle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Vehicle braking control apparatus, 18a-18d ... Wheel cylinder (braking means), 40 ... CPU (control start determination means, control means, slip ratio detection means, braking force holding determination means, braking force increase determination means, vehicle body reduction Speed detection means, vehicle deceleration determination means), DVS ... vehicle deceleration, FR, FL ... front wheels (wheels), KG ... vehicle deceleration threshold, KSLF1 ... first slip ratio threshold, KSLF2 ... second slip ratio threshold , SE1 to SE4: wheel speed sensor (vehicle deceleration detection means), SLF: slip ratio of front wheels, SLR: slip ratio of rear wheels, RR, RL: rear wheels (wheels).

Claims (5)

Braking means (18a, 18b, 18c, 18d) for applying a braking force to each wheel (FR, FL, RR, RL);
Control start determination means (40) for determining whether or not an antilock brake control start condition for suppressing locking of each wheel (FR, FL, RR, RL) during vehicle braking is satisfied;
If the determination result of the control start determination means (40) is negative, the braking means (18a, 18b, 18c, 18d) is such that the braking force of the front wheels (FR, FL) is maintained and increased. On the other hand, if the determination result of the control start determination means (40) is affirmative, the braking means (18a, 18b, 18c, 18d) is controlled to start the antilock brake control. A braking control device for a vehicle, comprising: a control means (40) for controlling the vehicle. Slip rate detection means (40) for detecting slip rates (SLF, SLR) of the wheels (FR, FL, RR, RL);
It is determined whether the slip ratio (SLF) of the front wheels (FR, FL) detected by the slip ratio detection means (40) during vehicle braking is equal to or greater than a preset first slip ratio threshold (KSLF1). Braking force holding determination means (40) for performing;
A second slip ratio in which the slip ratio (SLF) of the front wheels (FR, FL) detected by the slip ratio detection means (40) during vehicle braking is smaller than the first slip ratio threshold (KSLF1). Braking force increase determination means (40) for determining whether or not it is less than a threshold (KSLF2),
When the determination result of the control start determination means (40) is negative and the determination result of the braking force holding determination means (40) is affirmative, the control means (40) , FL) while controlling the braking means (18a, 18b, 18c, 18d) so that the braking force of the braking force increase determining means (40) is affirmative. The braking control device for a vehicle according to claim 1, wherein the braking means (18a, 18b, 18c, 18d) is controlled so as to increase a braking force of FR, FL). The control means (40) increases the braking force of the rear wheels (RR, RL) only after starting the control of the braking means (18a, 18b, 18c, 18d) so as to start the antilock brake control. The vehicle braking control device according to claim 1 or 2, wherein when the rear wheel braking force increase control to be performed is performed, a timing for ending the rear wheel braking force increase control is delayed. Vehicle body deceleration detecting means (40, SE1, SE2, SE3, SE4) for detecting vehicle body deceleration (DVS) of the vehicle;
It is determined whether the vehicle body deceleration (DVS) detected by the vehicle body deceleration detection means (40, SE1, SE2, SE3, SE4) is equal to or greater than a preset vehicle body deceleration threshold (KG). Vehicle body deceleration determination means (40),
The said control start determination means (40) determines whether the start conditions of the said anti-lock brake control were satisfied, when the determination result of the said vehicle body deceleration determination means (40) is affirmation determination. The braking control device for a vehicle according to any one of claims 3 to 4. During vehicle braking, if the anti-lock brake control start condition for suppressing the lock of each wheel (FR, FL, RR, RL) is not satisfied, the braking force of the front wheels (FR, FL) is maintained and increased. After that, when the anti-lock brake control start condition is satisfied, the anti-brake brake control is started.

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