JPH10244917A - Braking force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly raise a wheel cylinder pressure, in a braking force control device by which when an emergency brake operation is detected, brake-assist control for producing a larger braking force than that at the ordinary time is executed, by starting the brake-assist control in accordance with the various circumferences and at a proper timing. SOLUTION: At the time t1 when the emergency brake operation is detected, a pressure difference Pdiff is produced between the master cylinder pressure PM/ C and the wheel cylinder pressure PW/ C. In such a condition, since the PW/ C can be quickly raised making a liquid pressure source of a hydrobooster 36 (not shown), the normal braking condition can be maintained. Then, at the time t2 when the differential pressure Pdiff is below a prescribed value L, brake- assist control is started. This prescribed value L is set by considering the pressure-raising velocity of the wheel cylinder pressure PW/ C which is realized both in the ordinary brake control and in the brake-assist control respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking force control device, and more particularly to a braking force control device that generates a larger braking force than usual when an emergency braking operation is performed on a vehicle.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No.
As disclosed in No. 0, there is known a braking force control device that generates a larger braking force than usual when an emergency braking operation is requested. The conventional braking force control device includes a hydraulic pressure generating mechanism that generates a high assist hydraulic pressure using a pump as a hydraulic pressure source.

In the above-mentioned conventional apparatus, when the brake pedal is operated at a speed lower than a predetermined operation speed,
The master cylinder pressure adjusted to the hydraulic pressure according to the brake depression force is supplied to the wheel cylinder. Hereinafter, control for realizing such a state is referred to as normal brake control. When the brake pedal is operated at a speed exceeding a predetermined operation speed, it is determined that an emergency brake operation has been performed. In this case, by switching the hydraulic pressure source that applies hydraulic pressure to the wheel cylinder from the master cylinder to the hydraulic pressure generating mechanism, the high assist hydraulic pressure of the hydraulic pressure generating mechanism is supplied to the wheel cylinder. Hereinafter, control for achieving such a state is referred to as brake assist control. Therefore, according to the above-described conventional device, the braking force can be controlled to a magnitude corresponding to the brake depression force in the normal state, and the braking force can be quickly increased after the emergency braking operation is detected.

[0004]

By the way, in the above-mentioned conventional apparatus, the brake assist control is started by switching the hydraulic pressure source to the hydraulic pressure generating mechanism immediately after the emergency braking operation is detected. However, when the emergency brake operation is detected, the master cylinder pressure is rapidly increased due to the high-speed operation of the brake pedal. On the other hand, the speed at which the wheel cylinder pressure is increased by switching the hydraulic pressure source to the hydraulic pressure generating mechanism is limited by a delay in transmission of the hydraulic pressure from the hydraulic pressure generating mechanism to the wheel cylinder, a limit of the pump capacity, and the like. Therefore, if the brake assist control is started immediately after the emergency brake operation is detected, a situation in which the speed at which the wheel cylinder pressure is increased may occur rather than when the normal brake control is maintained. is there.

In order to prevent such a situation, it is conceivable to provide an appropriate delay time from when the emergency brake operation is detected to when the brake assist control is started. However, the emergency brake operation may be performed when the brake pedal is stepped on at a high speed from a state where the normal brake operation is being performed (hereinafter, such an emergency brake operation is referred to as an additional stepped emergency brake operation). . The pressure difference between the master cylinder and the wheel cylinder becomes smaller when the emergency brake operation is performed by further pressing, as compared to when the emergency brake operation is performed from the state where the brake pedal is not operated. I have. The boosting speed of the wheel cylinder, which can be realized by using the master cylinder as the hydraulic pressure source, decreases as the differential pressure between the master cylinder and the wheel cylinder decreases. Therefore, even if an emergency braking operation is performed by increasing the number of steps, it is not necessary to provide a constant delay time from the detection of the emergency braking operation to the start of the brake assist control. Is delayed, and a rapid increase in the wheel cylinder pressure cannot be realized.

The present invention has been made in view of the above points, and when an emergency brake operation is performed, the wheel cylinder pressure is always rapidly increased regardless of whether the emergency brake operation is performed by further pressing. It is an object to provide a braking force control device capable of increasing the pressure.

[0007]

The above object is achieved by the present invention.
As described in the above, the emergency braking operation is executed by the braking force control device that executes the normal braking control that generates the braking force according to the brake pedaling force and the brake assist control that generates the large braking force compared with the normal control. Emergency brake operation detecting means for detecting that the brake assist has been performed, and when the differential pressure between the master cylinder pressure and the wheel cylinder pressure becomes equal to or less than a predetermined value after detecting that the emergency brake operation has been performed, This is achieved by a braking force control device including: a brake assist control start unit that starts control.

In the present invention, during normal brake control, a hydraulic pressure corresponding to the brake depression force is supplied to the wheel cylinder. When the emergency brake operation is performed, the brake pedal force rises sharply. Therefore, when the emergency brake operation is detected, a large differential pressure is generated between the master cylinder pressure and the wheel cylinder pressure. In such a case, executing the normal brake control can increase the wheel cylinder pressure more quickly than executing the brake assist control. The brake assist control start means starts the brake assist control when the pressure difference between the master cylinder pressure and the wheel cylinder pressure becomes equal to or less than a predetermined value after detecting that the emergency braking operation has been performed. Therefore, according to the present invention, the brake assist control is started when it is more advantageous to execute the brake assist control than to execute the normal brake control.

According to a second aspect of the present invention, there is provided a braking force control apparatus according to the first aspect, further comprising control start differential pressure determining means for determining the predetermined value based on a master cylinder pressure. This is also achieved by a braking force control device. In the present invention, in a state where a constant differential pressure is generated between the master cylinder pressure and the wheel cylinder pressure, the speed at which the wheel cylinder pressure is increased during the normal brake control changes according to the master cylinder pressure. . Therefore, the differential pressure at which executing the brake assist control is more advantageous than executing the normal brake control changes according to the master cylinder pressure. The control start differential pressure determining means determines the predetermined value based on the master cylinder pressure. Therefore, according to the present invention, the brake assist control is started at a more appropriate timing for rapidly increasing the wheel cylinder pressure.

[0010]

FIG. 1 shows a system configuration diagram of a hydro-booster type braking force control device (hereinafter simply referred to as a braking force control device) according to an embodiment of the present invention. The braking force control device according to the present embodiment includes an electronic control unit 10 (hereinafter, referred to as an electronic control unit 10).
ECU 10).

The braking force control device has a brake pedal 12. A brake switch 14 is provided near the brake pedal 12. Brake switch 14
Outputs an ON signal when the brake pedal 12 is depressed. The output signal of the brake switch 14 is E
It is supplied to CU10. The ECU 10 determines whether or not the brake pedal 12 is depressed based on the output signal of the brake switch 14.

The brake pedal 12 is connected to the master cylinder 1
6. A reservoir tank 18 is disposed above the master cylinder 16. Reservoir tank 1
8, a return passage 20 for returning the brake fluid to the reservoir tank 18 is connected to the return passage. The supply passage 22 communicates with the reservoir tank 18. The supply passage 22 communicates with the suction side of the pump 24. The discharge side of the pump 24 has an accumulator passage 26
Are in communication. Accumulator passage 26 and supply passage 22
A constant pressure release valve 27 that opens when an excessive pressure is generated in the accumulator passage 26 is disposed between the accumulator passage 26 and the accumulator passage 26.

The accumulator passage 26 has a pump 24
Accumulator 28 for storing hydraulic pressure discharged from
Are in communication. In the accumulator passage 26,
Upper limit pressure switch 30 and lower limit pressure switch 32
Is connected. The upper limit pressure switch 30 is
The pressure in the accumulator passage 26 (hereinafter, accumulator pressure P
_ACCON) when the output exceeds the specified upper limit.
Occur. On the other hand, the lower limit pressure switch 32
Rator pressure P_ACCON output when exceeds the specified lower limit
Occurs.

[0014] The pump 24 is turned on from the lower pressure switch 32 until an on output is generated by the upper pressure switch 30, that is, after the accumulator pressure P _ACC falls below the lower limit, the upper limit value. Until it reaches. Therefore, the accumulator pressure P _ACC is always maintained between the upper limit and the lower limit. A regulator 34 is integrated into the master cylinder 16. The accumulator passage 26 communicates with the regulator 34. Hereinafter, the master cylinder 16 and the regulator 34 are collectively referred to as a hide booster 36.

FIG. 2 is a sectional view of the hydro booster 36. The hydro booster 36 has a housing 38. A first piston 40 is provided inside the housing 38. The first piston 40 has a large-diameter portion 42 and a small-diameter portion 44. Inside the housing 38, an assist hydraulic chamber 46 is formed on the first piston 40 on the brake pedal 12 side, and an atmospheric pressure chamber 48 is formed around the small diameter portion 44. The atmospheric pressure chamber 48
It is always in communication with the reservoir tank 18.

A second piston 50 is provided inside the housing 38. The second piston 50 has a large diameter portion 5.
2 and a spool portion 54. Inside the housing 38, a first hydraulic chamber 56 is formed between the first piston 40 and the second piston 50, and a second hydraulic chamber 58 is formed so as to surround the spool 54. In the first hydraulic chamber 56, the first piston 40 and the second
A spring 60 for urging the piston 50 in the separating direction is provided. The second hydraulic chamber 58 communicates with the assist hydraulic chamber 46 via a hydraulic passage 62.

Inside the housing 38, a high-pressure passage 64 is formed, one end of which communicates with the accumulator passage 26 and the other end of which opens to the outer peripheral surface of the spool portion 54. The spool 54 is displaced leftward in FIG. 1 to make the high pressure passage 64 and the second hydraulic chamber 58 conductive, and is displaced rightward in FIG. The hydraulic chamber 58 is cut off.

A valve mechanism 66 is provided inside the housing 38. The valve mechanism 66 includes a valve seat 68, a valve body 70,
And a spring 72. An atmospheric pressure chamber 74 communicating with the reservoir tank 18 is formed around the valve seat 68. Further, a pressure regulating passage 76 communicating with the second hydraulic chamber 58 is opened at an end face of the valve seat 68. Valve seat 68
Is formed with an oil passage communicating the atmospheric pressure chamber 74 and the pressure regulating passage 76. The valve body 70 includes the second piston 50
Is the right displacement end in FIG. 1, that is, when the oil passage is in the conducting state when located at the original position, and the second piston 50 is displaced leftward from the original position in FIG. Then, the oil passage is closed.

Inside the housing 38, the reaction disk 7 is located at a position slightly separated from the end face of the valve mechanism 66.
8 are provided. The reaction disk 78 defines a reaction force chamber 80 communicating with the pressure adjustment passage 76 inside the housing 38. The reaction disk 78 is formed of a member having elasticity. When a high-pressure oil pressure is guided to the reaction force chamber 80, the reaction disk 78 is elastically deformed and comes into contact with the valve mechanism 66.

When the brake pedal force F is not applied to the brake pedal 12, the first piston 40 and the second piston 50 are both held at their original positions, that is, at the right displacement ends in FIG. In this case, since the pressure regulating passage 76 and the reservoir tank 18 are electrically connected via the valve mechanism 66, the second hydraulic chamber 58 is regulated to the atmospheric pressure. When the second hydraulic chamber 58 is adjusted to the atmospheric pressure, the assist hydraulic chamber 46 communicates with the second hydraulic chamber via the hydraulic passage 62, and is formed between the first piston 40 and the second piston 50. The first hydraulic chamber 56 is similarly adjusted to the atmospheric pressure.

When the brake pedal force F is applied to the brake pedal 12, the first piston 40 and the second piston 50
Are displaced from their original positions to the left in FIG. When a leftward displacement occurs in the second piston 50, the valve mechanism 66 is first closed, and the pressure regulating passage 76 and the reservoir tank 18 are shut off. When the second piston 50 is further displaced leftward, the high-pressure passage 64 and the second hydraulic chamber 58 are brought into conduction through the spool portion 54.

[0022] high-pressure passage 64 and the second hydraulic chamber 58 becomes conductive, the accumulator pressure P _{AC C} is the second hydraulic chamber 58
Guided by the inner pressure of the second hydraulic chamber 58 (hereinafter, this pressure is referred to as a regulator pressure P _RE) by the boosts. The regulator pressure _PRE is guided to the assist hydraulic chamber 46. Therefore, when the regulator pressure P _RE is boosted, the first piston 40, the assist force Fa corresponding to the regulator pressure P _RE in addition to the brake pressing force F is applied.

[0023] regulator pressure P _RE guided to assist hydraulic chamber 46 is an area that acts on the first piston 40 and S _1, the assist force Fa can be expressed as the following equation. _{Fa = S 1 × P RE ···} (1) In this case, the first hydraulic chamber 56, hydraulic pressure corresponding to the brake pressing force F and the regulator pressure P _RE (hereinafter, this pressure master cylinder pressure P _{M / C} ) Occur. _Assuming that the cross-sectional area of the small diameter portion 44 of the first piston 40 is S ₂ , the master cylinder pressure P _{M / C} can be expressed by the following equation using the brake pedal force F and the regulator pressure _PRE .

