Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2000-09-14
2002-10-22
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C060S593000
Reexamination Certificate
active
06467266
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brake booster, which boosts operating force exerted on an operating means with working fluid pressure, that is controlled by a control valve, into predetermined magnitude to output intensified force and, more particularly, to a brake booster which can set the input travel variously without being affected by the operation of a working unit of a master cylinder and the like operated with the output of the brake booster and can control the output of the brake booster during its operation regardless of the operating force exerted on the operating means.
For example, in a conventional brake system of an automobile, a brake booster has been employed which boosts pedaling force exerted on a brake pedal by fluid pressure of hydraulic fluid into predetermined magnitude to develop large brake fluid pressure. The brake booster functions to provide large braking force from small pedaling force exerted on the brake pedal, thereby securing the braking action and reducing the labor of a driver.
Such conventional brake booster can be roughly classified into a vacuum booster for boosting the pedaling force by negative pressure to actuate the master cylinder, a hydraulic booster for boosting the pedaling force by fluid pressure to actuate the master cylinder, a full-power brake system in which the fluid pressure is directly supplied to the wheel cylinders, and a pneumatic/electromagnetic booster for boosting the pedaling force by compressed air/electromagnetic force to actuate the master cylinder.
FIG. 22
is a schematic illustration of a brake system employing a conventional vacuum booster and
FIG. 23
is a schematic illustration of a brake system employing a conventional hydraulic booster.
In the brake system employing the vacuum booster shown in
FIG. 22
, input force Fi is exerted to an input shaft
4
by depression of a brake pedal
3
so that the input shaft
4
moves in the operative direction. Then, a first valve element
5
a
of a control valve
5
moves to the left so that an output port
5
c
of the first valve element
5
a
is shut off from a low-pressure (L) valve passage
5
b
1
of a second valve element
5
b
connected to a negative pressure source and is connected to a high-pressure (H) valve passage
5
b
2
of the second valve element
5
b
connected to the atmospheric air. The atmospheric air is controlled according to the input Fi by the control valve
5
to develop output pressure Pr. The output pressure Pr is supplied to a power chamber
10
c
of the power cylinder
10
so that a power piston
10
b
moves to the left to produce output Fp which is boosted pedaling force. A master piston
11
a
is actuated by the output Fp so that a master cylinder
11
develops master cylinder pressure Pm which is supplied to wheel cylinder
7
as braking fluid pressure Pb, thereby actuating the brake. Reaction force Fm from the master cylinder
11
is modulated as reaction force Fv by a reaction mechanism
8
and is applied to the first valve element
5
a.
Therefore, the output pressure Pr of the control valve
5
is regulated to balance the reaction force Fv with the input force Fi of the input shaft
4
. The reaction force Fv is transmitted to a driver through the input shaft
4
and the brake pedal
3
. In the vacuum booster, the first valve element
5
a
moves together with the input shaft
4
and the second valve element
5
b
moves together with the power piston
10
b.
In the break system employing the hydraulic booster shown in
FIG. 23
, input force Fi is exerted to an input shaft
4
by depression of a brake pedal
3
so that the input shaft
4
moves in the operative direction. Then, a first valve element
5
a
of a control valve
5
moves to the left so that an output port
5
c
of the first valve element
5
a
is shut off from a low-pressure (L) valve passage
5
b
1
of a second valve element
5
b
connected to a reservoir and is connected to a high-pressure (H) valve passage
5
b
2
of the second valve element
5
b
connected to a fluid pressure source. The hydraulic pressure of the fluid pressure source such as a pump and an accumulator is controlled according to the input Fi by the control valve
5
to develop output pressure Pr. The output pressure Pr is supplied to a power chamber
10
c
of the power cylinder
10
so that a power piston
10
b
moves to the left to produce output Fp which is boosted pedaling force. A master piston
11
a
is actuated by the output Fp so that a master cylinder
11
develops master cylinder pressure Pm which is supplied to wheel cylinder
7
as braking fluid pressure Pb, thereby actuating the brake. Reaction force Fm from the master cylinder
11
and reaction force by the output pressure Pr of the control valve
5
are modulated as reaction force Fv by a reaction receiving portion and is applied to the first valve element
5
a.
Therefore, the output pressure Pr of the control valve
5
is regulated to balance the reaction force Fv with the input force Fi of the input shaft
4
. The reaction force Fv is transmitted to a driver through the input shaft
4
and the brake pedal
3
. In the hydraulic booster, in the same manner as the vacuum booster, the first valve element
5
a
moves together with the input shaft
4
and the second valve element
5
b
moves together with the power piston
10
b.
By the way, such conventional brake systems employ various brake controls such as for controlling the braking force during the braking action, for example, Brake Assist Control for increasing the braking force when the braking force is insufficient for emergency brake or the like, and Regenerative Brake Coordination Control to be performed when a regenerative brake system is used to develop braking pressure during the braking action by the service brake system, and automatic brake controls, for example, a brake control for controlling the distance from a vehicle in front, a brake control for avoiding a collision with an obstacle object, and Traction Control (TRC).
Most of such brake controls are normally conducted in a brake circuit between the master cylinder and the wheel cylinders. However, when the brake control is conducted in the brake circuit after the master cylinder, it is required to prevent the travel of the brake pedal or pedaling force from being affected by such brake controls, for instance, for obtaining better operational feeling.
However, in a conventional brake system, the travel of a piston of the master cylinder is fixed by the relation between the master cylinder and wheel cylinders or the relation between the master cylinder and the stroke simulator so that the stroke of an input shaft of the brake booster, i.e. the pedal travel of a brake pedal, depends on the travel of the piston of the master cylinder. That is, the travel for input is affected by the brake controls conducted in the brake circuit after the master cylinder. In the conventional brake system, the aforementioned requirement can not be securely and sufficiently satisfied.
For changing the travel characteristic of the brake pedal as the input side to obtain better operational feeling, the master cylinder and the brake circuit after the master cylinder are also affected so that some modifications on the output side, for instance a size change on the master cylinder, should be required. By the change on the output side, the output characteristic of the brake system is affected. This means that the overall modification on the brake system is required, i.e. large-scale modification is required.
It is further desired that the input side is affected as little as possible by brake circuit which may differ according to the type or size of vehicle.
If the input side and the output side are just separated from each other to produce outputs regardless of the travel of the input side, the input side does not travel so that the travel of the input side can not be ensured.
For this, a full power brake system has been conventionally proposed in which a stroke simulator is provided on the brake circuit after the master cy
Inoue Hidefumi
Kanazawa Osamu
Kobayashi Michio
Maki Kazuya
Niino Hiroaki
Bosch Braking Systems Co. Ltd.
Kanesaka & Takeuchi
Kershteyn Igor
Look Edward K.
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