JP2020111115A - Automatic braking device of vehicle - Google Patents

Abstract

To provide an automatic braking device of a vehicle, which can reduce a feeling of strangeness given to a driver in automatic braking control to suppress a vehicle from being deflected.SOLUTION: The automatic braking device employs a diagonal-type braking system. The device comprises; a first pressure-adjusting valve that adjusts first liquid pressure of a first braking system connected to right front wheel- and left rear wheel-wheel cylinders; a second pressure-adjusting valve that adjusts second liquid pressure of a second braking system connected to left front wheel- and right rear wheel-wheel cylinders; a regularly-open type left rear wheel-inlet valve provided for the left rear wheel-wheel cylinder; a regularly-open type right rear wheel-inlet valve provided for the right rear wheel-wheel cylinder; and a controller that controls energization to the first and second pressure-adjusting valves so that the first and second liquid pressure are adjusted based on required deceleration and controls energization to the right rear wheel- and the left rear wheel-inlet valves. The controller performs energization to the right rear wheel- and the left rear wheel-inlet valves and increases energization to the first and second adjustment valves to start automatic braking control.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a vehicle automatic braking device.

In Patent Document 1, for the purpose of "maximizing the braking force while appropriately adjusting the braking force distribution of the wheels when there is a possibility of collision with an obstacle," When a determination unit that determines whether there is a possibility of collision with an object, and when the determination unit determines that there is a possibility of a collision, the brake fluid pressure acting on each wheel is increased to control the wheel. A braking force control device including: an automatic braking control unit that executes 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. When the determination unit determines that there is a possibility of collision, the braking force distribution control unit compares the braking fluid with the brake fluid compared to the case where the determination unit determines that there is no possibility of collision. The braking force distribution control unit controls the braking force distribution so as to keep the pressure at a large value, and the braking force distribution control unit determines, if the determination unit determines that there is a possibility of collision, the determination unit determines the possibility of collision. The braking force distribution is controlled so that the brake fluid pressure of the rear wheels is maintained at a large value as compared with the case where it is determined that there is no brake pressure”.

In Patent Document 2, for the purpose of "improving the posture stability of the vehicle at the time of automatic brake control", "an automatic brake that automatically generates a braking force on the wheels of the vehicle irrespective of the driver's brake operation. A brake device for controlling, wherein first and second brake hydraulic circuits for transmitting hydraulic pressure from a master cylinder to the left and right front wheel cylinders, respectively, and the wheel cylinders provided in the brake hydraulic circuit. A brake actuator that can individually adjust the hydraulic pressure supplied to the vehicle, a brake controller that controls the brake actuator to individually control the braking force of each front wheel, and detects the behavior of the vehicle in the yaw direction. The brake actuator includes a pump that pressurizes the hydraulic pressure of each brake hydraulic circuit at the time of automatic brake control, and a pressure regulating valve that individually adjusts the hydraulic pressure of each brake hydraulic circuit. Then, the brake control unit increases the hydraulic pressure supplied to the wheel cylinder having the lower braking force among the front wheels, based on the behavior in the yaw direction detected by the behavior detection sensor during the automatic brake control. To control the pressure regulating valve as described above.

In the device of Patent Document 1, it is determined whether or not the own vehicle may collide with an obstacle, and when it is determined that there is a possibility of collision, it is determined that there is no possibility of collision. By comparison, the braking force distribution is performed such that the braking hydraulic pressure of the rear wheels is maintained at a large value. That is, the front-rear distribution of the braking force is shifted toward the rear wheel, and the rear-wheel braking force is increased.

By the way, in a wheel (tire), 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, when the vehicle is deflected and a side slip angle is generated on the rear wheel, the rear wheel lateral force is less generated. That is, a lateral force of the rear wheels generates a yaw moment (also referred to as a “stabilizing moment”) in a direction that suppresses vehicle deflection.

In a vehicle in which a diagonal hydraulic type (also referred to as “X type”) is adopted as a two-system brake hydraulic circuit (braking system) like the device of Patent Document 2, the left and right front wheels are affected by variations in the accuracy of the pressure regulating valve. A difference in braking force may occur, which may cause vehicle deflection. In the device of Patent Document 2, in order to suppress this vehicle deflection, during automatic brake control, the hydraulic pressure supplied to the wheel cylinder with the lower braking force is adjusted based on the behavior in the yaw direction. The 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 occurring at this time. ..

For the above-mentioned reason, it is desired that the automatic braking device that executes the automatic braking control can appropriately suppress the vehicle deflection without causing the driver to feel uncomfortable.

Japanese Unexamined Patent Publication No. 2018-062273 JP, 2017-149378, A

An object of the present invention is to provide an automatic braking device for a vehicle having a diagonal braking system, which can reduce a driver's discomfort and can favorably suppress vehicle deflection.

The automatic braking system for a vehicle is applied to a vehicle that adopts a diagonal system as two braking systems. The automatic braking device sets the hydraulic pressure (Pw) of the wheel cylinder (CW) to the master cylinder (CM) based on the required deceleration (Gs) according to the distance (Ob) between the object in front of the vehicle and the vehicle. For executing the automatic braking control that increases from the hydraulic pressure (Pm) of the first braking system, which is “the first braking system connected to the front right wheel and the rear left wheel cylinder (CWi, CW1) of the two braking systems. A first pressure regulating valve (UP1) for adjusting the first hydraulic pressure (Pp1) of (H1)" and "the left front wheel and the right rear wheel wheel cylinders (CWj, CWk) of the two braking systems are connected. A second pressure regulating valve (UP2) for adjusting the second hydraulic pressure (Pp2) of the second braking system (H2)", and the "normally open left rear wheel provided for the left rear wheel wheel cylinder (CWl)" "Inlet valve (VIl)", "a normally open right rear wheel inlet valve (VIk) provided for the right rear wheel wheel cylinder (CWk)", and "based on the required deceleration (Gs), The first and second hydraulic pressures (Pp1, Pp2) are adjusted by controlling the energization of the first and second pressure regulating valves (UP1, UP2), and the right rear wheel and left rear wheel inlet valves ( And a controller (ECU) for controlling energization to VIk, VIl).

In the automatic braking device for a vehicle, the controller (ECU) energizes the right rear wheel and the left rear wheel inlet valves (VIk, VIl) to connect the first and second pressure regulating valves (UP1, UP2). The energization is increased and the automatic braking control is started.

