JP2013000962A - Ink jet recording apparatus and maintenance method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the ink discharged at the maintenance.SOLUTION: The ink jet recording apparatus includes a pressure generating means which makes the ink of a recording head ejected, a maintenance part, a time measuring part which measures time since the maintenance is carried out, and a control part which controls these. The control part minutely vibrates the ink at a standby period, and executes maintenance of the recording head at the maintenance part to have the ink in nozzles ejected by a predetermined number of times when the measured time of the time measuring part becomes predetermined time. The predetermined time is time obtained from an ejection speed decrease rate whereat a strike position shifts a predetermined number of pixels from a normal strike position because of a relationship between ejection stop time which is time elapsed while the ink stands by and the ejection speed decrease rate which is a decrease rate to an ejection speed when a normal ink is ejected. The predetermined number of times is the number of times of ejection obtained when the ejection stop time is set to the predetermined time from a relationship between the ejection stop time and the number of times of ejection for returning to the ejection speed when the normal ink is ejected.

Description

  The present invention relates to an ink jet recording apparatus and a maintenance method thereof.

  Conventionally, in an ink jet recording apparatus, if the ink in a nozzle thickens due to drying, the speed of ink droplets or non-ejection occurs, which is a cause of image quality deterioration. For this reason, there is known an ink jet recording apparatus that prevents ink from being thickly oscillated within a range not ejected during standby to prevent drying and periodically discharges ink from the nozzle, thereby preventing ink from thickening in the nozzle. (See, for example, Patent Document 1).

JP 2009-247921 A

By the way, reducing the amount of ink consumed is a normal problem, and it is desired to reduce the amount of ink discharged during maintenance as much as possible.
An object of the present invention is to suppress ink discharged during maintenance.

An ink jet recording apparatus according to the invention of claim 1
A recording head for ejecting ink from the nozzles;
Pressure generating means for discharging the ink in the nozzle by compressing the nozzle;
A maintenance unit for performing maintenance of the recording head;
A time measuring unit for measuring the time after the maintenance by the maintenance unit is performed;
A control unit for controlling the maintenance unit and the pressure generating means,
The control unit gives a first drive signal in a range where ink is not ejected to the pressure generating means during standby, and causes the ink in the nozzle to vibrate,
When the measurement time of the time measuring unit reaches a predetermined time, the maintenance unit performs maintenance of the recording head, and applies a second drive signal in a range in which ink is ejected to the pressure generating unit to provide ink in the nozzle Is discharged a predetermined number of times,
The predetermined time is a relationship between a discharge stop time that is an elapsed time in a state where ink is waiting in the nozzle and a discharge speed decrease rate that is a decrease rate with respect to a discharge speed when normal ink is discharged. It is a time obtained from the ejection speed reduction rate at which the ink landing position is shifted by a predetermined pixel from the normal landing position,
The predetermined number of times is the number of discharges obtained when the discharge stop time is set to the predetermined time from the relationship between the discharge stop time and the number of discharges that are returned to the discharge speed when normal ink is discharged. It is characterized by that.

The invention according to claim 2
A recording head having nozzles for ejecting ink;
Pressure generating means for discharging the ink in the nozzle by compressing the nozzle;
A maintenance unit for performing maintenance of the recording head;
A maintenance method for an ink jet recording apparatus, comprising: a time measuring unit that measures time since maintenance by the maintenance unit is performed;
At the time of standby, the pressure generating means is given a first drive signal in a range where ink is not ejected, and the ink in the nozzle is slightly vibrated,
When the measurement time of the time measuring unit reaches a predetermined time, the maintenance unit performs maintenance of the recording head, and applies a second drive signal in a range in which ink is ejected to the pressure generating unit to provide ink in the nozzle Is discharged a predetermined number of times,
The predetermined time is a relationship between a discharge stop time that is an elapsed time in a state where ink is waiting in the nozzle and a discharge speed decrease rate that is a decrease rate with respect to a discharge speed when normal ink is discharged. It is a time obtained from the ejection speed reduction rate at which the ink landing position is shifted by a predetermined pixel from the normal landing position,
The predetermined number of times is the number of discharges obtained when the discharge stop time is set to the predetermined time from the relationship between the discharge stop time and the number of discharges that are returned to the discharge speed when normal ink is discharged. It is characterized by that.

  According to the present invention, it is possible to suppress ink discharged during maintenance.

