JPH1024602A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer without the need of consuming an extra ink or extra time even when a flushing treatment is conducted. SOLUTION: A CPU 8 stores image data to be recorded in a heat output buffer 12. With an optional timing, the image data are transmitted to a recording head by opening a gate 15. The recording head records an image on a paper by discharging an ink based on the transmitted image data. The CPU 8 stores the image data in a heat output hysteresis buffer 13 during the sampling time of about 20 seconds. After the time, a flushing treatment is conducted. That is, the data content is reversed and transmitted to the recording head 3 so as to conduct an empty discharge according to the reversed data. Therefore, the empty discharge is conducted only to a discharge opening where an ink has not been discharged in the sampling time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called serial ink jet printer which performs image recording by ejecting ink from a recording head while moving the recording head in parallel to a recording medium. In particular, the present invention relates to an ink jet printer having a flushing function for preventing ink clogging of ink discharge ports of a recording head.

[0002]

2. Description of the Related Art In a recording head of a serial ink jet printer, a plurality of ink discharge ports such as 64, 128, etc. are arranged at a predetermined interval, for example, 1/1, in a direction substantially perpendicular to the moving direction of the recording head. They are arranged side by side at 360 inch intervals. The act of recording an image on a recording medium, such as paper, is performed by moving the recording head in parallel with the recording medium, that is, by performing main scanning, while moving ink from several ink ejection ports appropriately selected based on image data. This is performed by discharging

[0003] In a conventional ink jet printer, a so-called flushing process is performed in order to prevent an ink discharge port that did not discharge ink during an image recording operation from drying out. This flushing process is
A process in which the recording head is periodically carried to a position separated from the recording medium at a time interval of, for example, about 20 seconds, and ink is ejected from the plurality of ink ejection ports in that state to prevent the ink from drying at each ejection port. is there. The ejection of the ink for flushing is performed, for example, about 500 times within a time of about 50 ms.

In a conventional ink jet printer, whether an ink ejection port ejects ink during an image recording operation,
Alternatively, the idle discharge of the ink is uniformly performed for all the ink discharge ports in the recording head regardless of whether the ink discharge ports have not discharged the ink. Therefore, in the conventional ink jet printer, since the ink ejection port that does not dry due to the ejection of the ink during the image recording operation is also uniformly ejected, there is a problem that wasteful ink is consumed. there were.

In a conventional ink jet printer, a flushing process is executed even when ink is ejected from all the ink ejection ports within a certain length of time during an image recording operation. In this case, the recording head is transported to a predetermined location for the flushing process, and further, an idle discharge operation is performed.

An ink jet printer similar to the ink jet printer according to the present invention is disclosed in
There is one disclosed in Japanese Patent Application No. -305159. In this publication, the discharge amount of the idle discharge of the ink for the flushing process is controlled for each discharge port in accordance with the recording image, so that the wettability of each discharge port is uniformly maintained, etc. There is disclosed a technique for preventing occurrence of density unevenness in a recorded image. However, in this publication,
There is no disclosure of a configuration in which the presence / absence of ink ejection within a predetermined time for each ink ejection port is stored and an ejection port for performing ink ejection for flushing is selected based on the information. There is no disclosure of the effect of reducing the amount of ink consumed during the flushing process and saving the processing time.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a conventional ink jet printer, and does not waste ink even when performing a flushing process. Another object of the present invention is to provide an ink jet printer that does not waste time.

[0008]

In order to achieve the above object, an ink jet printer according to the present invention comprises a recording head having a plurality of ink ejection ports, and a recording head for moving the recording head in parallel with respect to a recording medium. An inkjet printer having a head moving unit. The ink jet printer further includes an ink ejection storage unit for storing whether or not each of the plurality of ink ejection ports has ejected the ink within a predetermined length of sampling time, and a recording head from the recording medium. Flushing control means for idle-ejection of ink from some or all of the plurality of ink ejection ports in a state where the ink ejection port is moved to a deviated position. Further, the flushing control means selects an ink ejection port from which ink is to be ejected idle based on whether or not the ink is ejected stored by the ink ejection storage means. The above sampling time can be set freely,
For example, it can be set to about 20 seconds.

