JP3829925B2 - Brake control device for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a braking control device for a vehicle such as an automobile, and more particularly to a braking control device for a vehicle that performs braking force distribution control of front and rear wheels.
[0002]
[Prior art]
As one of the braking control devices for vehicles such as automobiles, when the driving state of the vehicle reaches a predetermined state in order to prevent the rear wheels from locking when the vehicle is braked and to improve the running stability of the vehicle, 2. Description of the Related Art Conventionally, a braking control device configured to perform front and rear wheel braking force distribution control that suppresses an increase in braking force of a rear wheel by holding or reducing a braking pressure or increasing a pulse is known.
[0003]
According to this type of braking control device, the rear wheels are locked before the front wheels and the stability of the vehicle due to this compared to the case where front and rear wheel braking force distribution control is not performed. However, when the front and rear wheel braking force distribution control is executed, the increase in the braking force of the rear wheels is suppressed, so that the driver can increase the braking force. Even if the amount of braking operation is increased to increase the braking force, the braking force of the vehicle as a whole is not sufficiently increased, and the driver may feel uncomfortable with the braking operation.
[0004]
In order to solve such a problem, for example, in Japanese Patent Application Laid-Open No. 2001-219434, which is filed by the applicant of the present application, the amount of braking operation by the driver is determined, and the driving state of the vehicle becomes a predetermined state, and the front and rear wheel braking force distribution is determined. A braking control device is described that is configured to increase the braking force of the rear wheel when it is determined that the amount of braking operation by the driver is increasing in a situation where the control is being executed.
[0005]
[Problems to be solved by the invention]
According to the braking control device described in the above publication, the braking force of the rear wheels is increased when the amount of braking operation by the driver is increased in a situation where the front and rear wheel braking force distribution control is being executed. Therefore, even if the driver increases the amount of braking operation to increase the braking force, the possibility that the driver feels uncomfortable with the braking operation due to the fact that the braking force of the vehicle as a whole does not increase sufficiently is reduced. be able to.
[0006]
However, since the increase range of the braking force allowed for the rear wheels is limited, in the braking control device as described above, the rear wheels are locked before the front wheels, and this is caused by this. There is a problem that the braking force of the entire vehicle cannot be sufficiently increased while reliably preventing the stability of the vehicle from deteriorating.
[0007]
The present invention has been made in view of the above-described problems in the conventional braking control device configured to perform front and rear wheel braking force distribution control that suppresses an increase in the braking force of the rear wheels when the driving state of the vehicle becomes a predetermined state. The main problem of the present invention is that the increase in the braking force of the front wheels is reduced by the shortage of the braking force of the rear wheels by suppressing the increase in the braking force of the rear wheels by the front and rear wheel braking force distribution control. By supplementing, it is possible to prevent the braking force of the entire vehicle from being insufficient without impairing the front and rear wheel distribution control, that is, the rear wheel is locked before the front wheel, and the vehicle That is, the braking force of the entire vehicle is set to a value corresponding to the braking operation amount of the driver while reliably preventing the deterioration of the stability.
[0008]
[Means for Solving the Problems]
  According to the present invention, the above-mentioned main problem is that the braking force is generated by supplying the hydraulic fluid pressure of the master cylinder to the wheel cylinder of the braking force generator provided corresponding to each wheel. When the driving state of the vehicle reaches a predetermined state, the front and rear wheel braking force distribution control is performed using a vehicle braking control device that performs front and rear wheel braking force distribution control that suppresses an increase in the braking force of the rear wheels. The front wheel braking force increasing means for increasing the braking force of the front wheel according to the amount of restraint of the increase in braking force of the rear wheel.The front and rear wheel braking force distribution control sets the rear wheel holding pressure according to the running state of the vehicle at the time when the driving state of the vehicle becomes a predetermined state, and based on the holding pressure, The front wheel braking force increasing means is configured to control the amount of braking operation by the driver, the holding pressure, and the parameter representing the braking performance of the braking force generator for the front and rear wheels. Based on this, the front wheel wheel cylinder pressure increase is calculated, and based on the increase, the front wheel wheel cylinder pressure is increased.This is achieved by a vehicle brake control device.
[0009]
  According to the present invention, in order to effectively achieve the above-mentioned main problems,The predetermined state isFront and rear wheel braking force distribution controlThe start condition of(Structure of claim 2).
[0010]
  According to the present invention, in order to effectively achieve the main problems described above,1 orIn the configuration of 2, the parameter is configured such that the higher the vehicle speed, the lower the braking performance (the configuration of claim 3).
  According to the present invention, in order to effectively achieve the above-mentioned main problem, in the configuration of claim 3, the parameter is configured to include a braking effectiveness coefficient of a braking force generator. 4 configuration).
  Further, according to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 4, the brake effectiveness coefficient is estimated based on the vehicle speed (claim 5). Constitution).
  According to the present invention, in order to effectively achieve the above main problem, in the structure according to any one of claims 1 to 5, the braking control device causes the vehicle operating state to be in the predetermined state. The holding pressure is configured to be variably set according to the vehicle speed at that time.
  According to the present invention, in order to effectively achieve the above main problem, in the structure according to any one of claims 1 to 5, the braking control device causes the vehicle operating state to be in the predetermined state. The holding pressure is variably set according to the deceleration of the vehicle at the time point (the configuration of claim 7).
