Vehicle brake system and method of detecting wear of friction member

1. A vehicle brake system, comprising:

an electric brake device including (a) a friction member, (b) a rotor configured to rotate with a wheel, (c) a motor as a power source, and (d) a driven member configured to be moved forward and backward by the motor, the electric brake device being configured to generate a braking force such that the driven member is moved forward by the motor so as to press the friction member and the friction member is brought into contact with the rotor; and

a wear detector configured to detect wear of the friction member and including (A) a data obtaining section configured to obtain an amount of a forward movement of the driven member corresponding to a distance by which the driven member moves forward and a pressing force by which the driven member presses the friction member, (B) a contact-start-position detecting section configured to detect a contact start position at which the driven member is located when the friction member starts to contact the rotor, and (C) a remaining-thickness estimating section configured to estimate a remaining thickness of the friction member based on the contact start position detected by the contact-start-position detecting section,

wherein the wear detector further includes an uneven-wear detecting section configured to detect uneven wear of the friction member indicative of a state in which the friction member is unevenly worn, by comparing: a relationship between the amount of the forward movement and the pressing force obtained by the data obtaining section; and a relationship between an amount of the forward movement and a pressing force in a case where it is supposed that a thickness of the friction member is equal to the remaining thickness that would be estimated by the remaining-thickness estimating section in a state in which the friction member is evenly worn.

2. The vehicle brake system according to claim 1 ,

wherein a change of the obtained pressing force with respect to a change of the obtained amount of the forward movement is defined as an actual change gradient, and a change of the pressing force with respect to a change of the amount of the forward movement in the case where it is supposed that the thickness of the friction member is equal to the remaining thickness that would be estimated by the remaining-thickness estimating section in the state in which the friction member is evenly worn is defined as an estimated change gradient, and

wherein the uneven-wear detecting section determines that there is a risk of uneven wear of the friction member when the electric brake device is in a situation in which the actual change gradient, which becomes constant after having increased in accordance with the forward movement of the driven member from the contact start position, is larger than the estimated change gradient.

3. The vehicle brake system according to claim 2 , wherein the uneven-wear detecting section estimates that the electric brake device is in the situation in which the actual change gradient is larger than the estimated change gradient and determines that there is the risk of uneven wear of the friction member, when the pressing force obtained by the data obtaining section becomes larger than an upper limit value that is set based on the relationship between the amount of the forward movement and the pressing force in the case where it is supposed that the thickness of the friction member is equal to the remaining thickness that would be estimated by the remaining-thickness estimating section in the state in which the friction member is evenly worn.

4. The vehicle brake system according to claim 1 ,

wherein a change of the obtained pressing force with respect to a change of the obtained amount of the forward movement is defined as an actual change gradient, and a change of the pressing force with respect to a change of the amount of the forward movement in the case where it is supposed that the thickness of the friction member is equal to the remaining thickness that would be estimated by the remaining-thickness estimating section in the state in which the friction member is evenly worn is defined as an estimated change gradient, and

wherein the uneven-wear detecting section determines that there is a risk of uneven wear of the friction member when the electric brake device is in a situation in which the actual change gradient, which is increasing as the driven member moves forward from the contact start position, is smaller than the estimated change gradient.

5. The vehicle brake system according to claim 4 ,

wherein the uneven-wear detecting section estimates that the electric brake device is in the situation in which the actual change gradient is smaller than the estimated change gradient and determines that there is the risk of uneven wear of the friction member, when the pressing force obtained by the data obtaining section becomes smaller than a lower limit value that is set based on the relationship between the amount of the forward movement and the pressing force in the case where it is supposed that the thickness of the friction member is equal to the remaining thickness that would be estimated by the remaining-thickness estimating section in the state in which the friction member is evenly worn.

6. A method of detecting wear of a friction member in an electric brake device including (a) a friction member, (b) a rotor configured to rotate with a wheel, (c) a motor as a power source, and (d) a driven member configured to be moved forward and backward by the motor, the electric brake device being configured to generate a braking force such that the driven member is moved forward by the motor so as to press the friction member and the friction member is brought into contact with the rotor, the method comprising:

obtaining an amount of a forward movement of the driven member corresponding to a distance by which the driven member moves forward and a pressing force by which the driven member presses the friction member;

detecting a contact start position at which the driven member is located when the friction member starts to contact the rotor;

estimating a remaining thickness of the friction member based on the detected contact start position; and

detecting uneven wear of the friction member indicative of a state in which the friction member is unevenly worn, by comparing: a relationship between the obtained amount of the forward movement and the obtained pressing force; and a relationship between an amount of the forward movement and a pressing force in a case where it is supposed that a thickness of the friction member is equal to the remaining thickness that would be estimated in a state in which the friction member is evenly worn.