JP7172526B2 - vehicle braking controller - Google Patents

Description

The present invention relates to a vehicle braking control device.

The applicant has developed a braking control device as described in Patent Document 1 in order to ensure sufficient regenerative energy and improve vehicle deceleration and directional stability. Specifically, in the brake control device of Patent Document 1, when the brake fluid pressures of the front and rear wheels are individually adjusted by the first and second pressure regulating valves arranged in series in the return path of the brake fluid, the brake fluid Mutual interference of pressure is suppressed. Here, the first pressure regulating valve is provided in a brake fluid return path including the electric pump, adjusts the brake fluid to a first hydraulic pressure, and adjusts the rear wheel hydraulic pressure of the rear wheel cylinder with the first hydraulic pressure. . The second pressure regulating valve is provided in the return path, reduces the first hydraulic pressure to the second hydraulic pressure, and adjusts the front wheel hydraulic pressure of the front wheel cylinder with the second hydraulic pressure. Then, the front wheel flow rate required to increase the front wheel hydraulic pressure is calculated based on the operation amount of the braking operation member and the regeneration amount of the regenerative generator, and the first pressure regulating valve is controlled based on the front wheel flow rate. be.

In the brake control device of Patent Literature 1, the flow of brake fluid in the return path including the electric pump is throttled by the first and second pressure regulating valves to adjust the brake fluid pressures of the four wheels. The braking control device is of a so-called brake-by-wire system, and the sudden increase in braking fluid pressure during sudden braking is performed using an electric pump as a power source. Therefore, there is a demand for a system capable of efficiently ensuring vehicle deceleration while coping with sudden braking.

Japanese Patent Application No. 2018-119954

SUMMARY OF THE INVENTION It is an object of the present invention to provide a brake control device for a vehicle in which the brake fluid pressures of the front and rear wheels are individually adjusted by a plurality of pressure regulating valves arranged in series in a brake fluid return path, whereby the brake fluid pressures are efficiently adjusted. , vehicle deceleration can be ensured.

A braking control system (SC) for a vehicle according to the present invention is applied to a vehicle having regenerative generators (GN) for front wheels (WHf). A braking control device (SC) of a vehicle is provided in a return path (A) of a brake fluid (BF) including an electric pump (DN), and supplies the brake fluid (BF) discharged by the electric pump (DN) as a second brake fluid (BF). 1 hydraulic pressure (Pb) and adjusts the rear wheel hydraulic pressure (Pwr) of the rear wheel cylinder (CWr) by the first hydraulic pressure (Pb); The first hydraulic pressure (Pb) is reduced to the second hydraulic pressure (Pc), and the second hydraulic pressure (Pc) reduces the front wheel hydraulic pressure (Pwf) of the front wheel cylinder (CWf). )”, and a “controller (ECU) for controlling the electric pump (DN) and the first and second pressure regulating valves (UB, UC)”.

In the vehicle braking control device (SC) according to the present invention, the controller (ECU) controls the amount of operation (Ba) of the braking operation member (BP) of the vehicle, and the distance between the object in front of the vehicle and the vehicle. Abrupt braking is determined based on at least one of the required decelerations (Gj) corresponding to the distance (Ob), and when the abrupt braking is determined, the first pressure regulating valve (UB) is fully opened. Also, the second pressure regulating valve (UC) is configured to be fully closed.

According to the above configuration, since the second pressure regulating valve UC is in the fully closed state, the total amount of the braking fluid BF discharged by the fluid pump HP is adjusted to the front and rear wheel hydraulic pressures Pwf and Pwr (particularly, the hydraulic pressure rise). Furthermore, since the first pressure regulating valve UB is fully opened, the maximum possible amount of brake fluid BF is supplied to regulate the front wheel hydraulic pressure Pwf. Therefore, the front wheel hydraulic pressure Pwf is efficiently increased, and the vehicle can be quickly decelerated.

Further, the braking control device (SC) for a vehicle according to the present invention is applied to a vehicle equipped with a regenerative generator (GN) for rear wheels (WHr). A braking control device (SC) of a vehicle is provided in a return path (A) of a brake fluid (BF) including an electric pump (DN), and supplies the brake fluid (BF) discharged by the electric pump (DN) as a second brake fluid (BF). 1 hydraulic pressure (Pb), and adjusts the front wheel hydraulic pressure (Pwf) of the front wheel wheel cylinder (CWf) by the first hydraulic pressure (Pb); A), the first hydraulic pressure (Pb) is reduced to the second hydraulic pressure (Pc), and the second hydraulic pressure (Pc) causes the rear wheel hydraulic pressure (Pwr) of the rear wheel cylinder (CWr) )”, and a “controller (ECU) for controlling the electric pump (DN) and the first and second pressure regulating valves (UB, UC)”.

In the vehicle braking control device (SC) according to the present invention, the controller (ECU) controls the amount of operation (Ba) of the braking operation member (BP) of the vehicle, and the distance between the object in front of the vehicle and the vehicle. Sudden braking is determined based on at least one of the required decelerations (Gj) corresponding to the distance (Ob), and when the sudden braking is determined, the first pressure regulating valve (UB) is fully closed. state.

According to the above configuration, since the first pressure regulating valve UB is driven to the fully closed state, the entire amount of the brake fluid BF discharged by the fluid pump HP is used to increase the front wheel hydraulic pressure Pwf. Therefore, the front wheel hydraulic pressure Pwf is efficiently increased, and the vehicle can be quickly decelerated.

Further, in the vehicle braking control device (SC) according to the present invention, the controller (ECU) is configured to fully close the second pressure regulating valve (UC) when the sudden braking is determined. be done. When the maximum differential pressure of the first pressure regulating valve UB is low, the first pressure regulating valve UB may be relieved (automatically opened) at the maximum differential pressure. In addition to the first pressure regulating valve UB, the second pressure regulating valve UC is also fully closed. Therefore, even if relief occurs in the first pressure regulating valve UB, the braking fluid BF from the electric pump DN is effectively released into the servo chamber. It is supplied to Rs and has the same effects as above.

1 is an overall configuration diagram for explaining a first embodiment of a vehicle braking control device SC according to the present invention; FIG. FIG. 4 is a flow chart for explaining pressure regulation control processing; FIG. 5 is a flow chart for explaining normal processing of pressure regulation control; FIG. 5 is a flow chart for explaining sudden braking processing of pressure regulation control corresponding to the first embodiment; FIG. 2 is an overall configuration diagram for explaining a second embodiment of a vehicle braking control device SC according to the present invention; FIG. 11 is a flowchart for explaining sudden braking processing of pressure regulation control corresponding to the second embodiment;

<Symbols of components, etc., and subscripts at the end of the symbols>
In the following description, constituent members, arithmetic processing, signals, characteristics, and values denoted by the same symbols such as "ECU" have the same function. The suffixes “i” to “l” attached to the end of the symbol relating to each wheel are generic symbols indicating which wheel it relates to. Specifically, "i" indicates the right front wheel, "j" indicates the left front wheel, "k" indicates the right rear wheel, and "l" indicates the left rear wheel. For example, the four wheel cylinders are denoted as a right front wheel cylinder CWi, a left front wheel cylinder CWj, a right rear wheel cylinder CWk, and a left rear wheel cylinder CWl. Furthermore, the subscripts “i” to “l” at the end of the symbols can be omitted. If the subscripts "i" to "l" are omitted, each symbol represents a generic name for each of the four wheels. For example, "WH" represents each wheel and "CW" represents each wheel cylinder.

The suffixes “f” and “r” attached to the end of the symbols relating to the braking system are generic symbols indicating which systems of the front and rear wheels it relates to. Specifically, "f" indicates the front wheel system, and "r" indicates the rear wheel system. For example, the wheel cylinders CW of each wheel are denoted as front wheel cylinders CWf (=CWi, CWj) and rear wheel cylinders CWr (=CWk, CWl). Furthermore, the subscripts "f" and "r" at the end of the symbols can be omitted. If the subscripts "f" and "r" are omitted, each symbol represents a generic term for each of the two braking systems. For example, "CW" represents wheel cylinders in the front and rear braking systems.

In the fluid path, the side closer to the reservoir RV (the side farther from the wheel cylinder CW) is called "upper", and the side closer to the wheel cylinder CW (the side farther from the reservoir RV) is called "lower". Further, in the circulation (A) of the brake fluid BF, the side closer to the discharge port of the fluid pump HP is called the "upstream side", and the side farther from the discharge port is called the "downstream side".

<First Embodiment of Braking Control Device SC>
A first embodiment of a braking control device SC according to the present invention will be described with reference to the overall configuration diagram of FIG. In the first embodiment, a so-called back-and-forth type is adopted as the two-system fluid passage. Here, the fluid path is a path for moving the brake fluid BF, which is the working fluid of the brake control device SC, and corresponds to a brake pipe, a fluid channel in the fluid unit, a hose, and the like.

