JP7259335B2 - vehicle automatic braking system - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to an automatic braking device for a vehicle.

Patent Document 1 describes a technique for "optimizing the braking force distribution of the wheels and securing the maximum braking force when there is a possibility of collision with an obstacle". a determination unit for determining whether or not there is a possibility of collision with an object; and when the determination unit determines that there is a possibility of collision, the brake fluid pressure acting on each wheel is increased to move the wheel. and an automatic braking control unit that performs automatic braking control for braking, and a braking force distribution control unit that controls the braking force distribution of the wheels by holding the brake fluid pressure. , the braking force distribution control unit, when it is determined that there is a possibility of a collision by the determination unit, compares the brake fluid when it is determined that there is no possibility of a collision by the determination unit The braking force distribution control unit controls the distribution of the braking force so as to maintain the pressure at a large value. The braking force distribution is controlled so as to maintain the rear wheel brake fluid pressure at a higher value than when it is determined that there is no

In Patent Document 2, for the purpose of "improving the posture stability of the vehicle during automatic brake control," "automatic brake that automatically generates braking force on the wheels of the vehicle without depending on the brake operation of the driver. A brake device that performs control, comprising: first and second brake hydraulic pressure circuits for transmitting hydraulic pressure from a master cylinder to respective wheel cylinders of left and right front wheels; a brake actuator that can individually adjust the hydraulic pressure supplied to the brake actuator, a brake control unit that individually controls the braking force of each of the front wheels by controlling the brake actuator, and a behavior in the yaw direction of the vehicle that detects and a behavior detection sensor, and the brake actuator has a pump that pressurizes the hydraulic pressure of each of the brake hydraulic circuits during automatic brake control, and a pressure regulating valve that individually adjusts the hydraulic pressure of each of the brake hydraulic circuits. During automatic brake control, the brake control unit increases the hydraulic pressure supplied to the wheel cylinder of the front wheel having a lower braking force based on the behavior in the yaw direction detected by the behavior detection sensor. to control the pressure regulating valve."

In the device disclosed in Patent Document 1, it is determined whether or not there is a possibility that the own vehicle will collide with an obstacle. By comparison, the braking force is distributed such that the rear wheel brake fluid pressure is maintained at a large value. That is, the front-to-rear distribution of the braking force is shifted toward the rear wheels, and the rear wheel braking force is increased.

By the way, in wheels (tires), there is a trade-off relationship between the braking force and the lateral force. When the rear wheel braking force is increased as in the device of Patent Document 1, the generation of rear wheel lateral force is reduced when the vehicle is deflected and a side slip angle is generated in the rear wheels. That is, the lateral force of the rear wheels generates a yaw moment (also referred to as a "stabilizing moment") in the direction of suppressing vehicle deflection, but the amount of yaw moment generated is small, making it difficult to converge the deflection of the vehicle.

As in the device of Patent Document 2, in a vehicle in which a diagonal type (also referred to as "X type") is adopted as a two-system brake hydraulic circuit (braking system), due to variations in accuracy of the pressure regulating valve, etc., the pressure of the left and right front wheels Differences in braking force may occur and vehicle deflection may occur. In order to suppress this vehicle deflection, the device of Patent Document 2 adjusts the hydraulic pressure supplied to the wheel cylinder with the lower braking force to be increased based on the behavior in the yaw direction during automatic braking control. A pressure valve is controlled. However, in the device of Patent Document 2, since the hydraulic pressure adjustment is started after the yaw behavior actually occurs, the driver may feel uncomfortable with the change in the yaw behavior of the vehicle that occurs at this time. .

For the reasons described above, an automatic braking device that executes automatic braking control is desired to suitably suppress vehicle deflection without causing discomfort to the driver.

JP 2018-062273 JP 2017-149378

SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic braking device for a vehicle having a diagonal braking system, which can reduce discomfort to the driver and satisfactorily suppress vehicle deflection.

An automatic braking device for a vehicle is applied to a vehicle that adopts a diagonal system as two braking systems. The automatic braking device adjusts the hydraulic pressure (Pw) of the wheel cylinder (CW) to the master cylinder (CM) based on the required deceleration (Gs) corresponding to the distance (Ob) between the vehicle and an object in front of the vehicle. The first braking system connected to the right front wheel and left rear wheel cylinders (CWi, CWl) of the two braking systems. A first pressure regulating valve (UP1) for regulating the first hydraulic pressure (Pp1) of (H1); A second pressure regulating valve (UP2) that adjusts the second hydraulic pressure (Pp2) of the second braking system (H2), and a normally open left rear wheel provided for the left rear wheel cylinder (CWl) inlet valve (VIl)," a normally open right rear wheel inlet valve (VIk) provided for the right rear wheel cylinder (CWk)," and "based on the required deceleration (Gs), By controlling the energization of the first and second pressure regulating valves (UP1, UP2), the first and second hydraulic pressures (Pp1, Pp2) are adjusted, and the right rear wheel and left rear wheel inlet valves ( A controller (ECU) for controlling energization of VIk, VIl).

In the vehicle automatic braking system, the controller (ECU) controls the right rear wheel and the left rear wheel until the elapsed time (Tk) from the start time (t0) of the automatic braking control reaches a predetermined time (tx). The inlet valves (VIk, VIl) are closed , and the automatic braking control is executed by the first and second pressure regulating valves (UP1, UP2).

According to the above configuration, when the automatic braking control is started, an increase in the braking fluid pressures Pwk and Pwl of the rear wheel cylinders CWk and CWl is suppressed. A sufficient lateral force is ensured for the wheels WHk and WHl, and the directional stability of the vehicle is improved.

Further, in the vehicle automatic braking device, the controller (ECU) determines whether or not the braking is sudden based on the required deceleration (Gs). The rear wheel and left rear wheel inlet valves (VIk, VIl) are opened , and the automatic braking control is executed by the first and second pressure regulating valves (UP1, UP2). until the elapsed time (Tk) from the start time (t0) of the automatic braking control reaches a predetermined time (tx), the right rear wheel and left rear wheel inlet valves (VIk, VIl) are closed. , the automatic braking control is executed by the first and second pressure regulating valves (UP1, UP2).

According to the above configuration, even if the automatic braking control operates even in the normal braking (service brake) area, when the emergency automatic braking control is started, the rear wheel cylinders CWk and CWl are braked. Since an increase in the hydraulic pressures Pwk and Pwl is suppressed, the lateral force of the rear wheels WHk and WHl is sufficiently secured even when the vehicle is deflected, and the directional stability of the vehicle is improved.

1 is an overall configuration diagram for describing an embodiment of an automatic braking device JS for a vehicle; FIG. FIG. 3 is a functional block diagram for explaining arithmetic processing in a driving assistance controller ECJ and a braking controller ECU; FIG. 4 is a flow chart for explaining a first example of automatic braking control; FIG. 4 is a time series diagram for explaining the operation of the first example of automatic braking control; FIG. 9 is a flow chart for explaining a second example of automatic braking control; FIG. 9 is a time series diagram for explaining the operation of a second example of automatic braking control;

<Symbols of constituent members, suffixes at the end of symbols, and motion/movement directions>
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 various symbols are generic symbols indicating which wheels they relate 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 "1" and "2" attached to the end of various symbols are generic symbols indicating which of the two braking systems (diagonal braking system) it relates to. Specifically, "1" indicates the first system, and "2" indicates the second system. For example, two master cylinder fluid paths are denoted as a first master cylinder fluid path HM1 and a second master cylinder fluid path HM2. Furthermore, the suffixes "1" and "2" at the end of the symbols can be omitted. If the suffixes "1" and "2" are omitted, each symbol collectively represents each of the two braking systems. For example, "HM" represents the master cylinder fluid path for each braking system.

