text: 1. Field of the Invention
  The present invention relates to a microwave oven, and more particularly, to a microwave oven including a linearly reciprocating tray, which enables food to be uniformly cooked.
  2. Description of the Related Art
  Microwave ovens are cooking devices using electronic waves. The microwave oven projects microwaves to food to be cooked to vibrate water molecules in the food, and cooks the food using frictional heat generated between water molecules as heat for cooking the food.
  When the microwaves are projected and reflected from the inner walls of a cooking chamber, traveling microwaves and the reflected microwaves are superposed, and the electromagnetic field formed within the microwave ovens exhibits strong and weak spots. Due to the inconsistent distribution of the electromagnetic field, food cannot be heated uniformly, so that food is unevenly cooked. Thus, to avoid this phenomenon, food, i.e. an object to be heated, is moved or the traveling direction of the microwaves is changed such that the microwaves are uniformly projected to the food if possible.
  Among the conventional methods, the method of using a rotary tray is widely known. However, the method of using a rotary tray has disadvantages in that, when long food is placed on the rotary tray, the long food contacts the rear wall of the cooking chamber or the inner surface of a door so that the long food cannot be smoothly rotated and cooked. Particularly, since a wall-mounted type microwave oven with a hood function has a relative longer side in the right-left direction, the rotary tray cannot effectively use cooking space of the microwave oven.
  Thus, by taking this problem into consideration, a tray device linearly reciprocating in the lateral direction is utilized. The linearly reciprocating tray device is disclosed in Korean Patent Laid-Open No. 2002-96424. The disclosed conventional linearly reciprocating tray device includes a tray having a groove formed in the lower side thereof, and a rotation member having an eccentric protrusion inserted into the groove. In the conventional linearly reciprocating tray device, when the rotation member is rotated by a motor, the eccentric protrusion or a bearing fitted around the eccentric protrusion moves along the inner surface of the groove to move the tray in the right-left direction.
  However, in the conventional linearly reciprocating tray device, since the eccentric protrusion or the bearing is inserted into or fitted around the groove while keeping a small gap, the tray hardly stays at the right and left sides of the cooking chamber and passes by the central area of the cooking chamber. Thus, food is chiefly cooked at the central area of the cooking chamber so that food cannot be uniformly cooked.
  Moreover, in the conventional linearly reciprocating tray device, since the eccentric protrusion or the bearing directly contacts the tray which may be heated heated to a high temperature during the operation of the microwave oven, the eccentric protrusion or the bearing may be deformed due to the heat unless they are made of highly heat-resistant materials.
  Additionally, according to the conventional linearly reciprocating tray device, the eccentric protrusion or the bearing must be inserted into or fitted around the groove formed in the lower side of the tray. However, since the tray, made of glass, is heavy, a user feels difficulty to clean the tray and to couple the protrusion with the groove.