P _{M / C} = (F + S ₁ × P _RE ) / S ₂ (2) At this time, the force F _{M / C at} which the brake fluid in the first hydraulic chamber 56 presses the second piston 58 is , the area of the large diameter portion 52 of the second piston 50 when the S _2, can be expressed as the following equation. F _{M / C} = P _{M / C} × S ₂ = F + S ₁ × P _PRE (3) Also, when the regulator pressure _PRE is generated in the second hydraulic chamber 58, the brake in the second hydraulic chamber 58 The force F _RE by which the fluid presses the second piston 58 can be expressed by the following equation, assuming that the area where the regulator pressure _PRE in the second hydraulic chamber 58 acts on the second piston 58 is S ₃ .

[0025] _{F RE = P RE × S 3} ··· (4) regulator pressure P _RE generated in the second hydraulic chamber 58 is also directed to the reaction chamber 80. The second piston 50 has a valve mechanism 66
And when the reaction disc 78 is displaced in the right in FIG. 2 until abutment, the second piston 50, the reaction force Fr in accordance with the regulator pressure P _RE through the reaction disc 78 is transmitted. The reaction force Fr can be expressed by the following equation using a predetermined value K.

Fr = K × P _RE (5) After the brake pedal force F is applied to the brake pedal 12,
F _{M / C} , F _RE , and F shown in the above equations (3) to (5)
The second piston 50 is displaced from the original position to the left in FIG. 2 while the following relationship is established for r. F _{M / C} > F _RE + Fr (6) In this case, since the second hydraulic chamber 58 is kept in conduction with the high-pressure passage 64, the regulator pressure _PRE gradually increases.

After the brake pedal force F is applied to the brake pedal 12, F _{M / C} shown in the above equations (3) to (5),
When a state is established in which the following relationship is established between F _RE and Fr, the second piston 50 is pushed back toward the original position. F _{M / C} <F _RE + Fr (7) When the second piston 50 is pushed back toward the original position, the second hydraulic chamber 58 is shut off from the high-pressure passage 64, so that the regulator pressure _PRE increases. Stopped. Thus, according to the hydro booster 36, after the brake pedal force is applied to the brake pedal 12, the regulator pressure _PRE is adjusted so that the following relationship is satisfied.

F _{M / C} = F _RE + Fr (8) The relation of the above equation (8) can be rewritten as the following equation using the relation of the above equations (3) to (5). P _RE = F / (S ₃ + K−S ₁ ) (9) In the present embodiment, the hydro booster 36 is determined such that “1 / (S ₃ + K−S ₁ )” in the above equation (9) is a predetermined value. The booster ratio is designed so that the regulator pressure _PRE and the master cylinder pressure PM _{/ C} are substantially equal. Therefore, according to the hydro booster 36, when the brake pedal force F is applied to the brake pedal 12, the brake pedal force F is applied to the first hydraulic chamber 56 and the second hydraulic chamber 58.
, A hydraulic pressure (master cylinder pressure PM _{/ C} and regulator pressure _PRE ) having a predetermined boosting ratio can be generated.

In the following description, the hydraulic pressure generated by the hydro booster 36, that is, the master cylinder pressure P _{M / C} generated in the first hydraulic chamber 56, and
Are collectively regulator pressure P _RE generated in the second hydraulic chamber 58, referred to as a master cylinder pressure P _{M / C.} As shown in FIG. 1, a first hydraulic chamber 56 of the hydro booster 36, and
A first hydraulic passage 82 and a second hydraulic passage 84 communicate with the second hydraulic chamber 58, respectively. First hydraulic passage 8
2 includes a first assist solenoid 86 (hereinafter referred to as SA _- 18).
6) and a second assist solenoid 88 (hereinafter, referred to as a second assist solenoid 88).
SA _- 288). On the other hand, the second hydraulic passage 84 has a third assist solenoid 90 (hereinafter referred to as SA).
_-3 90).

SA- ₁ 86 and SA- ₂₈₈ also include:
The control pressure passage 92 is in communication. The control pressure passage 92 is provided with a regulator switching solenoid 94 (hereinafter, STR94).
) To the accumulator passage 26. The STR 94 is a two-position solenoid valve that shuts off the accumulator passage 26 and the control pressure passage 92 when turned off, and connects the accumulator passage 26 and the control pressure passage 92 when turned on. is there.

The hydraulic pressure passage 96 provided corresponding to the right front wheel FR communicates with the SA _- 186. Similarly, SA- ₂
Reference numeral 88 denotes a hydraulic passage 9 provided corresponding to the left front wheel FL.
8 are in communication. The SA- ₁ 86 causes the first hydraulic passage 82 to be electrically connected to the first hydraulic passage 82 by being turned off.
And a two-position solenoid valve that realizes a second state in which the hydraulic pressure passage 96 is connected to the control pressure passage 92 by being turned on. Further, the SA- ₂ 88 realizes a first state in which the hydraulic pressure path 98 is connected to the first hydraulic pressure path 82 when turned off, and realizes a hydraulic pressure path 98 when turned on. Is a two-position solenoid valve that realizes a second state in which the valve is connected to the control pressure passage 92.

The hydraulic pressure passages 100 provided corresponding to the left and right rear wheels RL, RR communicate with the SA _- 390. SA
_-390 , when turned off, makes the second hydraulic passage 84 and the hydraulic passage 100 conductive, and when turned on, the second hydraulic passage 84 and the hydraulic passage 100 Is a two-position solenoid valve that shuts off the valve. A check valve 102 is provided between the second hydraulic passage 84 and the hydraulic passage 100 to allow only the flow of fluid from the second hydraulic passage 84 toward the hydraulic passage 100.

In the hydraulic passage 96 corresponding to the right front wheel FR,
A right front wheel holding solenoid 104 (hereinafter, referred to as SFRH 104) communicates therewith. Similarly, a left front wheel holding solenoid 106 (hereinafter, referred to as a hydraulic passage 96) corresponding to the left front wheel FL
SFLH 106) is provided in the hydraulic passage 100 corresponding to the left and right rear wheels RL, RR.
(Hereinafter, referred to as SRRH 108) and a left rear wheel holding solenoid 110 (hereinafter, referred to as SRLH 110) communicate with each other. Hereinafter, when these solenoids are collectively referred to, they are referred to as “holding solenoid S ** H”.

The front right wheel pressure reducing solenoid 112 (hereinafter, referred to as SFRR 112) communicates with the SFRH 104. Similarly, SFLH 106, SRRH 108 and S
The RLH 110 includes a left front wheel decompression solenoid 11
4 (hereinafter, referred to as SFLR 114), a right rear wheel pressure reducing solenoid 116 (hereinafter, referred to as SRRR 116), and a left rear wheel pressure reducing solenoid 118 (hereinafter, referred to as SRLR 118) communicate with each other. Hereinafter, these solenoids are collectively referred to as “pressure reducing solenoid S ** R”.

A wheel cylinder 120 of the right front wheel FR communicates with the SFRH 104. Similarly, SFL
The wheel cylinder 122 of the left front wheel FL is attached to H106.
RRH 108 includes a wheel cylinder 124 of the right rear wheel RR.
However, the wheel cylinders 126 of the left rear wheel RL communicate with the SRLH 110, respectively. Further, the hydraulic passage 9
6 between the wheel cylinder 120 and the SFRH 104
From the wheel cylinder 120 side to the hydraulic passage 9
A check valve 128 is provided to allow fluid flow to 6. Similarly, between the hydraulic passage 98 and the wheel cylinder 122, between the hydraulic passage 100 and the wheel cylinder 124
And the hydraulic passage 100 and the wheel cylinder 12
6, between SFLH106 and SRRH10
Non-return valves 130, 132, 134 are provided to allow fluid flow to bypass SRLH 110 and SRLH 110.

The SFRH 104 brings the hydraulic passage 96 into conduction with the wheel cylinder 120 when turned off, and the hydraulic passage 9 when turned on.
6 is a two-position solenoid valve that shuts off the wheel cylinder 120 and the wheel cylinder 120. Similarly, SFLH106, SRRH10
8 and the SRLH 110 are turned on, respectively, a path connecting the hydraulic path 98 and the wheel sinder 122, a path connecting the hydraulic path 100 and the wheel sinder 124, and a path connecting the hydraulic path 100 and the wheel sinder 126. It is a two-position solenoid valve that shuts off.

SFRR112, SFLR114, SRR
A return passage 20 communicates with R116 and SRLR118. The SFRR 112 is a two-position solenoid valve that turns off the wheel cylinder 120 and the return passage 20 when turned off, and turns on the wheel cylinder 120 and the return passage 20 when turned on. It is. Similarly, SFLR114, S
RRR 116 and SRLR 118 are turned on, respectively, to connect wheel cylinder 122 to return passage 20, to connect wheel cylinder 124 to return passage 20, and to connect wheel cylinder 12 to return passage 20.
6 is a two-position solenoid valve for conducting a path connecting the return passage 6 and the return passage 20.

Near the right front wheel FR, a wheel speed sensor 13 is provided.
6 are provided. The wheel speed sensor 136 detects the right front wheel F
A pulse signal is output at a cycle corresponding to the rotation speed of R. Similarly, near the left front wheel FL, near the right rear wheel RR, and
Near the left rear wheel RL, a wheel speed sensor 1 that outputs a pulse signal at a cycle corresponding to the rotation speed of the corresponding wheel.
38, 140 and 142 are provided. Output signals of the wheel speed sensors 136 to 142 are supplied to the ECU 10. ECU10 detects the rotational speed V _W of each wheel based on the output signal of the wheel speed sensors 136-142.

A hydraulic sensor 144 is provided in the second hydraulic passage 84 communicating with the second hydraulic chamber 58 of the hydro booster 36. The hydraulic pressure sensor 144 detects the hydraulic pressure generated inside the second hydraulic chamber 58, that is, the hydraulic booster 36.
And outputs an electric signal corresponding to the master cylinder pressure P _{M / C} generated. The output signal of the fluid pressure sensor 144 is EC
It is supplied to U10. The ECU 10 is a hydraulic pressure sensor 1
The master cylinder pressure P _{M / C} is detected based on the output signal of 44.

Next, the operation of the braking force control device of this embodiment will be described. The braking force control device according to the present embodiment switches the state of various solenoid valves disposed in the hydraulic circuit, thereby functioning as a normal brake device, functioning as an anti-lock brake system, and controlling braking force. When a quick rise is required, a function (brake assist function) of generating a larger braking force than in normal times is realized.

FIG. 1 shows a state of a braking force control device for realizing a function as a normal brake device (hereinafter, referred to as a normal brake function). That is, the normal braking function is realized by turning off all the solenoid valves included in the braking force control device as shown in FIG. Hereinafter, the state shown in FIG. 1 is referred to as a normal brake state. Also,
Control for realizing the normal brake function in the braking force control device is referred to as normal brake control.

In FIG. 1, the wheel cylinders 120 and 122 of the left and right front wheels FL and FR communicate with the first hydraulic chamber 56 of the hydro booster 34 via the first hydraulic pressure passage 82. Further, the wheel cylinders 12 of the left and right rear wheels RL and RR are provided.
4 and 126 communicate with the second hydraulic chamber 58 of the hydro booster 36 via the second hydraulic passage 84. in this case,
Wheel cylinder pressure P of wheel cylinders 120 to 126
_{W / C} is always controlled to be equal to the master cylinder pressure PM _{/ C.} Therefore, according to the state shown in FIG. 1, the normal braking function is realized.

FIG. 3 shows a state of a braking force control device for realizing a function as an antilock brake system (hereinafter referred to as an ABS function). That is, ABS
The function is, as shown in FIG. 3, SA _- 186 and SA _- 288.
Is turned on, and the holding solenoid S ** H and the pressure reducing solenoid S ** R are appropriately driven in accordance with the request of the ABS. Hereinafter, the state shown in FIG. 3 is referred to as an ABS operation state. Further, control for realizing the ABS function in the braking force control device is referred to as ABS control.

The ECU 10 starts the ABS control when the vehicle is in a braking state and an excessive slip ratio is detected for any of the wheels. During the ABS control, the hydraulic passages 96 and 98 provided corresponding to the front wheels communicate with the second hydraulic chamber 58 of the hydro booster 36 similarly to the hydraulic passage 100 provided corresponding to the rear wheels. Therefore, ABS
During control, the wheel cylinder pressures P _{W / C of} all wheels are
The pressure is increased using the hydraulic chamber 58 as a hydraulic pressure source.

During the execution of the ABS control, the holding solenoid S
** H is opened and pressure reducing solenoid S ** R
Is closed, the wheel cylinder pressure P _{W / C of} each wheel
Can be increased. Hereinafter, this state is referred to as (i) pressure increase mode. Also, during the ABS control, the holding solenoid S *
When both * H and the pressure reducing solenoid S ** R are closed, the wheel cylinder pressure P _{W / C} of each wheel can be maintained. Hereinafter, this state is referred to as (ii) holding mode.
Furthermore, when the holding solenoid S ** H is closed and the pressure reducing solenoid S ** R is opened during the ABS control, the wheel cylinder pressure P _{W / C} of each wheel can be reduced. Hereinafter, this state is referred to as (iii) decompression mode.

