Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Reexamination Certificate
2001-12-19
2004-04-13
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
Reexamination Certificate
active
06718863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum booster used for the servo operation of a brake master cylinder for a vehicle. In particular, the present invention pertains to an improved vacuum booster, wherein a booster piston is located in a booster shell to divide the interior of the booster shell into a front vacuum chamber communicating with a vacuum source and a rear operating chamber, wherein a valve piston fitted into a valve cylinder so as to be slidable forward and backward, an input rod that connects the front end thereof to the valve piston, a control valve that, in accordance with the forward and backward movement of the input rod between the valve piston and the valve cylinder, alters the communication of the operating chamber with either the vacuum chamber or the atmosphere, and an input return spring that impels the input rod backward are arranged in the valve cylinder that communicates with the booster piston, wherein the control valve is constituted by a ring-shaped vacuum introduction valve seat formed in the valve cylinder, an atmosphere introduction valve seat formed in the valve piston and positioned inside the vacuum introduction valve seat, a valve element that includes: a ring-shaped attachment bead portion securely supported at the inner wall of the valve cylinder; an elastic cylinder axially extending from the attachment bead portion; and a valve portion connected, flange-like, to the front end of the elastic cylinder and located facing the vacuum introduction valve seat and the atmosphere introduction valve seat, on which the valve portion is to be seated, and wherein a first port that communicates with the vacuum chamber is opened to the outer wall side of the vacuum introduction valve seat, and a second port that communicates with the operating chamber is opened between the vacuum introduction valve seat and the atmosphere introduction valve seat, thus enabling the inside of the valve portion to communicate with the atmosphere.
2. Description of the Related Art
Vacuum boosters are well known, as is disclosed, for example, in JP-B-58-48923U.
The periphery of the control valve of the vacuum booster disclosed in the referenced publication is shown in FIG.
6
. As is apparent from
FIG. 6
, a control valve
38
of a conventional vacuum booster includes: a ring-shaped vacuum introduction valve seat
30
, which is formed in a valve cylinder
10
; an atmosphere introduction valve seat
31
, which is formed on a valve piston
18
that is connected to an input rod
20
and is located inside the vacuum introduction valve seat
30
; a valve element
34
, which includes a ring-shaped attachment bead portion
34
b
that is securely supported by the inner wall of the valve cylinder
10
, an elastic cylinder
34
c
that extends forward from the attachment bead portion
34
b
, and a ring-shaped valve disk
34
a
that is connected, flange-like, to the front end of the cylinder
34
c
and is positioned opposite the vacuum introduction valve seat
30
and the atmosphere introduction valve seat
31
on which it is seated; and a valve spring
36
, which impels the valve disk
34
a
in the direction in which it is seated on the vacuum introduction valve seat
30
and the atmosphere introduction valve seat
31
. A first port
28
, which communicates with the vacuum chamber
2
, opens to the outer wall-side of the vacuum introduction valve
30
, and a second port
29
, which communicates with the operating chamber
3
, is opened between the vacuum introduction valve seat
30
and the atmosphere introduction valve seat
31
. An atmosphere introduction port
39
, which communicates with the inner wall of the valve disk
34
a
, is formed at the rear of the valve cylinder
10
. In addition, an input return spring
41
, which impels the input rod
20
to the rear, is retracted between the valve cylinder
10
and the input rod
20
, while a booster piston
4
is integrally coupled with the valve cylinder
10
.
Generally, for this vacuum booster, since the initial operating force exerted by the input rod
20
is determined in accordance with the set load of the input return spring
41
, it is preferable that the set load of the input return spring
41
be as small as possible in order to reduce the required operating force.
Assume that the atmosphere introduction valve seat
31
is released from the valve portion
34
a
of the valve element
34
by moving the input rod
20
forward against the set load of the input return spring
41
, that the valve portion
34
a
is seated on the vacuum introduction valve seat
30
, and that a forward propulsive force produced by a pressure difference between the vacuum chamber
2
and the operating chamber
3
is exerted on the booster piston
4
. Since in this state, atmospheric pressure acts on the front face of the valve portion
34
a
and a vacuum pressure, produced by the vacuum chamber
2
, acts on the rear face, it is necessary for the set load of the valve spring to be satisfactorily large in order to prevent the propulsive force produced by the pressure difference from releasing the valve portion
34
a
from the vacuum introduction valve seat
30
. However, when the set load of the valve spring
36
is large, accordingly, the set load of the input return spring
41
must also be large. Otherwise, when the operating force applied to the input rod
20
is released, the set load of the valve spring
36
will prevent the valve portion
34
a
from separating from the vacuum introduction valve seat
30
. This factor prevents any reduction in the set load of the input return spring
41
of the conventional vacuum booster.
SUMMARY OF THE INVENTION
To resolve this problem, it is one objective of the present invention to provide a vacuum booster wherein a smaller set load is provided for a valve spring, and accordingly, the set load of an input return spring can be reduced, as can the initial operating force applied to the input rod
20
.
To achieve the above objective, according to a first aspect of the invention, there is provided a vacuum booster, comprising:
a booster shell;
a booster piston accommodated in the booster shell to divide the interior of the booster shell into a front vacuum chamber communicating with a vacuum source and a rear operating chamber;
a valve cylinder connected to the booster piston;
a valve piston fitted into the valve cylinder so as to be slidable forward and backward;
an input rod connected to the valve piston at a front end thereof;
an input return spring urging the input rod backward; and
a control valve arranged within the valve cylinder, for changing over the communication of the operating chamber with one of the vacuum chamber and the atmosphere in accordance with the forward and backward movement of the input rod, the control valve including:
a ring-shaped vacuum introduction valve seat formed in the valve cylinder;
an atmosphere introduction valve seat formed in the valve piston and disposed inside the vacuum introduction valve seat;
a valve element having: a ring-shaped attachment bead portion securely held with respect to an inner wall of the valve cylinder; an elastic cylinder axially extending from the attachment bead portion; and, an annular valve portion connected in a flange shape to a front end of the elastic cylinder and facing the vacuum introduction valve seat and the atmosphere introduction valve seat, on which the valve portion is to be seated; and
a valve spring urging the valve portion in a direction that the valve portion is seated on the vacuum introduction valve seat and the atmosphere introduction valve seat, wherein a first port that communicates with the vacuum chamber is opened to an outer periphery side of the vacuum introduction valve seat, a second port that communicates with the operating chamber is opened between the vacuum introduction valve seat and the atmosphere introduction valve seat, and an inner periphery side of the valve portion is communicated with the atmosphere,
further wherein the valve portion is fitted with the va
Leslie Michael
Look Edward K.
McGuire Woods LLP
Nissin Kogyo Co. Ltd.
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