JP5567791B2 - Vehicle braking force control device - Google Patents

Description

  The present invention relates to a vehicle braking force control device, and more particularly to a vehicle braking force control device capable of generating a braking force for maintaining the vehicle in a stopped state.

  As one of braking force control devices for vehicles such as automobiles, when a predetermined operating condition is established, a braking force control device for a vehicle that performs braking force holding control for holding the braking state of the vehicle is already known. Patent Document 1 of Japanese Patent Application Laid-Open No. H11-228707. According to this type of braking force control device, the driver can maintain the vehicle in a stopped state without continuing the braking operation.

JP 2007-276625 A JP-A-10-264801

[Problems to be Solved by the Invention]
In the conventional braking force control device as described in each of the above publications, for example, when it is determined that the vehicle substantially stops on a slope and a predetermined operating condition is satisfied, the brake actuator is operated. The braking force applied to the wheels generates a braking force sufficient to maintain the vehicle in a stopped state.

  In addition, as a means to apply and maintain braking force for maintaining the vehicle in a stopped state, the communication between the master cylinder and the wheel cylinder is interrupted when the vehicle is stopped by a braking operation performed by the driver. Thus, it is conceivable to maintain the braking force of the wheel by maintaining the pressure in the wheel cylinder.

  However, in general, the driver reduces the amount of braking operation when the vehicle speed approaches 0 in order to avoid a shock at the time of braking stop of the vehicle. Therefore, the amount of braking operation of the driver when a predetermined operating condition is satisfied is It ’s low. Therefore, in such a situation, a sufficient braking force cannot be ensured even if the communication between the master cylinder and the wheel cylinder is interrupted. Therefore, the hydraulic oil must be pressurized by the pump, and the durability of the pump may be deteriorated due to the high frequency of pump operation.

  In order to ensure a sufficient braking force in the braking force holding control, for example, in Patent Document 2 described above, when the amount of braking operation of the driver is increased in a situation where the vehicle speed is below the reference value. A braking force control device that performs braking force holding control is described. According to this type of braking force control device, it is possible to avoid an increase in the operation frequency of the pump due to the braking force holding control. However, if the amount of braking operation by the driver is not increased in a situation where the vehicle speed is below the reference value, the braking force holding control cannot be performed.

The present invention has been made in view of the above-described problems in the conventional braking force control device that performs the braking force holding control for holding the braking state of the vehicle. The main problem of the present invention is that the working fluid is It is an object of the present invention to provide a braking force control device capable of performing a braking force holding control with a sufficient braking force without causing an increase in the frequency of pressurization.
[Means for Solving the Problems and Effects of the Invention]

Major problems described above, according to the present invention, a vehicle work dynamic fluid performs suppress braking force holding control a decrease in pressure in the wheel cylinder by restricting the flowing from the wheel cylinder to the master cylinder In the braking force control device, when it is determined that the driver is about to stop the vehicle by performing a braking operation, it is determined whether to start the braking force holding control based on the amount of braking operation performed by the driver. In addition, when the vehicle does not stop even when a time longer than a reference time has elapsed from the time when the braking force holding control is started, the braking force holding device is terminated. suppressing braking the lowering of pressure in the wheel cylinder by the configuration of claim 1), or the working fluid is restricted from flowing from the wheel cylinder to the master cylinder In a braking force control device for a vehicle that performs holding control, a braking force generated by a driver's braking operation when the vehicle stops to maintain the vehicle in a stopped state even when the creep force should be suppressed. Is estimated by the vehicle braking force control device (configuration of claim 2 ), which performs the braking force holding control without suppressing the creep force.

According to this configuration 1, whether OPERATION person when it is determined that an attempt to stop the vehicle by performing a braking operation starts braking force holding control on the basis of the amount of braking operation of the driver If the vehicle does not stop even if a time longer than the reference time has elapsed from the time when the braking force holding control is started, the braking force holding control is ended. Accordingly, when the vehicle does not stop even after a time longer than the reference time has elapsed since the start of the braking force holding control, the braking force holding control is terminated. For example, the driver may travel downhill while performing a braking operation. In such a situation, it is avoided that the braking force holding control is continued unnecessarily and that the driving force is continuously applied to the vehicle for an unnecessarily long time due to this. be able to.

According to the second aspect of the present invention, even when the creep force is to be suppressed, the reference value for maintaining the vehicle in the stopped state by the braking force generated by the driver's braking operation when the vehicle stops. When it is estimated that the braking force is exceeded, the braking force holding control is performed without suppressing the creep force. Accordingly, the creep force is not suppressed in a situation where the pressure in the wheel cylinder when the vehicle stops becomes a pressure that generates a braking force that can maintain the vehicle in a stopped state. Therefore, the amount of braking operation is reduced by the driver in response to the suppression of the creep force, and as a result, the braking force of the vehicle becomes less than the braking force that can maintain the vehicle in a stopped state, If the working fluid is not pressurized, the possibility that the vehicle cannot be maintained in a stopped state can be reduced.

According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 2 , the braking force control device is controlled by a driver's braking operation when the vehicle stops. When the power is estimated to be equal to or greater than a reference value for maintaining the vehicle in a stopped state, but the braking force by the driver's braking operation when the vehicle stops is less than the reference value, the pressure in the wheel cylinder By increasing the pressure of the vehicle, the braking force of the vehicle is increased to the reference value or more to perform the braking force holding control, and thereafter the creep force is suppressed (configuration of claim 3 ).

According to the third aspect of the present invention, when the braking force of the vehicle when the vehicle is stopped is less than the reference value for maintaining the vehicle in the stopped state, the pressure in the wheel cylinder is increased to increase the pressure of the vehicle. The braking force holding control is performed by increasing the braking force by a reference value or more, and then the creep force is suppressed. Therefore, the braking force holding control is performed in a situation where the braking force of the vehicle when the vehicle stops is less than the reference value for maintaining the vehicle in the stopped state, and the vehicle cannot be maintained in the stopped state. be able to. Further, the suppression of the creep force is prevented from being performed before the braking force holding control, and the braking operation amount is reduced by the driver in response to the suppression of the creep force and the pressure in the wheel cylinder is prevented from being lowered. Therefore, the required pressure increase amount in the wheel cylinder can be reduced.
[Preferred embodiment of problem solving means]

According to another preferred aspect of the present invention, in the configuration of claim 2 or 3 , the braking force control device estimates the amount of decrease in the braking force of the vehicle until the vehicle stops, and the driver The braking of the driver when the vehicle stops when the braking force of the vehicle based on the braking operation amount of the vehicle is equal to or greater than the sum of the reference value for maintaining the vehicle in a stopped state and the amount of decrease in the braking force of the vehicle It is configured to estimate that the braking force due to the operation is equal to or greater than a reference value for maintaining the vehicle in a stopped state (preferred aspect 1 ).