<Embodiment of Automatic Braking Device for Vehicle>
An embodiment of an automatic braking system JS for a vehicle will be described with reference to the overall configuration diagram of FIG. The master cylinder CM is connected to the wheel cylinder CW via a master cylinder fluid passage HM and a wheel cylinder fluid passage HW. The fluid path is a path for moving the brake fluid BF, which is the working fluid of the automatic braking device JS, and corresponds to brake pipes, fluid unit flow paths, hoses, and the like. The inside of the fluid path is filled with the damping fluid BF. In the fluid path, the side closer to the master cylinder CM is called "upper", and the side closer to the wheel cylinder CW is called "lower".

A vehicle employs two fluid paths (that is, two braking systems). Of the two braking systems, the first system (system associated with the first master cylinder chamber Rm1) is connected to the right front wheel and left rear wheel cylinders CWi and CWl. The second system (system associated with the second master cylinder chamber Rm2) of the two braking systems is connected to the left front wheel and right rear wheel cylinders CWj and CWk. A so-called diagonal type (also referred to as "X type") type is employed as the two braking systems of the vehicle.

A vehicle equipped with the automatic braking device JS is equipped with a braking operation member BP, a wheel cylinder CW, a master reservoir RV, a master cylinder CM, and a brake booster BB.

A braking operation member (for example, a brake pedal) BP is a member operated by the driver to decelerate the vehicle. By operating the brake operation member BP, the hydraulic pressure (braking hydraulic pressure) Pw of the wheel cylinder CW is adjusted, the braking torque Tq of the wheel WH is adjusted, and braking force is generated on the wheel WH.

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, and a friction member (for example, a brake pad) is pressed against the rotating member KT by increasing the pressure (brake fluid pressure) Pw of the brake fluid BF inside the brake caliper. Since the rotating member KT and the wheels WH are fixed so as to rotate integrally, braking torque Tq is generated in the wheels WH by the frictional force generated at this time. A deceleration slip is generated in the wheels WH by the braking torque Tq, resulting in a braking force.

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 master cylinder CM is mechanically connected to the braking operation member BP via a brake rod, a clevis (U-shaped link), and the like. The master cylinder CM is of a tandem type, and its interior is divided into first and second master cylinder chambers Rm1 and Rm2 by master pistons PL1 and PL2. When the brake operation member BP is not operated, the master cylinder chambers Rm1, Rm2 of the master cylinder CM and the reservoir RV are in communication. First and second master cylinder fluid passages HM1 and HM2 are connected to the master cylinder CM. When the brake operation member BP is operated, the master pistons PL1, PL2 move forward, and the two master cylinder chambers Rm1, Rm2 are cut off from the reservoir RV. When the operation of the brake operating member BP is increased, the brake fluid BF is pressure-fed from the master cylinder CM toward the wheel cylinders CWi-CWl through the master cylinder fluid passages HM1 and HM2.

The brake booster (simply referred to as "booster") BB reduces the operating force Fp of the brake operating member BP by the driver. A negative pressure type is adopted as the booster BB. A negative pressure is created by the engine or an electric negative pressure pump. As the booster BB, one using an electric motor as a drive source may be employed (for example, an electric booster, an accumulator type hydraulic booster).

Each wheel WH of the vehicle is provided with a wheel speed sensor VW to detect the wheel speed Vw. The signal of the wheel speed Vw is used for braking control independent of each wheel, such as anti-skid control (anti-lock brake control) that suppresses the tendency of the wheels WH to lock (that is, excessive deceleration slip).

A steering operation member (for example, a steering wheel) is provided with a steering angle sensor SA to detect a steering angle Sa. A vehicle body is provided with a yaw rate sensor YR to detect a yaw rate (yaw angular velocity) Yr. In addition, a longitudinal acceleration sensor GX and a lateral An acceleration sensor GY is provided. These signals (Sa, Yr, etc.) are used for vehicle motion control such as vehicle stabilization control (so-called ESC) that suppresses excessive oversteer behavior and understeer behavior.

A braking operation amount sensor BA is provided to detect an operation amount Ba of a braking operation member BP (brake pedal) by the driver. As the braking operation amount sensor BA, a master cylinder hydraulic pressure sensor PM that detects the hydraulic pressure (master cylinder hydraulic pressure) Pm in the master cylinder CM, an operation displacement sensor SP that detects the operation displacement Sp of the braking operation member BP, and a braking At least one of the operating force sensors FP is employed to detect the operating force Fp of the operating member BP. That is, the operation amount sensor BA detects at least one of the master cylinder hydraulic pressure Pm, the operation displacement Sp, and the operation force Fp as the braking operation amount Ba.

Signals such as wheel speed Vw, steering angle Sa, yaw rate Yr, longitudinal acceleration (deceleration) Gx, lateral acceleration Gy, braking operation amount Ba (Pm, Sp, Fp) detected by each sensor (VW, etc.) , is input to the braking controller ECU.

Vehicles are equipped with driving assistance systems to avoid collisions with obstacles or to reduce damage in the event of a 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 relative distance Ob is input to the driving assistance controller ECJ. The driving assistance controller ECJ calculates the required deceleration Gs based on the relative distance Ob. The required deceleration Gs is a target value of vehicle deceleration for avoiding the vehicle from colliding with an object. The requested deceleration Gs is transmitted to the brake controller ECU via the communication bus BS.

≪Brake controller ECU≫
The automatic braking device JS is composed of a braking controller ECU and a fluid unit HU. A brake controller (also called an "electronic control unit") ECU is composed of an electric circuit board on which a microprocessor MP or the like is mounted and a control algorithm programmed in the microprocessor MP. The braking controller ECU is network-connected to other controllers (driving assistance controller ECJ, etc.) through a communication bus BS mounted on the vehicle so as to share signals (detected values, calculated values, etc.). For example, the braking controller ECU calculates the vehicle body speed Vx and transmits it to the driving assistance controller ECJ. On the other hand, from the driving support controller ECJ to the braking controller ECU, a required deceleration Gs (target value) for executing automatic braking control (braking control for avoiding a collision with an obstacle or reducing collision damage) is sent. The braking controller ECU executes automatic braking control based on the required deceleration Gs.

A braking controller ECU (electronic control unit) controls the electric motor ML of the hydraulic unit HU and three different solenoid valves UP, VI, VO. Specifically, drive signals Up, Vi and Vo for controlling various electromagnetic valves UP, VI and VO are calculated based on a control algorithm in microprocessor MP. Similarly, a drive signal Ml for controlling the electric motor ML, which is the drive source of the electric pump DL, is calculated.

The brake controller ECU is provided with a drive circuit DR to drive the solenoid valves UP, VI, VO and the electric motor ML. 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 ML. Based on the motor drive signal Ml, the energization state of each switching element is controlled, and the output of the electric motor ML is controlled. Further, in the drive circuit DR, based on the drive signals Up, Vi, and Vo, the energized state (that is, the excited state) of the electromagnetic valves UP, VI, and VO is controlled by the switching elements. The drive circuit DR is provided with energization amount sensors for detecting actual energization amounts of the electric motor ML and the solenoid valves UP, VI, and VO. For example, a current sensor is provided as an energization amount sensor to detect the current value (energization amount) supplied to the electric motor ML and the electromagnetic valves UP, VI, and VO.

≪Fluid unit HU≫
The fluid unit HU is connected to the first and second master cylinder fluid paths HM1, HM2. At portions Bt1 and Bt2 (branching portions) in the fluid unit HU, the two master cylinder fluid passages HM1 and HM2 are branched into four wheel cylinder fluid passages HWi to HWl, which are connected to the four wheel cylinders CWi to CWl. be. Here, the braking system connected to the right front wheel and left rear wheel cylinders CWi and CWl is referred to as "first braking system H1". A braking system connected to the left front wheel and right rear wheel cylinders CWj and CWk is referred to as a "second braking system H2".

