JP2010116061A - Vehicle braking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle braking device achieving optimal brake-related control depending upon road surface conditions. <P>SOLUTION: The vehicle braking device 1 includes: a lock suppressing means 7b for suppressing wheel locks when a slip ratio is larger than a target slip ratio; a pitching suppressing means 7c for suppressing vehicle pitching when a vehicle body speed is a permitted minimum vehicle body speed or above and a vehicle body deceleration is a start permit deceleration or above; a sand road determination means 7d for determining whether a vehicle travels on a sand road; and a change means 7e for increasing the target slip ratio and decreasing the permitted minimum vehicle body speed and the start permit deceleration when the sand road determination means 7d determines that the vehicle travels on the sand road. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle braking device suitable for being applied to vehicles such as passenger cars, trucks, buses and the like.

  Usually, in a vehicle, a wheel cylinder of a brake device provided for each wheel is applied based on a command by a driver depressing a brake pedal or a braking command of a device for controlling the speed of the vehicle such as ACC (Adaptive Cruse Control). On the other hand, hydraulic pressure is supplied from the master cylinder, further hydraulic pressure is supplied from the wheel cylinder to the brake cylinder of each wheel, and braking is performed by pressing the brake pad against the brake disc drive-coupled to the hub by the brake cylinder, The vehicle is decelerating or stopping.

In such a brake device, when the vehicle body speed is obtained from the wheel speeds of the front, rear, left and right wheels, and the slip ratio obtained by dividing the value obtained by subtracting the vehicle body speed from each wheel speed by the vehicle body speed is greater than the target slip ratio. By considering the occurrence of slip and removing the hydraulic pressure from the wheel cylinder corresponding to the wheel where the slip is occurring, the pressure of the brake pad against the brake disc is loosened to prevent or suppress the lock of the wheel. So-called ABS (Anti-Lock Brake System) is used to prevent the stop distance or the braking distance from extending. In the case where this ABS is used, Patent Document 1 discloses that the braking force is reduced due to the hydraulic pressure being removed from the wheel cylinder, thereby inducing the pitching of the vehicle. A technique for suppressing this pitching is disclosed in Patent Document 2.
JP-A-8-20323 JP-A-6-72307

  However, in such a conventional technology, the vehicle traveling on the sandy road including the desert is not considered, and when the vehicle is traveling on the sandy road, the stopping distance and the braking distance are suppressed as much as possible by suppressing the pitching. Since it was not possible to meet the contradictory requirement of preventing the front wheels from being buried in the desert after shortening, optimal control related to braking according to the road surface condition could not be realized. There was still a problem of not.

  In view of the above problems, an object of the present invention is to provide a vehicle braking device that can optimally execute control related to braking according to road surface conditions.

In order to solve the above problem, the vehicle braking device according to the present invention is:
Lock restraining means for restraining wheel lock when the slip ratio is larger than the target slip ratio;
Pitching suppression means for suppressing the pitching of the vehicle when the vehicle body speed is greater than or equal to the permitted minimum vehicle body speed and the vehicle body deceleration is greater than or equal to the permitted start vehicle deceleration;
Sandy road judging means for judging whether or not the vehicle is traveling on a sandy road;
When the sand road determination means determines that the vehicle is traveling on a sand road, the target slip ratio is increased, and a changing means for decreasing the minimum allowable vehicle body speed and the start permission deceleration is provided. It is characterized by that.

  Here, increasing the target slip ratio means setting the target slip ratio to be larger than the initial value of the target slip ratio suitable for normal road traveling on a normal road surface that is not a sandy road. Decreasing the vehicle body speed is to set a smaller value than the initial value of the permitted minimum vehicle body speed suitable for normal road traveling on a normal road surface that is not a sandy road, and reducing the start permission deceleration is a sandy road. It is to set small with respect to the initial value of the start permission deceleration that is suitable for normal driving on a non-normal road surface.

  In addition, the operation range of the pitching suppression means is set to a relatively high vehicle speed range by the permitted minimum vehicle body speed, and the operation range of the pitching suppression means is set to a relatively high deceleration range by the start permission deceleration. The demand for suppressing the vehicle pitching and suppressing the increase of the stop distance or the braking distance is considered to be large in the high vehicle speed region and the high deceleration region.

  Further, the pitching suppression means, for example, when supplying the master cylinder pressure to the wheel cylinder, makes the slope of the pressure rise lie down or loosens, or suppresses the peak value to be small, thereby reducing the braking force in the initial stage of braking. By holding at a value smaller than the normal braking force, vehicle pitching is suppressed.

