JP2000255048A - Ink-jet printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a temperature rise in a printing head without excessive power consumption and devices, by providing an ink supply path in the printing head and cooling the printing head having the temperature raised by the printing operation simultaneously with the ink supply. SOLUTION: A printing head 1 comprising a base plate 1b with a nozzle heater distributed in a high density, is provided with a pipe-like circuit 12 made of a material with the excellent heat conductivity. An ink supply path tube 10 from an ink cartridge 3 to the printing head 1 and an ink supply path tube 11 from the printing head 1 to a sub-tank 4 are connected via the pipe-like circuit 12. By an ink flowing in the pipe-like circuit 12, the ink itself acts as a cooling medium to cool the printing head 1. The pipe-like circuit 12, and the tubes 10, 11, from the ink supply path. Therefore, even in the case heat is generated in the printing head 1 during the printing, since the circulating ink has a large heat absorbability, the heat can be discharged to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing apparatus for printing an image on a print medium by using a print head capable of discharging ink from a discharge port.

[0002]

2. Description of the Related Art At present, various printing methods have been developed as printing apparatuses. Among them, an ink jet printing method has excellent quietness and high-speed printing because it does not contact a print medium. It is widely used because high density printing is possible and colorization and miniaturization are easy.

A typical configuration and principle of a means for generating thermal energy as energy used for performing ink ejection are described in relation to a liquid path in which a liquid (ink) is held. Generating thermal energy in the electrothermal transducer by applying at least one drive signal to the electrothermal transducer that corresponds to the recorded information and provides a rapid temperature rise above nucleate boiling, thereby producing a thermal effect on the printhead. This is effective because film boiling occurs on the surface, and as a result, bubbles can be formed in the liquid (ink) corresponding to this drive signal on a one-to-one basis. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed.

FIG. 5 schematically shows a circuit configuration of an ink circulation system in a conventional printing apparatus to which such a basic principle is applied.
Is shown in

As shown in FIG. 5, a conventional printing apparatus includes a print head 101, a recovery tub 102, an ink cartridge 103, a sub tank 104, an ink tank 105, a main pump 106, a recycle pump 107, , A sub-pump 108 and a tube 109 connecting the ink cartridge 103 and the sub-tank 104
A tube 110 connecting the ink cartridge 103 and the ink tank 105; a tube 111 connecting the sub tank 104 and the print head 101; and a tube 112 connecting the print head 101 and the ink tank 105 and provided with a sub pump 108 in the middle. , Recovery tub 1
02 and the ink tank 105, and has an ink flow path formed by a recycle pump 107 and a tube 113 provided with a one-way valve 114 and a filter 115 therebetween. In the ink flow path for circulating the ink, a filter 115 is provided between the ink tank 105 and the recycle pump 107 in the tube 113 of the ink flow path on the downstream side of the print head 101 in order to remove dust in the ink. Is provided together with the one-way valve 114.

In the illustrated ink flow path, by rotating the main pump 106 in a counterclockwise direction, ink is supplied from the ink cartridge 103 to the sub tank 104 via a tube 109 such as a metal pipe or a plastic tube. Ink exceeding the predetermined volume is passed through the tube 110 to the ink cartridge 1.
03 is returned. In the ink supply operation, when the ink consumption reaches a certain amount, printing is temporarily stopped even during printing.

During printing, a print head 101 such as a discharge failure
When the trouble described above occurs, the cleaning is performed and the nozzles of the print head 101 are cleaned.

When the main pump 106 shown in FIG. 5 is rotated clockwise, ink is sent out from the ink tank 105 by pressurization, passes through the tube 111, passes through the liquid path 101a indicated by the dotted line of the print head 101, and prints. The head 101 is filled with ink. A part of the ink is discharged together with the air mixed in the nozzles (not shown) of the print head 101, discharged into the recovery tub 102, temporarily received, and then returned to the ink tank 105 by the recycle pump 107. . Main pump 1
When the sub-pump 108 is rotated at the same time as the rotation of the sub-pump 06, the excess ink in the print head 101 is sucked, and
, The pressure suction circulation is completed.