The vehicle is a hybrid vehicle or an electric vehicle having an electric motor GN for driving. The electric motor GN for driving also functions as a generator for regenerating energy. For example, the generator GN is provided for the front wheels WHi, WHj (=WHf). The generator GN is controlled by a drive controller ECD.

A vehicle is equipped with a driving support system so as to avoid a collision with an obstacle (corresponding to an "object") or to reduce damage at the time of collision. The driving assistance system includes a distance sensor OB and a driving assistance controller ECJ. A distance sensor OB detects a distance (relative distance) Ob between an object (another vehicle, a fixed object, a person, a bicycle, etc.) present in front of the own vehicle and the own vehicle. For example, a camera, radar, or the like is adopted as the distance sensor OB. The distance Ob is input to the driving assistance controller ECJ. The driving assistance controller ECJ calculates the required deceleration Gj based on the relative distance Ob.

The vehicle is equipped with a brake operating member BP, a wheel cylinder CW, a wheel speed sensor VW, a master reservoir RV, an upper fluid unit YU and a lower fluid unit YL.

A braking operation member (for example, a brake pedal) BP is a member operated by the driver to decelerate the vehicle. By operating the braking operation member BP, the braking torque of the wheels WH is adjusted, and braking force is generated on the wheels WH. Specifically, a rotating member (for example, a brake disc) KT is fixed to the wheel WH of the vehicle. A brake caliper is arranged so as to sandwich the rotating member KT.

The brake caliper is provided with a wheel cylinder CW. By increasing the pressure (brake fluid pressure) Pw of the brake fluid BF in the wheel cylinder CW, the friction member (for example, brake pad) is pressed against the rotating member KT. Since the rotary member KT and the wheels WH are fixed so as to rotate integrally, braking torque (frictional braking force) is generated in the wheels WH by the frictional force generated at this time.

Each wheel WH is equipped with a wheel speed sensor VW to detect a wheel speed Vw, which is the rotational speed of the wheel WH. A signal representing the wheel speed Vw is used for anti-skid control or the like for suppressing the locking tendency of the wheels WH. Each wheel speed Vw detected by the wheel speed sensor VW is input to the lower controller ECL. The lower controller ECL calculates the vehicle body speed Vx based on the wheel speed Vw.

The master reservoir (atmospheric pressure reservoir, also simply called "reservoir") RV is a tank for hydraulic fluid, in which brake fluid BF is stored. The reservoir RV is connected to the upper fluid unit YU.

<Upper Fluid Unit YU>
The upper hydraulic unit YU is composed of an operation amount sensor BA, a master unit YM, a pressure regulating unit YC, a regenerative coordination unit YK, and an upper controller ECU.

An operation amount sensor BA is provided to detect an operation amount Ba of a braking operation member (brake pedal) BP by a driver. At least one of the sensors listed below is provided as the manipulated variable sensor BA. An operation displacement sensor SP is provided for detecting an operation displacement Sp of the braking operation member BP. An operating force sensor FP is provided to detect the operating force Fp of the brake operating member BP. A simulator hydraulic pressure sensor PS is provided to detect the hydraulic pressure (simulator hydraulic pressure) Ps in the stroke simulator SS. An input hydraulic pressure sensor PN is provided to detect the hydraulic pressure (input hydraulic pressure) Pn in the input chamber Rn of the regenerative coordination unit YK. That is, the operation amount sensor BA is a general term for the above-described operation displacement sensor SP, etc., and the detected operation amount Ba includes the operation displacement Sp, the operation force Fp, the simulator hydraulic pressure Ps, and the input hydraulic pressure Pn. At least one is used. The detected braking operation amount Ba is input to the upper controller ECU.

The upper controller ECU controls the pressure regulation unit YC and the regenerative coordination unit YK. Specifically, based on the operation amount Ba, "electric motor MT of pressure regulating unit YC and first and second pressure regulating valves UB and UC" and "first and second opening/closing of regenerative coordination unit YK valves VA, VB" are controlled. The upper controller ECU is connected to the lower controller ECL, drive controller ECD, and driving support controller ECJ via a communication bus BS so that each signal (sensor detection value, calculated value, etc.) is shared.

[Master unit YM]
The master unit YM adjusts the hydraulic pressure Pwf (front wheel hydraulic pressure) in the front wheel cylinder CWf via the master cylinder chamber Rm of the master cylinder CM. The master unit YM includes a master cylinder CM, a master piston PM, and a master elastic body SM.

The master cylinder CM is a stepped cylinder member having a bottom (ie, having a small diameter portion and a large diameter portion). A single type is adopted as the master cylinder CM. The master piston PM is a piston member inserted inside the master cylinder CM, and has a collar portion (flange) Tm. The master cylinder CM and the master piston PM are sealed with a seal SL. The master piston PM can move in conjunction with the operation of the braking operation member BP. The interior of the master cylinder CM is partitioned into three hydraulic pressure chambers Rm, Rs, and Ro by the master piston PM. The master piston PM can move smoothly along the central axis Jm of the master cylinder CM.

A master cylinder chamber (simply referred to as a “master chamber”) Rm is a hydraulic chamber defined by “a small-diameter inner peripheral portion and a small-diameter bottom portion of the master cylinder CM” and the end portion of the master piston PM. A master cylinder fluid passage HM is connected to the master chamber Rm. The master chamber Rm is finally connected to the front wheel cylinders CWf (=CWi, CWj) via the lower fluid unit YL.

The interior of the master cylinder CM is divided into a servo hydraulic pressure chamber (also simply referred to as a "servo chamber") Rs and a reaction force hydraulic pressure chamber (simply referred to as a "reaction force chamber") Ro by the collar portion Tm of the master piston PM. divided into The servo chamber Rs is a hydraulic chamber defined by "the large-diameter inner peripheral portion and the large-diameter bottom portion of the master cylinder CM" and the flange portion Tm of the master piston PM. A second supply fluid passage HC is connected to the servo chamber Rs, and a second regulated hydraulic pressure Pc is introduced from the pressure regulating unit YC.

The reaction force chamber Ro is a hydraulic chamber defined by the large-diameter inner peripheral portion of the master cylinder CM, the stepped portion, and the flange portion Tm of the master piston PM. The reaction force chamber Ro is sandwiched between and positioned between the master hydraulic chamber Rm and the servo hydraulic chamber Rs in the direction of the center axis Jm. In other words, the servo chamber Rs and the reaction force chamber Ro are arranged to face each other with the flange portion Tm interposed therebetween. Therefore, when the volume of the servo chamber Rs is increased, the volume of the reaction chamber Ro is decreased. Conversely, when the servo chamber volume is decreased, the reaction force chamber volume is increased. A simulator fluid passage HS is connected to the reaction force chamber Ro. The reaction force chamber Ro adjusts the amount of the damping fluid BF in the upper fluid unit YU.

A master elastic body (for example, a compression spring) SM is provided between the end of the master piston PM and the small-diameter bottom of the master cylinder CM. The master elastic body SM presses the master piston PM against the large-diameter bottom portion of the master cylinder CM in the direction of the central axis Jm of the master cylinder CM. During non-braking, the master piston PM is in contact with the large-diameter bottom of the master cylinder CM. The position of the master piston PM in this state is called the "initial position of the master unit YM".

The master cylinder CM is provided with a through hole and connected to the master reservoir RV. When the master piston PM is at the initial position (that is, during non-braking), the master chamber Rm is brought into communication with the reservoir RV.

In the master chamber Rm, an urging force Fb (referred to as "retreating force") in the retreating direction Hb along the central axis Jm is applied by its internal pressure ("master cylinder hydraulic pressure", also referred to as "master hydraulic pressure") Pq. Granted to the master piston PM. The servo chamber Rs applies an urging force Fa (referred to as "forward force") in the forward direction Ha opposite to the backward force Fb to the master piston PM by its internal pressure (that is, the introduced second adjustment hydraulic pressure Pc). . That is, in the master piston PM, the advancing force Fa due to the hydraulic pressure Pc in the servo chamber Rs and the retreating force Fb due to the hydraulic pressure (master hydraulic pressure) Pq in the master chamber Rm oppose each other in the direction of the central axis Jm ( facing each other), statically balanced. A master cylinder pressure sensor PQ is provided to detect the master cylinder pressure Pq. For example, a master cylinder hydraulic pressure sensor PQ may be provided in the master cylinder fluid path HM. Also, the master cylinder pressure sensor PQ may be included in the lower fluid unit YL.

