JP3428881B2 - Inkjet printer - Google Patents

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.

[0002]

2. Description of the Related Art A typical example of making a large poster or comp is a screen printing method in which a silk screen plate is used to directly print on paper. In this method, first of all, for the original image to be printed, a silk screen plate for each color used in the original image is attached to the screen printing device, and the ink is directly transferred to the paper through the mesh of the silk screen plate. Recording is done.

However, this screen printing method requires a great deal of man-hours and days to prepare the silk screen printing plate in advance, and the ink composition of each color
There is a problem that work such as alignment of the silk screen plate for each color is required. In addition, the device is large,
In addition to increasing the size and installation space in proportion to the number of colors used, there is also the problem that a storage space for silk screen plates is also required. Further, since such a printing method can be manufactured at a very low cost in mass production, it is very expensive in a production of a small lot poster such as a presentation or a single event.

Therefore, an ink jet recording method for directly recording an image on a recording medium has been proposed. This inkjet recording method is a method in which a minute ink is ejected from a discharge port provided in an inkjet recording unit (inkjet recording head) onto a recording medium such as paper to record an image on the recording medium. According to the method, the screen plate, which was necessary in the conventional screen printing, becomes unnecessary. As a result, the process and the number of days until the image is formed on the paper are significantly shortened, and the device can be downsized.
In addition, image information for printing can also be saved on a medium such as tape, flexible disk, optical disk, etc. Therefore, it has excellent storability and storability of image information. Furthermore, color arrangement change, layout change, enlargement, reduction of the original image is possible. There is also an advantage that processing such as can be easily performed.

Among the ink jet recording apparatuses, in a serial type recording apparatus which employs a serial scan system in which main scanning is performed in a direction intersecting a recording material (recording medium) conveying direction (sub-scanning direction), the recording material is printed along the recording material. An image is recorded by a recording unit mounted on a carriage that moves in the main scanning direction, and after one line of recording is completed (outward side), a predetermined amount of paper feed (pitch feed) is performed in the sub scan direction. Furthermore,
The entire recording material is recorded by repeating the operation of collectively recording the next line (return side). In the ink jet recording apparatus using the line type recording means in which a large number of ejection openings are arranged in the width direction of the recording material as described above, the recording speed can be further increased.

The general advantages of ink jet recording are that it is non-contact with the printing (recording) medium, so it is excellent in quietness, high printing speed, high density printing is possible, and colorization is possible. Easy,
The device is small in size.

[0007]

However, in the ink jet recording apparatus, the distance between the cloth and the recording head must be set larger than that of a general computer printer. In an ordinary printer, paper is usually used as a recording material. However, in printing, there are cloths having various textures, and thus the distance between the cloth and the recording head has to be large.

Therefore, the density difference between the forward side and the backward side of the recording head scanning, which is a problem peculiar to the on-demand type ink jet recording apparatus, which is generated by the secondary droplets generated when the main droplets are ejected, is one of the image deteriorations. It is a cause.

FIG. 1 is a schematic view of a droplet discharge process in bubble jet type ink jet recording. In FIG. 1, (a) shows a state where the ink 1500 is filled in the nozzle 1500. In (b), when energy is applied to the electrothermal converter 1520 for an extremely short time, the ink near the electrothermal converter 1520 is rapidly heated, and minute bubbles are generated. (C) The ink 1510 is rapidly vaporized, and micro bubbles grow. (D) The bubble expands to the maximum and the ink 1510 is pushed out. (E) The bubbles are cooled by the ink 1510 and rapidly contracted, and the extruded ink 1510 becomes a droplet. (F) Ink droplets are pushed out and fly in the arrow direction. (G) The tail portion of the ink droplet becomes a droplet shape 1530 due to surface tension. Not only in bubble jet recording, but in wide range of ink jet recording of droplet discharge, the tail portion of the main droplet discharge becomes a droplet due to the surface tension of the ink itself, and a secondary ink separate from the main droplet originally necessary for printing. Drop (hereinafter called satellite)
Or mist-like ink droplets (hereinafter referred to as mist) are generated.

