Droplet ejection apparatus

Abstract

A droplet ejection apparatus comprises: (a) a recording head including a nozzle from which a droplet of a liquid is ejected, (b) a pressure chamber which is filled with the liquid and whose volume is changeable for ejecting the droplet from the nozzle, and (c) an actuator which changes the volume of the pressure chamber by a drive pulse inputted thereto; and an operating device which outputs the drive pulse to the actuator and which is capable of performing a restoring operation for restoring a droplet ejection performance of the recording head. The restoring operation includes: a first operation for outputting, a plurality of times, an ejection drive pulse as the drive pulse by which the droplet can be ejected; and a second operation for outputting, a plurality of times, a non-ejection drive pulse as the drive pulse by which the droplet can not be ejected, the second operation being performed following the first operation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and optional objects, features, and advantages of the present invention will be better understood by reading the following detailed description of a preferred embodiment of the invention when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view schematically showing an inkjet printer employing a droplet ejection apparatus as one embodiment of the present invention;

FIG. 2 is a cross-sectional view of a recording head of the inkjet printer;

FIG. 3 is a block diagram showing an electrical operation system of the inkjet printer;

FIG. 4 is a block diagram showing an inner construction of a drive circuit of the inkjet printer;

FIG. 5A is a view showing a waveform of the conventional drive pulse signal including a plurality of pulse groups;

FIG. 5B is a view of a waveform of a first pulse-train which has ejection drive pulses;

FIG. 5C is a view of a waveform of a drive pulse signal employed in the present embodiment, the signal including a plurality of pulse groups;

FIG. 5D is a view of a waveform of a second pulse-train which has non-ejection drive pulses; and

FIG. 6 is a table showing a result of an experiment in various combinations of a width of the non-ejection drive pulse and an interval interposed between successive two of the non-ejection drive pulses in the second pulse-train.

Claims

1. A droplet ejection apparatus used for a recording operation in which a droplet of a liquid is ejected on a recording medium, comprising: a recording head including (a) a nozzle from which the droplet of the liquid is ejected, (b) a pressure chamber which is filled with the liquid and whose volume is changeable for ejecting the droplet from the nozzle, and (c) an actuator which changes the volume of the pressure chamber by a drive pulse inputted thereto; andan operating device which outputs the drive pulse to the actuator, andwherein the operating device is capable of performing a restoring operation for restoring a droplet ejection performance of the recording head, the restoring operation including: a first operation for outputting, a plurality of times, an ejection drive pulse as the drive pulse by which the droplet can be ejected; and a second operation for outputting, a plurality of times, a non-ejection drive pulse as the drive pulse by which the droplet can not be ejected, the second operation being performed following the first operation.

2. The droplet ejection apparatus according to claim 1, wherein the restoring operation is performed independently of the recording operation.

3. The droplet ejection apparatus according to claim 1, wherein the non-ejection drive pulse is capable of applying vibration to a meniscus of the liquid which is formed in the nozzle.

4. The droplet ejection apparatus according to claim 1, wherein the first operation is for outputting a plurality of first pulse groups in each of which a first pulse-train having at least one pulse each as the ejection drive pulse is repeated continuously at a first period, and which are outputted such that a first interval longer than the first period is interposed between any successive two of the plurality of first pulse groups, andwherein the second operation is for outputting a plurality of second pulse groups in each of which a second pulse-train having at least one pulse each as the non-ejection drive pulse and that is repeated continuously at a second period (Ta), and which are outputted such that a second interval longer than the second period is interposed between any successive two of the plurality of second pulse groups.

5. The droplet ejection apparatus according to claim 4, wherein the first period has the same length as the second period.

6. The droplet ejection apparatus according to claim 4, wherein a number of the plurality of first pulse groups is equal to a number of the plurality of second pulse groups.

7. The droplet ejection apparatus according to claim 4, wherein a number of repetition of the first pulse-train in each of the plurality of first pulse groups is equal to a number of repetition of the second pulse-train in each of the plurality of second pulse groups.

8. The droplet ejection apparatus according to claim 4, wherein a number of said at least one pulse each as the non-ejection drive pulse in the second pulse-train is smaller than a number of said at least one pulse each as the ejection drive pulse in the first pulse-train.

9. The droplet ejection apparatus according to claim 4, wherein the first interval is longer than a time length in which each of the plurality of first pulse groups is outputted and the second interval is longer than a time length in which each of the plurality of second pulse groups is outputted.

10. The droplet ejection apparatus according to claim 4, wherein the first interval has the same length as the second interval.

11. The droplet ejection apparatus according to claim 4, wherein the second interval is shorter than the first interval.

12. The droplet ejection apparatus according to claim 1, wherein a number of outputting of the non-ejection drive pulse in the second operation is smaller than a number of outputting of the ejection drive pulse in the first operation.

13. The droplet ejection apparatus according to claim 1, wherein the ejection drive pulse is identical with the drive pulse to be outputted by the operating device in the recording operation.

14. The droplet ejection apparatus according to claim 1, wherein the ejection drive pulse is determined such that an amount of the droplet to be ejected by the ejection drive pulse is larger than an amount of the droplet to be ejected in the recording operation.

15. The droplet ejection apparatus according to claim 1, further comprising a carriage which holds the recording head and which is capable of reciprocating the recording head, under an operation by the operating device, over a recording area where the recording operation is performed and a non-recording area which is outside of the recording area,wherein the operating device is arranged to perform both of the first operation and the second operation when the recording head is located at a specific position in the non-recording area.

16. The droplet ejection apparatus according to claim 1, further comprising a carriage which holds the recording head and which is capable of reciprocating the recording head, under an operation by the operating device, over a recording area where the recording operation is performed and a non-recording area which is outside of the recording area,wherein the operating device is arranged to perform (a) the first operation when the recording head is located at a specific position in the non-recording area and (b) the second operation while the recording head is moved from the specific position to the recording area.