JP2019043256A - Vehicular brake force control apparatus - Google Patents

Abstract

To enable determination of abnormality in a front wheel system of the brake device of a large-scale vehicle.SOLUTION: A brake force control apparatus 10 includes: a brake device 12 that has a front wheel system 12F and a rear wheel system 12R that increase and decrease brake force of left- and right-front wheels and left- and right-rear wheels, respectively; and a control device 14 for controlling the brake device. Further, in the apparatus, when a preset condition is satisfied, the control device limits an increase in brake force Fbr of the rear wheel associated with an increase in brake force Fbv of the vehicle, thus limits brake force of the rear wheel by the front-rear wheel brake force distribution control. In a case where a product of front wheel and rear wheel brake slip ratios (SLf, SLr) is equal to or less than a reference value SLc while the brake force of the rear wheels is being limited, the control device 14 determines that the brake device 12 is abnormal and loosens the limit in the brake force of the rear wheel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vehicle braking force control device that performs front and rear wheel braking force distribution control.

  In a vehicle such as an automobile, if a preset condition is established to ensure the stability of the vehicle during braking, the front and rear wheel control is restricted by limiting the increase in the braking force of the rear wheels accompanying the increase in the braking force of the vehicle. It is known to limit the braking force of the rear wheels by power distribution control. In a braking force control device that performs front and rear wheel braking force distribution control, the braking force of the rear wheels is limited in a situation where an abnormality has occurred in the front wheel system of the braking device and the braking force of the front wheels is not normally generated. As a result, the braking force of the entire vehicle is insufficient, and the braking distance of the vehicle becomes long.

  In order to prevent such a situation, it is already known that when the front wheel system of the braking device is abnormal, the restriction of the braking force of the rear wheel by the front and rear wheel braking force distribution control is prohibited. For example, in Patent Document 1 below, if the difference between the deceleration of the front wheels and the deceleration of the rear wheels during braking of the vehicle does not have a maximum value, it is determined that the front wheel system of the braking device is abnormal. A braking force control device that prohibits the restriction of the braking force of the rear wheels by the front and rear wheel braking force distribution control is described.

  According to the braking force control device described in Patent Document 1, if it is determined that the front wheel system of the braking device is abnormal, the restriction of the braking force of the rear wheels by the front and rear wheel braking force distribution control is prohibited. The Therefore, since the braking force of the rear wheels is not limited, the braking force of the entire vehicle can be made higher than when the braking force of the rear wheels is limited even when the front wheel system of the braking device is abnormal. The degree to which the braking distance of the vehicle becomes longer due to the lack of the braking force of the entire vehicle can be reduced.

Japanese Patent Laid-Open No. 08-301092

[Problems to be Solved by the Invention]
According to the braking force control apparatus described in Patent Document 1, when the vehicle is a medium-sized vehicle such as a passenger car and the support load of the front wheels is higher than the support load of the rear wheels, the front wheel system of the brake device If becomes abnormal, the abnormality can be determined. However, if the vehicle is a large vehicle such as a truck and the rear wheel support load is higher than the front wheel support load, the abnormality cannot be determined even if the front wheel system of the braking device becomes abnormal.

  In a small and medium-sized vehicle, for example, as indicated by a solid line in FIG. 7, the actual front / rear distribution line (solid line) of the braking force may be set to intersect the ideal front / rear distribution line (broken line). Assuming that the front wheel braking force Fbf at the point where the actual front / rear distribution line intersects the ideal front / rear distribution line is Fbf0, when the front wheel braking force Fbf is less than Fbf0, the front wheel slip ratio is larger than the rear wheel slip ratio. When the front wheel braking force Fbf exceeds Fbf0, the front wheel slip rate is smaller than the rear wheel slip rate.

  Therefore, in a situation where the front wheel system of the braking device is normal, the difference between the front wheel deceleration Gwf and the rear wheel deceleration Gwr when the front wheel braking force Fbf and the rear wheel braking force Fbr gradually increase is as follows: As shown in FIG. 8, it has a maximum value. On the other hand, in a situation where the front wheel system of the braking device is abnormal and the braking force cannot be generated normally, the front wheel deceleration when the front wheel braking force Fbf and the rear wheel braking force Fbr gradually increase. The difference between Gwf and the rear wheel deceleration Gwr does not have a local maximum as shown in FIG.

  As indicated by a two-dot chain line in FIG. 7, when the front wheel braking force Fbf is equal to or greater than Fbf0, the front wheel system of the braking device is normal even when the front wheel braking force Fbr is limited. In some circumstances, the difference between the front wheel deceleration Gwf and the rear wheel deceleration Gwr has a local maximum. However, in a situation where the front wheel system of the braking device is abnormal and braking force cannot be normally generated, the difference between the front wheel deceleration Gwf and the rear wheel deceleration Gwr does not have a maximum value. Therefore, it is determined whether or not the front wheel system of the braking device is abnormal by determining whether or not the difference between the deceleration of the front wheels and the deceleration of the rear wheels has a maximum value when braking the vehicle. Can do.

  On the other hand, in a large vehicle, the rear wheel braking force is higher than the front wheel braking force in response to the rear wheel support load being higher than the front wheel support load. ) Is set so as not to intersect the ideal front-rear distribution line (broken line) as shown in FIG. Therefore, the slip ratio of the rear wheel is larger than the slip ratio of the front wheel over the entire region of the braking force Fbf of the front wheel and Fbr of the rear wheel.

