JPH10226072A - Ink-jet recording head and ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording head which can prevent degradation of print quality as a result of air bubbles left in an ink flow passage, thereby enabling highly elaborate printing at higher speed, and an ink-jet recording apparatus loading the ink-jet recording head. SOLUTION: The ink-jet recording head has a heat-generating element 104. Air bubbles are formed in ink by heat energy generated by the element 104, whereby the ink is discharged. In order to remove remaining air bubbles 110, an ink jet flow by a jet flow generation means 202 such as a pump or the like is sent through a tube 203 and a jet flow hole 202 and jetted out to a common liquid chamber 108 above the heat-generating element 104.

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 head having a device for improving the printing quality and increasing the printing speed, and a recording device equipped with the head.

[0002]

2. Description of the Related Art Conventionally, an ink jet recording apparatus is provided in front of a liquid flow path by generating a pressure change in the liquid flow path by changing the volume of the liquid flow path by mechanical deformation of a piezoelectric element. There is known a method in which droplets are ejected from an orifice (ejection port) for recording, and a method in which a pair of electrodes is provided in front of the orifice to deflect the flight direction of the droplet ejected from the orifice for recording. Have been.

Furthermore, bubbles are instantaneously generated by rapidly generating heat from a heating element serving as a heat generator disposed in the ink flow path, and the ejection force generated by the generation of the bubbles causes a forward force in the ink liquid flow path. An ink jet system has been proposed in which a recording liquid is discharged using so-called thermal energy for discharging liquid droplets from an orifice.

[0004] This ink jet recording head is
Since orifices for ejecting droplets for recording can be arranged at a high density, it is possible to perform high-resolution and high-definition recording. In fact, it is possible to make full use of the advantages of IC technology and micro-machining technology, which have been making remarkable progress in recent semiconductor technology and improving reliability, and it is easy to make them longer and planar (two-dimensional). For this reason, it has attracted particular attention as being capable of easily forming a multi-nozzle and high-density mounting, having high productivity in mass production, and capable of reducing manufacturing costs.

With respect to an ink jet recording apparatus equipped with the above-described ink jet recording head, an apparatus aimed at improving ejection efficiency, ejection responsiveness, ejection stability, long-time continuous recording property, high-speed recording property, etc. For example, it is specifically disclosed in JP-A-55-59975, JP-A-55-59976, JP-A-55-59977, and UPS 4330787. In addition, Japanese Patent Publication No. 61-59911
No. 59914 discloses an apparatus which facilitates miniaturization and high-density images.

[0006]

However, at present, there is a demand for reliably executing higher-speed and higher-definition recording. That is, the improvement of the ink jet recording head and the ink jet recording apparatus described in each of the above publications has given a technical problem of improving the ejection performance and realizing high-speed printing.

FIG. 8A shows a conventional example of the structure of an ink jet recording head for discharging ink using thermal energy.
Is shown schematically in FIG.

As shown in FIG. 8A, the structure of the ink jet recording head includes an ink flow path 107, a heating element
4. An orifice 105 is provided.

The heating element 104 generates heat instantaneously when a drive signal is applied, and instantaneously heats the liquid on the upper side in the figure to generate bubbles.

Due to the change in the volume of the bubbles generated at this time, the liquid is ejected from the orifice 105, and the ink adheres to the surface of a recording member such as paper, and recording is performed. The supply of the required amount of ink into the ink flow path 107 is performed by a capillary force from a common liquid chamber (not shown) or an appropriate pressure applied by some means.

[0011] However, in the above-mentioned conventional example, as the printing speed is increased, the ink discharge interval per printing becomes shorter. Therefore, when the ink is continuously discharged, bubbles generated in the ink flow path are generated. Since there is not enough time to defoam, it remains as it is. The remaining air bubbles affect the ejection performance of the ink, causing a problem of deteriorating the print quality.

The reason why the residual air bubbles degrade the print quality will be described.

If bubbles remain in the nozzle during foaming, the energy of foaming is consumed to crush the bubbles, and as a result, the ink ejection force is reduced. In particular, in the case where the air bubble is located above the heating element, the air bubble cannot be moved due to a sudden increase in pressure and is crushed, and the ejection force is greatly reduced. When the ejection force is weakened, the ink ejection amount becomes unstable, causing unevenness in printing and deteriorating printing quality.

A mechanism for generating bubbles in the ink jet recording head will be described with reference to FIGS. 8 (a) and 8 (b). Each part is exaggerated and schematically shown for easy understanding of the phenomenon.