It is explanatory drawing which shows schematic structure of the inkjet recording device which concerns on this embodiment. FIG. 2 is a block diagram illustrating a main control configuration of the ink jet recording apparatus of FIG. 1. It is explanatory drawing which shows the normal landing position of an ink, and the state which the landing position shifted | deviated only the predetermined pixel. It is a graph which shows the relationship between the discharge stop time in each of two types of ink, and a discharge speed fall rate. It is a graph which shows the relationship between the discharge stop time in each of two types of ink, and the number of discharges returned to the discharge speed when normal ink is discharged. FIG. 2 is an explanatory diagram illustrating an interval from a nozzle surface of a recording head included in the inkjet recording apparatus of FIG. 1 to a recording medium. 6 is a table summarizing how the predetermined time and the predetermined number of inks change according to the interval and resolution between the nozzle surface of the recording head and the recording medium. It is a flowchart which shows the flow at the time of execution of the maintenance method which concerns on this embodiment.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is an explanatory diagram showing a schematic configuration of an inkjet recording apparatus 1 according to the present embodiment.
The ink jet recording apparatus 1 is a scan type ink jet printer, and ejects ink from a recording head to a recording medium to form an image on the recording medium. Here, in the scanning ink jet recording apparatus, a recording medium is transported in a predetermined direction by a transport device, and a recording head for ejecting ink scans in a direction perpendicular to the transport direction of the recording medium along the surface of the recording medium. By doing so, an image is formed on the recording medium.
As shown in FIG. 1, an inkjet recording apparatus 1 includes a recording head 2 that ejects ink onto a recording medium P, a carriage 3 that supports the recording head 2, and a guide that supports the carriage 3 so as to be movable in the scanning direction. A rail 4, a transport device 6 that transports the recording medium P, a maintenance unit 8 that cleans the nozzle surface of the recording head 2, and a moisturizing unit 9 that retains the nozzle surface of the recording head 2 are provided.

The recording head 2 is mounted on the carriage 3. The recording head 2 is formed in a rectangular parallelepiped shape, and a nozzle row in which a large number of nozzles are arranged in a row is formed on the nozzle surface 2a serving as a lower end surface thereof. It is possible to print on the recording medium P by ejecting ink from the nozzles.
In the ink jet recording apparatus 1, a total of four recording heads 2 are installed on the carriage 3 so that ink of four colors of black (K), yellow (Y), magenta (M), and cyan (C) can be ejected. ing. The four recording heads 2 are arranged in a line in the scanning direction S of the recording head. The ink used in the inkjet recording apparatus 1 is not limited to this, and other colors such as light yellow (LY), light magenta (LM), and light cyan (LC) can be used. In this case, the recording head 2 corresponding to each color is mounted on the carriage 3. As the ink, for example, an ink composed of water, a solvent, a pigment, a pigment dispersion, and a resin and containing water as a main component is used.

Each recording head 2 is connected to an ink tank 2t for storing black, yellow, magenta, and cyan inks via an ink flow path 2r such as an ink supply tube. That is, the ink in the ink tank 2t is supplied to each recording head 2 by the ink flow path 2r.
A carriage 3 that supports these recording heads 2 is movably attached to a guide rail 4. The carriage 3 is moved along the guide rail 4 by a carriage drive mechanism 31 (see FIG. 2).
The guide rail 4 is formed so as to extend along the scanning direction S of the recording head 2. The guide rail 4 can move over a home position area X which is an initial standby position of the recording head 2, a recording area Y where the recording head 2 records on the recording medium P, and a maintenance area Z where maintenance of the recording head 2 is performed. It is formed as follows.

The conveying device 6 includes a driving roller (not shown), a driven roller, a conveying belt stretched between the driving roller and the driven roller, and a motor 61 (see FIG. 2) that rotates the driving roller.
When the driving roller rotates by driving the motor 61, the conveying belt circulates between the driving roller and the driven roller and conveys the recording medium P placed on the upper surface along the conveying direction. When stopped, the circulation between both rollers is stopped, and the conveyance of the recording medium P is stopped.
The conveyance direction of the recording medium P is set to be a direction orthogonal to the scanning direction S and parallel to the surface direction of the recording medium P.

