JP4965469B2 - Brake control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking apparatus with a so-called X-shaped piping, capable of, when performing an antiskid control during a braking force distribution control of front and rear wheels, preventing a braking pressure of the rear wheels from becoming unnecessarily high to improve traveling stability of a vehicle. <P>SOLUTION: When a holding pressure Pc of the rear wheel is calculated based on a vehicle speed V and a deceleration Gxb of the vehicle (S50 to S70) and a starting condition of the braking force distribution control of the front and rear wheels is established (S60 and S70), an increased pressure &Delta;Pf of the braking pressure of the front wheel is calculated based on a deviation Pm-Pc of a master cylinder pressure Pm and the holding pressure Pc of the rear wheel (S150 and S160), the braking pressure of the front wheel is controlled to be the sum of the master cylinder pressure Pm and the increased pressure &Delta;Pf (S170), and the braking pressure of the rear wheel is controlled to be the holding pressure Pc (S190). When the antiskid control is started during the braking force distribution control of the front and rear wheels (S90), the increased pressure &Delta;Pf of the braking pressure of the front wheel is gradually reduced (S100 and 130), and the holding pressure Pc of the braking pressure of the rear wheel is gradually increased (S180 and S200). <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  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.

  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.

  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.

In order to solve this problem, for example, in the following Patent Document 1 relating to the application of the present applicant, the hydraulic fluid pressure of the master cylinder is supplied to the wheel cylinder of the braking force generator provided corresponding to each wheel. A vehicle braking control device that performs front / rear wheel braking force distribution control that suppresses an increase in the braking force of the rear wheels when a vehicle driving state reaches a predetermined state. There is described a braking control device configured to increase the braking force of the front wheels in accordance with the amount of suppression of the increase in braking force of the rear wheels.
Japanese Patent Application No. 2001-360510 Specification and Drawing

  According to the braking control device of the previous application, when the front and rear wheel braking force distribution control is performed, the braking force of the front wheel is increased according to the amount of increase in the braking force of the rear wheel. The power distribution control is performed and the increase in the braking force of the rear wheel is suppressed, so that the shortage of the braking force of the rear wheel can be reliably compensated by the increase of the braking force of the front wheel. The braking force of the entire vehicle is effectively changed to the braking force corresponding to the amount of braking operation by the driver while reliably preventing the vehicle from being locked in advance and deteriorating the stability of the vehicle due to this. Can be controlled.

However, each wheel has a pressure increasing / decreasing control valve for controlling the braking pressure (wheel cylinder pressure), and upstream of the pressure increasing / decreasing control valve corresponding to the left front wheel and upstream of the pressure increasing / decreasing control valve corresponding to the right rear wheel. A control valve for controlling the pressure in the brake hydraulic control conduit communicating with the side, and an upstream side of the pressure increasing / reducing control valve corresponding to the right front wheel and a upstream side of the pressure increasing / reducing control valve corresponding to the left rear wheel And a braking device having a control valve for controlling the pressure in the brake hydraulic pressure control conduit, and the front-rear wheel braking force distribution that lowers the braking pressure of the rear wheels below the braking pressure of the front wheels when the driving state of the vehicle reaches a predetermined state When the amount of braking operation by the driver is increased after starting the front and rear wheel braking force distribution control, the pressure in the brake hydraulic control conduit is increased by the control valve, and the front wheel is controlled according to the amount of increase in the braking operation amount. Braking to increase braking pressure When anti-skid control is performed on the front wheels in the situation where the front and rear wheel braking force distribution control is performed with the increase control, the hydraulic pressure in the brake hydraulic control conduit temporarily rises temporarily according to the anti-skid control of the front wheels However, since the rear wheel braking pressure rises rapidly, the rear wheel slips near the slip limit in the situation where the front and rear wheel braking force distribution control is performed. There is a problem that tends to become unstable.