When a drive signal is input to the heat generating element 104, which is a heat generating element, a main bubble 601 is generated in the ink flow path 107 filled with ink as shown in FIG. ), The volume change of the bubbles generated at that time causes the main droplet 60
2 jumps out of the orifice 105.

As the volume of the main foam 601 decreases rapidly, FIG.
As shown in (b), the ink before and after the main bubble 601 moves in the direction of the arrow. As shown by arrows A and B, main bubble 601
The ink coming from before and after is hit when the main bubble 601 disappears, and cavitation occurs. At this time,
As shown in FIG. 8C, minute bubbles (hereinafter referred to as residual bubbles 110) are generated in the nozzle in addition to the main bubble 601.

Normally, such residual bubbles 110 remain near the defoaming point of the main bubble even after the meniscus returns, and are dissolved again in the ink and defoamed by the next foaming. Alternatively, the ink moves to the vicinity of the meniscus with the movement of the ink in the ink flow path at the time of refilling, and the bubble disappears in a shorter time in the process.

Conventionally, there was a sufficient discharge interval for the residual bubbles to be eliminated, so that residual bubbles did not cause a problem. However, this problem has been highlighted in realizing high-speed printing.

At present, as printing speed is being increased, deterioration of print quality due to residual bubbles is a serious problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording head capable of preventing a decrease in print quality due to residual air bubbles in an ink flow path and capable of performing high-speed and high-definition printing, and the ink jet recording head. An object of the present invention is to provide an ink jet recording apparatus.

[0021]

SUMMARY OF THE INVENTION An ink jet recording head according to the present invention has a heating element, and the ink is ejected by generating bubbles in the ink by the heat energy generated by the heating element, and the ink is ejected onto a recording medium. The apparatus for performing recording is characterized in that a device for generating a flow is provided in a part of the ink jet recording head, specifically, inside and near the ink flow path to remove residual air bubbles.

With the ink jet recording head configured as described above, high-speed and high-definition printing can be performed by eliminating the deterioration of print quality due to residual air bubbles.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings.

As described in the above section, in the ink jet recording head, when a driving signal is input, the heating element 104 rapidly generates heat, and the heat causes the heating element 104 to generate heat.
The liquid on the surface is heated instantaneously and foaming occurs instantaneously. The ink is ejected by the ejection force generated by the foaming.

When the main bubbles disappear, bubbles may be generated due to cavitation. The generated air bubbles remain in the ink flow path to become residual air bubbles 110, and depending on the shape of the ink flow path, there is a high possibility that the main air bubbles will remain at the position where the main air bubble disappears. In an ink jet recording head having an ink flow path shape, the ink tends to remain on the heating element 104.

When the residual air bubbles 110 are present above the heating element 104, they are crushed almost without moving due to a sudden increase in pressure during foaming. At that time, the power of foaming is consumed, so that the growth of the main foam is reduced, and stable printing cannot be obtained.

Therefore, in this embodiment, the ink flow path 107
By generating a flow in the inside, the residual bubbles 110 are moved from above the heating element 104.

(Embodiment 1) FIG. 1 is a diagram for explaining the main components of an ink jet recording head according to a first embodiment of the present invention.

The present embodiment is characterized in that a jet part is provided in a part of an ink jet recording head as a flow generating device for generating a flow in an ink flow path.

As shown in FIG. 1, the jet portion comprises a jet generating device 201 such as a pump, and a jet hole 202 for jetting an ink jet generated by the device 201 through a tube 203 to a position above the heating element 104. Is done.

A method for generating a jet will be described.

A jet generator 20 composed of a pump or the like
The ink jet generated by 1 is jetted into the ink flow path 107 through the tube 203 and the jet hole 202. The intensity of the jet and the number of the jet holes 202 need only be such that the residual air bubbles 110 move from above the heating element 104 because new air bubbles are generated when the jet is too strong.

The jet direction of the jet is such that the ink does not overflow from the orifice 105 and that the air bubbles do not move toward the heating element 104 as shown in FIG.
The liquid was ejected toward the common liquid chamber 108 once.

It is desirable that the jet flow be generated intermittently so as not to affect the bubbling due to the main bubble at the time of printing by the ink jet recording head, and when the air bubbles are accumulating above the heating element 104. An appropriate jet generation interval was examined by an experiment, and the timing of jet generation was adjusted.

As a result of printing using the ink jet recording head constituted by the jet generating device 201 shown in this embodiment, no print unevenness was generated. This is probably because the residual air bubbles 110 were removed from the upper part of the heating element 104 by the jet flow, so that the foaming energy of the main air bubbles was not consumed for crushing the residual air bubbles.

