Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-06-09
2001-04-17
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C188SDIG001, C188S358000, C303S015000, C303S155000, C303S116100, C303S113100, C303S114100
Reexamination Certificate
active
06217133
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 increases a power ratio of a brake booster 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. Hereinafter, such a brake operation is referred to as an emergency brake operation.
The above-mentioned conventional brake force control apparatus determines that the emergency brake operation is being performed when the brake pedal is operated at a speed which is greater than a predetermined speed. In this case, a relatively high brake pressure as compared to that generated during a normal brake operation is generated by pressurizing brake fluid stored in a reservoir and supplying the pressurized brake fluid to wheel cylinders. Hereinafter, this brake control is referred to as a brake assist control (abbreviated as a BA control).
According to the above-mentioned conventional brake force control apparatus, when the emergency brake operation is performed, an advantageous situation can be established for a rapid increase in the brake force by generating a relatively large power ratio as compared to that generated during a normal brake operation. Thus, when the driver requests a rapid increase in a brake force, it is possible to correctly satisfy the request.
In order to generate a relatively high brake pressure as compared to that generated during the normal brake operation when the emergency brake operation is performed by the driver, it is necessary to provide the brake force control apparatus with a means for pressurizing the brake fluid. A pump can be used as such a means. However, when a pump is used as a high pressure source, the increase in the brake force may be delayed due to a delay in the response of the pump, if the pump is started to be operated after a condition for starting the BA control is established. In this case, it is impossible to generate a brake force which appropriately satisfies the request by the driver.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a brake force control apparatus which can quickly supply pressurized brake fluid to wheel cylinders immediately after a condition for starting the BA control is established by starting the operation of a high pressure source before the BA control is started.
The above-mentioned objects can be achieved by a brake force control apparatus comprising:
emergency brake determining means for determining an emergency brake operation performed by a driver;
a high pressure source for generating a fluid pressure which is higher than a fluid pressure generated by a master cylinder; and
supply means for supplying brake fluid from the pump to a wheel cylinder based on the determination made by the emergency brake determining means, characterized by further comprising:
actuating means for actuating the high pressure source before the fluid pressure is supplied by the supply means.
In this invention, since the brake fluid can be immediately supplied to the wheel cylinder from the high pressure source, the brake force control for the emergency brake operation can be provided so as to be highly responsive. Generally, the high pressure source cannot immediately increase the fluid pressure to a desired high pressure after being started due to inertia. Thus, if the operation of the pump is started at a time when the brake force control for the emergency brake operation is started, a delay is generated until the brake fluid is actually supplied to the wheel cylinder, and as a result, the response of the brake force control may be deteriorated.
However, according to the present invention, the high pressure source starts to pressurize the brake fluid before the supply means supplies the fluid pressure. Thus, at a time when the pressurized brake fluid is supplied to the wheel cylinder, the high pressure source has been already started and the pressure of the brake fluid is increased to a predetermined value. Accordingly, it is possible to immediately supply the pressurized brake fluid to the wheel cylinder.
Additionally, the emergency brake determining means may comprise:
necessary condition determining means for determining an establishment of a necessary condition for the emergency brake operation; and
sufficient condition determining means for determining an establishment of a sufficient condition for the emergency brake operation,
wherein
the actuating means actuates the high pressure source when the necessary condition is established.
The necessary condition may be established when a brake operating speed is greater than or equal to a first predetermined speed.
Additionally, the sufficient condition may be established when a high-speed operating time after the brake operating speed becomes greater than or equal to the first predetermined speed until the brake operating speed becomes smaller than or equal to a second predetermined speed is greater than or equal to a first predetermined time.
In this invention, the brake fluid is supplied from the high pressure source to the wheel cylinder only when an elapsed time after the brake operating speed becomes greater than or equal to the first predetermined speed until the brake operating speed becomes smaller than or equal to the second predetermined speed, that is, a time for which the brake operation is maintained to be performed at a high speed is greater than the first predetermined time. When a driver of a vehicle requests a rapid increase in the brake force, the high-speed operating time is relatively long. In such a case, the supply means positively supplies the brake fluid from the high pressure source to the wheel cylinder. On the other hand, when the emergency brake operation is instantaneously performed due to a vibration of the vehicle, the high-speed operating time is relatively short. In such a case, the supply means does not unnecessarily supplies the brake fluid from the high pressure source to the wheel cylinder. Accordingly, it is possible to generate the increased fluid pressure only when the driver requests a rapid increase in the brake force without being subjected to the influence of the instantaneous brake operation due to a vibration of the vehicle.
Additionally, the high-speed operating time may be started to be counted when the brake operating speed exceeds the first predetermined speed and the amount of brake operation exceeds a first amount of operation.
In this invention, the high-speed operating time is started to be counted after a brake operation with a high operating speed and the amount of brake operation is large. Both of the above-mentioned two conditions for starting to count the high-speed operating time are established when the driver requests a rapid increase in the brake force. Thus, the driver's request can be accurately detected by providing these two conditions. Accordingly, it is possible to accurately detect a situation in which the driver requests a rapid increase in the brake force.
Additionally, the supply means may supply the brake fluid from the high pressure source to the wheel cylinder when the high-speed operating time is greater than or equal to the first predetermined time and smaller than or equal to a second predetermined time.
In this invention, the brake fluid is supplied from the high pressure source to the wheel cylinder when the high-speed operating time is greater than or equal to the first predetermined time and smaller than or equal to a second predetermined time. When a brake operation is properly performed by the driver, a high operating speed is not maintained for an excessively long time. On the oth
Butler Douglas C.
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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