During the ABS control, the ECU 10 appropriately realizes (i) the pressure increasing mode, (ii) the holding mode, and (iii) the pressure reducing mode for each wheel according to the slip state of each wheel. Thus, the holding solenoid S ** H and the pressure reducing solenoid S ** R are controlled. Holding solenoid S **
When H and the pressure reducing solenoid S ** R are controlled as described above, the wheel cylinder pressures P _{W / C} of all the wheels are controlled to pressures that do not cause an excessive slip ratio on the corresponding wheels. Therefore, according to the above control, the ABS function can be realized in the braking force control device.

During the ABS control, the brake fluid in the wheel cylinders 120 to 126 is discharged to the return passage 20 every time the decompression mode is performed on each wheel. Each time the pressure increase mode is performed on each wheel, the hydro booster 36
The brake fluid is supplied to the wheel cylinders 120 to 126 from. Therefore, during the ABS control, a larger amount of brake fluid flows out of the hydro booster 36 than during normal braking.

The hydraulic pressure source such as the accumulator 28 does not communicate with the first hydraulic chamber 56 of the Hyrod booster 36. Therefore, if the first hydraulic chamber 56 is used as a hydraulic pressure source during execution of the ABS control, a large amount of brake fluid flows out of the first hydraulic chamber 56, and as a result, an excessive stroke of the brake pedal 12 A situation arises. On the other hand, in the system according to the present embodiment, the second hydraulic chamber 58 that communicates with the accumulator 28 via the spool 54 during the ABS control is used as a hydraulic pressure source. Therefore, according to the system of the present embodiment, an excessive stroke does not occur on the brake pedal 12 during execution of the ABS control.

FIG. 4 shows a brake assist function (hereinafter, referred to as a brake assist function).
The state of the braking force control device for realizing the BA function)
State. That is, the BA function is, as shown in FIG.
SA _-186 and SA_-288 is turned on, and S
A_-3Implemented by turning on 90 and STR94
Is done. Hereinafter, the state shown in FIG. 4 is referred to as a BA operation state.
Also, to realize the BA function in the braking force control device
Is referred to as BA control.

The ECU 10 realizes the BA operation state shown in FIG. 4 when the driver performs a brake operation requesting a quick rise of the braking force (hereinafter, this brake operation is referred to as an emergency brake operation). . In the BA operating state, hydraulic passages 96, 9 provided corresponding to the front wheels are provided.
8, and a hydraulic passage 100 provided corresponding to the rear wheel
Communicates with the accumulator passage 26 via the STR 94. Therefore, when the BA operation state is realized,
The wheel cylinder pressures P _{W / C} of all wheels are increased by using the accumulator 28 as a hydraulic pressure source.

The accumulator 28 stores a high accumulator pressure P _ACC . Therefore, when the wheel cylinder pressure P _{W / C} is boosted by using the accumulator 28 as a hydraulic pressure source, the wheel cylinder pressure P _{W / C} can be quickly increased. As described above, according to the state shown in FIG. 4, the function of quickly increasing the braking force, that is, B
Function A can be realized.

In the BA operating state shown in FIG. 4, the hydraulic passages 96, 98, 100 communicate with the accumulator passage 26 as described above, and the check valve 102
Through the second hydraulic passage 84. For this reason,
When the master cylinder pressure P _{M / C} guided to the second hydraulic passage 84 is higher than the wheel cylinder pressure P _{W / C} of each wheel, even in the BA operating state, the hydraulic cylinder 36 is used as a hydraulic pressure source by using the hydro booster 36 as a hydraulic pressure source. The pressure P _{W / C} can be increased.

When the BA control is started in the braking force control device, thereafter, the wheel cylinder pressure P _{W / C of} each wheel is rapidly increased, so that an excessive slip ratio may occur in any one of the wheels. is there. In such a case, the ECU 10 executes the ABS control in addition to the BA control. Hereinafter, this control is referred to as BA + ABS control. BA
+ ABS control, as shown in FIG. 4, SA _-1 86, SA _-2
88, the SA- ₃ 90 and the STR 94 are turned on, and the above-mentioned (i) pressure-increasing mode, (ii) holding mode, and (iii) pressure-reducing mode are appropriately realized for each wheel. Holding solenoid S * according to wheel slip condition
This is realized by controlling * H and the pressure reducing solenoid S ** R. According to the above-described BA + ABS control, the wheel cylinder pressures P _{W / C} of all the wheels are reduced by the accumulator 28.
Can be controlled to an appropriate pressure without causing an excessive slip ratio on the corresponding wheel.

Next, referring to FIG. 5 and FIG.
A description will be given of a method by which the emergency brake operation is detected, and a method by which the BA control is started when the emergency brake operation is detected. FIG. 5 shows an example of a time chart realized when the driver performs an emergency braking operation in the braking force control device of the present embodiment. The curve shown in FIG. 5A indicates a change amount ΔP _{M / C} of master cylinder pressure P _{M / C} per unit time (hereinafter, change speed ΔP _{M / C} ) when an emergency brake operation is performed by the driver.
The following shows an example of the change that occurs. FIG. 5 (B)
The curve shown by and the curve shown by under similar circumstances,
Examples of changes occurring in the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C} are shown below.

As shown by the curve in FIG. 5B, when an emergency braking operation is performed by the driver, the master cylinder pressure PM _{/ C} is immediately increased to an appropriate pressure after the braking operation is started. You. At this time, the change speed ΔP
_As shown in FIG. 5A, the _{M / C} increases toward the maximum value ΔP _MAX in synchronization with the time when the master cylinder pressure P _{M / C} sharply increases after the brake operation is started. In synchronization with the time when the pressure PM _{/ C} converges to an appropriate pressure, the pressure PM _{/ C} decreases to a value near "0".

The brake fluid flowing out of the hydro booster 36 flows into the wheel cylinders 120 to 126 via a brake hose or the like. Wheel cylinder pressure P
_{The W / C} starts boosting after a certain amount of brake fluid flows into the _{W / C.} Therefore, as shown by the curve in FIG. 5B, the wheel cylinder pressure P _{W / C} increases with a delay with respect to the master cylinder pressure P _{M / C.}

As described above, the ECU 10 executes the BA control when the emergency braking operation by the driver is detected. In determining whether or not the driver has performed an emergency braking operation, the ECU 10 firstly operates the brake pedal 12 exceeding a predetermined speed, specifically, a change speed ΔP _M exceeding a first predetermined speed THΔP1. Detect _{/ C.} When detecting a change speed ΔP _{M / C} that satisfies ΔP _{M / C} > THΔP1, the ECU 10 determines that the emergency braking operation may have been performed, and shifts to the first standby state (FIG. 5B). Period I).

After the shift to the first standby state, the ECU 10 sets a time t ₂ − until the change speed ΔP _{M / C} of the master cylinder pressure P _{M / C} becomes equal to or less than the second predetermined speed THΔP2.
t ₁ = CSTANBY1 is counted. And ECU1
When the elapsed time CSTANBY1 is within a predetermined range, the CPU determines that the emergency braking operation has been performed by the driver and shifts to the second standby state (period II shown in FIG. 5B).

The braking force control apparatus according to the present embodiment appropriately determines the timing for starting the BA control after the time t ₁ when the emergency braking operation is detected, that is, after shifting to the second standby state. Thus, the wheel cylinder pressure P _{W / C} can be quickly increased. Hereinafter, such features will be described. FIG. 5 (B)
A curve shown by a broken line in FIG. 7 represents a change in the wheel cylinder pressure P _{W / C} obtained when the BA control is started immediately at time t ₁ . On the other hand, the curve shows a change in P _{W / C} when the normal brake control is maintained at time t ₁ . As can be seen from the curves and at the initial stage of the boosting process, it is understood that the wheel cylinder pressure P _{W / C} can be rapidly increased by maintaining the normal brake control.

That is, the wheel cylinder pressure P_{W / C}of
As shown in FIG.
Time t when it was determined that the key operation was performed₁At
Is P _{M / C}And P_{W / C}Differential pressure P between_diffHas occurred
The master cylinder pressure P_{M / C}Is not boosted
If normal control is maintained, a relatively large amount of brake fluid
From the hydraulic booster 36 to the wheel cylinders 120-1
26. On the other hand, the foil from the accumulator 28
Brake fluid that can be supplied to cylinders 120 to 126
Depends on the capacity of the accumulator 28 and the capacity of the pump 24.
It is restricted by force. Therefore, the master cylinder P_{M / C}When
Wheel cylinder pressure P_{W / C}Large differential pressure P between_diffIs raw
Is in the normal
Maintaining the rake control will promptly increase the wheel cylinder pressure.
P_{W / C}Can be boosted.

Therefore, in the braking force control device of this embodiment, in order to quickly increase the wheel cylinder pressure P _{W / C} after the emergency braking operation is performed, the wheel obtained when the normal control is maintained is obtained. rate of rise [Delta] P W _{/ C} of the cylinder pressure P _{W / C,} when large compared to the rate of rise [Delta] P W _{/ C} obtained after starting the BA control, it is desirable not to start the BA control.

In this case, it is conceivable that the BA control is started after a predetermined delay time elapses after the emergency braking operation is performed. When executed, the following inconveniences occur. FIG. 6 shows the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C} in the case where the additional depression emergency braking operation is executed, by curves and respectively. In addition,
FIG. 6 shows a case where an emergency brake operation is performed from a state where the brake pedal is not operated for comparison (hereinafter, a case where the brake pedal is not operated).
The PM _{/ C} and _{PW / C} of such an emergency brake operation are referred to as a normal emergency brake operation. As shown in FIG. 6, each of the emergency brake operation is detected at time T ₁ and T _2.

If the emergency brake operation is performed by increasing the number of steps,
In the case of normal braking, a certain amount of
キ Fluid comes from the hydro booster 36
, And is supplied to the power supply 120-126. Therefore, FIG.
Wheel cylinder pressure P as shown _{W / C}Is P_nUp to
I have. Therefore, the emergency braking operation with further depression was performed.
If a normal emergency braking operation is performed
In the process of executing the emergency braking operation,
Il cylinder pressure P_{W / C}Is boosted relatively quickly. This
Time T_TwoWheel cylinder P at_{W / C}Master series
Pressure P_{M / C}Differential pressure P_{diff, 2}Is the time T₁Differential pressure P at
_{diff, 1}It is smaller than.

The pressure increase rate ΔP _{W / C} of the wheel cylinder pressure P _{W / C} when the hydraulic booster 36 is used as a hydraulic pressure source changes according to the differential pressure P _diff . That is, when the differential pressure P _diff is small, the flow rate of brake fluid per unit time that can flow from the hydro booster 34 to the wheel cylinders 120 to 126 decreases, so that the wheel cylinder pressure P _{diff
The W / C} is hardly boosted, and the boosting speed ΔP _{W / C} is reduced. Therefore, as in the case where the depression increases the emergency brake operation is performed, when the emergency brake operation is already pressure difference P _diff when it is detected is reduced smaller, as if the pressure difference P _{di ff} is greater If the BA control is started after waiting for a predetermined delay time, the wheel cylinder pressure P
Normal brake control is continued even though the _{W / C} cannot be quickly boosted. As a result, in such a case, P _{W / C} cannot be appropriately boosted.

To eliminate such inconvenience, the differential pressure P _diff
It is desirable to determine the timing of switching from the normal brake control to the BA control based on the above. Therefore, in the present embodiment, after the emergency brake operation is executed and the state shifts to the second standby state, the differential pressure P _diff between the master cylinder pressure PM _{/ C} and the wheel cylinder pressure P _{W / C} is set to a predetermined threshold L. At a time point (time t _{2 in} FIG. 5), the hydraulic pressure source is switched from the hydro booster 36 to the accumulator 28. Here, the threshold value L is a differential pressure P _diff such that the boosting speed ΔP _{W / C} when the accumulator 28 is used as a hydraulic pressure source exceeds the boosting speed ΔP _{W / C} when the hydraulic booster 36 is used as a hydraulic pressure source. Determined by experimental determination.

By using this method, it is possible to use the accumulator 28 as a hydraulic pressure source for the hydro booster 36.
When a state advantageous for promptly increasing the wheel cylinder pressure P _{W / C} is established as compared with using the hydraulic pressure source as the hydraulic pressure source, BA
Control can be started. This makes it possible to rapidly increase the wheel cylinder pressure P _{W / C} irrespective of whether the normal emergency braking operation is performed or whether the emergency braking operation is further performed.