According to another preferred aspect of the present invention, in the configuration of the preferred aspect 1 described above, the braking force control device is configured to wait until the vehicle stops based on a change in the braking operation amount of the driver and a change in the vehicle speed. It is comprised so that the fall amount of the braking force of a vehicle may be estimated (Preferred aspect 2 ).

According to another preferred aspect of the present invention, in the configuration of claim 2 , the braking force control device maintains the vehicle in a stopped state by the braking force generated by the driver's braking operation when the vehicle stops. When it is estimated that the braking force will not exceed the reference value, the creep force is suppressed and the pressure in the wheel cylinder is increased so that the braking force of the vehicle is increased to a reference value or more and braking force holding control is performed. It is comprised so that it may perform (Preferable aspect 3 ).

According to another preferred aspect of the present invention, in the configuration of claim 2 or 3 , the braking force control device is a reference value for maintaining the vehicle in a stopped state based on at least the creep force of the vehicle. (Preferred aspect 4 ).

According to another preferred aspect of the present invention, in the configuration of the preferred aspect 4 described above, the braking force control device maintains the vehicle in a stopped state based on the creep force of the vehicle and the longitudinal force due to the forward and backward inclination of the road surface. It is comprised so that the reference value for doing may be calculated (Preferred aspect 5 ).

According to another preferred aspect of the present invention, in the configuration according to any one of the first to third aspects, the braking force control device controls the pressure in the wheel cylinder by the differential pressure control valve. By maintaining the pressure higher than the pressure, the working fluid is configured to be restricted from flowing from the wheel cylinder to the master cylinder (preferred aspect 6 ).

According to another preferred aspect of the present invention, in the configuration according to any one of the first to third aspects, the braking force control device blocks communication between the wheel cylinder and the master cylinder by the on-off valve. Thus, it is configured to restrict the working fluid from flowing from the wheel cylinder to the master cylinder (preferred aspect 7 ).

1 is a schematic configuration diagram showing a first embodiment of a braking force control device for a vehicle according to the present invention. It is a flowchart which shows the braking force holding | maintenance control routine in 1st embodiment. It is a flowchart which shows the braking force holding | maintenance control routine in 2nd embodiment. When the braking pressure Pi at which it is determined that the driver intends to stop the vehicle is equal to or higher than the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in a stopped state, the driver's braking operation It is a figure which shows the example of the change of the master cylinder pressure Pm at the time of a vehicle stopping by, the braking pressure Pi of each wheel, and the driving force Fd of a vehicle. When the braking pressure Pi at the time when it is determined that the vehicle is stopped in the conventional braking force holding control is equal to or higher than the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in a stopped state ( It is a figure which shows the example of a change of the master cylinder pressure Pm and the braking pressure Pi of each wheel about the case (B) which is less than A) and the reference | standard braking pressure Pbreq. It is a figure which shows the example of a change of the master cylinder pressure Pm and the braking pressure Pi of each wheel about the case where the starting conditions of creep force fall control are satisfied in the conventional braking force holding control.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[First embodiment]

  FIG. 1 is a schematic configuration diagram showing a hydraulic circuit and an electronic control device of a first embodiment of a braking force control device according to the present invention. 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 system brake hydraulic control conduit 18A and a second system brake hydraulic control conduit 18B are connected to the first master cylinder chamber 14A and the second master cylinder chamber 14B, respectively. The brake hydraulic control conduits 18A and 18B connect the master cylinder chambers 14A and 14B to the brake actuator 20, respectively.

  A communication control valve 22A of the first system is provided in the middle of the brake hydraulic pressure control conduit 18A. The communication control valve 22A is a normally open linear solenoid valve in the illustrated embodiment. The communication control valve 22A opens when a drive current is not supplied to a solenoid not shown in FIG. 1, and closes when a drive current is supplied to the solenoid. In particular, when the communication control valve 22A is in a closed state, the differential pressure is maintained so that the pressure on the side opposite to the master cylinder 14 becomes higher than the pressure on the master cylinder 14 side, and the communication control valve 22A corresponds to the voltage of the drive current. Increase or decrease the differential pressure.

  In other words, when the differential pressure across the communication control valve 22A is equal to or less than the commanded differential pressure determined by the voltage of the drive current for the solenoid, the communication control valve 22A maintains the closed state. Therefore, the communication control valve 22A prevents oil as a working fluid from flowing from the side opposite to the master cylinder 14 to the master cylinder 14 side through the communication control valve 22A, and thereby the differential pressure across the communication control valve 22A. Prevents the decline. On the other hand, when the differential pressure across the communication control valve 22A exceeds the commanded differential pressure determined by the voltage of the drive current with respect to the solenoid, the communication control valve 22A opens. Therefore, the communication control valve 22A allows oil to flow from the side opposite to the master cylinder 14 to the master cylinder 14 side through the communication control valve 22A, thereby indicating the differential pressure across the communication control valve 22A as the indicated differential pressure. To control.

  The other end of the first system brake hydraulic control conduit 18A is connected to one end of a brake hydraulic control conduit 24FR for the right front wheel and one of the brake hydraulic control conduit 24RL for the left rear wheel. Wheel cylinders 26FR and 26RL for controlling the braking force of the right front wheel and the left rear wheel are connected to the other ends of the brake hydraulic control conduit 24FR for the right front wheel and the brake hydraulic control conduit 24RL for the left rear wheel, respectively. . Further, normally open electromagnetic on-off valves 28FR and 28RL are provided in the middle of the brake hydraulic control conduit 24FR for the right front wheel and the brake hydraulic control conduit 24RL for the left rear wheel, respectively.

  One end of an oil discharge conduit 32FR is connected to the brake hydraulic control conduit 24FR between the electromagnetic on-off valve 28FR and the wheel cylinder 26FR, and oil is discharged to the brake hydraulic control conduit 24RL between the electromagnetic on-off valve 28RL and the wheel cylinder 26RL. One end of the conduit 32RL is connected. Normally closed solenoid valves 34FR and 34RL are provided in the middle of the oil discharge conduits 32FR and 32RL, respectively, and the other end of the oil discharge conduits 32FR and 32RL is a first system reservoir for storing oil through the connection conduit 36A. 38A.