(Embodiment 2) FIG. 2 is a diagram for explaining the main components of an ink jet recording head according to a second embodiment of the present invention.

The present embodiment is characterized in that the flow generating device is based on a circulating moving object.

As shown in FIG. 2, the circulating moving object is a wire 1 rotating or reciprocating above the ink flow path 107.
02, a rotary or reciprocating drive device 101 for driving the wire 102, a wire passage hole 103 for guiding the wire 102, a wire support protrusion 106, and the like.

That is, the wire 102 passes through the wire passage hole 103 and is supplied with a driving force by the rotary driving device 101 in the direction of the arrow while being supported by the wire support protrusion 106 and is sent.

As a method of generating a driving force for the wire transmission by the rotary driving device 101, the wire 102 is transmitted in the ink flow path 107 at a speed sufficient to generate a constant flow without affecting foaming. Any method that can be used may be used.

As a means for forming the wire passage hole 103, any means such as laser processing may be used. The diameter of the wire passage hole 103 does not affect foaming, and the diameter of the wire 102 conforms to the diameter.

The means for forming the projection 106 may be either laser processing or integral molding. Also, the protrusion 10
6 may be added after the formation of the ink flow path 107. Since the shape of the protrusion 106 changes depending on the shape of the head and the ink flow path 107, it cannot be said unconditionally.
Any shape may be used as long as the line 2 can be smoothly transmitted.

The operation of the rotary drive 101 will be described.

During the printing operation by the ink jet recording head, the wire 102 is sent by the rotary driving device 101 in the direction of the arrow in the drawing, and the flow continues to be generated above the heating element 104, and the residual bubble 110 is moved from above the heating element 104. .

As a result of printing using the ink jet recording head thus configured, no printing unevenness occurred. This is because the residual air bubbles 110 are removed from the upper part of the heating element 104 by generating a flow in the flow path, so that the foaming energy of the main air bubbles is not consumed for crushing the residual air bubbles 110. Conceivable.

(Embodiment 3) FIG. 3 is a diagram for explaining the main component configuration of an ink jet recording head according to a third embodiment of the present invention.

The present embodiment is characterized in that the flow generating device is based on the second heating element.

As shown in FIG. 3, a heating element 3 for removing bubbles is provided above the heating element 104 of the ink jet recording head.
02 is provided.

A method for removing residual bubbles by using the bubble removing heating element 302 will be described. The heating element 302 for removing bubbles is heated and foamed after defoaming the main foam so as not to affect the foaming of the main foam by the heating element 104. This foaming may be performed at appropriate intervals during printing by the ink jet recording head, and does not always need to be performed after the main foam has disappeared. The degree of accumulation of the bubbles, the time until the accumulation, and the like were examined by an experiment, and based on the results, the period of the voltage applied to the heating element 302 for removing bubbles was determined.

By the flow generated by the bubbling of the heating element 302 for removing bubbles, the remaining bubbles 110 in the vicinity thereof are repelled, and the bubbles are removed from above the heating element 104.

As a result of printing using the ink jet recording head configured as described above, no printing unevenness occurred. This is presumably because the residual bubbles 110 were removed from the upper part of the heating element 104 by the flow generated by the foaming, so that the foaming energy of the main bubbles was not consumed for crushing the residual bubbles 110.

(Embodiment 4) FIG. 4 is a view for explaining the main components of an ink jet recording head according to a fourth embodiment of the present invention.

The present embodiment is characterized in that the flow generating device is based on a vibrating element.

As shown in FIG. 4, a piezo element 301 is provided above the heating element 104 of the ink jet recording head.

A method for removing residual air bubbles by using the piezo element 301 will be described.

After the main bubble is eliminated by the heating element 104, the piezoelectric element 301 is vibrated in the direction of the arrow to generate a pressure wave. This vibration may be performed at an appropriate interval during printing by the ink jet recording head, and is not always required to be performed after the main bubble is foamed. The degree of accumulation of the bubbles, the time until the accumulation, and the optimum shape were examined by an experiment, and the amplitude, vibration period, and shape of the piezo element 301 were determined based on the results.

The pressure bubbles cause the residual bubbles 110 in the vicinity thereof to be repelled and removed from the upper portion of the heating element 104.

As a result of printing using the ink jet recording head thus configured, no printing unevenness occurred. This is because the residual air bubbles 110 are removed from the upper part of the heating element 104 by generating a flow in the flow path, so that the foaming energy of the main air bubbles is not consumed for crushing the residual air bubbles 110. Conceivable.