[0067] Incidentally, as described above, the detection of the emergency braking operation, master cylinder pressure P _{M / C} of change rate [Delta] P M _{/ C}
It is performed based on. Therefore, the master cylinder pressure P _{W / C} at the time when the emergency brake operation is performed changes depending on how the driver depresses the brake pedal during the emergency brake operation. In the normal brake state, the wheel cylinder pressure P _{W / C} is equal to the master cylinder pressure P _{M / C}
Is boosted with the upper limit. Therefore, when the master cylinder pressure P _{M / C} is low, the value of the wheel cylinder pressure P _{W / C} that can be reached while maintaining the normal brake control is also limited to a small value. In such a case, the master cylinder pressure P _{M / C}
As compared with the case is large, even if occurring the same differential pressure P _diff, rate of rise [Delta] P W _{/ C} of the wheel cylinder pressure P _{W / C} is kept small. Therefore, if the normal brake control is maintained until the differential pressure P _diff decreases to a constant value when the master cylinder pressure P _{M / C} is low, as in the case where the master cylinder pressure P _{M / C} is high, the wheel cylinder The pressure P _{W / C} cannot be quickly increased.

Therefore, in this embodiment, the master serial
Pressure P_{M / C}Is smaller than the predetermined value A,
Value L to P_{M / C}Is kept the same as when the value is equal to or more than the predetermined value A.
The wheel cylinder pressure P_{W / C}Pressure rise speed ΔP_{W / C}But
Judge that it will be smaller and increase the threshold L
The greater the differential pressure P_diffAt the stage where
A control is to be started. Thus, the threshold L
Is the master cylinder pressure P _{M / C}By changing according to
BA control can be started at more appropriate timing
It works. As a result, the emergency braking operation was performed.
The wheel cylinder pressure P_{W / C}More quickly boosted
Can be made.

In order to determine the differential pressure P _diff between the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C} , it is necessary to detect the wheel cylinder pressure P _{W / C.} In the system, a sensor for detecting the wheel cylinder pressure P _{W / C} is not provided in order to reduce the cost of the apparatus. Therefore, in the present embodiment, the ECU 10
Wheel cylinder pressure P based on master cylinder pressure P _{M / C
W / C} is estimated and calculated. Hereinafter, the principle of the estimation calculation of the wheel cylinder pressure P _{W / C} will be described.

FIG. 7 shows the relationship between the total brake fluid amount Q _total supplied from the hydro booster 36 to the wheel cylinders 120 to 126 and the wheel cylinder pressure P _{W / C.}
As shown in FIG. 7, the wheel cylinder pressure P _{W / C} exhibits a characteristic that increases as the _total brake fluid amount Q _total increases. Therefore, if the total brake fluid amount Q _total is obtained, P _{W / C} can be estimated from Q _total using the relationship shown in FIG. Therefore, in this embodiment, first, the total brake fluid amount Q _total is obtained based on the master cylinder pressure P _{M / C} , and then Q
P _{W / C} is estimated from the _total . In order to simplify the calculations in this example, as shown by the broken line in FIG. 7, Q _total and P _{W / C} linear relationship of two of J: P W _{/ C}
= P · Q _{tota l, and, K: P W / C =} q · Q total + r
In approximation, seeking P _{W / C} by P _W / C = Max _{[p · Q total, q · Q} total + r ] (10). Here, Max [] is a function that gives the maximum value of the arguments.

The estimation of the _total brake fluid amount Q _total based on the master cylinder pressure P _{M / C} is based on the flow rate ΔQ of the brake fluid exchanged between the hydro booster 34 and each of the wheel cylinders 120 to 126 per unit time, This is performed by using the following relationship: ΔQ = k · √ | PM _{/ C} − _{PW / C} | (11) is established between the master cylinder pressure PM _{/ C} and the wheel cylinder pressure _{PW / C.} . That is,
According to equation (11), ΔQ is calculated for each unit time,
By calculating the cumulative sum of the values of Q, Q _total can be calculated. The wheel cylinder pressure P _{W / C} is estimated from the thus obtained Q _total according to the equation (10).

The change in wheel cylinder pressure P _{W / C} shown in FIG. 5 is realized by starting the BA control in the above-described manner. According to the above method, as shown in FIG. 5, after the emergency braking operation is started by the driver, the wheel cylinder pressure P _{W / C} can be quickly and efficiently increased. Hereinafter, with reference to FIG. 8 to FIG. 11, the contents of processing executed by the ECU 10 to realize the above function will be described.

FIG. 8 is a flowchart showing an example of a control routine executed by the ECU 10 to determine conditions for shifting to the first standby state and to determine conditions for maintaining the first standby state. The routine shown in FIG. 8 is a periodic interruption routine that is started every predetermined time. When the routine shown in FIG. 8 is started, first, the process of step 200 is executed.

In step 200, the flag XSTANB
It is determined whether or not Y1 is on. XSTAN
BY1 is a flag that is turned on when a condition for shifting to the first standby state is satisfied. Therefore, when the condition for shifting to the first standby state is not satisfied, it is determined that XSTANBY1 = ON is not satisfied. In this case, the process of step 202 is executed next.

In step 202, the first predetermined amount THP1 and the first predetermined speed THΔP are set according to the driving state of the vehicle.
1, and a noise cut value THNC are set. The first predetermined amount THP1, the first predetermined speed THΔP1, and the noise cut value THNC are threshold values used for determining a transition condition to the first standby state. In the present embodiment, the ECU 10 determines that the master cylinder pressure P _{M / C} and its change speed ΔP _{M / C} are
P _{M / C} ≧ THP1, and THΔP1 <ΔP _{M / C} <T
When both conditions of the HNC are satisfied, it is determined that the condition for shifting to the first standby state is satisfied.

In step 202, THP1,
THΔP1 and THNC are the vehicle speed SPD and the elapsed time T after the brake switch 14 is turned on.
Based on _STOP , it is set as shown in Table 1 below.

[0077]

[Table 1]

The first predetermined amount THP1 is shown in Table 1 above.
As described above, the vehicle speed SPD is equal to the predetermined speed V.₀If it is more than specified
The quantity THP1L is set. Also, the vehicle speed SPD is a predetermined speed.
Degree V ₀Is less than the predetermined amount THP1H
You. THP1L and THP1H are THP1L <TH
It is set so that the relationship of P1H is established. First
When the predetermined amount THP1 is set to the value shown in Table 1 above,
P which is one of the conditions for shifting to the one standby state_{M / C}≧ T
HP1 is easily established during high-speed running and at low-speed running.
It is difficult to be established.

When the vehicle is running at a low speed, it is less necessary to quickly increase the braking force than when the vehicle is running at a high speed. In addition, during low-speed running, deceleration during braking is more easily felt than during high-speed running. Therefore, it is appropriate that the BA control is less likely to be started when the vehicle is running at a low speed than when the vehicle is running at a high speed.
Such a request can be realized by setting the first predetermined amount THP1 to the value shown in Table 1 above.

The first predetermined speed THΔP1 is shown in Table 1 above.
As shown, the vehicle speed SPD is equal to the predetermined speed V. ₀That's all
First, the progress after the brake switch 14 is turned on.
Time T _STOPIs a predetermined time T₀If not reached the specified speed
The degree THΔP1H is set. Also, the vehicle speed SPD is
Speed V₀If not, set to the predetermined speed THΔP1M
Is done. THΔP1H and THΔP1M are THΔP
1H> THΔP1M is set to be established.
I have. The first predetermined speed THΔP1 is set as described above.
Then, one of the conditions for shifting to the first standby state is T.
HΔP1 ≦ P_{M / C}Is difficult to be established during high-speed driving, and
It becomes easier to be established at low speeds.

The driver of the vehicle operates the brake pedal 12 at a higher speed when performing an emergency brake operation during high-speed traveling than when performing an emergency brake operation during low-speed traveling.
Therefore, when the vehicle speed SPD is low, the threshold value THΔP1 for judging the presence or absence of the emergency braking operation is set to a relatively small value, and when the vehicle speed SPD is high, the threshold value THΔP1 is set to A relatively large value is appropriate. The first predetermined speed THΔP1 is determined according to Table 1 above.
By setting to the value shown in (1), such a request can be realized.

As shown in Table 1, the first predetermined speed THΔP1 is a predetermined time T _STOP after the vehicle speed SPD is equal to or higher than the predetermined speed V ₀ and the elapsed time T _STOP after the brake switch 14 is turned on. When the time is equal to or longer than the time T _0, that is, when the time T ₀ has elapsed after the brake operation is started, the predetermined speed THΔP1L is set. T
HΔP1L is a smaller value than THΔP1M. When the first predetermined speed THΔP1 is set as described above, one of the conditions for shifting to the first standby state is TH.
ΔP1 ≦ P _{M / C} is equal to T _STOP ≧ T ₀ and then T _STOP
It is easier to be satisfied than before ≧ T ₀ is satisfied.

In a vehicle, an emergency braking operation may be started at a point in time when a certain period of time has passed after the braking operation was started. In this case, since the brake pedal 12 is already depressed when the emergency brake operation is started, the change speed ΔP _{M / C} generated after the emergency brake operation is started is unlikely to be high. Therefore, in order to accurately detect such an emergency brake operation, after a lapse of a certain period of time from the start of the brake operation, the first predetermined speed, which is a threshold value for determining the presence or absence of the emergency brake operation, is set. It is appropriate to set THΔP1 to a value smaller than the previous value. First predetermined speed THΔ
By setting P1 to the value shown in Table 1 above, such a request can be realized.

The noise cut value THNC is shown in Table 1 above.
As described above, the vehicle speed SPD is the predetermined speed V₀That is all, and
Elapsed time T after the brake operation was started_STOPAt a given time
Interval T ₀If not reached, set to the predetermined value THNCH
It is. When the vehicle speed SPD is equal to the predetermined speed V₀That's all
Elapsed time T_STOPIs a predetermined time T₀If it is more than
And the vehicle speed SPD is the predetermined speed V₀Prescribed if less than
The speed is set to THNCL. THNCH and THN
CL is set so that the relationship of THNCH> THNCL is satisfied.
Is set to

SPD ≧ V ₀ holds, and T _STOP ≧ T
_{If 0} is not established, as described above, a large change speed ΔP _{M / C} is generated with the emergency braking operation. Therefore,
In this case, it is appropriate to treat a relatively large change rate ΔP _{M / C} as effective data. On the other hand, if both SPD ≧ V ₀ and T _STOP ≧ T ₀ hold, and SP
When D <V ₀ holds, as described above, it is difficult for the change speed ΔP _{M / C to} become a large value with the emergency brake operation.
Therefore, in this case, it is appropriate to treat the relatively large change speed ΔP _{M / C} as an abnormal value. Noise cut value T
By setting the HNC to the value shown in Table 1 above, such a request can be realized.

According to the above method, the first predetermined amount THP
After setting the first predetermined speed THΔP1 and the noise cut value THNC, the process of step 204 is executed. In step 204, it is determined whether or not the master cylinder pressure PM _{/ C} is equal to or greater than a first predetermined amount THP1. As a result, if it is determined that PM _{/ C} ≧ THP1 is not satisfied, it is determined that the condition for shifting to the first standby state is not satisfied, and the current routine is ended. On the other hand, if it is determined that PM _{/ C} ≧ THP1, the process of step 206 is performed.

At step 206, the change speed ΔP
_It is determined whether _{M / C} is larger than the first predetermined speed THΔP1 and smaller than the noise cut value THNC. As a result, THΔP1 <ΔP _{M / C} <THNC
Is not satisfied, it is determined that the condition for shifting to the first standby state is not satisfied, and the current routine is terminated. On the other hand, when it is determined that the above condition is satisfied, the process of step 208 is executed next.

At step 208, a flag XST is set to indicate that the condition for shifting to the first standby state has been satisfied.
ANBY1 is turned on. When the process of step 208 is completed, the current routine is completed. When this routine is started after the flag XSTANBY1 is turned on in step 208, it is determined that XSTANBY1 = ON is established in step 200. In this case, step 200 is followed by step 2
Ten processes are executed.

At step 210, the counter CSTAN
A process of incrementing BY1 is performed. The counter CSTANBY1 is a counter for counting an elapsed time after a condition for shifting to the first standby state is satisfied. The count time of the counter CSTANBY1 has been reset to "0" by initial processing when the vehicle is started. When the process of step 210 is completed, the process of step 212 is performed next.

In step 212, the counter CSTAN
It is determined whether or not the time counted by BY1 is equal to or less than the predetermined time α. The predetermined time α is a smaller value than the time during which the change speed ΔP _{M / C} is maintained at a large value when the emergency braking operation is performed. As a result of the above determination, C
If it is determined that STANBY1 ≦ α is satisfied, the process of step 214 is executed next.

In step 214, it is determined whether or not the change speed ΔP _{M / C} is lower than a predetermined value β. As a result, when ΔP _{M / C} <β is satisfied, it is determined that the change speed ΔP _{M / C} becomes a small value after a very short time after the condition for shifting to the first standby state is satisfied. it can. In this case, it is determined that the driver's brake operation was not an emergency brake operation, and the process of step 216 is executed.