The flushing control means, for example, performs idle ejection for flushing at an ink ejection port where no ink is ejected within a sampling time during an image recording operation, and performs ink ejection during which the ink is ejected within the sampling time. At the outlet, ON / OFF of idle discharge of ink from each ink discharge port is controlled so that idle discharge for flushing is not performed.

[0010]

According to the ink jet printer of the present invention, it is possible to prevent idle discharge of the ink for the flushing process from being performed at the discharge port that discharges the ink for image recording during the image recording operation. Can be prevented. Further, when the ink for image recording is ejected from all the ejection ports within a predetermined time during the image recording operation, the flushing process can be omitted, and thus the time for the image recording operation can be shortened.

[0011]

FIG. 1 shows an embodiment of an ink jet printer according to the present invention. This ink jet printer includes a carriage 2 disposed opposite a conveyance path of a sheet 1 as a recording medium,
It has a recording head 3 fixedly disposed on the upper side, and an endless annular transport belt 4 for driving the carriage 2. The transport belt 4 functions as a recording head moving unit for moving the recording head 3 in parallel. The sheet 1 is transported by a transport device (not shown) and moves in the direction of arrow B for sub-scanning. The transport belt 4 is stretched around a driving pulley 5a and a driven pulley 5b, and a motor 6 is connected to the driving pulley 5a. When the motor 6 operates, the transport belt 4 moves orbitally, and the orbital movement causes the carriage 2 and the recording head 3 to reciprocate in a direction parallel to the sheet 1 as indicated by an arrow A, thereby performing main scanning on the sheet 1. The encoder 7 fixed to the side surface of the carriage 2 detects the position of the carriage 2 in the main scanning direction indicated by the arrow A, that is, the position of the recording head 3, and outputs it as an electric signal. A plurality of ink ejection ports (not shown) for ejecting ink toward the paper 1 are provided on a surface of the recording head 3 facing the paper 1. For example, 64 ink ejection ports are provided at 1/360 inch intervals in a direction perpendicular to the main scanning direction indicated by arrow A. Each ink ejection port is provided with a well-known ink ejection mechanism, for example, an ink ejection mechanism using a piezoelectric element.

A cap position C and a flash position D are set at positions within the movement area of the recording head 3 in the direction of the arrow A and out of the movement path of the sheet 1 in the direction of the arrow B. The cap position C is a position for preventing the ink ejection ports from drying out by covering the surface of the recording head 3 where the ink ejection ports are provided with a cap. Further, the flash position D is a position for discharging ink from the ink discharge port irrespective of the discharge of ink for image recording, that is, for performing idle discharge to eliminate clogging of the ink in the ink discharge port. . At the flash position D, an ink absorbing member, for example, a sponge or the like, for collecting the idle-discharged ink is provided as necessary.

FIG. 2 shows an essential part of one embodiment of an electric control system of the ink jet printer of the present embodiment. This control system is a CP that controls overall control for an image recording operation.
U8, a ROM 10 storing a predetermined program for the image recording operation, a RAM 11 used as a work area when performing each process for the image recording operation, and image data to be supplied to the recording head 3. And a head output buffer buffer 13 for storing whether or not ink has been ejected within a predetermined length of sampling time during the image recording operation for each ink ejection port in the recording head 3. , And a timer 14 for counting the sampling time. The image data stored in the head output buffer 12 is
The recording head 3 is sent to the recording head 3 through a gate 15 which opens and closes according to a command from the printer 8.

The head output buffer 12 is composed of, for example, a flip-flop FF1, as shown in FIG. The head output history buffer 13 includes, for example, a flip-flop FF2 and an OR circuit 16. Image data is input to one input terminal of the OR circuit 16 through the internal bus 9, and an output signal of the FF 2 is input to the other input terminal. Note that FF1,
The units including the FFs 2, the OR circuit 16, and the gates 15 are provided by the number of ink ejection ports provided in the recording head 3. Therefore, in this embodiment in which 64 ink ejection ports are provided, the same number of units are prepared.