  Therefore, even in a situation where the front wheel system of the braking device is normal, the difference between the front wheel deceleration Gwf and the rear wheel deceleration Gwr when the front wheel braking force Fbf and the rear wheel braking force Fbr gradually increase is as follows: It does not have a local maximum as shown in FIG. The difference between the front wheel deceleration Gwf and the rear wheel deceleration Gwr in a situation where the front wheel system of the braking device is abnormal and the braking force cannot be generated normally is shown in FIG. This is the same as in the case of small and medium-sized vehicles. Therefore, it cannot be determined whether or not the front wheel system of the braking device is abnormal by determining whether or not the difference between the deceleration of the front wheels and the deceleration of the rear wheels has a maximum value during braking of the vehicle. .

  The main problem of the present invention is that when the front wheel system or the rear wheel system of the braking device is abnormal, the abnormality is determined regardless of the magnitude of the support load of the front and rear wheels, and the rear wheel control by the braking force distribution control is performed. It is an object of the present invention to provide an improved braking force control device that can relax power limitation.

[Means for Solving the Problems and Effects of the Invention]
According to the present invention, the braking device (12) having the front wheel system (12F) for increasing / decreasing the braking force of the left and right front wheels and the rear wheel system (12R) for increasing / decreasing the braking force of the left and right rear wheels, and the control for controlling the braking device. The control device includes a device (14), and when the preset condition is satisfied, the control device restricts an increase in the braking force (Fbr) of the rear wheel accompanying an increase in the braking force (Fbv) of the vehicle. A vehicular braking force control device (10) configured to limit the braking force of rear wheels by power distribution control is provided.

  The control device (14) calculates the braking slip index values (SLf, SLr) for the front wheels and the rear wheels in a situation where the braking force of the entire vehicle is equal to or greater than the reference value of the braking force. When the product of the braking slip index value of the wheel is equal to or less than the reference value (SLc) of the braking slip index value, it is determined that the braking device is abnormal, and even if the preset condition is satisfied, the rear wheel It is configured to relax the braking force limit.

  According to the above configuration, when the preset condition is not satisfied, the increase in the braking force of the rear wheel accompanying the increase in the braking force of the vehicle is not limited, and the rear wheel is controlled by the front and rear wheel braking force distribution control. There is no power limitation. On the other hand, if a preset condition is satisfied, the increase in the braking force of the rear wheels accompanying the increase in the braking force of the vehicle is limited, and thus the braking force of the rear wheels is limited by the front and rear wheel braking force distribution control. Done. Therefore, the braking force of the front and rear wheels is generated regardless of whether or not the preset condition is satisfied, so when the front wheel system and the rear wheel system are normal, Regardless, the braking slip index values for the front and rear wheels are positive values of a certain magnitude. Accordingly, the product of the braking slip index value of the front wheel and the braking slip index value of the rear wheel is a value larger than the reference value of the braking slip index value.

  On the other hand, in a situation where the front wheel system or rear wheel system of the braking device is abnormal and the braking force cannot be normally generated, the abnormal system wheels regardless of the magnitude of the support load of the front and rear wheels. The braking slip index value is 0 or a small value. Therefore, the product of the braking slip index value of the front wheels and the braking slip index value of the rear wheels becomes a value equal to or less than the reference value of the braking slip index value. Therefore, when the front wheel system or the rear wheel system of the braking device is abnormal, by confirming that the product of the braking slip index values of the front wheels and the rear wheels is not more than the reference value, at least one of the front wheel system and the rear wheel system Can be determined to be abnormal.

  According to the above configuration, in a situation where the braking force of the entire vehicle is greater than or equal to the reference value of the braking force, the braking slip index values of the front wheels and the rear wheels are calculated, and the product of these braking slip index values is the braking slip index value. When it is less than the reference value, it is determined that at least one of the front wheel system and the rear wheel system is abnormal. Therefore, when the front wheel system or the rear wheel system is abnormal, the abnormality can be determined regardless of the magnitude relationship of the support loads of the front and rear wheels.

  Further, if it is determined that at least one of the front wheel system and the rear wheel system is abnormal, the restriction on the braking force of the rear wheel is relaxed even if a preset condition is satisfied. Therefore, since the braking force of the rear wheel can be increased as compared with the case where the restriction on the braking force of the rear wheel is not relaxed, the rear wheel braking force distribution control by the front and rear wheel braking force distribution control is performed when the front wheel system is abnormal. The degree to which the braking force of the entire vehicle becomes insufficient due to the limitation of the braking force and the braking distance of the vehicle becomes long can be reduced. If the rear wheel system is abnormal, the rear wheel system cannot normally generate braking force. Therefore, even if the restriction on the braking force of the rear wheel is relaxed, the braking force of the rear wheel is increased. Although it is not possible, the restriction of the braking force on the rear wheels will not be adversely affected.

  In the above description, in order to help understanding of the present invention, the reference numerals used in the embodiment are attached to the configuration of the invention corresponding to the embodiment described later in parentheses. However, each component of the present invention is not limited to the component of the embodiment corresponding to the reference numerals appended in parentheses. Other objects, other features and attendant advantages of the present invention will be readily understood from the description of the embodiments of the present invention described with reference to the following drawings.

