Inkjet recording device and inkjet recording method

1. An inkjet recording device comprising:

a first pressure source which contains ink and causes the ink to have a first energy per unit volume relative to a reference static ink under atmospheric pressure at a height level of nozzles of a print head;

an upstream-side flow channel which connects the first pressure source to the print head;

a second pressure source which contains ink which has passed through the print head, and causes the ink to have a second energy per unit volume relative to the reference static ink;

a downstream-side flow channel which connects the print head to the second pressure source;

a return flow channel which connects the second pressure source to the first pressure source and completes a circulation channel;

a first temperature sensor;

a second temperature sensor; and

a control device which changes at least one of the energies per unit volume of the first and second pressure sources,

the print head comprising a nozzle branch point which connects the upstream-and downstream-side flow channels to the nozzles,

the first temperature sensor configured to detect an ink temperature of ink that is upstream of the nozzle branch point,

the second temperature sensor configured to detect an ink temperature of ink that is downstream of the nozzle branch point, and

the control device configured to maintain an ink pressure in the nozzles at a predetermined value by controlling at least one of the first and second energies per unit volume based on a flow channel resistance ratio of a flow channel resistance of the upstream-side flow channel and a flow channel resistance of the downstream-side flow channel, the flow channel resistances being determined based on the temperatures detected by the first and second temperature sensors.

2. The inkjet recording device of claim 1 , wherein

the flow channel resistances are based on a viscosity-to-temperature characteristic of the ink.

3. The inkjet recording device of claim 1 , wherein

the first temperature sensor comprises a plurality of first temperature sensors, and

the control device maintains ink pressure in the nozzles at the predetermined value, based on temperatures detected by the plurality of first temperature sensors, the temperature detected by the second temperature sensor, and a viscosity-to-temperature characteristic of the ink.

4. The inkjet recording device of claim 1 , wherein the second temperature sensor comprises a plurality of second temperature sensors, and

the control device maintains the ink pressure in the nozzles at the predetermined value, based on temperatures detected by the plurality of second temperature sensors, the temperature detected by the first temperature sensor, and a viscosity-to-temperature characteristics of the ink.

5. The inkjet recording device of claim 1 , further comprising:

a first pump provided on the return flow channel;

a main tank connected to an inlet side of the first pump through an ink-amount adjustment channel; and

a second pump provided on the ink-amount adjustment channel.

6. The inkjet recording device of claim 5 , wherein

the first pump pumps ink from the second pressure source to the first pressure source so that a height of a liquid surface of the ink in the first pressure source is maintained lower than a predetermined height, and

the second pump pumps the ink from the main tank into the circulation channel or pumps the ink back to the main tank, depending on a height of a liquid surface of the ink in the second pressure source.

7. The inkjet recording device of claim 1 , wherein the control device controls a pump to adjust a height of the liquid surface of the ink in one of the first pressure source and the second pressure source so that the ink pressure in the nozzles is maintained at the predetermined value.

8. An inkjet recording device comprising:

a first pressure source which contains ink and causes the ink to have an energy per unit volume P 1 relative to a reference static ink under atmospheric pressure at a height level of nozzles of a print head;

an upstream-side flow channel which connects the first pressure source to the print head;

a second pressure source which contains ink which has passed through the print head, and causes the ink to have an energy per unit volume P 2 relative to the reference static ink;

a downstream-side flow channel which connects the print head to the second pressure source;

a return flow channel which connects the second pressure source to the first pressure source and completes a circulation channel;

a flow channel resistance ratio calculation device which calculates a flow channel resistance ratio r between a flow channel resistance R 1 (Pa*s/m 3 ) of the upstream-side flow channel and a flow channel resistance R 2 (Pa*s/m 3 ) of the downstream-side flow channel, according to a relationship of R 1 :R 2 =1:r, the flow channel resistances R 1 and R 1 being determined based on a temperature distribution of the ink; and

a control device which controls at least one of P 1 and P 2 in accordance with the calculated flow-channel resistance ratio r, so that a nozzle pressure Pn is maintained at a predetermined value calculated according to an expression of Pn=P 1 *r/(1+r)+P 2 /(1 +r).

9. The inkjet recording device of claim 8 , wherein the flow channel resistance ratio r is based on at least an ink temperature detected in ink that is upstream of the nozzles of the print head, an ink temperature detected of ink that is downstream of the nozzles of the print head, and a viscosity characteristic of the ink.