Therefore, in the first braking system H1, the first master cylinder fluid passage HM1 is branched into the right front wheel and left rear wheel cylinder fluid passages HWi and HWl at the first branch portion Bt1. The front right wheel and rear left wheel cylinder fluid passages HWi and HWl are connected to the front right wheel and rear left wheel cylinders CWi and CWl. Similarly, in the second braking system H2, the second master cylinder fluid passage HM2 is branched into the left front wheel and right rear wheel cylinder fluid passages HWj and HWk at the second branch portion Bt2. Left front wheel and right rear wheel cylinder fluid passages HWj and HWk are connected to left front wheel and right rear wheel cylinder fluid paths CWj and CWk. That is, the vehicle employs a diagonal type (X type) braking system having a first braking system H1 (=HM1+HWi, HWl) and a second braking system H2 (=HM2+HWj, HWk).

The fluid unit HU comprises a pressure regulating valve UP, an electric pump DL, a low pressure reservoir RL, a master cylinder hydraulic pressure sensor PM, a regulating hydraulic pressure sensor PP, an inlet valve VI and an outlet valve VO.

First and second pressure regulating valves UP1 and UP2 (=UP) are provided in the first and second master cylinder fluid paths HM1 and HM2 (=HM). As the pressure regulating valve UP, a linear solenoid valve (also referred to as a “proportional valve” or “differential pressure valve”) whose valve opening amount (lift amount) is continuously controlled based on the energized state (for example, supply current) is adopted. The pressure regulating valve UP is controlled by the controller ECU based on first and second pressure regulating valve drive signals Up1 and Up2 (=Up). Here, normally open solenoid valves are employed as the first and second pressure regulating valves UP1 and UP2.

The electric pump DL is composed of one electric motor ML and two fluid pumps QL1 and QL2 (=QL). The electric motor ML is controlled by the controller ECU based on the drive signal Ml. The electric motor ML rotates and drives the first and second fluid pumps QL1 and QL2 together. First and second suction portions Bs1 positioned between the first and second pressure regulating valves UP1 and UP2 and the master cylinder CM (that is, above the pressure regulating valve UP) by the first and second fluid pumps QL1 and QL2. , Bs2 from which the brake fluid BF is pumped. The pumped-up braking fluid BF is discharged to first and second discharge portions Bt1 and Bt2 located below the first and second pressure regulating valves UP1 and UP2. Here, the electric pump DL is rotated only in one direction. First and second low-pressure reservoirs RL1 and RL2 (=RL) are provided on the suction sides of the first and second fluid pumps QL1 and QL2.

The controller ECU calculates the target energization amount of the pressure regulating valve UP based on the calculation result (for example, the target hydraulic pressure Pt) of the automatic braking control, and determines the drive signal Up based on this. Then, according to the drive signal Up, the energization amount (current) to the pressure regulating valve UP is adjusted, and the valve opening amount of the pressure regulating valve UP is adjusted.

When the fluid pump QL is driven, a reflux (flow of the circulating brake fluid BF) is formed in the order of "Bs→RL→QL→Bt→UP→Bs". When the pressure regulating valve UP is not energized and the normally open type pressure regulating valve UP is fully open, the hydraulic pressure above the pressure regulating valve UP (that is, the master cylinder hydraulic pressure Pm) and the pressure below the pressure regulating valve UP matches the actual hydraulic pressure Pp (referred to as "adjusted hydraulic pressure").

The amount of energization to the normally open first and second pressure regulating valves UP1 and UP2 is increased, and the valve opening amount thereof is decreased. The first and second pressure regulating valves UP1 and UP2 restrict the circulation of the braking fluid BF, and the orifice effect produces the first and second regulating hydraulic pressures (actual hydraulic pressures) Pp1 and Pp2 (“first and second hydraulic pressures”). , and "=Pp") is increased from the first and second master cylinder hydraulic pressures Pm1 and Pm2 (=Pm) (therefore, "Pp>Pm"). That is, the differential pressure between the master cylinder hydraulic pressure Pm and the regulated hydraulic pressure Pp is adjusted by the electric pump DL and the pressure regulating valve UP. By controlling the electric pump DL and the pressure regulating valve UP, the regulating hydraulic pressure Pp (resulting in the braking hydraulic pressure Pw of the wheel cylinder CW) is higher than the master cylinder hydraulic pressure Pm corresponding to the operation of the brake operating member BP. Increased. For example, when the brake operating member BP is not operated, "Pm=0", but the brake hydraulic pressure Pw is raised from "0" by the automatic braking control.

First and second master cylinder hydraulic pressure sensors PM1 and PM2 are provided above the pressure regulating valve UP (closer to the master cylinder CM) to detect the first and second master cylinder hydraulic pressures Pm1 and Pm2. Since "Pm1=Pm2" basically holds, one of the first and second master cylinder hydraulic pressure sensors PM1 and PM2 can be omitted.

First and second regulating hydraulic pressure sensors are provided below the pressure regulating valve UP (closer to the wheel cylinder CW) to detect first and second regulating hydraulic pressures (first and second hydraulic pressures) Pp1 and Pp2. PP1 and PP2 are provided. In the pressure regulating valve UP, since the relationship between the energization amount (supplied current) and the differential pressure (pressure difference between the master cylinder hydraulic pressure Pm and the regulating hydraulic pressure Pp) is known, the first and second regulating hydraulic pressure sensors At least one of PP1, PP2 may be omitted. Since the amount of energization to the pressure regulating valve UP is adjusted by the drive signal Up, for example, when the two regulating hydraulic pressure sensors PP are omitted, the drive signal Up (that is, the amount of energization to the pressure regulating valve UP) Based on this, the adjustment hydraulic pressure Pp can be estimated.

The first braking system H1 is composed of a first master cylinder fluid passage HM1 and right front wheel and left rear wheel cylinder fluid passages HWi and HWl. CWi and CWl are connected. The right front wheel and left rear wheel inlet valves VIi and VIl are provided in the right front wheel and left rear wheel cylinder fluid paths HWi and HWl branched from the first master cylinder fluid path HM1. That is, the right front wheel and left rear wheel inlet valves VIi and VIl are provided between the branch portion Bt1 and the right front wheel and left rear wheel cylinders CWi and CWl in the first braking system H1. In other words, the first braking system H1 is provided with normally open right front wheel and left rear wheel inlet valves VIi and VIl for the right front wheel and left rear wheel cylinders CWi and CWl.

Similarly, the second braking system H2 is composed of a second master cylinder fluid passage HM2, and wheel cylinder fluid passages HWj and HWk for the left front wheel and right rear wheel. The wheel cylinders CWj and CWk are connected. Left front wheel and right rear wheel inlet valves VIj and VIk are provided in left front wheel and right rear wheel cylinder fluid paths HWj and HWk branched from the second master cylinder fluid path HM2. That is, the left front wheel and right rear wheel inlet valves VIj and VIk are provided between the branch portion Bt2 and the left front wheel and right rear wheel cylinders CWj and CWk in the second braking system H2. In other words, the second braking system H2 is provided with normally open left front wheel and right rear wheel inlet valves VIj and VIk for left front wheel and right rear wheel cylinders CWj and CWk.

Each wheel cylinder fluid passage HW is connected to a low pressure reservoir RL via a normally closed outlet valve VO below inlet valve VI (between inlet valve VI and wheel cylinder CW). A fluid path connecting the wheel cylinder fluid path HW and the low pressure reservoir RL is referred to as a "reservoir fluid path HR". Accordingly, each outlet valve VO is provided for each reservoir fluid line HR.

A normally open ON/OFF electromagnetic valve is employed as the inlet valve VI. Here, the "on/off solenoid valve" is a 2-port 2-position switching type solenoid valve that has two positions, an open position and a closed position. In the normally open inlet valve VI, an open position and a closed position are selectively realized. The open state of the inlet valve VI is adjusted by the drive signal Vi calculated based on the duty ratio Du. Here, the "duty ratio" is the ratio of the pulse ON time (energization time) in a pulse train that continues at a constant cycle. Since the inlet valve VI is of the normally open type, it is fully opened when not energized (that is, when the duty ratio is "0%"), and when fully energized (that is, when the duty ratio Du is "100%"). case) is fully closed. By adjusting the duty ratio Du between 0% and 100%, the open state of the inlet valve VI can be adjusted.

