JPH11129499A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate guiding of bubbles into a channel at the time of moving an ink by specifying conditions at the time of maintenance including an ink movement at a flowing velocity of supplying the ink from a ink tank without entraining the bubbles and at an ink moving velocity. SOLUTION: The ink jet recording comprises a bubble mixture preventing means for satisfying a M<=V with a flowing velocity V for supplying an ink from an ink tank 4 without entraining bubbles and an ink moving velocity M for moving the ink under the condition at the time of maintenance including an ink movement. The recorder carries a head holder 3 for holding an ink jet head 2 with a water-repellent treated nozzle surface, the tank 4, a transfer member 5 for coupling the head 2 to the tank 4, and a circuit board 7. An ink residue sensing means and an environmental temperature sensing means are provided at the tank 4 and the board 7. The head 2 is provided with a plurality of discharge ports for discharging inks of different colors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for forming an ink image on a recording medium such as recording paper by flying ink droplets, and more particularly to a means for preventing air bubbles from entering.

[0002]

2. Description of the Related Art An ink jet recording apparatus directs ink from a plurality of nozzle openings of an ink jet head, a droplet diameter,
This is a recording apparatus capable of obtaining good printing quality by discharging while keeping the discharge speed constant. Further, since the number of ejection ports and the type of ink can be easily increased in the ink jet recording apparatus, color recording has progressed and the ink jet recording apparatus has become a mainstream recording apparatus at present. For this reason, the number of nozzles per ink jet recording apparatus also tends to increase, reaching 80 to 100 holes or more. However, on the other hand, there is also a disadvantage that a nozzle surface having several nozzle openings for ejecting ink becomes dirty, or air bubbles are mixed in the flow path, and if one of the nozzle openings causes ejection failure, good printing cannot be performed. is there. Therefore, a maintenance station is provided in the ink jet recording apparatus as a means for recovering the ejection failure to a normal state.

As means for operating the maintenance station to return to a good discharge state, Japanese Patent Publication No.
As described in US Pat.
A method has been proposed in which the ink is released to the atmosphere during suction and the backflow is suppressed, as in -214795. In general, the wiper is brought into contact with the discharge port surface of the ink jet head and the discharge is performed by moving the wiper and the discharge port surface relatively. A nozzle surface cleaning means for removing ink attached to the outlet surface, a suction port connected to a suction pump or the like, and a discharge port provided with a valve equipped with a valve for communicating with the atmosphere. An ink moving device that recovers by discharging dust and bubbles clogged in the discharge port by suction, and an ink evaporation prevention unit that covers the nozzle with a cap or seal to prevent ink from evaporating from the nozzle. Are combined. The maintenance operation is performed when the user presses a maintenance switch in order to recover the ejection failure to a good ejection state when the ejection failure occurs, or when the ejection failure is predicted in advance according to the storage state, the inkjet recording apparatus is used. This is performed when the stored ink is exhausted and the ink is injected again.

When the maintenance is performed using the maintenance station, if the ink moving speed M at the time of discharging the ink using the ink moving device exceeds the flow velocity V at which the ink can be supplied without entraining the bubbles from the ink tank, the ink is discharged. Bubbles are mixed in the flow path. When air bubbles are mixed, even if pressure is applied to the ink to eject ink droplets from the nozzle openings, the air bubbles are elastic, so the applied pressure is absorbed and ink cannot be ejected, or ejection failure occurs. I do. The maintenance station is provided in the ink jet recording apparatus in order to recover the ejection failure. However, in this case, the operation of the maintenance station causes the ejection failure to occur in the nozzles that perform the normal ejection. The cause of the discharge failure is when there is drying near the nozzle opening, when dust such as paper dust adheres, or when the above-mentioned bubbles enter the flow path. To recover them,
The problem must be solved by discharging unnecessary ink using an ink moving device.However, in the case of drying near the nozzle opening or dust such as paper dust attached due to minor trouble, discharge the ink near the nozzle. However, when bubbles enter the flow path, ink in the flow path must be discharged together with the bubbles to remove the bubbles when the bubbles enter the flow path. Must discharge a lot of ink. Therefore, if air bubbles are mixed in by performing maintenance, more ink must be discharged by the ink moving device in order to recover the air bubbles, so that not only the ink cannot be recovered but also ink is wasted. become. As a result, there is a problem that the running cost increases, the time required for maintenance increases, and the throughput decreases. In particular, in the case of using pigment ink, since the re-dissolvability and re-dispersibility of the dried ink are poor, the amount of discharged ink required for recovery is increased, and the amount of wasteful use of the ink is increased. Is even larger. In addition, since the pigment is not soluble in water, it is necessary to use an ink using a pigment as a coloring material in order to obtain a printing result requiring water resistance. In order to require complete water resistance for the printing result, a resin for fixing the pigment to the recording paper is required. As a method of adding the resin, when dispersing the pigment in the liquid, a polymer that does not dissolve in water once dried in the dispersant is used, or the resin having a fixing function is dispersed in the ink as an emulsion. There are methods. The pigments in the ink are configured so that they do not agglomerate due to Van der Waals forces or the like, but when the liquid component in the ink evaporates, the pigment particles adhere to each other to form a large mass. This mass has the property that it does not redisperse when the liquid component is simply given again. As described above, since the pigment ink contains components that are not dissolved again after drying once or components that are not redispersed, once dried and solidified, the pigment ink cannot be removed by dispersion or dissolution. Therefore, if air bubbles are mixed, the liquid component of the ink evaporates in the air bubbles and the ink dries, or if ejection failure occurs, the ink dries in the nozzle and the nozzle for ejecting the ink is used Clogging may destroy the ink jet recording apparatus.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides an ink jet recording apparatus having means for preventing air bubbles from being introduced into a flow path when ink is moved by using an ink moving device. It is in.