It is a schematic block diagram which shows embodiment of the braking force control apparatus for vehicles by this invention. It is a flowchart which shows the front-and-rear wheel distribution control routine of the braking force in the embodiment. It is a flowchart which shows the abnormality determination control routine in embodiment. It is a front-and-rear wheel distribution diagram of braking force for explaining front-and-rear wheel distribution control of braking force by an embodiment about a case where a braking device is normal and a case where it is abnormal. It is a graph which shows the example of the change of the product SLf * SLr of the slip ratio of a front wheel and a rear wheel when a braking device is normal. It is a graph which shows the example of a change of product SLf * SLr of the slip ratio of a front wheel and a rear wheel in case a brake device is abnormal. It is a front-rear wheel distribution diagram of braking force showing an actual front-rear distribution line (solid line) and an ideal front-rear distribution line (broken line) of a medium-to-small vehicle. It is a graph which shows the example of the change of the difference Gwf-Gwr of the deceleration of a front wheel and a rear wheel in case a front wheel system is normal about a medium-sized vehicle. It is a graph which shows the example of the change of the difference Gwf-Gwr of the deceleration of a front wheel and a rear wheel when a front wheel system | strain is abnormal about a medium-sized vehicle. It is a front-rear wheel distribution diagram of braking force showing an actual front-rear distribution line (solid line) and an ideal front-rear distribution line (dashed line) of a large vehicle. It is a graph which shows the example of the change of the difference Gwf-Gwr of the deceleration of a front wheel and a rear wheel when a front-wheel system is normal about a large vehicle. It is a graph which shows the example of the change of the difference Gwf-Gwr of the deceleration of a front wheel and a rear wheel in case a front wheel system | strain is abnormal about a large vehicle.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, a braking force control device 10 according to the embodiment includes a braking device 12 having a front wheel system 12F that increases and decreases the braking force of the left and right front wheels, and a rear wheel system 12R that increases and decreases the braking force of the left and right rear wheels. And an electronic control unit 14 to be controlled. As will be described in detail later, the electronic control unit 14 performs front and rear wheel braking force distribution control that restricts an increase in the rear wheel braking force Fbr as the vehicle braking force Fbv increases when a preset condition is satisfied. Is configured to do. In FIG. 1, illustrations of solenoids and springs of the valves that are electromagnetically driven are omitted.

  The braking device 12 is a hydraulic braking device, and includes a master cylinder 16 that pumps brake oil in response to a depression operation of the brake pedal 15 by the driver. The master cylinder 16 has a first master cylinder chamber 16A and a second master cylinder chamber 16B defined by a free piston 16C urged to a predetermined position by compression coil springs on both sides thereof.

  One end of a brake hydraulic pressure control conduit 18F for the front wheels is connected to the first master cylinder chamber 16A, and the brake hydraulic pressure control conduit 20FL for the left front wheel and the brake for the right front wheel are connected to the other end of the brake hydraulic pressure control conduit 18F. One end of the hydraulic control conduit 20FR is connected. The brake hydraulic control conduit 18F is provided with a front wheel control valve 22F which is a normally open electromagnetic control valve. Connected to the brake hydraulic control conduits 18F on both sides of the control valve 22F are check bypass conduits 24F that permit only the flow of oil from the first master cylinder chamber 16A toward the brake hydraulic control conduit 20FL or the brake hydraulic control conduit 20FR. Yes.

  The control valve 22F is a linear solenoid valve, and controls the pressure in the portion of the brake hydraulic pressure control conduit 18F opposite to the master cylinder 16 in accordance with the control voltage for the solenoid. Therefore, by controlling the control voltage for the solenoid, the pressure (referred to as “upstream pressure” in the present specification) in the opposite portion can be controlled to a desired pressure by the control valve 22F.

  Wheel cylinders 26FL and 26FR for controlling the braking force of the left front wheel and the right front wheel are connected to the other ends of the brake hydraulic control conduit 20FL for the left front wheel and the brake hydraulic control conduit 20FR for the right front wheel, respectively. The brake oil pressure control conduit 20FL for the left front wheel and the brake oil pressure control conduit 20FR for the right front wheel are provided with normally open type electromagnetic on-off valves 28FL and 28FR, respectively. Connected to the brake hydraulic control conduits 20FL and 20FR on both sides of the electromagnetic on-off valves 28FL and 28FR are check bypass conduits 30FL and 30FR that permit only the flow of oil from the wheel cylinders 26FL and 26FR toward the brake hydraulic control conduit 18F, respectively. Yes.

  One end of an oil discharge conduit 32FL is connected to the brake hydraulic control conduit 20FL between the electromagnetic on-off valve 28FL and the wheel cylinder 26FL, and the brake hydraulic control conduit 20FR between the electromagnetic on-off valve 28FR and the wheel cylinder 26FR is connected to the brake hydraulic control conduit 20FL. One end of the oil discharge conduit 32FR is connected. The oil discharge conduits 32FL and 32FR are provided with normally closed electromagnetic on-off valves 34FL and 34FR, respectively, and the other ends of the oil discharge conduits 32FL and 32FR are connected to a buffer reservoir 38F for the front wheels by a connection conduit 36F. ing.

