Fluid-pressure and analogous brake systems – Speed-controlled – Braking pressure demand or braking force desire
Reexamination Certificate
1999-06-24
2001-11-06
Oberleitner, Robert J (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Braking pressure demand or braking force desire
C303S116100
Reexamination Certificate
active
06312064
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a brake force control apparatus and, more particularly, to a brake force control apparatus which generates, when an emergency brake operation is performed in a vehicle, a relatively large brake force as compared to that generated during a normal brake operation.
BACKGROUND ART
Conventionally, as disclosed in Japanese Laid-Open Patent Application No. 4-121260, a brake force control apparatus is known which generates an increased brake fluid pressure as compared to that generated during a normal brake operation when a brake pedal is depressed at a speed exceeding a predetermined speed. A driver of a vehicle operates a brake pedal at a high speed when a rapid increase in a brake force is desired. According to the above-mentioned brake force control apparatus, when such a brake operation (hereinafter referred to as an emergency brake operation) is performed, it is possible to generate a brake force which appropriately responds to a request of the driver by generating an increased brake fluid pressure as compared to that generated during the normal brake operation.
A brake force requested by the driver after start of the emergency brake operation is not always uniform. That is, when the brake pedal is further depressed after the start of the emergency brake operation, it can be determined that the driver intends to increase the brake force. On the other hand, when an operation of the brake pedal is maintained constant or decreased, it can be determined that the driver intends to maintain or decrease the brake force, respectively.
Accordingly, in order to generate a brake force to which the driver's intention is accurately reflected after the emergency brake operation is started, it is appropriate to increase or decrease the brake fluid pressure in accordance with a state of operation of the brake pedal after the brake fluid pressure is increased as compared to that generated in the normal operation. Such an ability can be achieved by, for example, providing an additional function which attempts to increase the brake fluid pressure when the amount of operation of the brake pedal is increased, maintain the brake fluid pressure when the amount of operation is maintained, and decrease the brake fluid pressure when the amount of operation is decreased.
However, it is not necessarily easy to increase or decrease the brake fluid pressure supplied to wheel cylinders when the brake fluid pressure is relatively high as compared to a case of a normal operation. For this reason, the brake fluid pressure intended by the driver may not be generated if the brake fluid pressure is controlled by using the above-mentioned technique.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a brake force control apparatus which can always accurately generate a brake force conforming to a driver's intention.
The above-mentioned object can be achieved by a brake force control apparatus which performs brake assist control for supplying an increased brake fluid pressure which is greater than that generated in a regular brake operation to a wheel cylinder of a vehicle when an emergency brake operation is performed by a driver, the brake force control apparatus characterized by:
deceleration detecting means for detecting a deceleration of the vehicle;
difference detecting means for detecting a difference between a target deceleration which is to be generated during execution of the brake assist control and the deceleration; and
fluid pressure control means for controlling a brake fluid pressure which is supplied to the wheel cylinder during execution of the brake assist control based on the difference.
In this invention, during execution of the brake assist control, an increased brake fluid pressure is supplied to the wheel cylinder as compared to that generated during the regular brake operation. This brake fluid pressure is controlled based on the difference between the target deceleration and the actual deceleration. According to this control, a deceleration which is always equal to the target deceleration can be obtained during execution of the brake assist control (hereinafter referred to as BA control) without being influenced by interferences with the other controls and changes in properties of components during execution of the brake assist control.
The brake force control apparatus according to the present invention may further comprise:
amount of brake operation detecting means for detecting an amount of brake operation; and
target deceleration setting means for setting the target deceleration based on the amount of brake operation.
In this invention, the target deceleration is set based on the amount of brake operation performed by the driver. When a relatively large amount of brake operation is generated during execution of the brake assist control, it can be determined that the driver requests a relatively large deceleration. In this case, it is appropriate to set the target deceleration to a relatively large value. On the other hand, when the amount of brake operation generated during execution of the brake assist control is relatively small, it can be determined that the driver does not request a large deceleration. In this case, it is appropriate to set the target deceleration to a relatively small value. According to the invention, it is possible to set the target deceleration to a value which always satisfies the above-mentioned requirements during execution of the brake assist control. Thus, it is possible to set the target deceleration to an appropriate value which conforms to the driver's intention.
Additionally, the target deceleration setting means may comprise:
basic deceleration detecting means for detecting a deceleration which is obtained during the regular brake operation based on the amount of brake operation; and
assist deceleration adding means for calculating the target deceleration by adding a predetermined assist deceleration to the deceleration detected by the basic deceleration detecting means.
In this invention, a deceleration which is substantially equal to the target deceleration can be obtained during execution of the brake assist control. In addition, the target deceleration is set to a value which is obtained by adding the assist deceleration to a deceleration corresponding to the amount of brake operation (a deceleration obtained during the regular brake operation). Accordingly, a deceleration can be generated which is greater than that obtained during the regular brake operation by the predetermined assist deceleration during execution of the brake assist control.
Additionally, the brake force control apparatus may further comprise an TABS mechanism for performing TABS control which attempts to decrease a wheel cylinder pressure P
W/C
for a wheel in which an excessive slip rate is generated, and the fluid pressure control means may comprise pressure increasing inhibiting means for inhibiting increase of the wheel cylinder pressure P
W/C
when the TABS control is performed even if the deceleration is smaller than the target deceleration.
In this invention, when an excessive slip rate is generated in any of the wheels, the wheel cylinder pressure P
W/C
of that wheel is decreased by performing the TABS control. It can be determined that the wheel cylinder pressure P
W/C
of each wheel is increased to a certain extent at a time when the TABS control is started. According to the present invention, in such a situation, the wheel cylinder pressure P
W/C
is inhibited from being increased even if the deceleration of the vehicle is smaller than the target deceleration. According to this process, the wheel cylinder pressure P
W/C
is not increased to an excessively high fluid pressure when the vehicle is moving on a low friction road.
Additionally, the pressure increasing inhibiting means may inhibit increase of the wheel cylinder pressure P
W/C
when the TABS control is performed for at least one of the front left and right wheels.
In this invention, increase of the wheel cylinder pre
Aizawa Hideyuki
Hara Masahiro
Koike Shin
Nakanishi Nobuyasu
Shimizu Satoshi
Kenyon & Kenyon
Oberleitner Robert J
Pezzlo Benjamin A.
Toyota Jidosha & Kabushiki Kaisha
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