FIG. 6 shows details of the inside of the nozzle 1a of the print head 1. As shown in FIG. The print head 1 is provided with a heater 11 at a nozzle 1a for ejecting ink formed on a base plate 1b, which is a main body, and by applying electric energy to the heater 11 in accordance with recording information, a heater 11 is provided. The ink is given a rapid temperature rise exceeding the nucleate boiling, and the grown bubbles shrink and extrude the ink in the nozzle 1a, thereby forming an image on the medium.

However, in such a print head 1, in order to discharge ink, a heater 2 is required.
A voltage is applied to the electrothermal transducer 0. Therefore,
A part of the heat energy of the heater 20 is discharged by discharging the ink droplets, but the remaining energy is stored in the print head 1 and the temperature of the print head 1 rises. Thereby, the ink in the print head 1 is further warmed. On the other hand, due to the physical properties of the ink, the viscosity of the ink tends to decrease as the temperature rises. Therefore, the ink with the reduced viscosity discharges more ink even with the same energy, resulting in an increase in the number of printed sheets. As a result, the image density increases. The extent of this effect is even more pronounced in long printheads where many nozzles are densely distributed.

Conventionally, in order to solve the above-mentioned problem, in addition to natural cooling during an ink supply period which automatically enters during printing, the temperature of the print head is reduced by means of forced air cooling by a cooling fan or the like. We have responded so as not to exceed a certain upper limit.

[0012]

However, in the above prior art, power consumption for driving the cooling fan is required, and its effect is not sufficient due to heat transfer characteristics of air and the like.

SUMMARY OF THE INVENTION Accordingly, the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to effectively increase the print head temperature which causes an increase in print density by means of minimizing power consumption and unnecessary devices. An object of the present invention is to provide an ink-jet printing apparatus that can suppress the above problem.

[0014]

According to the present invention, there is provided an ink jet printing apparatus for printing an image on a print medium by using a print head capable of discharging ink from a discharge port. The print head, which has been heated by printing, is cooled at the same time as the ink is supplied during printing.

Further, in the ink jet printing apparatus according to the present invention, the ink supply path of the print head forms a long flow path that bends and extends continuously over the entire cross section in the longitudinal direction and the vertical direction of the print head. It is characterized by doing.

Further, the ink jet printing apparatus according to the present invention is characterized in that the ink supply path of the print head also serves as a cooling flow path.

Still further, the ink jet printing apparatus according to the present invention is characterized in that the ink flowing through the ink supply path of the print head acts as a cooling medium to cool the print head.

The ink jet printing apparatus according to the present invention comprises:
One end of the ink supply path of the print head is connected to the ink cartridge, and the other end is connected to the sub tank.

Further, in the ink jet printing apparatus according to the present invention, the ink supply path may include a pipe-shaped circuit of the print head, a tube connecting the print head and the ink cartridge, and a tube connecting the print head and a subtank. And is characterized by the following.

Further, in the ink jet printing apparatus according to the present invention, the ink supply path includes the print head having the pipe-shaped circuit, the recovery tub, the ink cartridge, the sub tank, the ink tank, and the main pump. , And a recycling pump.

Further, in the ink jet printing apparatus according to the present invention, the main pump is connected between the sub tank and the ink tank, and the recycle pump is connected between the recovery tub and the ink tank. Features.

The ink jet printing apparatus of the present invention comprises:
The print head includes an electrothermal converter that generates thermal energy used for discharging ink.

Further, the ink jet printing apparatus of the present invention is characterized in that the electrothermal transducer generates electric energy which causes ink to boil.

In this specification, "print"
(In the following, it may be referred to as "print") means not only the case where significant information such as characters and figures are formed, but also whether the information is significant or insignificant, and which is manifested so that humans can perceive it visually. Regardless of whether or not the image is formed, a case where an image, a pattern, a pattern, or the like is widely formed on a print medium or a case where the medium is processed is also referred to.

Here, the term "print medium" refers not only to paper used in a general printing apparatus but also to a wide range of materials that can accept ink, such as cloth, plastic films, metal plates, and the like.

