JPS62160244A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To prevent recording liquid from becoming dry during non-recording time and thereby eliminating the possibility of nozzle clogging by reversing the direction of an electromagnetic force of a liquid jet recording head when recording has been terminated and causing recording liquid to flow back to a liquid reservoir. CONSTITUTION:Electrodes 2, 3 are provided opposed to each other on the inner surface of an ink channel 1c in a nozzle 1, and further a magnet 8 is arranged so that a magnetic flux PHI which crosses almost at right angles with the ink channel 1c and an electric current I may be generated. When a switch 7 is turned ON and an electrode 2 is connected to a DC power supply voltage V+, the current I runs through a conductive ink 4 from the electrode 2 to the electrode 3, generating an electromagnetic force F. Part of the conductive ink 4 is injected from a jet nozzle 1d by the electromagnetic force F. If a minus voltage is applied to the electrode 2 after termination of printing, the electromagnetic force is reversed resulting in the accumulation of the conductive ink 4 at the tip of the ink channel 1c into an ink reservoir 20. The ink reservoir 20 has a larger cross section than the ink channel 1c with a smaller area continuous to an atmosphere. Therefore, the conductive ink 4 can be prevented from becoming dry during non-recording time and nozzle clogging be precluded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid jet recording head, and more specifically, a recording liquid or liquid ink is ejected from a liquid flow path of a nozzle and attached to a recording material to perform recording. The present invention relates to a liquid jet recording head.

[Prior Art] This type of so-called inkjet recording head includes a type that constantly jets ink liquid and an on-demand type that jets ink only when necessary. In conventional on-demand type heads, ink is ejected using the pressure generated by a piezoelectric element, or a heat source is installed, and the heat generated generates bubbles in the ink, and the pressure generated when the bubbles expand is used to eject ink. The bubble jet method is known.

[Problems to be Solved by the Invention] However, in all of the above-mentioned conventional methods, the direction of movement (driving) of ink is fixed only from the rear end of the nozzle to the jetting port at the tip of the nozzle, and can be changed arbitrarily. Ink cannot be moved in the direction of .

For this reason, during non-recording, the ink tip surface, so-called meniscus, in the ink flow path of the nozzle is located very close to the ejection port and is directly exposed to the outside air. Therefore, the tip of the ink tends to dry and solidify, which tends to cause ink clogging in the renozzle. In order to eliminate ink clogging, it is necessary to install additional mechanisms such as a suction pump that sucks and removes the ink at the tip of the nozzle, which complicates the structure of the recording device, increases the number of parts, and increases manufacturing costs. There was a problem.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, a conductive recording liquid is supplied and a liquid reservoir having a larger cross-sectional area than other parts is formed in the middle part. a liquid flow path of a nozzle; a means for passing a current through the liquid in the liquid flow path in a direction substantially perpendicular to the liquid flow path; and a means for generating a magnetic flux substantially perpendicular to the liquid flow path and the current. the liquid is injected from the tip of the liquid flow path by switching the direction of an electromagnetic force generated between the magnetic flux and the current and acting on the liquid in the liquid flow path by reversing the current; The liquid was allowed to flow back into the liquid reservoir.

[Function] According to this configuration, recording is performed by jetting the recording liquid from the tip of the liquid flow path of the nozzle, and after recording is completed, the current is reversed to direct the recording liquid at the tip of the liquid flow path into the liquid flow path. If the recording liquid is caused to flow backward into the liquid reservoir, the leading end surface of the recording liquid in the liquid flow path will come into indirect contact with the outside air at the liquid flow path tip, that is, the liquid pool drawn inward from the injection port. The liquid reservoir has a larger cross-sectional area than other parts of the flow path, and the area communicating with the outside air is small compared to the volume of the recording liquid collected there. Therefore, drying of the recording liquid during non-recording can be suppressed, and nozzle clogging caused by this drying can be prevented.

[Example] Hereinafter, the present invention will be described in detail with reference to the attached drawings, but first, the principle of ink jetting of a liquid jet recording head, that is, an inkjet head according to the present invention will be explained.

FIG. 1 shows its basic configuration.

