Brakes – Operators – Electric
Reexamination Certificate
1998-11-25
2001-03-13
Butler, Douglas C. (Department: 3613)
Brakes
Operators
Electric
C188S18100R, C188S162000, C303S020000
Reexamination Certificate
active
06199670
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an electric brake apparatus and, more particularly, to an electric brake apparatus which generates a brake force by using a brake motor as a power source.
2. Description of the Related Art
Conventionally, for example, as disclosed in Japanese Laid-Open Utility Model Application No.
5-22234,
an electric brake apparatus is known. The above-mentioned conventional apparatus includes a disc brake. The disc brake comprises an electrically-driven caliper including a brake motor and a disc rotor rotating with a wheel. The brake motor generates a force to hold the disc rotor by externally provided electric power. Thus, according to the above-mentioned conventional apparatus, a brake force can be generated electrically by appropriately controlling the brake motor.
A driver operating a vehicle may maintain a brake pedal being pressed for a long time when the vehicle is stopped. In this case, according to the above-mentioned conventional apparatus, a large amount of motor current may continuously flow to the brake motor. Additionally, in the above-mentioned conventional apparatus, a large amount of motor current may also continuously flow to the brake motor when a short circuit occurs in an electric circuit, for example due to a collision of the vehicle.
When a vehicle is stopped or after a collision of a vehicle occurs, there is no need to generate a large brake force in the vehicle. In this respect, the above-mentioned conventional apparatus has a problem in that an unnecessarily large amount of electric power is consumed under such a condition.
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 generates an appropriate brake force without unnecessarily consuming electric power.
In order to achieve the above-mentioned objects, there is provided according to the present invention an electric brake apparatus having a brake actuator generating a brake force, the brake actuator using a brake motor system including a brake motor as a power source, the electric brake motor comprising:
normal control means for controlling a motor current provided to the brake motor so as to generate a brake force required for a vehicle; and
motor current reducing means for reducing the motor current controlled by the normal control means under a predetermined condition.
In the above-mentioned invention, under a normal condition, the motor current is provided to the brake motor so as to generate a brake force required in response to a degree of braking operation by a driver or a moving condition of the vehicle. Accordingly, when a large brake force is required, a large amount of motor current is provided to the brake motor. In this condition, a large brake force is generated with large electric power consumption.
In the present invention, a process for reducing the motor current provided to the brake motor is performed under the above-mentioned condition. When the process for reducing the motor current is performed, a large brake force is not generated but a power consumption is reduced. Accordingly, a superior energy saving characteristic can be achieved by the electric brake apparatus according to the present invention. It should be noted that the normal control means determines a level of the motor current so that a predetermined relationship is established between the motor current and a degree of braking required by the driver as determined by such as a pedal stroke or a pedal pressing force. Additionally, the motor current reducing means sets the level of the motor current smaller than the level determined in accordance with the above-mentioned predetermined relationship.
Additionally, in the electric brake apparatus according to the present invention, the motor current reducing means may reduce the motor current controlled by the normal control means when the brake motor system is in a condition in which an overheat occurs.
In this invention, a process for reducing the motor current is performed when the brake motor system is being excessively heated due to an excessive level of the motor current being provided to the brake motor. Accordingly, the brake motor is prevented from being overheated and an energy saving characteristic of the electric brake apparatus is improved.
In the electric brake apparatus according to the present invention, the motor current reducing means may reduce the motor current controlled by the normal control means when the brake motor is continuously driven for a period exceeding a predetermined period.
When the brake motor is continuously driven for a long time, the brake motor is excessively heated. Accordingly, in this invention, the motor current is reduced when the motor current is continuously provided to the brake motor for a long time so as to prevent the brake motor from being overheated. This results in an improvement of the energy saving characteristic of the electric brake apparatus.
Additionally, in the electric brake apparatus according to the present invention, the motor current reducing means may reduce the motor current controlled by the normal control means when the brake motor is continuously driven for a period exceeding a predetermined period while generating a torque exceeding a predetermined value.
The brake motor generates a large amount of heat as the motor current is continuously driven for a long time or the brake motor generates a larger torque. Accordingly, in this invention, the motor current is reduced when the motor current is continuously provided to the brake motor for a long time while generating a large torque so as to prevent the brake motor from being overheated. This results in an improvement of the energy saving characteristic of the electric brake apparatus.
Additionally, the electric brake apparatus according to the present invention may further comprise temperature detecting means for detecting a temperature of one of the brake motors and a drive circuit driving the brake motor, and wherein the motor current reducing means may reduce the motor current controlled by the normal control means when the temperature of one of the brake motor and the drive circuit is equal to or greater than a predetermined value.
In this invention, the motor current is reduced when the temperature of the brake motor or the drive circuit is excessively high. When the motor current is reduced in such a condition, the brake motor is positively prevented from being overheated and an energy saving characteristic of the electric brake apparatus is improved.
Additionally, the electric brake apparatus according to the present invention may further comprise stopped state determining means for determining whether or not the vehicle is in a stopped state, and wherein the motor current reducing means may reduce the motor current controlled by the normal control means when the vehicle is determined to be in the stopped state.
In this invention, the process for reducing the motor current is performed when it is determined that the vehicle is in a stopped state. When the vehicle is being stopped, there is no need to generate a large brake force exceeding a brake force by which the vehicle can be maintained in the stopped state. In the present invention, the motor current is reduced so that the brake force for maintaining the stopped state is maintained. Thus, the vehicle can be maintained in the stopped state without influencing a behavior of the vehicle and a superior energy saving characteristic can be achieved.
Additionally, the electric brake apparatus according to the present invention may further comprise motor current increasing means for increasing the motor current being provided to the brake motor when the vehicle is not in the stopped state in a condition in which the motor current is reduced by the motor current reducing means.
According to
Nakamura Eiji
Niwa Satoru
Otomo Akihiro
Shirai Kenji
Yoshino Yasunori
Butler Douglas C.
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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