  As understood from the above description, the electromagnetic on-off valves 28FR and 28RL are pressure-increasing valves for increasing or maintaining the pressure in the wheel cylinders 26FR and 26RL, respectively, and the electromagnetic on-off valves 34FR and 34RL are in the wheel cylinders 26FR and 26RL, respectively. This is a pressure reducing valve for reducing the pressure of Therefore, the electromagnetic on-off valves 28FR and 34FR cooperate with each other to define a pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26FR of the right front wheel, and the electromagnetic on-off valves 28RL and 34RL cooperate with each other. The pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26RL of the left rear wheel is defined.

  The connecting conduit 36A is connected to the suction side of the pump 42A by a connecting conduit 40A. The discharge side of the pump 42A is connected to the other end of the brake hydraulic pressure control conduit 18A by a connection conduit 46A having a damper 44A on the way. The connection conduit 46A between the pump 42A and the damper 44A is provided with a check valve 48A that allows only the flow of oil from the pump 42A toward the damper 44A.

  Similarly, a second system communication control valve 22B is provided in the middle of the brake hydraulic pressure control pipe 18B. The communication control valve 22B is a normally open linear solenoid valve in the illustrated embodiment, and is connected to the brake hydraulic control conduit 18B. It operates similarly to the control valve 22A. Therefore, by controlling the voltage of the drive current for the solenoid not shown in FIG. 1, the oil is restricted from flowing from the wheel cylinders 26FL and 26RR side to the master cylinder 14 side through the communication control valve 22B. The differential pressure across the communication control valve 22B is controlled to the indicated differential pressure.

  One end of a brake hydraulic control conduit 24FL for the left front wheel and a brake hydraulic control conduit 24RR for the right rear wheel are connected to the other end of the brake hydraulic control conduit 18B of the second system. Wheel cylinders 26FL and 26RR for controlling the braking force of the left front wheel and the right rear wheel are respectively connected to the other ends of the brake hydraulic control conduit 24FL for the left front wheel and the brake hydraulic control conduit 24RR for the right rear wheel. . Further, normally open electromagnetic on-off valves 28FL and 28RR are provided in the middle of the brake hydraulic control conduit 24FL for the left front wheel and the brake hydraulic control conduit 24RR for the right rear wheel, respectively.

  One end of an oil discharge conduit 32FL is connected to the brake hydraulic control conduit 24FL between the electromagnetic on-off valve 28FL and the wheel cylinder 26FL, and oil is discharged to the brake hydraulic control conduit 24RR 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 end of the oil discharge conduits 32FL and 32RR is a second-system reservoir for storing oil through the connection conduit 36B. 38B.

  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. This is a pressure reducing valve for reducing the pressure of Accordingly, the electromagnetic on-off valves 28FL and 34FL cooperate with each other to define a pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26FL of the left front wheel, and the electromagnetic on-off valves 28RR and 34RR cooperate with each other. The pressure increasing / reducing valve for increasing and decreasing the pressure in the wheel cylinder 26RR of the right rear wheel is defined.

  The connecting conduit 36B is connected to the suction side of the pump 42B by a connecting conduit 40B. The discharge side of the pump 42B is connected to the other end of the brake hydraulic control conduit 18B by a connection conduit 46B having a damper 44B in the middle. A connection conduit 46B between the pump 42B and the damper 44B is provided with a check valve 48B that allows only the flow of oil from the pump 42B toward the damper 44B. The pumps 42A and 42B are driven by a common electric motor not shown in FIG.

  The reservoirs 38A and 38B are connected to brake hydraulic pressure control conduits 18A and 18B between the master cylinder 14 and the communication control valves 22A and 22B by connection conduits 50A and 50B, respectively. Accordingly, the reservoirs 38A and 38B allow oil to flow between the master cylinder chambers 14A and 14B and the reservoirs 38A and 38B when the communication control valves 22A and 22B are in the closed state, respectively. A check valve is integrally fixed to the free pistons of the reservoirs 38A and 38B, and the check valve prevents the amount of oil in the reservoirs 38A and 38B from exceeding a reference value.

  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. As a result, the pressure in the first master cylinder chamber 14A is supplied to the wheel cylinders 26FR and 26RL, and the pressure in the second master cylinder chamber 14B is supplied to the wheel cylinders 26FL 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.

  On the other hand, when the communication control valves 22A and 22B are switched to the closed position, and the pumps 42A and 42B are driven in a state where the opening / closing valves of the wheels are at the positions shown in FIG. Oil is pumped up by the pump. Therefore, the pressure pumped up by the pump 42A is supplied to the wheel cylinders 26FR and 26RL, and the pressure pumped up by the pump 42B is supplied to the wheel cylinders 26FL and 26RR. Therefore, 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 increased when the on-off valves 28FR to 28RL and the on-off valves 34FR to 34RL are in the non-control position shown in FIG. 1 (pressure increasing mode), and the on-off valves 28FR to 28RL are closed. When it is switched to the valve position and the on-off valves 34FR to 34RL are in the non-control position shown in FIG. 1, it is held (holding mode), and the on-off valves 28FR to 28RL are switched to the closed position and the on-off valves 34FR to 34RL are When switched to the valve open position, the pressure is reduced (pressure reduction mode).

  The motors that drive the communication control valves 22A and 22B, the on-off valves 28FR to 28RL, the on-off valves 34FR to 34RL, and the pumps 42A and 42B are controlled by the braking force control electronic control device 60 as will be described later. Although not shown in FIG. 1, the electronic control unit 60 includes a microcomputer and a driving circuit, and the microcomputer has a general configuration well known in the art having a CPU, a RAM, and a ROM. It may be a thing.

  The electronic controller 60 receives a signal indicating the master cylinder pressure Pm from the pressure sensor 62, a signal indicating the pressure Pi (i = fr, fl, rr, rl) in the wheel cylinders 26FR to 26RL from the pressure sensor 64i, and a vehicle speed sensor 66. A signal indicating the vehicle speed V is input. The electronic control unit 60 calculates target braking pressures Pti (i = fr, fl, rr, rl) for the left and right front wheels and the left and right rear wheels, and controls the communication control valve 22A and the like, thereby controlling the braking pressure Pi for each wheel. (I = fr, fl, rr, rl) is controlled to the corresponding target braking pressure Pti. The pressure Pi in the wheel cylinders 26FR to 26RL may be estimated from a control command value to the communication control valve 22A or the like, and therefore the pressure sensor 64i may be omitted.