[0011]
[Action and effect of the invention]
  According to the configuration of claim 1 above,The holding pressure of the rear wheel is set according to the running state of the vehicle when the driving state of the vehicle becomes a predetermined state, and the increase in the wheel cylinder pressure of the rear wheel is suppressed based on the holding pressure. Front and rear wheel braking force distribution control is performed,When the front / rear wheel braking force distribution control is being performed,RetentionSince the braking force of the front wheels increases according to the pressure, the front and rear wheel braking force distribution control is performed and the rear wheelsWheel cylinder pressureThe shortage of the braking force of the rear wheel due to the suppression of the increase in the force can be reliably compensated by increasing the braking force of the front wheel, so that the rear wheel is locked before the front wheel and this Thus, the braking force of the entire vehicle can be effectively controlled to the braking force corresponding to the amount of braking operation by the driver while reliably preventing the vehicle stability from deteriorating.
  According to the first aspect of the present invention, the wheel cylinder pressure increase of the front wheel is based on the amount of braking operation by the driver, the holding pressure of the rear wheel, and the parameter representing the braking performance of the braking force generator for the front wheel and the rear wheel. Since the amount is calculated and the wheel cylinder pressure of the front wheel is increased based on the increased amount, it is necessary to compensate the insufficient braking force by increasing the braking force of the front wheel by suppressing the increase of the wheel cylinder pressure of the rear wheel The wheel cylinder pressure of the front wheels is increased by a small increase amount, so that the braking force of the entire vehicle can be reliably controlled to the braking force according to the driver's braking operation amount.
[0013]
  Generally, the braking performance of a braking force generator that generates a braking force by supplying the hydraulic fluid pressure of the master cylinder to the wheel cylinder decreases as the vehicle speed increases.1 or 2The parameter representing the braking performance of the braking force generating device for the front wheels and the rear wheels used in calculating the amount of increase in the wheel cylinder pressure for the front wheels according to the configuration of the above is a parameter representing the braking performance of the braking force generating device as the vehicle speed increases. It is preferable.
[0014]
  According to the above configuration of the third aspect, the amount of increase in the wheel cylinder pressure of the front wheel is determined by the amount of braking operation by the driver,RetentionThe calculation is based on the pressure and a parameter representing the braking performance of the braking force generators for the front and rear wheels. In this case, the parameter is a parameter representing a lower braking performance as the vehicle speed is higher. The amount of increase in the wheel cylinder pressure of the front wheels can be calculated in consideration of the braking performance of the power generation device, and thus the wheel cylinder pressure of the front wheels can be appropriately increased regardless of the vehicle speed.
  According to the fourth aspect of the invention, since the parameter includes the braking effectiveness coefficient of the braking force generator, the amount of increase in the wheel cylinder pressure of the front wheel is controlled as compared with the case where the variation of the braking effectiveness coefficient is not taken into consideration. It is possible to calculate a value that accurately corresponds to the shortage of power, and thereby to properly control the wheel cylinder pressure of the front wheels without excess or deficiency.
  According to the fifth aspect of the present invention, since the braking effectiveness coefficient is estimated based on the vehicle speed, the amount of increase in the wheel cylinder pressure of the front wheels is appropriately calculated in consideration of the fact that the braking effectiveness coefficient decreases as the vehicle speed increases. be able to.
  Further, according to the configuration of the sixth aspect, since the holding pressure is variably set according to the vehicle speed when the driving state of the vehicle becomes a predetermined state, the braking control device is compared with the case where the vehicle speed is not considered. Thus, the holding pressure of the rear wheels can be set appropriately, and accordingly, the front and rear wheel braking force distribution control can be properly executed according to the situation of the vehicle.
  According to the seventh aspect of the present invention, the braking control device variably sets the holding pressure in accordance with the deceleration of the vehicle when the driving state of the vehicle becomes a predetermined state. The rear wheel holding pressure can be set appropriately as compared with the case where the above is not taken into consideration, and accordingly, the front and rear wheel braking force distribution control can be appropriately executed in accordance with the situation of the vehicle.
[0017]
[Preferred embodiment of the problem solving means]
  The present inventionOneAccording to one preferred embodiment, the above claimsAny one of 1-7The front wheel braking force increasing means is the master cylinder pressure and the rear wheelRetentionIt is configured to calculate a wheel cylinder pressure increase amount of the front wheels based on a deviation from the pressure and a parameter representing the braking performance of the braking force generating device for the front wheels and the rear wheels (preferred embodiment)1).
[0019]
  According to another preferred embodiment of the invention, the above claimsAny one of 1-7In this configuration, the braking control device sets the master cylinder pressure at the time when the vehicle operation state reaches a predetermined state to the holding pressure of the rear wheel, and maintains the braking pressure of the rear wheel at the holding pressure. (Preferred aspect 2)
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0023]
FIG. 1 is a schematic configuration diagram showing a hydraulic circuit and an electronic control device of one embodiment of a braking control device according to the present invention, and FIG. 2 is an illustrative sectional view showing a front wheel communication control valve shown in FIG. is there. In FIG. 1, the solenoid of each valve that is electromagnetically driven is not shown.