According to the above configuration, when the automatic braking control is started, an increase in the braking hydraulic pressures Pwk, Pwl of the rear wheel cylinders CWk, CW1 is suppressed, so that even if the vehicle is deflected, The lateral forces of the wheels WHk and WHl are sufficiently secured, and the directional stability of the vehicle is improved.

Further, in the automatic braking device for a vehicle, the controller (ECU) determines "whether or not it is a sudden braking" based on the required deceleration (Gs). Without energizing the rear wheels and the left rear wheel inlet valves (VIk, VIl), the energization of the first and second pressure regulating valves (UP1, UP2) is increased to start the automatic braking control. When a sudden braking is determined, the right rear wheel and left rear wheel inlet valves (VIk, VIl) are energized, and the first and second pressure regulating valves (UP1, UP2) are energized. Then, the automatic braking control is started.

According to the above configuration, even when the automatic braking control operates in the normal braking (service braking) region as well, when the emergency automatic braking control is started, the braking of the rear wheel wheel cylinders CWk, CW1 is performed. Since the increase of the hydraulic pressures Pwk and Pwl is suppressed, even if the vehicle is deflected, the lateral force of the rear wheels WHk and WHl is sufficiently secured, and the directional stability of the vehicle is improved.

It is a whole lineblock diagram for explaining an embodiment of automatic braking device JS of vehicles. It is a functional block diagram for explaining a calculation processing in driving support controller ECJ and a braking controller ECU. It is a flow chart for explaining the 1st example of automatic braking control. It is a time series diagram for explaining operation of the 1st example of automatic braking control. It is a flow figure for explaining the 2nd example of automatic braking control. It is a time-series diagram for demonstrating operation|movement of the 2nd example of automatic braking control.

<Symbols of components, subscripts at the end of the symbol, and movement/movement direction>
In the description below, components such as “ECU” and the like, components, calculation processes, signals, characteristics, and values having the same symbol have the same function. The suffixes "i" to "l" added to the end of various symbols are comprehensive symbols indicating which wheel they belong 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, in each of the four wheel cylinders, the right front wheel wheel cylinder CWi, the left front wheel wheel cylinder CWj, the right rear wheel wheel cylinder CWk, and the left rear wheel wheel cylinder CWl are described. Furthermore, the subscripts "i" to "l" at the end of the symbols can be omitted. When the subscripts "i" to "l" are omitted, each symbol represents a generic name of each of the four wheels. For example, "WH" represents each wheel and "CW" represents each wheel cylinder.

The subscripts "1" and "2" added to the end of each symbol are comprehensive symbols indicating which one of the two braking systems (diagonal type braking system). Specifically, "1" indicates the first system and "2" indicates the second system. For example, the two master cylinder fluid passages are referred to as a first master cylinder fluid passage HM1 and a second master cylinder fluid passage HM2. Furthermore, the subscripts "1" and "2" at the end of the symbol can be omitted. When the subscripts "1" and "2" are omitted, each symbol represents a generic name 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 device 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 the master cylinder fluid passage HM and the wheel cylinder fluid passage HW. The fluid passage is a passage for moving the brake fluid BF that is the working fluid of the automatic braking device JS, and corresponds to a brake pipe, a fluid unit flow passage, a hose, and the like. The inside of the fluid path is filled with the braking fluid BF. In the fluid path, the side closer to the master cylinder CM is called "upper side", and the side closer to the wheel cylinder CW is called "lower side".

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

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

The 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 hydraulic pressure (braking hydraulic pressure) Pw of the wheel cylinder CW is adjusted, the braking torque Tq of the wheel WH is adjusted, and the braking force is generated on the wheel WH.

A rotating member (for example, a brake disc) KT is fixed to a wheel WH of the vehicle. Then, the brake caliper is arranged so as to sandwich the rotating member KT. The brake caliper is provided with a wheel cylinder CW, and the friction member (for example, a brake pad) is pressed against the rotating member KT by increasing the pressure (braking liquid pressure) Pw of the brake fluid BF inside thereof. Since the rotating member KT and the wheel WH are fixed so as to rotate integrally, the braking torque Tq is generated on the wheel WH by the frictional force generated at this time. The braking torque Tq causes a deceleration slip on the wheels WH, resulting in a braking force.

The master reservoir (atmospheric pressure reservoir, also simply referred to as “reservoir”) RV is a tank for the working liquid, and the braking liquid BF is stored therein. 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 a tandem type, and the inside thereof is divided into first and second master cylinder chambers Rm1 and Rm2 by master pistons PL1 and PL2. When the braking operation member BP is not operated, the master cylinder chambers Rm1 and Rm2 of the master cylinder CM and the reservoir RV are in communication with each other. First and second master cylinder fluid passages HM1 and HM2 are connected to the master cylinder CM. When the braking operation member BP is operated, the master pistons PL1 and PL2 move forward, and the two master cylinder chambers Rm1 and Rm2 are shut off from the reservoir RV. When the operation of the braking operation member BP is increased, the braking fluid BF is pressure-fed from the master cylinder CM to the wheel cylinders CWi to CW1 via the master cylinder fluid passages HM1 and HM2.

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

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

The steering operation member (for example, a steering wheel) is provided with a steering angle sensor SA so as to detect the steering angle Sa. The vehicle body of the vehicle is provided with a yaw rate sensor YR so as to detect a yaw rate (yaw angular velocity) Yr. Further, a longitudinal acceleration sensor GX and a lateral acceleration sensor GX are provided so as to detect acceleration (longitudinal acceleration) Gx in the front-rear direction (travel direction) and acceleration (lateral acceleration) Gy in the lateral direction (direction perpendicular to the traveling direction) of the vehicle. 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 so as to detect the operation amount Ba of the 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 a hydraulic pressure (master cylinder hydraulic pressure) Pm in the master cylinder CM, an operational displacement sensor SP that detects an operational displacement Sp of the braking operation member BP, and a braking operation. At least one of the operating force sensors FP that detects the operating force Fp of the operating member BP is adopted. 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.

The signals such as the wheel speed Vw, the steering angle Sa, the yaw rate Yr, the longitudinal acceleration (deceleration) Gx, the lateral acceleration Gy, and the braking operation amount Ba (Pm, Sp, Fp) detected by the sensors (VW, etc.) described above are , Is input to the braking controller ECU.

