Fluid-pressure and analogous brake systems – Electric control
Reexamination Certificate
1999-08-18
2001-02-13
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Electric control
C188S158000, C188S162000, C188S072100
Reexamination Certificate
active
06186599
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake apparatus and, more particularly, to an electric brake apparatus having a brake motor which is rotated in a normal direction so as to generate a braking force and rotated in a reverse direction so as to cancel the braking force.
2. Description of the Related Art
Japanese Laid-Open Patent Application No.7-291120 discloses an electric brake apparatus having a disc brake which includes an electrically driven caliper and a disc rotor rotating with a wheel. The electrically driven caliper is driven by a brake motor so as to generate a clamping force. When a power supply to the brake motor is stopped, the clamping force of the electrically driven caliper is cancelled. More specifically, the brake motor moves brake pads provided on the electrically driven caliper toward the disc rotor so that a braking force is generated by the brake pads being pressed against the disc rotor. In order to cancel the braking force, the brake motor moves the brake pads in a direction opposite to the direction toward the disc rotor. Hereinafter, the rotation of the brake motor in the direction to generate the braking force is referred to as a normal rotation, and the direction of the normal rotation is referred to as a normal direction. Additionally, the rotation of the brake motor in a direction to cancel the braking force is referred to as a reverse rotation, and the direction of the reverse rotation is referred to as a reverse direction.
When the brake motor is rotated in the reverse direction, there may be a case in which the brake motor is driven by an excessive power. In such a case, parts provided around a motor shaft of the brake motor may be damaged due to excessive rotation. Additionally, a clearance gap between the disc rotor and the brake pads is increased, which increases a response time of a subsequent braking operation. Accordingly, in order to prevent the parts from being damaged and maintain a quick response of a braking operation, it is necessary to appropriately prevent the brake motor from being excessively rotated in the reverse direction.
In the conventional brake apparatus, a mechanical clutch is provided so as to disengage the brake motor from the caliper when an excessive power is generated by the brake motor in the reverse direction so that the excessive power is not transmitted to the caliper. However, there is a problem in that the entire structure of the electric brake apparatus is complex due to addition of the mechanical clutch.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful electric brake apparatus in which the above-mentioned problem is eliminated.
A more specific object of the present invention is to provide an electric brake apparatus which can positively prevent a brake motor from being excessively rotated in a reverse direction in which a braking force is cancelled.
In order to achieve the above-mentioned object, there is provided according to the present invention an electric brake apparatus for generating a braking force by driving a brake motor in a predetermined direction, the braking force being canceled by driving the brake motor in a reverse direction opposite to the predetermined direction, said electric brake apparatus comprising:
excessive rotation determining means for determining whether or not the brake motor is excessively driven in the reverse direction; and
motor stopping means for stopping an operation of the brake motor when the brake motor is determined to be excessively driven in the reverse direction.
According to the above-mentioned invention, since the brake motor is stopped when it is determined that the brake motor is excessively driven in the reverse direction, a member of the electric brake apparatus moved by the brake motor is prevented from being excessively moved beyond a predetermined position. Accordingly, a part of the electric brake apparatus is prevented from being damaged due to an excessive movement of the member moved by the brake motor with a simple structure as compared to a mechanical structure.
In the above-mentioned invention, the excessive rotation determining means may include a rotation sensor detecting a rotational angle of a rotational shaft of said brake motor so that the excessive rotation determining means determines that the brake motor is excessively rotated when the rotational shaft is rotated beyond a predetermined angle in the reverse direction.
Additionally, in the electric brake apparatus according to the present invention, the motor stopping means may include a fuse which blows when a current exceeding a predetermined current flows to said brake motor in a direction in which said brake motor is driven in the reverse direction.
Further, in the electric brake apparatus according to the present invention, the excessive rotation determining means may include a current detecting circuit detecting a current flowing to the brake motor in a direction in which the brake motor is driven in the reverse direction, and the motor stopping means may stop the operation of the brake motor when the current detected by the current detecting circuit exceeds a predetermined value.
According to this invention, when the current flowing to the brake motor in the reverse direction exceeds the predetermined value, the brake motor is stopped. When the operation of the brake motor in the reverse direction is not restricted, a small current flows to the brake motor. However, if the operation of the brake motor is restricted for some reason, a large load is applied to the brake motor which results in an increase in the current flowing to the brake motor. Accordingly, if the current flowing to the brake motor exceeds a predetermined value when the brake motor is driven in the reverse direction, it can be determined that the brake motor is excessively driven in the reverse direction. In the present invention, the brake motor is stopped when the current flowing to the brake motor in the reverse direction exceeds the predetermined value. Thus, a part of the electric brake apparatus is prevented from being damaged due to an excessive movement of a member moved by the brake motor with a simple structure as compared to a mechanical structure.
The electric brake apparatus according to the present invention may further comprise a reciprocal member reciprocally movable by operation of the brake motor so as to press a brake pad against a brake disc rotating with a wheel, wherein the excessive rotation determining means may calculate a travel of said reciprocal member based on a rotational angle of a rotational shaft of the brake motor so that the excessive rotation determining means determines that the brake motor is excessively rotated when the reciprocal member travels beyond a predetermined position in a direction in which the brake motor is driven in the reverse direction.
The above-mentioned electric brake apparatus may further comprise an excessive reverse-rotation switch which turns on when the reciprocal member reaches the predetermined position, wherein the motor stopping means stops the operation of the brake motor when the excessive reverse-rotation switch is turned on.
Additionally, the electric brake apparatus according to the above-mentioned invention may further comprise means for determining whether or not the brake motor is driven in the reverse direction for a continuous period longer than a predetermined period after the brake pad is separated from the brake disc, wherein the motor stopping means may stop the operation of the brake motor when the brake motor is driven in the reverse direction for the continuous period longer than the predetermined period.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 4804073 (1989-02-01), Taig et al.
patent: 5366280 (1994-11-01), Littlejphn
patent: 5931268 (1999-08-01), Kingston et al.
Otomo Akihiro
Shirai Kenji
Butler Douglas C.
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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