Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2001-11-07
2003-10-28
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
Reexamination Certificate
active
06637201
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a master cylinder. More particularly, it relates to a master cylinder that is suited for an automobile on which a working fluid is returned from a wheel cylinder to a reservoir through a working fluid passage for the master cylinder when brake control is released on an automobile provided with a unit in which a working fluid for the wheel cylinder is pressurized by pumping-up to carry out brake control (traction control unit, automobile stability control unit, etc.), and that decreases the noneffective piston stroke of the master cylinder at the time of ordinary operation.
FIG. 20
is a sectional view showing one example of a conventional master cylinder, which has been disclosed in Japanese Patent Application Provisional Publication No. 10-53120 (No. 53120/1998). This master cylinder
1
has a piston
3
fitted slidably in a cylinder bore
2
a
formed in a cylinder body
2
, and is provided with a pressure delivering chamber
4
defined by the piston
3
and a supply passage
5
. The piston
3
is fitted with a valve mechanism
6
and a floating throttle valve mechanism
7
on the extension of the axial line. The valve mechanism
6
opens an axial hole
12
with a flange
10
integral with a rod
9
being separated from an annular member
11
in response to the retreat of the piston
3
to the return position effected by a return spring
8
installed in the pressure delivering chamber
4
, and closes the axial hole
12
with the flange
10
coming into contact with the annular member
11
in response to the advance of the piston from the return position.
Also, the floating throttle valve mechanism
7
, which is provided with a floating member
13
having a throttle hole
13
a
, moves the floating member
13
to a throttling position at which a throttle effect is given to the flow of a working fluid when the working fluid flows toward a reservoir, not shown, and moves the floating member
13
to a non-throttling position at which no throttle effect is given to the flow of the working fluid when the working fluid flows from the reservoir toward the pressure delivering chamber
4
through the axial hole
12
.
The piston
3
begins to operate in the state in which the valve mechanism
6
is open, and advances in the left-hand direction in the figure, whereby the valve mechanism
6
is closed. Therefore, the communication between the pressure delivering chamber
4
and the supply passage
5
is cut off. Subsequently, by moving the piston
3
further in the left-hand direction, a pressure is delivered in the pressure delivering chamber
4
, and the working fluid is discharged through an output port
14
. During the time elapsing from when the piston
3
begins to advance to when the valve mechanism
6
closes, the working fluid in the pressure delivering chamber
4
is made to flow by the advance of the piston
3
so as to go into the supply passage
5
through the floating throttle valve mechanism
7
and the valve mechanism
6
. At this time, by the flow of the working fluid, the floating member
13
of the floating throttle valve mechanism
7
closes a communication hole
15
a
in a case
15
. Thereby, the working fluid in the pressure delivering chamber
4
is made to flow into the supply passage
5
through the throttle hole
13
a
in the floating member
13
. The quantity of working fluid flowing from the pressure delivering chamber
4
into the supply passage
5
decreases as compared with the case where the flow of working fluid from the pressure delivering chamber
4
to the supply passage
5
is not throttled.
However, for a master cylinder used for an automobile provided with a traction control unit and an automobile stability control unit, in the case where there is provided a throttle valve mechanism (for example, an orifice) for decreasing the quantity of working fluid flowing from the pressure delivering chamber
4
to the reservoir at the time of operation start (at the time of piston advance), there arises a problem in that a delay in returning fluid to the reservoir or a delay in lowering the fluid pressure in the pressure delivering chamber
4
is encountered because of the interposition of the throttle valve mechanism in the passage when the working fluid is returned from the wheel cylinder to the reservoir via a make-up liquid passage of the master cylinder at the time when the traction control unit and the automobile stability control unit are released.
Also, in the case where the throttle valve mechanism is provided in a portion in which the master cylinder and the reservoir are connected to each other, when liquid is returned from the pressure delivering chamber to the reservoir, there arises a problem in that a high pressure is delivered in a portion in which the master cylinder and the reservoir are connected to each other, and a force acts in the direction toward the reservoir tank, so that the cost is increased by the increased strength of a tank holding construction.
For these reasons, there has been demanded a master cylinder having a construction in which the throttle valve mechanism can respond quickly to an increase/decrease in the quantity of the returned working fluid (that is, a change in pressure) at the time when the traction control unit and the automobile stability control unit are released.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a master cylinder for an automobile provided with a traction control unit and an automobile stability control unit, which has a simple and small valve construction which can decrease the quantity of working fluid flowing to a reservoir at the time of operation start of master cylinder, and can respond to the fluctuations in fluid pressure quickly when the traction control unit and the automobile stability control unit are released, and which is capable of decreasing the noneffective piston stroke.
To achieve the above object, the present invention is configured as follows in a master cylinder in which a piston is disposed slidably in a cylinder bore formed in a cylinder body; a pressure delivering chamber is defined by the piston and the cylinder body; a fluid passage, which connects the pressure delivering chamber to a reservoir, for resupply the working fluid to the pressure delivering chamber is provided; and a working fluid whose pressure is increased in the pressure delivering chamber is discharged through an output port at the operation time of the piston.
A throttle valve mechanism having a throttle function of throttling the flow of working fluid from the pressure delivering chamber to the reservoir at the operation time of the piston, a valve function of allowing the working fluid to flow from the reservoir to the pressure delivering chamber by opening the valve at the return time of the piston, and a relief valve function of allowing the working fluid to flow from the pressure delivering chamber to the reservoir is disposed in the fluid passage.
The throttle valve mechanism has a valve seat provided at the tip end of a connector of the reservoir with the cylinder body, and a floating valve disc formed of an elastic material formed with a throttle hole and a plurality of slits in a substantially central portion thereof, which has a valve seat face which is seated against the valve seat.
Alternatively, the throttle valve mechanism has a thin-sheet or thin-film valve sheet formed of an elastic material, a rib formed at the tip end of the connector of the reservoir with the cylinder body, with which the valve sheet comes into contact from the pressure delivering chamber side, and a fixing portion for fixing the valve sheet, and in the normal state in which the valve sheet is not deformed, a slit for throttling is formed between the outer peripheral edge of the valve sheet and the inner peripheral face of tip end of the connector of the reservoir.
Alternatively, the throttle valve mechanism has two large-diameter and small-diamet
Chiba Kunihiro
Chiba Shusaku
Hirayama Junichi
Alston & Bird LLP
Bosch Braking Systems Co. Ltd.
Kershteyn Igor
Look Edward K.
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