[Pressure adjustment unit YC]
The pressure regulating unit YC includes an electric pump DN, a check valve GC, first and second pressure regulating valves UB and UC, and first and second regulating hydraulic pressure sensors PB and PC. The pressure regulating unit YC adjusts the hydraulic pressure Pwf of the front wheel cylinder CWf (“front wheel braking hydraulic pressure” and equivalent to “front wheel hydraulic pressure”) and the hydraulic pressure Pwr of the rear wheel cylinder CWr (“rear wheel braking hydraulic pressure”). and corresponds to "rear wheel hydraulic pressure") are independently and individually adjusted. Specifically, the braking fluid pressure Pwf of the front wheels WHf provided with the generator GN is independently adjusted within a range equal to or lower than the braking fluid pressure Pwr of the rear wheels WHr not provided with the generator GN.

The electric pump DN is composed of an electric motor MT and a fluid pump HP, which rotate together. In the fluid pump HP, the suction port is connected to the first reservoir fluid line HV. A discharge port of the fluid pump HP is connected to one end of the pressure regulating fluid passage HA. A check valve GC is provided in the vicinity of the discharge port of the fluid pump HP in the pressure regulating fluid passage HA. The other end of the pressure regulation fluid passage HA is connected to the second reservoir fluid passage HU via the second pressure regulation valve UC. The first and second reservoir fluid paths HV, HU are connected to the master reservoir RV. That is, the first and second reservoir fluid paths HV, HU and the pressure regulating fluid path HA form a return path (A) for the brake fluid BF including the fluid pump HP. Here, the "return path" is a fluid path through which the braking fluid BF is circulated and returned to its original flow.

Two pressure regulating valves UB and UC are provided in series in the pressure regulating fluid passage HA. Specifically, the pressure regulating fluid passage HA is provided with a first pressure regulating valve UB downstream of the check valve GC, and a second pressure regulating valve UC is disposed at the other end of the pressure regulating fluid passage HA. be done. One end of the second reservoir fluid passage HU is connected to the second pressure regulating valve UC. Therefore, in the pressure regulating fluid passage HA, which is a part of the return passage (A), the first pressure regulating valve UB is arranged on the upstream side and the second pressure regulating valve UC is arranged on the downstream side.

The first and second pressure regulating valves UB and UC are linear solenoid valves (proportional valves, differential pressure valves) whose opening amount (lift amount) is continuously controlled based on the energized state (for example, supply current). be. The first and second pressure regulating valves UB and UC are controlled by the upper controller ECU based on drive signals Ub and Uc. Normally open solenoid valves are employed as the first and second pressure regulating valves UB and UC.

When the electric pump DN is rotationally driven, a reflux of the brake fluid BF (flow of the circulating brake fluid BF) is formed like "HV->HP->GC->UB->UC->HU->RV->HV". In other words, the return path (A) for the brake fluid BF includes the fluid pump HP, the first and second pressure regulating valves UB and UC, and the reservoir RV. Note that the second pressure regulating valve UC may be connected to the first reservoir fluid passage HV at the portion Bv. In this case, the return path (A) is in the order of "HV→HP→GC→UB→UC→HU→HV".

When the first and second pressure regulating valves UB and UC are in a fully open state (they are of the normally open type and thus are not energized), the hydraulic pressures (adjusted hydraulic pressures) Pb and Pc in the pressure regulating fluid passage HA are Both are approximately "0 (atmospheric pressure)". When the amount of energization to the first pressure regulating valve UB is increased and the return passage (A) is throttled by the pressure regulating valve UB, the hydraulic pressure Pb on the upstream side of the first pressure regulating valve UB in the pressure regulating fluid passage HA becomes "0". is incremented from The hydraulic pressure Pb is the hydraulic pressure between the fluid pump HP (particularly, the check valve GC) and the first pressure regulating valve UB, and is called "first regulating hydraulic pressure (corresponding to "first hydraulic pressure")". be.

In addition, when the amount of energization to the second pressure regulating valve UC is increased and the return passage (A) is throttled by the pressure regulating valve UC, the fluid pressure on the upstream side of the second pressure regulating valve UC in the pressure regulating fluid passage HA becomes “0”. ” is incremented from . The hydraulic pressure Pc is the hydraulic pressure between the first pressure regulating valve UB and the second pressure regulating valve UC, and is called "second regulating hydraulic pressure (corresponding to 'second hydraulic pressure')".

Since the first and second pressure regulating valves UB and UC are arranged in series with the pressure regulating fluid passage HA, the second regulating hydraulic pressure Pc (second hydraulic pressure) regulated by the second pressure regulating valve UC is It is equal to or less than the first adjustment hydraulic pressure Pb (first hydraulic pressure) (that is, "Pc≦Pb"). The first pressure regulating valve UB adjusts the first regulating hydraulic pressure Pb, and the second pressure regulating valve UC reduces the first regulating hydraulic pressure Pb to adjust the second regulating hydraulic pressure Pc. In other words, the second pressure regulating valve UC adjusts the second regulating hydraulic pressure Pc to increase from "0 (atmospheric pressure)", and the first pressure regulating valve UB adjusts the first regulating hydraulic pressure Pb to the second It is adjusted to increase from the adjusted hydraulic pressure Pc. The pressure regulating unit YC is provided with first and second regulating hydraulic pressure sensors PB and PC to detect the first and second regulating hydraulic pressures Pb and Pc. Since the specifications (pressure receiving area, etc.) of the master unit YM are known, the second adjustment hydraulic pressure Pc can be calculated based on the master cylinder hydraulic pressure Pq, which is the detection result of the master cylinder hydraulic pressure sensor PQ. In this case, the second adjustment hydraulic pressure sensor PC may be omitted.

The pressure regulating fluid passage HA branches into a first supply fluid passage HB at a portion Bh between the fluid pump HP and the first pressure regulating valve UB. The first supply fluid passage HB is connected to the rear wheel cylinder CWr via the lower fluid unit YL. Therefore, the first adjustment hydraulic pressure Pb is directly introduced (supplied) to the rear wheel hall cylinder CWr. Further, the pressure regulating fluid passage HA is branched into the second supply fluid passage HC at a portion Bm between the first pressure regulating valve UB and the second pressure regulating valve UC. The second supply fluid path HC is connected to the servo chamber Rs. Therefore, the second adjustment hydraulic pressure Pc is introduced (supplied) into the servo chamber Rs. Since the master cylinder CM is connected to the front wheel cylinder CWf via the lower fluid unit YL, the second adjustment hydraulic pressure Pc is indirectly introduced to the front wheel cylinder CWf via the master cylinder CM. be. Therefore, the first adjustment hydraulic pressure Pb adjusts the rear wheel hydraulic pressure Pwr of the rear wheel cylinder CWr, and the second adjustment hydraulic pressure Pc adjusts the front wheel hydraulic pressure Pwf of the front wheel cylinder CWf.

Since the first adjustment hydraulic pressure Pb and the second adjustment hydraulic pressure Pc are adjusted independently and separately within the range of "Pb≧Pc", the front and rear distribution of the braking force is optimized, and the regenerative cooperation control is executed. Therefore, deceleration and stability of the vehicle can be ensured, and regenerative energy can be maximized.

[Regenerative coordination unit YK]
Coordinated control of friction braking and regenerative braking (referred to as “regenerative coordinated control”) is achieved by the regenerative coordination unit YK. For example, the regenerative coordination unit YK can create a state in which the brake operating member BP is operated but the brake hydraulic pressure Pw is not generated. The regenerative coordination unit YK consists of an input cylinder CN, an input piston PK, an input elastic body SN, a first on-off valve VA, a second on-off valve VB, a stroke simulator SS, a simulator hydraulic pressure sensor PS, and an input hydraulic pressure sensor PN. Configured.

The input cylinder CN is a bottomed cylinder member that is fixed to the master cylinder CM. The input piston PK is a piston member inserted inside the input cylinder CN. The input piston PK is mechanically connected to the brake operating member BP via a clevis (U-shaped link) so as to interlock with the brake operating member BP. The input piston PK is provided with a flange portion (flange) Tn. An input elastic body (for example, a compression spring) SN is provided between the mounting surface of the input cylinder CN to the master cylinder CM and the flange portion Tn of the input piston PK. The input elastic body SN presses the flange Tn of the input piston PK against the bottom of the input cylinder CN in the backward direction Hb of the central axis Jm.

When the brake is not applied, the stepped portion of the master piston PM abuts the large-diameter bottom portion of the master cylinder CM, and the flange portion Tn of the input piston PK abuts the bottom portion of the input cylinder CN. During non-braking, inside the input cylinder CN, the clearance Ks between the end surface Mq of the master piston PM and the end surface Mg of the input piston PK is set to a predetermined distance ks (referred to as "initial clearance"). That is, when the pistons PM and PK are at the position (referred to as the "initial position" of each piston) in the most backward direction Hb (the direction opposite to the forward direction Ha) (that is, when the brake is not applied), the master piston PM and the input piston PK is separated by a predetermined distance ks. Here, the predetermined distance ks corresponds to the maximum value of the regeneration amount Rg. When regenerative cooperative control is executed, the gap (also referred to as "separation displacement") Ks is controlled (adjusted) by the adjustment hydraulic pressure Pc.