[0024]
In FIG. 1, reference numeral 10 denotes a hydraulic braking device, and the braking device 10 has a master cylinder 14 that pumps brake oil in response to a depression operation of a brake pedal 12 by a driver. The master cylinder 14 has a first master cylinder chamber 14A and a second master cylinder chamber 14B defined by free pistons 16 biased to predetermined positions by compression coil springs on both sides thereof.
[0025]
One end of a front wheel brake hydraulic control conduit 18F is connected to the first master cylinder chamber 14A, and the other brake brake control conduit 18F is connected to the left front wheel brake hydraulic control conduit 20FL and the right front wheel brake hydraulic control. One end of the conduit 20FR is connected. A communication control valve 22F for the front wheels is provided in the middle of the brake hydraulic control conduit 18F, and the communication control valve 22F is a normally open linear solenoid valve in the illustrated embodiment. Connected to the brake hydraulic control conduits 18F on both sides of the communication control valve 22F are check bypass conduits 24F that permit only the flow of oil from the first master cylinder chamber 14A toward the brake hydraulic control conduit 20FL or the brake hydraulic control conduit 20FR. Yes.
[0026]
As shown schematically in FIG. 2, the communication control valve 22F has a housing 72 that defines a valve chamber 70 therein, and a valve element 74 is disposed in the valve chamber 70 so as to be capable of reciprocating. . A portion 18FA of the brake hydraulic pressure control conduit 18F on the master cylinder 14 side is always connected to the valve chamber 70 via an internal passage 76, and a portion 18FB of the brake hydraulic pressure control conduit 18F opposite to the master cylinder 14 is internally connected. A communication connection is established via a passage 78 and a port 80.
[0027]
As shown in the figure, a solenoid 82 is disposed around the valve element 74, and the valve element 74 is urged to a valve opening position shown in FIG. 2 by a compression coil spring 84. When a drive voltage is applied to the solenoid 82, the valve element 74 is urged against the port 80 against the spring force of the compression coil spring 84, thereby closing the port 80.
[0028]
In the situation where the communication control valve 22F is in the closed position, the sum of the force of the pressure in the portion 18FB on the opposite side of the master cylinder 14 of the brake hydraulic control conduit 18F and the spring force of the compression coil spring 84 is the solenoid. When the electromagnetic force is increased by the pressure 82, the valve element 74 opens away from the port 80, and the oil in the portion 18FB passes through the internal passage 78, the port 80, the valve chamber 70, the internal passage 76, and the brake hydraulic control conduit 18F. To the part 18FA. When the oil pressure in the portion 18FB decreases due to this oil flow, the sum of the force by the pressure and the spring force of the compression coil spring 84 becomes lower than the electromagnetic force by the solenoid 82, and the valve element 74 causes the port 80 to Close again.
[0029]
Thus, since the communication control valve 22F controls the pressure in the portion 18FB of the brake hydraulic pressure control conduit 18F according to the voltage applied to the solenoid 82, the communication control valve 22F controls the pressure in the portion 18FB by controlling the driving voltage for the solenoid 82. The pressure (referred to herein as “upstream pressure”) can be controlled to a desired pressure.
[0030]
In the illustrated embodiment, the check bypass conduit 24F shown in FIG. 1 is built in the communication control valve 22F, and is provided with an internal passage 86 and a part from the valve chamber 70 provided in the middle of the internal passage. It consists of a check valve 88 that allows only the flow of oil toward 18FB.
[0031]
A brake force generator wheel not shown in FIG. 1 generates braking force for the left front wheel and right front wheel at 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. Cylinders 26FL and 26FR are connected, and normally open electromagnetic on-off valves 28FL and 28FR are provided in the middle 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. 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. .
[0032]
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 oil is discharged to the brake hydraulic control conduit 20FR between the electromagnetic on-off valve 28FR and the wheel cylinder 26FR. One end of the conduit 32FR is connected. Normally closed solenoid valves 34FL and 34FR are provided in the middle of the oil discharge conduits 32FL and 32FR, respectively, and the other ends of the oil discharge conduits 32FL and 32FR are connected to a front wheel buffer reservoir 38F by a connection conduit 36F. ing.
[0033]
As understood from the above description, 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, and the electromagnetic on-off valves 34FL and 34FR are in the wheel cylinders 26FL and 26FR, respectively. Therefore, the electromagnetic on-off valves 28FL and 34FL cooperate with each other to define an increasing / decreasing valve for increasing and decreasing the pressure in the wheel cylinder 26FL of the left front wheel, The electromagnetic open / close 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.
[0034]
The connection conduit 36F is connected to the suction side of the pump 42F by the connection conduit 40F, and two check valves 44F and 46F that allow only the flow of oil from the connection conduit 36F to the pump 42F are provided in the connection conduit 40F. 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 on the way. 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.
[0035]
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 a brake between the first master cylinder chamber 14A and the control valve 22F. It is connected to the hydraulic control conduit 18F. A normally closed electromagnetic on-off valve 60F is provided in the middle of the connecting conduit 54F. The electromagnetic on-off valve 60F functions as a suction control valve that controls communication between the brake hydraulic pressure control conduit 18F between the master cylinder 14 and the control valve 22F and the suction side of the pump 42F.