The vehicle is equipped with a driving support system so as to avoid a collision with an obstacle or reduce the damage at the time of the collision. The driving support system includes a distance sensor OB and a driving support controller ECJ. The distance sensor OB detects a distance (relative distance) Ob between an object existing in front of the host vehicle (another vehicle, a fixed object, a person, a bicycle, etc.) and the host vehicle. For example, a camera, a radar or the like is adopted as the distance sensor OB. The relative distance Ob is input to the driving support controller ECJ. The driving assist controller ECJ calculates the required deceleration Gs based on the relative distance Ob. The required deceleration Gs is a target value of the vehicle deceleration for avoiding the vehicle from hitting an object. The required deceleration Gs is transmitted to the braking controller ECU via the communication bus BS.

<<Brake controller ECU>>
The automatic braking device JS includes a braking controller ECU and a fluid unit HU. The braking controller (also referred to as “electronic control unit”) ECU includes an electric circuit board on which a microprocessor MP and the like are mounted and a control algorithm programmed in the microprocessor MP. The braking controller ECU is network-connected to another controller (driving support controller ECJ or the like) through the communication bus BS so as to share signals (detection value, calculated value, etc.) via the vehicle-mounted communication bus BS. For example, the braking controller ECU calculates the vehicle body speed Vx and transmits it to the driving support controller ECJ. On the other hand, from the driving support controller ECJ to the braking controller ECU, the required deceleration Gs (target value) for executing automatic braking control (braking control for avoiding collision with an obstacle or reducing collision damage). Will be 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 fluid unit HU and three different types of solenoid valves UP, VI, VO. Specifically, drive signals Up, Vi, Vo for controlling the various solenoid valves UP, VI, VO are calculated based on a control algorithm in the microprocessor MP. Similarly, the drive signal Ml for controlling the electric motor ML, which is the drive source of the electric pump DL, is calculated.

The braking controller ECU is provided with a drive circuit DR for driving the solenoid valves UP, VI, VO and the electric motor ML. In the drive circuit DR, a bridge circuit is formed by switching elements (power semiconductor devices such as MOS-FETs and IGBTs) so as to drive the electric motor ML. The energization state of each switching element is controlled based on the motor drive signal Ml, and the output of the electric motor ML is controlled. Further, in the drive circuit DR, the energized state (that is, the excited state) of these is controlled by the switching element based on the drive signals Up, Vi, Vo so as to drive the solenoid valves UP, VI, VO. The drive circuit DR is provided with an electric motor ML and an energization amount sensor that detects the actual energization amount of the solenoid valves UP, VI, VO. For example, a current sensor is provided as the energization amount sensor, and the current value (energization amount) supplied to the electric motor ML and the solenoid valves UP, VI, VO is detected.

<<Fluid unit HU>>
The fluid unit HU is connected to the first and second master cylinder fluid passages HM1 and HM2. At the portions Bt1 and Bt2 (branch 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 HW1 and connected to the four wheel cylinders CWi to CW1. It Here, the braking system connected to the right front wheel and the left rear wheel wheel cylinders CWi, CWl is referred to as "first braking system H1". The braking system connected to the left front wheel and the right rear wheel wheel cylinders CWj, 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 the left rear wheel wheel cylinder fluid passages HWi and HW1 at the first branch portion Bt1. The right front wheel and the left rear wheel wheel cylinders CWi and CWl are connected to the right front wheel and the left rear wheel wheel cylinder fluid paths HWi and HWl. Similarly, in the second braking system H2, the second master cylinder fluid passage HM2 is branched into the left front wheel and the right rear wheel wheel cylinder fluid passages HWj and HWk at the second branch portion Bt2. The left front wheel and the right rear wheel wheel cylinders CWj and CWk are connected to the left front wheel and the right rear wheel wheel cylinder fluid passages HWj and HWk, respectively. That is, the vehicle employs a diagonal (X-type) braking system having the first braking system H1 (=HM1+HWi, HWl) and the second braking system H2 (=HM2+HWj, HWk).

The fluid unit HU includes 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 passages HM1 and HM2 (=HM). As the pressure regulating valve UP, a linear solenoid valve (also referred to as “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 the first and second pressure regulating valve drive signals Up1 and Up2 (=Up). Here, normally open solenoid valves are used 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 first and second fluid pumps QL1 and QL2 are integrally rotated and driven by the electric motor ML. The first and second suction parts Bs1 located 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, the braking fluid BF is pumped up. The pumped brake fluid BF is discharged to the first and second discharge parts 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 of the automatic braking control (for example, the target hydraulic pressure Pt), and the drive signal Up is determined based on this. Then, the amount of electricity (current) to the pressure regulating valve UP is adjusted according to the drive signal Up, 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 braking fluid BF) of “Bs→RL→QL→Bt→UP→Bs” is formed. When the pressure regulating valve UP is not energized and the normally open type pressure regulating valve UP is in the fully open state, the hydraulic pressure at the upper portion of the pressure regulating valve UP (that is, the master cylinder hydraulic pressure Pm) and the lower portion of the pressure regulating valve UP are set. And the actual hydraulic pressure Pp (referred to as “adjusted hydraulic pressure”).

The energization amount to the normally open first and second pressure regulating valves UP1 and UP2 is increased, and the valve opening amount is decreased. The first and second pressure regulating valves UP1 and UP2 restrict the recirculation of the braking fluid BF, and the orifice effect causes the first and second adjustment fluid pressures (actual fluid pressures) Pp1 and Pp2 (“the first and second fluid pressures”). "=Pp") is increased from the first and second master cylinder hydraulic pressures Pm1 and Pm2 (=Pm) (hence "Pp>Pm"). That is, the electric pump DL and the pressure regulating valve UP adjust the differential pressure between the master cylinder hydraulic pressure Pm and the adjusted hydraulic pressure Pp. By controlling the electric pump DL and the pressure regulating valve UP, the adjusted hydraulic pressure Pp (as a result, 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 braking operation member BP. Will be increased. For example, when the braking operation member BP is not operated, “Pm=0”, but the braking hydraulic pressure Pw is increased 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 (on the side closer to the master cylinder CM) so as to detect the first and second master cylinder hydraulic pressures Pm1 and Pm2. Note that, basically, since "Pm1=Pm2", one of the first and second master cylinder hydraulic pressure sensors PM1 and PM2 can be omitted.