Further, the term “ink” is to be interpreted broadly as in the definition of “print” described above. When applied to a print medium, it forms an image, a pattern, a pattern, or processes the print medium. Liquid that can be provided to

In this specification, the term nozzle generally refers to a discharge port, a liquid path communicating with the discharge port, and an element that generates energy used for ink discharge, unless otherwise specified.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the ink jet printing apparatus according to the present invention having the above-described structure, a part of an ink supply circuit is provided in a print head, so that a liquid (ink) is automatically supplied during an ink supply period. )
Is characterized in that the effect of suppressing the temperature rise in the print head is enhanced by utilizing the fact that the heat transfer characteristic is far superior to that of air.

Hereinafter, embodiments of the ink jet printing apparatus of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an ink circulation system of an ink jet printing apparatus to which the present invention is applied.
2 is a front longitudinal sectional view of the print head, FIG. 3 is a transverse sectional view of the print head of FIG. 2, and FIG. 4 is a schematic configuration diagram of an ink jet printing apparatus according to the present invention.

As shown in FIG. 4, an ink jet printing apparatus to which the present invention is applied includes a supply unit 201 for supplying card paper S as a print medium, and a conveyance unit 202 for conveying the supplied card paper S. A printing unit 203 for printing on the conveyed card paper S, and a discharging unit 204 for discharging the printed card paper S.

The card paper S is stacked on the feeding means 201 and sent to the conveying means 202. The printing unit 203 performs printing on the card paper S conveyed by the conveying unit 202 to form an image. The printing unit 203 is of an ink jet type that discharges ink from the print heads 3b, 3c, 3m, and 3y. In the case of the present embodiment, a heating resistor as a heating element is distributed to the nozzles in a print width specification range (4 inches) at a high density (360 dpi), and the printing speed is much higher than that of a serial head. The effect of heating is also large.

In this embodiment, a print head 3b for black ink, a print head 3c for cyan ink, a print head 3m for magenta ink, and a print head for yellow ink are sequentially arranged along the transport direction of the card paper S. 3y are arranged. The rotation pulse signal of the motor for conveying the card paper S and the print head 3
b, 3c, 3m, and 3y are synchronized with the digitized image signals for controlling the ejection of the ink from the respective ejection ports, and the respective image signals of the print heads 3b, 3c, 3m, and 3y are synchronized. In response, the heater 20 which is a heating resistor is energized, and the ink is ejected to the card paper S by causing bubbles to grow and shrink in the ink by utilizing the film boiling generated in the ink by the thermal energy. To form

As shown in FIG. 1, the ink jet printing apparatus of the present invention comprises a print head 1 and a recovery tub 2.
, Ink cartridge 3, sub tank 4, ink tank 5, main pump 6, recycle pump 7
A sub-pump 8, a tube 10 connecting the cartridge 3 and the print head 1, a tube 11 connecting the print head 1 and the sub-tank 4, a tube 13 connecting the ink cartridge 3 and the ink tank 5, a sub-tank 4 and the print Tube 14 for connecting head 1
And a tube 15 in which the print head 1 and the ink tank 5 are connected and a sub-pump 8 is provided on the way, and a recycle pump 7 and a one-way valve 17 and a filter 18 are provided between the recovery tub 2 and the ink tank 5. And an ink flow path formed from the tube 16. In the ink flow path for circulating such ink, a filter 18 is provided between the ink tank 5 and the recycle pump 7 in the tube 16 of the ink flow path on the downstream side of the print head 1 in order to remove dust in the ink. Is a one-way valve 17
It is provided with.

Next, the cooling means for suppressing the temperature rise of the print head 1 will be described with reference to FIGS. 2 and 3 showing the structure of the print head 1. The print head 1 has a nozzle 1a. The heater 20 is composed of a base plate 1b distributed at a high density, and a pipe-shaped circuit 12 made of a material having excellent heat conductivity such as a metal material such as copper or aluminum is integrally formed. A tube 10 on the ink supply path from the ink cartridge 3 to the print head 1 and a tube 11 on the ink supply path from the print head 1 to the sub tank 4
Are connected via a pipe-shaped circuit 12 of the print head 1 (FIG. 1).

