Fluid-pressure and analogous brake systems – Speed-controlled – Braking pressure demand or braking force desire
Reexamination Certificate
1999-10-19
2001-11-13
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Braking pressure demand or braking force desire
C303S011000, C303S113400, C303S115400, C303S166000
Reexamination Certificate
active
06315371
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a technical field of a brake system in which a master cylinder (hereinafter, sometimes referred to as “MCY”) is operated by a press of a brake pedal to develop fluid pressure (hereinafter, sometimes referred to as “MCY pressure”) which actuates a brake cylinder, performing braking operation and, more particularly, to a technical field of a brake system which is designed to have a very short stroke of a brake pedal as compared to a conventional one and has suitable braking characteristics.
Among brake systems for automobiles, a brake system in which the braking action is carried out by fluid pressure converted from a pedaling force exerted on a brake pedal is well employed.
FIG. 9
is a schematic view of the basic construction of such a conventional brake system using fluid pressure. In
FIG. 9
, numeral “a” designates a brake system, “b” designates a brake pedal for braking operation, “c” designates a tandem-type master cylinder (MCY) for generating brake fluid pressure, “d” designates a primary piston of the MCY c, “e” designates a secondary piston of the MCY c, “f” and “g” designate return springs, “h” designates a primary fluid pressure chamber of a first brake circuit, “i” designates a secondary fluid pressure chamber of a second brake circuit, “j” designates a reservoir for storing brake fluid, “k” designates a primary-side fluid line for the brake fluid between the primary fluid pressure chamber f and the reservoir j, “m” designates a secondary-side fluid line for the brake fluid between the secondary fluid pressure chamber i and the reservoir j, “n” designates a brake fluid pressure line in the first brake circuit, “o” designates a brake fluid pressure line in the second brake circuit, “p” and “q” designate wheel cylinders (hereinafter, sometimes referred to as “WCY”) in the first brake circuit, and “r” and “s” designate WCYs in the second brake circuit.
As shown in
FIG. 9
, in this brake system a, the primary piston d of the MCY c is advanced (to the left in
FIG. 9
) from the illustrated inoperative position by a pedaling force exerted on the brake pedal b. As a sealing portion (not shown) of the primary piston d passes an opening k
1
(for communication with the primary fluid pressure chamber h of the MCY c) of the primary-side fluid line k and further advances, MCY pressure is developed in the primary fluid pressure chamber h. By this MCY pressure, the secondary piston e advances so that a sealing portion (not shown) of the secondary piston e passes an opening m
1
of the secondary fluid line m and further advances, MCY pressure is developed in the secondary fluid pressure chamber i. These MCY pressure is introduced into the WCYs p, q and r, s through the brake fluid pressure lines n and o, respectively, thereby carrying out the braking action.
In this brake system a, as mentioned above, the pedaling force exerted on the brake pedal b is converted to the fluid pressure by the MCY c and the WCYs p, q and r, s are actuated by the fluid pressures, thus carrying out the braking action.
As for brake systems, recently, it is desired to design the stroke of a brake pedal as shorter as possible in a view of the facility of the braking operation.
In the aforementioned brake system, however, a predetermined amount of brake fluid must be sent from the MCY c to the brake circuits until fluid pressures are developed after the sealing portions of the pistons d, e pass the openings k
1
, m
1
of the respective fluid lines communicating with the reservoir j, due to the idle distances of the WCYs p, q and r, s, and so on. Accordingly, the pistons d, e must advance largely in order to send the predetermined amount of brake fluid. Since this action does not directly actually develop the fluid pressures, this action is idle travel. The stroke of each piston d, e includes the travel from the inoperative position to a position where the sealing portion passes the openings k
1
, m
1
of the fluid lines k, m communicating with the reservoir j and the idle travel, i.e. a large stroke. As a result of this, the pedal stroke of the brake pedal d is inevitably large. Concretely, the pedal stroke of the conventional brake pedal is generally in a range from 60 mm to 80 mm, even the shortest one is about 40 mm.
The above mentioned desire for designing the stroke of a brake pedal as short as possible can not be sufficiently fulfilled by the conventional brake system.
Brake characteristics of a vehicle including (i) feeling of braking, (ii) feeling of response, and (iii) feeling of pedaling are determined by three factors: (1) pedal characteristics, (2) travel of a brake pedal, and (3) deceleration (brake fluid pressure) of the vehicle. When the shortening of the pedal stroke is enabled, it is desired to optimize the brake characteristics by taking these three factors into consideration.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a brake system which can be set to have a very short stroke of a brake pedal as compared to a conventional one and has optimal braking characteristics.
For accomplishing this object, a brake system of the present invention comprises: a brake pedal which travels by pedaling force applied to the brake pedal, a reservoir for storing brake fluid, a master cylinder which communicates with the reservoir when it is inoperative and is shut off from the reservoir so as to develop fluid pressure when it is actuated by the press of said brake pedal, and brake cylinders which are connected to said master cylinder and are actuated by the fluid pressure of the master cylinder, wherein said pedaling force is converted to the fluid pressure by said master cylinder and said brake cylinders are actuated by the fluid pressure, and said brake system further comprises: shut-off means for shutting off the communication between said master cylinder and said brake cylinders, brake fluid supply means for supplying the brake fluid to lines between said brake cylinders and said shut-off means, brake fluid pressure control means for controlling the supply of the brake fluid from brake fluid supply means to said lines and for controlling the fluid pressure in said brake cylinders, and a central processor for controlling said shut-off means based on the operation of said brake pedal in such a manner that said shut-off means allows the communication between said brake cylinders and said reservoir when the brake pedal is inoperative and shuts off the communication between said brake cylinders and said reservoir when said brake pedal is operative and, in addition, for controlling said brake fluid pressure control means based on the pedaling force in such a manner that said brake fluid pressure control means stops the supply of the brake fluid from said brake fluid supply means to said lines when said brake pedal is inoperative and allows the supply of the brake fluid from said brake fluid supply means to said lines and adjusts the fluid pressure in said brake cylinders according to the predetermined relation between said pedaling force and the outputs of said brake cylinders when said brake pedal is operative. In this brake system, the central processor controls said shut-off means and said fluid pressure control means to obtain rising characteristics of braking action having a characteristic point with a deceleration of a vehicle 0.08-0.12G when the pedaling force is 15-25N and the travel of the brake pedal is 7-15 mm.
According to the present invention, the characteristics between the pedaling force and the deceleration of the vehicle are provided with a jumping function to develop a predetermined deceleration when the travel of the brake pedal reaches the rising point of the deceleration of the vehicle.
In addition, according to the present invention, the characteristics between the pedaling force and the deceleration of the vehicle after said characteristic point are provided with linear characteristics.
In addition, according to the present invention, the brake system has brake characteristics of preventi
Fukushima Toshiaki
Wachi Yuzi
Bosch Braking Systems Co. Ltd.
Kanesaka & Takeuchi
Pezzlo Benjamin A.
Schwartz Christopher P.
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