  Various methods can be used for the sandy road determination means to determine whether or not the vehicle is traveling on a sandy road. For example, an estimated deceleration estimated from a master cylinder hydraulic pressure, and the vehicle body Based on the comparison with the actually measured deceleration in step, it is determined that the vehicle is traveling on a sandy road when the estimated deceleration is separated from the deceleration by a sandy road determination threshold or more. be able to.

  In the present invention, when the sand road determination means determines that the vehicle is running on a sand road, the slip ratio at which the target slip ratio is increased to be suppressed by the lock suppression means is determined as a normal road. Make it larger than when driving. In the sandy road, the relationship between the slip amount and the friction coefficient is a straight line that rises to the right without having an inflection point that is convex upward compared to a normal road. The friction coefficient of the wheel can be increased by increasing the slip amount to increase the deceleration, thereby shortening the stopping distance and the braking distance on the sandy road.

  Further, in the present invention, when it is determined that the vehicle is traveling on a sandy road, the deceleration is increased, and the operating range of the pitching suppression means is set in a direction in which the vehicle body speed is low and the deceleration is low. As a result, the pitching suppression control is executed even in a low vehicle speed range and a low deceleration range. Thereby, at the initial stage when the slip ratio starts to suppress the locking of the wheel by the lock suppressing means, the control for suppressing the pitching is performed, and the nose dive of the vehicle is suppressed as much as possible. Can prevent the front wheel from slipping and being buried excessively with respect to the sandy road.

  That is, according to the present invention, in running the vehicle on the sandy road, the stopping distance and the braking distance are shortened, and the front wheel of the wheels, in particular, the front wheel slips excessively with respect to the sandy road and is buried. Events can also be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle braking device which can perform optimally the control regarding the braking according to the road surface condition can be provided.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an embodiment of a vehicle braking device according to the present invention.

  As shown in FIG. 1, the vehicle braking device 1 includes a brake pedal 2, a stroke sensor 3 provided on the brake pedal 2 for detecting a stroke value of the brake pedal 2, and a pedaling force input to the brake pedal 2 by a driver. A vacuum booster 4 that communicates with a negative pressure generating pipe that generates negative pressure using the negative pressure of the engine that is boosted; a master cylinder 5 that generates operating hydraulic pressure from the basic hydraulic pressure by the boosted pedal force; It comprises a reservoir 6 for storing basic hydraulic pressure, a brake ECU 7 (Brake Electronic Control Unit), a wheel speed sensor 8, a deceleration sensor 9, and a brake actuator 10.

  The wheel speed sensor 8 is provided at four locations corresponding to the front, rear, left and right (FR, FL, RR, RL) wheels, detects each wheel speed, and outputs the detection result to the brake ECU 7.

  The deceleration sensor 9 is provided at the center of the floor of the vehicle body, for example, and detects the deceleration actually generated in the vehicle body and outputs the detection result to the brake ECU 7.

  The operation hydraulic pressure or the basic hydraulic pressure is supplied to the inlet of the hydraulic piping of the brake actuator 10. The brake actuator 10 includes an FR system and an FL system. For example, the FR system hydraulically brakes the right front wheel FR and the left rear wheel RL, and the FL system hydraulically brakes the left front wheel FL and the right rear wheel RR. Since the configuration of both is the same, only the FR system is used. This will be described with reference to FIG.

  The brake actuator 10 includes a hydraulic pipe, a holding valve 11, a holding valve 12, a pressure reducing valve 13, a pressure reducing valve 14, a reservoir 15, and a master cylinder pressure sensor 16.

  The hydraulic piping is first branched at the branch point A from the inlet toward the downstream side, and the master cylinder pressure sensor 16 is arranged on the upstream side of the branch point A, so that the operating hydraulic pressure or basic hydraulic pressure ( When the pedal force is not applied to the pedal 2, the operation oil pressure = basic oil pressure is detected and the detection result is output to the brake ECU 7.

  A branch point B is provided on the downstream side of the hydraulic pipe after branching from the branch point A to the left side. A holding valve 11 for the right front wheel FR is provided on one downstream side of the branch point B, and the left rear side is provided on the other side. A holding valve 12 for the wheel RL is provided. On the other hand, the hydraulic piping branched rightward from the branch point A is communicated with the reservoir 15.