When the braking operation member BP is stepped on from the state of "Ba=0", the input piston PK is moved from its initial position in the forward direction Ha (the direction in which the braking fluid pressure Pw increases). At this time, if the adjustment hydraulic pressure Pc remains "0", the master piston PM remains at the initial position. , gradually decreasing. On the other hand, when the adjustment hydraulic pressure Pc is increased from "0", the master piston PM is moved in the forward direction Ha from its initial position. Therefore, the clearance Ks can be adjusted independently of the braking operation amount Ba within the range of "0≦Ks≦ks" by the adjustment hydraulic pressure Pc. That is, by adjusting the adjustment hydraulic pressure Pc, the gap Ks between the input piston PK and the master piston PM is adjusted, and regenerative cooperative control is achieved.

The input chamber Rn of the regenerative cooperation unit YK and the reaction force chamber Ro of the master unit YM are connected by the simulator fluid path HS. A first on-off valve VA is provided in the simulator fluid path HS. The first on-off valve VA is a normally closed solenoid valve having an open position and a closed position. A third reservoir fluid path HT is connected to a portion Bs between the first on-off valve VA and the reaction force chamber Ro of the simulator fluid path HS. A second on-off valve VB is provided in the third reservoir fluid path HT. The second on-off valve VB is a normally open solenoid valve having an open position and a closed position. The first and second on-off valves VA and VB are two-position solenoid valves (on/off valves) having an open position (communication state) and a closed position (blockage state). The first and second on-off valves VA and VB are controlled by the upper controller ECU based on drive signals Va and Vb. When the braking control device SC is activated, energization of the first and second on-off valves VA and VB is started. Then, the first on-off valve VA is set to the open position, and the second on-off valve VB is set to the closed position.

A stroke simulator SS (simply referred to as a "simulator") is connected to the simulator fluid passage HS between the first on-off valve VA and the reaction force chamber Ro. In other words, the input chamber Rn of the regenerative cooperation unit YK is connected to the simulator SS by the simulator fluid path HS. During regenerative cooperative control, the first on-off valve VA is opened and the second on-off valve VB is closed. When the second on-off valve VB is in the closed position, the flow path to the reservoir RV is blocked in the third reservoir fluid path HT, so that the brake fluid BF is moved from the input chamber Rn of the input cylinder CN into the simulator SS. . Since a force is applied to the piston of the simulator SS by an elastic body to prevent the inflow of the brake fluid BF, an operation force Fp is generated when the brake operation member BP is operated.

A third reservoir fluid path HT is connected to the master reservoir RV. A portion of the third reservoir fluid passage HT can be shared with the first and second reservoir fluid passages HV and HU. However, it is desirable that the first and second reservoir fluid paths HV, HU and the third reservoir fluid path HT are separately connected to the reservoir RV. The fluid pump HP sucks the damping fluid BF from the reservoir RV through the first reservoir fluid passage HV. At this time, air bubbles may be mixed in the first reservoir fluid passage HV. Therefore, the third reservoir fluid passage HT is directly connected to the reservoir RV so as to prevent air bubbles from entering the input cylinder CN or the like.

A simulator hydraulic pressure sensor PS is provided in the simulator fluid passage HS between the first on-off valve VA and the reaction force chamber Ro so as to detect the hydraulic pressure (referred to as "simulator hydraulic pressure") Ps in the simulator SS. An input hydraulic pressure sensor PN is provided in the simulator fluid passage HS between the first on-off valve VA and the input chamber Rn to detect the hydraulic pressure (referred to as "input hydraulic pressure") Pn in the input chamber Rn. be done. The simulator hydraulic pressure sensor PS and the input hydraulic pressure sensor PN are one of the braking operation amount sensors BA described above. The detected hydraulic pressures Ps and Pn are input to the upper controller ECU as the braking operation amount Ba. Here, since "Ps=Pn" when the first and second on-off valves VA and VB are energized, either the simulator hydraulic pressure sensor PS or the input hydraulic pressure sensor PN One can be omitted.

[Upper controller ECU]
The upper controller ECU is composed of a microprocessor MP, an electric circuit board on which a drive circuit DR is mounted, and a control algorithm programmed in the microprocessor MP. The controller ECU is provided with a drive circuit DR to drive the solenoid valves VA, VB, UB, UC and the electric motor MT. A bridge circuit is formed in the drive circuit DR by switching elements (power semiconductor devices such as MOS-FETs and IGBTs) so as to drive the electric motor MT. Further, the drive circuit DR is provided with switching elements to drive the solenoid valves VA, VB, UB, and UC.

By the upper controller ECU, the electric motor MT and the solenoid valves VA, VB, UB, UC are controlled by the braking operation amount Ba (Sp, Fp, Ps, Pn), the vehicle body speed Vx, and the adjustment hydraulic pressure (detected value) Pb , Pc. Specifically, the upper controller ECU calculates drive signals Va, Vb, Ub, and Uc for controlling various electromagnetic valves VA, VB, UB, and UC. Similarly, a drive signal Mt for controlling the electric motor MT is calculated. Based on the drive signals Va, Vb, Ub, Uc and Mt, the energized state of each switching element is controlled to drive the solenoid valves VA, VB, UB and UC and the electric motor MT. Note that the master cylinder hydraulic pressure Pq may be employed instead of the second adjustment hydraulic pressure Pc.

The upper controller ECU is network-connected to other controllers (electronic control units) via an in-vehicle communication bus BS. From the controller ECU, the regeneration amount Rg is transmitted to the drive controller ECD so as to execute the regeneration cooperative control. The "regeneration amount Rg" is a state quantity (including Fg and Fx) representing the magnitude of the regenerative braking force generated by the driving motor GN. Also, the vehicle body speed Vx calculated by the lower controller ECL is transmitted to the upper controller ECU via the communication bus BS. Further, the required deceleration Gj is transmitted from the driving support controller ECJ to the upper controller ECU so that automatic braking control is executed. Here, "automatic braking control" automatically controls the vehicle based on the distance between the obstacle and the vehicle so as to avoid a collision with an obstacle (object) in front of the vehicle (or reduce damage in the event of a collision). It slows down to The required deceleration Gj is the target value of the vehicle deceleration for automatic braking control.

[Lower fluid unit YL]
The lower fluid unit YL is a known fluid unit including a master cylinder pressure sensor PQ, a plurality of solenoid valves, an electric pump and a low pressure reservoir. A master cylinder fluid passage HM is connected to the master cylinder CM. The master cylinder fluid passage HM branches into front wheel cylinder fluid passages HWi, HWj (=HWf) in the lower fluid unit YL, and is connected to the front wheel cylinders CWi, CWj (=CWf). Further, the first supply fluid passage HB is branched into rear wheel cylinder fluid passages HWk, HWl (=HWr) in the lower fluid unit YL and connected to the rear wheel cylinders CWk, CWl (=CWr).

The lower fluid unit YL is controlled by a lower controller ECL. Wheel speed Vw, yaw rate, steering angle, longitudinal acceleration, lateral acceleration, etc. are input to the lower controller ECL. The lower controller ECL calculates the vehicle body speed Vx based on the wheel speed Vw. Then, based on the vehicle body speed Vx and the wheel speed Vw, antiskid control is executed to suppress excessive deceleration slip (for example, wheel lock) of the wheels WH. Further, the lower controller ECL performs vehicle stabilization control (so-called ESC) for suppressing unstable vehicle behavior (excessive oversteer behavior and understeer behavior) based on the yaw rate. In other words, the lower hydraulic unit YL controls the braking fluid pressure Pw of each wheel WH individually. The calculated vehicle body speed Vx is input to the upper controller ECU through the communication bus BS.

[Operation of braking control device SC]
When a start switch (eg, ignition switch) of the vehicle is turned on, the first on-off valve VA is opened and the second on-off valve VB is closed. Therefore, while the vehicle is running, the input chamber Rn of the regenerative coordination unit YK and the reaction force chamber Ro of the master unit YM are in communication via the simulator fluid path HS and the first on-off valve VA. On the other hand, since the second on-off valve VB is in the closed position, the input chamber Rn and the reaction force chamber Ro are cut off from the master reservoir RV.

During non-braking (for example, when the braking operation member BP is not operated), the first and second pressure regulating valves UB and UC and the electric motor MT are not energized. At this time, the pistons PM and PK are pressed to their respective initial positions by the elastic bodies SM and SN, and the fluid pressure chamber Rm of the master cylinder CM and the reservoir RV are in communication. Therefore, the master cylinder hydraulic pressure Pq is "0 (atmospheric pressure)".