In step 216, a process for turning off the flag XSTANBY1 to release the first standby state is executed. After the process of step 216 is performed, the process of step 218 is performed next. In step 218, a process of resetting the count time of the counter CSTANBY1 to “0” is executed. This step 2
When the process of 18 ends, the current routine ends.

In this routine, the above step 212
If it is determined that CSTANBY1 ≦ α is not established in step S214, and if it is determined that ΔP _{M / C} <β is not established in step 214, the condition for shifting to the first standby state is satisfied. Change rate ΔP during time
It can be determined that the phenomenon that the _{M / C} decreases to a small value has not occurred. In this case, the process of step 220 is executed next.

In step 220, the counter CSTAN
It is determined whether the count value of BY1 is equal to or longer than a second predetermined time THT2. The second predetermined time THT2 is a value that defines an upper limit value of the time for maintaining the first standby state after the condition for shifting to the first standby state is satisfied. Therefore, in this step 220, CSTANBY1 ≧ THT2
Is established, it can be determined that the duration of the first standby state has reached the upper limit. In this case, next, after the processing of steps 216 and 218 is executed, the current routine is terminated. On the other hand, if it is determined in this step 220 that CSTANBY1 ≧ TH2 is not satisfied, it can be determined that the duration of the first standby state has not yet reached the upper limit.
In this case, the process of step 222 is executed next.

At step 222, the flag XSTANB
It is determined whether or not Y2 is on. Flag XS
TANBY2 is the second routine in another routine described later.
This flag is turned on when it is determined that the condition for shifting to the standby state is satisfied. XSTANBY2
If it is determined that = ON is established, it is determined that it is not necessary to maintain the first standby state. In this case, next, after the processing of steps 216 and 218 is executed, the current routine is terminated. On the other hand, XSTAN
When it is determined that BY2 = ON is not established, it is determined that the first standby state needs to be maintained. In this case, the current routine is terminated without any further processing.

FIG. 9 is a flowchart illustrating an example of a control routine executed by the ECU 10 to determine a condition for shifting to the second standby state. The routine shown in FIG. 9 is a periodic interruption routine that is started every predetermined time. When the routine shown in FIG. 9 is started, first, the process of step 230 is executed. In step 230, the counting time of the counter CSTANBY1, that is, the elapsed time after the condition for shifting to the first standby state is satisfied, is
It is determined whether it is longer than the first predetermined time THT1 and shorter than the second predetermined time THT2. The second predetermined time is the upper limit of the time during which the first standby state is to be maintained, as described above. On the other hand, the first predetermined time THT1
Is a value that determines the lower limit time during which the high-speed operation of the brake pedal 12 continues when the emergency brake operation is performed.

Therefore, in the braking force control device of this embodiment, after the brake operation is started, THT1 ≦ CST
If the operation speed of the brake pedal 12 becomes a sufficiently small value before ANBY1 is established, it can be determined that the brake operation is not an emergency brake operation. In the above step 230, THT1 ≦ CSTANB
If it is determined that Y1 ≦ THT2 is not satisfied, the current routine is terminated without any further processing. On the other hand, when it is determined that the above condition is satisfied, the process of step 232 is executed next.

In step 232, the rate of change ΔP
_It is determined whether the _{M / C} has changed from a speed exceeding the second predetermined speed THΔP2 to a speed equal to or lower than the second predetermined speed THΔP2. The second predetermined speed THΔP2 determines whether or not the master cylinder pressure P _{M / C} is rapidly increasing, that is,
This is a threshold value for determining whether or not the brake pedal 12 is operated at a high speed.

In step 232, the change rate ΔP is calculated from the previous processing cycle to the current processing cycle.
If it is determined that the _{M / C} has not changed from a speed exceeding THΔP2 to a speed equal to or less than THΔP2, it is necessary that the high-speed operation period of the brake pedal 12 has not ended from the previous processing cycle to the current processing cycle. You can judge. In this case, the current routine is terminated without any further processing.

On the other hand, if it is determined in step 232 that the change speed ΔP _{M / C} has changed from a speed exceeding THΔP2 to a speed equal to or lower than THΔP2 from the previous processing cycle to the current processing cycle, It can be determined that the high-speed operation period of the brake pedal 12 has ended from the processing cycle of the above to the current processing cycle. In this case, the process of step 234 is executed next.

In step 234, the maximum value _{PM / CMAX of} the master cylinder pressure _{PM / C} detected after the condition for shifting to the first standby state is satisfied, and the master cylinder pressure immediately after the condition in step 232 is satisfied. The difference from pressure P _{M / C} "P
_It is determined whether or not “ _{M / CMAX−} P _{M / C} ” is smaller than the predetermined value γ. As a result, if it is determined that _{PM / CMAX−} P _{M / C} <γ holds, It can be determined that a large pedaling force F is being applied to the brake pedal 12. In this case, the process of step 236 is executed next, while the condition of step 234 is not satisfied. Can determine that the depression of the brake pedal 12 has already been loosened, in which case the current routine is terminated without proceeding with the process of shifting to the second standby state.

At step 236, a flag XST is set to indicate that the condition for shifting to the second standby state has been satisfied.
ANBY2 is turned on. When the process of step 236 ends, the current routine ends. FIG.
Is EC to determine the condition for starting BA control.
4 shows a flowchart of an example of a control routine executed by U10. The routine shown in FIG. 10 is a periodic interruption routine that is started every predetermined time. When the routine shown in FIG. 10 is started, first, the process of step 240 is executed.

At step 240, the master cylinder pressure P _{M / C} is read from the hydraulic pressure sensor 144. Step 2
When the process at 40 is completed, next, at step 242, an estimation calculation of the wheel cylinder pressure P _{W / C} is performed.
The details of the processing of the estimation calculation of P _{W / C} will be described later. When the processing in step 242 is completed,
4 is executed.

At step 244, the flag XSTANB
It is determined whether or not Y2 is on. as a result,
When it is determined that XSTANBY2 = ON is not established, it is determined that it is not necessary to start the BA control. In this case, thereafter, the current routine ends without performing any processing. On the other hand, in step 244, XS
If it is determined that TANBY2 = ON is satisfied, the process of step 246 is performed next. Step 246
Then, it is determined whether or not the master cylinder pressure PM _{/ C} is smaller than the predetermined value A. As a result, if P _{M / C} <A holds, then at step 248, the threshold L
Is substituted for β. On the other hand, if P _{M / C} <A does not hold, β is substituted for the threshold L in step 250. Here, α and β are constants having a relation of α <β. Therefore, when the wheel cylinder pressure P _{W / C} is smaller than the predetermined value A, the threshold value L is set smaller than when the wheel cylinder pressure P _{W / C} is equal to or larger than the predetermined value A.

When the processes of steps 248 and 250 are completed, the process of step 252 is executed.
In step 252, it is determined whether (PM _{/ C- PW / C} ) (= _Pdiff ) is smaller than the threshold value L. Step 2
If it is determined in step 52 that (PM _{/ C- PW / C} ) <L holds, it is determined that the timing to start the BA control has come, and the process of step 254 is executed.
On the other hand, in step 252, (P _{M / C} −P _{W / C} ) <L
Is determined not to be established, it is determined that the timing to start the BA control has not yet arrived, and the current routine ends without performing any processing thereafter.

In step 254, a process for bringing the braking force control device into the BA operating state is executed to start the BA control. After the process of step 254 is executed,
Wheel cylinder pressure P of wheel cylinders 120 to 126
_{The W / C} is boosted using the accumulator 28 as a hydraulic pressure source. When the process of step 254 is completed, the current routine is completed.

Next, referring to FIG.
The details of the processing for estimating the wheel cylinder pressure P _{W / C} executed in 42 will be described. FIG. 11 is a flowchart of the wheel cylinder pressure estimation calculation routine executed in step 242. When the routine shown in FIG. 11 is started, first, the process of step 260 is executed. In step 260, it is determined whether or not it is time to return from the ABS operation state or the BA operation state to the normal brake state. As described above, in the normal braking state, SA- ₁ 86, SA- ₂ 88, SA- ₃ 90, and STR
All 94 are turned off. On the other hand, in the ABS operating state or the BA operating state, at least one of these solenoids is turned on. Therefore, the above-described determination in step 260 is performed based on SA _- 186 and SA- _28.
This is performed by detecting that at least one of 8, SA- ₃ 90, and STR 94 has been switched from the ON state to the OFF state.

As described above, in the present embodiment, the estimation of the wheel cylinder pressure P _{W / C} is based on the hydro booster 36.
Is performed on the basis of the total brake fluid amount Q _total supplied to the wheel cylinders 120 to 126 from. However, in the ABS operating state or the BA operating state,
Hydro booster 36 and wheel cylinders 120 to 126
Therefore, Q _total cannot be calculated correctly because conduction between the two may be interrupted. Therefore, the wheel cylinder pressure P _{W / C} estimated and calculated has an incorrect value at the time of returning from the ABS operation state or the BA operation state to the normal brake state.

Therefore, in step 260, ABS
From operating state or BA operating state to normal brake state
If it is determined that it is time to return,
In step 262, the wheel cylinder pressure P_{W / C}First
The current master cylinder pressure P as the period value_{M / C}Is assigned the value of
It is. When the processing in step 262 is completed, the next step
In step 264, the inverse calculation of the relationship of equation (10) is performed.
, Ie, Q _total= Min [P_{W / C}/ P, P
_{W / C}/ Qr] by using the relationship _totalof
An initial value is calculated. Where Min [] is the argument
This function gives the minimum value. Step 264 is completed
Upon completion, the current routine ends. On the other hand,
In step 260, it is determined that the above condition is not satisfied.
In this case, the estimation calculation process after step 266 is executed.
It is.

In step 266, it is determined whether P _{M / C} is equal to or greater than P _{W / C.} As a result, P _{M / C} ≧ P _{W / C}
Is established, it is determined that the brake fluid is flowing from the hydro booster 36 into the wheel cylinders 120 to 126. In this case, next, in step 268, Q _total is changed to a flow rate ΔQ = k√ (PM _{/ C} -P
_{W / C} ). On the other hand, if it is determined in step 266 that P _{M / C} ≧ P _{W / C} is not established, the brake fluid
It is determined that the liquid has flowed out to the hydraulic booster 36 from. In this case, next in step 270, Q
A process of reducing _total by k√ (P _{W / C} −P _{M / C} ) is executed.

When the processes of steps 268 and 270 are completed, the process of step 272 is executed.
In step 272, Q is calculated using the relationship of the above equation (10).
The value of P _{W / C} is estimated from the _total . When the process of step 272 is completed, the current routine is completed. As described above, in the present embodiment, the master cylinder pressure P _{M / C}
By starting the BA control at the stage when the differential pressure P _diff between the wheel cylinder pressure P _{W / C} and the wheel cylinder pressure P _{W / C} falls below a predetermined threshold value,
The wheel cylinder pressure P _{W / C} can be appropriately increased. Further, by changing the threshold value according to the master cylinder pressure P _{M / C} , the BA control can be started at a more appropriate timing.

Therefore, according to the braking force control apparatus of this embodiment, in order to quickly increase the wheel cylinder pressure P _{W / C} , the hydraulic booster 36 is used as the hydraulic pressure source when the accumulator 28 is used as the hydraulic pressure source. It is possible to accurately determine the time point at which the state becomes more advantageous than the above, and to start the BA control at this time point. This makes it possible to appropriately realize a rapid increase in the wheel cylinder pressure P _{W / C} according to various situations.

In the above embodiment, the ECU 10
8 and 9 by executing the routine shown in FIGS. 8 and 9, the ECU 10 executes the processing of steps 252 and 254, and the ECU 10 executes the processing of steps 252 and 254. The above-described control start differential pressure determination means is realized by executing the process of S250.

Next, a second embodiment of the present embodiment will be described with reference to FIGS. FIG. 12 is a system configuration diagram of a pump-up type braking force control device (hereinafter, simply referred to as a braking force control device) according to a second embodiment of the present invention. 12, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

The braking force control device of this embodiment is a device suitable as a braking force control device for a front engine / rear drive type vehicle (FR vehicle). The braking force control device according to the present embodiment is controlled by the ECU 10. ECU10
Controls the operation of the braking force control device by executing the control routine shown in FIGS. 8 to 10 as in the case of the first embodiment described above.

The braking force control device has a brake pedal 12. A brake switch 14 is provided near the brake pedal 12. The ECU 10 controls the brake pedal 1 based on the output signal of the brake switch 14.
It is determined whether or not 2 is depressed. The brake pedal 12 is connected to the vacuum booster 300. The vacuum booster 300 is connected to the brake pedal 12.
When is depressed, an assist force Fa having a predetermined boosting ratio with respect to the brake depression force F is generated. The master cylinder 302 is fixed to the vacuum booster 300. The master cylinder 302 is a center valve conventional type master cylinder, and includes a first hydraulic chamber 304 and a second hydraulic chamber 306 therein. The first hydraulic chamber 304 and the second hydraulic chamber 306 include:
A master cylinder pressure P _{M / C} is generated according to the resultant force of the brake depression force F and the assist force Fa.