  The electromagnetic on-off valves 28FL and 28FR are pressure increasing valves for increasing or maintaining the pressure in the wheel cylinders 26FL and 26FR, respectively. The electromagnetic on-off valves 34FL and 34FR are for reducing the pressure in the wheel cylinders 26FL and 26FR, respectively. This is a pressure reducing valve. Therefore, the electromagnetic on-off valves 28FL and 34FL define an increasing / decreasing valve for cooperating with each other to increase and decrease the pressure in the wheel cylinder 26FL of the left front wheel. The electromagnetic on-off valves 28FR and 34FR cooperate with each other to define a pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26FR of the right front wheel.

  The connecting conduit 36F is connected to the suction side of the pump 42F by a connecting conduit 40F, and the connecting conduit 40F is provided with two check valves 44F and 46F that allow only the oil flow from the connecting conduit 36F to the pump 42F. It has been. The discharge side of the pump 42F is connected to the brake hydraulic control conduit 18F by a connection conduit 50F having a damper 48F. A connection conduit 50F between the pump 42F and the damper 48F is provided with a check valve 52F that allows only the flow of oil from the pump 42F toward the damper 48F.

  One end of a connection conduit 54F is connected to the connection conduit 40F between the two check valves 44F and 46F, and the other end of the connection conduit 54F is between the first master cylinder chamber 16A and the control valve 22F. Is connected to the brake hydraulic pressure control conduit 18F. The connection conduit 54F is provided with a normally closed electromagnetic on-off valve 60F. The electromagnetic on-off valve 60F functions as a pump intake valve that controls communication between the brake hydraulic pressure control conduit 18F between the master cylinder 16 and the control valve 22F and the intake side of the pump 42F.

  As understood from the above description, the control valve 22F and the like described above are front wheel systems that increase or decrease the braking force of the left front wheel and the right front wheel by increasing or decreasing the pressure in the wheel cylinders 26FL and 26FR of the left front wheel and the right front wheel, respectively. 12F is configured.

  Similarly, one end of a brake hydraulic pressure control conduit 18R for the rear wheel is connected to the second master cylinder chamber 16B, and the brake hydraulic pressure control conduit 20RL for the left rear wheel is connected to the other end of the brake hydraulic pressure control conduit 18R. One end of a brake hydraulic pressure control conduit 20RR for the right rear wheel is connected. The brake hydraulic control conduit 18R is provided with a rear wheel control valve 22R which is a normally open electromagnetic control valve.

  The control valve 22R is a solenoid valve having the same structure as the front wheel control valve 22F, and controls the pressure (upstream) in the brake hydraulic control conduit 18R on the downstream side of the control valve 22R by controlling the control voltage for the renoid. Pressure) can be controlled to a desired pressure. Further, wheel cylinders 26RL and 26RR for controlling the braking force of the left rear wheel and the right rear wheel are connected to the other ends of the brake hydraulic control conduit 20RL for the left rear wheel and the brake hydraulic control conduit 20RR for the right rear wheel, respectively. Has been. The brake hydraulic control conduit 20RL for the left rear wheel and the brake hydraulic control conduit 20RR for the right rear wheel are provided with normally open type electromagnetic on-off valves 28RL and 28RR, respectively. Connected to the brake hydraulic control conduits 20RL and 20RR on both sides of the electromagnetic on-off valves 28RL and 28RR are check bypass conduits 30RL and 30RR that permit only the flow of oil from the wheel cylinders 26RL and 26RR toward the brake hydraulic control conduit 18R, respectively. Yes.

  One end of an oil discharge conduit 32RL is connected to the brake hydraulic control conduit 20RL between the electromagnetic on-off valve 28RL and the wheel cylinder 26RL, and the brake hydraulic control conduit 20RR between the electromagnetic on-off valve 28RR and the wheel cylinder 26RR is connected to the brake hydraulic control conduit 20RL. One end of the oil discharge conduit 32RR is connected. The oil discharge conduits 32RL and 32RR are provided with normally closed electromagnetic on-off valves 34RL and 34RR, respectively, and the other ends of the oil discharge conduits 32RL and 32RR are connected to the buffer reservoir 38R for the rear wheel by the connection conduit 36R. Has been.

  As with the front wheel system 12F, the electromagnetic on-off valves 28RL and 28RR are pressure-increasing valves for increasing or maintaining the pressure in the wheel cylinders 26RL and 26RR, respectively. The electromagnetic on-off valves 34RL and 34RR are respectively the wheel cylinders 26RL and 26RR. This is a pressure reducing valve for reducing the internal pressure. Therefore, the electromagnetic on-off valves 28RL and 34RL define a pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26RL of the left rear wheel in cooperation with each other. The electromagnetic open / close valves 28RR and 34RR define a pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26RR of the right rear wheel in cooperation with each other.

  The connection conduit 36R is connected to the suction side of the pump 42R by a connection conduit 40R. The connection conduit 40R is provided with two check valves 44R and 46R that allow only the flow of oil from the connection conduit 36R to the pump 42R. It has been. The discharge side of the pump 42R is connected to the brake hydraulic control conduit 18R by a connection conduit 50R having a damper 48R. A connection conduit 50R between the pump 42R and the damper 48R is provided with a check valve 52R that allows only the flow of oil from the pump 42R toward the damper 48R. The pumps 42F and 42R are driven by a common electric motor not shown in FIG.

