Patent ID: 9660559
Date: 2017-05-23
CPC Classifications: B60S,H02K,H02P

Claim:
1. A brushless motor comprising: a stator having an armature coil to which a current is supplied; a rotor which is rotated by a revolving magnetic field formed by the armature coil and is connected to an operating member; a worm wheel formed with a gear meshed with the worm, an output shaft being fixed to the worm wheel; and a switching element provided on a route for supplying the current to the armature coil, the brushless motor further comprising: an output shaft sensor is provided to the gear of the worm wheel; a driving device having: a control circuit in which a detection signal of the output shaft sensor is inputted; and an inverter circuit for controlling energization for the armature coil, wherein the driving device has a rotation number control unit which controls a rotation number of the rotor with at least two control modes different in rotation number of the rotor from each other, and when a first control mode is selected from among the control modes, the rotation number control unit supplies the current to the armature coil at predetermined energization timing and controls a duty ratio indicating an ON ratio of the switching element to control the rotation number of the rotor and, when a second control mode is selected from among the control modes, the rotation number control unit supplies the current to the armature coil at energization timing advanced from the energization timing for the first control mode, thereby performing field weakening control of weakening the revolving magnetic field formed by the armature coil with respect to a revolving magnetic field for the first control mode to control the rotation number of the rotor, wherein the rotation number control unit is adapted to selectively assume the control modes, on the basis of wind resistance which is applied to a wiper blade while a vehicle is moving, wiping resistance which is applied to the wiper blade, or a change in wiping speed of the wiper blade resulting from both resistances, so as to put a wiping speed of a wiper arm of a wiper apparatus close to a target wiping speed.