A normally closed ON/OFF solenoid valve is employed as the outlet valve VO. The normally closed outlet valve VO also selectively realizes an open position and a closed position. Similarly to the inlet valve VI, the open state of the outlet valve VO is also adjusted by the drive signal Vo calculated based on the duty ratio Du (ratio of energization time per unit time). Since the outlet valve VO is normally closed, it is fully closed when not energized (Du=0%) and fully opened when fully energized (Du=100%). The open state (closed state) of the outlet valve VO can be adjusted by adjusting the duty ratio Du between 0% and 100%.

The inlet valve VI and the outlet valve VO have the same configuration for each wheel WH. The brake fluid pressure Pw of each wheel can be independently controlled by the inlet valve VI and the outlet valve VO. A linear solenoid valve may be employed as at least one of the inlet valve VI and the outlet valve VO instead of the on/off solenoid valve. For example, a normally open linear solenoid valve can be used as the inlet valve VI. In this case, the opening amount of the inlet valve VI is controlled by the amount of energization (supplied current) to the inlet valve VI, like the pressure regulating valve UP.

For example, in antiskid control, to reduce the hydraulic pressure Pw in the wheel cylinder CW, the inlet valve VI is closed and the outlet valve VO is opened. Inflow of the brake fluid BF from the inlet valve VI is blocked, the brake fluid BF in the wheel cylinder CW flows out to the low pressure reservoir RL, and the brake fluid pressure Pw is reduced. Also, to increase the braking fluid pressure Pw, the inlet valve VI is opened and the outlet valve VO is closed. The brake fluid BF is prevented from flowing out to the low-pressure reservoir RL, and the adjustment fluid pressure Pp adjusted by the pressure adjustment valve UP is introduced into the wheel cylinder CW to increase the brake fluid pressure Pw. Further, both the inlet valve VI and the outlet valve VO are closed to maintain the hydraulic pressure (brake hydraulic pressure) Pw in the wheel cylinder CW.

<Arithmetic Processing in Driving Support Controller ECJ and Braking Controller ECU>
Arithmetic processing in the driving assistance controller ECJ and the braking controller ECU will be described with reference to the functional block diagram of FIG. A required deceleration Gs in automatic braking control is calculated by the driving support controller ECJ. The requested deceleration Gs is transmitted to the brake controller ECU via the communication bus BS. The braking controller ECU controls the hydraulic units HU (ML, UP, etc.) to adjust the braking fluid pressure Pw (that is, braking torque Tq) of each wheel WH based on the required deceleration Gs.

The vehicle detects the distance (relative distance) Ob between the vehicle and objects (other vehicles, fixed objects, bicycles, people, animals, etc.) that the vehicle is traveling on. A distance sensor OB is provided. For example, a camera, radar, or the like is used as the distance sensor OB. Also, when a fixed object is stored in the map information, a navigation system can be used as the distance sensor OB. The detected relative distance Ob is input to the driving assistance controller ECJ. The driving assistance controller ECJ includes a collision margin time calculation block TC, a headway time calculation block TW, and a required deceleration calculation block GS.

A collision margin time calculation block TC calculates a collision margin time Tc based on the relative distance Ob between an object in front of the vehicle and the own vehicle. The collision margin time Tc is the time until the host vehicle collides with an object. Specifically, the collision margin time Tc is determined by dividing the relative distance Ob between an object in front of the vehicle and the own vehicle by the speed difference (that is, the relative speed) between the obstacle and the own vehicle. be. Here, the relative velocity is calculated by time-differentiating the relative distance Ob.

A headway time calculation block TW calculates a headway time Tw based on the relative distance Ob and the vehicle body speed Vx. The headway time Tw is the time it takes for the host vehicle to reach the current position of the forward object. Specifically, the headway time Tw is calculated by dividing the relative distance Ob by the vehicle speed Vx. Note that when the object ahead of the vehicle is stationary, the collision margin time Tc and the headway time Tw match. The vehicle body speed Vx is acquired from the vehicle body speed calculation block VX of the brake controller ECU via the communication bus BS.

A required deceleration calculation block GS calculates a required deceleration Gs based on the collision margin time Tc and the headway time Tw. The required deceleration Gs is a target deceleration of the own vehicle for avoiding collision between the own vehicle and a forward object. The required deceleration Gs is calculated according to the calculation map Zgs so that it decreases as the time to collision Tc increases (or increases as the time to collision Tc decreases). Further, the required deceleration Gs can be adjusted based on the headway time Tw. The required deceleration Gs is adjusted based on the headway time Tw such that the larger the headway time Tw, the smaller the required deceleration Gs (or the smaller the headway time Tw, the larger the required deceleration Gs). . The requested deceleration Gs is input to the braking controller ECU via the communication bus BS.

Each wheel WH of the vehicle is provided with a wheel speed sensor VW to detect the rotational speed (wheel speed) Vw of the wheel WH. The detected wheel speed Vw is input to the braking controller ECU. The brake controller ECU includes a vehicle body speed calculation block VX, an actual deceleration calculation block GA, an automatic braking control block JC, and a drive circuit DR.

A vehicle speed calculation block VX calculates a vehicle speed Vx based on the wheel speed Vw. For example, during non-braking including acceleration of the vehicle, the vehicle body speed Vx is calculated based on the slowest one (slowest wheel speed) of the four wheel speeds Vw. During braking, the vehicle body speed Vx is calculated based on the fastest one (fastest wheel speed) of the four wheel speeds Vw. Furthermore, in the calculation of the vehicle body speed Vx, a limit can be placed on the amount of change over time. That is, the upper limit value αup of the increasing gradient of the vehicle speed Vx and the lower limit value αdn of the decreasing gradient of the vehicle speed Vx are set, and the change in the vehicle speed Vx is restricted by the upper and lower limit values αup and αdn. The calculated vehicle body speed Vx is transmitted to the headway time calculation block TW of the driving assistance controller ECJ via the communication bus BS.

An actual deceleration calculation block GA calculates an actual deceleration Ga based on the vehicle body speed Vx. The actual deceleration Ga is deceleration (negative acceleration) in the front-rear direction (traveling direction) of the vehicle that actually occurs. Specifically, the vehicle body speed Vx is time-differentiated to calculate the actual deceleration Ga. Further, the longitudinal acceleration (deceleration) Gx is employed for the calculation of the actual deceleration Ga. In this case, the longitudinal acceleration Gx (detected value) is directly determined as the actual deceleration Ga. The longitudinal acceleration Gx is detected by the longitudinal acceleration sensor GX, and the longitudinal acceleration Gx includes the gradient of the road surface on which the vehicle is traveling. Therefore, the differential value of the vehicle body speed Vx is preferable to the longitudinal acceleration Gx for calculating the actual deceleration Ga. Further, in order to improve robustness, the actual vehicle deceleration Ga may be calculated based on the differential value (calculated value) of the vehicle speed Vx and the longitudinal acceleration Gx (detected value).

In the automatic braking control block JC, automatic braking control is executed based on the requested deceleration Gs and the actual deceleration Ga. First, the automatic braking control block JC determines whether automatic braking is necessary. If the driver has already operated the braking operation member BP and the actual deceleration Ga is greater than the required deceleration Gs, automatic braking control is unnecessary. On the other hand, when the actual deceleration Ga is smaller than the required deceleration Gs, feedback control (automatic braking control) based on the deceleration of the vehicle is executed so that the actual deceleration Ga matches the required deceleration Gs. The automatic braking control block JC includes a target hydraulic pressure calculation block PT, an elapsed time calculation block TK, and a drive signal calculation block DS.

