Machine element or mechanism – Control lever and linkage systems – Foot operated
Reexamination Certificate
2002-03-21
2003-12-23
Luong, Vinh T. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Foot operated
C074S560000
Reexamination Certificate
active
06666105
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brake pedal apparatus for inputting an operational force of a driver into a brake system for actuating brakes and, more particularly, to a brake pedal apparatus of which the lever ratio (hereinafter, referred to as “pedal leverage”) is changeable.
In most brake systems for automobiles, brakes are actuated by pedaling force applied by depressing a brake pedal.
FIG. 17
is an illustration schematically showing the basic structure of a typical conventional brake system with a brake pedal. In
FIG. 17
, numeral
1
designates a brake system,
2
designates a brake pedal for brake operation,
3
designates a booster for amplifying the pedaling force on the brake pedal
2
by power such as fluid pressure, negative pressure, or air pressure (positive pressure),
4
designates a tandem-type master cylinder (hereinafter, sometimes referred to as “MCY”) which is actuated by the output of the booster
3
to develop master cylinder pressure,
5
and
6
designate wheel cylinders (hereinafter, sometimes referred to as “WCYs”) of a first brake circuit which generate braking force by the MCY pressure supplied as braking pressure to them,
7
and
8
designate WCYs of a second brake circuit which generate braking force by the MCY pressure supplied as braking pressure to them, and
9
designates a reservoir of the MCY
4
.
In this brake system
1
, an input shaft
3
a
of the booster
3
is advanced (moved to the left in
FIG. 17
) by depression of the brake pedal
2
and the booster
3
thus amplifies the pedaling force to output amplified power. By the output of the booster
3
, the MCY
4
is actuated to develop MCY pressure which is then supplied to the respective wheel cylinders
5
,
6
,
7
,
8
, thereby actuating brakes with large braking force i.e. amplified pedaling force.
By the way, in such a brake system
1
, the lever ratio (L
1
+L
2
)/L
1
of a lever
2
a
of the brake pedal
2
, i.e. the pedal leverage, is normally constant, wherein L
1
is a distance between a pivot of the lever
2
a
and a connection point where the input shaft
3
a
of the booster
3
is connected to the lever
2
a,
and L
2
is a distance between the connection point and the center of the brake pedal
2
. The constant pedal leverage leads to the following problems:
(1) in case of failure of amplifying action of the booster
3
(for example, power source failure), required pedaling force should be too large;
(2) under some condition, the pedal stroke may be increased, thus giving the driver a bad pedaling feel;
(3) a driver such as an inexpert driver may not produce large braking force even in case of emergency braking;
(4) the brake pedal may largely shift to the driver during a vehicle collision; and
(5) in such a design for improving the fuel consumption rate that brake pads are spaced largely (there is a limitation of spacing because the loss stroke of the brake pedal
2
should be considered) apart from brake disks or brake drums to prevent brake calipers from dragging, the pedal stroke should be longer.
Though there is a conventional pedal apparatus in which the pedal leverage can be adjusted by changing the joint position between the lever
2
a
of the brake pedal
2
and the input shaft
3
a
of the booster
3
(or the input shaft of the MCY
4
) in case of booster failure, this apparatus can not completely solve the aforementioned problems and, in addition, the operation for changing the joint position is troublesome.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a brake pedal apparatus capable of easily changing its pedal leverage and therefore solving the aforementioned problems.
To achieve the aforementioned object, a brake pedal apparatus of the present invention comprises: a first lever member of which a middle portion is pivotally supported to a vehicle body by a first pivot pin; a second lever member which is provided at its one end with a pedal member and is pivotally connected to one end of said first lever member by a second pivot pin and to which an input shaft of a booster or an input shaft of a master cylinder is pivotally connected; a pivotal movement control means for controlling said first lever member in such a manner as to prevent the pivotal movement of said first lever member when a predetermined condition is not satisfied and to allow the pivotal movement of said first lever member when the predetermined condition is satisfied; and a coupling means for coupling said first and second lever members to pivot together when the pivotal movement of said first lever member is allowed.
The present invention is also characterized in that an end of said second lever member positioned opposite to said pedal member is pivotally connected to the end of said first lever member positioned opposite to said pedal member, and the input shaft of said booster or the input shaft of said master cylinder is pivotally connected to the second lever member at a position on the pedal member side relative to said first pivot pin.
Further, the present invention is characterized in that a middle portion of said second lever member is pivotally connected to the end of said first lever member positioned at the pedal member side, and the input shaft of said booster or the input shaft of said master cylinder is pivotally connected to the second lever member at a position on the side opposite to said pedal member relative to said first pivot pin.
In addition, the present invention is characterized in that said second lever member and the input shaft of said booster or said master cylinder are pivotally connected via a third lever member.
The present invention is also characterized in that said pivotal movement control means comprises: a receiving portion disposed at a position of said vehicle body which corresponds to the one end of said first lever member; an engaging means disposed on the one end of said first lever member and capable of engaging said receiving portion; and an engagement control means for controlling the engagement between said engaging means and said receiving portion in such a manner as to disengage said engaging means by the satisfaction of said predetermined condition, which engages said receiving portion to prevent the pivotal movement of said first lever member, from said receiving portion to allow the pivotal movement of said first lever member.
The present invention is characterized in that said predetermined condition is whether the pedaling force exceeds a preset threshold value or not, and said engagement control means controls the engagement in such a manner as to maintain said engaging means in the engaged state with said receiving portion when said pedaling force is smaller than the preset threshold value and to disengage said engaging means from said receiving portion when said pedaling force exceeds said preset threshold value.
Furthermore, the present invention is characterized in that said predetermined condition is whether the pedaling force exceeds a first preset threshold value or not and whether the pedal stroke exceeds a second preset threshold value or not, and said engagement control means controls the engagement in such a manner as to disengage said engaging means from said receiving portion only when said pedaling force exceeds said first threshold value and said pedal stroke is smaller than said second threshold value.
The present invention is characterized in that said predetermined condition is whether the pedaling speed exceeds a preset threshold value or not, and said engagement control means controls the engagement in such a manner as to maintain said engaging means in the engaged state with said receiving portion when said pedaling speed exceeds the preset threshold value and to disengage said engaging means from said receiving portion when said pedaling speed is lower than said preset threshold value.
The present invention is characterized in that said predetermined condition is whether said pedal member is moved backward from its inoperative position or not, an
Bosch Braking Systems Co. Ltd.
Kanesaka & Takeuchi
Luong Vinh T.
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