JP2763638B2 - Ink jet recording head and method of manufacturing the recording head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head and a method of manufacturing the recording head, and more particularly, to an ink jet recording head having a configuration in which ink droplets are ejected by a mechanical pressurizing unit. And its manufacturing method.

2. Description of the Related Art Various configurations of an ink jet recording head are conventionally known depending on an ink droplet ejection method, an ejection energy generation method, and the like. Among them, a so-called on-demand type recording head is often used, in which the application of the ejection signal corresponds to the ejection of the ink droplet and the ink droplet can be ejected only when necessary.

As one configuration of this on-demand type recording head,
There is a recording head having a configuration in which ink droplets are ejected by pressure generated by an electromechanical transducer such as a piezo element.
The general configuration of this recording head is that ink is filled in a tubular nozzle with a tapered tip where the discharge port is opened, and a discharge pressure is generated by applying mechanical deformation to this nozzle by a piezo element. Then, an ink droplet is ejected from the ejection port.

This so-called piezo type recording head has an advantage that halftone expression can be easily performed for recording a full-color image or the like. That is, by changing the voltage and pulse width of the electric pulse applied to the piezo element, the size (ink amount) of the ink droplet ejected according to the electric pulse can be changed. Thus, the recording density can be controlled by changing the size of the dot formed on the recording paper by the ink droplet.

[Problems to be Solved by the Invention] However, in the above-described piezo type recording head, when ink droplets are continuously discharged, minute bubbles may be generated in the nozzles. When ink droplets are ejected in such a state, the size (ink amount) and ejection direction of the ejected ink droplets are not determined due to the influence of air bubbles, or the ejection energy generated by the piezo element is extremely small. In some cases, it is deprived of the kinetic energy of the bubbles and the like, making it impossible to discharge at all.

One of the causes of the generation of such bubbles is cavitation when the ink in the nozzles flows with the ejection of the ink droplets. In particular, a dissolved gas is generally present in ink, and bubbles generated by cavitation are promoted by the dissolved gas serving as a nucleus.

Another cause of the generation of air bubbles is that air is taken in from an ejection port or an ink supply path as ink droplets are ejected.

Therefore, conventionally, an ink jet recording apparatus discharges bubbles together with ink by pressurizing the inside of a nozzle, or
A so-called ejection recovery system for sucking ink in the nozzles and sucking air bubbles together with the ink is provided.

However, in the conventional nozzle configuration, even with such a recovery system, air bubbles mixed into the ink in the nozzles cannot be completely removed, and the unremovable air bubbles may accumulate and cause the above-described ejection failure. there were.

FIG. 3 is a schematic sectional view showing a part of a conventional nozzle configuration. The figure shows the rear end of the nozzle, where 1 is the nozzle and 6 is the filter. In general, the nozzle has an integral tubular shape from the front end to the rear end where the discharge port is opened, and for example, a tubular piezo element is provided around a part thereof. In addition, as shown in the figure, the filter 6 is joined at the rear end.

By the joining of the filter 6, an edge-shaped corner portion as shown in FIG. 1B is formed in the shape of the nozzle 1. This portion is a portion where the flow velocity of the ink becomes an extremely small stagnation portion, and the above-mentioned air bubbles stay in this portion, that is, the hatched portion in the figure, and gradually become large air bubbles. It is difficult to remove such bubbles staying in this portion even if the above-described discharge recovery system is used, because the flow velocity in this portion cannot be sufficiently increased. As a result, the bubbles grown in this portion block the filter or adversely affect the propagation of the pressure wave generated by the piezo element, thereby causing a discharge failure as described above.

The present invention has been made in order to solve the above-described problem, and an object thereof is to form a joint portion with a filter at a rear end portion of a nozzle into a shape having an edge-shaped corner portion. Accordingly, it is an object of the present invention to provide an ink jet recording head capable of easily removing air bubbles in a nozzle by eliminating stagnation of air bubbles, and a method of manufacturing the recording head.