  One end of a connection conduit 54R is connected to the connection conduit 40R between the two check valves 44R and 46R, and the other end of the connection conduit 54R is between the second master cylinder chamber 16B and the control valve 22R. Is connected to the brake hydraulic pressure control conduit 18R. The connection conduit 54R is provided with a normally closed electromagnetic on-off valve 60R. The electromagnetic opening / closing valve 60R also functions as a pump intake valve that controls communication between the brake hydraulic pressure control conduit 18R between the master cylinder 16 and the control valve 22R and the intake side of the pump 42R.

  As can be understood from the above description, the control valve 22R and the like described above increase or decrease the pressure in the wheel cylinders 26RL and 26RR of the left rear wheel and the right rear wheel, thereby increasing the braking force of the left rear wheel and the right rear wheel, respectively. A rear wheel system 12R to be increased or decreased is configured.

  In the illustrated embodiment, each control valve and each on-off valve is set to the non-control position shown in FIG. 1 when the control current is not supplied to the corresponding solenoid. Therefore, the pressure in the first master cylinder chamber 16A is supplied to the wheel cylinders 26FL and 26FR, and the pressure in the second master cylinder chamber 16B is supplied to the wheel cylinders 26RL and 26RR. Accordingly, the pressure in the wheel cylinder of each wheel, that is, the braking force is increased or decreased in accordance with the depression force of the brake pedal 15 at normal times.

  On the other hand, the control valves 22F and 22R are switched to the closed position, the on-off valves 60F and 60R are opened, and the pumps 42F and 42R are operated with the on-off valves of the wheels being at the positions shown in FIG. When driven, the oil in the master cylinder 14 is pumped up by the pump. Therefore, the pressure pumped up by the pump 42F is supplied to the wheel cylinders 26FL and 26FR, and the pressure pumped up by the pump 42R is supplied to the wheel cylinders 26RL and 26RR. Accordingly, the braking pressure of each wheel is increased or decreased by opening / closing the control valves 22F and 22R and the opening / closing valves (increase / decrease valves) of each wheel regardless of the depression force of the brake pedal 12.

  In this case, the pressure in the wheel cylinder is increased when the on-off valves 28FL to 28RR and the on-off valves 34FL to 34RR are in the non-control position shown in FIG. 1 (pressure increasing mode). The pressure in the wheel cylinder is held when the on-off valves 28FL to 28RR are switched to the closed position and the on-off valves 34FL to 34RR are in the non-control position shown in FIG. 1 (holding mode). Further, the pressure in the wheel cylinder is reduced when the on-off valves 28FL to 28RR are switched to the closed position and the on-off valves 34FL to 34RR are switched to the open position (pressure reduction mode).

  The control valves 22F and 22R, the on-off valves 28FL to 28RR, the on-off valves 34FL to 34RR, and the on-off valves 60F and 60R are controlled by the electronic control unit 14. The electronic control device 14 includes a microcomputer 70 and a drive circuit 72. The microcomputer 70 may have a general configuration well known in the art, and includes, for example, a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. Good. The ROM of the microcomputer 70 stores a control program corresponding to the flowcharts shown in FIGS.

  A brake hydraulic pressure control conduit 18F between the master cylinder 16 and the control valve 22F is provided with a pressure sensor 80 that detects the pressure in the first master cylinder chamber 16A as the master cylinder pressure Pma. Similarly, a pressure sensor 82 for detecting the pressure in the second master cylinder chamber 16B as the master cylinder pressure Pmb is provided in the brake hydraulic pressure control conduit 18R between the master cylinder 16 and the control valve 22R. Signals indicating the master cylinder pressures Pma and Pmb detected by the pressure sensors 80 and 82 are input to the microcomputer 70. A wheel speed sensor 84i (i = fl, fr, rl and rr) for detecting the wheel speed Vwi (i = fl, fr, rl and rr) is applied to the left and right front wheels and the left and right rear wheels which are not shown in FIG. ) Is provided. A signal indicating the wheel speed Vwi detected by the wheel speed sensor 84 i is also input to the microcomputer 70.

  The CPU of the microcomputer 70 performs front and rear wheel distribution control of the braking force in accordance with a control program corresponding to the flowchart shown in FIG. The CPU of the microcomputer 70 performs abnormality determination control for the front wheel system and the rear wheel system according to the control program corresponding to the flowchart shown in FIG. 3, and indicates that when the braking device 12 is determined to be abnormal. The alarm is displayed on the alarm device 86.

  Next, the front and rear wheel braking force distribution control routine in the embodiment will be described with reference to the flowchart shown in FIG. Note that the control according to the flowchart shown in FIG. 2 is repeatedly executed at predetermined time intervals when an ignition switch (not shown) is on.

  First, in step 10, a signal indicating the master cylinder pressure Pma detected by the pressure sensor 80 is read. At the start of control, a flag Fdbc, which will be described later, relating to whether or not the rear wheel braking force is being limited is reset to zero.

  In step 20, the target braking force Fbvt of the vehicle is calculated based on the master cylinder pressure Pma or Pmb or the average value Pm thereof.