[0006]

In order to solve the above problems, an ink jet head having a nozzle opening at least on a nozzle surface for discharging ink, a pigment ink using a pigment as a coloring agent, and an ink jet head An ink tank for storing the ink in the recording apparatus, a drive waveform generating circuit for discharging the ink from the nozzle opening of the inkjet head, at least a nozzle surface cleaning device, an ink moving device for discharging ink from the nozzle, and a nozzle An ink jet recording apparatus comprising: a maintenance station comprising an ink evaporation preventing means for preventing the evaporation of the ink; and a remaining amount detecting means for knowing the remaining amount of the ink. And the flow velocity V at which ink can be supplied from the ink tank without involving air bubbles, The ink movement speed M for performing ink movement has a bubble mixing prevention means characterized by satisfying M ≦ V, and the flow velocity V at which ink can be supplied without entraining bubbles from the ink tank of the bubble mixing prevention means is known. It is characterized in that the means uses at least one of a remaining amount detecting means for knowing the remaining ink amount and an environmental temperature detecting means for knowing the environmental temperature. That is, in the ink jet recording apparatus according to the first aspect, an ink jet head having a nozzle orifice on at least a nozzle surface for discharging ink, a pigment ink using a pigment as a colorant, and storing the ink in the ink jet recording apparatus. Ink tank, a drive waveform generating circuit for discharging the ink from the nozzle opening of the ink jet head, at least a nozzle surface cleaning device, an ink moving device for discharging ink from the nozzle, and preventing evaporation of ink from the nozzle An ink jet recording apparatus comprising: a maintenance station comprising ink evaporation preventing means; and a remaining amount detecting means for knowing a remaining amount of ink, wherein conditions for performing maintenance including ink movement include bubbles from the ink tank. The flow velocity V at which ink can be supplied without being caught An ink moving speed M that performs dynamic, characterized in that it has a bubble mixing prevention means that satisfies M ≦ V. Further, in the ink jet recording apparatus according to the second aspect, the means for knowing the flow rate V capable of supplying ink without entraining bubbles from the ink tank of the bubble entrapment preventing means includes a remaining amount detecting means for knowing the remaining amount of ink;
It is characterized in that at least one or more of environmental temperature detecting means for knowing the environmental temperature is used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following configuration.