A reservoir tank 308 is provided above the master cylinder 302. Reservoir tank 308
, A front reservoir passage 310 and a rear reservoir passage 312 communicate with each other. A front reservoir cut solenoid 314 is provided in the front reservoir passage 310.
(Hereinafter, referred to as SRCF 314). Similarly, a rear reservoir cut solenoid 316 (hereinafter, referred to as SRCR 316) communicates with the rear reservoir passage 312.

The SRCF 314 is further connected to a front pump passage 318. Similarly, SRCR 316
Is connected to a rear pump passage 320. SRCF
Reference numeral 314 denotes a two-position solenoid valve which shuts off the front reservoir passage 310 and the front pump passage 318 when turned off, and conducts them when turned on. The SRCR 316 is a two-position solenoid valve that shuts off the rear reservoir passage 312 and the rear pump passage 320 when turned off, and conducts them when turned on.

First hydraulic chamber 30 of master cylinder 302
A first hydraulic passage 322 and a second hydraulic passage 324 communicate with the fourth hydraulic chamber 306 and the second hydraulic chamber 306, respectively. The first hydraulic passage 322 includes a right front master cut solenoid 326 (hereinafter, referred to as SMFR 326), and
Left front master cut solenoid 328 (hereinafter referred to as SMFL3
28). On the other hand, the second hydraulic passage 32
4 has a rear master cut solenoid 330 (hereinafter referred to as S
MR330).

A hydraulic passage 332 provided corresponding to the right front wheel FR communicates with the SMFR 326. Similarly,
A hydraulic passage 334 provided corresponding to the left front wheel FL communicates with the SMFL 328. Further, a hydraulic passage 336 provided corresponding to the left and right rear wheels RL, RR communicates with the SMR 330. SMFR326, SMFL32
8 and the SMR 330 are provided with constant pressure release valves 338, 340, and 342, respectively. SMFR3
Reference numeral 26 denotes a state in which the first hydraulic pressure passage 322 and the hydraulic pressure passage 332 are electrically connected when turned off, and the first hydraulic pressure passage 32 through the constant pressure release valve 338 when turned on.
2 is a two-position solenoid valve for communicating the fluid passage 2 with the hydraulic passage 332. When the SMFL 326 is turned off, the first hydraulic passage 322 and the hydraulic passage 334 are brought into a conductive state, and when the SMFL 326 is turned on, the first hydraulic passage 340 is connected via a constant pressure release valve 340. The solenoid valve is a two-position solenoid valve that connects the fluid passage 322 and the hydraulic passage 334. Similarly, SMR 330
When turned off, the second hydraulic passage 324 and the hydraulic passage 336 are brought into conduction, and when turned on, the second hydraulic passage 324 and the hydraulic passage are connected via the constant pressure release valve 342. 336 is a two-position solenoid valve that communicates with 336.

Between the first hydraulic passage 322 and the hydraulic passage 332, the hydraulic passage 33 extends from the first hydraulic passage 322 side.
Check valve 34 that allows only fluid flow toward side 2
4 are provided. Similarly, a first hydraulic passage 322 is provided between the first hydraulic passage 322 and the hydraulic passage 334 and between the second hydraulic passage 324 and the hydraulic passage 336.
A check valve 346 that allows only the flow of the fluid from the side to the hydraulic passage 334 and a check valve 348 that allows only the flow of the fluid from the second hydraulic passage 324 to the hydraulic passage 336. It is arranged.

Hydraulic passages 3 provided corresponding to the left and right front wheels
As in the case of the first embodiment, the holding solenoid S ** H, the pressure reducing solenoid S ** R, the wheel cylinders 120 to 126 and check valves 128-134 are in communication. The left and right front wheel holding solenoid SFR
A front pressure reducing passage 350 communicates with R112 and SFLR114. Further, a rear pressure reducing passage 352 communicates with the holding solenoids SRRR116 and SRLR118 of the left and right rear wheels.

A front reservoir 354 and a rear reservoir 355 communicate with the front pressure reducing passage 350 and the rear pressure reducing passage 352, respectively. The front reservoir 354 and the rear reservoir 355 each include a check valve 3
The suction side of the front pump 360 through 56, 358,
And, it communicates with the suction side of the rear pump 362. The discharge side of the front pump 360 and the rear pump 36
2 is provided with a damper 3 for absorbing the pulsation of the discharge pressure.
64,366. The damper 364 includes a front right pump passage 368 provided corresponding to the front right wheel FR and a front left pump passage 370 provided corresponding to the front left wheel FL.
Is in communication with On the other hand, the damper 366 is
It communicates with 6.

The front right pump passage 368 communicates with the hydraulic passage 332 via a front right pump solenoid 372 (hereinafter, referred to as SPFL 372). The front left pump passage 370 is connected to a front left pump solenoid 374 (hereinafter, SPF).
R374) to the hydraulic passage 334. The SPFL 372 is a two-position solenoid valve that brings the right front pump passage 368 and the hydraulic passage 332 into conduction when turned off, and shuts off when turned on. Similarly, SPFR37
4 is a left front pump passage 37
The solenoid valve is a two-position solenoid valve that establishes a continuity state between the hydraulic pressure passage 334 and the hydraulic pressure passage 334 and, when turned on, shuts them off.

Between the hydraulic passage 332 and the right front pump passage 368, the right front pump passage 368 is connected from the hydraulic passage 332 side.
Constant pressure release valve 376 that allows only the fluid flow toward the side
Are arranged. Similarly, between the hydraulic passage 334 and the left front pump passage 370, a constant pressure release valve 378 that allows only the flow of the fluid from the hydraulic passage 334 toward the left front pump passage 370 is provided.

In the vicinity of each wheel, a wheel speed sensor 136,
138, 140, 142 are provided. ECU10
Detects the rotational speed V _W of each wheel based on the output signal of the wheel speed sensors 136-142. Further, a hydraulic pressure sensor 144 is provided in the second hydraulic pressure passage 324 communicating with the master cylinder 302. The ECU 10 detects the master cylinder pressure PM _{/ C} based on the output signal of the hydraulic pressure sensor 144.

Next, the operation of the braking force control device of this embodiment will be described. The braking force control device according to the present embodiment switches the state of various solenoid valves provided in the hydraulic circuit to provide a normal brake function, an ABS function, and a B function.
A function is realized. The normal braking function is realized by turning off all solenoid valves provided in the braking force control device as shown in FIG. Hereinafter, the state shown in FIG. 12 is referred to as a normal brake state. Further, control for realizing the normal brake function in the braking force control device is referred to as normal brake control.

In the normal braking state shown in FIG.
Wheel cylinders 120, 122 for left and right front wheels FL, FR
Are both connected to the master cylinder 3 via the first hydraulic passage 322.
02 communicates with the first hydraulic chamber 304. The wheel cylinders 124, 126 of the left and right rear wheels RL, RR are
The hydraulic pressure passage 324 communicates with the second hydraulic chamber 306 of the master cylinder 302. In this case, the wheel cylinder pressure P _{W / C} of the wheel cylinders 120 to 126 is controlled to be always equal to the master cylinder pressure P _{M / C.} Therefore, FIG.
According to the state shown in FIG. 2, the normal braking function is realized.

In the ABS function, in the state shown in FIG. 12, the front pump 360 and the rear pump 362 are turned on, and the holding solenoid S ** H and the pressure reducing solenoid S ** R are appropriately driven in accordance with the request of the ABS. It is realized by doing. Hereinafter, control for realizing the ABS function in the braking force control device is referred to as ABS control.

The ECU 10 starts the ABS control when the vehicle is in a braking state and an excessive slip ratio is detected for any of the wheels. The ABS control is started in a situation where the brake pedal 12 is depressed, that is, in a situation where the master cylinder 302 is generating a high master cylinder pressure PM _{/ C.} During the execution of the ABS control, the master cylinder pressure P _{M / C} is supplied via the first hydraulic pressure passage 322 and the second hydraulic pressure passage 324 to the hydraulic pressure passages 332, 334 provided corresponding to the left and right front wheels, respectively. and,
It is guided to a hydraulic passage 336 provided corresponding to the left and right rear wheels. Therefore, when the holding solenoid S ** H is opened and the pressure reducing solenoid S ** R is closed in such a situation, the wheel cylinder pressure P _{W / C} of each wheel can be increased. Hereinafter, this state is referred to as (i) pressure increase mode.

When both the holding solenoid S ** H and the pressure reducing solenoid S ** R are closed during the execution of the ABS control, the wheel cylinder pressure P _{W / C} of each wheel can be held. . Hereinafter, this state is referred to as (ii) holding mode. Further, during the execution of the ABS control, the holding solenoid S ** H is closed, and the pressure reducing solenoid S ** is closed.
When R is in the valve open state, the wheel cylinder pressure P of each wheel
_{W / C} can be reduced. Hereinafter, this state is referred to as (iii)
This is called a decompression mode.

During the ABS control, the ECU 10 controls the slip state of each wheel so that the above-mentioned (i) pressure increasing mode, (ii) holding mode, and (iii) pressure reducing mode are appropriately realized for each wheel. , The holding solenoid S ** H and the pressure reducing solenoid S ** R are controlled. Holding solenoid S **
When H and the pressure reducing solenoid S ** R are controlled as described above, the wheel cylinder pressures P _{W / C of} all the wheels are controlled to appropriate pressures without generating an excessive slip ratio on the corresponding wheels. . Thus, according to the above control,
An ABS function can be realized in the braking force control device.

When the decompression mode is performed on each wheel during the execution of the ABS control, the brake fluid in the wheel cylinders 120 to 126 passes through the front depressurization passage 350 and the rear depressurization passage 352 and the front reservoir 354 and the rear reservoir 355. Flows into. Front reservoir 3
The brake fluid flowing into the reservoir 54 and the rear reservoir 355 is supplied to the front pump 360 and the rear pump 362.
And supplied to the hydraulic passages 332, 334, 336.

A part of the brake fluid supplied to the hydraulic passages 332, 334, 336 flows into the wheel cylinders 120 to 126 when the pressure increasing mode is performed in each wheel. The remainder of the brake fluid flows into the master cylinder 302 to compensate for the outflow of the brake fluid. Therefore, according to the system of the present embodiment, the ABS
Excessive stroke of the brake pedal 12 does not occur during execution of the control.

FIG. 13 shows a state of the braking force control device for realizing the BA function. That is, the BA function
As shown in FIG. 13, SRCF314, SRCR316
(Reservoir cut solenoid) and SMFR32
6, SMFL 328 and SMR 330 (master cut solenoid) are turned on, and the front pump 360
And by turning on the rear pump 362. Hereinafter, the state illustrated in FIG. 13 is referred to as a BA operation state.
Further, control for realizing the BA function in the braking force control device is referred to as BA control.

Also in this embodiment, as in the case of the first embodiment, when a large differential pressure P _diff occurs between the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C.} When the master cylinder 302 is used as a hydraulic pressure source, the wheel cylinder pressure P _{W / C} can be increased more quickly than when the front pump 360 and the rear pump 362 are used as a hydraulic pressure source. Further, even when a constant differential pressure P _diff is generated, the wheel cylinder pressure increasing speed ΔP _{W / C} that can be realized using the master cylinder 302 as a hydraulic pressure source decreases. Therefore, also in the present embodiment, the ECU 10 executes the routine shown in FIGS.
It is determined whether or not the driver has performed the emergency brake operation, and after the emergency brake operation is detected, the wheel cylinder pressure P is determined according to the routine shown in FIG.
_{In order} to increase the _{W / C} , the front pump 360 and the rear pump 36 are more expensive than using the master cylinder 302 as a hydraulic pressure source.
At the point in time when a state where it is advantageous to use 2 as the hydraulic pressure source is formed,
The braking force control device is set to the BA operation state.

When the braking force control device is brought into the BA operation state, the brake fluid stored in the reservoir tank 308 is supplied to the front pump 360 and the rear pump 362.
And supplied to the hydraulic passages 332, 334, 336. In the BA operating state, the hydraulic passages 332, 33
4,336 are constant pressure release valves 338,340,34.
2 until the pressure becomes higher than the master cylinder pressure P _{M / C} beyond the valve opening pressure of the master cylinder 302, the flow of fluid from the hydraulic passages 332, 334, 336 to the master cylinder 302 is reduced to SMF.
Blocked by R326, SMFL328, SMR330.

For this reason, when the BA control is started, a hydraulic pressure higher than the master cylinder pressure PM _{/ C} is generated in the hydraulic passages 332, 334, 336. In the BA operating state, the wheel cylinders 120 to 126 and the corresponding hydraulic passages 332, 334, 336 are maintained in a conductive state. Therefore, when the BA control is started, the wheel cylinder pressures P _{W / C} of all the wheels are immediately increased to a pressure exceeding the master cylinder pressure P _{M / C} using the front pump 360 or the rear pump 362 as a hydraulic pressure source. It is boosted.
As described above, according to the state shown in FIG. 13, the function of quickly increasing the braking force, that is, the BA function can be realized.