Means for Solving the Problems In order to achieve the object, the present invention provides a tubular nozzle having a discharge port for guiding ink to the tip through an ink supply unit and discharging ink droplets, and the inside of the nozzle. In an ink jet recording head that performs recording by ejecting ink droplets by applying pressure to the ink, a plurality of tubular fine passage holes for supplying ink in the direction of the ejection port are provided at an end of the nozzle on the ink supply unit side. Is formed, the filter has a passage hole region in which the plurality of fine passage holes are formed in a direction from a central portion to a peripheral portion, and the nozzle at a peripheral portion outside the passage hole region. A non-porous region formed in a portion fitted to the inner wall surface of the nozzle, and covering the non-porous region of the filter so as to narrow the inner wall portion of the nozzle fitted with the filter. The filter is characterized in that it has a wall thickness extending from the passage hole region to the discharge port of the filter as a smooth and continuous wall surface.

Here, the member constituting the inner wall of the nozzle may be a member integrated with the nozzle.

In addition, the present invention includes a tubular nozzle having a discharge port for guiding ink to the tip through an ink supply unit and discharging an ink droplet, and ejecting the ink droplet by applying a pressure to the ink inside the nozzle. In a method of manufacturing an ink jet recording head for performing recording, a filter formed with a plurality of tubular fine passage holes for supplying ink in the discharge port direction of the nozzle is joined to an end of the nozzle on an ink supply unit side, By heating the vicinity of the joining portion of the nozzle, the nozzle and the filter are welded, and the member forming the nozzle is welded to the vicinity of the filter where the fine passage hole is provided. It is characterized by having each step of extending.

[Operation] According to the above configuration, the formation of an edge-shaped corner portion in the ink flow due to the joining of the nozzle and the filter is eliminated, and the place where the air bubbles mixed into the ink in the nozzle stays is reduced. Disappears. As a result, bubbles existing in the ink are quickly removed from the nozzles along with the ink ejection or the ejection recovery operation.

Further, according to the present invention, by narrowing the inner wall portion in the vicinity of the filter joint of the nozzle, the fluid resistance to ink in that portion increases, and the fluid resistance of the filter can be secured to some extent. The diameter of the passage hole does not need to be so small. Further, by increasing the thickness of the inner wall portion near the filter joint of the nozzle, the strength of the filter joint of the filter and the nozzle can be improved.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing a main part of an ink jet recording head according to one embodiment of the present invention. In the figure, 1
Is a nozzle, and the nozzle 1 has an opening as a discharge port 4 at a front end thereof, a portion having a gradually increasing cross-sectional area from the opening, and a uniform cross-sectional area continuing from this portion to a rear end. And a tubular glass material having a portion. 2 is the nozzle 1
Is a piezo element (piezoelectric element) provided in a part of the uniform cross-sectional area portion, and the piezo element 2 has an annular shape and is joined around the nozzle 1. An electric pulse is applied to the piezo element 2 by the activation unit 7 in accordance with the recording data, and the piezo element 2 is distorted by this, whereby the nozzle 1 at the portion where the piezo element 2 is attached is deformed. Due to the deformation of the nozzle 1, the ink of the ejection energy action section corresponding to the deformed portion in the nozzle 1 is compressed. Due to this compression, the pressure wave propagates in the nozzle toward the leading end and the trailing end, and the behavior of the pressure wave and the reflected wave causes ink droplets to be ejected from the ejection port 4 at the leading end, and Ink is supplied from an ink supply path (not shown).

Reference numeral 6 denotes a filter attached to the rear end of the nozzle 1, which is made of a ceramic material. The filter 6 has a cylindrical shape so as to conform to the shape of the nozzle 1 and has a plurality of tubular holes passing through both end surfaces of the cylinder. This hole not only functions as a filter for preventing dust and air bubbles in the ink from entering the nozzle, but also functions as a fluid resistance to the ink, and maintains an appropriate ink pressure in the nozzle 1. Further, due to the presence of these holes, the pressure wave generated in the nozzle 1 due to the ejection of the ink droplet is rapidly attenuated, and the influence on the next ejection of the ink droplet is reduced.