The present invention provides an increase / decrease control valve provided for each wheel for controlling the braking pressure of the corresponding wheel, and the increase / decrease control valve corresponding to the upstream side of the increase / decrease control valve corresponding to the left front wheel and the right rear wheel. A control valve for controlling the pressure in the brake hydraulic control conduit communicating with the upstream side of the upstream side, an upstream side of the pressure increasing / reducing control valve corresponding to the right front wheel, and an upstream side of the pressure increasing / reducing control valve corresponding to the left rear wheel; And a braking device having a control valve for controlling the pressure in the brake hydraulic pressure control conduit communicating with the vehicle, and when the driving state of the vehicle reaches a predetermined state, an increase in the braking force of the rear wheels is suppressed and The front and rear wheel braking force distribution control is performed to increase the braking force of the front wheels in accordance with the increase suppression amount of the braking force of the wheels, and when the braking operation amount by the driver is increased after the start of the front and rear wheel braking force distribution control, the control valve Increases the pressure in the brake hydraulic control conduit In the braking control device configured to perform the braking force increase control for increasing the braking pressure of the front wheels according to the increase amount of the braking operation amount, the braking by the driver during the execution of the front and rear wheel braking force distribution control is performed. The present invention has been made in view of the above-mentioned problem when the anti-skid control is performed on the front wheel when the braking pressure of the front wheel is increased in accordance with the increase amount of the operation amount. In a vehicle equipped with a braking device and a braking control device, the running stability of the vehicle is improved when anti-skid control is performed in a situation where front and rear wheel braking force distribution control is performed.

According to the present invention, the main problems described above are the pressure increasing / decreasing control valve provided for each wheel and controlling the braking pressure of the corresponding wheel, and the upstream side and the right rear side of the pressure increasing / decreasing control valve corresponding to the left front wheel. A control valve for controlling the pressure in the brake hydraulic control conduit communicating with the upstream side of the pressure increasing / reducing control valve corresponding to the wheel, and the upstream side of the pressure increasing / reducing control valve corresponding to the right front wheel and the left rear wheel A braking control device for a vehicle comprising a braking device having a control valve for controlling a pressure in a brake hydraulic control conduit communicating with an upstream side of the pressure increasing / decreasing control valve, wherein the vehicle operating state is brought into a predetermined state. In this case, front and rear wheel braking force distribution control is performed so that the braking pressure of the rear wheels is lower than the braking pressure of the front wheels. When the amount of braking operation by the driver is increased after the start of the front and rear wheel braking force distribution control, the control valve Increase the pressure in the hydraulic control conduit Brake force increase control is performed to increase the braking pressure of the front wheels according to the increase amount of the braking operation amount, and braking of the front wheels is performed according to the increase amount of the brake operation amount by the driver during the execution of the front and rear wheel braking force distribution control. is achieved by a vehicle braking control device, characterized by decreasing the pressure of the control valve by Ri said brake hydraulic pressure control conduit on when the front wheel antiskid control is performed for when to increase the pressure.

According to the above configuration, the increase / decrease control valve provided for each wheel to control the braking pressure of the corresponding wheel, and the increase / decrease corresponding to the upstream side of the increase / decrease control valve corresponding to the left front wheel and the right rear wheel. A control valve that controls the pressure in the brake hydraulic control conduit that communicates with the upstream side of the pressure control valve, and the pressure increase / reduction control valve that corresponds to the upstream side of the pressure increase / reduction control valve corresponding to the right front wheel and the pressure increase / reduction control valve corresponding to the left rear wheel. A braking control device for a vehicle having a braking device having a control valve for controlling a pressure in a brake hydraulic pressure control conduit communicating with an upstream side, wherein the braking pressure of a rear wheel is set when a driving state of the vehicle becomes a predetermined state. When the braking operation amount by the driver is increased after the start of the front and rear wheel braking force distribution control, the control valve controls the pressure in the brake hydraulic control conduit. Increasing the braking operation amount The braking force increase control is performed to increase the braking pressure of the front wheels according to the increase amount, and the braking pressure of the front wheels is increased according to the increase amount of the braking operation amount by the driver during the execution of the front and rear wheel braking force distribution control. because when the anti-skid control is performed for the front wheels is gradually reduced pressure in by Ri the brake pressure control line to the control valve, increase the amount of the amount of braking operation performed by the front and rear wheel braking force distribution control is performed and the driver when Accordingly, when assist braking that increases the braking pressure of the front wheels is being performed, even if anti-skid control is performed on the front wheels, the hydraulic pressure in the brake hydraulic control conduit temporarily increases rapidly according to the anti-skid control of the front wheels. Therefore, even if the rear wheel braking pressure distribution control is avoided and the rear wheel is close to the slip limit, the rear wheel slips. Possibility that the running of the vehicle becomes unstable will not.