  A branch point C is provided on the downstream side of the holding valve 11, the wheel cylinder 17 of the right front wheel FR is communicated with one hydraulic pipe downstream of the branch point C, and a pressure reducing valve is provided downstream of the branch point C of the other pipe. 13 communicates with the reservoir 15.

  Similarly, a branch point D is provided on the downstream side of the holding valve 12, the wheel cylinder 18 of the left rear wheel RL is connected to one hydraulic pipe downstream of the branch point D, and the branch point D of the other pipe is connected. The downstream is communicated with the reservoir 15 via the pressure reducing valve 14. The holding valve 11 and the holding valve 12 supply operating hydraulic pressure to the wheel cylinders 17 and 18 as supply hydraulic pressure.

  The brake ECU 7 includes, for example, a CPU, a ROM, a RAM, a data bus connecting them, and an input / output interface. The CPU performs predetermined processing according to a program stored in the ROM. The means 7b, the pitching suppression means 7c, the sandy road judgment means 7d, and the changing means 7e are configured.

  The control means 7a of the brake ECU 7 includes the holding valves 11, 12 included in the brake actuator 10 and the pressure reducing pressure based on the stroke sensor value detected by the stroke sensor 3 and the master pressure sensor value detected by the master cylinder pressure sensor 16 shown in FIG. Hydraulic braking is performed by appropriately controlling the valves 13 and 14.

  The lock suppression means 7b of the brake ECU 7 obtains four wheel speeds from the front, rear, left and right wheel speed sensors 8, calculates the average value of the wheel speeds of the rolling wheels, calculates the vehicle speed, and calculates the vehicle speed from the respective decelerations. The slip ratio is obtained by dividing the value obtained by subtracting the vehicle speed from the vehicle body speed, and when the braking by the control means 7a is performed and the slip ratio of a certain wheel becomes larger than the target slip ratio, the pressure reducing valve corresponding to the corresponding wheel By performing control to open 13 or 14 as appropriate, the wheel cylinder pressure inside the wheel cylinder 17 or 18 is reduced to perform ABS control for suppressing lock.

  The pitching suppression means 7c of the brake ECU 7 closes the pressure reducing valves 13 and 14 and opens the holding valves 11 and 12 as appropriate, and when the master cylinder pressure is supplied to the wheel cylinder, the rising slope of the pressure is laid down and loosened. By suppressing the peak value to a small value (for example, about 40%) and maintaining the braking force at the initial stage of braking at a value smaller than the braking force at the normal time, the pitching of the vehicle is suppressed.

  The sand road judging means 7d of the brake ECU 7 differentiates the vehicle body speed obtained from the master cylinder pressure sensor 16 to obtain an estimated deceleration, and further obtains the actual deceleration from the deceleration sensor 9 to estimate the deceleration. The deceleration is compared, and when these differences are equal to or greater than the threshold for sandy road determination, it is determined that the vehicle is traveling on the sandy road.

  The change means 7e of the brake ECU 7 increases the target slip ratio from the initial value and sets the minimum allowable vehicle body speed to the initial value (when the sand road determination means 7d determines that the vehicle is traveling on the sand road. For example, the start permission deceleration is set to be smaller than an initial value (for example, 0.3 G).

  Hereinafter, the control content of the vehicle braking device 1 of a present Example is demonstrated using a flowchart and a map. FIG. 2 is a flowchart showing the control contents of the vehicle braking apparatus 1 according to the present invention.

  In step S1 shown in FIG. 2, the sand road judging means 7d of the brake ECU 7 detects and acquires the actual deceleration from the deceleration sensor 9, and in step S2, the brake ECU 7 locks the brake ECU 7 from the four wheel speed sensors 8. The suppression means 7b detects and acquires the wheel speed. In step S3, the lock suppression means 7b calculates the vehicle body speed and the slip ratio, and the sandy road determination means 7d calculates the estimated deceleration.

  In step S4, the sand road determination means 7d of the brake ECU 7 determines whether or not the vehicle is traveling on the sand road, based on whether or not the difference between the estimated deceleration and the deceleration is equal to or greater than a sand road determination threshold. If the result is affirmative, the process proceeds to step S5. If the result is negative, the process proceeds to step S8.

  In step S5, the changing means 7e of the brake ECU 7 increases the target slip ratio from the initial value, and in step S6, the changing means 7e decreases the allowable minimum vehicle body speed to an initial value (for example, 80 km / h). Further, in step S7, the changing unit 7e makes the start permission deceleration smaller than an initial value (for example, 0.3 G).

