Pen input device having malfunction prevention function and method of preventing malfunction thereof

A pen input device, comprising:

• a housing having a bar form and having one end relatively narrowly opened to form a housing space;
• a resonant circuit housed within the housing;
• a tip that protrudes from an open end of the housing to the outside to form a contact portion to which a pressure is applied, said tip comprising a dielectric material and being configured to be movable within a predetermined range in a direction of a longitudinal axis of the housing, the tip being further configured to be self-centering;
• a ground shielding portion disposed in a portion of the housing in which electromagnetic induction occurs, said ground shielding portion not including the tips;
• wherein the housing further comprises a malfunction prevention portion comprising a malfunction prevention switch and an actuator configured to selectively actuate the malfunction prevention switch based on an orientation of the housing, and
• wherein the malfunction prevention switch of the malfunction prevention portion comprises a pair of electrodes connected to the portion of the housing in which the electromagnetic induction occurs and is disposed at a side of the housing, the actuator of the malfunction prevention portion comprising a tilt guide formed within the housing and separated by a predetermined distance from the pair of electrodes, and a moving member configured to move between the electrode and the tilt guide based on an orientation direction of the housing.