  In step 30, it is determined whether or not the flag Fab set by the abnormality determination control according to the flowchart shown in FIG. 3 described later is 1, that is, whether or not at least one of the front wheel system and the rear wheel system is abnormal. Is determined. When a positive determination is made, the front and rear wheel braking force distribution control proceeds to step 50, and when a negative determination is made, the front and rear wheel braking force distribution control proceeds to step 40.

  In step 40, the product Rf · Fbvt of the braking force front wheel distribution ratio Rf (positive constant) and the target braking force Fbvt of the vehicle, that is, the target driving force of the front wheels is equal to or greater than the reference value Fbvc (positive constant). Whether or not it is necessary to limit the rear wheel braking force is determined. When a positive determination is made, the front and rear wheel braking force distribution control proceeds to step 70, and when a negative determination is made, the front and rear wheel braking force distribution control proceeds to step 50.

In step 50, the flag Fdbc is reset to 0 indicating that the rear wheel braking force is not being limited. In step 60, the target braking force Fbft of each front wheel and the target braking force Fbrt of each rear wheel are calculated according to the following equations (1) and (2), respectively.
Fbft = Rf · Fbvt / 2 (1)
Fbrt = (1-Rf) Fbvt / 2 (2)

In step 70, the flag Fdbc is set to 1 indicating that the rear wheel braking force is being limited. In step 80, the target braking force Fbft of each front wheel is calculated according to the above equation (1), and the target braking force Fbrt of each rear wheel is set to a constant value Fbrc calculated according to the following equation (3).
Fbrt = (1-Rf) Fbvc / 2 = Fbrc (3)

  In step 90, the braking pressures Pfl and Pfr of the left and right front wheels are controlled by the front wheel system 12F so that the braking force Fbf of the left and right front wheels becomes the target braking force Fbft. Similarly, the braking pressures Prl and Prr for the left and right rear wheels are controlled by the rear wheel system 12R so that the braking force Fbr for the left and right rear wheels becomes the target braking force Fbrt.

  Normally, the braking force of the left and right wheels is controlled to the same value as described above, but the braking force of the wheels is individually controlled as in anti-skid control, vehicle motion control, vehicle automatic operation control, etc. When it is necessary to control, individual control of the braking force is executed with priority. Therefore, the braking forces of the left and right wheels are controlled to different values as necessary.

  Next, the abnormality determination control routine in the illustrated embodiment will be described with reference to the flowchart shown in FIG. Note that the control according to the flowchart shown in FIG. 3 is also repeatedly executed at predetermined time intervals when an ignition switch (not shown) is on.

  First, in step 110, a signal indicating the wheel speed Vwi detected by the wheel speed sensor 84i is read. At the start of control, a flag Fab, which will be described later, relating to whether or not the front wheel system 12F is abnormal is reset to zero.

  In step 120, it is determined whether or not the master cylinder pressure Pm, which is an average value of the master cylinder pressures Pma and Pmb, is equal to or higher than a reference value Pmc (positive constant), that is, whether or not there is a driver's braking request. A determination is made. When a negative determination is made, the abnormality determination control is once ended. When an affirmative determination is made, the abnormality determination control proceeds to step 130. Note that the master cylinder pressure Pm used for this determination may be either the master cylinder pressure Pma or Pmb.

  In step 130, it is determined whether or not the flag Fdbc set by the front and rear wheel braking force distribution control according to the flowchart shown in FIG. 2 is 1, that is, whether or not the rear wheel braking force is being limited. Is determined. When a negative determination is made, the abnormality determination control is temporarily ended. When an affirmative determination is made, the abnormality determination control proceeds to step 140.

  In step 140, the estimated vehicle speed Vb is calculated in a manner known in the art based on the wheel speed Vwi detected by the wheel speed sensor 84i. When the vehicle includes a vehicle speed sensor, the vehicle speed detected by the vehicle speed sensor may be used as the estimated vehicle body speed Vb.

In step 150, the average wheel speed Vwf (= (Vwfl + Vwfr) / 2) for the left and right front wheels and the average wheel speed Vwr (= (Vwrl + Vwrr) / 2) for the left and right rear wheels are calculated. Further, according to the following equations (4) and (5), the front wheel slip ratio SLf and the rear wheel slip ratio SLr are calculated as braking slip index values for the front wheels and the rear wheels. The slip ratio SLf of the front wheel may be an average value of the slip ratio SLfl of the left front wheel and the slip ratio SLfr of the right front wheel, and the slip ratio SLr of the rear wheel is the slip ratio SLrl of the left rear wheel and the right rear wheel. The slip value SLrr may be an average value.
SLf = (Vb−Vwf) / Vb (4)
SLr = (Vb−Vwr) / Vb (5)

  In step 160, it is determined whether or not the product SLf · SLr of the front wheel slip ratio SLf and the rear wheel slip ratio SLr is equal to or smaller than a reference value SLc (positive constant), that is, at least one of the front wheel system and the rear wheel system. Whether or not is abnormal is determined. If a negative determination is made, it is determined in step 170 that the braking device 12 is normal, the flag Fab is reset to 0, and an alarm indicating that the braking device 12 is abnormal is not displayed on the alarm device 86. . On the other hand, when an affirmative determination is made, it is determined in step 180 that the braking device 12 is abnormal, the flag Fab is set to 1, and the warning device 86 indicates that the braking device 12 is abnormal. An alarm is displayed. The reference value SLc is set to a value that makes a negative determination in step 160 when the braking device 12 is normal and the master cylinder pressure Pm is greater than or equal to the reference value Pmc.

