Fluid-pressure and analogous brake systems – Speed-controlled – Braking pressure demand or braking force desire
Reexamination Certificate
1998-10-29
2001-03-13
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Braking pressure demand or braking force desire
C303S116200, C303S146000, C303S900000
Reexamination Certificate
active
06199963
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a braking force control apparatus, and more particularly to a braking force control apparatus in which a master cylinder and a high pressure source are provided as a hydraulic source.
BACKGROUND OF THE INVENTION
Conventionally, a braking force control apparatus in which a braking force greater than that in a normal case is generated when an emergency braking operation is required has been known, as disclosed in Japanese Laid-Open Patent Application No. 4-121260. The conventional apparatus has a brake booster generating a pressure into which a brake pedaling force F
p
is boosted with a predetermined servo ratio. The pressure from the brake booster is transferred to the master cylinder. The master cylinder then generates a master cylinder pressure P
M/C
corresponding to the pressure generated by the brake booster, that is, corresponding to the brake pedaling force F
p
.
In addition, the conventional apparatus has a hydraulic pressure generating mechanism, including a pump as a hydraulic pressure source, generating an assist hydraulic pressure. The hydraulic pressure generating mechanism generates the assist hydraulic pressure based on a driving signal supplied from a control circuit. When the brake pedal is operated at a speed greater than a predetermined speed, the control circuit determines that a driver carries out the emergency braking operation and outputs the driving signal for requesting a maximum assist hydraulic pressure to the hydraulic pressure generating mechanism. The assist hydraulic pressure generated by the hydraulic pressure generating mechanism is supplied to the master cylinder and a change valve. Due to switching operation of the change valve, a higher one of the assist hydraulic pressure generated by the hydraulic pressure generating mechanism and the master cylinder pressure P
M/C
is alternatively supplied to wheel cylinders.
According to the above conventional apparatus, when the brake pedal is operated at a speed equal to or less the predetermined speed, the master cylinder pressure P
M/C
which is controlled to a hydraulic pressure corresponding to the brake pedaling pressure F
P
is supplied to the wheel cylinders. Hereinafter, a control in such a state is referred to as a normal control. In addition, when the brake pedal is operated at a speed greater than the predetermined speed, a high assist hydraulic pressure from the pump which is the hydraulic pressure source is supplied to the wheel cylinders. Hereinafter, a control in such a state is referred to as a brake assist control. Thus, according to the above conventional apparatus, the braking force is controlled based on the bake pedaling force F
P
. Further, after the emergency braking operation is detected, the braking force can be rapidly increased.
In the above conventional apparatus, to terminate the brake assist control and resume the normal control, it is necessary to switch the change valve so that the hydraulic pressure source for the wheel cylinders is changed from the hydraulic pressure generating mechanism to the master cylinder. The brake assist control is a control for generating a wheel cylinder pressure P
W/C
sufficiently greater than the master cylinder pressure P
M/C
when the emergency braking operation is carried out. Thus, when the terminating request of the brake assist control occurs, there may be a great difference between the wheel cylinder pressure P
W/C
and the master cylinder pressure P
M/C.
In a case where the wheel cylinder pressure P
W/C
greater than the master cylinder pressure P
M/C
is generated in the wheel cylinders, when the hydraulic pressure source for the wheel cylinders is switched from the hydraulic pressure generating mechanism to the master cylinder, a brake fluid having a high pressure flows backward from the wheel cylinders to the master cylinder. The brake fluid flowing back to the master cylinder passes through the master cylinder and enters a reservoir tank. This phenomenon is not preferable in that unnecessary load is applied to the master cylinder and the pressure in wheel cylinders is prevented from being rapidly decreased.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above point, and an object of the present invention is to provide a braking force control apparatus which can terminate the brake assist control without causing the brake fluid stored in the wheel cylinders at a high pressure during the brake assist control to flow back to the master cylinder.
The above object of the present invention is achieved by a braking force control apparatus which executes a normal control and a brake assist control, said normal control using a master cylinder as a hydraulic source to increasing a wheel cylinder pressure, said brake assist control using a high pressure source as the hydraulic source to increasing the wheel cylinder pressure in a state in which communication between said master cylinder and said wheel cylinder is intercepted, characterized in that there is provided: termination means for restoring the communication between said master cylinder and said wheel cylinder after wheel cylinder pressure is decreased so as to terminate said brake assist control when a termination request for said brake assist control occurs.
In the above constitution, while the normal control is being executing, the wheel cylinder communicates with the master cylinder. In addition, while the brake assist control is being executing, the communication between the wheel cylinder and the master cylinder is intercepted and the wheel cylinder is joined to the high pressure source. In the brake assist control, the high pressure source is used as the hydraulic source to increase the wheel cylinder pressure. As a result, in the brake assist control, there is a case where a pressure greater than the master cylinder is generated in the wheel cylinder. The termination control means decreases the wheel cylinder before the brake assist control is terminated. Thus, when the brake assist control is terminated and the wheel cylinder communicates with the master cylinder, a brake fluid having a high pressure does not flow back from the wheel cylinder to the master cylinder.
In the above constitution, the present invention may be formed as follows. That is, the braking force control apparatus executes a stability control using said high pressure source as said hydraulic source, in a state in which the communication between said wheel cylinder for a controlled-wheel and said master cylinder, to increase a wheel cylinder pressure for the controlled-wheel so that a yaw moment is generated to stabilize an action of the vehicle, the controlled-wheel being a wheel which should be controlled, and said termination control means comprises termination specifying control means for restoring the communication between said wheel cylinder for a not-controlled wheel in said stability control and said master cylinder after the wheel cylinder pressure for the not-controlled wheel is decreased so as to discontinue said brake assist control when a request for said stabilizing control occurs during execution of said brake assist control, said not-controlled wheel being a wheel which should not be controlled in said brake assist control.
In this constitution, while the stability control is being executed, the high pressure source is used as the hydraulic source to increase the wheel cylinder pressure for the controlled-wheel. AT this time, a not-controlled wheel communicates with the master cylinder in the same way as in the normal control. When the brake assist control is switched to the stability control (the stability control has a preference to the brake assist control), it is necessary to switch the hydraulic source for the not-controlled wheel from the high pressure source to the master cylinder. The termination specifying control means decreases the wheel cylinder pressure for the not-controlled wheel before switching the hydraulic source. Thus, when the brake assist control is switched to the stability contro
Kenyon & Kenyon
Kramer Devon
Schwartz Christopher P.
Toyota Jidosha & Kabushiki Kaisha
LandOfFree
Braking force control apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Braking force control apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Braking force control apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2544766