Fluid pressure boosting device

Details Fluid pressure boosting device Fluid pressure boosting device

2002-04-15

2003-12-02

Look, Edward K. (Department: 3745)

Power plants

Pressure fluid source and motor

Pulsator

C091S369200

Reexamination Certificate

active

06655140

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a fluid pressure boosting device, which boosts operating force exerted on an operating means with working fluid pressure into predetermined magnitude to output boosted force and, more particularly, to a fluid pressure boosting device with a so-called jumping characteristic.
For example, fluid pressure boosting device is employed in a brake fluid pressure boosting device of a type utilized in brake systems of automotive vehicles. Such a brake fluid pressure boosting device is for boosting pedaling force on a brake pedal into predetermined magnitude to output. The output of the brake fluid pressure boosting device actuate a master cylinder so that the master cylinder develops master cylinder pressure corresponding to the output of the brake fluid pressure boosting device. The master cylinder pressure is supplied to wheel cylinders, thereby actuating brakes.
Among conventional brake fluid pressure boosting devices, a brake fluid pressure boosting device of a center-valve type with a so-called jumping characteristic is known in which a control valve is located in a power piston. According to the jumping characteristics, as shown in
FIG. 3
, little or none output is produced until loss stroke in the brake system is cancelled so that substantial brake pressure is attained after, while large output is produced when substantial brake pressure is attained after loss stroke in the brake system is cancelled. Because of the jumping characteristic, the braking pressure boosting device can output braking pressure well corresponding to the input as compared to a device without jumping characteristic as shown by a dotted line of FIG.
3
.
As an example of conventional brake fluid pressure boosting devices having the aforementioned jumping characteristic is disclosed in Japanese Unexamined Patent Publication No. 2000-177576.
FIG. 4
is a sectional view showing a brake fluid pressure boosting device and a tandem-type master cylinder disclosed in the above publication. The master cylinder is actuated by output of the brake fluid pressure boosting device. Detail explanation of components and actions of the brake fluid pressure boosting device and the master cylinder will be omitted because these should be understood upon a reading of the publication. The components and actions will be just simply explained.
When any braking action is not taken as shown in
FIG. 4
, in the brake fluid pressure boosting device
1
and the master cylinder
2
, a brake pedal (not shown) is not depressed so that an input shaft
3
connected to the brake pedal does not travel and a control valve
4
is thus in its inoperative state as shown in FIG.
4
. That is, a valve ball
5
of the control valve
4
is seated on a first valve seat
7
fixed to a power piston
6
and is spaced apart from a second valve seat
8
disposed on an end of a cylindrical member
8
a
connected to the input shaft
3
integrally. Therefore, a power chamber
9
, which is always in communication with a second-valve-seat-side portion of the cylindrical member
8
a,
communicates with a booster reservoir (not shown) through a space between the valve ball
5
and the second valve seat
8
, an axial hole
10
formed in the cylindrical member
8
a,
an axial hole
11
and a radial hole
12
formed in the input shaft
3
, a radial hole
14
formed in a plug
13
, an axial hole
16
formed in a housing
15
, and a discharge port
17
. Hydraulic fluid introduced from a fluid pressure source (not shown) through an input port
18
is not supplied to the power chamber
9
. Therefore, the power piston
6
is not actuated and the brake fluid pressure boosting device
1
outputs nothing.
The right end
19
a
of a reaction piston
19
which is slidably fitted around the input shaft
3
is spaced apart from a step
3
a
of the input shaft
3
. In addition, a flange (stopping portion)
20
a
of a cylindrical stopper member
20
connected to the input shaft
3
is in contact with an end
13
b
of a cylindrical projection
13
a
of the plug
13
and is spaced apart from a stopper
19
c
of a first flange
19
b
of the reaction piston
19
. That is, the flange
20
a
of the cylindrical stopper member
20
is in a position advanced relative to the stopper
19
c.
The master cylinder
2
is also not operated. In this state, a radial hole
22
formed in a primary piston
21
is positioned behind a cup seal
23
so that a primary chamber
24
communicates with a master-cylinder reservoir
27
through the radial hole
22
and holes
25
,
26
. Further, a radial hole
29
of a secondary piston
28
is in a position behind a cup seal
30
so that the secondary chamber
31
communicates with the master-cylinder reservoir
27
through radial holes
29
and passages
32
,
33
. Therefore, no master cylinder pressure is developed in the primary chamber
24
and the secondary chamber
31
.
Upon depression of the brake pedal for braking operation, the input shaft
3
, the cylindrical stopper member
20
, and the cylindrical member
8
a
advance so that the valve ball
5
is seated on the second valve seat
8
and is spaced apart from the first valve seat
7
, thereby switching the control valve
4
. Therefore, the power chamber
9
is isolated from the booster reservoir, which is always in communication with the axial hole
10
of the cylindrical member
8
a,
and communicates with the input port
18
, whereby hydraulic fluid is introduced into the power chamber
9
from the fluid pressure source. By the hydraulic fluid introduced into the power chamber
9
, the power piston
6
advances so that the brake fluid pressure boosting device
1
outputs. Then, the primary piston
21
advances such that the radial hole
22
passes the cup seal
23
, thereby isolating the primary chamber
24
from the master-cylinder reservoir
27
. As a result, master cylinder pressure is developed in the primary chamber
24
.
At the same time, the hydraulic fluid in the power chamber
9
is introduced into both wheel cylinders of one circuit of the brake system through a hole
34
formed in the housing
15
. Because of the master cylinder pressure developed in the primary chamber
24
, the secondary piston
28
advances such that its radial hole
29
passes the cup seal
30
, thereby isolating the secondary chamber
31
from the master-cylinder reservoir
27
. As a result, master cylinder pressure is developed in the secondary chamber
31
too. The master cylinder pressure developed in the secondary chamber
31
is introduced into both wheel cylinders of the other circuit of the brake system from a secondary output port
35
.
As mentioned above, the inner pressure of the power chamber
9
, and the respective master cylinder pressures of the primary chamber
24
and the secondary chamber
31
are equal to each other so that hydraulic fluid at the same fluid pressure is supplied to the respective wheel cylinders. That is, braking pressures at the two circuits of the brake system are equal to each other. The hydraulic fluid in the power chamber
9
is also introduced into a chamber
37
through an axial hole
36
. By the fluid pressure in the chamber
37
, a valve member
38
supporting the valve ball
5
is biased in a direction against the input of the input shaft
3
.
Because of the fluid pressure in the power chamber
9
, the reaction piston
19
is shifted to the right relative to the power piston
6
and the input shaft
3
against the spring force of the spring
39
. Since loss strokes exist in the respective wheel cylinders, however, no braking force is substantially produced by the wheel cylinders at an initial operational stage. In this initial operational stage, the rear end (the right end in
FIG. 4
)
19
a
of the reaction piston
19
moves to such a position before the step
3
a
of the input shaft
3
. Therefore, the rear end
19
a
of the reaction piston
19
does not come in contact with the step
3
a
of the input shaft
3
so that no force is exerted on the input shaft
3
from the reaction piston
19
. Therefore, exerted

Affiliated with

Also associated with

Rating

Fluid pressure boosting device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Fluid pressure boosting device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluid pressure boosting device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3154425