Device for preventing elevator car from accidental movement and control method

The invention discloses a device for preventing an elevator car from accidental movement and a control method. The device comprises electric rail clamping devices which are symmetrically mounted at the top of an elevator car, contact wheels in tight contact with vertical surfaces of guide rails, and an encoder which is fixed at one end of the contact wheel. When a car door and a floor door are in an open state, whether an electric safety device of each door leaf is in an off state or not is identified; a contact type triggering device starts to enter a working state; the encoder accurately acquires a rotating angle of the contact wheel and calculates a movement distance of the contact wheel on the vertical surfaces of the guide rails; the state of the elevator car is judged through judging the movement distance of the elevator car. The device disclosed by the invention has the beneficial effects that the movement prevention device is mounted at the top of the elevator car, and the transformation of each floor station is avoided. so that the modification cost is reduced; furthermore, an electric safety switch of each door leaf of the elevator door is used for judging the device for preventing the elevator car from the accidental movement; when it is determined that the elevator door accidentally moves, the device is started up, and the guide rails are tightly clamped by the electric rail clamping devices, so that the elevator car is prevented from further accidental movement and a dangerous shearing accident is effectively avoided.