[0036]
Similarly, one end of a brake oil pressure control conduit 18R for the rear wheel is connected to the second master cylinder chamber 14B, and the brake oil pressure control conduit 20RL for the left rear wheel and the right rear wheel are connected to the other end of the brake oil pressure control conduit 18R. One end of a brake hydraulic control conduit 20RR for the wheel is connected. A rear wheel communication control valve 22R, which is a normally open linear solenoid valve, is provided in the middle of the brake hydraulic control conduit 18R.
[0037]
The communication control valve 22R has the same structure as that shown in FIG. 2 with respect to the front wheel communication control valve 22F. Therefore, the communication control valve 22R is controlled by controlling the drive voltage for the solenoid not shown in the figure. The pressure (upstream pressure) in the brake hydraulic pressure control conduit 18R downstream of the valve 22R can be controlled to a desired pressure. Further, a check bypass conduit 24R allowing only the flow of oil from the second master cylinder chamber 14B to the brake hydraulic control conduit 20RL or the brake hydraulic control conduit 20RR is connected to the brake hydraulic control conduit 18R on both sides of the communication control valve 22R. ing.
[0038]
A braking force not shown in FIG. 1 is generated at 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. The wheel cylinders 26RL and 26RR of the generator are connected, and normally open type electromagnetic on-off valves 28RL and 28RR are provided in the middle 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. Is provided. 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. .
[0039]
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 oil is discharged to the brake hydraulic control conduit 20RR between the electromagnetic on-off valve 28RR and the wheel cylinder 26RR. One end of the conduit 32RR is connected. In the middle of the oil discharge conduits 32RL and 32RR, normally closed electromagnetic on-off valves 34RL and 34RR are provided, respectively, and the other ends of the oil discharge conduits 32RL and 32RR are connected to a rear wheel buffer reservoir 38R by a connection conduit 36R. Has been.
[0040]
As in the case of the front wheel side, 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 in the wheel cylinders 26RL and 26RR, respectively. Therefore, the electromagnetic on-off valves 28RL and 34RL cooperate with each other to define an increase / decrease valve for increasing and decreasing the pressure in the wheel cylinder 26RL of the left rear wheel. The electromagnetic on-off valves 28RR and 34RR cooperate with each other to define an increasing / decreasing valve for increasing and decreasing the pressure in the wheel cylinder 26RR of the right rear wheel.
[0041]
The connecting conduit 36R is connected to the suction side of the pump 42R by a connecting conduit 40R, and two check valves 44R and 46R that allow only the flow of oil from the connecting conduit 36R to the pump 42R are provided in the connecting conduit 40R. 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 on the way. A connection conduit 50R between the pump 42R and the damper 48R is provided with a check valve 52R that allows only an oil flow from the pump 42R to the damper 48R. The pumps 42F and 42R are driven by a common electric motor not shown in FIG.
[0042]
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 a brake between the second master cylinder chamber 14B and the control valve 22R. It is connected to the hydraulic control conduit 18R. A normally closed electromagnetic on-off valve 60R is provided in the middle of the connecting conduit 54R. This electromagnetic on-off valve 60R also functions as a suction control valve that controls communication between the brake hydraulic pressure control conduit 18R between the master cylinder 14 and the control valve 22R and the suction side of the pump 42R.
[0043]
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 drive current is not applied to the corresponding solenoid, whereby the wheel cylinders 26FL and 26FR are set. The pressure in the first master cylinder chamber 14A is supplied, and the pressure in the second master cylinder chamber 14B is supplied to the wheel cylinders 26RL and 26RR. Therefore, at normal times, the pressure in the wheel cylinder of each wheel, that is, the braking force is increased or decreased according to the depression force of the brake pedal 12.
[0044]
On the other hand, the communication 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 in a state where the on-off valves of the wheels are at the positions shown in FIG. When driven, the oil in the master cylinder 14 is pumped up by the pump, the pressure pumped up by the pump 42F is supplied to the wheel cylinders 26FL, 26FR, and the pumping up by the pump 42R is supplied to the wheel cylinders 26RL, 26RR. Since the pressure is supplied, the braking pressure of each wheel is increased / decreased by opening / closing the communication control valves 22F, 22R and the opening / closing valves (increasing / reducing valves) of each wheel regardless of the depression force of the brake pedal 12.
[0045]
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), and the on-off valves 28FL to 28RR are closed. When it is switched to the valve position and the on-off valves 34FL to 34RR are in the non-control position shown in FIG. 1, it is held (holding mode), and the on-off valves 28FL to 28RR and the on-off valves 34FL to 34RR are switched to the open position. The pressure is reduced (pressure reduction mode).
[0046]
The communication control valves 22F and 22R, the open / close valves 28FL to 28RR, the open / close valves 34FL to 34RR, and the open / close valves 60F and 60R are controlled by the electronic control unit 90 as described later. The electronic control unit 90 includes a microcomputer 92 and a drive circuit 94, and the microcomputer 92 may have a general configuration well known in the art.
[0047]
The microcomputer 92 receives a signal indicating the master cylinder pressure Pm from the pressure sensor 96, a signal indicating the vehicle speed V from the vehicle speed sensor 98, and a signal indicating the longitudinal acceleration Gx of the vehicle from the longitudinal acceleration sensor 100. The microcomputer 92 stores a braking control flow, which will be described later, and calculates the target braking pressure Pti (i = fl, fr, rl, rr) for the left and right front wheels and the left and right rear wheels according to the braking control flow. By controlling 22F and the like, the braking pressure Pi (i = fl, fr, rl, rr) of each wheel is controlled to the corresponding target braking pressure Pti.