(Embodiment 5) FIG. 5 is a view for explaining the main components of an ink jet recording head according to a fifth embodiment of the present invention.

The present embodiment is characterized in that the flow generating device is based on a reciprocating object.

As shown in FIG. 5, a reciprocating object 303 is provided above the heating element 104 of the ink jet recording head. Here, the reciprocating object 303 uses a spring, but may be similar.

A method for removing the residual air bubbles by using the reciprocating object 303 will be described.

The bubbling of the main bubble by the heating element 104 causes a rapid pressure change in the ink flow path 107, generating a pressure wave. At this time, the reciprocating object 303 provided above the heating element 104 vibrates by receiving the pressure wave. Due to the vibration of this spring, the residual air bubbles 11 above the heating element 104
0 is flipped and removed from the upper part of the heating element 104.

As a result of printing using the ink jet recording head thus configured, no printing unevenness occurred. This is because the residual air bubbles 110 are removed from the upper part of the heating element 104 by generating a flow in the flow path, so that the foaming energy of the main air bubbles is not consumed for crushing the residual air bubbles 110. Conceivable.

As described above, in each embodiment, the jet part, the circulating moving object, the heating element 302 for removing bubbles, and the piezo element 301
In addition, by the flow generating device using the reciprocating object 303, the residual air bubbles 110 are removed from the upper part of the heating element 104, and the ink ejection force is stabilized without being scraped, and high quality is achieved.
High-definition printing can now be obtained.

In the above-described embodiment, the device for removing air bubbles is provided in the ink flow path 107. However, it is conceivable that a more complicated device similar to a micromachine may be incorporated in the future.

As a possible example, as shown in FIG.
An in-ink-path rotating device 401 including a bladed roller 402 is conceivable. The method for removing the residual air bubbles 110 is as follows.
This is performed by rotating the bladed roller 402 to generate a flow. The number of the bladed rollers 402 is not particularly limited as long as the flow can be generated. Further, the shape is not limited to the blade, and any shape may be used as long as it is a protrusion that can cause a flow. The position of these devices may be any position as long as it is arranged at a position where the influence on the foaming of the main bubble is small and the residual bubbles 110 can be removed.

As another example, as shown in FIG. 7, a rotary device composed of a pulley 501 and a belt 502, or a component similar thereto, for example, a chain and a sprocket (not shown) can be considered. . Belt 50
In the shape of No. 2, a blade is provided on the surface or a protrusion similar thereto is provided. It is conceivable to rotate these rotating devices to generate a flow to remove the residual bubbles 110 from above the heating element 104.

In the above embodiment, a device for removing bubbles remaining in the ink flow path is provided in a part of the ink jet recording head, and the device moves the remaining bubbles to a position which does not affect the bubbling of the main bubble. As a result, the energy of foaming is not lost, the decrease in the amount of ink due to residual air bubbles is eliminated, the print quality can be maintained, and a high-definition image can be obtained.

As described above, in the ink jet recording apparatus using the ink jet recording head according to the present invention, the case where only one ink jet recording head for discharging a single color ink is mounted, the present invention is not limited to this. Absent.

That is, it is natural that the ink jet recording head of the present invention is used for a color recording apparatus in which a plurality of ink jet recording heads respectively corresponding to a plurality of color inks are mounted.

The typical construction and principle of the ink jet type recording head and recording apparatus according to the present invention are described in, for example, US Pat. Nos. 4,723,129 and 4,7,129.
It is preferred to use the basic principles disclosed in US Pat. No. 40,796.

This method can be applied to both the so-called on-demand type and the continuous type. Particularly, in the case of the on-demand type, the type is arranged corresponding to a sheet or a liquid path holding a liquid (ink). By applying at least one drive signal for giving a rapid temperature rise exceeding the film boiling corresponding to the recorded information to the electrothermal transducer, heat energy is generated in the electrothermal transducer, and as a result, This is effective because air bubbles in the liquid (ink) can be formed corresponding to the drive signal. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed.

When the driving signal is formed into a pulse shape, the growth and shrinkage of the bubbles are performed immediately and appropriately, so that the ejection of the liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable.

The pulse-shaped drive signal is disclosed in US Pat. Nos. 4,463,359 and 4,345,359.
No. 262 are suitable. If the conditions described in U.S. Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface described above 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 respective specifications, The present invention also includes a configuration using U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600 which disclose a configuration in which a heat acting portion is arranged in a bending region. It is. In addition, Japanese Unexamined Patent 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, or an opening that absorbs pressure waves of thermal energy is discharged. The present invention is also effective as a configuration based on JP-A-59-138461 which discloses a configuration corresponding to a unit.