In the present invention, the nozzle indicated by the symbol l in FIG.
Use. Further, on the inner surface of the ink flow path IC of the nozzle L, an electrode 2.
3 are provided facing each other. Electrode 2 is connected to DC power supply voltage V+ via switch 7, and electrode 3 is grounded. Furthermore, a magnet or electromagnet (not shown) is placed near the nozzle to generate a magnetic flux Φ directed toward the back of the paper as shown by the blunder mark, that is, a magnetic flux Φ that is almost perpendicular to the ink flow path 1c and the current ■.
to occur.

With this configuration, when the switch 7 is turned on to connect the electrode 2 to the DC power supply voltage V+, a predetermined amount of current I flows from the electrode 2 to the electrode 3 through the conductive ink 4.

Here, according to Fleming's left-hand rule, an electromagnetic force indicated by symbol F is applied to the part where the current I of the conductive ink 4 flows in the ink channel IC in the direction indicated by the arrow, that is, along the ink channel IC, and the tip of the ink channel. It acts in the ink ejection direction toward the ejection port 1d. Let the magnetic flux density of magnetic flux Φ be B, and electrode 2.
Assuming that the distance between 3 is 1, the magnitude of electromagnetic force F is F=BX×work.

A part of the conductive ink 4 is ejected from the ejection port 1d by this electromagnetic force F.

Then, when the switch 7 is turned off, the electric current becomes zero, the electromagnetic force F becomes zero, and the ejection of the conductive ink 4 stops, and a part of the previously ejected conductive ink 4 becomes an ink droplet 4a.

By turning the switch 7 on and off in this manner, the ejection of the conductive ink 4 can be controlled.

Furthermore, if a negative voltage of the opposite polarity is applied to the electrode 2 to reverse the direction of the current I, the direction of action of the electromagnetic force F becomes opposite to that described above, and the conductive ink 4 can be caused to flow backwards.

Next, the present invention will be explained in detail.

Figure 2 is an exploded perspective view showing the structure of the inkjet head (hereinafter referred to as head) according to this embodiment.1 The head of this embodiment is constructed by stacking each member shown in the figure one above the other and fixing them together. .

Starting from the bottom member, the reference numeral 9 is a yoke that guides the magnetic flux Φ described above, and is made of a high magnetic permeability material such as pure iron and has a substantially U-shaped cross section.

A magnet 8 is fixed on the bottom surface of the recess 9a of the yoke 9.

The magnet 8 is formed into a rectangular plate shape from rare earth metal or the like, and is magnetized in the thickness direction as shown by the pole symbols N and S and the arrow indicating the direction of magnetic flux.

On the magnet 8, there is a rectangular glass substrate 1a constituting a nozzle,
lb is fixed. A groove is formed as an ink channel IC on the upper surface of the lower glass substrate 1b, and a groove is formed as an ink channel IC on the upper surface of the lower glass substrate 1b.
In the middle part of c, the cross-sectional area is larger than other parts, and as will be described later, there is an ink reservoir 2 in which conductive ink 4 is collected after recording is completed.
0 is formed. The upper side of the ink flow path 1c is closed by a glass substrate la.

In addition, electrodes 2 are placed on both sides of the area from the tip of the ink flow path IC, which is the injection port in the front in the figure, to the rear end of the ink reservoir 20.
．． 3 is provided.

The electrodes 2 and 3 are connected to a DC power supply circuit (not shown) via a switch and a polarity switching circuit each made of a semiconductor element (not shown). The polarity switching circuit is a bipolar drive circuit that reverses the positive and negative polarities of the connection of the electrodes 2.3 to the DC power supply circuit, and since a very common one can be used as is, we will explain its specific configuration below. is omitted.

Furthermore, a rectangular plate-shaped yoke 10 made of a high magnetic permeability material, like the yoke 9, is fixed on the upper glass substrate la.

Such a laminated structure constitutes the head of this embodiment whose cross section is shown in FIG. 3, and the above-mentioned conductive ink 4 is supplied to the ink channel IC of the head.

With this structure, the magnetic flux generated from the magnet 8 flows through loops lla and flb shown by arrows, perpendicular to the ink flow path 1c, and also perpendicular to the line connecting the electrodes 2 and 3.

