JP2003127418A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer capable of stably discharging ink by making a pressure in a supply path an optimum value. SOLUTION: The ink jet printer is provided with a recording head for discharging the high-viscosity ink which becomes low in the viscosity in accordance with a temperature rise, an ink tank for storing the high-viscosity ink, the supply path for supplying the high-viscosity ink from the ink tank to the recording head, a pressure detecting means for detecting the pressure of the inside of the supply path or the inside of the recording head, a pressure changing means for changing the pressure of the inside of the supply path, and a pressure control means for controlling the pressure changing means on the basis of the detected result of the pressure detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer that uses high viscosity ink as a recording liquid.

[0002]

2. Description of the Related Art Some conventional inkjet printers supply ink to a recording head from an ink tank containing ink via a supply path. Further, when a high viscosity ink is used as the recording liquid, there is an advantage that a printed image is less likely to bleed and clear printing can be performed.

[0003]

However, when high-viscosity ink is used in the ink jet printer having the above-mentioned structure, the high viscosity ink causes high pressure loss due to the flow path resistance in the supply passage, resulting in high viscosity ink. There is a risk that ink cannot be stably supplied from the ink tank to the recording head, and ink ejection from the recording head becomes unstable.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet printer which makes the pressure in the supply passage an optimum value and enables stable ink ejection.

[0005]

According to another aspect of the present invention, there is provided an ink jet printer in which a recording head for ejecting a high-viscosity ink whose viscosity is lowered with an increase in temperature in a low-viscosity state and a high-viscosity ink are stored. Ink tank, a supply path for supplying high-viscosity ink from the ink tank to the recording head, pressure detection means for detecting pressure inside the supply path or inside the recording head, and pressure inside the supply path And a pressure control means for controlling the voltage transforming means based on the detection result of the pressure sensing means.

According to the first aspect of the present invention, the pressure control means controls the transformer means based on the detection result of the pressure detection means, so that the pressure inside the supply passage is always controlled to a value required for stable discharge. be able to. That is, even if high-viscosity ink is used, pressure loss does not occur in the supply passage, stable supply from the ink tank to the recording head can be performed, and stable ink ejection can be performed.

The high-viscosity ink is preferably a liquid having a viscosity at 30 ° C. of 50 to 3000 mPa · s. It is more preferably 50 to 1000 mPa · s, and even more preferably 100 to 500 mPa · s. At 50 mPa · s or less, bleeding is likely to occur, and clear printing cannot be performed. At 3000 mPa · s or higher, the smoothness of the image quality is lost. Furthermore, the viscosity at 60 ° C is 3 to
It is preferably a liquid of 30 mPa · s. 3 mPa
・ If it is less than s, problems may occur in high-speed injection.
If it exceeds 30 mPa · s, the injection property may be deteriorated. Further, particularly when ejected from a recording head including a piezo element, a liquid having a viscosity of 3 to 30 mPa · s is preferable.

According to a second aspect of the present invention, in the ink jet printer according to the first aspect, the pressure detecting means is
It is characterized in that it is provided in a portion of the supply path in the vicinity of the recording head or in the recording head.

According to the second aspect of the present invention, the pressure detecting means is provided in a portion of the supply path near the recording head or in the recording head. The pressure can be detected. In particular, when the high-viscosity ink is ejected, if the inside of the print head is in a negative pressure state close to 0, the high-viscosity ink can be stably ejected, so that the high-viscosity ink is detected in the vicinity of the print head or in the print head. By controlling the pressure-changing means based on the applied pressure, the inside of the recording head can be easily maintained in a negative pressure state close to 0, and more stable supply of high-viscosity ink can be achieved. Here, the vicinity of the recording head in the supply path is a portion showing a pressure substantially equal to the pressure in the recording head,
Preferably, it is a portion where the pressure inside the recording head becomes the same (for example, a portion where the recording head and the supply path are connected).

The invention according to claim 3 is the invention according to claim 1 or 2.
In the inkjet printer described in the paragraph 1, the high-viscosity ink includes a high-viscosity UV ink that is cured by being irradiated with ultraviolet rays.

According to the third aspect of the invention, the high-viscosity ink is cured by UV (Ultr)
aViolet) ink is included, the same effect as the invention according to claim 1 or 2 can be obtained even when UV ink is used. In this way, printing is UV
When the ink is used, the UV ink is cured by being irradiated with ultraviolet rays after printing, so that the printed image cannot be easily erased for a long period of time, and the quality of the printed image by the inkjet printer can be improved. Further, when the high-viscosity UV ink is obtained by adding a thickening agent to the UV ink, the recording medium has a good ink absorbability (for example, paper).
Alternatively, printing can be performed even on a recording medium having no ink absorption or a recording medium having low ink absorption.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings of FIGS.