If the satellite or mist adheres around the ink discharge port of the recording head, the flying of the ink is hindered and the landing position is displaced, or the ink droplet is broken and becomes a splash. If the ink ejection port is blocked by satellite or mist, the phenomenon of non-ejection occurs. Therefore, in order to prevent non-ejection, the ink ejection port must be appropriately wiped. The reason is that if the phenomenon as described above occurs, the printing quality is degraded and the value is lost.

FIG. 2 shows a schematic view of the print head used in the present invention. The head 2000 has a plurality of nozzles arranged in a line to form a nozzle row 2030 for one color. The head unit 600 is formed by further stacking the heads. In the head 2000, a silicon-based sealant 2010 is used to seal a key portion in order to prevent ink from leaking out of the head and entering from the outside.

Now, when attempting to wipe the face surface 2020 of the head unit 600 with a wiper (not shown) in a direction orthogonal to the nozzle row, since the head to be wiped is formed on the same plane, the wiper does not touch the face surface. As it passes, it contacts the surface of the sealant 2010. When the wiper passes the surface of the sealant 2010, a stick-slip phenomenon occurs and the wiper abnormally vibrates, causing the scraped ink droplets to be scattered around. The ink droplets scattered at this time adhere to the recording paper and extremely deteriorate the printing quality. The scattered ink droplets not only stain the surroundings, but also reach around the wiped head and adhere to the nozzles, which causes defective printing.

In order to avoid contact with the sealant, the stick-slip phenomenon can be avoided by using a wiper having a width shorter than that of the parallel sealant and wiping in the direction parallel to the nozzle row. However, the probability that dust and ink adhered to the nozzle will be much higher than the former,
Printing defects are likely to occur. Therefore, a means for wiping in a direction perpendicular to the nozzle while avoiding the sealant is desired. Further, in recent years, the speed of printing has been increased, and the head carriage unit is moving at high speed. Moving the carriage at an extremely low speed suitable for wiping is very difficult.

[0014]

SUMMARY OF THE INVENTION The present invention is an ink jet printer in which a plurality of nozzle rows for ejecting ink are arranged in a line and recording is performed using a recording head having a sealant in parallel on the face surface. And a plurality of wipers for wiping the face surface in a direction orthogonal to the nozzle row by a turning motion, and when wiping,
The recording head moves in the same direction as the moving direction of the wiper at a speed lower than the moving speed of the tip of the wiper, and the wiper is on the opposite side of the moving direction of the recording head and from the inside of the sealant to the face surface. And then comes out of the face surface without coming into contact with the sealant.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 3 is a schematic side sectional view showing a schematic configuration of a printing apparatus as an example of the image forming apparatus (inkjet printer) of the present invention. Here, 1 is a recording paper as a printing medium, which is unwound in accordance with the rotation of the unwinding roller 310 driven by a motor (not shown), and reaches the conveying means 200 via the intermediate rollers 320 and 330. The transport unit 200 is provided at a position facing the printer unit 100, and after being transported in the substantially horizontal direction by the transport unit 200, the feed roller 14 and the intermediate rollers 520, 5 are connected.
It is wound by the winding roller 500 through 30, 540.

FIG. 4 is an overall schematic view of this embodiment. Here, inside the print frame 1050, a pair of guide rails 1020 parallel to the main scanning direction orthogonal to the conveyance direction of the recording paper 1 are arranged. This guide rail 1020
A head carriage 1010 is provided above the ball bearing 1011 so that the head carriage 1010 can reciprocate in the main scanning direction. The head carriage 1010 is a printer frame 1050.
It is driven via a drive belt (not shown) by a drive motor (not shown) fixed to one side wall. A recording head unit (not shown) for forming an image on the recording paper 1 is attached to the inner lower surface of the head carriage 1010.

