Ink supply device for inkjet recording apparatus

An ink supply device for an inkjet recording apparatus comprising a back pressure tank, a distribution tank, a plurality of ink opening/closing electromagnetic valves, and a plurality of recording heads, and in which the distribution tank is connected to the back pressure tank via an ink supply path, the plurality of ink opening/closing electromagnetic valves is directly attached to the distribution tank while being connected to the plurality of recording heads via a distribution supply pipe, characterized in that

• the back pressure tank contains a float that floats in contact with substantially the entire upper liquid surface of ink stored therein;
• the back pressure tank is provided with a liquid surface detector for detecting the height of the upper liquid surface of the ink via the float;
• an upper part inside of the back pressure tank communicates with the atmosphere via an air path, an air switching three-port electromagnetic valve, and an air filter connected to the air switching three-port electromagnetic valve;
• a cover and a plate are attached to the distribution tank with a frame sandwiched therebetween, and a space provided in the flame is filled with ink;
• an air vent member for removing air in the frame is connected to a top of the frame in the distribution tank;
• a plate-shaped humidification heater is attached in a sandwiched state between the frame and the plate;
• and
• a temperature sensor for measuring the temperature of ink in the space is attached to the frame or the plate.