(Embodiment) A bubble mixing preventing means of the present invention will be described. An ink jet recording apparatus is provided with an ink tank for storing ink to be ejected. The ink tank is designed so as not to discharge air bubbles together with the ink as much as possible. However, when the amount of the ink is reduced, the ink discharging performance is reduced and air bubbles are mixed. When the ink is almost exhausted, only the gas is discharged. Such a phenomenon is particularly significant when a porous body is provided in the ink tank. Although there are many examples in which a porous body is provided in an ink tank, for example, as the structure of the ink tank, the present applicant has proposed a cover having a vent, four side plates, and a surface in which the supply port near the center of the bottom is lowered by one step. A print head comprising a print head and a separable connection part, and a fibrous material which is pressed by the lid and the side plate and inserted into the ink container in a compressed state, using a fiber material having a good ink discharge property, An ink tank has been proposed in which a felt block having a high fiber density and a felt block having a low fiber density are provided in the vicinity, and the liquid collecting effect of ink is enhanced by utilizing the capillary force generated by the density difference of the ink holder. . In such an ink tank having a porous body in its internal configuration, the flow rate V at which ink can be supplied from the ink tank without involving air bubbles depends on the remaining amount of ink and the environmental temperature (the viscosity of the ink increases as the environmental temperature increases). As the ink flow rate increases, the speed V at which ink can be supplied without entrapping air bubbles increases, whereas when the ambient temperature decreases, the speed V at which ink can be supplied without entrapping air bubbles V
Becomes smaller. ). Methods for detecting the remaining amount of ink include calculating the remaining amount from the amount of ink ejected during maintenance and the number of ejected ink droplets, measuring the weight, and measuring the electrical resistance. And a method of measuring the ink supply pressure of the ink tank. As a means for knowing the environmental temperature, a thermistor can be provided on the circuit board or inside the ink jet recording device such as around the ink tank to know the environmental temperature.

A method for determining the ink movement speed M for performing the ink movement is as follows. The ink is discharged from the ink tank using the ink moving device in a temperature range where the ink jet recording device is used, and bubbles are discharged together with the ink. Measure the range that will not be used. In this way, the relationship between the remaining amount of ink, the environmental temperature, and the flow velocity V at which ink can be supplied without entraining bubbles from the ink tank is grasped. This relationship is stored in the ink jet recording apparatus. In an ink jet recording apparatus having only an ink remaining amount detecting means, when a certain amount of ink remains, a value when the flow velocity V at which ink can be supplied without entraining bubbles from the ink tank in the operating temperature range is the smallest is stored. deep. When performing maintenance including ink movement,
Reference is made to the flow rate V at which ink can be supplied without entrapping air bubbles from the ambient temperature or from the remaining amount of ink. When the ink movement speed M when performing the ink movement for maintenance is higher than the reference V, the speed is suppressed to V without discharging unnecessary ink at the ink movement speed M. If V is larger than M, unnecessary ink is discharged at the ink moving speed M without changing the ink moving speed. This prevents bubbles from flowing from the ink tank into the ink flow path.

(Examples 1 and 2 and Comparative Example 1) FIG. 1 is a schematic view of an ink jet recording apparatus embodying the present invention. In FIG. 1, reference numeral 1 denotes a carriage, which includes a head holder 3 for holding an ink jet head 2 having a nozzle surface subjected to a water-repellent treatment, an ink tank 4, a relay member 5 for connecting the ink jet head 2 and the ink tank 4, and a circuit board 7. Mount. The ink tank 4 and the circuit board 7 have ink remaining amount detecting means and environmental temperature detecting means. The inkjet head 2 has a plurality of ejection ports for ejecting inks of different colors. A carriage motor (not shown) drives the carriage 1 via the timing belt 8, and
It is reciprocated along the guide rail 9 to the left and right in the figure. FP
C30 connects a drive circuit (not shown) to the circuit board 7.
On the other hand, a paper feed motor (not shown) drives the paper feed roller 31 and the paper discharge roller 12, pulls out the recording paper 32 onto the platen 14, and moves the recording paper 32 in a direction perpendicular to the moving direction of the carriage. In this manner, while moving the carriage 1 and the recording paper 32, the positions of the respective heads 2 on the recording paper 32 are two-dimensionally changed, and the ink is supplied from the heads 2 according to a recording signal by a known means such as piezoelectric driving. , The recording pattern such as an image and a character can be recorded on the recording paper 32. A nozzle surface cleaning unit 18 for removing dirt on the nozzle surface of the inkjet head and an ink moving unit 21 for removing unnecessary ink and bubbles in the nozzle are provided beside the printing area. In the ink jet recording apparatus of this embodiment, an ink moving device capable of discharging ink by suctioning with a cap is provided. As the ink, at least a pigment such as phthalocyanine, azo-based, perylene-based, or carbon black is dispersed in water as a coloring agent, and a humectant having a moisturizing function such as glycerin, diethylene glycol, or propanediol is added to the ink.
To 40 parts by weight of an aqueous pigment ink.