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

The first braking system H1 includes a first master cylinder fluid passage HM1, right front wheels, left rear wheel wheel cylinder fluid passages HWi, HWl, and a first master cylinder chamber Rm1 and right front wheels and left rear wheel cylinders. Connect CWi and CW1. The right front wheel and the left rear wheel inlet valves VIi and VIl are provided in the right front wheel and the left rear wheel wheel cylinder fluid passages HWi and HWl branched from the first master cylinder fluid passage HM1. That is, the right front wheel and the left rear wheel inlet valves VIi and VIl are provided between the branch portion Bt1 and the right front wheel and the left rear wheel wheel cylinders CWi and CWl in the first braking system H1. In other words, the first braking system H1 is provided with the normally open right front wheel for the right front wheel, the left rear wheel wheel cylinders CWi, CW1, and the left rear wheel inlet valve VIi, VIl.

Similarly, the second braking system H2 is composed of a second master cylinder fluid passage HM2, left front wheels, right rear wheel wheel cylinder fluid passages HWj, HWk, and a second master cylinder chamber Rm2 and left front wheels, right rear. The wheel cylinders CWj and CWk are connected. The left front wheel and the right rear wheel inlet valves VIj, VIk are provided in the left front wheel and the right rear wheel wheel cylinder fluid passages HWj, HWk branched from the second master cylinder fluid passage HM2. That is, the left front wheel and the right rear wheel inlet valves VIj, VIk are provided between the branch portion Bt2 and the left front wheel, the right rear wheel wheel cylinders CWj, CWk in the second braking system H2. In other words, the second braking system H2 is provided with the left front wheel, the right rear wheel wheel cylinders CWj, the normally open left front wheel for the CWk, and the right rear wheel inlet valves VIj, VIk.

Each wheel cylinder fluid path HW is connected to the low pressure reservoir RL via a normally closed outlet valve VO at the lower portion of the inlet valve VI (between the inlet valve VI and the wheel cylinder CW). The fluid passage that connects the wheel cylinder fluid passage HW and the low pressure reservoir RL is referred to as "reservoir fluid passage HR". Therefore, each outlet valve VO is provided in each reservoir fluid passage HR.

A normally open type on/off solenoid valve is adopted as the inlet valve VI. Here, the "on/off solenoid valve" is a 2-port 2-position switching type solenoid valve having two positions, an open position and a closed position. In the normally open inlet valve VI, the open position and the 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 ON time (energization time) of a pulse in a pulse train that continues at a constant cycle. Since the inlet valve VI is a normally open type, it is in a fully open state when not energized (that is, when the duty ratio is “0%”) and fully energized (that is, when the duty ratio Du is “100%”). In the case), it is fully closed. Then, by adjusting the duty ratio Du between 0% and 100%, the open state of the inlet valve VI can be adjusted.

As the outlet valve VO, a normally closed on/off solenoid valve is adopted. Even in the normally closed outlet valve VO, the open position and the closed position are selectively realized. Similar 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 a normally closed type, it is fully closed when not energized (Du=0%) and fully opened when fully energized (Du=100%). By adjusting the duty ratio Du between 0% and 100%, the open state (closed state) of the outlet valve VO can be adjusted.

In the inlet valve VI and the outlet valve VO, the configuration related to each wheel WH is the same. 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 adopted 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 may be used as the inlet valve VI. In this case, the valve opening amount of the inlet valve VI is controlled by the amount of electricity supplied to the inlet valve VI (supply current), like the pressure regulating valve UP.

For example, in the anti-skid control, in order 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. Further, since the braking hydraulic pressure Pw is increased, the inlet valve VI is opened and the outlet valve VO is closed. The outflow of the braking fluid BF to the low pressure reservoir RL is blocked, the adjustment fluid pressure Pp adjusted by the pressure adjustment valve UP is introduced into the wheel cylinder CW, and the braking fluid pressure Pw is increased. Further, in order to maintain the hydraulic pressure (braking hydraulic pressure) Pw in the wheel cylinder CW, both the inlet valve VI and the outlet valve VO are closed.

<Operation processing in the driving support controller ECJ and the braking controller ECU>
With reference to the functional block diagram of FIG. 2, the arithmetic processing in the driving support controller ECJ and the braking controller ECU will be described. The driving assist controller ECJ calculates the required deceleration Gs in the automatic braking control. The required deceleration Gs is transmitted to the braking controller ECU via the communication bus BS. The braking controller ECU controls the fluid unit HU (ML, UP, etc.) so as to adjust the braking fluid pressure Pw (that is, the braking torque Tq) of each wheel WH based on the required deceleration Gs.

In the vehicle, the distance (relative distance) Ob between the object (another vehicle, a fixed object, a bicycle, a person, an animal, etc.) existing ahead of the vehicle and the vehicle is detected. A distance sensor OB is provided. For example, a camera, a radar or the like is used as the distance sensor OB. 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 support controller ECJ includes a collision margin time calculation block TC, a vehicle head time calculation block TW, and a required deceleration calculation block GS.

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

In the vehicle head time calculation block TW, the vehicle head time Tw is calculated based on the relative distance Ob and the vehicle body speed Vx. The headway time Tw is the time until the vehicle reaches the current position of the object ahead. Specifically, the headway time Tw is calculated by dividing the relative distance Ob by the vehicle body speed Vx. When the object ahead of the host vehicle is stationary, the collision margin time Tc and the headway time Tw match. The vehicle speed Vx is acquired from the vehicle speed calculation block VX of the braking controller ECU via the communication bus BS.

In the required deceleration calculation block GS, the required deceleration Gs is calculated based on the collision margin time Tc and the vehicle head time Tw. The required deceleration Gs is a target value of the deceleration of the host vehicle for avoiding a collision between the host vehicle and a front object. The required deceleration Gs is calculated according to the calculation map Zgs such that the larger the collision margin time Tc is, the smaller it is (or the smaller the collision margin time Tc is, the larger it is). Further, the required deceleration Gs can be adjusted based on the headway time Tw. The required deceleration Gs is adjusted based on the vehicle head time Tw so that the required deceleration Gs becomes smaller as the vehicle head time Tw becomes larger (or the required deceleration Gs becomes larger as the vehicle head time Tw becomes smaller). .. The required 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 so as to detect the rotation speed (wheel speed) Vw of the wheel WH. The detected wheel speed Vw is input to the braking controller ECU. The braking 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.