  Hereinafter, preferred embodiments of the present invention (hereinafter simply referred to as embodiments) will be described in detail with reference to the accompanying 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, 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.

  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.

  One end of a first brake hydraulic control conduit 18A is connected to the first master cylinder chamber 14A, and the brake hydraulic control conduit 20FL for the left front wheel and the brake hydraulic pressure for the right rear wheel are connected to the other end of the brake hydraulic control conduit 18A. One end of the control conduit 20RR is connected. A first communication control valve 22A is provided in the middle of the brake hydraulic pressure control conduit 18A, and the communication control valve 22A is a normally open linear solenoid valve in the illustrated embodiment. Connected to the brake hydraulic control conduits 18A on both sides of the communication control valve 22A are check bypass conduits 24A 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 20RR. Yes.

  As shown schematically in FIG. 2, the communication control valve 22A 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 18AA of the brake hydraulic control conduit 18A on the master cylinder 14 side is always connected to the valve chamber 70 via an internal passage 76, and a portion 18AB of the brake hydraulic control conduit 18A opposite to the master cylinder 14 is internally connected. A communication connection is established via a passage 78 and a port 80.

  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.

  In the situation where the communication control valve 22A is in the closed position, the sum of the force caused by the pressure in the portion 18AB on the opposite side of the master cylinder 14 of the brake hydraulic control conduit 18A and the spring force of the compression coil spring 84 is the solenoid. When the electromagnetic force is increased by the valve 82, the valve element 74 opens away from the port 80, and the oil in the portion 18AB passes through the internal passage 78, the port 80, the valve chamber 70, the internal passage 76, and the brake hydraulic control conduit 18A. To the portion 18AA. When the oil pressure in the portion 18AB 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.

  Thus, since the communication control valve 22A controls the pressure in the portion 18AB of the brake hydraulic control conduit 18A according to the voltage applied to the solenoid 82, the communication control valve 22A controls the pressure in the portion 18AB by controlling the driving voltage for the solenoid 82. The pressure (referred to herein as “upstream pressure”) can be controlled to a desired pressure.

  In the illustrated embodiment, the check bypass conduit 24A shown in FIG. 1 is built in the communication control valve 22A, 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 18AB.

  A braking force generator not shown in FIG. 1 generates braking forces for the left front wheel and the right rear wheel at the other ends of the brake hydraulic control conduit 20FL for the left front wheel and the brake hydraulic control conduit 20RR for the right rear wheel, respectively. Wheel cylinders 26FL and 26RR are connected, and normally open electromagnetic on-off valves 28FL and 28RR are provided in the middle of the brake hydraulic control conduit 20FL for the left front wheel and the brake hydraulic control conduit 20RR for the right rear wheel, respectively. ing. Connected to the brake hydraulic control conduits 20FL and 20RR on both sides of the electromagnetic on-off valves 28FL and 28RR are check bypass conduits 30FL and 30RR that permit only the flow of oil from the wheel cylinders 26FL and 26RR toward the brake hydraulic control conduit 18A, respectively. .