An ink moving device for discharging ink from a nozzle includes a suction device that covers the nozzle provided on the nozzle surface with a cap, suctions and discharges ink by reducing the pressure inside the cap, and an ink supply side. Any type of pressurizing device can be used, which presses ink out of the nozzles to discharge unnecessary ink. As a nozzle surface cleaning device for removing ink on the nozzle surface, a nozzle surface cleaning member in which an elastic base is attached to a holder serving as a support and the surface of the elastic body is covered with a sheet-like ink absorbing member is used. did. As the base elastic body, a porous body such as rubber or sponge or a fiber entangled with felt or the like can be used. In this embodiment, rubber is used. As the ink absorbing member, polyester and nylon were used. The ink absorbing member is made to be able to expose a new surface when the ink is absorbed and becomes dirty. As an operation, the nozzle surface cleaned with ink and the nozzle surface cleaning member are moved to the opposite position. Next, by bringing the nozzle surface cleaning member into contact with the nozzle surface, the ink penetrates the ink absorbing member and the ink on the nozzle surface is moved to the nozzle surface cleaning member side. The contact pressure was set to a pressure at which the ink absorbing member was brought into close contact with the nozzle surface. The contact was maintained while the ink on the nozzle surface moved to the ink absorbing member.
Next, since there is a case where ink that cannot be absorbed by the ink absorber remains, the nozzle surface cleaning member and the nozzle surface are removed by relatively moving. The number of operations of moving the nozzle surface cleaning member and the nozzle surface in relative contact with each other was performed twice. Thus, the nozzle surface was cleaned.

An ink jet recording apparatus having no air bubble mixing preventing means, an ink jet recording apparatus having an air bubble mixing preventing means using a remaining amount detecting means and an environmental temperature detecting means, and an ink jet recording apparatus using the remaining amount detecting means. Prepare an ink jet recording apparatus having air bubble intrusion prevention means, install ink tanks filled with ink, perform continuous printing, and perform maintenance including ink movement every 3 hours during continuous printing. Was. In the evaluation, the amount of ink initially filled in the ink tank was set to 100, and the amount of ink remaining when an ejection failure occurred due to mixing of bubbles was measured.
As a result, an ink jet recording apparatus having no bubble intrusion prevention means caused ejection failure at a 40% ink remaining amount, but an ink jet recording apparatus having a bubble intrusion prevention means using a remaining amount detection means did not. In the ink jet recording apparatus which can perform good ejection up to 30% of the remaining amount of ink and has a bubble mixing preventing means using the remaining amount detecting means and the environmental temperature detecting means, it is possible to perform good ejection to the 20% remaining amount of ink. Could be printed. From this comparison, it can be seen that the ink consumption increases in the ink jet recording apparatus having the bubble intrusion prevention means.

[0013]

As described above, according to the present invention, even if a discharge failure occurs during printing and maintenance including ink movement is performed, bubbles are not mixed into the flow path. It is possible to perform good printing even when the number of images is reduced. Further, since the usable amount of ink has increased, the amount of ink that can be used for printing has increased. As a result, running costs have been reduced. Further, since pigment inks can be used, printing with excellent water resistance and light resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an ink jet recording apparatus.

[Explanation of symbols]

 Reference Signs List 1 carriage 2 inkjet head 3 head holder 4 ink tank 5 relay member 7 circuit board 8 timing belt 9 guide rail 12 paper discharge roller 14 platen 18 nozzle surface cleaning means 21 ink moving means 30 FPC 31 paper feed roller 32 recording paper

Claims (2)

[Claims] An ink-jet head having a nozzle port on at least a nozzle surface for discharging ink; a pigment ink using a pigment as a colorant; an ink tank for storing the ink in an ink-jet recording apparatus; A drive waveform generating circuit for discharging ink from the nozzle opening of the ink jet head, at least a nozzle surface cleaning device, an ink moving device for discharging ink from the nozzle, and an ink evaporation preventing means for preventing evaporation of ink from the nozzle An ink jet recording apparatus equipped with a maintenance station and a remaining amount detecting unit for knowing the remaining amount of ink, wherein the conditions for performing maintenance including ink movement are such that ink is supplied from the ink tank without entrapping air bubbles. The flow velocity V that can be achieved and the ink movement velocity M at which the ink is moved are M ≦ M. An ink jet recording apparatus comprising: a means for preventing air bubbles from being mixed. 2. A means for knowing a flow rate V at which ink can be supplied from an ink tank without entraining bubbles from an ink tank of a bubble mixing preventing means, a remaining amount detecting means for knowing a remaining ink amount, and an environmental temperature for knowing an environmental temperature. 2. An ink jet recording apparatus according to claim 1, wherein at least one of said detecting means is used.