In the vehicle speed calculation block VX, the vehicle speed Vx is calculated 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 of the four wheel speeds Vw (slowest wheel speed). During braking, the vehicle body speed Vx is calculated based on the fastest one of the four wheel speeds Vw (the fastest wheel speed). Further, in the calculation of the vehicle body speed Vx, a limit may be set on the time change amount. That is, the upper limit value αup of the increasing gradient of the vehicle body speed Vx and the lower limit value αdn of the decreasing gradient are set, and the change of the vehicle body speed Vx is restricted by the upper and lower limit values αup, αdn. The calculated vehicle speed Vx is transmitted to the headway time calculation block TW of the driving support controller ECJ via the communication bus BS.

The actual deceleration calculation block GA calculates the actual deceleration Ga based on the vehicle body speed Vx. The actual deceleration Ga is the deceleration (negative acceleration) in the front-rear direction (travel direction) of the vehicle that is actually occurring. Specifically, the vehicle speed Vx is time-differentiated to calculate the actual deceleration Ga. Further, the longitudinal acceleration (deceleration) Gx is adopted for the calculation of the actual deceleration Ga. In this case, the longitudinal acceleration Gx (detection 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 traveling road surface. Therefore, for the calculation of the actual deceleration Ga, the differential value of the vehicle body speed Vx is preferable to the longitudinal acceleration Gx. Further, the actual vehicle deceleration Ga may be calculated based on the differential value (calculated value) of the vehicle body speed Vx and the longitudinal acceleration Gx (detected value) so as to improve the robustness.

In the automatic braking control block JC, automatic braking control is executed based on the required deceleration Gs and the actual deceleration Ga. First, in the automatic braking control block JC, the necessity of automatic braking is determined. When the driver has already operated the braking operation member BP and the actual deceleration Ga is higher than the required deceleration Gs, the automatic braking control is not necessary. On the other hand, when the actual deceleration Ga is smaller than the required deceleration Gs, the 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.

In the target hydraulic pressure calculation block PT, the first and second target hydraulic pressures Pt1, Pt2 (=Pt) are calculated based on the required deceleration Gs and the preset calculation map. The first target hydraulic pressure Pt1 is a target for the adjusted hydraulic pressure Pp1 of the first braking system H1 connected to the front right wheel cylinder CWi (which is the “first hydraulic pressure actual value” and corresponds to the “first hydraulic pressure”). It is a value. Further, 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 (the “actual second hydraulic pressure value”, which corresponds to the “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"). The specifications of the vehicle (mass, height of the center of gravity, etc.) and the specifications of the braking device (the effective braking radius of the rotating member KT, the friction coefficient of the friction material, the pressure receiving area of the wheel cylinder CW, etc.) are known, so the above calculation map Then, using these specifications, it is determined that the first and second target hydraulic pressures Pt1 and Pt2 increase as the required deceleration Gs increases.

The elapsed time calculation block TK calculates the elapsed time Tk from the time when the automatic braking control is started. As will be described later, the elapsed time Tk is a front-rear distribution of the braking force (contribution of the front-rear wheels to the total braking force acting on the vehicle) so that the deflection of the vehicle can be suppressed when the automatic braking control is executed. Used to adjust the.

In the drive signal calculation block DS, the motor drive signal Ml, the pressure regulating valve drive signal Up, and the inlet valve/outlet valve drive signals Vi and Vo are calculated. For example, the target rotation speed of the electric motor ML is determined based on the target hydraulic pressure Pt, and the drive signal Ml (current instruction) for instructing the energization amount (current value) to the electric motor ML so that the target rotation speed is achieved. Value) is calculated. Further, the electric motor ML may be driven at a preset constant number of rotations. In this case, an ON signal for instructing the 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 transmitted to the drive circuit DR in order to control the pressure regulating valve UP. The pressure regulating valve UP is a normally open type linear solenoid valve, and the valve opening amount is in a fully opened state when de-energized. Then, as the energization amount (current value) is increased, the valve opening amount is decreased, the return passage configured including the fluid pump QL is throttled, and the actual hydraulic pressure Pp (resulting braking hydraulic pressure Pw) is obtained. Will be increased. In the pressure regulating valve UP, since the relationship between the supplied energization amount and the adjusted hydraulic pressure Pp is known, the drive signal Up (energized 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 the energization instruction value Up is determined to increase as the target hydraulic pressure Pt increases.

In addition, in the drive signal calculation block DS, the left and right rear wheel duty is adjusted so as to adjust the energization state to the left and right rear wheel inlet valves VIk, VIl based on the elapsed time Tk from the time when the automatic braking control is started. The ratios Duk and Dul (that is, the rear wheel inlet valve drive signals Vik and Vil) are calculated. Specifically, “Duk, Dul=100%” is determined at the beginning of the automatic braking control, and the rear wheel inlet valves VIk, VIl are fully closed. That is, the adjusted hydraulic pressure Pp is supplied to the front wheel cylinders CWi and CWj, but is not supplied to the rear wheel cylinders CWk and CWl. Therefore, the front-rear distribution of the braking force is relatively shifted to the front wheels, and the contribution of the front-wheel braking force is increased and the contribution of the rear-wheel braking force is reduced as compared with the normal distribution. Here, the "normal distribution" is the front-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, a sufficient rear wheel lateral force is generated and a stabilizing moment that reduces vehicle deflection is secured. As a result, the fluctuation of the vehicle at the initial stage of starting the automatic braking control is suppressed, and the directional stability can be secured. Then, when the elapsed time Tk becomes longer, the rear wheel duty ratios Duk and Dul are gradually reduced, 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, CWl, and sufficient vehicle deceleration can be ensured.

Further, in the drive signal calculation block DS, when the braking hydraulic pressure Pw needs to be reduced, the drive signal Vo is output so as to realize the open position of the outlet valve VO (the 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 the switching element (power semiconductor device) based on the drive signals Ml and Up. The drive circuit DR is provided with an electric motor ML and an energization amount sensor (current sensor) that detects an actual energization amount (supply current value) of the pressure regulating valve UP, and the supply current value is supplied to the drive signals Ml and Up. The current feedback control is executed so that they match. Further, in the drive circuit DR, the switching element controls the energization state of the on/off solenoid valves VI and VO by the drive signals Vi and Vo, and as a result, the valve open state (valve closed state) thereof 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. The automatic braking control is performed by the wheel cylinder CW so as to avoid the collision between the vehicle and the obstacle based on the required deceleration Gs corresponding to the relative distance Ob between the object (obstacle) in front of the vehicle and the vehicle. The hydraulic pressure (braking hydraulic pressure) Pw is increased above the hydraulic pressure (master cylinder hydraulic pressure) Pm of the master cylinder CM. Particularly, in the first processing example, rapid braking is performed at a predetermined deceleration or higher only when the probability of collision between the vehicle and the obstacle is high (that is, in an emergency). For example, the operation is performed at a deceleration (0.7 to 0.8 G or more), which is in a region close to the upper limit of the friction coefficient between the wheel and the road surface and is much higher than that in normal braking (during normal braking).