The CPU 8 is provided with an operation unit for performing various operations for image recording processing. In the operation unit, the ink is discharged from the ink discharge ports in an idle state, and the operation of the ink discharge ports is performed. A flushing calculation unit for calculating a flushing process performed to eliminate ink clogging or the like is also included.

The operation of the ink jet printer having the above configuration will be described below. First, the CPU 8 checks whether image data has been received as shown in FIG. 4 (step S1). If it is determined that the image data has been received, the recording head 3 is carried out from the cap position C, and an image recording operation is performed (steps S2 and S3).

The image recording operation is executed, for example, as follows. That is, in FIG. 2, the position of the recording head 3 with respect to the sheet 1 is detected by the encoder 7, and the gate 15 corresponding to each of the ink discharge ports is appropriately recorded with reference to the detected position information. Open at the timing. As a result, the image data stored in the head output buffer 12 is sent to the recording head 3 at an appropriate timing, and ink is ejected from an ink ejection port at an appropriate position. As a result, a desired image is formed on the paper 1. Be recorded.
When the image data is sent to the head output buffer 12, the image data is also sent to the history buffer flip-flop FF2 through the OR circuit 16. The output signal of the flip-flop FF2 is the OR circuit 16
, The image data sent to the FF2 as described above is held by the FF2 until the FF2 is cleared. That is,
The head output history buffer 13 includes a flip-flop FF
During a predetermined sampling time until 2 is cleared,
The fact that the image data has been input, that is, the fact that ink has been ejected from the ink ejection ports for image recording, is stored. The sampling time for storing the presence or absence of ink ejection is set to, for example, about 20 seconds.

The above-described image recording operation is continuously executed while image data is being received by the CPU 8 (NO in step S4). When the reception of the image data is completed (YES in step S4), the recording head 3 is returned to the cap position C, and all the ink ejection ports are covered with the caps. Prevent it from drying out.

The CPU 8 executes an interruption process for the flushing process shown in FIG. 5 at a predetermined timing while the image recording action is being executed in step S3 in FIG. In this flushing process, first, information in the head output history buffer 13 is read (step S1).
0). The head output history buffer 13 stores the presence or absence of ink ejection within the sampling time for the 64 ink ejection ports.

In a normal image recording operation, it is relatively rare that ink is ejected from all 64 ink ejection ports within a sampling time of about 20 seconds. It is considered that ink is often selectively discharged. As described above, when ink is ejected from several selected ejection openings,
It is determined as "NO" in step S11, and a flushing process for eliminating ink clogging or the like is performed on the ink discharge ports other than the ink discharge ports from which the ink is discharged for image recording (step S12). Specifically, the data on the presence or absence of ink ejection for each ink ejection port stored in the head output history buffer 13 is inverted, the inverted data is transferred to the head output buffer 12 and the recording head 3 Is performed.
In this way, if the idle ejection is performed only for the necessary ink ejection ports, the amount of ink consumption can be suppressed as much as possible.

On the other hand, if it is determined that ink has been ejected from all the ink ejection ports within the sampling time (YES in step S11), the CPU 8 executes the history buffer flip-flop FF without executing the flushing process.
Clear 2 and return to the main routine for image recording. In this case, since the ink is ejected from all the ink ejection ports during the image recording operation, the clogging of the ink is eliminated without performing the flushing process. By omitting the flushing process itself in this way, wasteful consumption of ink can be avoided and
The time spent for image recording can be reduced.