  In particular, when the amount of braking operation by the driver is small and the braking operation speed is low, the brake assist is unnecessary. Therefore, the communication control valve 22A and the like are maintained at the standard positions shown in the figure, and the pumps 42A and 42B are not driven. Braking pressure, that is, the pressure in the wheel cylinders 26FR to 26RL is controlled by the master cylinder pressure Pm.

  On the other hand, when the amount of braking operation by the driver is large or when the braking operation speed is large, brake assist is necessary, so the communication control valves 22A and 22B are closed first, and then the pumps 42A and 42B are started to be driven. The target braking pressure Pti of each wheel is calculated based on the master cylinder pressure Pm, and the communication control valve 22A and the like are controlled based on the target braking pressure Pti, whereby the braking pressure of each wheel is set to the target braking pressure Pti. Be controlled.

  Although not shown in the figure, the electromagnetic on-off valves 28FR to 28RL and the on-off valves 34FR to 34RL are controlled when it is necessary to individually control the braking force of each wheel as in the case of stabilizing the behavior of the vehicle. The Particularly in this case, the higher target braking pressure of the right front wheel and the left rear wheel is set as the target upstream pressure of the communication control valve 22A, and the higher target braking pressure of the left front wheel and the right rear wheel is set as the target upstream pressure of the communication control valve 22B. The braking pressure with the lower target braking pressure of the right front wheel and the left rear wheel and the braking pressure with the lower target braking pressure of the left front wheel and the right rear wheel are respectively set by the corresponding pressure increasing valve and pressure reducing valve. It is controlled to the corresponding target braking pressure.

  In the first embodiment, the electronic control unit 60 stores the braking force holding control flow shown in FIG. 2, and when the driver is about to stop the vehicle, the electronic control unit 60 is shown in FIG. The braking force holding control is performed according to the flowchart. In particular, in the situation where the driver is about to stop the vehicle, the electronic control unit 60 operates when the amount of braking operation by the driver is equal to or greater than the value corresponding to the reference braking force for maintaining the vehicle in the stopped state. The command differential pressures of the flow control valves 22A and 22B are controlled so that the braking operation amount of the person can secure the braking force necessary to maintain the vehicle in the stopped state. Thus, the electronic control unit 60 controls the braking force of the vehicle to the braking force necessary to maintain the vehicle stop state without requiring the pumps 42A and 42B to be driven.

  Further, the electronic control device 60 cancels the excessive braking force generated by closing the through-control valves 22A and 22B by the driving force of the vehicle, whereby the deceleration of the vehicle corresponds to the braking operation amount of the driver. The driving force control electronic control unit 68 is requested to generate a driving force so as to achieve deceleration.

  The driving force control electronic control device 68 controls the output of the engine 70 and the gear ratio of the automatic transmission 72 according to the accelerator opening degree, etc., when the command signal is not received from the braking force control electronic control device 60. Thus, the driving force of the vehicle is controlled according to the driving request of the driver. On the other hand, when the driving force control electronic control unit 68 receives a command signal from the braking force control electronic control unit 60, the driving force (mainly driving force) of the vehicle according to the request of the braking force control electronic control unit 60. To control.

  Next, the braking force holding control routine in the first embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started in a situation where the vehicle is in a traveling state, and is repeatedly executed every predetermined time.

  First, in step 10, it is determined whether or not the driver intends to stop the vehicle, that is, whether or not the driver has an intention to stop the vehicle. The control according to the routine shown in FIG. 2 is once terminated, and when an affirmative determination is made, the routine proceeds to step 20. In this case, when the vehicle speed V is equal to or lower than the reference value V1 (a positive constant close to 0) and the master cylinder pressure Pm is equal to or higher than the reference value Pm1 (a positive constant), the driver intends to stop the vehicle. May be determined.

In step 20, a reference braking force Fbreq for maintaining the vehicle in a stopped state is calculated. In this case, the creep force when the vehicle is stopped is Fcp, the longitudinal force of the vehicle due to the slope of the road is Fsx (the forward direction of the vehicle is positive), and the margin coefficient is Ka (a positive value greater than 1 of about 2). The reference braking force Fbreq may be calculated according to the following equation 1. Further, the longitudinal force Fsx of the vehicle due to the inclination of the road surface may be calculated by Wsin θ, where θ is the inclination angle of the road surface and W is the weight of the vehicle.
Fbreq = Ka (Fcp + Fsx) (1)

  In step 30, it is determined whether or not a differential pressure instruction in step 50 described later has already been made to the communication control valves 22A and 22B. When a negative determination is made, the process proceeds to step 40 to determine whether or not a differential pressure instruction is possible, and when an affirmative determination is made, the process proceeds to step 50.

  In step 40, the coefficient for converting the braking pressure into the braking force is set as Kf, and it is determined whether or not the product KfPm of the coefficient Kf and the master cylinder pressure Pm is equal to or higher than the reference braking force Fbreq, that is, the driver's braking operation It is determined whether or not the current braking force of the vehicle is a braking force that can maintain the vehicle in a stopped state. When a negative determination is made, the process proceeds to step 110, and when an affirmative determination is made, the process proceeds to step 50.

  In step 50, the product KpFbreq of the coefficient Kp (= 1 / Kf) for converting the braking force into the braking pressure and the reference braking force Fbreq is calculated as the reference braking pressure Pbreq corresponding to the reference braking force Fbreq. Further, the reference brake pressure Pbreq is used as an instruction differential pressure with respect to the communication control valves 22A and 22B so that the communication control valves 22A and 22B can maintain the brake pressure Pbreq even when the master cylinder pressure Pm becomes lower than the reference brake pressure Pbreq. The voltage of the control current for the solenoid of the communication control valve is controlled.

  In step 60, for example, whether or not the vehicle has stopped is determined by determining whether or not the vehicle speed V is equal to or less than a reference value V2 (a positive constant smaller than V1), and an affirmative determination is made. If YES, the process proceeds to step 100. If a negative determination is made, the process proceeds to step 70.

In step 70, a driving force Fdreq necessary to cancel the surplus braking force Fbex generated by maintaining the differential pressure by the communication control valves 22A and 22B by the driving force Fd of the vehicle is calculated. In this case, the necessary driving force Fdvreq may be calculated according to the following equation 2, and when the driving force Fdvreq is calculated to a negative value, the driving force Fdvreq is set to zero.
Fdreq = Fbex
= Kf (Pbreq-Pm) (2)

  In step 80, it is determined whether or not an end condition of control for generating the driving force Fdreq necessary for canceling the surplus braking force Fbex with the driving force Fd of the vehicle is satisfied, and an affirmative determination is made. If so, the process proceeds to step 100. If a negative determination is made, the process proceeds to step 90. In this case, when the necessary driving force Fdreq is 0, or when the elapsed time from the start of generation of the necessary driving force Fdreq is equal to or longer than the reference time, the control end condition for generating the necessary driving force Fdreq is It may be determined that it is established.