FIG. 2 is a schematic cross-sectional view showing a part of the nozzle shown in FIG. 1, and shows a matching portion between the nozzle 1 and the filter 6 in detail.

As shown in the figure, the filter 6 has a passage hole region 6A formed with a plurality of holes as described above around the center thereof,
The area where these are formed has no holes (non-porous area)
6B6B. The non-porous region 6B exists for reasons such as maintaining the strength of the filter 6, and as shown in FIG. 3, in the conventional nozzle, the presence of the non-porous region results in an edge-shaped corner portion. Was formed.

In this embodiment, the inside of the nozzle in the non-porous region 6B is covered by extending a member forming the nozzle 1 (a portion indicated by 1A in FIG. 2), and an edge-shaped corner portion is formed in the nozzle. Not be formed. As a result, the ink flows smoothly from the filter 6 to the front of the nozzle 1 and bubbles do not stay in the nozzle.

In this embodiment, the portion 1A that covers the above-described extended land and the non-porous portion region 6B is formed by heating a glass material constituting the nozzle 1 at an end of the filter 6 as described later. That is, the glass material is melted by heating, and the melted glass material moves to the inside of the nozzle 1 while traveling along the non-porous region 6B of the filter 6 and is welded to the non-porous region 6B by the surface tension. The nozzle by such a manufacturing method can be narrowed down in its shape,
By increasing the fluid resistance in this portion, it is possible to simultaneously have the advantage that the diameter of the hole of the filter 6 does not need to be so small. Further, when the nozzle is narrowed down, the thickness of the welded portion of the nozzle with the filter 6 is increased, so that the strength is increased.

In the above embodiment, in order to prevent an edge-shaped corner portion from being formed, the member constituting the nozzle is extended to the non-porous region of the filter. However, this member is different from the nozzle member. The shape may be such that the non-porous region is covered, or the filter does not previously form an edge-shaped corner portion.

Hereinafter, a method of manufacturing the above-described nozzle and a recording experiment using the nozzle will be described.

[Experimental example 1] Glass nozzle (length 40mm, inner diameter 660μm, outer diameter 760μ)
m, discharge port diameter 50μm) and ceramic filter with hole diameter 50μm (length 0.8mm, outer diameter 620μm, non-porous part width 50μ)
m), a ceramic filter was inserted into the rear end of the glass nozzle, and the tube was heated at 720 ° C. for about 30 seconds using a heater. In the glass nozzle, the vicinity of the filter melts due to heat, and the constricted inner wall moves inward due to surface tension,
The non-porous part having a width of 50 μm was covered with glass.

When continuous recording was performed by an ink jet recording head having a nozzle formed in this manner, normal ejection could be performed for 3 hours or more.

Even if bubbles are forcibly mixed in from the discharge port side and the discharge direction temporarily becomes non-uniform, if the amount of mixed bubbles is small, perform normal discharge for several seconds. Within a short period of time, it returned to normal ejection, and even when the amount of bubbles was so large that it did not recover spontaneously, it was possible to immediately return to a normal ejection state by using the suction pump inside the recording apparatus.

[Experimental Example 2] The same glass nozzle as in Example 1 and the same ceramic filter as in Experimental Example 1 having a length of 0.7 mm other than the above were used.
Heating was performed for about 40 seconds with a heater in the same manner as in Experimental Example 1.

In the evaluation of the ejection stability by continuous recording using a recording head having such a nozzle, normal ejection can be performed for 3 hours or more, and the result of the forced air bubble mixing test is as good as in Experimental Example 1. Was.