As shown in FIG. 1, the outer end of the recording area Y in which the carriage 3 is movable and the conveyance device 6 is provided is a maintenance area Z. The maintenance area Z includes the recording head 2. A maintenance unit 8 that performs head maintenance is provided. The maintenance unit 8 includes a suction device 81 that sucks ink from the nozzle surface 2a of the recording head 2, a blade 82, an ink receiver 83, and the like.
The suction device 81 is provided with four suction caps 81 a covering the nozzle surface 2 a of the recording head 2 corresponding to the number of recording heads 2. In addition, an ink communication pipe 81b communicating with the inside of the suction cap 81a is provided on the bottom surface of the suction cap 81a. A suction pump 81c is provided in the middle of the ink communication pipe 81b, and a waste ink tank 81d for receiving the sucked ink is provided at the lower end of the ink communication pipe 81b.
In the vicinity of one end of the suction cap 81 a, there is provided an ink receiver 83 that receives ink discharged when ink is ejected from the nozzles of the recording head 2, and the nozzle surface is adjacent to the ink receiver 83. A blade 82 for wiping off ink adhering to 2a is provided.
The suction pump 81c includes a cylinder pump and a tube pump, and operates in a state where the suction cap 81a covers the nozzle surface 2a, so that the ink inside the recording head 2 is discharged from the nozzle surface 2a together with foreign matter and bubbles. A suction force for suction is generated.

  In addition, a position opposite to the maintenance area Z across the conveying device 6 at the other end of the movement range of the carriage 3 is a home position area X. In this home position area X, the recording head 2 is placed. A moisturizing unit 9 for moisturizing is provided. The moisturizing unit 9 is provided with four moisturizing caps 91 that moisturize the ink of the recording head 2 by covering the nozzle surface 2a when the recording head 2 is in a standby state. These four moisturizing caps 91 are arranged corresponding to the arrangement of the recording heads 2 so as to simultaneously cover the nozzle surfaces 2a of the four recording heads 2.

  FIG. 2 is a block diagram showing a main control configuration of the inkjet recording apparatus 1. As shown in FIG. 2, the control unit 10 includes a CPU, a RAM, and a ROM. The control unit 10 includes a carriage drive mechanism 31, a motor 61 of the transport device 6, and a recording head 2 via an interface (not shown). The pressure generating means 22, the maintenance unit 8, the moisturizing unit 9, the time measuring unit 13, and the like are connected. Here, the pressure generating means 22 compresses the nozzles of the recording head 2 to discharge the ink in the nozzles. For example, a piezo element or the like is used. The time measuring unit 13 measures the time after the maintenance by the maintenance unit 8 is performed.

  The control unit 10 reciprocates the carriage 3 in the scanning direction S, repeats conveyance and stop of the recording medium P in accordance with the operation of the carriage 3, and intermittently conveys the recording medium P in the conveyance direction. The operation of the carriage drive mechanism 31 and the motor 61 of the transport device 6 is controlled.

The control unit 10 is connected to an input unit 12 including a host computer and a scanner for inputting image information, a keyboard for inputting image recording conditions, and the like. The control unit 10 receives a predetermined signal input from the input unit 12. Based on the above, the pressure generating means 22 of the recording head 2 is operated, and ink is ejected onto the recording medium P to record a predetermined image. Here, at the time of image formation or idle ejection, the control unit 10 applies a drive signal (second drive signal) in a range where ink is ejected to the pressure generating unit 22 to eject ink from the nozzles. At the time of idle ejection, the control unit 10 gives the second drive signal to the pressure generating means 22 and ejects the ink in the nozzle a predetermined number of times. On the other hand, when ink is not ejected from the recording head 2, when the so-called recording head 2 is on standby, the control unit 10 applies a driving signal (first driving signal) in a range where ink is not ejected to the pressure generating unit 22. The ink in the nozzle is vibrated slightly.
The control unit 10 controls the moisturizing unit 9 to perform a moisturizing operation by the moisturizing cap 91 in a standby state that is not during image formation or maintenance.