  In step 90, a command is output to the driving force control electronic control unit 68 to control the vehicle driving force Fd to the required driving force Fdreq, whereby the vehicle driving force Fd is changed to the required driving force Fdreq. Be controlled.

  In step 100, when a command for controlling the driving force Fd of the vehicle to the required driving force Fdreq is output to the electronic controller 68 for controlling the driving force, a command for setting the driving force Fd of the vehicle to 0 is issued. In this way, the generation of the driving force Fd of the vehicle is terminated. When the command for controlling the driving force Fd of the vehicle to the required driving force Fdreq is not output, the command for setting the driving force Fd of the vehicle to 0 is not output.

  In step 110, as in step 50, for example, whether or not the vehicle has stopped is determined by determining whether or not the vehicle speed V is equal to or less than the reference value V2, and if a negative determination is made. Returning to step 20, when an affirmative determination is made, the routine proceeds to step 120.

  In step 120, as in step 50, the product KpFbreq of the coefficient Kp for converting braking force into braking pressure and the reference braking force Fbreq is calculated as the reference braking pressure Pbreq corresponding to the reference braking force Fbreq. Further, the reference brake pressure Pbreq is used as an instruction differential pressure with respect to the communication control valves 22A and 22B so that the communication control valves 22A and 22B can maintain the brake pressure Pbreq even when the master cylinder pressure Pm becomes lower than the reference brake pressure Pbreq. The voltage of the control current for the solenoid of the communication control valve is controlled.

  In step 130, the operation of the pumps 42A and 42B is started by driving the motors of the pumps 42A and 42B.

  In step 140, it is determined whether or not the braking pressure Pi of each wheel is equal to or higher than the reference braking pressure Pbreq corresponding to the reference braking force Fbreq, and the braking pressure necessary for maintaining the vehicle in a stopped state is secured. If a negative determination is made, step 140 is repeatedly executed. If an affirmative determination is made, the process proceeds to step 150.

  In step 150, the pumps 42A and 42B are stopped by stopping the motors of the pumps 42A and 42B, whereby the pressure increase of the braking pressure Pi of each wheel is stopped, and then the process proceeds to step 160.

  In step 160, it is determined whether or not the braking force holding control should be terminated. When a negative determination is made, the process returns to step 20, and when an affirmative determination is made, it is shown in FIG. The routine control is terminated, and the communication control valves 22A and 22B are opened to return to normal braking force control.

  In this case, it may be determined that the braking force holding control should be terminated when the control of the differential pressure instruction is performed on the communication control valves 22A and 22B and the driving force Fd of the vehicle is zero. In addition, it is determined that the braking force holding control should be terminated in any case where the braking operation amount is increased by the driver, the acceleration operation is performed by the driver, or the parking brake is operated. Good. In particular, when the driver performs acceleration operation, the braking force holding control is already performed, and when the driving force is applied based on the necessary driving force Fdvreq, the driving force based on the necessary driving force Fdvreq is provided. The grant of is terminated.

  Thus, according to the first embodiment, it is determined in step 10 whether or not the driver is going to stop the vehicle, and when the driver is going to stop the vehicle, the vehicle is The braking force is controlled to be a braking force necessary to maintain the vehicle in a stopped state.

  In particular, when the braking force of the current vehicle by the driver's braking operation is equal to or greater than the reference braking force for maintaining the vehicle in a stopped state, an affirmative determination is made in step 40. In step 50, the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in a stopped state is used as the command differential pressure for the communication control valves 22A and 22B, and the voltage of the control current for the solenoids of these communication control valves. Is controlled.

  If the vehicle is stopped, an affirmative determination is made in steps 60 and 160, so that the braking pressure Pi of each wheel is braked even if the master cylinder pressure Pm becomes lower than the braking pressure Pbreq. The pressure is maintained at Pbreq. Therefore, even if the driver does not perform the braking operation and the brake pressure is not increased by the operation of the pumps 42A and 42B, the vehicle can be maintained in the stopped state.

  When the vehicle has not stopped yet, a negative determination is made in step 60, and the excess braking force Fbex generated by maintaining the differential pressure by the communication control valves 22A and 22B in step 70 is obtained. A driving force Fdreq necessary for canceling with the driving force Fd of the vehicle is calculated. Then, until an affirmative determination is made in step 80, the driving force Fd of the vehicle is controlled to the required driving force Fdreq in step 90.

  Therefore, the surplus braking force Fbex generated by maintaining the differential pressure by the communication control valves 22A and 22B can be offset by the driving force Fd of the vehicle. Therefore, it is possible to prevent the braking force and deceleration of the vehicle from rapidly increasing due to the start of the braking force holding control, and the vehicle occupant from feeling uncomfortable due to this.

  For example, FIG. 4 shows the case where the braking pressure Pi at the time when it is determined that the driver intends to stop the vehicle is equal to or higher than the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in the stopped state. It is a figure which shows the example of the change of the master cylinder pressure Pm when the vehicle stops by a person's braking operation, the braking pressure Pi of each wheel, and the driving force Fd of a vehicle.

  As shown in FIG. 4, at time t1, it is determined that the driver intends to stop the vehicle, and the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in the stopped state is set. Assume that the control of the differential pressure of the communication control valves 22A and 22B is started as the command differential pressure. Then, it is assumed that the braking pressure Pi becomes less than the braking pressure Pbreq corresponding to the reference braking force Fbreq at time t2, and it is determined that the vehicle has stopped at time t3.

  In this situation, control of the differential pressures of the flow control valves 22A and 22B is started at time t1, but the flow control valves 22A and 22B remain open until time t2 after time t1. The braking pressure Pi of each wheel decreases corresponding to the master cylinder pressure Pm. After the time t2, the control valves 22A and 22B are closed, and the braking pressure Pi is maintained at the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in a stopped state. The vehicle is maintained in a stopped state without requiring a braking operation.

  Further, after the time point t2, the braking pressure Pi becomes less than the braking pressure Pm corresponding to the driver's braking request, so the driving force Fd for canceling the surplus braking force Fbex until the time point t3 when the vehicle stops. Generated. The driving force Fd for canceling the surplus braking force Fbex after the time point t3 is 0, but the driving force is generated while decreasing after the time point t3 from the relationship of engine responsiveness. However, since the vehicle has already stopped and the braking force Fbreq that can maintain the vehicle in a stopped state is generated, the remaining driving force does not give the passenger an uncomfortable feeling.