The recording head unit is a set of a plurality of recording heads 1100 having a large number of ink ejection openings arranged in a predetermined direction and held in a direction different from the predetermined direction, and in this example, this recording head is used. A set of 1100 (hereinafter may be simply referred to as a head) is held in two stages in the transport direction. The recording heads 1100 of each set are provided with a plurality of sets corresponding to the inks of different colors, respectively, thereby enabling color printing. Recording head 110
0 indicates a plurality of ink storage tank units 1 as needed.
Each relay tube 10 which is an ink supply path from 300
Various inks are supplied via 30. The details of the ink supply path will be described later,
Since these ink supply paths move in the same manner as the head carriage 1010, they are arranged in a caterpillar (not shown) for ease of movement and prevention of damage.

The tube used as the ink supply path is preferably a rubber type such as fluororubber, isopropylene or silicone rubber, a fluororesin type such as Teflon or a plastic type such as polyolefin, polyethylene or vinyl chloride, but is not limited thereto. It is not something that will be done. A capping unit 1200 is provided below the home position of the recording head unit. The capping unit 1200 is in contact with the ejection port surface of each recording head 1100 when not printing, and each recording head 1100 is capped by the capping unit 1 when not printing.
Move to the home position, which is a position facing 200, and perform capping. When the recording head is left in the air for a long time, the ink in the nozzle evaporates and the viscosity increases, and the ejection becomes unstable. In order to prevent this, during non-printing, the nozzle part is shut off from the outside air and sealed (capping). Inside the cap portion, there is a liquid absorbing material that is kept wet with ink, and the inside of the cap is kept at a high degree of wetting to minimize the thickening of the ink.

FIG. 5 is a diagram schematically showing an ink supply path suitable for the present invention. Note that FIG. 5 shows an ink supply path, which will be described later, for one print head, and the ink supply path is actually provided for only the print heads. In the ink storage unit 1300, 1310 is a main tank for storing a large amount of ink, 1320 is a sub-tank for stabilizing the head difference with the recording head 1100 to stabilize ejection, and 340 is a main tank. It is a pump for supplying the ink in the tank 1310 to the sub tank 1320. Further, each recording head is connected by an ink supply tube 1030. The ink is normally supplied to the recording head 1100 by the amount of the ink ejected from the recording head 1100 by a capillary action. In addition, the sub tank 13
The ink may be supplied to the ink tank 20 by warning the user with a signal from the sensor 350 provided in the sub tank and prompting the ink supply.

(Embodiment 1) FIG. 6 is a schematic perspective view of a main part of an ink jet printer according to Embodiment 1 of the present invention. Not only for bubble jet recording, but also widely for ink jet recording droplet ejection, the tail portion at the time of main liquid ejection becomes a droplet due to the surface tension of the ink itself, and in addition to the main droplet originally required for printing, a secondary ink Droplets (hereinafter referred to as satellites) and mist-like ink droplets (hereinafter referred to as mists) are generated. If the satellite or mist adheres to the periphery of the ink ejection port of the recording head, the flight of the ink is hindered and the landing position is displaced, or the ink droplet is broken and becomes a splash. If the ink ejection port is blocked by satellite or mist, the phenomenon of non-ejection occurs.

When such a phenomenon occurs, the printing quality is degraded and the value is lost. Therefore, in the bubble jet printer, the wiping means of the print head is usually provided near the capping means. As conditions for wiping a bubble jet, a polyurethane-based wiping wiper, a thickness of 1 mm or less (hereinafter simply referred to as a wiper), a head overlap amount of 2.0 mm or less, a free length of the wiper of 20 mm or less, a head-wiper relative Experiments have shown that suitable wiping can be performed by setting the speed to 100 mm / sec or less.