The control unit 10 controls the head maintenance by operating the maintenance unit 8 immediately after the power is turned on or when a predetermined maintenance start condition is met.
Here, the maintenance start condition will be specifically described.
As the maintenance start condition, the maintenance of the recording head 2 is performed by the maintenance unit 8 when the time measured by the time measuring unit 13 reaches a predetermined time. This predetermined time is stored in advance in the ROM of the control unit 10.
The predetermined time is determined based on the relationship between the ejection stop time, which is the elapsed time in a state where the ink is waiting in the nozzle, and the ejection speed reduction rate, which is the rate of decrease with respect to the ejection speed when normal ink is ejected. This is the time obtained from the discharge speed reduction rate at which the landing position is shifted by a predetermined pixel from the normal landing position.
FIG. 3 is an explanatory diagram showing a normal ink landing position and a state where the landing position is deviated by a predetermined pixel. In FIG. 3, squares indicate each pixel, and a circle indicates an ink droplet that has landed. Although FIG. 3 shows a case where the landing position is shifted by one pixel for convenience, the predetermined pixel indicating the amount of deviation of the landing position is set in a range that does not give a sense of incongruity to the image quality.
Although the ink droplets I1 to I4 land on the normal landing position, the ink droplet I5 deviates from the normal landing position by one pixel. This positional deviation of the landing position is caused by the increase in the viscosity of the ink in the nozzle and the decrease in the ejection speed.
FIG. 4 is a graph showing the relationship between the ejection stop time and the ejection rate reduction rate for each of the two types of ink. As shown in FIG. 4, the rate of decrease in the ejection speed relative to the ejection speed when normal ink with no increased viscosity is ejected is the elapsed time when ink is waiting in the nozzle, that is, the ejection stop time is longer. The bigger it gets, the bigger it gets. If the discharge speed reduction rate increases, the positional deviation of the landing position also increases accordingly, so the amount of positional deviation must be suppressed to at least the discharge speed reduction rate that fits within the predetermined pixel, and the discharge speed reduction The discharge stop time as a rate is set to the predetermined time described above. For example, in the case of FIG. 4, if the discharge rate reduction rate must be within 10%, the predetermined time is 11 to 12 seconds for ink A, and the predetermined time is 45 to 46 seconds for ink B.

  In addition, the predetermined number of times that is the number of times of ejection at the time of idle ejection is when the ejection stop time is set to the predetermined time from the relationship between the ejection stop time and the number of times of ejection that returns to the ejection speed when normal ink is ejected. This is the number of discharges determined by FIG. 5 is a graph showing the relationship between the ejection stop time for each of the two types of ink and the number of ejections returned to the ejection speed when normal ink is ejected. As shown in FIG. 5, the longer the discharge stop time, the greater the number of discharges until the discharge speed is restored. For example, in the case of FIG. 5, as described above, about 450 times is the predetermined number for the ink A that has passed the predetermined time (11 to 12 seconds), and for the ink B that has passed the predetermined time (45 to 46 seconds). About 350 times is the predetermined number.

The predetermined time and the predetermined number of times are obtained by various experiments and simulations. These values also vary depending on the interval G from the nozzle surface 2a of the recording head 2 to the recording medium P, as shown in FIG. Further, the predetermined time and the predetermined number of times vary depending on the resolution.
FIG. 7 is a table summarizing how the predetermined time and the predetermined number of inks A change according to the interval G and the resolution. In the table, the numbers in parentheses are the discharge rate reduction rate when one pixel (predetermined pixel) is shifted and the discharge rate at that time. It can be seen that as the resolution becomes finer, the predetermined time and the predetermined number of times decrease, and when the interval G increases, the predetermined number of times and the predetermined number of times decrease.

  A table as shown in FIG. 7 is stored in advance in the ROM of the control unit 10 for each type of ink that can be used in the inkjet recording apparatus 1. Based on the ink information input from the input unit 12 before the image formation, the control unit 10 specifies the ink to be used for image formation from now on, reads the ink table from the ROM, and sets the predetermined time and the predetermined number of times as the image. Register before forming.

  Next, a maintenance method executed in the inkjet recording apparatus 1 of the present embodiment will be described. FIG. 8 is a flowchart showing a flow when the maintenance method is executed. In the ink jet recording apparatus 1, when the ink is not ejected after the power is turned on, the control unit 10 always gives the first drive signal to the pressure generating means 22 of the recording head 2 to slightly vibrate the ink in the nozzles. I am letting.

First, when the ink jet recording apparatus 1 is used for the first time or when the ink is replaced, the type of ink used for future image formation is input from the input unit 12 to the control unit 10 (step S1).
In step S2, the control unit 10 reads the predetermined time and the predetermined number of times from the table in the ROM based on the input ink type, and sets to apply the predetermined time and the predetermined number of times to future maintenance.

  In step S <b> 3, the control unit 10 controls the maintenance unit 8 and the recording head 2 to perform maintenance of the recording head 2. Specifically, the control unit 10 controls the suction device 81 to suck ink from the recording head 2. Thereafter, the control unit 10 gives a second drive signal to the pressure generating unit 22 of the recording head 2 and causes the ink receiver 83 to eject the ink idly a predetermined number of times. Then, the control unit 10 controls the blade 82 to rub the nozzle surface 2a of the recording head 2 and wipe the ink attached to the nozzle surface 2a.

In step S <b> 4, the control unit 10 controls the time measurement unit 13 to measure the time after the maintenance by the maintenance unit 8 is performed.
In step S <b> 5, the control unit 10 controls the carriage driving mechanism 31, the motor 61 of the transport device 6, and the pressure generation unit 22 of the recording head 2 to form an image on the recording medium P by cooperating them.

