Brake fluid pressure generating device

Details Brake fluid pressure generating device Brake fluid pressure generating device

2001-11-27

2003-11-25

Schwartz, Christopher P. (Department: 3683)

Fluid-pressure and analogous brake systems

Speed-controlled

Having a valve system responsive to a wheel lock signal

C303S155000

Reexamination Certificate

active

06652040

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a brake fluid pressure generating device which generates brake fluid pressure via a control valve in response to operation of a brake operating means such as a brake pedal and, more particularly, to a brake fluid pressure generating device which can prevent the operating stroke of the brake operating means from being varied even with variation in consumption of brake fluid by that brake fluid pressure control is conducted regardless of the operation of the brake operating means on a wheel cylinder side of the brake fluid pressure generating device.
For example, in a conventional brake system of an automobile, a brake fluid pressure generating device has been employed which boosts a pedaling force exerted on a brake pedal by fluid pressure into predetermined magnitude to develop large brake fluid pressure. The brake fluid pressure generating device functions to provide a large braking force from a small pedaling force exerted on the brake pedal, thereby securing the braking action and reducing the fatigue of a driver.
Such conventional brake fluid pressure generating device can be roughly classified into the following types: one employing a vacuum booster for boosting the pedaling force by negative pressure to actuate the master cylinder, one employing a hydraulic booster for boosting the pedaling force by fluid pressure to actuate the master cylinder, one used in a full-power brake system for directly supplying fluid pressure to wheel cylinders, and the other one employing a pneumatic booster or an electromagnetic booster for boosting the pedaling force by compressed air or electromagnetic force to actuate a master cylinder.
FIG. 13
is a schematic illustration of a brake system with a brake fluid pressure generating device employing a conventional vacuum booster and
FIG. 14
is a schematic illustration of a brake system employing a conventional hydraulic booster. In the following description of the prior art and description of embodiments, terms such as “top”, “bottom”, “right-hand”, “left-hand” describe and correspond to the top, the bottom, the right-hand, and the left-hand in the associated drawings, and terms “front” and “rear” correspond to the left and the right in the associated drawings.
In the brake system with the brake fluid pressure generating device employing the vacuum booster shown in
FIG. 13
, an input force F
1
is exerted to an input shaft
4
of the brake fluid pressure generating device
1
by depression of a brake pedal
3
as a brake operating means 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 isolated 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 F
1
by the control valve
5
to develop control valve output pressure P
r
. The control valve output pressure P
r
is supplied to a power chamber
15
b
of the power cylinder unit
15
so that a power piston
15
a
moves to the left to produce output F
p
which is a boosted pedaling force. A master cylinder piston
16
a
is actuated by the output F
p
so that a master cylinder
16
generates master cylinder pressure P
m
which is supplied to wheel cylinder(s)
9
as braking fluid pressure P
b
, thereby actuating the brake. A reaction force F
m
from the master cylinder
16
is modulated as a reaction force F
v
by a reaction mechanism
57
and is applied to the first valve element
5
a.
Therefore, the control valve output pressure P
r
of the control valve
5
is regulated to balance the reaction force F
v
with the input force F
1
of the input shaft
4
. The reaction force F
v
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
15
a.
In the break system with the brake fluid pressure generating device employing the hydraulic booster shown in
FIG. 14
, an input force F
1
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 isolated from a low-pressure (L) valve passage
5
b
l
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 F
1
by the control valve
5
to generate control valve output pressure P
r
. The control valve output pressure P
r
is supplied to a power chamber
15
b
of the power cylinder unit
15
so that a power piston
15
a
moves to the left to produce output F
p
which is a boosted pedaling force. A master cylinder piston
16
a
is actuated by the output F
p
so that a master cylinder
16
generates master cylinder pressure P
m
which is supplied to wheel cylinder(s)
9
as braking fluid pressure P
b
, thereby actuating the brake. A reaction force F
m
from the master cylinder
16
and a reaction force by the control valve output pressure P
r
of the control valve
5
are modulated as a reaction force F
v
by a reaction mechanism
57
and is applied to the first valve element
5
a.
Therefore, the control valve output pressure P
r
of the control valve
5
is regulated to balance the reaction force F
v
with the input force F
1
of the input shaft
4
. The reaction force F
v
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
15
a.
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 generate 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
16
and the wheel cylinder(s)
9
. However, when the brake control is conducted in the brake circuit after the master cylinder, it is required to prevent the pedal stroke of or pedaling force on the brake pedal
3
from being affected by such brake controls, for instance, for obtaining better operational feeling.
However, in the aforementioned conventional brake systems, the stroke of the master cylinder piston
16
a
is defined by the relation between the master cylinder
16
and the wheel cylinder(s)
9
. Accordingly, the stroke of the input shaft
4
of the brake fluid pressure generating device
1
, i.e. the pedal stroke of the brake pedal
3
, depends on the stroke of the master cylinder piston
16
a.
That is, the stroke for input is affected by the brake controls conducted in the brake circuit after the master cylinder
16
. In the brake system employing the conventional brake fluid pressure generating device
1
, it is hard to securely and sufficiently satisfy the aforementioned requirement.
If the input side and the output sid

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