In the BA operating state shown in FIG. 13, the hydraulic passages 334, 332 and 336 are connected to the master cylinder 3 via check valves 344, 346 and 348, respectively.
02. Therefore, the master cylinder pressure P
_{If the M / C} is larger than the wheel cylinder pressure P _{W / C} of each wheel, the master cylinder
Can be used as a hydraulic pressure source to increase the wheel cylinder pressure P _{W / C.}

When the BA control is started in the braking force control device, thereafter, the wheel cylinder pressure P _{W / C of} each wheel is rapidly increased, so that an excessive slip ratio may occur in any one of the wheels. is there. In such a case, the ECU 10 starts the BA + ABS control. BA
In the + ABS control, among the SRCFs 314 and SRCRs 316 (reservoir cut solenoids) that are turned on when the BA control is started, the solenoid corresponding to the wheel in which an excessive slip ratio has occurred is turned off, and the holding solenoid S * * Of the H and pressure reducing solenoids, the solenoid corresponding to the wheel with the excessive slip ratio is A
This is realized by appropriately controlling according to the request of the BS.

FIG. 14 shows the state of the braking force control device for executing the BA + ABS control in which the left front wheel FL is the target wheel of the ABS control and the other wheels are the non-control target wheels of the ABS control. The state shown in FIG. 14 is realized when an excessive slip ratio occurs in the left front wheel FL prior to the other wheels after the BA control is started. Hereinafter, the state shown in FIG. 14 is referred to as a BA + ABS (FL) operation state. Control realized by bringing the braking force control device into the BA + ABS (FL) operating state is referred to as BA + ABS (FL) control.

[0142] The BA + ABS (FL) operating state is the SRC which has been turned on by the start of the BA control.
F314 (front reservoir cut solenoid) is turned off, and SFLH106 and SFLR114
Is appropriately controlled according to the request of the ABS. More specifically, the BA + ABS (FL) operation state is determined by SRCR 316, SMFR 326, SMFL 328.
And the SMR 330 are turned on, and the front pump 3
60 and the rear pump 362 are turned on, and the left front wheel FL is brought into a slip state so that the (i) pressure increasing mode, (ii) holding mode, and (iii) depressurizing mode are appropriately realized for the left front wheel FL. This is realized by controlling the SFLH 106 and the SFLR 114 accordingly.

In the BA + ABS (FL) operating state,
The rear pump 362 pressure-feeds the brake fluid sucked from the reservoir tank 308 as in the BA control.
The brake fluid pumped by the rear pump 362 is supplied to the wheel cylinders 124, 12 of the left and right rear wheels RL, RR.
6. According to the above control, the left and right rear wheels RL,
The wheel cylinder pressure P _{W / C} of RR continues to increase as in BA control.

The BA + ABS (FL) control is performed for the left front wheel FL.
(Ii) is started by executing the decompression mode. Therefore, the brake fluid flows into the front reservoir 354 at the same time when the BA + ABS (FL) control is started. In the BA + ABS (FL) operating state, the front pump 360 is connected to the front reservoir 3 as described above.
The brake fluid that has flowed into 54 is sucked and pumped.

The brake fluid pumped by the front pump 360 is mainly supplied to the wheel cylinder 120, and is also supplied to the wheel cylinder 122 when the (i) pressure increasing mode is executed at the left front wheel FL. According to the above control, the wheel cylinder pressure P _{W / C} of the right front wheel FR is BA
The voltage is continuously increased as in the control. Further, the wheel cylinder pressure P _{W / C} of the left front wheel FL is controlled to an appropriate value that does not cause an excessive slip ratio on the left front wheel FL.

As described above, according to the BA + ABS (FL) operating state, the wheel cylinder pressure P _{W / C} of the left front wheel FL, which is the target wheel of the ABS control, is adjusted to an appropriate value so as not to generate an excessive slip ratio on the left front wheel FL. While suppressing the pressure, the right front wheel FR and the left and right rear wheels RL,
The wheel cylinder pressure P _{W / C} of RR can be quickly increased in the same manner as in the BA control. Further, according to the braking force control device of the present embodiment, the wheels other than the left front wheel FL are ABS
Even in the case of the control target wheel, the BA function and the ABS function can be realized at the same time as in the case described above.

In the braking force control device according to the present embodiment, EC
U10 starts BA control in the same manner as in the first embodiment as described above. Therefore, according to the braking force control device of the present embodiment, similarly to the above-described braking force control device of the first embodiment, the emergency braking operation of the driver is accurately detected, and then the braking force is quickly increased. Can be launched.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 15 is a system configuration diagram of a pump-up type braking force control device (hereinafter, simply referred to as a braking force control device) corresponding to the third embodiment of the present invention. In FIG. 15, the same components as those shown in FIG. 12 are denoted by the same reference numerals, and description thereof will be omitted or simplified.

The braking force control device of the present embodiment is a device suitable as a braking force control device for a front engine / front drive type vehicle (FF vehicle). The braking force control device according to the present embodiment is controlled by the ECU 10. ECU
10 controls the operation of the braking force control device by executing the control routine shown in FIGS. 8 to 10 as in the first and second embodiments described above.

The braking force control device has a brake pedal 12. A brake switch 14 is provided near the brake pedal 12. The ECU 10 controls the brake pedal 1 based on the output signal of the brake switch 14.
It is determined whether or not 2 is depressed. The brake pedal 12 is connected to the vacuum booster 300. The vacuum booster 300 is fixed to the master cylinder 302. A first hydraulic chamber 304 and a second hydraulic chamber 306 are formed inside the master cylinder 302. First hydraulic chamber 304 and second hydraulic chamber 306
Inside the brake pedal F and the vacuum booster 3
A master cylinder pressure P _{M / C} is generated according to the resultant force with the assist force Fa at which 00 is generated.

A reservoir tank 308 is provided above the master cylinder 300. Reservoir tank 308
, A first reservoir passage 400 and a second reservoir passage 402 communicate with each other. In the first reservoir passage 400, a first reservoir cut solenoid 404 (hereinafter, SR
C _- 1404). Similarly, a second reservoir cut solenoid 4 is provided in the second reservoir passage 402.
06 (hereinafter, referred to as SRC- ₂ 406).

The SRC _-1 404 is further connected to a first pump passage 408. Similarly, a second pump passage 410 communicates with SRC- ₂ 406. SRC- ₁₄
The first reservoir passage 40 is turned off.
0 is a two-position solenoid valve that shuts off the first pump passage 408 and turns on when turned on. The SRC- ₂ 406 is a two-position solenoid valve that shuts off the second reservoir passage 402 and the second pump passage 410 when turned off and conducts them when turned on. is there.

First hydraulic chamber 30 of master cylinder 302
A first hydraulic passage 322 and a second hydraulic passage 324 communicate with the fourth hydraulic chamber 306 and the second hydraulic chamber 306, respectively. A first master cut solenoid 412 (hereinafter referred to as SMC- ₁ 412) communicates with the first hydraulic passage 322. On the other hand, a second master cut solenoid 414 (hereinafter, referred to as SMC- ₂ 414) communicates with the second hydraulic passage 324.

The SMC- ₁ 412 has a first pump passage 41
6 and a hydraulic passage 418 provided corresponding to the left rear wheel RL. A first pump solenoid 420 (hereinafter, referred to as SMV- ₁ 420) communicates with the first pump passage 416. The SMV- ₁ 420 also has a right front wheel FR
Are connected to each other.
Inside the SMV _-1 420, a constant pressure release valve 424 is provided. The SMV _-1 420 makes the first pump passage 416 and the hydraulic passage 422 conductive when turned off, and connects them via the constant pressure release valve 424 when turned on 2 Position solenoid valve. First
Between the pump passage 416 and the hydraulic passage 422,
A check valve 426 that allows only fluid flow from the first pump passage 416 to the hydraulic passage 422 is provided.

The SMC- ₂ 414 has a second pump passage 42
8 communicates with a hydraulic passage 430 provided corresponding to the right rear wheel RR. A second pump solenoid 432 (hereinafter, referred to as SMV- ₂ 432) communicates with the second pump passage 428. The SMV _- 2432 also has a left front wheel FL
Are connected to each other.
Inside the SMV- ₂ 432, a constant pressure release valve 436 is provided. The SMV- ₂ 432 makes the second pump passage 428 and the hydraulic passage 434 conductive when turned off, and connects them via a constant pressure release valve 436 when turned on. Position solenoid valve. First
Between the pump passage 428 and the hydraulic passage 434,
A check valve 438 that allows only fluid flow from the second pump passage 428 toward the hydraulic passage 436 is provided.

Inside the SMC- ₁ 412 and SMC- ₂ 414, constant pressure release valves 440 and 442 are provided, respectively. The SMC _-1 412 connects the first hydraulic passage 322 and the hydraulic passage 418 (and the first pump passage 416) to a conductive state when turned off, and a constant pressure release valve when turned on. A two-position solenoid valve that connects them through 440. Also, when the SMC- ₂ 414 is turned off, the second hydraulic passage 324 and the hydraulic passage 43
0 (and the second pump passage 428),
Further, it is a two-position solenoid valve that connects them via a constant pressure release valve 442 when turned on.

A check valve 444 is provided between the first hydraulic passage 322 and the hydraulic passage 418 to allow only the flow of fluid from the first hydraulic passage 322 to the hydraulic passage 418. ing. Similarly, a check valve 44 between the second hydraulic passage 324 and the hydraulic passage 430 that allows only the flow of the fluid from the second hydraulic passage 324 to the hydraulic passage 430.
6 are provided.

Four hydraulic passages 416, 422, 428, and 434 provided corresponding to the left and right front wheels and the left and right rear wheels have holding solenoids S * as in the first and second embodiments. * H, the pressure reducing solenoid S ** R, the wheel cylinders 120 to 126, and the check valves 128 to 134 are in communication. The pressure reducing solenoids SFRR112 and SRLR118 of the right front wheel FR and the left rear wheel RL include:
The first pressure reduction passage 448 communicates with the first pressure reduction passage 448. Furthermore, the left front wheel FL
The second pressure reducing passage 450 communicates with the pressure reducing solenoids SFLR114 and SRRR116 of the right rear wheel RR.

First pressure reducing passage 448 and second pressure reducing passage 4
A first reservoir 452 and a second reservoir 454 communicate with 50. Also, the first reservoir 452
And the second reservoir 454 are each provided with a check valve 456,
It communicates with the suction side of the first pump 460 and the suction side of the second pump 462 via 458. First pump 4
60 and the discharge side of the second pump 462,
It communicates with dampers 464 and 466 for absorbing the pulsation of the discharge pressure. The dampers 464 and 466 communicate with the hydraulic passages 422 and 434, respectively.

Near each wheel, a wheel speed sensor 136,
138, 140, 142 are provided. ECU10
Detects the rotational speed V _W of each wheel based on the output signal of the wheel speed sensors 136-142. Further, a hydraulic pressure sensor 144 is provided in the second hydraulic pressure passage 324 communicating with the master cylinder 302. The ECU 10 detects the master cylinder pressure PM _{/ C} based on the output signal of the hydraulic pressure sensor 144.

Next, the operation of the braking force control device of this embodiment will be described. The braking force control device according to the present embodiment switches the state of various solenoid valves provided in the hydraulic circuit to provide a normal brake function, an ABS function, and a B function.
A function is realized. The normal braking function is realized by turning off all the solenoid valves provided in the braking force control device as shown in FIG. Hereinafter, the state shown in FIG. 15 is referred to as a normal brake state. Further, control for realizing the normal brake function in the braking force control device is referred to as normal brake control.

In the normal braking state shown in FIG.
Both the wheel cylinder 120 of the right front wheel FR and the wheel cylinder 126 of the left rear wheel RL communicate with the first hydraulic chamber 304 of the master cylinder 302 via the first hydraulic pressure passage 322. The wheel cylinder 122 of the left front wheel FL and the wheel cylinder 124 of the right rear wheel RR both communicate with the second hydraulic chamber 306 of the master cylinder 302 via the second hydraulic passage 324. In this case, the wheel cylinder 12
The wheel cylinder pressure P _{W / C} of 0 to 126 is always controlled to be equal to the master cylinder pressure P _{M / C.} Therefore, according to the state shown in FIG. 15, the normal braking function is realized.

In the ABS function, in the state shown in FIG. 15, the first pump 460 and the second pump 462 are turned on, and the holding solenoid S ** H and the pressure reducing solenoid S ** R are switched according to the ABS request. This is realized by appropriate driving. Hereinafter, control for realizing the ABS function in the braking force control device is referred to as ABS control.

During the execution of the ABS control, four hydraulic passages 418, 4 provided corresponding to the left and right front wheels and the left and right rear wheels, respectively.
A high master cylinder pressure P _{M / C} is led to all of 22, 22, 434. Therefore, when the holding solenoid S ** H is opened and the pressure reducing solenoid S ** R is closed in such a situation, the wheel cylinder pressure P _{W / C} of each wheel can be increased. Hereinafter, this state
(i) This is referred to as pressure increase mode.