The ink jet printer 1 illustrated in the first embodiment has a lower viscosity as the temperature rises,
High-viscosity UV ink (hereinafter referred to as ink) that is cured by being irradiated with ultraviolet rays is ejected onto a recording medium to perform printing. As shown in FIG. 1, the main configuration of the ink jet printer 1 includes a conveyance unit (not shown) that conveys a sheet-shaped recording medium 2 to the front during printing, and a state in which the ink on the recording medium 2 has a low viscosity. A recording head 3 for ejecting, a carriage 4 carrying the recording head 3 for each of a plurality of colors, an ink tank 9 for storing ink to be supplied to the recording head 3, and the recording head 3 from the ink tank 9.
A supply path 11 for supplying ink to the recording head 3
Maintenance unit 5 for carrying out maintenance, a guide rail 6 for guiding the carriage 4 along the horizontal direction (arrow A) at the time of printing or maintenance, a home position 7 serving as a waiting place for the carriage 4, and each of these parts. And a control unit 30 (FIG. 2) that controls the above.

At the time of printing, the conveying means conveys the recording medium 2 on the print area C at the same timing as the operation of the carriage 4, and the recording medium 2 is moved downward from the print area C (at the end of printing). It is conveyed toward the arrow B).

The recording head 3 has a plurality of ejection openings for ejecting ink, a manifold for guiding the ink to each ejection opening, and heating for lowering the viscosity of the ink for stable ejection of the ink. And vessels are provided. Normally, if the inside of the manifold has a negative pressure close to 0, it is possible to eject ink stably. The recording head 3 is a type of ink used in the inkjet printer 1 (Y: yellow, LY: light yellow,
M: Magenta, LM: Light Magenta, C: Cyan, L
C: light cyan, K: black, LK: light black).

The carriage 4 repeats the reciprocating movement in the horizontal direction (arrow A) by the guide rail 6,
The recording head 3 is moved along the print surface of the recording medium 2 in the print area C. In order to cure the ink ejected from the recording head 3, the side portion of the carriage 4 is
A UV light source 16 that radiates ultraviolet rays is provided.

The ink tank 9 is, for example, an ink cartridge that is replaceably provided, and the ink tank remaining amount sensor 9 for detecting the ink remaining amount in the ink tank 9.
a (FIG. 2). A plurality of ink tanks 9 are provided in accordance with each color of ink stored in each recording head 3. Although the ink tank 9 is divided for each color in this embodiment, each main tank 9
May be integrated.

The ink tank remaining amount sensor 9a may be of any type as long as it detects the remaining amount of ink in the ink tank 9, and for example, the reflected light is detected by an optical sensor by irradiating the liquid surface of the ink with light. Then, the one that detects the remaining amount of ink by its response speed and that electricity is applied to the ink,
There are ones that detect the remaining amount of ink by the conductive state, ones that detect the remaining amount of ink by the weight of the tank, and the like.

The supply path 11 connects the respective ink tanks 9 and the respective recording heads 3 to each other so that the inks can be supplied from the main tank 9 to the recording heads 3 for each color. And this supply path 11 is
It is formed of a flexible member so as to correspond to the movement of the recording head 3. In each of the supply paths 11, a pressure change pump (transformer means) 10 that changes the pressure inside the supply path 11 to supply ink from the ink tank 9 to the recording head 3, and a vicinity of the recording head 3 in the supply path 11. And a pressure sensor (pressure detection means) 12 (FIG. 2) for detecting the pressure inside the supply path 11.

As shown in FIG. 1, the maintenance unit 5 covers a nozzle surface of the recording head 3 having a discharge port, and a suction cap 13 for sucking ink from the discharge port.
It is provided with a blade portion 14 for wiping off the ink remaining on the nozzle surface of the recording head 3 after the suction of the ink by the suction cap 13 and a blade cleaner portion (not shown) for cleaning the blade portion.

The home position 7 is provided at one end of the path along which the carriage 4 reciprocates. Moisturizing caps 8 for moisturizing the nozzle surface of the recording head 3 are provided at the home position 7 in the same number as the recording head 3, and the nozzle surface of the recording head 3 is covered and sealed while the carriage 4 is on standby. ing.