  Subsequently, in step S8, the control unit 7a of the brake ECU 7 turns on a flag indicating whether or not the lock suppression unit 7b is a period before the control is started when the slip rate becomes equal to or higher than the target slip rate. If the result is affirmative, the process proceeds to step S9. If the result is negative, the process proceeds to step S10. In step S10, the lock restraining means 7b of the brake ECU 7 executes normal ABS control.

  In step S9, the pitching suppression means 7c of the brake ECU 7 has an initial value that is greater than or equal to the minimum allowable vehicle body speed, which is the initial value when the vehicle body speed is changed or not changed, and the deceleration is changed or not changed. If it is equal to or greater than a certain start permission deceleration and satisfies the pitching suppression control start condition, the process proceeds to step S11 if affirmative, and proceeds to step S12 if negative.

  In step S11, the pitching suppression means 7c of the brake ECU 7 performs the pitching suppression control, and in step S12, the normal cylinder pressure is supplied to the wheel cylinders 17 and 18 by opening the holding valves 13 and 14 as they are. I do.

  According to the vehicle braking device 1 of the present embodiment realized by the control contents described above, the following operational effects can be obtained. In this embodiment, when the sand road determination means 7d determines that the vehicle is traveling on the sand road, the slip ratio at which the lock suppression means 7b suppresses the lock by increasing the target slip ratio is normally set. Make it larger than when driving on the road.

  By using the fact that the relationship between the slip amount and the coefficient of friction in a sandy road is a straight line with no upward inflection point, the wheel against the sandy road is used. The coefficient of friction of the vehicle can be increased as the slip amount increases, thereby increasing the deceleration of the vehicle and shortening the stopping distance and braking distance of the vehicle on the sandy road.

  At the same time, in this embodiment, when it is determined that the vehicle is traveling on a sandy road, the deceleration is increased, and the operating range of the pitching suppression means 7c is set in the direction in which the vehicle body speed is small and the deceleration is small. By expanding in the direction, the pitching suppression control is executed even in the low vehicle speed range and the low deceleration range.

  As a result, control is performed to suppress pitching in a stage before the ABS control is executed with the slip ratio at which the suppression of the locking of the wheel by the lock suppressing means 7b is started, and the nose dive of the vehicle is suppressed as much as possible. In particular, the front wheel can be prevented from being excessively slipped and buried with respect to the sandy road.

  According to the present embodiment, in the vehicle traveling on the sandy road, while the stop distance and the braking distance are shortened, there is also a contradictory event that the front wheel among the wheels, in particular, slips excessively with respect to the sandy road and is buried. Can be prevented. In other words, the ABS control, the pitching suppression control, and the sandy road determination can be harmonized, and the control related to the braking can be optimally classified according to the road surface condition.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

  The present invention relates to a technology for braking a vehicle, and can optimally execute control related to braking according to road surface conditions by adding a relatively minor logic change without adding new components. Therefore, the present invention is useful when applied to various vehicles such as passenger cars, trucks, and buses.

1 is a block diagram showing an embodiment of a vehicle braking device according to the present invention. It is a flowchart which shows the control content of one Embodiment of the vehicle braking device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle braking device 2 Brake pedal 3 Stroke sensor 4 Vacuum booster 5 Master cylinder 6 Reservoir 7 Brake ECU
7a Control means 7b Lock suppression means (ABS)
7c Pitching suppression means 7d Sand road judgment means 7e Change means 8 Wheel speed sensors (FR, FL, RR, RL)
9 Deceleration sensor 10 Brake actuator 11 Holding valve 12 Holding valve 13 Pressure reducing valve 14 Pressure reducing valve 15 Reservoir 16 Master cylinder pressure sensor 17 Wheel cylinder 18 Wheel cylinder

Claims (1)

  Lock suppression means that suppresses wheel lock when the slip ratio is larger than the target slip ratio, and suppresses vehicle pitching when the vehicle body speed is equal to or higher than the permitted minimum vehicle body speed and the vehicle body deceleration is equal to or greater than the start permitted deceleration. The pitching suppressing means, the sandy road judging means for judging whether or not the vehicle is running on the sandy road, and when the sandy road judging means determines that the vehicle is running on the sandy road, A vehicle braking apparatus comprising: a changing unit that increases a target slip ratio and decreases the minimum allowable vehicle body speed and the start allowable deceleration.

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