When both the holding solenoid S ** H and the pressure reducing solenoid S ** R are closed during the execution of the ABS control, the wheel cylinder pressure P _{W / C} of each wheel can be held. . Hereinafter, this state is referred to as (ii) holding mode. Further, during the execution of the ABS control, the holding solenoid S ** H is closed, and the pressure reducing solenoid S ** is closed.
When R is in the valve open state, the wheel cylinder pressure P of each wheel
_{W / C} can be reduced. Hereinafter, this state is referred to as (iii)
This is called a decompression mode.

During the execution of the ABS control, the ECU 10 appropriately sets (i) the pressure increasing mode, (ii) the holding mode,
And (iii) controlling the holding solenoid S ** H and the pressure reducing solenoid S ** R according to the slip state of each wheel so that the pressure reducing mode is realized. Holding solenoid S
When ** H and the pressure reducing solenoid S ** R are controlled as described above, the wheel cylinder pressures P _{W / C of} all the wheels are controlled to appropriate pressures without generating an excessive slip ratio on the corresponding wheels. Is done. As described above, according to the above control, the ABS function can be realized in the braking force control device.

When the decompression mode is performed on each wheel during the execution of the ABS control, the brake fluid in the wheel cylinders 120 to 126 flows through the first decompression passage 448 and the second decompression passage 450 to the first reservoir 452. And flows into the second reservoir 454. The brake fluid flowing into the first reservoir 452 and the second reservoir 454
The water is pumped by the pump 460 and the second pump 462 and supplied to the hydraulic passages 422 and 434.

A part of the brake fluid supplied to the hydraulic passages 422 and 434 flows into the wheel cylinders 120 to 126 when the pressure increase mode is performed in each wheel. Also,
The remainder of the brake fluid flows into master cylinder 302 to supplement the outflow of the brake fluid. Therefore, according to the system of the present embodiment, an excessive stroke does not occur on the brake pedal 12 during execution of the ABS control.

FIG. 16 shows a state of the braking force control device for realizing the BA function. That is, the BA function
As shown in FIG. 16, SRC- ₁ 404, SRC- ₂ 406
(Reservoir cut solenoid) and SMC _- 141
2, the SMC _-2 414 (master cut solenoid) is turned on, and the first pump 460 and the second pump 4
This is realized by turning ON the switch 62. Hereinafter, FIG.
Is referred to as a BA operation state. The control for realizing the BA function in the braking force control device is referred to as BA control.

The ECU 10 executes the routine shown in FIGS. 8 and 9 to determine whether or not the driver has performed an emergency braking operation. Also, EC
In U10, after the emergency brake operation is detected,
In accordance with the routine shown in FIG. 0, in order to increase the wheel cylinder pressure P _{W / C} , there is a state where it is more advantageous to use the first pump 460 and the second pump 462 as the hydraulic pressure source than to use the master cylinder 302 as the hydraulic pressure source. At the time of the formation, the braking force control device is brought into the BA operation state.

When the braking force control device is set to the BA operation state, the brake fluid stored in the reservoir tank 308 is pumped up by the first pump 460 and the second pump 462 and supplied to the hydraulic passages 422 and 434. . B
In the A operating state, the hydraulic passages 422 and 434 are maintained in a conductive state with the first pump passage 416 and the second pump passage 428, respectively.

Further, in the BA operation state, the first pump passage 416 is maintained until the internal pressure of the first pump passage 416 exceeds the opening pressure of the constant pressure release valve 440 and becomes higher than the master cylinder pressure PM _{/ C.} The flow of fluid from the 416 side to the master cylinder 302 side is blocked by the SMC- ₁ 412.
Similarly, in the BA operating state, the second pump passage 428 is maintained until the internal pressure of the second pump passage 428 exceeds the valve opening pressure of the constant pressure release valve 442 and becomes higher than the master cylinder pressure PM _{/ C.}
The flow of fluid from the 28 side to the master cylinder 302 side is blocked by the SMC- ₂ 414.

For this reason, when the BA control is started, the four hydraulic passages 41 provided corresponding to the respective wheels are thereafter provided.
8, 422, 428, and 430 have the master cylinder pressure P
High hydraulic pressure is generated compared to _{M / C.} In the BA operating state, the wheel cylinders 120 to 126 and the corresponding hydraulic passages 418, 422, 428, 430 are maintained in a conductive state. Therefore, when the BA control is started, thereafter, the wheel cylinder pressures P _{W / C} of all the wheels are reduced by the first pump 460.
Alternatively, the pressure is quickly increased to a pressure exceeding the master cylinder pressure P _{M / C} using the second pump 462 as a hydraulic pressure source. As described above, according to the state illustrated in FIG. 16, the function of quickly increasing the braking force, that is, the BA function can be realized.

In the BA operating state shown in FIG. 16, the hydraulic passages 418, 422, 428, and 430 communicate with the master cylinder 302 via check valves 444, 446. Therefore, when the master cylinder pressure P _{M / C} is larger than the wheel cylinder pressure P _{W / C} of each wheel, B
Even in the A operating state, the wheel cylinder pressure P _{W / C} can be increased using the master cylinder 302 as a hydraulic pressure source.

When the BA control is started in the braking force control device, thereafter, the wheel cylinder pressure P _{W / C of} each wheel is rapidly increased, so that an excessive slip ratio may occur in any one of the wheels. is there. In such a case, the ECU 10 starts the BA + ABS control. BA
The + ABS control is one of the SRC _-1 404 and SRC _-2 406 that are turned on when the BA control is started.
The solenoid corresponding to the wheel where the excessive slip ratio has occurred is turned off, and the solenoid corresponding to the wheel where the excessive slip ratio has occurred among the holding solenoid S ** H and the pressure-reducing solenoid is requested according to the ABS request. This is realized by appropriate control.

FIG. 17 shows a state of the braking force control device for executing the BA + ABS control in which the left rear wheel RL is a target wheel for ABS control and the other wheels are non-control target wheels for ABS control. The state shown in FIG. 17 is realized when an excessive slip ratio occurs in the left rear wheel RL prior to the other wheels after the BA control is started. Hereinafter, the state shown in FIG. 17 is referred to as a BA + ABS (RL) operation state. Control realized by bringing the braking force control device into the BA + ABS (RL) operating state is referred to as BA + ABS (RL) control.

The BA + ABS (RL) operation state is the BA system.
SRC that was turned on by the start of control
_-1404 (first reservoir cut solenoid) turned off
And SRLH110 and SRLR118 are A
It is realized by appropriately controlling according to the request of BS.
You. More specifically, BA + ABS (RL) operating state
Is the SRC_-2406, SMC _-1412 and SMC_-24
14 is turned on, the first pump 460 and the second pump
462 is turned on and the left rear wheel RL is
(I) Boost mode, (ii) Hold mode, and (iii) Decrease mode.
The slip mode of the left rear wheel RL is set so that the pressure mode is realized.
Controls SRLH110 and SRLR118 according to state
It is realized by doing.

In the BA + ABS (RL) operating state,
The second pump 462 controls the reservoir
Brake fluid sucked from the nozzle
To 34. Pumped by the second pump 462
The brake fluid is the wheel cylinder 12 of the left front wheel FL.
2 and the wheel cylinder 124 of the right rear wheel RR.
You. According to the above control, the left front wheel FL and the right rear wheel RR
Wheel cylinder pressure P _{W / C}Is boosted as in BA control
Keep doing.

In the BA + ABS (FL) operating state,
The first pump 460 is connected to the wheel cylinder 12 of the left rear wheel RL.
After flowing out of the reservoir 6, the brake fluid flowing into the first reservoir 452 is pressure-fed to the hydraulic passage 422. The brake fluid pumped by the first pump 360 is mainly supplied to the wheel cylinder 120, and is supplied to the left rear wheel RL.
(i) When the pressure increase mode is executed, the wheel cylinder 126
Supplied to According to the above control, the wheel cylinder pressure P _{W / C} of the right front wheel FR continues to increase as in the BA control. Further, the wheel cylinder pressure P _{W / C} of the left rear wheel RL is controlled to an appropriate value that does not generate an excessive slip ratio on the left rear wheel RL.

As described above, according to the BA + ABS (RL) operating state, the wheel cylinder pressure P _{W / C} of the left rear wheel RL, which is the target wheel of the ABS control, does not generate an excessive slip ratio on the left rear wheel RL. The wheel cylinder pressures P _{W / C} of the left and right front wheels FL, FR and the right rear wheel RR, which are the non-target wheels of the ABS control, can be quickly increased while suppressing the pressure to an appropriate pressure, as in the BA control. Further, according to the braking force control device of the present embodiment, the wheels other than the left rear wheel RL are ABS
Even in the case of the control target wheel, the BA function and the ABS function can be realized at the same time as in the case described above.

In the braking force control device of this embodiment, EC
U10 starts BA control in the same manner as in the first and second embodiments as described above. For this reason,
According to the braking force control device of the present embodiment, similarly to the above-described braking force control device of the first embodiment or the second embodiment, the emergency braking operation of the driver is accurately detected, and thereafter, the control is quickly performed. Power can be started.

[0182]

As described above, according to the first aspect of the present invention, after the emergency braking operation is performed, it is more effective to execute the brake assist control than to execute the normal control. The brake assist control can be started at the point in time when it is advantageous to achieve this. Therefore, according to the present invention, when an emergency brake operation is performed, regardless of whether the brake operation is an additional brake operation,
The wheel cylinder pressure can always be rapidly increased.

According to the second aspect of the present invention, the brake assist control can be started at a more appropriate timing for increasing the wheel cylinder pressure. Therefore, according to the present invention, when an emergency braking operation is performed, the wheel cylinder pressure can be appropriately increased according to various situations.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a normal braking state of a braking force control device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a hydro booster used in the braking force control device shown in FIG.

FIG. 3 is a diagram illustrating an ABS operation state of the braking force control device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a BA operating state and a BA + ABS operating state of the braking force control device according to the first embodiment of the present invention.

[5] FIG. 5 (A) occurs on a change rate [Delta] P M _{/ C} of the master cylinder pressure P _{M / C} when an emergency brake operation is performed in the brake force control apparatus corresponding to the first embodiment of the present invention It is a figure showing a change. FIG. 5B shows changes occurring in the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C} when an emergency braking operation is performed in the braking force control device according to the first embodiment of the present invention. FIG.

FIG. 6 shows changes occurring in the master cylinder pressure P _{M / C} and the wheel cylinder pressure P _{W / C} when the emergency braking operation is performed by increasing the number of steps in the braking force control device according to the first embodiment of the present invention. FIG. 7 is a diagram illustrating a case where a normal emergency brake operation is performed.

FIG. 7 is a diagram showing a relationship between a total brake fluid amount Q _total supplied to a wheel cylinder and a wheel cylinder pressure P _{W / C.}

FIG. 8 is a flowchart of an example of a control routine executed to determine whether a first standby state is established in the braking force control device according to the first embodiment of the present invention.

FIG. 9 is a flowchart of an example of a control routine executed to determine whether a second standby state is established in the braking force control device according to the first embodiment of the present invention.

FIG. 10 is a flowchart of an example of a control routine that is executed in the braking force control device according to the first embodiment of the present invention to determine whether a BA control start condition is satisfied.

FIG. 11 is a flowchart of an example of a routine executed to perform an estimation calculation of a wheel cylinder pressure P _{W / C} in the braking force control device according to the first embodiment of the present invention.

FIG. 12 is a diagram illustrating a normal braking state of the braking force control device according to the second embodiment of the present invention.

FIG. 13 is a diagram showing a BA operation state of the braking force control device according to the second embodiment of the present invention.

FIG. 14 is a system configuration diagram showing a BA + ABS operating state of the braking force control device according to the second embodiment of the present invention.

FIG. 15 is a diagram showing a normal braking state of the braking force control device according to the third embodiment of the present invention.

FIG. 16 is a diagram illustrating a BA operation state of the braking force control device according to the third embodiment of the present invention.

FIG. 17 is a system configuration diagram showing a BA + ABS operation state of the braking force control device according to the third embodiment of the present invention.

[Explanation of symbols]

 10 Electronic Control Unit (ECU) 12 Brake Pedal 36 Hydro Booster 120, 122, 124, 126 Wheel Cylinder 144 Hydraulic Pressure Sensor 300 Vacuum Booster 302 Master Cylinder

Claims (2)

[Claims] An emergency braking operation is performed in a braking force control device that performs a normal brake control that generates a braking force according to a brake pedaling force and a brake assist control that generates a large braking force as compared with the normal control. Emergency brake operation detecting means for detecting that the brake assist has been performed, and when the differential pressure between the master cylinder pressure and the wheel cylinder pressure becomes equal to or less than a predetermined value after detecting that the emergency brake operation has been performed, And a brake assist control start means for starting control. 2. The braking force control device according to claim 1, further comprising control start differential pressure determining means for determining the predetermined value based on a master cylinder pressure.