  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 20RR between the electromagnetic on-off valve 28RR and the wheel cylinder 26RR. One end of the conduit 32RR is connected. Normally closed solenoid valves 34FL and 34RR are provided in the middle of the oil discharge conduits 32FL and 32RR, respectively, and the other ends of the oil discharge conduits 32FL and 32RR are connected to a buffer reservoir 38A for the front wheel by a connection conduit 36A. ing.

  As understood from the above description, the electromagnetic on-off valves 28FL and 28RR are pressure-increasing valves for increasing or maintaining the pressure in the wheel cylinders 26FL and 26RR, respectively. The electromagnetic on-off valves 34FL and 34RR are in the wheel cylinders 26FL and 26RR, 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 on-off valves 28RR and 34RR cooperate with each other to define an increase / decrease valve for increasing and decreasing the pressure in the wheel cylinder 26RR of the right rear wheel.

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

  One end of a connection conduit 54A is connected to the connection conduit 40A between the two check valves 44A and 46A, and the other end of the connection conduit 54A is a brake between the first master cylinder chamber 14A and the control valve 22A. It is connected to the hydraulic control conduit 18A. A normally closed electromagnetic on-off valve 60A is provided in the middle of the connecting conduit 54A. The electromagnetic on-off valve 60A functions as a suction control valve that controls communication between the brake hydraulic pressure control conduit 18A between the master cylinder 14 and the control valve 22A and the suction side of the pump 42A.

  Similarly, one end of a second brake hydraulic control conduit 18B is connected to the second master cylinder chamber 14B, and the brake hydraulic control conduit 20RL for the left rear wheel and the right front wheel are connected to the other end of the brake hydraulic control conduit 18B. One end of the brake hydraulic pressure control conduit 20FR is connected. A rear wheel communication control valve 22B, which is a normally open linear solenoid valve, is provided in the middle of the brake hydraulic control conduit 18B.

  The communication control valve 22B has the same structure as that shown in FIG. 2 for the first communication control valve 22A. Therefore, the communication control valve 22B controls the drive voltage for the solenoid not shown in the figure, thereby controlling the communication. The pressure (upstream pressure) in the brake hydraulic pressure control conduit 18B downstream of the valve 22B can be controlled to a desired pressure. Further, a check bypass conduit 24B that allows only the flow of oil from the second master cylinder chamber 14B toward the brake hydraulic control conduit 20RL or the brake hydraulic control conduit 20FR is connected to the brake hydraulic control conduit 18B on both sides of the communication control valve 22B. ing.

  A brake force generation 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 20FR for the right front wheel, respectively. The wheel cylinders 26RL and 26FR of the apparatus are connected, and normally open type electromagnetic on-off valves 28RL and 28FR are provided in the middle of the brake hydraulic control conduit 20RL for the left rear wheel and the brake hydraulic control conduit 20FR for the right front wheel, respectively. It has been. Connected to the brake hydraulic control conduits 20RL and 20FR on both sides of the electromagnetic on-off valves 28RL and 28FR are check bypass conduits 30RL and 30FR that permit only the flow of oil from the wheel cylinders 26RL and 26FR toward the brake hydraulic control conduit 18B, respectively. .

  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 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 34RL and 34FR are provided in the middle of the oil discharge conduits 32RL and 32FR, respectively, and the other ends of the oil discharge conduits 32RL and 32FR are connected to the buffer reservoir 38B for the rear wheel through the connection conduit 36B. Has been.

  As in the case of the first side, the electromagnetic on-off valves 28RL and 28FR are pressure-increasing valves for increasing or maintaining the pressure in the wheel cylinders 26RL and 26FR, respectively. The electromagnetic on-off valves 34RL and 34FR are respectively the wheel cylinder 26RL and 26FR is a pressure reducing valve for reducing the pressure in the 26FR. Therefore, the electromagnetic opening / closing valves 28RL and 34RL cooperate with each other to define an pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26RL of the left rear wheel. The electromagnetic open / close valves 28RR and 34FR cooperate with each other to define a pressure increasing / decreasing valve for increasing and decreasing the pressure in the wheel cylinder 26FR of the right front wheel.