  In this case, the driving force Fd of the vehicle is controlled to the required driving force Fdreq, and the required driving force Fdreq is calculated according to the above equation 2. Accordingly, it is possible to control the reduction amount of the braking force due to the application of the driving force Fd in accordance with the master cylinder pressure Pm which is the amount of braking operation by the driver. Then, the deceleration of the vehicle can be controlled according to the driver's braking intention.

  In FIG. 4, this shows that the curve of the driving force Fd of the vehicle between the time point t2 and the time point t3 is based on the braking pressure Pbreq line in the same section. This means that the curve is reversed and coincides with the curve when converted to braking force.

  When the driving force Fd of the vehicle is controlled to the required driving force Fdreq, it is determined in step 80 whether or not the control end condition for generating the required driving force Fdreq is satisfied. When the determination is made, the process proceeds to step 100. In step 100, the generation of the driving force Fd of the vehicle is terminated. Therefore, for example, when the driver travels downhill while performing a braking operation and the elapsed time from the start of generation of the necessary driving force Fdreq is longer than the reference time, the generation of the driving force Fd is unnecessarily generated. Can be prevented and fuel consumption of the vehicle can be prevented from deteriorating.

  Further, when the vehicle is stopped and an affirmative determination is made in step 60, the driving of the vehicle in step 100 is also performed when the driving force Fd of the vehicle is controlled to the required driving force Fdreq. Generation of force Fd is released. Therefore, it is possible to prevent the generation of the driving force Fd from being unnecessarily continued after the vehicle stops.

  Note that, for example, when the master cylinder pressure Pm changes as indicated by the wavy line in FIG. 4, the vehicle is driven by the driver's braking operation when it is determined that the driver intends to stop the vehicle. When the braking force is less than the reference braking force Fbreq for maintaining the vehicle in a stopped state, a negative determination is made in step 40. In steps 110 to 150, the same control as the conventional braking force holding control is performed.

  However, the determination in step 40 is the stage in which it is determined in step 10 that the driver intends to stop the vehicle. In other words, the amount of braking operation by the driver is not reduced as much as when the vehicle is stopped. Done in stages. Therefore, since the negative determination is not frequently performed in step 40, the differential pressure control of the communication control valve is started when it is determined that the vehicle has stopped, and the reference for the brake pressure Pi to maintain the vehicle in the stopped state. When it is less than the braking pressure Pbreq, the operating frequency of the pump can be reduced as compared with the conventional braking force holding control in which the braking pressure Pi is increased by the pump.

  For example, FIG. 5 shows that the braking pressure Pi at the time when it is determined that the vehicle is stopped in the conventional braking force holding control is equal to or higher than the reference braking pressure Pbreq corresponding to the reference braking force Fbreq for maintaining the vehicle in a stopped state. In the case of (A) and the case of being lower than the reference braking pressure Pbreq (B), examples of changes in the master cylinder pressure Pm and the braking pressure Pi of each wheel are shown.

  As shown in FIG. 5A, for example, when the driver is a beginner and the braking operation amount is not reduced immediately before the vehicle stops, the braking pressure Pi at the time when the vehicle is determined to stop is braked. The pressure is above Pbreq and the pump is not activated.

  However, generally, as shown in FIG. 5B, since the amount of braking operation is reduced by the driver immediately before the vehicle stops, the braking pressure Pi at the time when it is determined that the vehicle has stopped is braked. The pressure becomes less than Pbreq. Therefore, since the pump is operated until the braking pressure Pi becomes equal to or higher than the braking pressure Pbreq, the pump operating frequency increases.

On the other hand, according to the first embodiment, as shown in FIG. 4, even when the braking pressure Pi at the time when it is determined that the vehicle is stopped is less than the reference braking pressure Pbreq, the driver When it is determined that there is an intention to stop the vehicle, the braking pressure Pi is often equal to or higher than the reference braking pressure Pbreq. Therefore, the operation frequency of the pump can be reduced as compared with the case of the conventional braking force holding control.
[Second Embodiment]

  FIG. 3 is a flowchart showing a braking force holding control routine of the second embodiment of the braking force control apparatus according to the present invention.

  In this second embodiment, the braking force control electronic control device 60 stores the control flow of the braking force holding control routine shown in FIG. 3, and when the creep force reduction control start condition is satisfied. Then, the braking force holding control is performed according to the flowchart shown in FIG. 3 and the creep force reduction possibility determination control is performed.

  In particular, when it is estimated that the electronic control unit 60 can maintain the vehicle in a stopped state even if the braking operation amount is reduced and the braking pressure is reduced before the creep force reduction control is executed, After the braking force holding control is performed, the creep force reduction control is performed. On the other hand, when it is estimated that the vehicle cannot be maintained in the stopped state when the braking operation amount of the driver is reduced and the braking pressure is reduced until the creep force reduction control is executed, the electronic control unit 60 First performs creep force reduction control, and then performs braking force holding control.

  Next, the braking force holding control and the creep force reduction determination control in the second embodiment will be described with reference to the flowchart shown in FIG. Note that the control according to the flowchart shown in FIG. 3 is also started in a situation where the vehicle is in a running state, and is repeatedly executed every predetermined time.

  First, at step 210, it is determined whether or not the creep force reduction control start condition is satisfied. When a negative determination is made, the control by the routine shown in FIG. When the determination is made, the process proceeds to step 220.

  Whether or not the creep force reduction control start condition is satisfied is determined by the driving force control electronic control unit 68. Information on the determination result input from the driving force control electronic control unit 68 is used. Based on this, a determination in step 210 may be made. In addition, the permission condition for the control such as fuel cut that reduces the driving force generated by the engine and transmitted to the driving wheel is satisfied, when the vehicle speed V is equal to or lower than a preset reference value and the accelerator opening is zero. Sometimes, it may be determined that the start condition for the creep force reduction control is satisfied.

  In step 220, the reference braking force Fbreq for maintaining the vehicle in the stop state is calculated according to the above equation 1 as in step 20 in the first embodiment. In this case, since the creep force is reduced when the vehicle stops, the reference braking force Fbreq may be a braking force capable of maintaining the vehicle in a stopped state in a state where the creep force is reduced, and thus the reference braking force. The creep force Fcp used for the calculation of Fbreq may be a reduced value.