A target hydraulic pressure calculation block PT calculates first and second target hydraulic pressures Pt1 and Pt2 (=Pt) based on the required deceleration Gs and a preset calculation map. The first target hydraulic pressure Pt1 is a target for the regulated hydraulic pressure Pp1 ("first hydraulic pressure actual value" and equivalent to "first hydraulic pressure") of the first braking system H1 connected to the right front wheel cylinder CWi. value. The second target hydraulic pressure Pt2 is the adjusted hydraulic pressure Pp2 of the second braking system H2 connected to the left front wheel cylinder CWj ("second hydraulic pressure actual value" and equivalent to "second hydraulic pressure"). is the target value for Here, the first target hydraulic pressure Pt1 and the second target hydraulic pressure Pt2 are calculated to be equal (that is, "Pt1=Pt2"). Since the vehicle specifications (mass, height of the center of gravity, etc.) and the specifications of the braking device (braking effective radius of the rotary member KT, friction coefficient of the friction material, pressure receiving area of the wheel cylinder CW, etc.) are already known, the calculation map Now, using these specifications, the first and second target hydraulic pressures Pt1 and Pt2 are determined to increase as the required deceleration Gs increases.

An elapsed time calculation block TK calculates an elapsed time Tk from the start of the automatic braking control. As will be described later, the elapsed time Tk is determined based on the distribution of the braking force between the front and rear wheels (contribution of the front and rear wheels to the total braking force acting on the vehicle) so that the deflection of the vehicle can be suppressed in advance when the automatic braking control is executed. used to adjust

In the drive signal calculation block DS, the motor drive signal Ml, the pressure regulation valve drive signal Up, and the inlet valve and outlet valve drive signals Vi and Vo are calculated. For example, based on the target hydraulic pressure Pt, the target rotation speed of the electric motor ML is determined. value) is calculated. Also, the electric motor ML may be driven at a preset constant number of revolutions. In this case, an ON signal for instructing rotation of the electric motor ML is determined as the motor drive signal Ml.

In the drive signal calculation block DS, the pressure regulating valve drive signal Up is determined based on the target hydraulic pressure Pt. The drive signal Up is a signal sent to the drive circuit DR to control the pressure regulator valve UP. The pressure regulating valve UP is a normally open linear solenoid valve, and the valve opening amount is fully open when not energized. As the energization amount (current value) increases, the valve opening amount is decreased, the return passage including the fluid pump QL is throttled, and the actual hydraulic pressure Pp (resulting in the braking hydraulic pressure Pw) is reduced. Increased. In the pressure regulating valve UP, since the relationship between the supply energization amount and the regulated hydraulic pressure Pp is known, the drive signal Up (the energization instruction amount) is calculated based on the target hydraulic pressure Pt. That is, when the target hydraulic pressure Pt is relatively small, the energization instruction value Up is calculated to be small, and is determined so that the energization instruction value Up increases as the target hydraulic pressure Pt increases.

In addition, in the drive signal calculation block DS, based on the elapsed time Tk from the start of the automatic braking control, the left and right rear wheel duty ratios are adjusted so as to adjust the energization state of the left and right rear wheel inlet valves VIk and VIl. A ratio Duk, Dul (that is, rear wheel inlet valve drive signals Vik, Vil) is calculated. Specifically, at the beginning of the automatic braking control, "Duk, Dul=100%" is determined, and the rear wheel inlet valves VIk and VIl are fully closed. That is, the adjusted hydraulic pressure Pp is supplied to the front wheel cylinders CWi and CWj, but not to the rear wheel cylinders CWk and CWl. Therefore, the braking force is distributed relatively to the front wheels, and the contribution of the braking force to the front wheels is increased and the contribution of the braking force to the rear wheels is decreased compared to the normal distribution. Here, the "regular distribution" is the front-to-rear distribution of the braking force when the rear wheel inlet valves VIk and VIl are in the fully open position. Even if vehicle deflection occurs, sufficient rear wheel lateral force is generated to ensure a stabilizing moment to reduce vehicle deflection. As a result, swaying of the vehicle in the initial stage of starting automatic braking control is suppressed, and directional stability can be ensured. As the elapsed time Tk increases, the rear wheel duty ratios Duk and Dul are gradually decreased, and the rear wheel inlet valves VIk and VIl are gradually opened. As a result, the adjusted hydraulic pressure Pp is supplied to the rear wheel cylinders CWk and CWl, and sufficient vehicle deceleration can be ensured.

Further, in the drive signal calculation block DS, when the brake fluid pressure Pw needs to be decreased, the drive signal Vo is output so as to open the outlet valve VO (communication state of the reservoir fluid passage HR).

In the drive circuit DR, the energization states of the electric motor ML and the linear solenoid valve (pressure regulating valve) UP are controlled by switching elements (power semiconductor devices) based on the drive signals Ml and Up. The drive circuit DR is provided with an energization amount sensor (current sensor) for detecting the actual energization amount (supplied current value) of the electric motor ML and the pressure regulating valve UP. Current feedback control is performed to match. In the drive circuit DR, the drive signals Vi and Vo control the energization states of the on/off solenoid valves VI and VO by means of switching elements, and as a result, the valve open state (valve closed state) is adjusted.

<First processing example of automatic braking control>
A first processing example of the automatic braking control will be described with reference to the flowchart of FIG. Automatic braking control is based on the object (obstacle) in front of the vehicle and the required deceleration Gs according to the relative distance Ob between the vehicle and the wheel cylinder CW so as to avoid collision between the vehicle and the obstacle. The hydraulic pressure (brake hydraulic pressure) Pw is increased to be equal to or higher than the hydraulic pressure (master cylinder hydraulic pressure) Pm of the master cylinder CM. In particular, the first processing example performs sudden braking at a predetermined deceleration rate or higher only when the probability of collision between the vehicle and an obstacle is high (that is, in an emergency). For example, it is a region close to the upper limit of the coefficient of friction between the wheels and the road surface, and is operated at deceleration (0.7 to 0.8 G or more) that is much higher than normal braking (during normal braking).

At step S110, various signals are read. Specifically, the required deceleration Gs, the longitudinal acceleration Gx (detected value), and the vehicle body speed Vx are acquired. In step S120, the actually occurring deceleration Ga in the longitudinal direction of the vehicle is calculated based on at least one of the longitudinal acceleration (detected value) Gx and the vehicle body speed Vx.

At step S130, it is determined whether or not automatic braking control is required, and if automatic braking control is required, the target hydraulic pressure Pt is calculated based on the required deceleration Gs. Specifically, the necessity of automatic braking control is determined based on a comparison between the required deceleration Gs and the actual deceleration Ga. When "Gs≤Ga" and the driver is sufficiently decelerating the vehicle, automatic braking control is unnecessary, so "Pt = 0" is determined and pressurization by automatic braking control is executed. not. On the other hand, if "Gs>Ga", automatic braking control is necessary, so the target hydraulic pressure Pt (=Pt1, Pt2) is determined based on the required deceleration Gs. The first and second target hydraulic pressures Pt1 and Pt2 are target values for the actual first and second adjusted hydraulic pressures Pp1 and Pp2 (first and second hydraulic pressures). Here, the first and second target hydraulic pressures Pt1 and Pt2 are calculated as "Pt1=Pt2", and pressurization is performed so that the first and second adjustment hydraulic pressures (actual hydraulic pressures) Pp1 and Pp2 are the same. instructions are given.

In step S140, the elapsed time Tk from the calculation period when the automatic braking control is started (that is, the start time of the control) is calculated. At step S150, it is determined whether or not the elapsed time Tk is less than the predetermined time tx. Here, the predetermined time tx is a threshold for determination and is a preset constant. If "Tk<tx", the process proceeds to step S160. On the other hand, if "Tk≧tx", the process proceeds to step S180.