[0048]
  In particular, in the illustrated embodiment, when the amount of braking operation by the driver is small and the front / rear distribution control of the braking force is unnecessary, the communication control valve 22F and the like are maintained in the illustrated standard position and the pumps 42F and 42R are driven. Thus, the braking pressure of each wheel, that is, the wheel cylinder 26FL~ 2The pressure in 6RR is controlled by the master cylinder pressure Pm.
[0049]
On the other hand, when the amount of braking operation by the driver is large and the front / rear distribution control of the braking force is necessary, the communication control valves 22F and 22R are first closed, then the intake control valves 60F and 60R are opened, and then the pump The driving of 42F and 42R is started, and the holding pressure Pc of the rear wheel is calculated based on the vehicle speed V and the deceleration Gxb (= −Gx) of the vehicle, as will be described in detail later, and the master cylinder pressure Pm and the rear wheel The front wheel increase pressure ΔPf is calculated based on the holding pressure Pc and the like, and the communication control valve 22F is controlled to control the front wheel system so that the upstream pressure on the front wheel side becomes the target braking pressure of Pm + ΔPf. By closing the valves 28RL and 28RR, the rear wheel system is controlled so that the braking pressure of the left and right rear wheels becomes the holding pressure Pc.
[0050]
Although not shown in the figure, the electromagnetic on-off valves 28FL to 28RR and the on-off valves 34FL to 34RR are controlled, for example, when the behavior of the vehicle is stabilized by individually controlling the braking force of each wheel. Particularly in this case, the higher target braking pressure of the left and right wheels is set to the target upstream pressure Ptf, Ptr, and the braking pressure Pi of the wheel having the higher target braking pressure Pti of the left and right wheels is upstream by the communication control valve 22F or 22R. The pressure is controlled by controlling to the target upstream pressure Ptf or Ptr, and the braking pressure of the left and right wheels is controlled to the corresponding target braking pressure by the corresponding pressure increasing valve and the pressure reducing valve.
[0051]
Next, the braking control routine in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 3 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals.
[0052]
  First, in step 10, a signal indicating the master cylinder pressure Pm detected by the pressure sensor 96 is read, and in step 20, it is determined whether or not the braking force distribution control of the front and rear wheels is being performed. That is, after an affirmative determination is made in step 30 to be described later,9It is determined whether or not an affirmative determination is made at 0. If an affirmative determination is made, the process proceeds to step 90. If a negative determination is made, the process proceeds to step 30.
[0053]
In step 30, the basic holding pressure Pcs of the rear wheels is calculated from a map corresponding to the graph shown in FIG. 4 on the basis of the vehicle speed V, and in step 40, it is shown in FIG. 5 based on the deceleration Gxb of the vehicle. The correction pressure ΔPc for the basic holding pressure Pcs is calculated from the map corresponding to the graph, and in step 50, the rear wheel holding pressure Pc is calculated as the sum of the basic holding pressure Pcs and the correction pressure ΔPc. Note that Gxbo in FIG. 5 is a standard vehicle deceleration during vehicle braking.
[0054]
  In step 60, the master cylinder pressure Pm exceeds the rear wheel holding pressure Pc.The start condition for braking force distribution control for the front and rear wheels is satisfied.Is determined, that is, whether it is necessary to maintain the braking pressure of the rear wheels and increase the braking pressure of the front wheels. If a negative determination is made, the process proceeds to step 70, where an affirmative determination is made. If so, go to Step 100.
[0055]
In step 70, it is determined whether or not other starting conditions for the braking force distribution control for the front and rear wheels are established in any manner known in the art, and when a negative determination is made. If the control by the routine shown in FIG. 3 is once finished and an affirmative determination is made, the rear wheel holding pressure Pc is set to the master cylinder pressure Pm at step 80, and then the routine proceeds to step 100. .
[0056]
Whether or not other starting conditions for the braking force distribution control for the front and rear wheels are satisfied is determined by, for example, (A) Deviation ΔVw of the average wheel speed Vwr of the left and right rear wheels with respect to the average wheel speed Vwf of the left and right front wheels. Or (B) by determining whether the vehicle deceleration Gxb is equal to or greater than the control start reference value Gxs (positive constant). Or may be performed by a combination of the above (A) and (B).
[0057]
In step 90, for example, by determining whether or not the master cylinder pressure Pm has become equal to or less than the control end reference value Pme (a positive constant smaller than Pc), the end condition of the braking force distribution control for the front and rear wheels is established. 3 is determined. If the determination is affirmative, the control according to the routine shown in FIG. 3 is temporarily terminated. If the determination is negative, the process proceeds to step 100.
[0058]
It should be noted that whether or not the condition for terminating the braking force distribution control for the front and rear wheels has been satisfied may be determined in any manner known in the art. When it is performed based on ΔVw, it may be performed by determining whether or not the wheel speed deviation ΔVw is equal to or less than the control end reference value Vwe (a positive constant smaller than Vws). When the establishment determination is made based on the vehicle deceleration Gxb, it may be performed by determining whether or not the vehicle deceleration Gxb is equal to or less than a control end reference value Gxe (a positive constant smaller than Gxs). .