10. The inkjet recording device of claim 8 , wherein the temperature distribution of the ink in at least one of the upstream and downstream flow channels is determined based on temperatures separately detected in each of a plurality of parts of the at least one of the upstream and downstream flow channels.

11. The inkjet recording device of claim 8 , further comprising:

a first pump provided on the return flow channel;

a main tank connected to an upstream side of the first pump through an ink-amount adjustment channel; and

a second pump provided on the ink-amount adjustment channel.

12. The inkjet recording device of claim 11 , wherein

the first pump pumps ink from the second pressure source to the first pressure source so that a height of a liquid surface of the ink in the first pressure source is maintained lower than a predetermined height, and

the second pump pumps the ink from the main tank into the circulation channel or pumps the ink back to the main tank, depending on a height of a liquid surface of the ink in the second pressure source.

13. An inkjet recording method comprising:

causing ink contained in a first pressure source to have a first energy per unit volume relative to a reference static ink under atmospheric pressure at a height level of nozzles of a print head connected to the first pressure source;

storing ink which has passed through the print head, in a second pressure source, and causing the ink in the second pressure source to have a second energy per unit volume, relative to the reference static ink;

pumping ink from the second pressure source to the first pressure source through a return flow channel, thereby circulating the ink;

detecting a first ink temperature of ink that is upstream of the nozzles of the print head;

detecting a second ink temperature of ink that is downstream of the nozzles of the print head; and

controlling at least one of the first and second energies per unit volume based on a flow channel resistance ratio of a flow channel resistance of an upstream-side flow channel between the first pressure source and the print head, and a flow channel resistance of a downstream-side flow channel between the print head and the second pressure source, the flow channel resistances being determined based on the first and second detected ink temperatures.

14. The inkjet recording method of claim 13 , further comprising:

controlling at least one of the first and second energies per unit volume to maintain an ink pressure in the nozzles at a predetermined value, based on the first and second detected ink temperatures and on a viscosity-to-temperature characteristic of the ink.

15. The inkjet recording method of claim 13 , further comprising:

detecting plurality of first ink temperatures at different positions between the nozzles and the first pressure source; and

controlling at least one of the first and second energies per unit volume to maintain an ink pressure in the nozzles at a predetermined value, based on the detected first ink temperatures, the detected second ink temperature, and on a viscosity-to-temperature characteristic of the ink.

16. The inkjet recording method of claim 13 , further comprising:

detecting a plurality of second ink temperatures at different positions between the nozzles and the second pressure source; and

controlling at least one of the first and second energies per unit volume to maintain an ink pressure in the nozzles at a predetermined value, based on the detected first ink temperature, the detected second ink temperatures, and on a viscosity-to-temperature characteristic of the ink.

17. The inkjet recording method of claim 13 , wherein the ink is pumped from the second pressure source to the first pressure source so that a height of a liquid surface of the ink in the first pressure source is maintained lower than a predetermined height.

18. The inkjet recording method of claim 13 , wherein the ink is pumped from or to a main tank, depending on a height of a liquid surface of the ink in the second pressure source.

19. An inkjet recording method comprising:

causing ink contained in a first pressure source to have a first energy per unit volume relative to a reference static ink under atmospheric pressure at a height level of nozzles of a print head connected to the first pressure source;

storing ink which has passed through the print head, in a second pressure source, and causing the ink in the second pressure source to have a second energy per unit volume, relative to the reference static ink;

pumping ink from the second pressure source to the first pressure source through a return flow channel, thereby circulating the ink;

detecting a first ink temperature of ink that is upstream of the nozzles of the print head;

detecting a second ink temperature of ink that is downstream of the nozzles of the print head; and

maintaining an ink pressure in the nozzles at a predetermined pressure by controlling at least one of the first and second energies per unit volume, based on a flow channel resistance ratio of a flow channel resistance of an upstream-side flow channel between the first pressure source and the print head, and a flow channel resistance of a downstream-side flow channel between the print head and the second pressure source, the flow channel resistances being determined based on the first and second detected ink temperatures.

20. The inkjet recording method of claim 19 , wherein the step of maintaining the ink pressure comprises:

controlling a pump to adjust a height of the liquid surface of the ink in one of the first pressure source and the second pressure source so that the ink pressure in the nozzles is maintained at the predetermined value.