Dishwasher

A dishwasher comprising:

• a tub that defines a washing space;
• a sump disposed below the tub and configured to store washing water received from the tub;
• a pump configured to supply the washing water stored in the sump to the washing space;
• and
• a spray arm configured to discharge the washing water from the pump into the washing space,
• wherein the spray arm defines a channel therein configured to carry the washing water received from the pump, the spray arm being configured to spray the washing water or the washing water including microbubbles into the washing space,
• wherein the spray arm comprises an upper cover and a lower cover that have inner surfaces facing each other, the lower cover being coupled to a lower side of the upper cover,
• wherein the spray arm has:
• a flat surface that is defined at one of the inner surfaces of the upper cover and the lower cover, and
• a pair of inner ribs that protrude from the other of the inner surfaces of the upper cover and the lower cover to the flat surface, the pair of inner ribs being in contact with the flat surface to thereby define the channel between the pair of inner ribs,
• wherein the spray arm comprises:
• a first blade configured to spray the washing water into the washing space, and
• a second blade configured to supply the washing water including the microbubbles to the washing space,
• wherein the channel comprises (i) a spray channel defined inside the first blade and (ii) a bubble generating channel defined inside the second blade,
• wherein the upper cover comprises an upper rib that protrudes downward, and the lower cover comprises a lower rib that protrudes upward to the upper rib to thereby define the spray channel between the upper cover and the lower cover, and
• wherein the flat surface and the pair of inner ribs are disposed in the second blade and define at least a portion of the bubble generating channel.