As shown in FIG. 2, the control unit 30 includes an interface 31, a ROM (Read Only Memory) 32, and an R.
AM (Random Access Memory) 33, CPU (Central
Processing Unit) 34 and the like, and controls various devices connected to the interface 31 in accordance with control programs and control data written in the ROM 32.

The interface 31 includes a display section 17 for displaying an error and a state of each section, an ink tank remaining amount sensor 9a, a transformer pump 10, and a pressure sensor 12.
Etc. are electrically connected.

Various data for ink supply, various control programs and control data relating to the operation of each section of the ink jet printer, etc. are written in the ROM 32. The various data in the ink supply include the ink remaining amount (predetermined amount a) in the ink tank 9 that serves as a reference for the replacement time of the ink tank 9 and the ink stored in the ink tank 9 when it is supplied to the recording head 3. It is the pressure (predetermined pressure p) in the supply path 11 that can maintain the negative pressure inside the manifold of the recording head 3 close to zero.

The RAM 33 can store a plurality of data input only while power is supplied, and a storage area for storing various data such as image data to be printed and a CPU.
A work area by 34 is provided.

The CPU 34 reads out a program designated from the various programs stored in the ROM 32 from the R program.
It is developed in the work area in the AM 33, and various processes according to the program are executed according to the input signal from each sensor.

The control unit 30 controls the entire operation of the ink jet printer 1. Here, the control procedure performed when the ink is supplied from the ink tank 9 to the recording head 3 will be described with reference to FIG. Explain.

When printing is started, the variable pressure pump 10 is operated to start supplying ink from the ink tank 9 to the recording head 3, and the process proceeds to step S1. Step S1
Then, the ink remaining amount of the ink tank 9 is detected based on the detection result of the ink tank remaining amount sensor 9a, and if the ink remaining amount of any one of the main tanks 9 is less than the predetermined amount a, the process proceeds to step S2. To do. On the other hand, if the ink residual amounts of all the main tanks 9 are equal to or larger than the predetermined amount a, the process proceeds to step S3.

In step S2, the printing is stopped, and the display unit 17 is caused to display that the ink tank 9 having a predetermined amount a or less is replaced or the ink tank 9 is replenished with ink. Then, after the replacement or the replenishment, if the ink amount in the ink tank 9 becomes a printable value or more (preferably, a value that fills the ink tank), printing is restarted.

In step S3, the pressure in the supply passage 11 is detected based on the detection result of the pressure sensor 12. When the pressure in the supply passage 11 is less than the predetermined pressure p,
Control goes to step S4. On the other hand, if the pressure in the supply passage 11 is equal to or higher than the predetermined pressure p, the process proceeds to step S6.

In step S4, the output state of the variable pressure pump 10 is controlled so as to increase the pressure inside the supply passage 11, and the process proceeds to step S5.

In step S5, the pressure in the supply passage 11 is detected based on the detection result of the pressure sensor 12. When the pressure in the supply passage 11 is less than the predetermined pressure p,
Control goes to step S4. On the other hand, if the pressure in the supply passage 11 is equal to or higher than the predetermined pressure p, the process proceeds to step S6.

In step S6, the variable pressure pump 1 is operated so as to maintain the pressure in the supply passage 11 which is equal to or higher than the predetermined pressure p.
The output state of 0 is controlled, and the process proceeds to step S7.

In step S7, the current printing stage is detected, and if printing is in the middle, the process proceeds to step S1. When the printing is completed, the variable pressure pump 10 is stopped to stop the ink supply, and the operation related to the printing of each unit is stopped and ended.

As described above, according to the ink jet printer 1 of the present embodiment, the control section (pressure control means) 30
However, since the variable pressure pump 10 is controlled based on the detection result of the pressure sensor 12, the pressure inside the supply passage 11 can be constantly controlled to a value necessary for stable discharge. That is, even if high-viscosity ink is used, pressure loss does not occur in the supply passage 11, stable supply from the ink tank 9 to the recording head 3 can be performed, and stable ink ejection can be performed. .

Further, since the pressure sensor 12 is provided in the portion of the supply path near the recording head 3, the pressure in the vicinity of the recording head 3 can be detected. In particular, when ejecting high-viscosity ink, the inside of the recording head 3 (for example,
If the discharge port, manifold, etc.) maintains a negative pressure close to 0, high-viscosity ink can be stably ejected, so that the pressure detected in the portion of the supply path near the recording head is used as a basis. If the variable pressure pump 10 is controlled as, it is easy to maintain the inside of the recording head at a negative pressure state close to 0,
It is possible to more stably supply high viscosity ink.