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

In step S130, it is determined whether or not the automatic braking control is necessary. If the automatic braking control is necessary, the target hydraulic pressure Pt is calculated based on the required deceleration Gs. Specifically, the necessity of the automatic braking control is determined based on the comparison between the required deceleration Gs and the actual deceleration Ga. When “Gs≦Ga” and the vehicle is sufficiently decelerated by the driver, the automatic braking control is not necessary, so “Pt=0” is determined and the pressurization by the automatic braking control is executed. Not done. On the other hand, when “Gs>Ga”, automatic braking control is required, and therefore 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 the first and second adjusted hydraulic pressures (actual hydraulic pressures) Pp1 and Pp2 are increased to be the same. Instructions are given.

In step S140, the elapsed time Tk from the calculation cycle when the automatic braking control is started (that is, the control start point) is calculated. In 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 value 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, VIl for the rear wheel cylinders CWk, 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, in the initial stage of the start of the automatic braking control (when the elapsed time Tk is less than the predetermined time tx), the adjusted hydraulic pressure (actual hydraulic pressure) Pp increased from the master cylinder hydraulic pressure Pm by the pressure regulating valve UP is left or right. It is not supplied (introduced) to the rear wheel cylinders CWk and CWl.

In step S170, electric motor ML is driven. For example, the electric motor ML is driven so that the rotation speed thereof rapidly increases at its maximum output. As a result, a recirculation of the brake fluid BF including the pressure regulating valve UP and the fluid pump QL (a flow of the brake fluid BF circulating in “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 adjusted hydraulic pressures Pp1 and Pp2 (actual values or estimated values) are 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 (match) the (target value). Alternatively, in the configuration in which the adjusting hydraulic pressure sensor PP is omitted, the relationship between the differential pressure between the adjusting hydraulic pressure Pp and the master cylinder hydraulic pressure Pm with respect to the energization amount to the pressure adjusting valve UP is known, and thus the first and second The energization amount corresponding to the target hydraulic pressures Pt1 and Pt2 is 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 electricity supplied to the pressure regulating valve UP is controlled.

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

In step S180, the amount of electricity to the rear wheel inlet valves VIk, VIl is gradually reduced based on the elapsed time Tk. That is, when the elapsed time Tk becomes equal to or longer than the predetermined time tx, the rear wheel duty ratios Duk and Dul are gradually reduced from 100%, and the rear wheel inlet valves VIk and VIl are gradually opened. As a result, the adjusted hydraulic pressure Pp is introduced into the rear wheel wheel cylinders CWk, CW1, and the rear wheel braking hydraulic pressures Pwk, Pwl are gradually increased. Then, finally, the rear wheel braking hydraulic pressures Pwk and Pwl match the first and second adjustment hydraulic pressures Pp1 and Pp2.

<Operation of the first processing example of automatic braking control>
The vehicle has first and second braking systems (two braking systems) of a diagonal system. The automatic braking device JS increases the hydraulic pressure Pw of the wheel cylinder CW from the hydraulic pressure Pm of the master cylinder CW based on the required deceleration Gs according to the distance Ob between the object in front of the vehicle and the vehicle. Automatic braking control is achieved. The automatic braking device JS includes a "first pressure regulating valve UP1 for adjusting the first hydraulic pressure Pp1 of the first braking system H1 connected to the right front wheel, the left rear wheel wheel cylinders CWi, CW1", a "left front wheel, a right rear wheel". A second pressure regulating valve UP2 for adjusting the second hydraulic pressure Pp2 of the second braking system H2 connected to the wheel wheel cylinders CWj, CWk, and "a normally open left rear provided for the left rear wheel wheel cylinder CW1". "Wheel inlet valve VIl", "a normally open right rear wheel inlet valve VIk provided for the right rear wheel cylinder CWk", and "first and second pressure regulating valves UP1 based on the required deceleration Gs". A controller ECU that controls the first and second hydraulic pressures Pp1 and Pp2 by controlling the energization to UP2 and also controls the energization to the right rear wheel and the left rear wheel inlet valves VIk and VIl". Composed. Then, the controller ECU energizes the right rear wheel and the left rear wheel inlet valves VIk, VIl, increases the energization of the first and second pressure regulating valves UP1, 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. In the diagram, it is assumed that the driver has not operated the braking operation member BP and the vehicle is automatically and rapidly decelerated by the automatic braking device JS.

Before the time point t0, the automatic braking control is not started and “Gs=0”. Therefore, the target hydraulic pressure Pt (resultingly, 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 valve VIi. VIl is in the non-energized state and is in the fully open position.

At time t0, automatic braking control is started. According to the required deceleration Gs, the rotational drive of the electric motor ML is started and the target hydraulic pressure Pt is increased from “0”. Energization of the pressure regulating valve UP is started, and the regulated hydraulic pressure Pp starts to increase from "0 (non-braking state)". Since the adjusted hydraulic pressure Pp is controlled so as to match the target hydraulic pressure Pt, they overlap in the diagram. 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 “Duk, Dul=100%”, and full energization is performed. 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 completely closed, 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 braking fluid is not supplied. The pressures Pwk and Pwl remain “0”. Further, the time counting of the elapsed time Tk is started from the time point t0 (that is, “Tk=0” at the time point t0).

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

In deceleration of the vehicle, the contribution of the braking force of the front wheels WHi, WHj is significantly higher than the contribution of the braking force of the rear wheels WHk, WHl. This is because the load (vertical force) on the front wheels WHi, WHj increases and the load on the rear wheels WHk, WHl decreases due to the deceleration of the vehicle. Further, when the braking force of the rear wheels WHk, WHl becomes excessive, the directional stability of the vehicle is likely to be impaired. Is set to be 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, the braking fluid BF corresponding to the consumed fluid amount of the wheel cylinder CW is supplied, and then the braking fluid BF is further supplied. As a result, the increase of the braking hydraulic pressure Pw is started. Here, the “consumed liquid amount” is the volume of the braking liquid BF consumed by the rigidity (deformation) of members such as brake calipers, hydraulic pipes (fluid passages), and friction materials arranged around the wheels. Based on the above reason, the liquid consumption amount of the front wheel cylinders CWi, CWj is relatively large with respect to the liquid consumption amount of the rear wheel cylinders CWk, CWl.