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

  One end of a connection conduit 54B is connected to the connection conduit 40B between the two check valves 44B and 46B, and the other end of the connection conduit 54B is a brake between the second master cylinder chamber 14B and the control valve 22B. It is connected to the hydraulic control conduit 18B. A normally closed electromagnetic on-off valve 60B is provided in the middle of the connecting conduit 54B. The electromagnetic opening / closing valve 60B also functions as a suction control valve that controls communication between the brake hydraulic pressure control conduit 18B between the master cylinder 14 and the control valve 22B and the suction side of the pump 42B.

  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, thereby causing the wheel cylinders 26FL and 26RR to move. Is supplied with the pressure in the first master cylinder chamber 14A, and the wheel cylinders 26RL and 26FR are supplied with the pressure in the second master cylinder chamber 14B. 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.

  On the other hand, the communication control valves 22A and 22B are switched to the closed position, the on-off valves 60A and 60B are opened, and the pumps 42A and 42B are operated with the on-off valves of the wheels at the positions shown in FIG. When driven, the oil in the master cylinder 14 is pumped up by the pump, the pressures pumped up by the pump 42A are supplied to the wheel cylinders 26FL, 26RR, and the wheel cylinders 26RL, 26FR are pumped up by the pump 42B. Since the pressure is supplied, the braking pressure of each wheel is increased or decreased by opening / closing the communication control valves 22A and 22B 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 such that the on-off valves 28FL to 28RR are in the open position when not energized as shown in FIG. 1, and the on-off valves 34FL to 34RR are in the closed position when not energized as shown in FIG. In some cases, the pressure is increased (pressure increase mode), and the on-off valves 28FL to 28RR are switched to the closed position when energized, and are held when the on-off valves 34FL to 34RR are in the closed position when not energized as shown in FIG. Holding mode), when the on-off valves 28FL to 28RR are in the closed position when energized and the on-off valves 34FL to 34RR are switched to the open position by energization, the pressure is reduced (decompression mode).

  The communication control valves 22A and 22B, the open / close valves 28FL to 28RR, the open / close valves 34FL to 34RR, and the open / close valves 60A and 60B 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.

  The microcomputer 92 detects 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, a signal indicating the longitudinal acceleration Gx of the vehicle from the longitudinal acceleration sensor 100, and wheel speed sensors 102FL to 102RR. Further, signals indicating wheel speeds Vwi (i = fl, fr, rl, rr) of the left and right front wheels and the left and right rear wheels are input. 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 22A and the like, the braking pressure Pi (i = fl, fr, rl, rr) of each wheel is controlled to the corresponding target braking pressure Pti.

  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 22A and the like are maintained at the illustrated standard position and the pumps 42A and 42B are driven. Accordingly, the braking pressure of each wheel, that is, the pressure in the wheel cylinders 26FL to 26RR is controlled by the master cylinder pressure Pm.

  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 22A and 22B are first closed, then the intake control valves 60A and 60B are opened, and then the pump The driving of 42A and 42B 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 22A and the like are controlled so that the upstream pressure on the front wheel side is controlled to the target braking pressure of Pm + ΔPf. The left and right rear wheel on / off valves 28RL and 28RR are closed so that the braking pressure of the left and right rear wheels becomes the holding pressure Pc.

  The microcomputer 92 is not shown as a flow chart, but based on the wheel speed Vwi of each wheel, the vehicle speed Vb and the braking slip amount SBi (i = fl, fr, rl, rr), and when the braking slip amount SBi of any wheel becomes larger than the reference value for starting anti-skid control (ABS control) and the anti-skid control start condition is satisfied, Until the end condition is satisfied, anti-skid control is performed in which the pressure in the wheel cylinder is increased or decreased so that the braking slip amount of the wheel falls within a predetermined range over the braking force front-rear distribution control.