Such a pipe-shaped circuit 12 of the print head 1 forms a long flow path which bends and extends continuously over the entire longitudinal and vertical cross sections of the base plate 1b which is the main body of the print head 1. As described above, the print head 1 is made of a material having excellent heat conductivity as described above, and the ink itself acts as a cooling medium by flowing the ink in the pipe-shaped circuit 12, thereby cooling the print head 1. The cooling effect of the print head 1 can be further enhanced. Thus, the print head 1
, A tube 10 connecting the print head 1 and the ink cartridge 3, and a tube 11 connecting the print head 1 and the sub tank 4.
An ink supply path according to the present invention is formed.

Therefore, when heat is generated in the print head 1 during printing, such heat is first stored in the base plate 1b of the print head 1 and also stored in the ink filled in the pipe-shaped circuit 12. However, when the ink consumption reaches a certain amount during printing, the ink is automatically supplied, so that the tubes 10, 11 and Since the ink circulating through the tubular circuit 12 has a much larger heat absorbing capacity than the conventional air cooling system, the flowing ink captures and absorbs the heat generated during printing without leaving, It is designed to escape to the outside.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for performing ink ejection, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. No. 4,723,129, and US Pat.
It is preferable to use the basic principle disclosed in 740,796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or the liquid path holding the liquid (ink). Applying at least one drive signal corresponding to the recording information and providing a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, thereby causing the electrothermal transducer to generate thermal energy, thereby causing the recording head to emit heat energy. This is effective because a film in the liquid (ink) corresponding to the driving signal can be formed one by one by causing film boiling on the heat acting surface. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in U.S. Pat. Nos. 4,463,359 and 4,345,262 are suitable. In addition, U.S. Pat. No. 4,313,124 relating to the invention relating to the rate of temperature rise of the heat acting surface.
If the conditions described in the specification are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, A configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600 which discloses a configuration in which a heat acting portion is arranged in a bending region is also included in the present invention. It is. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even in the case of the serial type as described above, the recording head fixed to the apparatus main body or the electric connection with the apparatus main body or the ink from the apparatus main body is attached to the apparatus main body by being attached to the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

Further, it is preferable to add a discharge recovery means for the recording head, a preliminary auxiliary means, and the like as the constitution of the recording apparatus of the present invention since the effect of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

Regarding the type or number of print heads to be mounted, for example, in addition to one provided for a single color ink, a plurality of inks having different print colors and densities are provided. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent the temperature rise due to thermal energy by using the energy of the state change from the solid state of the ink to the liquid state, or to prevent the ink from evaporating, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start to solidify when reaching the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet recording apparatus of the present invention is not limited to those used as image output terminals of information processing equipment such as computers, copying apparatuses combined with readers and the like, and facsimile apparatuses having a transmission / reception function. It may take a form.

[0047]

According to the first aspect of the present invention having the above-described structure,
The inkjet printing apparatus according to the aspect of the invention is an inkjet printing apparatus that prints an image on a print medium using a print head capable of ejecting ink from an ejection port.In the inkjet printing apparatus, an ink supply path is provided in the print head to supply ink during printing. At the same time, the print head, which has been heated by printing, is cooled, so that a long flow path that is bent and continuously extends over the entire longitudinal and vertical cross sections of the print head is formed, and an extra device is provided. Instead, a cooling effect close to water cooling, which is superior to forced air cooling for driving a conventional cooling fan, is obtained, and effects such as simplification of the apparatus and reduction in power consumption, such as elimination of a cool air fan, can be expected.

According to a second aspect of the present invention, there is provided an ink jet printing apparatus, wherein the ink supply path of the print head has a long flow which bends continuously over the entire cross section in the longitudinal direction and the vertical direction of the print head. Since the path is formed, since the ink has a large heat absorbing ability, it is possible to capture the heat generated during printing without leaving the flowing ink and to escape to the outside, thereby performing good cooling.

In the ink jet printing apparatus according to the third aspect of the present invention, since the ink supply path of the print head also serves as a cooling flow path, no extra apparatus is provided, thereby simplifying the apparatus and reducing power consumption. Can be planned.

In the ink jet printing apparatus according to a fourth aspect of the present invention, since the ink flowing through the ink supply path of the print head acts as a cooling medium to cool the print head, the ink jet printing apparatus can be reliably formed with a simple structure. The print head can be cooled.