Wiping is established by moving the head and the wiper relative to each other. In conventional printers, there are a type in which the wiper is fixed and the head is moved horizontally, and a type in which the head is fixed and the wiper is moved. In the wiping operation in the present invention, a plurality of wipers (2050, 2060, 2070) provided are configured like a water wheel, and wiping is performed by a turning motion. Further, the head moves in the same direction as the wiper moving direction, and the moving speed is slower than the wiper moving speed. The speed obtained by subtracting the moving speed of the head from the tip speed of the wiper is set as a relative speed suitable for wiping.

The actual wiping operation will be described with reference to FIG. The wiper wipes from the end head in the head traveling direction.

(A) shows the positional relationship between the head unit 600 and the wiper unit 700 at the start of wiping. The first wiper 2050 enters from the side opposite to the head advancing direction around the nozzle row 2030. At this time, the first wiper 2050 penetrates from the inside of the head sealant 2010, so the first wiper 2050 and the sealant 201
0 does not touch.

(B) The head unit advances in the direction of arrow A in the drawing. The wiper unit 700 also rotates in the direction of arrow B in conjunction with the movement of the head unit 600. At this time, the moving speed of the head unit 600 is 6.67 mm /
sec, the tip turning speed of the first wiper 2050 is 11.
If it is 67 mm / sec, the first wiper faces the vertical direction after 0.6 sec, and reaches the center of the nozzle row 2030 at that time. The amount of overlap between the first wiper 2050 and the head unit 600 at that time matches the preferable wiping condition. Furthermore, the first wiper 2
The numerical value obtained by subtracting the moving speed of the head unit 600 from the tip turning speed of 050 also meets the preferable wiping condition.

Wiping is performed in such a manner that ink droplets existing between the first wiper 2050 and the head face surface 2020 are dragged by the first wiper 2050. The face is coated with a water-repellent film of ink, and its wettability is very poor. On the other hand, the first wiper 2050
Has a higher wettability than the water-repellent film on the face surface, so that the ink is attached to the first wiper 2050 when the first wiper 2050 passes over the water-repellent film.

(C) The relative movement between the head unit 600 and the first wiper 2050 further progresses, and 1 second after the start of wiping, the wiping by the first wiper 2050 ends, and the nozzle row 2030 to the first wiper 205.
0 exits. At this time, since the first wiper 2050 comes off from the inside of the head sealant 2010, the first wiper 2050 and the sealant 2010 do not come into contact with each other.

(D) After 1.9 seconds from the start of wiping, the relative movement advances to the position where the second wiper 2060 starts wiping the central head. The wiping start position at this time is the same as in (a) above.
Inside.

(E) After 3.8 seconds, the wiping of the central head is completed, and the third head wiper 2070 reaches the wiping start position of the third head. The wiping start position at this time is the same as in (a) and (d).
It is inside 010.

(F) After 5.7 seconds, wiping of all heads is completed.

(G) During normal printing, the wiper is retracted in order to prevent interference with the head.

According to the present invention, good wiping can be performed without the wiper passing over the head seal agent while maintaining the wiping preferable condition.

Next, the wiper cleaner of the present invention will be described with reference to FIG. (A) First wiper 2050
Wipes the nozzle row.

(B) When the second wiper 2060 finishes wiping, the first wiper 2050 scrapes and contacts the tongue 2100, and scrapes large ink droplets and dust adhering to the first wiper 2050.

(C) The first wiper 2050 that has passed through the scraping tongue 2100 contacts the absorbing roller 2110,
Absorbs fine ink drops on the wiper surface.

(D) When the first wiper 2050 passes through the absorbing roller 2110, the third wiper 2070 contacts the head unit 600. At this time, the absorbing roller 2110 continues to rotate and transfers the ink to the contact roller 2120.

Scraping tongue 2100, absorbing roller 211
If another wiper wipes the head when the wiper is in contact with 0, vibration occurs when the wiper scrapes off the tongue 2100 and the absorbing roller 2110, fluctuations in the wiping speed, and the like. With this, sufficient wiping cannot be performed. Therefore, the scraping tongue 2100 and the absorbing roller 2110 are arranged at positions that do not affect head wiping.