  As understood from the above description, when the driver performs a braking operation, the master cylinder pressure Pm is equal to or higher than the reference value Pmc, and the rear wheel braking force is being limited by the front and rear wheel braking force distribution control, step 120 and An affirmative determination is made at 130. In steps 140 and 150, the front wheel slip ratio SLf and the rear wheel slip ratio SLr are calculated. In step 160, it is determined whether or not the product SLf · SLr of these slip ratios is equal to or less than the reference value SLc. Whether or not at least one of the rear wheel systems is abnormal is determined.

  In a situation where the driver performs a braking operation and the master cylinder pressure Pm is equal to or higher than the reference value Pmc, if the front wheel system and the rear wheel system are normal, the front wheel and the rear wheel The braking slip rates SLf and SLr of the rear wheels are positive values of a certain magnitude according to the braking force. Therefore, the product SLf · SLr of the braking slip ratio of the front wheels and the rear wheels increases as the amount of braking operation by the driver increases, and becomes a value larger than the reference value SLc as shown in FIG. 5, for example. Accordingly, a negative determination is made in step 160 and a determination that the front wheel system is normal is made in step 170. Therefore, when the front wheel system and the rear wheel system are normal, the relationship is related to the magnitude of the support load of the front and rear wheels. Therefore, it is not determined that the braking device 12 is abnormal.

  In contrast, even if the master cylinder pressure Pm is equal to or higher than the reference value Pmc, if at least one of the front wheel system and the rear wheel system is abnormal and braking force cannot be generated normally, Regardless of the magnitude relationship of the wheel support load, the braking slip rate of the abnormal wheel is 0 or a very small positive value. Therefore, the product SLf · SLr of the braking slip ratio of the front wheels and the rear wheels does not increase even if the amount of braking operation by the driver is increased, and becomes a value equal to or smaller than the reference value SLc as shown in FIG. 6, for example. . Accordingly, an affirmative determination is made in step 160, and a determination that the braking device 12 is abnormal is made in step 180. Therefore, when at least one of the front wheel system and the rear wheel system is abnormal, it can be determined that the braking device 12 is abnormal regardless of the magnitude relationship of the support loads of the front and rear wheels.

  Next, the control of the braking force by the braking force control device 10 according to the embodiment will be described separately when the braking device 12 is determined to be normal and when the braking device 12 is determined to be abnormal. To do.

<When it is determined that the braking device is normal>
In step 20, the target braking force Fbvt of the vehicle is calculated based on the master cylinder pressure Pma or Pmb or the average value Pm thereof, and the flag Fab is 0 when it is determined that the braking device 12 is normal. Therefore, a negative determination is made at step 30.

  When the target braking force Fbvt of the vehicle is less than the reference value Fbvc, a negative determination is made in step 40, and in step 60, the target braking force Fbft of the left and right front wheels and the target braking force Fbrt of the left and right rear wheels are respectively expressed by the above formula (1). And (2). In step 90, control is performed so that the braking force Fbf of the left and right front wheels becomes the target braking force Fbft and the braking force Fbr of the left and right rear wheels becomes the target braking force Fbrt, so that the front wheel distribution ratio of the braking force becomes Rf. The braking force of the front and rear wheels is controlled.

  On the other hand, when the target braking force Fbvt of the vehicle is greater than or equal to the reference value Fbvc, an affirmative determination is made in step 40, and in step 80, the target braking force Fbft of the left and right front wheels is calculated according to the above equation (1). The wheel target braking force Fbrt is set to a constant value Fbrc. In step 90, the braking force Fbf of the left and right front wheels becomes the target braking force Fbft, and the braking force Fbrf of the left and right rear wheels is controlled to become the target braking force Fbrt. Although controlled according to the operation amount, the braking force Fbr of the left and right rear wheels is limited to a constant value Fbrc.

<When it is determined that the braking device is abnormal>
If it is determined that the braking device 12 is abnormal, the flag Fab is 1. Therefore, an affirmative determination is made in step 30, the braking device 12 is normal, and the target braking force Fbvt of the vehicle is the reference value. Steps 50, 60 and 90 are executed as if less than Fbvc. That is, the braking force Fbr of the left and right rear wheels is not limited to a constant value Fbrc but is controlled according to the amount of braking operation by the driver. Therefore, when the target braking force Fbvt of the vehicle is greater than or equal to the reference value Fbvc, the braking force Fbf of the left and right front wheels becomes the target braking force Fbft, as shown by the one-dot chain line in FIG. The braking force Fbr is controlled so as to become the target braking force Fbrt.

  When the rear wheel system is normal but the front wheel system is abnormal, the braking force Fbf of the left and right front wheels does not become the target braking force Fbft, but the braking force Fbr of the left and right rear wheels is greater than a certain value Fbrc and driving. The target braking force Fbrt is controlled according to the braking operation amount of the person. Accordingly, the braking force Fbr of the left and right rear wheels is larger than that when the braking force Fbr is limited to a constant value Fbrc. Therefore, the entire vehicle is caused by the limitation of the braking force of the rear wheels by the front and rear wheel braking force distribution control. The degree to which the braking force of the vehicle becomes insufficient and the braking distance of the vehicle becomes long can be reduced.