In step S160, the rear wheel inlet valves VIk and VIl for the rear wheel cylinders CWk and CWl are fully energized. That is, the duty ratios (rear wheel duty ratios) Duk and Dul of the rear wheel inlet valves VIk and VIl are determined to be 100%, and the rear wheel inlet valves VIk and VIl are fully closed (closed position). Therefore, at the beginning of the automatic braking control (when the elapsed time Tk is less than the predetermined time tx), the regulated hydraulic pressure (actual hydraulic pressure) Pp increased from the master cylinder hydraulic pressure Pm by the pressure regulating valve UP It is not supplied (introduced) to the rear wheel cylinders CWk and CWl.

At step S170, the electric motor ML is driven. For example, the electric motor ML is driven at its maximum output so that the number of revolutions increases rapidly. As a result, a recirculation of the brake fluid BF including the pressure regulating valve UP and the fluid pump QL (flow of the brake fluid BF circulating in the order of "QL→Bt→UP→Bs→RL→QL") is formed. Then, based on the first and second target hydraulic pressures Pt1 and Pt2, the first and second adjustment hydraulic pressures Pp1 and Pp2 (actual values or estimated values) are set to the first and second target hydraulic pressures Pt1 and Pt2. The first and second pressure regulating valves UP1 and UP2 are feedback-controlled so as to approach and match the (target value). Alternatively, in a configuration in which the regulating hydraulic pressure sensor PP is omitted, the relationship between the amount of energization to the pressure regulating valve UP and the differential pressure between the regulating hydraulic pressure Pp and the master cylinder hydraulic pressure Pm is known. Amounts of energization corresponding to the target hydraulic pressures Pt1 and Pt2 are supplied to the first and second pressure regulating valves UP1 and UP2. In any case, the drive signal (energization instruction signal) Up is determined based on the target hydraulic pressure Pt, and the amount of power supplied to the pressure regulating valve UP is controlled.

In controlling the amount of energization to the pressure regulating valve UP, feedback control of the amount of energization can be performed so that the actual amount of energization (value detected by the energization amount sensor) matches the target amount of energization (drive signal) Up. Furthermore, deceleration feedback control may be added in controlling the amount of energization to the pressure regulating valve UP so that the actual deceleration Ga matches the required deceleration Gs. That is, the first and second hydraulic pressures Pp1 and Pp2 are adjusted by the first and second pressure regulating valves UP1 and UP2.

In step S180, the amount of energization to the rear wheel inlet valves VIk and VIl is gradually reduced based on the elapsed time Tk. That is, when the elapsed time Tk reaches or exceeds the predetermined time tx, the rear wheel duty ratios Duk, Dul are gradually decreased from 100%, and the rear wheel inlet valves VIk, VIl are gradually opened. As a result, the adjusted hydraulic pressure Pp is introduced into the rear wheel cylinders CWk and CWl, and the rear wheel brake hydraulic pressures Pwk and Pwl are gradually increased. Ultimately, the rear wheel braking hydraulic pressures Pwk and Pwl match the first and second adjusted hydraulic pressures Pp1 and Pp2.

<Operation of first processing example of automatic braking control>
The vehicle has diagonal first and second braking systems (two braking systems). The hydraulic pressure Pw of the wheel cylinder CW is increased from the hydraulic pressure Pm of the master cylinder CW by the automatic braking device JS based on the required deceleration Gs according to the distance Ob between the vehicle and an object in front of the vehicle. Automatic braking control is achieved. The automatic braking device JS includes "a first pressure regulating valve UP1 for adjusting a first hydraulic pressure Pp1 of a first braking system H1 connected to the right front wheel and left rear wheel cylinders CWi and CWl" A second pressure regulating valve UP2 for adjusting the second hydraulic pressure Pp2 of the second braking system H2 connected to the wheel cylinders CWj and CWk; Wheel inlet valve VIl", "normally open right rear wheel inlet valve VIk provided for right rear wheel cylinder CWk", and "first and second pressure regulating valves UP1, UP1, a controller ECU that adjusts the first and second hydraulic pressures Pp1 and Pp2 by controlling energization to UP2 and controls energization to the right rear wheel and left rear wheel inlet valves VIk and VIl. Configured. Then, the controller ECU energizes the right rear wheel and left rear wheel inlet valves VIk and VIl, increases the energization of the first and second pressure regulating valves UP1 and UP2, and starts automatic braking control. .

The operation of the first processing example of the automatic braking control will be described with reference to the time series diagram of FIG. The diagram assumes a situation in which the driver does not operate the brake operation member BP and the vehicle is automatically and rapidly decelerated by the automatic braking device JS.

Before time t0, the automatic braking control has not started, and "Gs=0". Therefore, the target hydraulic pressure Pt (result, the adjusted hydraulic pressure Pp) is "0", the duty ratios for all the wheels including the rear wheel duty ratios Duk, Dul are "0%", and the inlet valves VIi to VIl is in a non-energized state and is in the fully open position.

At time t0, automatic braking control is started. The electric motor ML is started to rotate and the target hydraulic pressure Pt is increased from "0" according to the required deceleration Gs. Energization of the pressure regulating valve UP is started, and the regulating hydraulic pressure Pp begins to increase from "0 (non-braking state)". Since the adjusted hydraulic pressure Pp is controlled to match the target hydraulic pressure Pt, they overlap in the diagrams. At this time, the front wheel inlet valves VIi and VIj remain de-energized, but the rear wheel inlet valves VIk and VIl are instructed to be "Duk, Dul=100%" and are fully energized. Since the front wheel inlet valves VIi and VIj are in the open position, the first and second adjustment hydraulic pressures Pp1 and Pp2 are supplied. On the other hand, since the rear wheel inlet valves VIk and VIl are in the completely closed position, the first and second adjustment hydraulic pressures Pp1 and Pp2 are not supplied to the rear wheel cylinders CWk and CWl, and the rear wheel brake fluid is The pressures Pwk and Pwl remain "0". Also, starting from time t0, the elapsed time Tk is started to be counted (that is, "Tk=0" at time t0).

At time t1, "target hydraulic pressure Pt (result, Pp=pa)" is achieved corresponding to "Gs=ga". At time t2, elapsed time Tk reaches predetermined time tx (predetermined value). From time t2, the rear wheel duty ratios Duk, Dul are gradually decreased at the gradient Kg, and the rear wheel inlet valves VIk, VIl begin to be gradually opened. Then, the first and second adjustment hydraulic pressures Pp1 and Pp2 start to be gradually supplied to the rear wheel cylinders CWk and CWl. As a result, the rear wheel brake hydraulic pressures Pwk and Pwl are gradually increased. At time t3, "Duk, Dul=0%", the rear wheel inlet valves VIk, VIl are fully opened, and the rear wheel brake fluid pressures Pwk, Pwl are equal to the front wheel brake fluid pressures Pwi, Pwj (=pa). match.

In the deceleration of the vehicle, the contribution of the braking force of the front wheels WHi and WHj is significantly higher than that of the braking force of the rear wheels WHk and WHl. This is because the load (vertical force) on the front wheels WHi and WHj increases and the load on the rear wheels WHk and WHl decreases due to the deceleration of the vehicle. Also, if the braking force of the rear wheels WHk and WHl becomes excessive, the directional stability of the vehicle is likely to be impaired. is set larger than the pressure receiving areas of the rear wheel cylinders CWk and CWl.

In addition, in order to rapidly increase the braking fluid pressure Pw of the wheel cylinder CW, first, an amount of braking fluid BF corresponding to the amount of fluid consumed by the wheel cylinder CW is supplied, and then further braking fluid BF is supplied. As a result, the braking fluid pressure Pw starts to increase. Here, the "fluid consumption" is the volume of the brake fluid BF consumed by the rigidity (deformation) of members such as brake calipers, hydraulic pipes (fluid passages), and friction materials arranged around the wheels. For the above reason, the amount of fluid consumed by the front wheel cylinders CWi and CWj is relatively large compared to the amount of fluid consumed by the rear wheel cylinders CWk and CWl.

