Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2001-11-20
2003-04-08
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113300
Reexamination Certificate
active
06543860
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Patent Application 2000-353197 filed on Nov. 20, 2000, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
This invention generally relates to a hydraulic pressure brake device for a vehicle. More particularly, the present invention pertains to a hydraulic pressure brake device provided with an assisting device (booster) for assisting the movement of a master cylinder in response to brake pedal operation.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 3,910,048 discloses a servomotor for use in a power braking system. As illustrated in
FIG. 4
, the servomotor
12
is provided with a pressure ratio changer. The servomotor
12
is further provided with a first piston
58
and a second piston
60
for transmitting an operative force to a master cylinder. The first piston
58
is connected to a wall
28
moved by a pressure differential. The second piston
60
is coaxially disposed within the first piston
58
and serves to transmit the input force which drives a control valve
71
for producing the pressure differential. The second piston
60
also operates a hydraulic lock valve
118
disposed within the master cylinder. When the first and second pistons
58
,
60
are moved together in response to the movement of the wall
28
, fluid is introduced into a lock chamber
114
via the lock valve
118
. When the output force generated by the pressure differential reaches the maximum level, the simultaneous movement of the first and second pistons
58
,
60
ceases. Further manual force input by the operator will move the second piston
60
disposed within the first piston
58
to close the lock valve
118
and hold the hydraulic fluid within the lock chamber
114
to prevent the first piston
58
from moving.
More particularly, when the first and second pistons
58
,
60
are moved forward, hydraulic pressure is generated in each hydraulic pressure chamber
112
,
146
. The output from the first and second pistons
58
,
60
follows a line
188
(shown in
FIG. 5
) until a second chamber
32
in the servomotor
12
reaches the atmospheric pressure level. At point
190
in
FIG. 5
, the input force from a brake pedal
20
is transmitted via a plunger
70
and a sleeve
66
to the second piston
60
, wherein the second piston
60
is independently moved and a spring
130
is permitted to close a fluid passage
120
. When the second piston
60
is further moved under the above-described condition, the output follows the line
192
in FIG.
5
.
In the event the vacuum is unavailable, the second piston
60
is moved within the first piston
58
in response to the input force applied to a brake pedal
20
, whereby the fluid passage
120
is immediately closed by the valve
118
. The output under the above-described condition follows the line
196
in
FIG. 5
which shows that a larger output can be generated than the output which can be generated when the first and second pistons
58
,
60
are moved simultaneously under no power hydraulic pressure, which is represented by the line
195
in FIG.
5
.
According to the servomotor
12
disclosed in the above U.S. Pat. No. 3,910,048, when the increased hydraulic pressure is locked in the lock chamber
114
, the output follows the line
192
beyond a point
190
of the input force applied to the brake pedal
20
as shown in FIG.
5
. When the assisting device malfunctions, including the case of no negative pressure or vacuum, the output follows the line
196
corresponding to the movement of the second piston
60
disposed within the first piston
58
.
To achieve the operation described above, the servomotor
12
requires extensive modifications as compared to known servomotors to assure sufficient movement of the second piston
60
relative to the first piston
58
. This may require re-designing the entire hydraulic pressure brake device, thus causing an increase in the cost associated with manufacturing the hydraulic pressure brake device. Further, a large diameter portion of the first piston
58
is slidably and movably disposed in a hydraulic pressure chamber of the master cylinder. The first piston
58
is slidably movable in an inner bore at a rear side of the master cylinder. Therefore, the above-described construction may result in an increase in the resistance by the sliding movement at the slidably moving portion.
Accordingly, the disclosed hydraulic pressure brake device is susceptible of certain improvements with respect to minimizing the required modifications of the assisting device to substantially maintain the master cylinder under a predetermined structure so as to assure desired input/output characteristics when the assisting device malfunctions. A need also exists for a hydraulic pressure brake device which is not as susceptible to difficulties associated with sliding movement at each slidably moving portion to thus improve the brake pedal operation feeling.
SUMMARY OF THE INVENTION
A hydraulic pressure brake device includes a master cylinder, a brake operating member, a master piston, a booster, a first auxiliary piston, a pressure transmitting chamber disposed between the first auxiliary piston and the master piston, a valve mechanism, and a second auxiliary piston. The master piston is provided in the master cylinder and is moved forward in response to an input force applied to the brake operating member. The booster is provided between the master cylinder and the brake operating member and assists the movement of the master piston in response to the input force applied to the brake operating member. The first auxiliary piston is disposed behind the master piston in the master cylinder and has a larger effective cross-sectional area than the effective cross-sectional area of the master piston. The valve mechanism is disposed in the first auxiliary piston for hydraulically sealing the pressure transmitting chamber when the movement of the master piston is assisted by the booster and for connecting the pressure transmitting chamber with a reservoir when the movement of the master piston is not assisted by the booster. The second auxiliary piston is disposed between the first auxiliary piston and the booster for transmitting the boosting power generated by the booster to the first auxiliary piston when the movement of the master piston is assisted by the booster, for transmitting the input force applied to the brake operating member to the valve mechanism, and for opening the valve mechanism when the movement of the master piston is not assisted by the booster.
The hydraulic pressure brake device also includes an output member and a rod. The output member is provided in the booster for transmitting the boosting power generated by the booster to the first auxiliary piston when the movement of the master piston is assisted by the booster. The rod is provided in the second auxiliary piston for transmitting the input force applied to the brake operating member to the valve mechanism and for opening the valve mechanism when the movement of the master piston is not assisted by the booster.
According to another aspect of the invention, a hydraulic pressure brake device includes a master cylinder, a brake operating member, a master piston provided in the master cylinder and movable in a forward direction in response to an input force applied to the brake operating member, a vacuum booster provided between the master cylinder and the brake operating member to assist the movement of the master piston in response to the input force applied to the brake operating member, a first auxiliary piston possessing a front portion disposed in the rearward opening bore of the master piston and having a larger effective cross-sectional area than the effective cross-sectional area of the master piston, a pressure transmitting chamber defined between the first auxiliary piston and the master piston, and a valve member disposed in a bore in the first auxiliary piston and engageable with a valve seat when the movement of the
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Kramer Devon
Schwartz Christopher P.
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