The ink droplets adhering to the scraping tongue 2100 drop by gravity and are collected in a waste ink bottle (not shown). A polypropylene foam or other foam is used for the absorbing roller 2110. The contact roller 2120 is also made of the same foam as that of the absorbing roller 2110, but it is better to improve the absorbing power by further treating with a surfactant or the like. In this case, the absorbing roller 2110 is not subjected to the activator treatment so that ink droplets are caught on the roller surface, while the contact roller 2120 is subjected to the activator treatment so that the ink can be absorbed inside. And always maintain a stable roller surface condition. Since the amount of ink absorbed by the contact roller is very small, it is possible to maintain sufficient absorption capacity by natural drying.

(Second Embodiment) FIG. 9 is a perspective view for explaining the structure of a wiper according to a second embodiment. Here, the bubble jet printer shown above is used, and each of the wipers (2050, 2060, 2070) of the wiping mechanism is a stack of two wipers. Front wiper 2200
Are attached to the rear wiper 2210 at a gap T.

Front wiper 220 when wiping the head
At 0, the rear wiper 2210 wipes the trailing wiper even if the contact with the head is interrupted by the paper dust or the solidified ink on the head and the ink droplets are left unwound. Therefore, stable wiping can be performed. It is possible.

The timing of the entire wiping and the cleaning method of the front wiper 2200 are the same as those in the first embodiment. Wiping is performed by the turning motion of the wiper unit, the head moves in the same direction as the wiper advancing direction, and the moving speed is It is slower than the wiper moving speed. The speed obtained by subtracting the moving speed of the head from the tip speed of the wiper is set as a relative speed suitable for wiping. Wiping is performed while avoiding the sealant on the head.

(Third Embodiment) FIG. 10 is a perspective view for explaining the structure of the wiper of the third embodiment. Here, the bubble jet printer described above is used, and the wiper 2300 is made of a PP (polypropylene) foam. The porosity of the foam is 50% or more, preferably about 80%.

Since the foam comes into contact with the head, it is not preferable to perform activation treatment. Since the foam that has not been subjected to the activation treatment has a very low ink absorbing power, it is desirable to use it with water. The water content is 60% or less, preferably about 45%.

During wiping, since the head and the wiping wiper overlap, the foam is crushed with a certain pressure. At that time, if the water content of the foam is high, pure water will be squeezed out of the foam when the foam comes into contact with the head. When this squeezed pure water enters the head, it may cause discharge failure or swelling, so that the water content must be controlled.

A method of controlling the water content will be described with reference to FIG. Before wiping, the wiper unit 800 is rotated once at the head retracted position. A wiper cleaning unit 900 is arranged below the wiper unit 800. As shown in FIG. 11 a, pure water is introduced into the wiper cleaning unit 900 by an introduction pipe (not shown).
The wiper is successively dipped in pure water as it rotates, and cleaning and hydration are performed. Wiper unit 80
When 0 rotates once, the water content is controlled by performing suction for a predetermined time by the pump 2320 connected to the wiper holder 2310.

As shown in FIG. 11b, during the wiping, the pure water in the wiper cleaning unit 900 is discharged by opening the bubble 2330, and the wiper and the pure water do not come into contact with each other during the wiping operation. . In this way, since wiping is performed with the water-containing foam, stable wiping is always possible. The wiping method is the same as that in the first embodiment, the wiping is performed by the turning motion of the wiper unit 800, the head moves in the same direction as the wiper moving direction, and the moving speed is slower than the wiper moving speed. The speed obtained by subtracting the moving speed of the head from the tip speed of the wiper is set as a relative speed suitable for wiping. Wiping is performed while avoiding the sealant on the head.