In the automatic braking device JS, the first and second adjustment hydraulic pressures Pp1 and Pp2 are not supplied to the rear wheel cylinders CWk and CWl at the beginning of the automatic braking control (from time t0 to time t2). , the front wheel cylinders CWi, CWj are supplied with the first and second adjustment hydraulic pressures Pp1, Pp2 only. Therefore, the amount of brake fluid BF discharged by the first and second fluid pumps QL1 and QL2 is not consumed by the rear wheel cylinders CWk and CWl. That is, the entire discharge amount of the fluid pump QL is supplied to the front wheel cylinders CWi, CWj, and the front wheel braking fluid pressures Pwi, Pwj increase in response to increase, thereby efficiently decelerating the vehicle. In addition, since the increase in the rear wheel brake fluid pressures Pwk and Pwl is suppressed at the beginning of the control, even if the vehicle is deflected, the lateral force of the rear wheels WHk and WHl (that is, the stabilization moment ) is sufficiently ensured. As a result, the directional stability of the vehicle is improved, and the driver's uncomfortable feeling caused by the wobbling (deflection) of the vehicle is reduced.

Further, in the automatic braking device JS, the amount of energization to the left and right rear wheel inlet valves VIk, VIl is gradually reduced based on the elapsed time Tk from the time point when the automatic braking control was started (time point t2 to time point t3 until). As a result, the first and second adjustment hydraulic pressures Pp1 and Pp2 are supplied to the rear wheel cylinders CWk and CWl, the rear wheel braking hydraulic pressures Pwk and Pwl are sequentially increased, and finally the rear wheel braking hydraulic pressures Pwk and Pwl match the first and second adjustment hydraulic pressures Pp1 and Pp2. As a result, sufficient vehicle deceleration can be ensured. As described above, in the automatic braking system JS, in the initial stage of starting automatic braking control, vehicle deflection is suppressed, and vehicle deceleration is efficiently achieved without causing discomfort to the driver. . Sufficient vehicle deceleration can be ensured according to the continuation of the automatic braking control.

<Second processing example of automatic braking control>
A second processing example of the automatic braking control will be described with reference to the flowchart of FIG. In the first processing example, the automatic braking device JS is assumed to operate only in an emergency when the vehicle is highly likely to collide with an obstacle. The second processing example corresponds to the automatic braking device JS, in which the automatic braking control supports regular braking (also called "service braking") by the driver in addition to automatic braking in an emergency. Accordingly, in the second processing example, the processing of steps S135 and S185 is added to the first processing example. Note that since the calculation steps with the same symbols as in the first processing example execute the same processing, they will be briefly described below.

At step S110, various signals (such as Gs) are read. At step S120, the actual deceleration Ga is calculated. In step S130, it is determined whether automatic braking control is necessary. When the driver operates the braking operation member BP to decelerate the vehicle by himself (that is, when "Gs≤Ga"), automatic braking control is not executed. When "Gs>Ga", the first and second target hydraulic pressures Pt1 and Pt2 are calculated based on the required deceleration Gs. The first and second target hydraulic pressures Pt1 and Pt2 are target values for the actual first and second adjustment hydraulic pressures Pp1 and Pp2 (first and second hydraulic pressures), and are calculated as "Pt1=Pt2". be done. Note that the required deceleration Gs can also be indicated in the area of regular braking by the driver. In other words, the requested deceleration Gs encompasses (includes) a range from a normal region (eg, low deceleration and gentle braking) to an emergency region (eg, high deceleration and sudden braking).

At step S135, it is determined whether or not a sudden braking command has been issued (that is, whether it is emergency braking or regular braking in the execution of automatic braking control). For example, the determination is made based on "whether or not the amount of change in deceleration dG is greater than or equal to a predetermined amount of change dx and the required deceleration Gs is greater than or equal to a predetermined deceleration gx". Here, the deceleration change amount dG is calculated by time-differentiating the required deceleration Gs based on the required deceleration Gs. Further, the predetermined amount of change dx and the predetermined deceleration gx are threshold values for determination and are preset constants. If "dG≧dx and Gs≧gx" and the result of step S135 is affirmative (during emergency braking), the process proceeds to step S140. If "dG<dx or Gs<gx" and the step S135 is negative (during normal braking), the process proceeds to step S185.

At step S140, the elapsed time Tk from the start of the automatic braking control in an emergency is calculated. At step S150, it is determined whether or not the elapsed time Tk is less than the predetermined time tx. If "Tk<tx", the process proceeds to step S160. In step S160, the rear wheel inlet valves VIk and VIl are fully energized, and the rear wheel inlet valves VIk and VIl are placed in the fully closed position (blocked state). At step S170, the electric motor ML is driven. Then, based on the first and second target hydraulic pressures Pt1 and Pt2, the first and second adjustment hydraulic pressures Pp1 and Pp2 (first and second hydraulic pressures) are adjusted to the first and second target hydraulic pressures Pt1 and Pt2. The first and second pressure regulating valves UP1 and UP2 are controlled so as to approach and match. That is, the first and second hydraulic pressures (actual hydraulic pressures) Pp1 and Pp2 are adjusted by the first and second pressure regulating valves UP1 and UP2. It should be noted that, if emergency braking is determined in step S135, the electric motor ML is driven at its maximum output so that the rotational speed increases rapidly.

When "Tk≧tx" is established in step S180, the amount of energization to the rear wheel inlet valves VIk and VIl is gradually reduced as the elapsed time Tk elapses. Since the rear wheel inlet valves VIk and VIl are gradually opened, the adjusted hydraulic pressure Pp is introduced into the left and right rear wheel cylinders CWk and CWl, and the rear wheel braking hydraulic pressures Pwk and Pwl are adjusted to the first and second It is gradually increased until it matches the second adjustment hydraulic pressure Pp1, Pp2.

In step S185, since the automatic braking control is performed in the regular braking region, the rear wheel inlet valves VIk and VIl are not energized, and the rear wheel inlet valves VIk and VIl are maintained in the fully open position. Since it is not emergency braking, the adjustment hydraulic pressure Pp is supplied to all the wheel cylinders CW.

In the automatic braking device JS that operates not only during emergency braking but also during normal braking, at the start of emergency braking (during sudden braking), the rear wheel inlet valves VIk and VIl are fully energized, The wheel inlet valves VIk and VIl are fully closed to prevent the rear wheel brake hydraulic pressures Pwk and Pwl from increasing. As the elapsed time Tk elapses, the rear wheel inlet valves VIk and VIl are gradually opened from the fully closed state, and the rear wheel brake fluid pressures Pwk and Pwl are increased.

<Operation of Second Processing Example of Automatic Braking Control>
The configuration of the automatic braking device JS in the second processing example is the same as that in the first processing example. The difference is that the controller ECU determines "whether or not the braking is sudden" based on the requested deceleration Gs. When the sudden braking is not determined, the right rear wheel and left rear wheel inlet valves VIk and VIl are not energized, and the first and second pressure regulating valves UP1 and UP2 are increased in energization for automatic braking. Control is initiated (activation of service brakes). On the other hand, when sudden braking is determined, the right rear wheel and left rear wheel inlet valves VIk and VIl are energized, and the energization of the first and second pressure regulating valves UP1 and UP2 is increased to automatically Braking control is started (activation of emergency braking).

The operation of the second processing example of the automatic braking control will be described with reference to the time series diagram of FIG. As in the case of the first processing example, it is assumed that the driver does not operate the braking operation member BP (that is, when "Ba=0"). The emergency braking of the automatic braking control is represented by the characteristic Cx (indicated by the solid line) in each diagram.

