Image forming apparatus and non-transitory computer readable medium

1. An image forming apparatus, comprising:

a recording head including nozzles to discharge liquid droplets;

a head tank including a liquid containing part to contain liquid supplied to the recording head;

a main tank to contain the liquid supplied to the head tank; and

a controller to control, after detection of an end state of the main tank, post-end printing using the liquid remaining in the head tank corresponding to the main tank in the end state,

wherein the controller permits the post-end printing when an amount of the liquid remaining in the head tank to which the liquid is supplied from the main tank in the end state is a predetermined threshold remaining amount or greater.

2. The image forming apparatus according to claim 1 , wherein the main tank is formed of at least two main tanks, and the controller controls the post-end printing to be performed using the liquid in at least one main tank of the at least two main tanks that is not in the end state.

3. The image forming apparatus according to claim 2 , wherein, in the post-end printing, the controller controls the liquid remaining in the head tank corresponding to a main tank of the at least two main tanks that is in the end state to be used only for a maintenance operation of maintaining a performance of the nozzles.

4. The image forming apparatus according to claim 1 , further comprising:

a liquid feeder disposed between the head tank and the main tank; and

a pressure detector to detect pressure in a liquid supply passage from the main tank to the head tank,

wherein, when the pressure in the liquid supply passage detected with the pressure detector in feeding the liquid from the main tank to the head tank is a threshold value or lower, the controller determines that the main tank is in the end state.

5. The image forming apparatus according to claim 4 , further comprising an air releaser openable and closable to release an inside of the liquid containing part of the head tank to atmosphere,

wherein the liquid feeder is a reversible liquid feeder, and when the controller determines that the main tank is in the end state, the controller opens the air releaser to release the inside of the liquid containing part of the head tank to the atmosphere and rotates the reversible liquid feeder in reverse to return the liquid from the head tank to the main tank by a predetermined amount.

6. The image forming apparatus according to claim 1 , further comprising a notifier to notify that the controller permits the post-end printing.

7. The image forming apparatus according to claim 1 , wherein the controller stops the post-end printing when a usage of the liquid in the head tank corresponding to the main tank in the end state is a threshold usage amount.

8. The image forming apparatus according to claim 1 , wherein the controller stops the post-end printing when an elapsed time period from a start of the post-end printing reaches a threshold time period.

9. The image forming apparatus according to claim 1 , wherein the controller controls printing in the post-end printing to be performed using the liquid remaining in the head tank corresponding to the main tank in the end state.

10. A non-transitory computer readable medium storing a program to cause a computer to execute a process for an image forming apparatus including a liquid discharge head including nozzles to discharge liquid droplets, a head tank including a liquid containing part to contain liquid supplied to the liquid discharge head, and a main tank to contain the liquid supplied to the head tank,

the process comprising:

controlling, after detection of an end state of the main tank, post-end printing using the liquid remaining in the head tank corresponding to the main tank in the end state; and

permitting the post-end printing when an amount of the liquid remaining in the head tank to which the liquid is supplied from the main tank in the end state is a predetermined threshold remaining amount or greater.