FIG. 6 schematically shows the relationship between the ejection of ink for image recording and the idle ejection of ink during the flushing process, corresponding to each of the ink ejection ports A to F. In this figure, a to d indicate a predetermined sampling time set to about 20 seconds, a black circle “●” indicates that ink was ejected from the ink ejection port for image recording,
“X” indicates that the idle discharge of the ink is not performed during the flushing process, and “F” indicates that the idle discharge of the ink is performed during the flushing process. As is apparent from this figure, in the three sampling times a, b and d, the idle ejection for flushing is performed only for the ink ejection openings for which no ink ejection for image recording was performed. Do. On the other hand, when ink is ejected from all the ink ejection ports for image recording as in the sampling time c, the flushing process itself is omitted, that is, idle ejection from all the ink ejection ports is omitted.

The above description does not mention whether the ink jet printer is a color printer or a monochrome printer. In the case of a single color printer, 64 ink ejection ports for a single color are arranged in a print head. In the case of a color printer, each color of yellow (Y), magenta (M), cyan (C) and black (K) is used. For 6
Four ink ejection port groups are arranged side by side in the print head in parallel with each other. The present invention is applicable to both monochrome printers and color printers.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the embodiments and can be variously modified within the technical scope described in the claims.

For example, the sampling time for storing whether or not ink has been ejected from the ink ejection port during the image recording operation is not limited to about 20 seconds. Further, the method of discharging ink from the recording head is not limited to the discharging method using a piezoelectric element or the like, but may be any other method. For example, a method in which the ink is heated and expanded and ejected may be employed. Further, in the above embodiment, as shown in FIG. 3, the ink discharge storage means for storing the presence or absence of ink discharge within a predetermined time is a flip-flop or an OR.
Although it was configured as hardware by circuits, etc., instead of this,
The inverted data of the storage content of the head output buffer 12 is
It is also possible to make a configuration such that the data is created by a software operation using U8, and the inverted data is stored in a temporary memory in the RAM 11.

[0026]

According to the ink jet printer of the present invention, it is possible to prevent the idle ejection of the ink for the flushing process from being performed at the ejection port that ejected the ink for image recording during the image recording operation. Waste of ink can be prevented and ink consumption can be reduced. Further, when ink is ejected from all the ejection ports for image recording within a predetermined sampling time during the image recording operation, the flushing process itself can be omitted, and thus the image recording time can be shortened.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a main part of an embodiment of an ink jet printer according to the present invention.

FIG. 2 is a block diagram showing one embodiment of a control system of the inkjet printer according to the present invention.

FIG. 3 is a circuit diagram showing a main part of a control system shown in FIG. 2 in detail.

FIG. 4 is a flowchart showing a process executed by a control system shown in FIG. 2;

FIG. 5 is a flowchart showing a process interrupted by the processing operation of FIG. 4;

FIG. 6 shows the ejection of ink for image recording (“●”) and the idle ejection of ink during flushing processing (“×”, “F”).
FIG. 4 is a diagram schematically showing the relationship with respect to each of the ink ejection ports A to F.

[Explanation of symbols]

Reference Signs List 1 paper (recording medium) 2 carriage 3 recording head 4 transport belt 5a drive pulley 5b driven pulley 6 motor 7 encoder 8 CPU 13 head output history buffer (ink discharge storage means) C cap position D flash position

Claims (2)

[Claims] 1. An ink jet printer comprising: a recording head having a plurality of ink ejection ports; and a recording head moving means for moving the recording head in parallel with respect to a recording medium. An ink ejection storage means for storing whether or not ink ejection has occurred within a predetermined length of sampling time; and some of the plurality of ink ejection ports with the recording head moved to a position outside the recording medium Or flushing control means for causing ink to be ejected from all of the ink, and the flushing control means sets an ink ejection port for causing ink to be ejected in an idle manner based on the presence or absence of ink ejection stored by the ink ejection storage means. An ink jet printer characterized by selecting. 2. The ink jet printer according to claim 1, wherein the flushing control means performs idle ejection for flushing at the ink ejection port where no ink is ejected within the sampling time, and the ink is ejected within the sampling time. An ink jet printer characterized by controlling idle discharge of ink from each ink discharge port so as to not perform idle discharge for flushing at the ink discharge ports.