Before time u0, the automatic braking control has not been started and "Gs=0". Therefore, the target hydraulic pressure Pt (result, the regulated hydraulic pressure Pp) is "0", and each inlet valve VI is de-energized and fully opened. At time u0, automatic braking control (first, normal braking) is started. The electric motor ML is started to rotate and the target hydraulic pressure Pt is increased from "0" according to the required deceleration Gs. Energization of the pressure regulating valve UP is started, and the regulating hydraulic pressure Pp begins to increase from "0". In the diagram, the target hydraulic pressure Pt and the adjusted hydraulic pressure Pp overlap. Since each inlet valve VIi-VIj is in the open position, each braking fluid pressure Pwi-Pwl is increased from "0".

At time u1, the conditions that "the deceleration change amount dG (differential value of the required deceleration Gs) is a predetermined change amount dx or more" and "the required deceleration Gs is a predetermined deceleration gx or more" are satisfied, and the automatic Emergency braking is determined in the braking control and is started. At time u1, the front inlet valves VIi, VIj for the front wheel cylinders CWi, CWj remain de-energized (i.e., open), and the rear inlet valves VIk, for the rear wheel cylinders CWk, CWl, "Duk, Dul=100%" is instructed to VIl, and full energization is performed. As a result, the rear wheel inlet valves VIk and VIl are completely closed, so that the left and right rear wheel cylinders CWk and CWl are no longer supplied with the first and second regulating hydraulic pressures Pp1 and Pp2. Although the front wheel brake fluid pressures Pwi and Pwj are rapidly increased, the rear wheel brake fluid pressures Pwk and Pwl are maintained at the value pb. Then, the accumulation of the elapsed time Tk is started from the emergency braking determination time (start time) u1.

At time u2, elapsed time Tk reaches predetermined time tx. From the time point u2, the rear wheel duty ratios Duk, Dul are gradually decreased at the gradient Kg, and the rear wheel inlet valves VIk, VIl begin to be gradually opened. Then, since the first and second adjustment hydraulic pressures Pp1 and Pp2 start to be introduced into the rear wheel cylinders CWk and CWl, the rear wheel braking hydraulic pressures Pwk and Pwl are gently increased from the value pb. At time point u3, "Duk, Dul=0% (corresponding to the fully open position of the rear wheel inlet valves VIk, VIl)", and the rear wheel brake fluid pressures Pwk, Pwl are equal to the front wheel brake fluid pressures Pwi, Pwj (=pa). (that is, it becomes a regular allocation).

The second processing example also has the same effects as the first processing example. At the beginning of the emergency braking (rapid braking) of the automatic braking control (between time u1 and time t2), the rear wheel cylinders CWk and CWl are supplied with the first and second adjustment hydraulic pressures Pp1 and Pp2. First, since the adjustment hydraulic pressure Pp is supplied only to the front wheel cylinders CWi and CWj, the entire amount of the brake fluid BF discharged by the fluid pump QL is supplied to the front wheel cylinders CWi and CWj. As a result, the front wheel brake fluid pressures Pwi and Pwj increase in response are improved, and the vehicle is efficiently decelerated. In addition, since an increase in the rear wheel brake fluid pressures Pwk and Pwl is suppressed at the beginning of the emergency control, a sufficient lateral force can be obtained from the rear wheels WHk and WHl even when the vehicle is deflected. Therefore, a stabilizing moment is secured to suppress the wobbling of the vehicle, and the directional stability of the vehicle is improved. As a result, the driver is prevented from feeling discomfort due to vehicle deflection.

Furthermore, based on the elapsed time Tk, the energization of the rear wheel inlet valves VIk and VIl is gradually reduced from time u2 to time u3. As a result, the rear wheel braking hydraulic pressures Pwk and Pwl are gradually increased, and sufficient vehicle deceleration can be ensured. In other words, in the initial stage of the start of emergency braking by automatic braking control, vehicle deflection is suppressed and vehicle deceleration is efficiently achieved, and as automatic braking control continues, sufficient vehicle deceleration is achieved. can be secured.

It should be noted that the characteristic Cy (indicated by the dashed-dotted line) in each diagram shows the normal braking of the automatic braking control (when the process of step S135 is denied). In this regular braking, the rear wheel inlet valves VIk and VIl are not energized (see the process of step S185). Therefore, when the driver does not perform a braking operation, the target hydraulic pressure Pt is determined based on the required deceleration Gs, and the braking hydraulic pressure Pw of each wheel cylinder CW is controlled by the pressure regulating valve UP. controlled by Pp.

JS...Automatic braking device, BP...Brake operation member, CM...Master cylinder, CW...Wheel cylinder, UP1, UP2 (=UP)...First and second pressure regulating valves, VI...Inlet valve, VO...Outlet valve, ECU... Controller, Pt1, Pt2 (=Pt) First and second target hydraulic pressures Pp1, Pp2 (=Pp) First and second adjustment hydraulic pressures (first and second hydraulic pressures) Pm1, Pm2 (= Pm)... 1st, 2nd master cylinder liquid pressure, Tk... Elapsed time.

Claims (3)

It is provided in a vehicle that adopts a diagonal system as two braking systems, and increases the hydraulic pressure of the wheel cylinder from the hydraulic pressure of the master cylinder based on the required deceleration according to the distance between the vehicle and an object in front of the vehicle. An automatic braking device for a vehicle that executes automatic braking control to
a first pressure regulating valve that adjusts a first hydraulic pressure of a first braking system connected to the wheel cylinders of the right front wheel and the left rear wheel among the two braking systems;
a second pressure regulating valve that adjusts a second hydraulic pressure of a second braking system connected to the left front wheel and right rear wheel cylinders of the two braking systems;
a normally open left rear wheel inlet valve provided for the left rear wheel cylinder;
a normally open right rear wheel inlet valve provided for the right rear wheel cylinder;
Based on the required deceleration, energization to the first and second pressure regulating valves is controlled to adjust the first and second hydraulic pressures, and energization to the right rear wheel and left rear wheel inlet valves. a controller that controls the
with
The controller is
Until the elapsed time from the start of the automatic braking control reaches a predetermined time, the right rear wheel and left rear wheel inlet valves are closed , and the automatic braking control is executed by the first and second pressure regulating valves. , the automatic braking device of the vehicle. It is provided in a vehicle that adopts a diagonal system as two braking systems, and increases the hydraulic pressure of the wheel cylinder from the hydraulic pressure of the master cylinder based on the required deceleration according to the distance between the vehicle and an object in front of the vehicle. An automatic braking device for a vehicle that executes automatic braking control to
a first pressure regulating valve that adjusts a first hydraulic pressure of a first braking system connected to the wheel cylinders of the right front wheel and the left rear wheel among the two braking systems;
a second pressure regulating valve that adjusts a second hydraulic pressure of a second braking system connected to the left front wheel and right rear wheel cylinders of the two braking systems;
a normally open left rear wheel inlet valve provided for the left rear wheel cylinder;
a normally open right rear wheel inlet valve provided for the right rear wheel cylinder;
Based on the required deceleration, energization to the first and second pressure regulating valves is controlled to adjust the first and second hydraulic pressures, and energization to the right rear wheel and left rear wheel inlet valves. a controller that controls the
with
The controller is
Based on the required deceleration, determine whether or not sudden braking,
When the sudden braking is not determined, the right rear wheel and left rear wheel inlet valves are opened , and the automatic braking control is executed by the first and second pressure regulating valves,
When the sudden braking is determined, the right rear wheel and left rear wheel inlet valves are closed until the elapsed time from the start of the automatic braking control reaches a predetermined time. An automatic braking device for a vehicle, wherein the automatic braking control is executed by a second pressure regulating valve. In the automatic braking device for a vehicle according to claim 1 or claim 2,
An automatic braking device for a vehicle, wherein the controller opens the right rear wheel inlet valve and the left rear wheel inlet valve when the elapsed time reaches the predetermined time.

Images