According to a fifth aspect of the present invention, the ink supply path of the print head has one end connected to the ink cartridge and the other end connected to the sub-tank. The flow path can be continuously formed in a long and simple configuration, and the ink can be suitably supplied.

According to a sixth aspect of the present invention, in the ink jet printing apparatus, the ink supply path includes a pipe-shaped circuit of the print head, a tube connecting the print head and the ink cartridge, and the print head and a sub tank. Since the ink supply path is formed by the connecting tube, the ink supply path can be easily configured.

In an ink jet printing apparatus according to a seventh aspect of the present invention, the ink supply path includes the print head having the pipe-shaped circuit, the recovery tub, the ink cartridge, the sub-tank, and the ink tank. Since the main pump and the recycle pump are provided, the ink supply path to the print head can be made simple.

In the ink jet printing apparatus according to the present invention, the main pump is connected between the sub tank and the ink tank, and the recycle pump is connected between the recovery tub and the ink tank. Therefore, the ink supply path can be simply configured.

The ink jet printing apparatus according to the ninth aspect of the present invention has an electrothermal converter that generates heat energy used by the print head to eject ink. By discharging, high density and high definition of the print can be achieved, and a beautiful print can be obtained.

In the ink jet printing apparatus according to a tenth aspect of the present invention, since the electrothermal transducer generates electric energy that causes film boiling of the ink, the ink is ejected using the electric energy. High density and high definition printing can be achieved, and a beautiful print can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an ink circulation system in an inkjet printing apparatus according to the present invention.

FIG. 2 is a front vertical sectional view of a print head of the inkjet printing apparatus according to the present invention.

FIG. 3 is a cross-sectional view of the print head of the present invention of FIG. 2;

FIG. 4 is a schematic configuration diagram of an inkjet printing apparatus according to the present invention.

FIG. 5 is a schematic circuit diagram of an ink circulation system of a conventional inkjet printing apparatus.

FIG. 6 is a detailed partial sectional view of the inside of a nozzle of a print head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Print head 2 Recovery tub 3 Ink cartridge 4 Sub tank 5 Ink tank 6 Main pump 7 Recycle pump 8 Sub pump 10 Tube 11 Tube 12 Pipe circuit 13 Tube 14 Tube 15 Tube 16 Tube 17 One-way valve 18 Filter 20 Heater

Claims (10)

[Claims] 1. An ink jet printing apparatus for printing an image on a print medium by using a print head capable of discharging ink from a discharge port, wherein an ink supply path is provided in the print head, An ink jet printing apparatus, wherein the print head heated by printing is cooled. 2. The ink supply path of the print head forms a long flow path that bends and extends continuously over the entire longitudinal and vertical cross sections of the print head. The inkjet printing apparatus according to claim 1. 3. The ink jet printing apparatus according to claim 1, wherein the ink supply path of the print head also serves as a cooling channel. 4. The print head according to claim 1, wherein the ink flowing through the ink supply path of the print head acts as a cooling medium to cool the print head.
4. The inkjet printing apparatus according to any one of claims 3 to 3. 5. The ink jet printing apparatus according to claim 1, wherein one end of the ink supply path of the print head is connected to the ink cartridge, and the other end is connected to a sub tank. 6. The ink supply path is formed by a pipe-shaped circuit of the print head, a tube connecting the print head to the ink cartridge, and a tube connecting the print head to a sub-tank. The inkjet printing apparatus according to any one of claims 1 to 5, wherein: 7. The ink supply path includes the print head having the pipe-shaped circuit, a recovery tub, the ink cartridge, the sub tank, an ink tank, a main pump, and a recycle pump. The inkjet printing apparatus according to any one of claims 1 to 6, wherein: 8. The apparatus according to claim 6, wherein the main pump is connected between the sub tank and the ink tank, and the recycle pump is connected between the recovery tub and the ink tank. Inkjet printing equipment. 9. The ink-jet printing apparatus according to claim 1, wherein the print head includes an electrothermal converter that generates thermal energy used for discharging ink. 10. The ink-jet printing apparatus according to claim 9, wherein said electrothermal converter generates electric energy for causing film boiling of the ink.