[0059]
In step 100, the wheel cylinder cross-sectional areas of the front and rear wheels are set to Sf and Sr (positive constants), and the braking effective radii of the front and rear wheels are set to Rf and Rr (positive constants), respectively. The basic increase pressure ΔPfo of the braking pressure of the front wheels is calculated according to the following equation 1 with the wheel braking effectiveness coefficients being BEFf and BEFr (positive constants), respectively. The wheel cylinder cross-sectional areas Sf and Sr and the effective braking radii Rf and Rr are values determined by the specifications of the braking force generator, and the braking effectiveness coefficients BEFf and BEFr are obtained in advance experimentally, for example.
ΔPfo = (Pm−Pc) (Sr × Rr × BEFr) / (Sf × Rf × BEFf) (1)
[0060]
In step 110, the braking effectiveness coefficient BEFv corresponding to the current vehicle speed is calculated from the map corresponding to the graph shown in FIG. 6 based on the vehicle speed V, and the standard braking effectiveness coefficient BEFo and the current braking effectiveness coefficient BEFv are calculated. Deviation ΔBEF (= BEFo−BEFv) is calculated, and an increase pressure ΔPf of the braking pressure of the front wheels is calculated according to the following equation 2. A map corresponding to the graph shown in FIG. 6 is also obtained in advance experimentally, for example.
ΔPf = ΔPfo (1 + ΔBEF / BEFo) (2)
[0061]
In step 120, the target braking pressures Ptfl and Ptfr for the left and right front wheels are calculated as the sum of the master cylinder pressure Pm and the increased pressure ΔPf, and braking is performed so that the braking pressures for the left and right front wheels become the target braking pressures Ptfl and Ptfr, respectively. The front wheel system of the apparatus 10 is controlled, and in step 130, the target braking pressures Ptrl and Ptrr for the left and right rear wheels are set to the holding pressure Pc, and the braking pressures for the left and right rear wheels are set to the target braking pressures Ptrl and Ptrr, respectively. Thus, the rear wheel system of the braking device 10 is controlled.
[0062]
Although not shown in FIG. 3, if a negative determination is made in step 70 and an affirmative determination is made in step 90, the communication control valve 22F and the like are shown in FIG. Accordingly, the pressure Pm of the master cylinder 14 is directly supplied to the wheel cylinders 26FR to 26RR of each wheel, whereby the braking pressure of each wheel is increased or decreased according to the braking operation amount of the driver. Is done.
[0063]
Thus, according to the illustrated embodiment, when the braking force distribution control for the front and rear wheels is not being executed, a negative determination is made in step 20, and the basic holding pressure Pcs of the rear wheels is determined based on the vehicle speed V in step 30. In step 40, the correction pressure ΔPc for the basic holding pressure Pcs is calculated based on the vehicle deceleration Gxb. In step 50, the rear wheel holding pressure Pc is calculated as a difference between the basic holding pressure Pcs and the correction pressure ΔPc. Calculated as sum.
[0064]
When the master cylinder pressure Pm is equal to or lower than the rear wheel holding pressure Pc and the other starting conditions for the braking force distribution control for the front and rear wheels are not satisfied, it is not necessary to suppress the braking force for the rear wheels. In this case, a negative determination is made, and the pressure in the master cylinder 14 is supplied to the front and rear wheel cylinders 26FL to 26RR. Therefore, the control of suppressing the braking pressure of the rear wheel and the control of increasing the braking pressure of the front wheel are performed. I will not.
[0065]
  On the other hand, the braking operation amount by the driver is further increased, and the master cylinder pressure Pm exceeds the rear wheel holding pressure Pc.The start condition for braking force distribution control for the front and rear wheels is satisfied.If a positive determination is made in step 60 and the master cylinder pressure Pm does not exceed the rear wheel holding pressure Pc, another start condition of the front and rear wheel braking force distribution control is satisfied. In step 70, an affirmative determination is made. In step 80, the holding pressure Pc of the rear wheel is set to the current master cylinder pressure Pm. In step 100, the master cylinder pressure Pm and the holding pressure Pc of the rear wheel are determined. The basic increase pressure ΔPfo of the front wheel braking pressure is calculated according to the above equation 1 based on the deviation Pm−Pc of the vehicle, and the brake effectiveness coefficient BEFv corresponding to the current vehicle speed is calculated based on the vehicle speed V in step 110 to obtain the standard brake. A deviation ΔBEF between the effectiveness coefficient BEFo and the current braking effectiveness coefficient BEFv is calculated, and an increase pressure ΔPf of the braking pressure of the front wheels is calculated according to the above equation 2.
[0066]
Further, in step 120, the front wheel system of the braking device 10 is controlled so that the braking pressure of the left and right front wheels becomes the target braking pressures Ptfl and Ptfr calculated as the sum of the master cylinder pressure Pm and the increased pressure ΔPf. The rear wheel system of the braking device 10 is controlled so that the braking pressures of the left and right rear wheels become the target braking pressures Ptrl and Ptrr = holding pressure Pc of the left and right rear wheels.