Further, since the high viscosity UV ink is used as the recording liquid in the ink jet printer of the present embodiment, the high viscosity UV ink is cured by irradiating it with ultraviolet rays after printing, and the printed image is printed for a long period of time. It can be made hard to disappear, and can exhibit excellent weather resistance even when the printed matter is placed outdoors. That is, it is possible to improve the quality of the printed image by the inkjet printer. Furthermore, if the high-viscosity UV ink is used, the recording medium does not have to have good ink absorbability (for example, paper), but does not have ink absorbability or has low ink absorbability. Printing can be performed.
Here, a recording medium having no ink absorbability or a recording medium having low ink absorbability means a recording medium formed of a material having no ink absorbability or a material having low ink absorbability, or a material having no ink absorbability. For example, it is a recording medium having a surface layer (printing layer) made of a material having low ink absorbability. Examples of the material having no ink absorptivity or the material having a low ink absorptivity include various plastics and metals.

In this embodiment, the high-viscosity UV ink is described as an example of the recording liquid, but the recording liquid to be used is not limited to this, and even if it is UV ink, It may be a viscous ink.

Further, the ink tank may be divided into a main tank and a sub tank. In this case, a transformer or a pressure sensor may be provided in a supply path for supplying ink from the main tank to the sub tank. Good. By doing so, it becomes possible to stably supply the ink from the main tank to the sub tank. Further, in the present embodiment, the pressure sensor is provided in the portion of the supply path 11 near the recording head 3, but it is provided in a place where the pressure inside the recording head 3 (for example, the ejection port or the manifold) can be measured. Alternatively, a pressure sensor may be provided. With such a configuration, the pressure inside the print head 3 can be directly detected, and the inside of the print head 3 can be maintained in a negative pressure state closer to zero.

It should be understood that the embodiments disclosed this time are exemplifications in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0041]

According to the first aspect of the present invention, the pressure inside the supply passage can be constantly controlled to a value required for stable discharge. That is, even if high-viscosity ink is used, pressure loss does not occur in the supply passage, stable supply from the ink tank to the recording head can be performed, and stable ink ejection can be performed. According to the second aspect of the invention, it is possible to detect the pressure in the vicinity of the recording head in the supply path or inside the recording head. In particular, if the inside of the recording head is in a negative pressure close to 0 when ejecting high-viscosity ink,
Since the high-viscosity ink can be stably ejected, if the transforming means is controlled based on the pressure detected in the vicinity of the recording head of the supply path or the recording head, the inside of the recording head
It is easy to maintain a negative pressure state close to 0, and more stable supply of high-viscosity ink becomes possible.

According to the invention described in claim 3, even when the UV ink is used, the same effect as that of the invention described in claim 1 or 2 can be obtained. As described above, when the UV ink is used for printing, the UV ink is cured by irradiating with ultraviolet rays after the printing, so that the printed image cannot be easily erased for a long time, and the quality of the printed image by the inkjet printer can be improved. it can. Furthermore, U
In the case of the high-viscosity UV ink in which the thickening agent is added to the V ink, the recording medium is a recording medium having good ink absorption (for example,
It is possible to print even with a recording medium having no ink absorption property or a recording medium having low ink absorption property, even if it is not paper).

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of an inkjet printer according to a first embodiment of the present invention.

FIG. 2 is a main control block diagram of a control unit included in the inkjet printer of FIG.

3 is a flowchart showing a procedure of supplying ink from an ink tank provided in the inkjet printer of FIG. 1 to a recording head.

[Explanation of symbols]

1 inkjet printer 3 recording head 9 ink tank 10 Transformer pump (transformer means) 11 supply path 12 Pressure sensor (pressure detection means) 30 control unit (pressure control means)

Claims (3)

[Claims] 1. A recording head for ejecting a high-viscosity ink whose viscosity decreases with increasing temperature in a reduced viscosity state, an ink tank for storing the high-viscosity ink, and a high viscosity from the ink tank to the recording head. A supply path for supplying ink, a pressure detection means for detecting the pressure inside the supply path or the inside of the recording head, a transformer means for changing the pressure inside the supply path, and a detection result of the pressure detection means. An ink jet printer comprising: a pressure control unit that controls the transformation unit. 2. The ink jet printer according to claim 1, wherein the pressure detecting means is provided in a portion of the supply path near the recording head or in the recording head. 3. The inkjet printer according to claim 1, wherein the high-viscosity ink includes UV ink that is cured by being irradiated with ultraviolet rays.