In the automatic braking device JS, the first and second adjustment hydraulic pressures Pp1 and Pp2 are not supplied to the rear wheel wheel cylinders CWk and CWl at the initial start of automatic braking control (between time t0 and time t2). The first and second adjustment hydraulic pressures Pp1 and Pp2 are supplied only to the front wheel cylinders CWi and CWj. Therefore, the amount of the brake fluid BF discharged from the first and second fluid pumps QL1 and QL2 is not consumed in the rear wheel cylinders CWk and CWl. That is, the total discharge amount of the fluid pump QL is supplied to the front wheel cylinders CWi, CWj, and the boost responsiveness of the front wheel braking hydraulic pressures Pwi, Pwj is improved, so that vehicle deceleration is efficiently achieved. In addition, since the increase in the rear wheel braking hydraulic pressures Pwk and Pwl is suppressed at the beginning of the control, the lateral force (that is, the stabilizing moment) of the rear wheels WHk and WHl is suppressed even when the vehicle is deflected. ) Is sufficiently secured. As a result, the directional stability of the vehicle is improved, and the driver's discomfort due to vehicle wobbling (deflection) is reduced.

Furthermore, in the automatic braking device JS, the energization amount to the left and right rear wheel inlet valves VIk, VIl is gradually reduced based on the elapsed time Tk from the time when the automatic braking control is started (time t2 to time t3. Until). As a result, the first and second adjustment hydraulic pressures Pp1 and Pp2 are supplied to the rear wheel wheel cylinders CWk and CW1, the rear wheel braking hydraulic pressures Pwk and Pwl are sequentially increased, and finally, the rear wheel braking hydraulic pressures are obtained. 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 device JS, the vehicle deceleration is efficiently achieved in the initial stage of starting the automatic braking control by suppressing the vehicle deflection and making the driver feel uncomfortable. .. A sufficient vehicle deceleration can be ensured as the automatic braking control continues.

<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 that operates only in an emergency in which the vehicle is extremely likely to collide with an obstacle is assumed. The second processing example corresponds to the automatic braking device JS in which the automatic braking control supports not only the automatic braking in an emergency but also the regular braking by the driver (also referred to as “service brake”). Therefore, in the second processing example, the processing of steps S135 and S185 is added to the first processing example. In addition, since the calculation steps having the same symbols as those in the first processing example execute the same processing, they will be briefly described below.

In step S110, various signals (Gs etc.) are read. In 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 itself (that is, when “Gs≦Ga”), the 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 adjusted hydraulic pressures Pp1 and Pp2 (first and second hydraulic pressures), and are calculated as "Pt1=Pt2". To be done. The required deceleration Gs can also be designated in the area of regular braking by the driver. That is, the required deceleration Gs covers (includes) a range from a normal region (for example, low deceleration and gentle braking) to an emergency region (for example, high deceleration and sudden braking).

In step S135, it is determined "whether or not the sudden braking is instructed (that is, whether the emergency braking or the regular braking is performed in executing the automatic braking control)". For example, the determination is made based on "whether or not the deceleration change amount dG is equal to or greater than a predetermined change amount dx and the required deceleration Gs is equal to or greater than 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 change amount dx and the predetermined deceleration gx are threshold values for determination and are preset constants. If “dG≧dx and Gs≧gx” and step S135 is affirmative (during emergency braking), the process proceeds to step S140. If “dG<dx or Gs<gx” and step S135 is negative (during normal braking), the process proceeds to step S185.

In step S140, the elapsed time Tk from the start of the automatic braking control in an emergency is calculated. In 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 set to the fully closed position (blocking state). In step S170, electric motor ML is driven. Then, based on the first and second target hydraulic pressures Pt1 and Pt2, the first and second adjusted hydraulic pressures Pp1 and Pp2 (first and second hydraulic pressures) are set 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 pressure regulating valves UP1 and UP2 adjust the first and second hydraulic pressures (actual hydraulic pressures) Pp1 and Pp2. When the emergency braking is determined in step S135, the electric motor ML is driven so that the maximum output thereof rapidly increases the rotation speed.

When “Tk≧tx” is established in step S180, the amount of electricity to the rear wheel inlet valves VIk, VIl is gradually reduced as the elapsed time Tk elapses. Since the rear wheel inlet valves VIk, VIl are gradually opened, the adjusted hydraulic pressure Pp is introduced to the left and right rear wheel cylinders CWk, CWl, and the rear wheel braking hydraulic pressures Pwk, Pwl are 2 The adjustment hydraulic pressures are gradually increased until they coincide with Pp1 and Pp2.

In step S185, since the automatic braking control is an operation in the normal braking range, the rear wheel inlet valves VIk, VIl are not energized, and the rear wheel inlet valves VIk, VIl are maintained in the fully open position. Since it is not during emergency braking, the adjusted 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 regular braking, during emergency braking (during sudden braking), the rear wheel inlet valves VIk and VIl are fully energized at the start of the emergency braking. The wheel inlet valves VIk and VIl are fully closed to prevent the rear wheel braking hydraulic pressures Pwk and Pwl from increasing. Then, as the elapsed time Tk elapses, the rear wheel inlet valves VIk, VIl are gradually opened from the fully closed state, and the rear wheel braking hydraulic pressures Pwk, Pwl are increased.

<Operation of Second Processing Example of Automatic Braking Control>
The configuration of the automatic braking device JS of the second processing example is similar to that of the first processing example. The difference is that the controller ECU determines "whether or not the braking is sudden" based on the required deceleration Gs. When the sudden braking is not determined, the right rear wheel and the left rear wheel inlet valves VIk and VIl are not energized, and the first and second pressure regulating valves UP1 and UP2 are energized to perform automatic braking. Control is started (service brake operation). On the other hand, when the sudden braking is determined, the right rear wheel and the left rear wheel inlet valves VIk and VIl are energized, and the first and second pressure regulating valves UP1 and UP2 are energized to be automatically switched. Braking control is started (operation 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. Similar to the case of the first processing example, it is assumed that the driver is not operating the braking operation member BP (that is, the case of "Ba=0"). At the time of emergency braking of the automatic braking control, it is represented by the characteristic Cx (shown by a solid line) in each diagram.