  In step 230, the expected decrease in braking pressure ΔPb (positive value) due to the reduction in the amount of braking operation performed by the driver before the start of creep force reduction control is, for example, a change in the master cylinder pressure Pm and the vehicle speed. Is calculated based on Whether the product KfPm of the coefficient Kf for converting the braking pressure into the braking force and the master cylinder pressure Pm is equal to or larger than the sum of the reference braking force Fbreq and the expected braking force decrease amount KfΔPb corresponding to the expected braking pressure decrease amount ΔPb. Is determined. That is, it is determined whether or not the vehicle can be maintained in a stopped state even if the braking operation amount of the driver is reduced and the braking pressure is reduced before the creep force reduction control is started.

  If a negative determination is made in step 230, the process proceeds to step 300. If an affirmative determination is made, a command signal for prohibiting creep force reduction control is output to the driving force control electronic control unit 68 in step 240. Then, the process proceeds to step 250.

  In step 250, whether or not the vehicle has stopped is determined by determining whether or not the vehicle speed V is less than or equal to the reference value V2 as in steps 60 and 110 in the first embodiment described above, for example. When the determination is made and the negative determination is made, the control by the routine shown in FIG. 3 is once ended, and when the affirmative determination is made, the routine proceeds to step 260.

  In step 260, as in the case of steps 50 and 120 in the first embodiment described above, the product KpFbreq of the coefficient Kp for converting the braking force into the braking pressure and the reference braking force Fbreq is the reference braking force Fbreq. Is calculated as a reference braking pressure Pbreq corresponding to. Further, the reference brake pressure Pbreq is used as an instruction differential pressure with respect to the communication control valves 22A and 22B so that the communication control valves 22A and 22B can maintain the brake pressure Pbreq even when the master cylinder pressure Pm becomes lower than the reference brake pressure Pbreq. The voltage of the control current for the solenoid of the communication control valve is controlled.

  In step 270, as in step 140 in the first embodiment described above, the braking pressure Pi of each wheel is equal to or higher than the reference braking pressure Pbreq corresponding to the reference braking force Fbreq, and the vehicle is stopped. It is determined whether or not a braking pressure that can be maintained at has been secured. When a negative determination is made, in step 280, the pumps 42A and 42B are actuated by driving the motors of the pumps 42A and 42B, whereby the braking pressure Pi of each wheel is increased above the reference braking pressure Pbreq. The

  On the other hand, when an affirmative determination is made in step 270, if the motors of the pumps 42A and 42B are not driven, the process proceeds to step 290, and if the motors of the pumps 42A and 42B are driven. After the motors are stopped, the process proceeds to step 290.

  In step 290, a command signal for permitting the creep force reduction control is output to the driving force control electronic control unit 68, whereby the driving force control electronic control unit 68 starts the creep force reduction control. The control by the routine shown in FIG.

  In step 300, a command signal for permitting creep force reduction control is output to the driving force control electronic control unit 68, whereby creep force reduction control is started by the driving force control electronic control unit 68. In 310-330, the same control as in steps 250-270 is performed.

  Thus, according to the second embodiment, when the creep force reduction control start condition is satisfied, an affirmative determination is made in step 210, and a criterion for maintaining the vehicle in a stopped state in step 220. The braking force Fbreq is calculated. In step 230, it is determined whether or not the vehicle can be kept stopped even when the braking operation amount is reduced and the braking pressure is reduced until the creep force reduction control is started. This is performed based on Pm and the reference braking force Fbreq.

  When the vehicle can be maintained in a stopped state, an affirmative determination is made at step 230, and a command signal for prohibiting creep force reduction control is output to the driving force control electronic control unit 68 at step 240. Therefore, it is possible to suppress the braking operation amount of the driver from being reduced along with the execution of the creep force reduction control and the reduction of the braking pressure Pi of each wheel below the reference braking pressure Pbreq due to this.

  When the vehicle stops, an affirmative determination is made in step 250, and in step 260, the reference braking pressure Pbreq is used as an instruction differential pressure for the communication control valves 22A and 22B, and the voltage of the control current for the solenoids of these communication control valves. Is controlled. Therefore, even if the master cylinder pressure Pm becomes less than the reference braking pressure Pbreq, the reference braking pressure Pbreq can be maintained by the differential pressure control of the communication control valves 22A and 22B, and thus the vehicle can be maintained in a stopped state.

  For example, as shown in FIG. 6, if the start condition of the creep force reduction control is satisfied at the time point t1, in the case of the conventional braking force holding control, the creep force reduction control starts at the time point t1. Is done. Therefore, even if the master cylinder pressure Pm changes as indicated by the solid line unless the creep force reduction control is started, the braking force required for vehicle deceleration is reduced along with the creep force reduction control. The cylinder pressure Pm changes as indicated by the broken line.

  For this reason, the braking pressure Pi at the time point t2 when it is determined that the vehicle has stopped becomes less than the reference braking pressure Pbreq, and the pump must be operated to increase the braking pressure Pi to the reference braking pressure Pbreq or higher. Many. Therefore, it is inevitable that the pump operation frequency becomes high.

  On the other hand, according to the second embodiment, even if the start condition of the creep force reduction control is satisfied at the time point t1, the creep force reduction control is not started at the time point t1, and the braking is performed in step 270. Creep force reduction control is prohibited until it is determined that the pressure Pi is equal to or higher than the reference braking pressure Pbreq. Accordingly, the master cylinder pressure Pm does not decrease as shown by the broken line in FIG. 6 but gently decreases as shown by the solid line. Therefore, the braking pressure Pi at the time point t2 when it is determined that the vehicle has stopped becomes equal to or higher than the reference braking pressure Pbreq, and the pump does not need to be operated.

  In the second embodiment, the vehicle is stopped, and these communication control valves are controlled using the reference braking pressure Pbreq as an instruction differential pressure with respect to the communication control valves 22A and 22B. In some cases, the pressure drops below the reference braking pressure Pbreq. In this case, the pumps 42A and 42B are operated in steps 270 and 280, whereby the braking pressure Pi of each wheel is increased to the reference braking pressure Pbreq or higher. Therefore, although an affirmative determination is made in step 230, even when the braking pressure Pi of each wheel falls below the reference braking pressure Pbreq, the vehicle can be reliably maintained in a stopped state.