  Further, when the anti-skid control is started for any of the wheels during the front-rear distribution control of the braking force according to the braking control flow described later, the microcomputer 92 gradually decreases the front wheel increase pressure ΔPf and maintains the rear wheel braking pressure. The pressure Pc is gradually increased, thereby preventing the braking force of the entire vehicle from becoming excessive and improving the running stability of the vehicle.

  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.

  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.

  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 for the front and rear wheels is being performed. If the determination is affirmative, the process proceeds to step 90. If the determination is negative, the process proceeds to step 30.

  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.

  In step 60, it is determined whether or not the master cylinder pressure Pm exceeds the rear wheel holding pressure Pc, that is, whether or not it is necessary to maintain the rear wheel braking pressure and increase the front wheel braking pressure. If a negative determination is made, the process proceeds to step 70. If an affirmative determination is made, the process proceeds to step 150.

  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. The control by the routine shown in FIG. 3 is once terminated, and when an affirmative determination is made, in step 80, the rear wheel holding pressure Pc is set to the master cylinder pressure Pm at that time, and then the routine proceeds to step 150. .

  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 exceeds the control start reference value Gxs (positive constant). Or may be performed by a combination of the above (A) and (B). Further, it is simultaneously determined whether or not the control start conditions of the above steps 60 and 70 are satisfied. When the affirmative determination is made for the first time, the process proceeds to step 80, and when the affirmative determination is made for the second time or later, the process proceeds to step 150. If a negative determination is made in advance, the control by the routine shown in FIG. 3 may be corrected to end.

  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. If a negative determination is made, the process proceeds to step 100. If an affirmative determination is made, the gradual decrease amount ΔPf of the front wheel braking pressure increase ΔPf is determined to be ΔP1 (positive) in step 110. Constant), and the process proceeds to step 130.

  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 the control end reference value Gxe (a positive constant smaller than Gxs). Furthermore, it may be determined that the control end condition is satisfied when both conditions are satisfied.

  In step 100, it is determined whether or not anti-skid control is being performed for any of the wheels. If a negative determination is made, the process proceeds to step 150. If an affirmative determination is made, the process proceeds to step 120. Then, the gradual decrease amount ΔP of the increase pressure ΔPf of the braking pressure of the front wheels is set to ΔP2 (a positive constant smaller than ΔP1), and then the routine proceeds to step 130.

  In step 130, the previous value of the front wheel braking pressure increase pressure ΔPf is set to ΔPff, and the front wheel braking pressure increase pressure ΔPf is set to ΔPff−ΔP. In step 140, the increase pressure ΔPf is 0 or less. If a negative determination is made, the process proceeds to step 170. If an affirmative determination is made, the control by the routine shown in FIG.

In step 150, 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 coefficient Kb is calculated according to the following equation 1 with the wheel braking effectiveness coefficients being BEFf and BEFr (positive constants), respectively, and the basic increase pressure ΔPfo of the front wheel braking pressure is calculated according to the following equation 2. 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.
Kb = (Sr × Rr × BEFr) / (Sf × Rf × BEFf) (1)
ΔPfo = (Pm−Pc) Kb (2)

In step 160, 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 3. A map corresponding to the graph shown in FIG. 6 is also obtained in advance experimentally, for example.
ΔPf = ΔPfo (1 + ΔBEF / BEFo) (3)

  In step 170, 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 device 10 is controlled.