When the brake operation member BP is operated (especially when control braking is started), the input piston PK is moved in the forward direction Ha. At this time, the amount of the brake fluid BF flowing out from the input chamber Rn flows into the simulator SS, and the operating force Fp of the brake operating member BP is generated.

If the regenerative braking force from the generator GN is sufficient for decelerating the vehicle, the state of "Pc=0" is maintained. By operating the braking operation member BP, the input piston PK is moved from its initial position in the forward direction Ha, but at this time, the master piston PM is not moved because the adjustment hydraulic pressure Pc remains "0". . Therefore, as the input piston PK advances, the gap Ks (the distance between the end face Mm of the master piston PM and the end face Mn of the input piston PK) gradually decreases.

When the deceleration of the vehicle becomes insufficient with the regenerative braking force from the generator GN, the controller ECU controls the pressure regulating unit YC to adjust the regulated hydraulic pressure Pc. The adjustment hydraulic pressure Pc is applied to the servo chamber Rs through the second supply fluid passage HC. When the force (forward force) Fa in the forward direction Ha generated by the hydraulic pressure Pc in the servo chamber Rs becomes larger than the set load of the master elastic body SM, the master piston PM moves along the central axis Jm of the master cylinder CM. It is moved in the forward direction Ha. This movement in the forward direction Ha isolates the master chamber Rm from the reservoir RV.

Further, when the second adjustment hydraulic pressure Pc is increased, the brake fluid BF is pressure-fed from the master cylinder CM toward the front wheel cylinder CWf at the master hydraulic pressure Pq. A force (retreating force) Fb in the retreating direction Hb is acting on the master piston PM due to the master hydraulic pressure Pq. The servo chamber Rs generates a force (forward force) Fa in the forward direction Ha by the second adjustment hydraulic pressure Pc so as to oppose (oppose) this backward force Fb. The master hydraulic pressure Pq is increased or decreased according to the increase or decrease of the second adjustment hydraulic pressure Pc. As the second adjustment hydraulic pressure Pc increases, the master piston PM moves from the initial position in the forward direction Ha. It can be adjusted independently of Ba. That is, the cooperative regeneration control is executed by adjusting the clearance Ks by the adjustment hydraulic pressure Pc. The first adjustment hydraulic pressure Pb is applied directly to the rear wheel cylinder CWr through the first supply fluid passage HB and the lower fluid unit YL.

When the brake operating member BP is returned, the adjustment hydraulic pressure Pc is decreased. Then, when the adjusted hydraulic pressure Pc becomes smaller than the master cylinder hydraulic pressure Pq, the master piston PM is moved in the backward direction Hb. When the brake operation member BP is put into a non-operated state, the elastic force of the compression spring SM returns the master piston PM to a position (initial position) where it contacts the second bottom portion of the master cylinder CM.

It should be noted that during manual braking (during power failure, etc.), the first and second on-off valves VA and VB are not energized. Therefore, the first opening/closing valve VA is closed and the second opening/closing valve VB is opened. The closed position of the first on-off valve VA puts the input chamber Rn in a fluid-locked state (sealed state) so that the input piston PK and the master piston PM cannot move relative to each other. Further, the reaction force chamber Ro is connected to the reservoir RV through the second reservoir fluid passage HT by the open position of the second on-off valve VB. Therefore, although the volume Vo of the reaction force chamber Ro is reduced by the movement of the master piston PM in the forward direction Ha, the amount of fluid accompanying the reduction in volume is discharged toward the reservoir RV. In conjunction with the operation of the brake operation member BP, the input piston PK and the master piston PM are moved together, and the brake fluid BF is pressure-fed from the master chamber Rm to the front wheel cylinder CWf.

As described above, the vehicle has a brake-by-brake system in which the operation of the brake operation member BP and the adjustment of the brake hydraulic pressure Pw are independent of each other so as to achieve cooperative regenerative control (cooperative friction braking and regenerative braking).・Equipped with a wire-type braking control device SC. Accordingly, the operating force Fp of the brake operating member BP is generated by the simulator SS, and the hydraulic pressure Pw of the wheel cylinder CW is adjusted by the pressure regulating unit YC.

<Pressure regulation control process>
An example of pressure regulation control processing will be described with reference to the flowchart of FIG. 2 . "Pressure adjustment control" is drive control of the electric motor MT and the solenoid valves VA, VB, UB, UC for adjusting the first and second adjustment hydraulic pressures Pb, Pc. The control algorithm is programmed into the upper controller ECU.

At step S110, initialization of the braking control device SC is performed. In step S110, an initial diagnosis of each component is performed. Next, in step S120, the normally closed first on-off valve VA and the normally open second on-off valve VB are energized. That is, when the start switch of the device is turned on, the first on-off valve VA is opened and the second on-off valve VB is closed. The on/off states of the first and second on-off valves VA and VB are not switched for each braking operation, but the first and second on-off valves VA and VB are always energized while the vehicle is running. will be This is advantageous in terms of operation noise and stabilizes the characteristics of the simulator SS.

At step S130, various signals are read. Specifically, the operation amount Ba, the required deceleration Gj, the first and second adjustment hydraulic pressures (detected values) Pb and Pc, and the vehicle body speed Vx are read. The manipulated variable Ba is detected by a manipulated variable sensor BA (manipulation displacement sensor SP, input hydraulic pressure sensor PN, simulator hydraulic pressure sensor PS, etc.). The regulating hydraulic pressures Pb, Pc (or master cylinder hydraulic pressure Pq) are detected by regulating hydraulic pressure sensors PB, PC (or master cylinder hydraulic pressure sensor PQ) provided in the regulating fluid passage HA. The vehicle body speed Vx is acquired from the lower controller ECL via the communication bus BS. The wheel speed Vw may be input to the upper controller ECU, and the vehicle body speed Vx may be calculated by the upper controller ECU based on the wheel speed Vw.

At step S140, "whether braking is being performed or not" is determined based on the operation amount Ba of the braking operation member BP. For example, when the operation amount Ba is larger than the predetermined value bo, step S140 is affirmative, and the process proceeds to step S150. On the other hand, if the operation amount Ba is equal to or less than the predetermined value bo, step S140 is denied, and the process returns to step S130. Here, the predetermined value bo is a preset constant corresponding to the play of the braking operation member BP.

Further, during automatic braking control (during execution of control for avoiding a collision with an obstacle in front of the vehicle), in step S140, based on the required deceleration Gj, "whether or not braking is being performed" is determined. be judged. If the required deceleration Gj is greater than the predetermined deceleration go, affirmative determination is made in step S140, and the process proceeds to step S150. On the other hand, if the requested deceleration Gj is less than or equal to the predetermined deceleration go, the decision in step S140 is negative, and the process returns to step S130. Here, the predetermined deceleration go is a preset constant for determination.

At step S150, a sudden braking index Kb is calculated. The sudden braking index Kb is a state quantity representing the degree of sudden braking required to decelerate the vehicle. For example, as the sudden braking index Kb, the operation amount Ba is time-differentiated and calculated, and the operation speed dB is employed. The operation amount Ba is a state quantity representing the degree of operation of the brake operation member BP, and is determined based on at least one of the operation displacement Sp, the operation force Fp, the input hydraulic pressure Pn, and the simulator hydraulic pressure Ps. be. In particular, it is preferable to use the operation speed dS (differential value of the operation displacement Sp) calculated based on the operation displacement Sp as the sudden braking index Kb. Dynamically, the operation of the brake operation member BP is propagated in the order of "Sp→Pn→Ps", so the operation displacement Sp is the state quantity closest to the input of the brake operation member BP, and temporally It is based on being an early detected state quantity.

Further, in step S150, a sudden braking index Kb (a state quantity representing the degree of sudden braking demand) can be calculated based on the required deceleration Gj. The required deceleration Gj is an instruction value (target value) in automatic braking control, and is time-differentiated to calculate a deceleration differential value dG. Then, the deceleration differential value dG is determined as the sudden braking index Kb.

At step S160, it is determined whether or not the sudden braking process is being performed based on the control flag FL. The sudden braking process is a control process for the first and second pressure regulating valves UB and UC for quickly generating front wheel braking force, which plays an important role in decelerating the vehicle. The control flag FL expresses execution of the sudden braking process. If the flag FL is "0", it indicates that the sudden braking process is not being executed, and if the flag FL is "1", it indicates that the sudden braking process is being executed. If "FL=0 (when not executed)" and step S160 is negative, the process proceeds to step S170. If "FL=1 (during execution)" and step S160 is affirmative, the process proceeds to step S180.

At step S170, "whether or not to start the sudden braking process" is determined based on the sudden braking index Kb. For example, the determination to start the sudden braking process is affirmative when both of the following two conditions (A1, A2) are satisfied.
Condition A1: The sudden braking index Kb is greater than or equal to the first predetermined value kx. The first predetermined value kx is a predetermined determination constant (predetermined value).
Condition A2: "The manipulated variable Ba is greater than or equal to the predetermined amount bx" or "The required deceleration Gj is greater than or equal to the predetermined deceleration gx". The predetermined amount bx and the predetermined deceleration gx are preset constants (predetermined values).