  Even when the front wheel system is normal but the rear wheel system is abnormal, it is determined in step 180 that the braking device 12 is abnormal, and the flag Fab is set to 1. Accordingly, as in the case where the front wheel system is abnormal, the braking force Fbr of the left and right rear wheels is not limited to a constant value Fbrc, but the rear wheel system cannot normally generate braking force, so The fact that the braking force Fbr is not limited to the constant value Fbrc does not cause any particular inconvenience.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. This will be apparent to those skilled in the art.

  For example, in the above-described embodiment, when the braking force Fbr of the rear wheels is limited to a constant value Fbrc, when the product of the braking slip rates SLf and SLr of the front wheels and the rear wheels is equal to or less than the reference value SLc, It is determined that the braking device 12 is abnormal, and the restriction of the braking force of the rear wheels is stopped. However, the braking force Fbr of the rear wheel only needs to be relaxed by the front and rear wheel braking force distribution control. For example, as shown by a two-dot chain line in FIG. 4, the limited value Fbrc and the unrestricted value The restriction relaxation of the braking force of the rear wheel may be corrected so as to be a value between (a one-dot chain line).

  In the above-described embodiment, the front and rear wheel braking force distribution control is a control in which the target braking force Fbrt for the left and right rear wheels is limited to a constant value Fbrc when the vehicle target braking force Fbvt is equal to or greater than the reference value Fbvc. It is. However, in the front and rear wheel braking force distribution control, when a preset condition is satisfied, as long as the braking force of the rear wheel is limited by limiting the increase of the braking force of the rear wheel accompanying the increase of the braking force of the vehicle, It may be any front and rear wheel braking force distribution control known in the art.

  For example, in the front and rear wheel braking force distribution control, when the vehicle deceleration based on the longitudinal acceleration of the vehicle or the rate of change of the wheel speed is equal to or higher than a reference value, the braking force of the rear wheels is limited according to the vehicle deceleration. It may be a control. Alternatively, the front-rear wheel braking force distribution control is a control in which the braking force of each wheel is controlled according to the support load of the wheel, and the braking force of the rear wheel is limited based on the load movement in the front-rear direction during braking. Good.

  In the above-described embodiment, the front wheel slip ratio SLf and the rear wheel slip ratio SLr are calculated in step 150 as the braking slip index values for the front wheels and the rear wheels. However, the braking slip index values of the front wheels and the rear wheels may be, for example, slip amounts that are numerators on the right side of the above formulas (4) and (5), respectively.

  In the above-described embodiment, the pressure sensor 80 that detects the pressure in the first master cylinder chamber 16A as the master cylinder pressure Pma and the pressure that detects the pressure in the second master cylinder chamber 16B as the master cylinder pressure Pmb. A sensor 82 is provided. However, one pressure sensor may be omitted, and the pressure detected by one pressure sensor may be the master cylinder pressure Pm that is used for the determination in step 120.

  In the above-described embodiment, it is determined in step 120 whether or not the master cylinder pressure Pm is greater than or equal to the reference value Pmc. When an affirmative determination is made, step 130 and subsequent steps are executed. However, when the restriction of the braking force of the rear wheels by the front and rear wheel braking force distribution control is greater than or equal to a preset reference value or the target braking force Fbvt of the vehicle is greater than or equal to a preset reference value. In the case where it is executed, the determination in step 120 may be omitted.

  Furthermore, in the above-described embodiment, the pumps 42F and 42R are provided in the front wheel system 12F and the rear wheel system 12R, respectively. However, the braking device to which the present invention is applied is a front wheel that increases or decreases the braking force of the left and right front wheels. As long as it has a rear wheel system that increases or decreases the braking force of the system and the left and right rear wheels, it may be a braking device of any configuration known in the art. For example, the pumps of the front wheel system and the rear wheel system may be driven by their own electric motors.

DESCRIPTION OF SYMBOLS 10 ... Braking force control device, 12 ... Braking device, 12F ... Front wheel system, 12R ... Rear wheel system, 14 ... Electronic control device, 16 ... Master cylinder, 80, 82 ... Pressure sensor, 84 ... Wheel speed sensor, 86 ... Alarm apparatus

Claims (1)

A braking device having a front wheel system for increasing / decreasing the braking force of the left and right front wheels, a braking device having a rear wheel system for increasing / decreasing the braking force of the left and right rear wheels, and a control device for controlling the braking device, the control device being preset When the condition is satisfied, the vehicle braking force control configured to limit the rear wheel braking force by the front and rear wheel braking force distribution control by limiting the increase in the rear wheel braking force accompanying the increase in the vehicle braking force. In the device
The control device calculates a braking slip index value of the front wheels and the rear wheels in a situation where the braking force of the entire vehicle is equal to or greater than a reference value of the braking force, and calculates the braking slip index value of the front wheels and the braking slip index of the rear wheels. When the product with the value is equal to or less than the reference value of the braking slip index value, the braking device is determined to be abnormal, and the restriction of the braking force of the rear wheel is relaxed.
Vehicle braking force control device.

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