[0067]
Therefore, according to the illustrated embodiment, when the start condition of the front and rear wheel braking force distribution control is satisfied, the master cylinder pressure Pm exceeds the rear wheel holding pressure Pc until the end condition of the front and rear wheel braking force distribution control is satisfied. In this situation, the braking pressure of the rear wheel is maintained at the holding pressure Pc, so that it is possible to reliably prevent the rear wheel from being locked prior to the front wheel, and the braking pressure of the rear wheel is maintained at the holding pressure. An increase amount ΔPf of the front wheel braking pressure corresponding to the shortage of the braking force due to being maintained at Pc is calculated and the front wheel braking pressure is increased by ΔPf, so that the rear wheel braking pressure is maintained. Insufficient braking force for the vehicle as a whole is compensated by an increase in the braking force of the front wheels, so that the braking force of the vehicle as a whole can be reliably controlled to correspond to the amount of braking operation performed by the driver even during execution of front and rear wheel braking force distribution control. Power can be controlled.
[0068]
FIG. 7 shows the relationship between the braking force Fbf of the front wheels and the braking force Fbr of the rear wheels in the illustrated embodiment. In particular, the two-dot chain line indicates the ideal front-rear distribution line, and the solid line indicates the embodiment. The front and rear distribution lines are shown. As shown in the figure, when the braking force Fbf of the front wheel is equal to or less than the braking force Fbfc corresponding to the holding pressure Pc of the rear wheel, the braking force Fbf of the front wheel and the braking force Fbr of the rear wheel increase as the master cylinder pressure Pm increases. Although the front wheel braking force Fbf exceeds the braking force Fbfc corresponding to the rear wheel holding pressure Pc, the actual front / rear distribution line of the braking force is the ideal front / rear distribution line. The braking force Fbr of the rear wheels is maintained at the braking force Fbrc corresponding to the holding pressure Pc so as not to exceed the distribution line.
[0069]
8 indicates the relationship between the master cylinder pressure Pm, the front wheel braking pressure Pf, and the rear wheel braking pressure Pr in the illustrated embodiment, and the two-dot chain line indicates front and rear wheel braking force distribution control. The relationship between the master cylinder pressure Pm, the front wheel braking pressure Pf, and the rear wheel braking pressure Pr when the control is not performed is shown.
[0070]
As shown in FIG. 8, when the master cylinder pressure Pm is less than the holding pressure Pc, the front wheel braking pressure Pf and the rear wheel braking pressure Pr are the master cylinder pressure Pm, which are the same. When the cylinder pressure Pm exceeds the holding pressure Pc, the rear wheel braking pressure Pr is the holding pressure Pc (constant). If the current master cylinder pressure Pm is Pma, the rear wheel braking pressure is suppressed. An increase amount ΔPf of the front wheel braking pressure corresponding to the amount of suppression of the braking force of the rear wheels corresponding to the amount ΔPr (= Pma−Pc) is calculated, and the braking pressure Pf of the front wheels is controlled to Pma + ΔPf.
[0071]
Particularly, according to the illustrated embodiment, the increase amount ΔPf of the braking pressure of the front wheel is not simply set to the suppression amount ΔPr of the braking pressure of the rear wheel, but the braking force of the rear wheel due to the suppression of the braking pressure of the rear wheel. Is calculated as a value for adding the braking force corresponding to the deficiency of the front wheel to the braking force of the front wheels, so that compared with the case where the braking pressure of the front wheels is set to the master cylinder pressure Pma + the braking pressure suppression amount ΔPr of the rear wheels. Thus, the braking force of the entire vehicle can be controlled reliably and accurately to a value corresponding to the driver's braking operation amount.
[0072]
In general, as the vehicle speed V increases, the braking effectiveness of the front wheels decreases compared to the rear wheels, and as a result, the front-rear distribution of braking force becomes closer to the rear wheels. Therefore, the higher the vehicle speed V, the higher the holding pressure of the rear wheels. Pc is preferably set low. In general, the higher the vehicle load is, the closer the ideal front-rear distribution line of the braking force is to the rear wheel, and the higher the vehicle load is, the lower the deceleration of the vehicle and the greater the burden on the front wheels related to vehicle braking. It is preferable that the rear wheel holding pressure Pc is set higher as the vehicle deceleration at the start of braking force front-rear distribution control is lower.
[0073]
  According to the illustrated embodiment, the holding pressure Pc is not set to a constant value,305Since the rear wheel holding pressure Pc is variably set according to the vehicle speed V and the vehicle deceleration Gxb so as to decrease as the vehicle speed V increases at 0 and decrease as the vehicle deceleration Gxb increases. The rear wheel holding pressure Pc can be appropriately set as compared with the case where the deceleration Gxb is not taken into consideration, and accordingly, the front and rear wheel braking force distribution control can be appropriately executed in accordance with the state of the vehicle.
[0074]
Further, according to the illustrated embodiment, in step 110, the increase pressure ΔPf of the front wheel braking pressure is calculated considering that the braking effectiveness coefficient BEF decreases as the vehicle speed V increases. Compared to the case where fluctuations are not taken into account, the increase pressure ΔPf of the braking pressure of the front wheels can be calculated to a value that accurately corresponds to the shortage of the braking force of the rear wheels. Can be controlled.
[0075]
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. It will be apparent to those skilled in the art.
[0076]
For example, in the illustrated embodiment, the holding pressure Pc of the rear wheel is set to a constant value until the termination condition of the braking force front / rear wheel distribution control is satisfied. Depending on the state, the rear wheel braking pressure Pc may be gradually decreased or gradually increased, and the rear wheel braking pressure may be gradually decreased or gradually increased by pulse pressure increase.