If "Kb≧kx and Ba≧bx" or "Kb≧kx and Gj≧gx", step S170 is affirmative, and the process proceeds to step S200. In step S200, a rapid braking process is executed to increase the front wheel braking fluid pressure Pwf with high response. On the other hand, if any one of "Kb<kx", "Ba<bx", and "Gj<gx" is satisfied, step S170 is negative, and the process proceeds to step S190. At this time, the flag FL remains at "0". In step S190, the sudden braking process is not executed, but the normal pressure regulation control process (simply referred to as "normal process") is executed.

When the determination in step S170 is affirmative (corresponding calculation cycle), control flag FL is switched from "0" to "1". In addition, the time (continuation time) Tz during which the sudden braking process continues from the time when the determination in step S170 is affirmative is calculated. A timer is activated and the elapsed time Tz is sequentially accumulated in the calculation cycle in which the start of the sudden braking process is determined.

At step S180, it is determined whether or not to end the sudden braking process. The sudden braking process is terminated when at least one of the following three conditions (B1 to B3) is satisfied.
Condition B1: The elapsed time Tz has become equal to or longer than the predetermined time tz. The predetermined time tz is a preset constant (predetermined value).
Condition B2: The sudden braking index Kb (differential value dB of the manipulated variable Ba, differential value dG of the required deceleration Gj) has decreased, and the sudden braking index Kb has become less than the second predetermined value ky. Here, the second predetermined value ky is a preset constant smaller than the first predetermined value kx (that is, "ky<kx").
Condition B3: Braking is terminated. That is, "Ba=0" or "Gj=0" has been achieved.

If step S180 is affirmative, the process proceeds to step S190, and normal processing (normal pressure regulation processing) is executed. At this time, the control flag FL is switched from "1" to "0". On the other hand, if step S180 is negative, the process proceeds to step S200, and a sudden braking process (pressure regulation process for improving responsiveness) is executed. At this time, the flag FL remains at "1". Details of the normal process and the sudden braking process will be described below.

<Normal processing of pressure regulation control>
With reference to the flowchart of FIG. 3, normal pressure regulation control processing including regenerative cooperative control (processing when sudden braking processing is not executed) will be described.

At step S210, as shown in block X210, the required braking force Fu is calculated based on the manipulated variable Ba. The braking force Fu requested by the driver is a target value of the total braking force F acting on the vehicle according to the operation amount Ba. is the braking force combined with The required braking force Fu is determined to be "0" when the operation amount Ba is in the range from "0" to a predetermined value bo according to the calculation map Zfu, and when the operation amount Ba is equal to or greater than the predetermined value bo, the operation amount Ba increases. Accordingly, calculation is performed so as to monotonically increase from "0".

Further, during automatic braking control, in step S210, the requested deceleration Gj for the automatic braking control is converted into the dimension of the braking force, and the requested braking force Fj for the automatic braking control is calculated. Then, the larger one of the required braking force Fu (requested value by the driver) based on the operation amount Ba and the required braking force Fj (required value by automatic braking control) based on the required deceleration Gj is the final request. It is determined as the braking force Fd.

In step S220, the maximum value of regenerative braking force (referred to as "maximum regenerative force") Fx is calculated based on the vehicle body speed Vx and the calculation map Zfx using the characteristics shown in block X220. The calculation map Zfx for the maximum regenerative force Fx is set so that the maximum regenerative force Fx increases as the vehicle speed Vx increases in the range where the vehicle speed Vx is greater than or equal to "0" and less than the first predetermined speed vo. . Further, the maximum regenerative force Fx is determined to be the upper limit value fx when the vehicle body speed Vx is in the range of the first predetermined speed vo or more and less than the second predetermined speed vp. When the vehicle body speed Vx is equal to or higher than the second predetermined speed vp, the maximum regenerative force Fx is set to decrease as the vehicle body speed Vx increases. For example, in the decreasing characteristic of the maximum regenerative force Fx (characteristic of "Vx≧vp"), the relationship between the vehicle body speed Vx and the maximum regenerative force Fx is represented by a hyperbola (that is, the regenerative power is constant). Here, each predetermined value vo, vp is a preset constant. Note that in the calculation map Zfx, the rotation speed Ng of the generator GN can be used instead of the vehicle body speed Vx.

The amount of regeneration of the generator GN is limited by the rating of the power transistors (IGBT, etc.) of the drive controller ECD and the charge acceptance of the battery. When the electric power (work rate) is constant, the regenerative torque around the wheel shaft by the generator GN is inversely proportional to the rotation speed of the wheels WH (that is, the vehicle body speed Vx). Also, when the rotation speed Ng of the generator GN decreases, the regeneration amount decreases. The characteristics of the calculation map Zfx are set so that the regeneration amount of the generator GN is limited to a predetermined power (electric energy per unit time).

In step S230, the distribution ratio of the braking force (in particular, the ratio of the rear wheel braking force to the total braking force F, referred to as "rear wheel ratio Hr") is set. For example, the rear wheel ratio Hr is preset. is determined as a constant (predetermined value) hr. Also, the rear wheel ratio Hr may be determined based on at least one of the turning state quantity Ta, the vehicle body speed Vx, and the required braking force Fd. Here, the turning state quantity Ta is a variable representing the turning state of the vehicle, and corresponds to, for example, yaw rate and lateral acceleration.

In step S240, based on the required braking force Fd (the larger one of the required braking force Fu and the required braking force Fj) and the maximum regenerative force Fx, "When the required braking force Fd is equal to or less than the maximum regenerative force Fx, Yes or No" is determined. That is, it is determined whether or not the requested braking force Fd can be achieved only by the regenerative braking force Fg. If "Fd≦Fx" and the determination in step S240 is affirmative, the process proceeds to step S250. On the other hand, when "Fd>Fx" and step S240 is negative, the process proceeds to step S260.

In step S250, the regenerative braking force (target value) Fg and the front and rear wheel friction braking forces (target values) Fmf and Fmr are calculated based on the required braking force Fd. Specifically, the target regenerative braking force Fg is determined to match the required braking force Fd, and the front and rear wheel target frictional braking forces Fmf and Fmr are calculated to be "0" (that is, "Fg=Fd , Fmf=Fmr=0"). That is, when the regenerative braking force Fg does not reach the maximum regenerative force Fx (when "Fg<Fx"), friction braking is not adopted for vehicle deceleration, and only regenerative braking is used to achieve the required braking force Fd. is achieved.

In step S260, target regenerative braking force Fg, rear wheel reference force Fs, and complementary braking force Fh are calculated. First, the regenerative braking force Fg is calculated so as to match the maximum regenerative force Fx. That is, when the regenerative braking force Fg reaches the maximum regenerative force Fx (when "Fg≧Fx"), "Fg=Fx" is calculated to maximize the regenerative energy. Next, the rear wheel reference force Fs is calculated based on the required braking force Fd and the rear wheel ratio Hr. The rear wheel reference force Fs is a value obtained by considering the front/rear ratio of the braking force to the required braking force Fd (that is, the rear wheel ratio Hr), and is used as a reference for achieving the rear wheel ratio Hr. Specifically, the rear wheel reference force Fs is calculated by multiplying the required braking force Fd by the rear wheel ratio Hr (that is, "Fs=Hr×Fd"). Then, the complementary braking force Fh is calculated based on the required braking force Fd and the maximum regenerative force Fx. The complementary braking force Fh is a braking force that should be supplemented by friction braking in order to achieve the required braking force Fd. Specifically, the maximum regenerative force Fx is subtracted from the required braking force Fd to calculate the complementary braking force Fh (that is, "Fh=Fd-Fx").

In step S270, the complementary braking force Fh and the rear wheel reference force Fs are compared to determine whether or not the complementary braking force Fh is equal to or less than the rear wheel reference force Fs. If "Fh≦Fs" and the result in step S270 is affirmative, the process proceeds to step S280. On the other hand, if "Fh>Fs" and step S270 is negative, the process proceeds to step S290.

In step S280, the front wheel frictional braking force Fmf is determined to be "0", and the rear wheel frictional braking force Fmr is calculated so as to match the complementary braking force Fh (that is, "Fmf=0, Fmr=Fh"). . When the complementary braking force Fh is equal to or less than the rear wheel reference force Fs, the front wheel WHf does not generate the front wheel frictional braking force Fmf, and only the regenerative braking force Fg is applied. A frictional braking force Fmr is generated at the rear wheel WHr so that the required braking force Fd is satisfied.

