Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-03-22
2001-12-04
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S072100, C188S162000
Reexamination Certificate
active
06325182
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motor-driven brake system which is advantageously used for a vehicle.
As a motor-driven brake system, there can be mentioned, for example, a brake system of the type disclosed in Unexamined Japanese Patent Application Public Disclosure No. 3-45462. The brake system of this type comprises a pair of pads disposed at opposite sides of a disk, and a caliper for pressing the pads against the disk to generate a braking force. As the caliper, generally, a so-called floating type caliper which is movable along the axis of the disk is employed.
The floating type caliper comprises: a motor; a first movable member disposed at the opposite side of one pad from the disk and adapted to be moved directly by the motor; and a second movable member supporting the motor and having a claw portion disposed at the opposite side of the other pad from the disk. When the first movable member is moved by the motor to press the one pad against the disk, a reaction force acts to move the second movable member relative to the disk to thereby press the claw portion against the other pad, which is in turn pressed against the disk. Thus, the two pads move from opposite directions and press against the disk, thereby generating a braking force.
However, the above-mentioned floating type caliper poses the following problems:
In order to release the braking force, the motor is operated in a reverse direction, so that the first movable member is moved in a direction for releasing the pressure by which the one pad has applied to the disk. That is, since the first movable member is moved directly by the motor, the one pad which has been pressed by the first movable member is easily moved away from the disk. On the other hand, however, the second movable member which is not moved directly by the motor cannot enable the other pad to be moved away from the disk, so that the other pad drags against the disk. Consequently, not only does the lifetime of the pad and the disk become short, but also fuel consumption becomes high.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, the present invention has been made. It is a primary object of the present invention to provide a motor-driven brake system which prevents dragging of the pads to thereby extend the lifetime of the pads and the disk and also to suppress fuel consumption.
According to the present invention, there is provided a motor-driven brake system comprising:
a first pad and a second pad disposed at axially opposite sides of a disk, each of the pads having two opposite surfaces, one of which surfaces is adapted to abut against the disk;
a caliper for pressing the other surface of each of the first and second pads, to thereby press the pads against the disk and generate a braking force,
the caliper including a housing capable of being mounted on a non-rotatable portion of a vehicle body,
the housing containing a single electric motor;
an output portion adapted to be rotatably driven by the electric motor; and
a converting device for converting rotation of the output portion to a linear motion, the converting device including a first threaded portion and a second threaded portion having a directionally reverse relationship with each other;
a first pad pressing member disposed at one side of the disk and having one end engaged with the first threaded portion of the converting device and the other end capable of abutting against the first pad; and
a second pad pressing member extending across an outer periphery of the disk and having one end engaged with the second threaded portion of the converting device and the other end capable of abutting against the second pad,
whereby the first and second pad pressing members are capable of moving linearly reciprocally so that one of the first and second pad pressing members moves in a direction opposite to the movement of the other pad pressing member.
In the motor-driven brake system arranged as mentioned above, there is provided a converting device which is rotated by an electric motor and which has a first threaded portion and a second threaded portion having a directionally reverse relationship with each other. The first threaded portion of the converting device is engaged with a first pad pressing member and the second threaded portion of the converting device is engaged with a second pad pressing member. By this arrangement, when the converting device is rotated in a predetermined direction by the electric motor in order to release a braking force, the first pad pressing member and the second pad pressing member move in opposite directions. Therefore, each of the pads which have been pressed by the first and second pad pressing members can be easily moved away from the disk, to thereby prevent dragging.
According to the present invention, the first and second pad pressing members are movable along the axis of the disk, relative to the housing containing the motor.
According to the present invention, the first threaded portion comprises a first externally threaded portion formed in the output portion and an internally threaded portion formed on one end of the first pad pressing member for engagement with the first externally threaded portion, and the second threaded portion comprises a second externally threaded portion formed in the output portion and an internally threaded portion formed on one end of the second pad pressing member for engagement with the second externally threaded portion.
According to a first embodiment of the present invention, each of the first threaded portion and the second threaded portion has a ball screw structure.
According to one aspect of the first embodiment of the present invention, the ball screw structure includes a thread groove having a length of less than 1 pitch. By this arrangement, a high transmission ratio of the ball screw structure can be achieved.
According to another aspect of the first embodiment of the present invention, the motor-driven brake system further comprises a pad wear compensating mechanism for adjusting starting positions of the pads along the axis of the disk before operation of the first and second pad pressing members, whereby when an amount of rotation of the output portion exceeds a predetermined level during movement of the pads toward the disk caused by operation of the first and second pad pressing members, the starting positions of the pads are adjusted to positions closer to the disk relative to the starting positions before the amount of rotation of the output portion exceeds the predetermined level.
By this arrangement, when at least one of the first and second pads has been worn and rotation of the output portion driven by the electric motor exceeds a predetermined range during movement of the pads toward the disk caused by operation of the first and second pad pressing members, a pad clearance between the disk and each pad can be adjusted.
According to yet another aspect of the first embodiment of the present invention, the output portion comprises a cylindrical rotor member,
the rotor member receiving the first pad pressing member on a side of a distal end portion thereof through the first threaded portion and receiving the pad wear compensating mechanism on a side of a base end portion thereof, the first pad pressing member comprising:
a generally cylindrical inner body adapted to be reciprocally moved by the first threaded portion; and
a piston threadably engaged with an inner circumferential surface of the inner body and having a distal end associated with the first pad and a base end associated with the pad wear compensating mechanism,
the pad wear compensating mechanism comprising:
a detection device for detecting an amount of wear of at least one of the first and second pads; and
a one-way rotation transmitting device for preventing a rotation transmission path from the rotor member to the piston when the rotor member rotates in one direction during movement of the pads toward the disk caused by operation of the first and second pad pressing members, whil
Kumemura Youichi
Ohtani Yukio
Usui Takuya
Yamaguchi Tohma
Oberleitner Robert J.
Sy Mariano
Tokico Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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