  When the vehicle stops when the braking pressure Pi of each wheel exceeds the reference braking pressure Pbreq, or when the vehicle stops and the braking pressure Pi of each wheel exceeds the required braking pressure Pbreq, the creep force reduction control is performed at step 290. A command signal to be permitted is output to the driving force control electronic control unit 68, whereby the creep force reduction control is started. Accordingly, it is possible to start the creep force reduction control while ensuring the situation in which the vehicle is maintained in the stopped state.

  In addition, the creep condition reduction control start condition is satisfied, and an affirmative determination is made in step 210, but the braking operation amount of the driver is reduced and the vehicle is stopped until the creep force reduction control is started. If it cannot be maintained at step 230, a negative determination is made at step 230. In step 300, a command signal for permitting the creep force reduction control is output to the driving force control electronic control unit 68, whereby the creep force reduction control is started.

  Therefore, compared to the case where the creep force reduction control is started after the completion of the control of the braking pressure for maintaining the vehicle in the stopped state in steps 310 to 340, in other words, steps 240 to 290 are not executed without executing step 230. As compared with the case where is executed, the creep force lowering control can be started earlier, thereby improving the fuel efficiency of the vehicle.

  Further, steps 310 to 340 are executed after step 300, whereby the braking pressure Pi of each wheel is controlled to be equal to or higher than the reference braking pressure Pbreq. Therefore, even if a negative determination is made in step 230, the vehicle Can be reliably maintained in a stopped state.

  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 each of the above-described embodiments, the communication control valve that restricts the flow of the working fluid from the wheel cylinder to the master cylinder is a normally open linear solenoid valve, and the pressure on the side opposite to the master cylinder 14 However, the differential pressure is maintained so as to be higher than the pressure on the master cylinder 14 side, and the differential pressure is increased or decreased according to the voltage of the drive current. However, the communication control valve is not limited to a linear solenoid valve, but an electromagnetic on-off valve that switches between a valve opening position for connecting the wheel cylinder and the master cylinder and a valve closing position for disconnecting the communication between the wheel cylinder and the master cylinder. It may be.

  When the communication control valve is an electromagnetic open / close valve, the electromagnetic open / close valve is closed in a situation where the control of the communication control valves 22A and 22B is started using the reference braking pressure Pbreq as an instruction differential pressure. For example, in the case of the first embodiment described above, the electromagnetic on-off valve is closed in steps 40 and 110, and when an affirmative determination is made in step 150, the electromagnetic on-off valve is opened. In the case of the second embodiment described above, the electromagnetic on-off valve is closed in steps 260 and 320.

In the first and second embodiments described above, the reference braking force Fbreq for maintaining the vehicle in the stopped state is calculated according to Equation 1, but the margin coefficients Ka1 and Ka2 are set to 2. As a positive constant greater than about 1, the reference braking force Fbreq may be calculated according to Equation 3 below.
Fbreq = Ka1Fcp + Ka2Fsx (3)

  In the first and second embodiments described above, if the vehicle cannot be maintained in a stopped state unless the braking pressure Pi is increased, the reference braking pressure Pbreq is set at steps 120 and 320. Control of the communication control valves 22A and 22B is started as the command differential pressure. However, in the first embodiment, the vehicle is stopped between steps 110 and 120, and in the second embodiment, between steps 310 and 320. The reference braking force Fbreq to be calculated may be calculated again, and the steps 120 and 320 may be modified based on the calculated value.

In these cases, the reference braking force Fbreq is calculated after the vehicle stops, and the margin coefficient for calculating the reference braking force Fbreq may be small. Therefore, for example, the reference braking force Fbreq may be calculated according to the following equation 4 with Kb being a positive constant smaller than Ka.
Fbreq = Kb (Fcp + Fsx) (4)

In the first embodiment described above, the necessary driving force Fdreq is calculated according to Equation 2 as a driving force for canceling the surplus braking force Fbex. However, for example, assuming that Kc is a positive constant larger than 0 and smaller than 1, the necessary driving force Fdreq is calculated according to the following equation 5 so that the driving force Fdreq is smaller than the driving force for canceling the surplus braking force Fbex. Also good. In that case, the fuel consumption of the vehicle can be improved as compared with the first and second embodiments described above.
Fdreq = KcKf (Pbreq-Pm) (5)

  Further, in the first embodiment described above, the necessary driving force Fdreq is calculated according to Equation 2 without being limited in magnitude. However, when the calculated driving force Fdreq exceeds the reference value, the necessary driving force Fdreq may be corrected so as to be limited to a reference value or less.

  In the second embodiment described above, the step corresponding to step 150 in the first embodiment is not performed. However, in the second embodiment, it is preset. If the end condition is satisfied, the braking force holding control may be corrected to end.

  DESCRIPTION OF SYMBOLS 10 ... Braking device, 14 ... Master cylinder, 22A, 22B ... Communication control valve, 26FL, 26FR, 26RL, 26RR ... Wheel cylinder, 42A, 42B ... Oil pump, 28FL-28RR, 34FL-34RR ... Open / close valve, 38A, 38A ... Reservoir, 42A, 42A ... Pump, 44A, 44A ... Damper, 60 ... Electronic control device for braking force control, 62 ... Pressure sensor, 64i ... Pressure sensor, 66 ... Vehicle speed sensor, 68 ... Electronic control device for driving force control

Claims (3)

  In a braking force control device for a vehicle that performs braking force holding control that suppresses a decrease in pressure in the wheel cylinder by restricting the working fluid from flowing from the wheel cylinder to the master cylinder, the driver performs a braking operation. When it is determined that the vehicle is going to be stopped, it is determined whether or not the braking force holding control is started based on the amount of braking operation of the driver, and the reference from the time when the braking force holding control is started. A braking force control device for a vehicle, characterized in that the braking force holding control is terminated when the vehicle does not stop even after a time period has elapsed.   In a vehicle braking force control device that performs braking force holding control that suppresses a decrease in pressure in the wheel cylinder by restricting the working fluid from flowing from the wheel cylinder to the master cylinder, the creep force is suppressed. Even if the situation should be, if it is estimated that the braking force due to the driver's braking operation when the vehicle stops is equal to or greater than the reference value for maintaining the vehicle in the stopped state, the control is performed without suppressing the creep force. A braking force control device for a vehicle, characterized by performing power holding control. The braking force control device is estimated that the braking force by the driver's braking operation when the vehicle stops is equal to or greater than the reference value, but the braking force by the driver's braking operation when the vehicle stops is the reference value. When it is less than the value, the pressure in the wheel cylinder is increased to increase the braking force of the vehicle to the reference value or more to perform the braking force holding control, and then suppress the creep force. The vehicle braking force control device according to claim 2 .

Images