1. Technical Field
The present invention relates to an inkjet printer having a choke unit for closing the ink path at a position on the ink path between the ink cartridge and the printhead.
2. Related Art
Ink ejection problems can result from air bubbles in the ink path flowing into the printhead. Inkjet printers may therefore have a bubble trap disposed to the ink path to capture any air bubbles. Such inkjet printers perform a choke cleaning operation to purge the bubbles in the bubble trap from the printhead side when the air bubbles in the bubble trap are expected to reach a preset size.
This choke cleaning operation closes the ink path at a position upstream from the bubble trap by means of a choke unit. The nozzle face of the printhead is then covered by a cap, the inside of the cap is then depressurized by a suction means, and negative pressure is produced in the ink path. The choke unit is then opened in this negative pressure state, and the bubbles in the bubble trap are discharged in a burst with ink from the ink nozzles.
An inkjet printer that performs this choke cleaning operation is described in JP-A-2003-301964.
The choke unit of the inkjet printer described in JP-A-2003-301964 has a disc disposed inside the ink path, and an electromagnet on the outside of the ink path. The disc has a support member made from a magnetic material, and moves between a closed position choking the ink path closed, and an open position where the ink path is open. To choke the ink path closed, the electromagnet is driven to attract the support member by the force of magnetic attraction and move the disc from the open position to the closed position.
Because magnetic force is inversely proportional to the distance squared, it is not easy to increase the stroke of the disc that opens and closes the ink path or to increase the magnetic force applied to the disc when using a configuration that moves a disc located inside the ink path by means of magnetic force from outside the ink path. The flow path of the ink path must therefore be narrow in the area around the choke unit, and flow resistance therefore increases in this area. Because pressure loss increases when the flow resistance increases, controlling the amount of ink in the ink droplets ejected from the printhead with good precision becomes difficult.