On the other hand, in step S290, the rear wheel frictional braking force Fmr is calculated so as to match the rear wheel reference force Fs, and the front wheel frictional braking force Fmf is obtained by subtracting the rear wheel reference force Fs from the complementary braking force Fh (" It is calculated to match Fc (referred to as "front wheel steering force") (that is, "Fmf=Fc=Fh-Fs, Fmr=Fs"). When the complementary braking force Fh is larger than the rear wheel reference force Fs, the rear wheel frictional braking force Fmr is set to the rear wheel reference force Fs considering the rear wheel ratio Hr, and is insufficient for the required braking force Fd. The minute (=Fc) is determined as the front wheel frictional braking force Fmf.

At step S300, the regeneration amount Rg is calculated based on the regenerative braking force Fg. The regeneration amount Rg is a target value for the regeneration amount of the generator GN. The regeneration amount Rg is transmitted from the upper controller ECU to the drive controller ECD via the communication bus BS.

In step S310, the target hydraulic pressure Pt (=Ptf, Ptr) is calculated based on the target value Fm (=Fmf, Fmr) of the frictional braking force. That is, the target hydraulic pressure Pt is determined by converting the frictional braking force Fm into the dimension of the hydraulic pressure. The rear wheel target hydraulic pressure Ptr is a target value of the hydraulic pressure of the rear wheel cylinder CWr corresponding to the first adjustment hydraulic pressure Pb. The front wheel target hydraulic pressure Ptf is a target value of the hydraulic pressure of the front wheel cylinder CWf corresponding to the second adjustment hydraulic pressure Pc.

In step S320, the electric motor MT is controlled based on the front wheel target hydraulic pressure Ptf and the rear wheel target hydraulic pressure Ptr. For example, the target hydraulic pressure Pt (=Ptf, Ptr) is time-differentiated to calculate the hydraulic pressure change amount dP (=dPf, dPr). A target flow rate Qt required for the electric pump DN is calculated based on the target hydraulic pressure Pt and the hydraulic pressure change amount dP. Then, the target rotation speed Nt of the electric motor MT is determined based on the target flow rate Qt, and rotation speed feedback control is performed so that the actual rotation speed Na approaches and matches the target rotation speed Nt.

Since the hydraulic pressure change amount dP is taken into account in calculating the target rotational speed Nt, the electric pump DN is driven at the minimum rotational speed required for hydraulic pressure adjustment. Since the pressure regulating unit YC is provided with a check valve GC, when the first and second pressure regulating valves UB and UC are completely closed, the first and second regulating hydraulic pressures Pb and Pc (actual values) is kept constant. Further, the first and second regulating hydraulic pressures Pb and Pc can be reduced by opening the pressure regulating valves UB and UC. Therefore, when "dPf≤0 and dPr≤0" (for example, when the braking operation member BP is held or returned), the target flow rate Qt is determined to be "0". Then, the rotation of the electric pump DN (=MT) can be stopped (that is, "Nt=0"). The electric motor MT is stopped when the braking operation member BP is held or returned, thereby saving power.

Further, in step S320, the first pressure regulating valve UB and the second pressure regulating valve UC are controlled based on the front wheel target hydraulic pressure Ptf and the rear wheel target hydraulic pressure Ptr. For example, based on the front and rear wheel target hydraulic pressures Ptf, Ptr and the detection values Pc, Pb of the first and second adjustment hydraulic pressure sensors, the actual first and second adjustment hydraulic pressures Pc, Pb , the rear wheel target hydraulic pressures Ptf and Ptr, and the hydraulic pressure feedback control is executed so that the target hydraulic pressures Ptf and Ptr are approached and matched.

As described above, in the braking control device SC, the first adjustment hydraulic pressure Pb and the second adjustment hydraulic pressure Pc are adjusted independently and separately within the range of "Pb≧Pc". During normal processing of pressure regulation control, regenerative cooperative control is executed after consideration is given to the front-rear distribution of the braking force. Specifically, as the operation amount Ba (or the required deceleration Gj) increases, "only the regenerative braking force Fg of the front wheels WHf by the generator GN" → "(regenerative braking force Fg of the front wheels WHf) + (first adjustment liquid Friction braking force Fmr of rear wheel WHr due to pressure Pb) → (regenerative braking force Fg of front wheel WHf) + (friction braking force Fmf of front wheel WHf due to second adjustment hydraulic pressure Pc) + (friction braking force of rear wheel WHr Fmr)”, the generation state of the braking force is transitioned. As a result, in a vehicle equipped with a regenerative generator GN for the front wheels WHf, a sufficient amount of regenerative energy is ensured, and braking force is properly distributed between the front and rear wheels, thereby ensuring deceleration and stability of the vehicle. .

<Sudden braking process of pressure regulation control>
The sudden braking process of pressure regulation control corresponding to the first embodiment will be described with reference to the flowchart of FIG. The sudden braking process is executed when the braking operation member BP is suddenly operated, there is a high possibility of collision with an obstacle, and sudden braking is requested in the automatic braking control.

At step S410, the target hydraulic pressure Pt is calculated based on the required braking force Fd. Here, the required braking force Fd is the larger one of the required braking force Fu calculated based on the operation amount Ba and the required braking force Fj calculated based on the required deceleration Gj. . Since the specifications of the braking device (the pressure receiving areas of the master cylinder CM and the wheel cylinder CW, the effective braking radius of the rotary member KT, the friction coefficient of the friction material, etc.) are known, the required braking force Fd is calculated based on the specifications. It is converted into the target hydraulic pressure Pt. It should be noted that during the sudden braking process, the regenerative cooperative control is not executed, and the regenerative braking force Fg is set to "0".

At step S420, the electric motor MT is driven at its maximum output. That is, the maximum current that can flow through the switching element of the drive circuit DR. At step S430, the first pressure regulating valve UB is driven to the fully open state. That is, even if the rear wheel target hydraulic pressure Ptr is calculated to be a certain value, the normally open first pressure regulating valve UB is not energized. In step S440, the normally open second pressure regulating valve UC is fully energized and driven to the fully closed state.

In vehicle deceleration, the contribution of the braking force Ff of the front wheels WHf is much higher than the contribution of the braking force Fr of the rear wheels WHr. This is because the load (vertical force) on the front wheels WHf increases and the load on the rear wheels WHr decreases due to deceleration of the vehicle. Also, if the braking force Fr of the rear wheels WHr becomes excessive, the directional stability of the vehicle is likely to be impaired. It is set larger than the pressure receiving area of the rear wheel cylinder CWr. Therefore, the amount of fluid consumed by the front wheel cylinder CWf is relatively large. Here, the "fluid consumption" is the volume of the brake fluid BF consumed by the stiffness (deformation) of members such as calipers, hydraulic pipes (fluid passages), and friction members arranged around the wheels. In order to rapidly increase the braking fluid pressure Pwf of the front wheel cylinder CWf, first, the amount of the braking fluid BF corresponding to the amount of fluid consumed by the front wheel cylinder CWf is supplied, and then the braking fluid BF is further supplied. starts to increase the front wheel braking hydraulic pressure Pwf.

In the brake control device SC, a plurality of pressure regulating valves UB and UC are arranged in series in the return path (A) of the brake fluid BF, and the brake fluid pressures Pwf and Pwr of the front and rear wheels are individually adjusted by these valves. Then, in the sudden braking process that is executed when sudden braking is determined, the electric motor MT is driven at its maximum output, and the brake fluid BF is supplied at the maximum dischargeable flow rate of the electric pump DN. Since the second pressure regulating valve UC is fully closed, the entire amount of the brake fluid BF discharged by the fluid pump HP is supplied to the servo chamber Rs or the rear wheel cylinder CWr. Furthermore, since the first pressure regulating valve UB is fully open, the servo chamber Rs is supplied with as much braking fluid BF as possible. In other words, since the second pressure regulating valve UC is fully closed, the entire amount of the brake fluid BF discharged by the fluid pump HP is used for regulating the front and rear wheel hydraulic pressures Pwf and Pwr. In addition, since the first pressure regulating valve UB is fully opened, the maximum possible amount of brake fluid BF is supplied to regulate the front wheel hydraulic pressure Pwf. When the vehicle needs to be braked suddenly, the front wheel hydraulic pressure Pwf (resulting in the front wheel braking force Ff) is efficiently increased to quickly decelerate the vehicle.

In the process of step S410, "Fg=0" was determined and regenerative cooperative control was prohibited, but regenerative braking by generator GN may be performed. Even in this case, the electric motor MT is driven at maximum output, the first pressure regulating valve UB remains fully open, and the second pressure regulating valve UC is driven to a fully closed state. The sudden braking process can improve the responsiveness of the front wheel brake fluid pressure Pwf to increase, thereby achieving rapid deceleration of the vehicle.