(Fourth Embodiment) FIG. 12 is a perspective view for explaining the structure of a wiper according to a fourth embodiment. Wiping wiper 2400 is polyethylene terephthalate (hereinafter PE
The main raw material is T), and the thickness is 0.5 mm or less. PET is more rigid than the polyurethane mentioned above,
Straightness is easy to obtain during processing. Further, it has been confirmed that the effect of scraping off ink droplets solidified on the head surface is also high because of high rigidity. The wiping method and the cleaning method are the same as those in the first embodiment. Wiping is performed by the swiveling motion of the wiper unit, the head moves in the same direction as the wiper moving direction, and the moving speed is slower than the wiper moving speed. is there. The speed obtained by subtracting the moving speed of the head from the tip speed of the wiper is set as a relative speed suitable for wiping. Wiping is performed while avoiding the sealant on the head.

[0048]

According to the present invention, suitable for wiping,
While maintaining the free length of the wiper, the amount of overlap with the head, and the relative speed of the head and wiper, it is possible to avoid the sealant on the head and wipe only where it is needed. As a result, stable wiping is always possible, and the head surface can be maintained under an appropriate ink ejection condition, so that stable ink ejection can provide a beautiful print quality image.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a droplet discharge process in bubble jet inkjet recording.

FIG. 2 is a schematic diagram of a print head used in the present invention.

FIG. 3 is a schematic side sectional view showing a schematic configuration of a printing apparatus as each example in the image forming apparatus of the present invention.

FIG. 4 is an overall schematic perspective view of each embodiment.

FIG. 5 is a diagram schematically showing an ink supply path suitable for the present invention.

FIG. 6 is a schematic perspective view of a wiping unit according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of a wiping operation of the present invention.

FIG. 8 is an explanatory diagram of a wiper cleaner according to the present invention.

FIG. 9 is a perspective view for explaining the configuration of the wiper according to the second embodiment.

FIG. 10 is a perspective view for explaining the configuration of the wiper according to the third embodiment.

FIG. 11 is a diagram for explaining a method for controlling the water content of the wiper according to the third embodiment.

FIG. 12 is a perspective view for explaining a wiper of still another embodiment.

[Explanation of symbols]

1100 print head 1310 Main tank 1320 sub tank 2000 heads 2030 nozzle row 600 head unit 2010 sealant 2020 face side 2040 wiper 700 wiper unit 2050 first wiper 2060 Second wiper 2070 Third wiper 2100 Scraping tongue 2110 absorption roller 2120 Contact roller 2200 front wiper 2210 Rear wiper 900 wiper cleaning unit 2310 Wiper holder 2320 pump 2330 valve

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-5-270000 (JP, A) JP-A-5-278224 (JP, A) JP-A-5-8403 (JP, A) JP-A-7- 81075 (JP, A) JP 8-150710 (JP, A) JP 6-218939 (JP, A) JP 62-251145 (JP, A) JP 10-6516 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/165 B41J 29/17

Claims (5)

(57) [Claims] 1. An ink jet printer for performing recording by using a recording head in which a plurality of nozzle rows for ejecting ink are arranged in a line, and a face has a sealant in parallel, and the nozzle rows are formed by a swirling motion. A plurality of wipers for wiping the face surface in a direction orthogonal to, and when wiping, the recording head moves in the same direction as the traveling direction of the wiper at a speed slower than the moving speed of the tip of the wiper, The inkjet printer is characterized in that the wiper enters the face surface from the side opposite to the advancing direction of the recording head and from the inside of the seal agent, and comes out of the face surface without coming into contact with the seal agent. 2. The inkjet printer according to claim 1, further comprising a wiper cleaner for removing ink droplets attached to the tip of the wiper. 3. The ink jet printer according to claim 2, wherein the wiper cleaner does not function when the wiper is wiping the recording head. 4. The recording head according to claim 1, further comprising an electrothermal converter that generates thermal energy used to eject ink. Inkjet printer. 5. The ink jet printer according to claim 4, wherein the recording head ejects the ink from the ejection port by utilizing the film boiling generated in the ink by the thermal energy generated by the electrothermal converter. .