  In step S6, the control unit 10 determines whether or not the measurement time of the time measurement unit 13 is less than the predetermined time. If the measurement time is less than the predetermined time, the control unit 10 proceeds to step S5 and continues image formation as it is. When it is more than time, it transfers to step S7.

  In step S7, the control part 10 resets the measurement time of the time measurement part 13, and transfers to step S3. As a result, the maintenance is performed again on the recording head 2 after a predetermined time has elapsed since the previous maintenance.

As described above, according to the present embodiment, when the measurement time of the time measuring unit 13 reaches a predetermined time, the maintenance unit 8 performs maintenance of the recording head 2 and applies the second drive signal to the pressure generating unit 22. Since the ink in the nozzles is ejected a predetermined number of times, maintenance can be performed within a range that does not give a sense of incongruity to the image quality. Therefore, the number of maintenance can be reduced as much as possible, and ink discharged by maintenance can be suppressed.
Note that the present invention is not limited to the above embodiment, and can be modified as appropriate.
For example, in the ink jet recording apparatus 1 described in FIG. 1, the outer end of the recording area Y in which the carriage 3 is movable and the transport apparatus 6 is provided is the maintenance area Z. The maintenance unit 8 can be provided so as to perform idle ejection at the end of the recording medium P, and can be provided at both ends as well as one side of the recording medium P. In this case, the end of the recording medium P that has received the ink ejected idle is cut off to obtain a desired recorded matter.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Recording head 2a Nozzle surface 2r Ink flow path 2t Ink tank 3 Carriage 4 Guide rail 6 Conveying device 8 Maintenance part 9 Moisturizing part 10 Control part 12 Input part 13 Time measuring part 22 Pressure generating means 31 Carriage drive mechanism 61 Motor 81 Suction device 81a Suction cap 81b Ink communication tube 81c Suction pump 81d Waste ink tank 82 Blade 83 Ink receiver 91 Moisturizing cap G Interval P Recording medium

Claims (2)

A recording head for ejecting ink from the nozzles;
Pressure generating means for discharging the ink in the nozzle by compressing the nozzle;
A maintenance unit for performing maintenance of the recording head;
A time measuring unit for measuring the time after the maintenance by the maintenance unit is performed;
A control unit for controlling the maintenance unit and the pressure generating means,
The control unit gives a first drive signal in a range where ink is not ejected to the pressure generating means during standby, and causes the ink in the nozzle to vibrate,
When the measurement time of the time measuring unit reaches a predetermined time, the maintenance unit performs maintenance of the recording head, and applies a second drive signal in a range in which ink is ejected to the pressure generating unit to provide ink in the nozzle Is discharged a predetermined number of times,
The predetermined time is a relationship between a discharge stop time that is an elapsed time in a state where ink is waiting in the nozzle and a discharge speed decrease rate that is a decrease rate with respect to a discharge speed when normal ink is discharged. It is a time obtained from the ejection speed reduction rate at which the ink landing position is shifted by a predetermined pixel from the normal landing position,
The predetermined number of times is the number of discharges obtained when the discharge stop time is set to the predetermined time from the relationship between the discharge stop time and the number of discharges that are returned to the discharge speed when normal ink is discharged. An ink jet recording apparatus. A recording head having nozzles for ejecting ink;
Pressure generating means for discharging the ink in the nozzle by compressing the nozzle;
A maintenance unit for performing maintenance of the recording head;
A maintenance method for an ink jet recording apparatus, comprising: a time measuring unit that measures time since maintenance by the maintenance unit is performed;
At the time of standby, the pressure generating means is given a first drive signal in a range where ink is not ejected, and the ink in the nozzle is slightly vibrated,
When the measurement time of the time measuring unit reaches a predetermined time, the maintenance unit performs maintenance of the recording head, and applies a second drive signal in a range in which ink is ejected to the pressure generating unit to provide ink in the nozzle Is discharged a predetermined number of times,
The predetermined time is a relationship between a discharge stop time that is an elapsed time in a state where ink is waiting in the nozzle and a discharge speed decrease rate that is a decrease rate with respect to a discharge speed when normal ink is discharged. It is a time obtained from the ejection speed reduction rate at which the ink landing position is shifted by a predetermined pixel from the normal landing position,
The predetermined number of times is the number of discharges obtained when the discharge stop time is set to the predetermined time from the relationship between the discharge stop time and the number of discharges that are returned to the discharge speed when normal ink is discharged. A maintenance method for an ink jet recording apparatus.

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