<Second Embodiment of Brake Control Device SC>
A second embodiment of the braking control device SC according to the present invention will be described with reference to the overall configuration diagram of FIG. Also in the second embodiment, a front-rear type is adopted as the two-system fluid passage. As above, components, operations, signals, characteristics, and values labeled with the same symbols have the same function. The suffixes “i” to “l” attached to the end of the symbol relating to each wheel are generic symbols indicating which wheel it relates to. Specifically, "i" indicates the right front wheel, "j" indicates the left front wheel, "k" indicates the right rear wheel, and "l" indicates the left rear wheel. The subscripts “i” to “l” at the end of the symbol can be omitted. In this case, each symbol represents a generic name for each of the four wheels. The suffixes "f" and "r" attached to the end of the symbols relating to the front and rear type braking systems are generic symbols indicating which system of the front and rear wheels it relates to, and "f" indicates the front wheel system. , “r” indicates the rear wheel system. The suffixes “f” and “r” at the end of the symbols can be omitted. In this case, each symbol represents a generic term for each of the two braking systems. Further, in the fluid path, the side farther from the wheel cylinder CW is called "upper", and the side closer to the wheel cylinder CW is called "lower". In the return path (A), the side closer to the discharge part of the fluid pump HP is called the "upstream side", and the side farther from it is called the "downstream side".

In the first embodiment, in a vehicle equipped with a generator GN for the front wheels WHf, the first regulating hydraulic pressure Pb is introduced into the rear wheel cylinder CWr via the first supply fluid passage HB, and the second regulating hydraulic pressure Pc (≦Pb) was supplied to the servo chamber Rs via the second supply fluid passage HC. The second embodiment is applied to a vehicle having generators GN on rear wheels WHr. Therefore, the first regulating hydraulic pressure (first hydraulic pressure) Pb (≧Pc) is supplied to the first supply fluid passage HB (the fluid passage branched from the pressure regulating fluid passage HA at the upstream side portion Bn of the first pressure regulating valve UB). ) to the servo chamber Rs. Further, the second regulating hydraulic pressure (second hydraulic pressure) Pc is supplied via the second supply fluid passage HC (the fluid passage branched from the pressure regulating fluid passage HA at the downstream side Bo of the first pressure regulating valve UB). , to the rear wheel cylinder CWr.

During the normal process of pressure regulation control, the rear wheel hydraulic pressure Pwr and the front wheel hydraulic pressure Pwf are individually adjusted by the first and second adjustment hydraulic pressures Pb and Pc. Specifically, as the operation amount Ba (or the required deceleration Gj) increases, "only the regenerative braking force Fg of the rear wheels WHr by the generator GN" → "(frictional braking force of the front wheels WHf by the first adjustment hydraulic pressure Pb Fmf) + (regenerative braking force Fg of rear wheel WHr) → (friction braking force Fmf of front wheel WHf by second adjustment hydraulic pressure Pc) + (regenerative braking force Fg of rear wheel WHr) + (friction of rear wheel WHr The braking force generation state is changed in the order of braking force Fmr). As a result, in the vehicle equipped with the generator GN in the rear wheel WHr, sufficient regenerative energy is ensured, and braking force is properly distributed between the front and rear wheels, thereby ensuring deceleration and stability of the vehicle.

<Sudden braking process of pressure regulation control>
With reference to the flow chart of FIG. 6, the sudden braking process of the pressure regulation control corresponding to the second embodiment will be described. The sudden braking process corresponding to the second embodiment is also executed when the braking operation member BP is suddenly operated, or when there is a high probability that the vehicle will collide with an obstacle and the automatic braking control is required to brake quickly.

At step S510, the target hydraulic pressure Pt is calculated based on the required braking force Fd (the larger one of the required braking force Fu and the required braking force Fj). The required braking force Fd is converted into the target hydraulic pressure Pt based on the specifications of the braking device. During the sudden braking process, regenerative cooperative control is not executed, and "Fg=0" is set.

At step S520, the electric motor MT is driven at maximum output. At step S530, the first pressure regulating valve UB is driven to the fully closed state. That is, the normally open first pressure regulating valve UB is fully energized and driven to the fully closed state. As a result, the brake fluid BF does not flow downstream to the first pressure regulating valve UB. Therefore, in step S540, the normally open second pressure regulating valve UC is not energized and is fully opened.

Similarly to the above, the contribution of the front wheel braking force Ff to vehicle deceleration is significantly greater than the contribution of the rear wheel braking force Fr. First, in the sudden braking process (pressure regulation control process executed when sudden braking is determined), the electric motor MT is driven at maximum output, and the brake fluid BF is discharged from the electric pump DN at the maximum flow rate. Since the first pressure regulating valve UB is driven to the fully closed state, the entire amount of the braking fluid BF discharged by the fluid pump HP is supplied to the servo chamber Rs. That is, the discharged braking fluid BF is not supplied to the rear wheel cylinder CWr, and the entire amount of the braking fluid BF discharged by the fluid pump HP is used to regulate the front wheel hydraulic pressure Pwf. Even in a vehicle in which the generator GN is provided for the rear wheels WHr, the rapid braking process efficiently increases the braking fluid pressure Pwf of the front wheels WHf (resulting in the front wheel braking force Ff), thereby achieving rapid vehicle deceleration.

As in step S410, regenerative braking by generator GN may also be performed in step S510. Even in this case, the electric motor MT is driven at maximum output, and the first pressure regulating valve UB is driven to the fully closed state. Since all of the brake fluid BF from the electric pump DN is supplied to the servo chamber Rs, the front wheel brake fluid pressure Pwf can be improved in boosting responsiveness, and rapid deceleration of the vehicle can be efficiently achieved.

When the maximum differential pressure of the first pressure regulating valve UB is set low, even if the first pressure regulating valve UB is closed (fully closed drive), the first pressure regulating valve UB is relieved (automatically valve opening) may occur. In order to avoid this situation, as shown in parentheses in step S540, in addition to the first pressure regulating valve UB, the second pressure regulating valve UC is also closed (fully closed). Here, the "maximum differential pressure" is the hydraulic pressure difference between the first hydraulic pressure Pb and the second hydraulic pressure Pc that can be achieved by the first pressure regulating valve UB. Even if the first hydraulic pressure Pb exceeds the maximum differential pressure of the first pressure regulating valve UB, since the second pressure regulating valve UC is in the fully closed state, the braking fluid BF from the electric pump DN is effectively servoed. It is supplied to the chamber Rs, and as a result, the same effect as described above is achieved.

SC: braking control device, BP: braking operation member, CM: master cylinder, CW: wheel cylinder, YC: pressure regulating unit, DN: electric pump, MT: electric motor, HP: fluid pump, UB: first pressure regulating valve, UC...second pressure regulating valve, ECU...controller, BA...operation amount sensor, PB...first regulating hydraulic pressure sensor, PC...second regulating hydraulic pressure sensor, GN...regenerative generator.

Claims (3)

A braking control device for a vehicle having a regenerative generator on the front wheels of the vehicle,
A second brake is provided in a brake fluid return path including an electric pump, adjusts the brake fluid discharged by the electric pump to a first hydraulic pressure, and adjusts the rear wheel hydraulic pressure of the rear wheel cylinder by the first hydraulic pressure. 1 pressure regulating valve;
a second pressure regulating valve provided in the return passage for reducing the first hydraulic pressure to a second hydraulic pressure and adjusting the front wheel hydraulic pressure of the front wheel cylinder by the second hydraulic pressure;
a controller that controls the electric pump and the first and second pressure regulating valves;
with
The controller is
determining sudden braking based on at least one of an operation amount of a braking operation member of the vehicle and a requested deceleration corresponding to a distance between an object in front of the vehicle and the vehicle;
A braking control device for a vehicle, wherein the first pressure regulating valve is fully opened and the second pressure regulating valve is fully closed when the sudden braking is determined. A braking control device for a vehicle having a regenerative generator on the rear wheels of the vehicle,
A first regulator is provided in a brake fluid return path including an electric pump, adjusts the brake fluid discharged by the electric pump to a first hydraulic pressure, and adjusts the front wheel hydraulic pressure of the front wheel cylinder by the first hydraulic pressure. a pressure valve;
a second pressure regulating valve provided in the return passage for reducing the first hydraulic pressure to a second hydraulic pressure and adjusting the rear wheel hydraulic pressure of the rear wheel cylinder by the second hydraulic pressure;
a controller that controls the electric pump and the first and second pressure regulating valves;
with
The controller is
determining sudden braking based on at least one of an operation amount of a braking operation member of the vehicle and a requested deceleration corresponding to a distance between an object in front of the vehicle and the vehicle;
A braking control device for a vehicle, wherein the first pressure regulating valve is fully closed when the sudden braking is determined. In the vehicle braking control device according to claim 2,
The controller is
A braking control device for a vehicle, wherein the second pressure regulating valve is fully closed when the sudden braking is determined.

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