Further, as a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, a combination of a plurality of recording heads as disclosed in the above-mentioned specification is used. Either a configuration satisfying the length or a configuration as one integrally formed recording head may be used.

In addition, a replaceable chip-type recording head which can be electrically connected to the apparatus main body and supplied with ink from the apparatus main body by being attached to the apparatus main body, or the ink is supplied to the recording head itself. The present invention is also effective when a cartridge type recording head having an integrated tank is used.

It is preferable to add recovery means for the recording head, preliminary auxiliary means, and the like provided as components of the recording apparatus of the present invention since the effects of the present invention can be further stabilized. If you list these specifically,
A capping unit, a cleaning unit, a pressurizing or suctioning unit, a preheating unit using an electrothermal transducer or a heating element other than these, or a combination thereof, and a preliminary ejection for performing a different ejection from recording to the recording head. Performing the mode is also effective for performing stable recording.

The ink jet recording head and the ink jet apparatus having the above-mentioned various characteristics are very suitable for high-speed recording and high image quality due to the use of multiple ejection ports.

In the embodiment of the present invention described above,
Although the ink is described as a liquid, the above-described inkjet 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. Therefore, any ink that solidifies at room temperature or below and softens or forms a liquid at room temperature or liquid when a use recording signal is applied may be used.

In addition, the temperature rise due to thermal energy can be positively prevented by using the change energy from the solid state to the liquid state of the ink, or the ink that solidifies in a standing state for the purpose of preventing the evaporation of the ink can be used. In any case, such as a method in which the ink is liquefied and ejected as an ink liquid by applying the thermal energy according to the recording signal, and a method in which the ink already starts to solidify when reaching the recording medium, etc. The use of an ink that liquefies for the first time by energy is also applicable to the present invention.

In the present invention, the recording means cloth, thread, paper,
The recording apparatus includes ink application (printing) to all ink supports that receive ink application such as sheet materials.
The present invention includes all the various information processing apparatuses or a printer as an output device thereof, and the present invention can be used for them.

[0084]

As described above, the ink jet recording head according to the present invention uses the apparatus provided in a part of the ink jet recording head to remove the remaining air bubbles by generating a flow, so that the remaining air bubbles are removed from the main air bubbles. It can be moved to a position that does not affect foaming.

As a result, the ink ejection force becomes stable,
An inkjet recording head suitable for high-speed operation and capable of obtaining a high-definition image without uneven printing can be provided.

In addition, the ink jet recording apparatus of the present invention can perform high-speed, high-quality printing with good printing quality by including the above-described ink jet recording head of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of main components of an ink jet recording head according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration of main components of an inkjet recording head according to a second embodiment.

FIG. 3 is a diagram illustrating a configuration of main components of an inkjet recording head according to a third embodiment.

FIG. 4 is a diagram illustrating a configuration of main components of an inkjet recording head according to a fourth embodiment.

FIG. 5 is a diagram illustrating a configuration of main components of an inkjet recording head according to a fifth embodiment.

FIG. 6 is a diagram for explaining a configuration of main components of another inkjet recording head.

FIG. 7 is a diagram for explaining a configuration of main components of another inkjet recording head.

FIG. 8 is a diagram illustrating a mechanism of generation of residual bubbles.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Rotation drive device 102 Wire 103 Wire passage hole 104 Heating element 105 Orifice (discharge port) 106 Wire support protrusion 107 Ink flow path 108 Common liquid chamber 110 Residual bubble 201 Jet generator 202 Jet hole 203 Tube 301 Piezo element 302 Bubbles removal Heating element 303 reciprocating object 401 rotating device in ink passage 402 roller with blades 501 pulley 502 belt 601 main foam 602 main droplet

Claims (8)

[Claims] An ink jet recording head having a heating element and discharging ink by generating bubbles in the ink by heat energy generated by the element.
An ink jet recording head comprising a flow generating device. 2. An ink jet recording head according to claim 1, wherein the flow generating device comprises a jet part. 3. An ink jet recording head according to claim 1, wherein the flow generating device is constituted by a circulating moving object. 4. The flow generator according to claim 1, wherein
An ink jet recording head, comprising: a heating element. 5. An ink jet recording head according to claim 1, wherein the flow generating device comprises a vibrating element. 6. An ink jet recording head according to claim 1, wherein the flow generating device comprises a reciprocating object. 7. An ink jet recording head, wherein the flow generating device according to claim 1 is provided in an ink flow path. 8. An ink jet recording apparatus using the ink jet recording head according to claim 1 to perform recording by discharging ink from the head onto a recording medium.