[0077]
In the above embodiment, the rear wheel holding pressure Pc is variably set in steps 50 and 60 according to the vehicle speed V and the vehicle deceleration Gxb. The pressure Pc may be modified so as to be variably set only in accordance with one of the vehicle speed V and the vehicle deceleration Gxb. Further, as shown in FIG. 9 as a modified example, the rear wheel holding pressure Pc is It may be set to a constant value without being variably set according to V and vehicle deceleration Gxb.
[0078]
In the above-described embodiment, the rear wheel holding pressure Pc is calculated in steps 100 and 110 in consideration of the change in the braking effectiveness coefficient of the braking force generator based on the vehicle speed V. However, the correction of the holding pressure Pc of the rear wheel based on the change in the braking effectiveness coefficient may be omitted.
[0079]
In the above-described embodiment, the left and right front wheels and the left and right rear wheels are controlled to the same pressure during the front and rear wheel distribution control of the braking force. For example, the turning situation of the vehicle and the vehicle The braking pressure of the left and right front wheels or the braking pressure of the left and right rear wheels may be modified so as to be controlled to different values depending on the behavior.
[0080]
Further, in the above-described embodiment, the left and right front wheels and the left and right rear wheels form one system, and the braking pressure of each system is controlled mainly by the communication control valves 22F and 22R. As long as the braking device to which the device is applied can control the braking pressure of the front wheels to a value higher than the master cylinder pressure, and can control the braking pressure of the rear wheels to a value lower than the master cylinder pressure. Any configuration known in the art may be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a hydraulic circuit and an electronic control device of one embodiment of a braking control device according to the present invention.
FIG. 2 is an illustrative sectional view showing a front wheel communication control valve shown in FIG. 1;
FIG. 3 is a flowchart showing a braking force distribution control routine for front and rear wheels in the illustrated embodiment.
FIG. 4 is a graph showing a relationship between a vehicle speed V and a rear wheel basic holding pressure Pcs.
FIG. 5 is a graph showing a relationship between a vehicle deceleration Gxb and a correction pressure ΔPc with respect to a basic holding pressure Pcs.
FIG. 6 is a graph showing a relationship between a vehicle speed V and a brake effectiveness coefficient BEF.
FIG. 7 is a graph showing an ideal front / rear distribution line and a relationship between a braking pressure Pf for a front wheel and a braking pressure Pr for a rear wheel in the illustrated embodiment.
FIG. 8 is a graph showing a relationship between a master cylinder pressure Pm, a front wheel braking pressure Pf, and a rear wheel braking pressure Pr in the illustrated embodiment;
FIG. 9 is a flowchart showing a braking force distribution control routine for front and rear wheels in a modification of the illustrated embodiment.
[Explanation of symbols]
10 ... Brake device
14 ... Master cylinder
22F, 22R ... Communication control valve
26FL, 26FR, 26RL, 26RR ... Wheel cylinder
42F, 42R ... Oil pump
28FL-28RR, 34FL-34RR ... Open / close valve
42F, 42R ... Pump
60F, 60R ... Suction control valve
70 ... Valve
74 ... Valve element
84 ... Compression coil spring
88 ... Check valve
90 ... Electronic control unit
96 ... Pressure sensor
98 ... Vehicle speed sensor
100: longitudinal acceleration sensor

Claims (7)

A braking force is generated by supplying the hydraulic pressure of the master cylinder to a wheel cylinder of a braking force generator provided corresponding to each wheel, and when the driving state of the vehicle reaches a predetermined state, the braking force of the rear wheel is reduced. In a vehicle braking control device that performs front / rear wheel braking force distribution control that suppresses the increase, when the front / rear wheel braking force distribution control is being performed, the braking force of the front wheels is adjusted according to the amount of increase in the rear wheel braking force. have a front wheel braking force increasing means for increasing, to set the holding pressure of the rear wheels according to the running state of the at vehicle at the time the front and rear wheel braking force distribution control is the operation state of the vehicle becomes a predetermined state, The front wheel braking force increasing means generates the braking operation amount by the driver, the holding pressure, and the front and rear wheel braking force generation based on the holding pressure. Device braking performance It calculates the wheel cylinder pressure increase of the front wheel based on the parameter representing the braking control device of the vehicle, characterized in Rukoto increasing the wheel cylinder pressure of the front wheel on the basis of the increase. Wherein the predetermined condition is vehicle brake control device according to claim 1, wherein the state der Rukoto the starting condition of the front and rear wheel braking force distribution control is satisfied. The parameter is vehicle brake control device according to claim 1 or 2, characterized in that the vehicle speed is a parameter representing low higher braking performance. The vehicle braking control device according to claim 3, wherein the parameter includes a braking effectiveness coefficient of the braking force generation device. 5. The vehicle braking control apparatus according to claim 4, wherein the braking effectiveness coefficient is estimated based on a vehicle speed. 6. The vehicle according to claim 1, wherein the braking control device variably sets the holding pressure in accordance with a vehicle speed at a time when the driving state of the vehicle becomes the predetermined state. Braking control device. 6. The braking control device according to claim 1, wherein the braking control device variably sets the holding pressure in accordance with the deceleration of the vehicle at the time when the driving state of the vehicle becomes the predetermined state. Vehicle brake control device.

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