  In step 180, it is determined whether or not anti-skid control is being performed for any of the wheels. When a negative determination is made, in step 190, the target braking pressures Ptrl and Ptrr for the left and right rear wheels are determined. Is set to the holding pressure Pc, and 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, respectively. The target braking pressures Ptrl and Ptrr for the left and right rear wheels are set to the holding pressure Pc + ΔPcabs, with the amount of increase in the braking pressure for the rear wheels as ΔPcabs (positive constant), and the braking pressures for the left and right rear wheels are set to the target braking pressure Ptrl. And the braking device 10 is controlled to become Ptrr.

  Although not shown in FIG. 3, if a negative determination is made in step 70 and an affirmative determination is made in step 140, 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.

  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, a correction pressure ΔPc for the basic holding pressure Pcs is calculated based on the vehicle deceleration Gxb, and 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.

  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.

  On the other hand, when the amount of braking operation by the driver is further increased and the master cylinder pressure Pm exceeds the rear wheel holding pressure Pc, an affirmative determination is made in step 60, and the master cylinder pressure Pm is Even if the holding pressure Pc is not exceeded, if another start condition of the braking force distribution control for the front and rear wheels is satisfied, an affirmative determination is made at step 70, and the holding pressure Pc for the rear wheel is determined at step 80. Is set to the master cylinder pressure Pm at that time, and in step 150, the basic increase pressure ΔPfo of the braking pressure of the front wheels is calculated according to the above equation 2 based on the deviation Pm−Pc between the master cylinder pressure Pm and the rear wheel holding pressure Pc. In step 160, the braking effectiveness coefficient BEFv corresponding to the current vehicle speed is calculated based on the vehicle speed V, and the standard braking effectiveness coefficient BEFo and the current braking effectiveness relationship are calculated. A deviation ΔBEF from the number BEFv is calculated, and an increase pressure ΔPf of the braking pressure of the front wheels is calculated according to the above equation 3.

  Further, in step 170, 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 increase pressure ΔPf. The braking device 10 is controlled such that the braking pressure of the wheels becomes the target braking pressures Ptrl and Ptrr = holding pressure Pc of the left and right rear wheels.

  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.

  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.

  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.

  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.

  Further, according to the illustrated embodiment, when anti-skid control is started during front and rear wheel braking force distribution control, affirmative determination, negative determination, and positive determination are performed in steps 20, 90, and 100, respectively. And 130, the increase amount ΔPf of the braking pressure of the front wheels is gradually decreased by ΔP2 for each cycle, so that the pressure in the brake hydraulic control conduits 20FL and 20RR is gradually decreased by the communication control valve 22A and the communication control valve 22B. Since the pressure in the brake hydraulic control conduits 20FR and 20RL is gradually reduced, the braking pressure of the rear wheels suddenly increases after the start of the anti-skid control, the vehicle becomes unstable, and the brake hydraulic control conduits 20FL, 20RR, 20FR And the front wheel electromagnetic on / off valves 28FL and 34FL are controlled in a situation where the pressure in the 20RL is high, so that the front wheel Dynamic pressure can be reliably prevented from or is boosted to excessive, thereby improving the running stability of the vehicle.

  Further, according to the illustrated embodiment, when the termination condition for the front and rear wheel braking force distribution control is satisfied, an affirmative determination is made in step 90, and in step 110, the amount of increase ΔPf in the front wheel braking pressure is increased every cycle. Is gradually reduced at a faster gradual decrease speed than when anti-skid control is started, so that the gradual decrease speed of the amount of increase in the braking pressure of the front wheels during the anti-skid control is excessive. The front-wheel braking pressure can be quickly reduced at the end of the front-rear wheel braking force distribution control.

  Further, according to the embodiment shown in the figure, in both cases when the anti-skid control is started during the front and rear wheel braking force distribution control and when the termination condition of the front and rear wheel braking force distribution control is satisfied, Until the affirmative determination is made, in other words, until the increase amount ΔPf of the braking pressure of the front wheels becomes zero, the increase amount of the braking pressure of the front wheels can be gradually decreased until it becomes surely zero.