Therefore, turn on the above-mentioned switch (not shown), connect electrode 2 to the positive output of the DC power supply and electrode 3 to the negative output via the polarity switching circuit, and apply current from electrode 2 to electrode 3 through conductive ink 4. When flowing, the magnetic flux is orthogonal to this current, and as described above, an electromagnetic force acts on the conductive ink 4 in the ink flow path IC in a direction to jump out from the paper surface toward the front, and the conductive ink 4 is jetted. In the same manner as described above, the ejection of conductive ink can be controlled by turning the switch on and off, and recording can be performed.

After the recording is completed, the electrode 2.
By reversing the connection polarity of electrode 3, the current can be transferred to electrode 2.
When the conductive ink 4 is caused to flow from the ink flow path IC to the electrode 3 in the opposite direction to that described above, the direction of the electromagnetic force acting inside the ink flow path IC becomes opposite to the above direction, and the conductive ink 4 at the tip of the ink flow path IC flows into the ink reservoir. It flows backwards to 20. Behind the ink reservoir 20, the electrode 2
．． 3 is not disposed and no electromagnetic force is applied, so the conductive ink 4 at the tip remains in the ink reservoir 20.

In this way, the front end surface of the conductive ink 4 in the ink flow path IC comes into indirect contact with the outside air through the ink reservoir 20 drawn inward from the injection port ld at the front end of the ink flow path IC. The ink reservoir 20 has a larger cross-sectional area than other parts of the ink flow path IC, and the surface area communicating with the outside air is small compared to the volume of the conductive ink 4 collected therein. Therefore, the conductive ink 4 does not dry during non-recording. It is possible to prevent nozzle clogging caused by this drying. This also eliminates the need for mechanisms such as ink suction pops to clear nozzle blockages.

Further, according to the configuration of this embodiment, the above-mentioned electromagnetic force acts directly on the conductive ink 4.

Therefore, there is no loss or time delay in transmitting the force for ejecting conductive ink during recording, so that a high ejecting force can be efficiently obtained with respect to the applied current, and good frequency response characteristics can be obtained.

[Effects] As is clear from the above description, the liquid jet recording head according to the present invention has a liquid flow path of a nozzle to which a conductive recording liquid is supplied, and a liquid in the liquid flow path. The liquid flow path includes means for passing a current in a direction substantially perpendicular to the liquid flow path, and means for generating a magnetic flux that is substantially perpendicular to the liquid flow path and the current. The direction of the electromagnetic force acting on the liquid inside the nozzle is switched by reversing the current so that the liquid is either injected from the tip of the liquid flow path or flows back into the liquid reservoir. It is possible to suppress drying of the recording liquid, prevent nozzle clogging caused by this drying, and improve the reliability of the head. Furthermore, since an additional mechanism such as a suction pump for clearing the blockage is not required, the manufacturing cost of the entire recording apparatus can be significantly reduced.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the basic structure of the head of the present invention, Fig. 2 is an exploded perspective view showing the structure of the head according to the embodiment of the invention, and Fig. 3 is the structure of the head of the embodiment and the flow of magnetic flux. FIG. l... Nozzle la, lb... Glass substrate IC... Ink channel 2.3... Electrode 4...
Conductive ink 5...Tube 7...Switch
8...Magnet 9.10...Yoke 20.
...1 ink reservoir and 1 bow! ``The 40th day of the month'' with a blank composition

Claims (1)

[Claims] A liquid flow path of a nozzle in which a conductive recording liquid is supplied and a liquid reservoir having a larger cross-sectional area than other parts is formed in the middle part, and a liquid flow path that is approximately equal to the liquid flow path with respect to the liquid in the liquid flow path. It has means for passing a current in a direction perpendicular to the liquid flow path, and means for generating a magnetic flux substantially orthogonal to the liquid flow path and the current, which is generated between the magnetic flux and the current and acts on the liquid in the liquid flow path. A liquid jet recording head characterized in that the direction of the electromagnetic force is switched by reversing the current so that the liquid is jetted from the tip of the liquid flow path or flows back into the liquid reservoir.