Before the time point u0, the automatic braking control is not started and “Gs=0”. Therefore, the target hydraulic pressure Pt (resultingly, the adjusted hydraulic pressure Pp) is "0", and each inlet valve VI is not energized and is in a fully opened state. At time u0, automatic braking control (first, regular braking) is started. According to the required deceleration Gs, the rotational drive of the electric motor ML is started and the target hydraulic pressure Pt is increased from “0”. Energization of the pressure regulating valve UP is started, and the regulated hydraulic pressure Pp starts to increase from "0". In the diagram, the target hydraulic pressure Pt and the adjusted hydraulic pressure Pp overlap. Since the inlet valves VIi to VIj are in the open position, the braking hydraulic pressures Pwi to Pwl are increased from "0".

At time u1, the conditions of "the deceleration change amount dG (differential value of the required deceleration Gs) is equal to or greater than the predetermined variation amount dx" and "the required deceleration Gs is equal to or greater than the predetermined deceleration gx" are satisfied, and the automatic It is determined in the braking control that the braking is emergency braking, and the braking is started. At time u1, the front wheel inlet valves VIi, VIj for the front wheel cylinders CWi, CWj are left in the non-energized state (that is, the open position), and the rear wheel inlet valves VIk, Ck 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, VIl are completely closed, so that the left and right rear wheel cylinders CWk, CWl are no longer supplied with the first and second adjustment hydraulic pressures Pp1, Pp2. The front wheel braking hydraulic pressures Pwi and Pwj are rapidly increased, but the rear wheel braking hydraulic pressures Pwk and Pwl are maintained at the value pb. Then, from the determination point (start point) u1 of the emergency braking, integration of the elapsed time Tk is started.

At time u2, the elapsed time Tk reaches the predetermined time tx. From the time point u2, the rear wheel duty ratios Duk and Dul are gradually reduced with the gradient Kg, and the rear wheel inlet valves VIk and VIl are gradually opened. Then, since the first and second adjusting hydraulic pressures Pp1 and Pp2 start to be introduced into the rear wheel wheel cylinders CWk and CW1, the rear wheel braking hydraulic pressures Pwk and Pwl are gradually increased from the value pb. At time u3, “Duk, Dul=0% (corresponding to the fully open position of the rear wheel inlet valves VIk, VIl)”, and the rear wheel braking fluid pressures Pwk, Pwl are the front wheel braking fluid pressures Pwi, Pwj (=pa). (That is, the regular allocation).

The second processing example also has the same effect as the first processing example. At the beginning of the start of the emergency braking (rapid braking) of the automatic braking control (between time point u1 and time point t2), the first and second adjustment hydraulic pressures Pp1 and Pp2 are supplied to the rear wheel cylinders CWk and CWl. Instead, since the adjusted hydraulic pressure Pp is supplied only to the front wheel cylinders CWi, CWj, the entire amount of the brake fluid BF discharged by the fluid pump QL is supplied to the front wheel cylinders CWi, CWj. As a result, the boosting response of the front wheel braking hydraulic pressures Pwi and Pwj is improved, and vehicle deceleration is efficiently achieved. In addition, since the increase in the rear wheel braking fluid pressures Pwk and Pwl is suppressed at the beginning of the emergency control, the lateral force of the rear wheels WHk and WHl is sufficiently obtained even when the vehicle is deflected. Therefore, the stabilizing moment that suppresses the fluctuation of the vehicle is secured, and the directional stability of the vehicle is improved. This suppresses the driver from feeling uncomfortable due to vehicle deflection.

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

Note that during normal braking of automatic braking control (when the processing of step S135 is negative), it is represented by the characteristic Cy (shown by a chain line) in each diagram. In this regular braking, the rear wheel inlet valves VIk and VIl are not energized (see the processing of step S185). Therefore, when the driver's braking operation is not performed, 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 adjusted by the pressure adjusting valve UP. Controlled by Pp.

JS... Automatic braking device, BP... Braking 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 adjusted hydraulic pressures (first and second hydraulic pressures), Pm1, Pm2 (= Pm)... 1st, 2nd master cylinder hydraulic pressure, Tk... elapsed time.

Claims (2)

It is equipped in a vehicle that adopts a diagonal system as two braking systems,
An automatic braking device for a vehicle, which executes automatic braking control for increasing a hydraulic pressure of a wheel cylinder from a hydraulic pressure of a master cylinder based on a required deceleration corresponding to a distance between an object in front of the vehicle and the vehicle. ,
A first pressure regulating valve for adjusting a first hydraulic pressure of a first braking system connected to the right front wheel and the left rear wheel wheel cylinder of the two braking systems;
A second pressure regulating valve for adjusting a second hydraulic pressure of a second braking system connected to the left front wheel and the right rear wheel 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 wheel cylinder,
The first and second hydraulic pressures are adjusted by controlling the energization of the first and second pressure regulating valves based on the required deceleration, and the energization of the right rear wheel and left rear wheel inlet valves is performed. A controller for controlling
Equipped with
The controller is
An automatic braking device for a vehicle, which energizes the right rear wheel and the left rear wheel inlet valve, increases energization to the first and second pressure regulating valves, and starts the automatic braking control. It is equipped in a vehicle that adopts a diagonal system as two braking systems,
An automatic braking device for a vehicle, which executes automatic braking control for increasing a hydraulic pressure of a wheel cylinder from a hydraulic pressure of a master cylinder based on a required deceleration corresponding to a distance between an object in front of the vehicle and the vehicle. ,
A first pressure regulating valve for adjusting a first hydraulic pressure of a first braking system connected to the right front wheel and the left rear wheel wheel cylinder of the two braking systems;
A second pressure regulating valve for adjusting a second hydraulic pressure of a second braking system connected to the left front wheel and the right rear wheel 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 wheel cylinder,
The first and second hydraulic pressures are adjusted by controlling the energization of the first and second pressure regulating valves based on the required deceleration, and the energization of the right rear wheel and left rear wheel inlet valves is performed. A controller for controlling
Equipped with
The controller is
Based on the required deceleration, determine whether or not sudden braking,
If the sudden braking is not determined,
Without energizing the right rear wheel and the left rear wheel inlet valve, increasing the energization to the first and second pressure regulating valves to start the automatic braking control,
If the sudden braking is determined,
An automatic braking device for a vehicle, which energizes the right rear wheel and the left rear wheel inlet valve, increases energization to the first and second pressure regulating valves, and starts the automatic braking control.