  Further, according to the illustrated embodiment, when the anti-skid control is finished during the front and rear wheel braking force distribution control, a negative determination is made in steps 90 and 100, and the gradual decrease in the increase amount of the braking pressure of the front wheels is stopped. Since step 150 and subsequent steps are executed, it is possible to reliably prevent the gradual decrease in the amount of increase in the braking pressure of the front wheels from being unnecessarily continued despite the end of the anti-skid control.

  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.

  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.

  According to the illustrated embodiment, the holding pressure Pc is not set to a constant value. In steps 30 to 50, the vehicle speed V decreases so that the vehicle speed V decreases as the vehicle speed V increases and the vehicle deceleration Gxb increases. Since the rear wheel holding pressure Pc is variably set according to the vehicle deceleration Gxb, the rear wheel holding pressure Pc should be set appropriately as compared with the case where the vehicle speed V and the vehicle deceleration Gxb are not taken into consideration. Thus, the front and rear wheel braking force distribution control can be appropriately executed in accordance with the situation of the vehicle.

  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.

  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.

  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.

  In the embodiment described above, the rear wheel holding pressure Pc is variably set in steps 30 and 40 in accordance with the vehicle speed V and the vehicle deceleration Gxb. The pressure Pc may be modified to be variably set only in accordance with one of the vehicle speed V and the vehicle deceleration Gxb, and the rear wheel holding pressure Pc is variably set in accordance with the vehicle speed V and the vehicle deceleration Gxb. It may be set to a constant value without being performed.

  In the above-described embodiment, the rear wheel holding pressure Pc is calculated in steps 150 and 160 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.

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. 4 is a flowchart showing a braking force distribution control routine for front and rear wheels in the illustrated embodiment. It is a graph which shows the relationship between the vehicle speed V and the basic holding pressure Pcs of a rear wheel. It is a graph which shows the relationship between the deceleration Gxb of a vehicle, and correction | amendment pressure (DELTA) Pc with respect to the basic holding pressure Pcs. It is a graph which shows the relationship between the vehicle speed V and the brake effectiveness coefficient BEF. It is a graph which shows the relationship between the ideal front-rear distribution line and the braking pressure Pf of the front wheel and the braking pressure Pr of the rear wheel in the illustrated embodiment. 4 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Braking 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 chamber 74 ... Valve element 84 ... Compression coil spring 88 ... Check valve 90 ... Electronic control device 96 ... Pressure sensor 98 ... Vehicle speed sensor 100 ... Longitudinal acceleration sensor 102FL-102RR ... Wheel speed sensor

Claims (1)

An increase / decrease control valve provided for each wheel to control the braking pressure of the corresponding wheel; an upstream side of the increase / decrease control valve corresponding to the left front wheel; and an upstream side of the increase / decrease control valve corresponding to the right rear wheel; A brake that communicates the control valve that controls the pressure in the brake hydraulic control conduit that communicates with the upstream side of the pressure increasing / reducing control valve that corresponds to the right front wheel and the upstream side of the pressure increasing / reducing control valve that corresponds to the left rear wheel A vehicle braking control device comprising a braking device having a control valve for controlling a pressure in a hydraulic control conduit,
When the driving state of the vehicle reaches a predetermined state, front / rear wheel braking force distribution control is performed so that the braking pressure of the rear wheels is lower than the braking pressure of the front wheels,
When the amount of braking operation by the driver is increased after the front and rear wheel braking force distribution control is started, the pressure in the brake hydraulic control conduit is increased by the control valve, and braking of the front wheels is performed according to the amount of increase in the braking operation amount. Perform braking force increase control to increase pressure,
The brake Ri by said control valve when the front wheel antiskid control is performed for the time that increases the braking pressure of the front wheels in accordance with the increase amount of braking operation amount by the driver during execution of the front and rear wheel braking force distribution control A braking control device for a vehicle, wherein the pressure in the hydraulic control conduit is gradually reduced.

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