CROSS REFERENCE TO RELATED APPLICATION

The disclosure of Japanese Patent Application No. 2019-171158 filed on Sep. 20, 2019 including specification, drawings and claims is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a technique for liquid replacement in a channel which supplies a liquid in a circulating manner to a discharge head which discharges the liquid from a nozzle.

2. Description of the Related Art

Conventionally, a printing apparatus is known which performs printing by discharging an ink (liquid) from a nozzle of a discharge head by an inkjet method. Further, a printing apparatus described in JP 2009-101516A includes a supply tank which supplies an ink to a discharge head and a recovery tank which recovers the ink from the discharge head, and the ink is circulated between the supply tank and the recovery tank by returning the ink, which is flowed from the supply tank into the recovery tank via the discharge head, to the supply tank.

SUMMARY OF THE INVENTION

At the time of printing, the liquid can be discharged from the nozzle of the discharge head while the liquid is successively supplied to the discharge head by circulating the liquid in the above circulation channel. On the other hand, it has not necessarily been appropriate to circulate the liquid between a feed reservoir (supply tank) and a return reservoir (recovery tank) by the above circulation channel at the time of maintenance or the like besides printing. This is because minute foreign substances may be gradually generated from the liquid due to a load (e.g. a load by pumping) applied to the liquid by continuing to circulate the liquid. Thus, if the liquid is circulated in the above circulation channel, foreign substances may be mixed into the discharge head.

This invention was developed in view of the above problem and aims to provide a technique capable of circulating a liquid between a feed reservoir and a return reservoir while suppressing the mixing of foreign substances into a discharge head.

A printing apparatus according to the invention1, comprises: a feed reservoir; a discharge head which discharges a liquid supplied from the feed reservoir via a feed channel from a nozzle; a return reservoir which recovers the liquid from the discharge head via a return channel; a bypass channel configured to feed the liquid from the feed reservoir to the return reservoir by bypassing the discharge head; a liquid feed unit which performs a first liquid feeding operation of feeding the liquid from the feed reservoir to the return reservoir; and a control unit which selectively carries out a normal circulation of returning the liquid flowed into the discharge head from the feed reservoir to the feed reservoir by way of the return reservoir by causing the liquid feed unit to perform the first liquid feeding operation with the feed channel and the return channel opened while the bypass channel is closed and a bypass circulation of returning the liquid flowed into the bypass channel from the feed reservoir to the feed reservoir by way of the return reservoir by causing the liquid feed unit to perform the first liquid feeding operation with the bypass channel opened while the feed channel and the return channel are closed.

A liquid circulation method according to the invention in a printing apparatus for supplying a liquid from a feed reservoir via a feed channel to a discharge head which discharges the liquid and recovering the liquid from the discharge head via a return channel to a return reservoir, comprises: carrying out a normal circulation of returning the liquid flowed into the discharge head from the feed reservoir to the feed reservoir by way of the return reservoir with the feed channel and the return channel opened while a bypass channel which feeds the liquid from the feed reservoir to the return reservoir by bypassing the discharge head is closed; and carrying out a bypass circulation of returning the liquid flowed into the bypass channel from the feed reservoir to the feed reservoir by way of the return reservoir with the bypass channel opened while the feed channel and the return channel are closed.

In the invention (printing apparatus, liquid circulation method in the printing apparatus) thus configured, the liquid flowed into the discharge head from the feed reservoir can be returned to the feed reservoir by way of the return reservoir by carrying out the normal circulation. Thus, the liquid circulated by the normal circulation can be discharged from the nozzle of the discharge head at the time of normal printing. On the other hand, the liquid flowed into the bypass channel from the feed reservoir can be returned to the feed reservoir by way of the return reservoir by carrying out the bypass circulation. Since this bypass channel bypasses the discharge head, the liquid does not pass through the discharge head in the bypass circulation. As a result, the liquid can be circulated between the feed reservoir and the return reservoir while the mixing of foreign substances into the discharge head from the respective reservoirs is suppressed.

As described above, according to the invention, it is possible to circulate the liquid between the feed reservoir and the return reservoir while suppressing the mixing of foreign substances into the discharge head from the respective reservoirs.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for purpose of illustration only and is not intended as a definition of the limits of the invention.

