Fluid-pressure and analogous brake systems – Speed-controlled – Torque sensing
Reexamination Certificate
2001-06-22
2002-07-30
Graham, Matthew C. (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
Torque sensing
C303S020000, C303S152000, C188S111001
Reexamination Certificate
active
06425643
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrically operated braking system of a motor vehicle, which includes a brake employing an electric motor as a drive source.
2. Discussion of the Related Art
An electrically operated braking system of a motor vehicle generally includes (a) a brake operating member such as a brake pedal, which is operated by an operator of a motor vehicle, (b) an electric power source such as a battery, (c) a brake including an electric motor which is operated by an electric power supplied from the electric power source, to generate a drive force for forcing a friction member onto a rotor rotating with a wheel of the vehicle, for thereby braking the wheel, and (d) a controller which determines an amount of the electric power to be supplied from the electric power source to the electric motor, depending upon an operating amount of the brake operating member, for thereby controlling an operation of the brake.
A friction coefficient of friction members such as brake pads or brake linings used in a brake generally varies due to gradual deterioration or wearing of the friction members, or due to temperature or humidity of the friction members. Further, the friction members have different friction coefficient values due to variations associated with the manufacture. In an electrically operated braking system as described above, a change in the friction coefficient of the friction members will cause a change in the relationship between the amount of electric power actually supplied from the electric power source to the electric motor of the brake and the braking torque actually applied from the brake to the corresponding wheel. In other words, the relationship between the amount of electric power supplied to the motor and the braking torque generated by the brake is not necessarily held constant.
However, the conventional electrically operated braking system does not obtain and utilize the actual relationship between the supplied amount of electric power and the braking torque generated by the brake. That is, the conventional system uses a predetermined nominal relationship between the electric power amount and the braking torque, to determine the amount of electric power to be supplied to the electric motor, depending upon the operating amount of the brake operating member, on the assumption that the relationship is held constant. Therefore, the conventional electrically operated braking system is not capable of accurately controlling the braking torque of the brake in relation to the operating amount of the brake operating member.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an electrically operated braking system which obtains an actual relationship between the amount of electric power supplied to an electric motor and the braking torque generated by the brake, and utilizes the obtained relationship.
The above object may be achieved according to any one of the following modes or embodiments of the present invention, which are numbered to indicate possible combinations of various features of the invention:
(1) An electrically operated braking system of a motor vehicle having a wheel, comprising: (a) a rotor rotating with the wheel; (b) a brake operating member which is operated by an operator of the motor vehicle; (c) an electric power source; (d) a brake including a friction member movable to be forced onto the rotor, and an electric motor which is operated by an electric power supplied from the electric power source, to generate a drive force for forcing the friction member onto the rotor and thereby braking the wheel; and (e) a controller which determines an amount of the electric power to be supplied from the electric power source to the electric motor, depending upon an operating amount of the brake operating member, for thereby controlling an operation of the brake, the braking system being characterized by further comprising (e) a relationship estimating and utilizing device for obtaining an actual value of the electric power supplied from the electric power source to the electric motor during an operation of the brake while the motor vehicle is running, and an actual value of a braking torque applied from the brake to the wheel during the operation of the brake. The relationship estimating and utilizing device is adapted to estimate a relationship between the electric power to be supplied to the electric motor and the braking torque to be applied to the wheel, on the basis of the actual values obtained, and utilize the relationship. The relationship is formulated such that the braking torque to be applied to the wheel is changed with a change in the electric power to be supplied to the electric motor.
In the braking system constructed according to the above mode (1) of the present invention, the relationship estimating and utilizing device is capable of obtaining the relationship between the electric power to be supplied to the electric motor of the brake and the braking torque to be applied from the brake to the wheel. The relationship estimating and utilizing device is further adapted to utilize the obtained relationship for various purposes, for instance, for controlling the brake and providing the vehicle operator with information helpful to operate the vehicle.
The electric power to be applied to the electric motor may be expressed by a voltage or current. The electric motor of the brake may be a ultrasonic motor or DC motor. The operating amount of the brake operating member may be expressed as an operating force acting on the brake operating member, or an operating stroke or distance of the brake operating member. The operation of the brake while the vehicle is running may be a normal operation initiated by an operation of the brake operating member by the vehicle operator, or a special operation which is performed without an operation of the brake operating member, for the sole purpose of estimating the above-indicated relationship.
(2) An electrically operated braking system according to the above mode (1), wherein said relationship is a pattern of change of said braking torque with a change of said electric power, and said relationship estimating and utilizing device comprises relationship estimating means for selecting one of a plurality of candidate patterns which corresponds to a combination of the actual values obtained during the operation of the brake while the motor vehicle is running.
(3) An electrically operated braking system according to the above mode (2), wherein said relationship estimating means includes pattern memory means for storing the above-indicated plurality of candidate patterns, and pattern selecting means for selecting the above-indicated one of the plurality of candidate patterns stored in the pattern memory means.
(4) An electrically operated braking system according to any one of the above modes (1)-(3), wherein the relationship estimating and utilizing device obtains the above-indicated relationship from a plurality of different relationships between the electric power to be supplied to the electric motor and the braking torque to be applied to the wheel.
In the braking system according to the above mode (4), the control load of the relationship estimating and utilizing device is made smaller than in the braking system in which the relationship is estimated in a continuous fashion.
(5) An electrically operated braking system according to any one of the above modes (1)-(4), wherein the controller includes the relationship estimating and utilizing device, and the relationship estimating and utilizing device includes relationship utilizing means for determining a desired value of the braking torque on the basis of the operating amount of the brake operating member, and determining the value of the electric power to be supplied to the electric motor, on the basis of the determined desired value of the braking torque and according to the estimated relationship.
In this braking system, the electric power to be supplied to the electric motor d
Shirai Kenji
Yoshino Yasunori
Graham Matthew C.
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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