[Experimental Example 3] The same glass nozzle as in Experimental Example 1 and the hole diameter was 60 μm.
Otherwise, the same ceramic filter as in Experimental Example 1 was used, and heating was performed with a heater in the same manner as in Experimental Example 1 for about 40 seconds.

Also in the evaluation of the ejection stability by such a head, normal ejection could be performed for 3 hours or more, and the result of the forced bubble mixing test was as good as in Experimental Example 1.

Comparative Example A filter was welded to a glass nozzle in the same manner as in Experimental Example 1 except that the same nozzle and filter as in Experimental Example 1 were used, and the heating time by the heater was set to about 13 seconds.

In the evaluation of ejection stability by continuous recording of a recording head having such a nozzle, an ejection failure state occurred in 20 to 30 minutes, and even if ejection was continued, the ejection was not recovered, and finally, a non-ejection state was reached.

Further, the recovery operation was not performed at all by performing a recovery operation using a recovery system pump, and the recoverability was very poor.

[Effects of the Invention] As is apparent from the above description, according to the present invention, the formation of an edge-like corner portion in the ink flow due to the joining of the nozzle and the filter is eliminated, and the ink inside the nozzle is There is no place for air bubbles to be trapped.
As a result, bubbles existing in the ink are quickly removed from the nozzles along with the ink ejection or the ejection recovery operation.

Further, according to the present invention, by narrowing the inner wall portion in the vicinity of the filter joint of the nozzle, the fluid resistance to ink in that portion increases, and the fluid resistance of the filter can be secured to some extent. The diameter of the passage hole does not need to be so small. Further, by increasing the thickness of the inner wall portion near the filter joint of the nozzle, the strength of the filter joint of the filter and the nozzle can be improved.

As a result, a recording head with improved ejection stability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an ink jet nozzle according to an embodiment of the present invention, and FIG. 2 is a schematic view showing the joint between the nozzle and the filter shown in FIG. 1 in detail according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing a conventional example of a joint portion between a nozzle and a filter. 1 ... Nozzle, 2 ... Piezoelectric (piezoelectric) element, 3 ... Pressure acting part, 4 ... Discharge port, 6 ... Filter, 6A ... Passage hole area, 6B ... Non-hole part area.

Claims (3)

(57) [Claims] An ink supply unit is provided with a tubular nozzle having an ejection port for ejecting ink droplets to guide the ink to the tip thereof and ejecting ink droplets by applying pressure to ink inside the nozzles. In the ink jet recording head performing, a filter having a plurality of tubular fine passage holes for supplying ink in the direction of the discharge port is interposed at an end of the nozzle on the ink supply unit side, and the filter is provided at the center. A passage hole region in which the plurality of fine passage holes are formed in a direction from the portion to the peripheral portion, and a non-porous portion formed in a portion fitted to the inner wall surface of the nozzle at an outer peripheral portion of the passage hole region A region extending to a range covering the non-porous portion region of the filter so as to narrow an inner wall portion of the nozzle fitted with the filter, to have a thickness, An ink jet recording head is characterized in that the formation of the nozzle inner wall surface of the hole area to the discharge port as a smooth continuous wall surface. 2. The ink jet recording head according to claim 1, wherein the member forming the inner wall of the nozzle is a member integral with the nozzle. 3. A recording apparatus comprising a tubular nozzle having a discharge port through which ink is guided to an end through an ink supply section and discharges an ink droplet, and the ink inside the nozzle is ejected by applying a pressure to the ink to record. In a method of manufacturing an ink jet recording head, a filter having a plurality of tubular fine passage holes for supplying ink in the direction of the discharge port of the nozzle is joined to an end of the nozzle on an ink supply unit side, By heating the vicinity of the joining portion of the nozzle, the nozzle and the filter are welded, and the member forming the nozzle is extended to the vicinity of the filter where the fine passage hole is provided. A method for manufacturing an ink jet recording head, comprising: