JPH0899433A - Print head for powder jet image forming device - Google Patents

Abstract

PURPOSE: To prevent generation of irregular density of images by making a first electrode, among a plurality of first electrodes, large in width in such a manner that the lesser a developer supply quantity of the electrode is assumed dependdent on its position, the larger the width of it is formed. CONSTITUTION: An insulating base plate 20, a plurality of first electrodes 21 formed on the surface of the insulating base plate 20 at the side of a toner supply roller 1, and a plurality of second electrodes 22 formed on the surface of the insulating base plate 20 at the side of a recording paper convey roller are provided. A matrix electrode is formed of the first electrodes 21 and the second electrodes 22. At intersecting positions of the first electrodes 21 and the second electrodes 22, toner passage holes 23 which pass through a print head are opened. Here, a first electrode among the first electrodes 21 is made larger in width in such a manner that the larger a distance from the toner supply roller 1 is, the larger its width is formed. That is, the first electrode is made larger in width in such a manner that the farther at the front or back from the first electrodes 21 in the center at the front and back it is, the larger its width is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head in a powder jet image forming apparatus.

[0002]

2. Description of the Related Art The applicant has already developed a powder jet image forming apparatus as shown in FIG. This powder jet image forming apparatus has a print head 2 that controls passage of toner charged with a predetermined polarity, for example, negative polarity.
A toner supply roller 1 for supplying toner to the print head 2, a recording paper transport roller 3 for guiding the recording paper P to the print head 2, and a toner transferred onto the recording paper P. And a fixing roller 4 for fixing.

As shown in FIGS. 8 and 9, the print head 2 includes an insulating substrate 20, a plurality of first electrodes 21 on the surface of which the toner supply roller 1 of the insulating substrate 20 is formed, and an insulating substrate 20. The recording paper conveying roller 3 of No. 2 is provided with a plurality of second electrodes 22 formed on the surface of the hollow. The plurality of first electrodes 21 and the plurality of second electrodes 22 form a matrix electrode. Each first electrode 21 and each second electrode 2
A toner passage hole 23 penetrating the print head 2 is formed at each intersection with the print head 2.

An on-voltage (for example -100V) and an off-voltage (for example + 300V) are selectively applied to each first electrode 21. Each second electrode 22 has an on-voltage (for example, 0 V) and an off-voltage (for example, -200 V).
V) and are selectively applied. FIG. 10 shows each first electrode 2
1 shows changes in applied voltage V1-0 to V1-7.
As shown in FIG. 10, each of the first electrodes 21 is subjected to dimic scan control, and the applied voltage is sequentially turned on at predetermined unit time intervals. Then, only when the applied voltage to both the first electrode 21 and the second electrode 22 is the on-voltage, the toner passes through the toner insertion hole 23 at the intersection thereof, and the dot printing is performed.

The recording paper P is moved in the direction perpendicular to the first electrode 21 by the recording paper conveying roller 3 and in the direction in which control by dynamic scanning of the first electrode 21 proceeds (arrow A in FIG. 8).
Is conveyed in the direction indicated by. The recording paper transport roller 3 has
A voltage of + 500V is applied. The toner supply roller 1 is grounded and its surface potential is 0V.

The print head 2 is provided with an ultrasonic vibrator 5 for applying ultrasonic vibration to the print head 2 to prevent the toner insertion hole 23 from being clogged with toner.

[0007]

By the way, the toner is supplied from the toner supply roller 1 to the print head 2 by an electric field (generated by the difference between the potential of the toner supply roller 1 and the potential of the first electrode 21 at the time of off voltage). This is performed by the action of the toner supplying electric field). However, as shown in FIG. 11, since the outer surface of the toner supply roller 1 is a curved surface, the distance between each first electrode 21 of the print head 2 and the outer surface of the toner supply roller 1 is different when printing is performed. Therefore, each first electrode 21
The toner supply electric field in the vicinity is different. Therefore,
There is a problem that uneven image density occurs.

Further, as shown in FIG. 12, since the toner supply roller 1 supplies the toner to the first electrode 21 while rotating in the direction of arrow B, the toner flows in the direction shown by arrow C. The first electrode 21 on the downstream side with respect to the toner flow direction is connected to the toner supply roller 1 on the upstream side.
Since the toner that is supplied from the printer and is not consumed is also supplied, the toner supply amount increases. On the other hand, the amount of toner supplied to the first electrode 21 on the upstream side with respect to the toner flow direction is small. Therefore, there is a problem that uneven image density occurs.

An object of the present invention is to provide a print head in a powder jet image forming apparatus capable of preventing the occurrence of image density unevenness.

[0010]

A first print head in a powder jet image forming apparatus according to the present invention comprises a plurality of first electrodes formed on the surface of a developer supply roller of an insulating layer and an insulating layer. A matrix-like electrode is formed by a plurality of second electrodes formed on the surface of the recording paper transporting section, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode. In the print head of the jet image forming apparatus, among the plurality of first electrodes,
It is characterized in that the electrode width is increased as it is assumed that the developer supply amount decreases depending on the position.

Specifically, for example, among the plurality of first electrodes, the one having a larger distance from the developer supply roller,
The electrode width is formed large. Alternatively, among the plurality of first electrodes, the electrode width that is closer to the upstream side in the rotation direction of the developer supply roller is larger.

A second print head in the powder jet image forming apparatus according to the present invention comprises a plurality of first electrodes formed on the surface of a developer supply roller having an insulating layer and a recording paper conveying section having an insulating layer. A matrix-shaped electrode is formed by the plurality of second electrodes formed on the surface.
In a print head in a powder jet image forming apparatus in which a developer insertion hole is formed at each intersection of an electrode and a second electrode, it is assumed that the developer supply amount decreases depending on the position of the plurality of first electrodes. Each of them is characterized in that the diameter of the toner insertion hole formed therein is increased.

Specifically, for example, of the plurality of first electrodes, the one having a larger distance from the developer supply roller,
The diameter of the toner insertion hole formed therein is increased. Alternatively, among the plurality of first electrodes, the one on the upstream side in the rotation direction of the developer supply roller has a larger diameter of the toner insertion hole formed therein.

[0014]

In the first print head of the powder jet image forming apparatus according to the present invention, the electrode width of the plurality of first electrodes is increased as the developer supply amount is expected to decrease depending on the position. Therefore, it is assumed that the developer supply amount will decrease,
The developer supply electric field generated by the first electrode is increased, and variation in the developer supply amount between the first electrodes is reduced.

In the second print head of the powder jet image forming apparatus according to the present invention, the one of the plurality of first electrodes, which is assumed to have a smaller developer supply amount depending on its position, has the toner inserted therein. Since the diameter of the hole is large, the smaller the developer supply amount, the smoother the developer supply to the developer insertion hole, and the more the developer supply amount varies between the first electrodes. Will be alleviated.

[0016]

Embodiments of the present invention will be described below with reference to FIGS.

1 and 2 show a first embodiment of the present invention.

FIG. 1 shows the plane of the print head 200,
FIG. 2 shows a cross section of the print head 200. 1 and 2, parts corresponding to FIGS. 8 and 9 include
The same reference numerals as in FIGS. 8 and 9 are attached.

In this print head 200, similarly to the conventional print head 2 (see FIG. 8), the insulating substrate 20 and the plurality of first electrodes 21 on which the toner supply roller 1 of the insulating substrate 20 is formed on the surface of the wadding. And a plurality of second electrodes 22 formed on the surface of the recording paper carrying roller 3 of the insulating substrate 20. A plurality of first electrodes 21 and a plurality of second electrodes 22
The matrix-shaped electrodes are constituted by. Each first
A toner passage hole 23 penetrating the print head 2 is formed at each intersection of the electrode 21 and each second electrode 22.

In this print head 200, unlike the conventional print head 2, as shown in FIGS. 1 and 2, the electrode having the larger distance from the toner supply roller 1 among the plurality of first electrodes 21 has its electrode. It has a large width. That is, the electrode width is increased toward the front or rear of the first electrode 21 in the front-rear center.

In general, of the first electrodes 21, the one having the larger distance from the toner supply roller 1 has the first electrode 21.
The electric field for toner supply generated between the toner supply roller 1 and the toner supply roller 1 becomes small. However, in this embodiment, as the distance to the toner supply roller 1 is larger, the electrode width is larger. Therefore, the distance between the first electrode 21 and the toner supply roller 1 is larger. The toner supply electric field can be increased. Therefore, the variation in the developer supply amount between the first electrodes is alleviated, and the occurrence of image density unevenness is prevented.

3 and 4 show a second embodiment of the present invention.

FIG. 3 shows the first electrode 21 of the print head 200.
FIG. 4 shows a cross section of the print head 200.
3 and 4, parts corresponding to those in FIGS. 7 and 8 are denoted by the same reference numerals as those in FIGS. 7 and 8.

In this print head 200, as shown in FIGS. 3 and 4, the larger the distance from the toner supply roller 1 among the plurality of first electrodes 21, the diameter of the toner insertion hole 23 formed therein. Has been increased. That is,
The toner insertion hole 23 has a larger diameter toward the front or rear with respect to the first electrode 21 in the front-rear center.

In this embodiment, the larger the distance from the toner supply roller 1, the larger the toner insertion hole 2 formed therein.
Since the diameter of 3 is large, it is possible to increase the toner supply to the toner insertion hole 23 of the first electrode 21 having a large distance from the toner supply roller 1. Therefore, each first
Variations in the developer supply amount between the electrodes are alleviated, and uneven image density is prevented.

FIG. 5 shows a third embodiment of the present invention.

In this embodiment, the electrode width of the plurality of first electrodes 21 that is located closer to the upstream side in the rotation direction of the toner supply roller 1 is larger.

In general, the first electrode 21 located on the downstream side with respect to the toner flow direction (rotational direction of the toner supply roller 1).
The toner supplied from the toner supply roller 1 on the upstream side thereof and not consumed is also supplied, so that the toner supply amount increases. On the other hand, the amount of toner supplied to the first electrode 21 on the upstream side with respect to the toner flow direction is small.

However, in this embodiment, the electrode width of the toner supply roller 1 is increased toward the upstream side in the rotation direction of the toner supply roller 1, so that the toner supply roller 1 is formed.
The toner supply electric field between the first electrode 21 and the toner supply roller 1 on the upstream side in the rotation direction can be increased. Therefore, the variation in the developer supply amount between the first electrodes is alleviated, and the occurrence of image density unevenness is prevented.

FIG. 6 shows a fourth embodiment of the present invention.

In this embodiment, of the plurality of first electrodes 21, the one on the upstream side in the rotation direction of the toner supply roller 1 has a larger diameter of the toner insertion hole 23 formed therein.

In this embodiment, the diameter of the toner insertion hole 23 formed in the toner supply roller 1 on the upstream side in the rotation direction is larger, so the toner supply roller 1 is on the upstream side in the rotation direction. It is possible to increase the toner supply to the toner insertion hole 23 of the first electrode 21 located at. Therefore, the variation in the developer supply amount between the first electrodes is reduced, and the occurrence of image density unevenness is prevented.

It should be noted that, with respect to each of the first electrodes 21, each distance between the toner supply roller 1 and the position of the toner supply roller 1 with respect to the rotation direction (upstream, midstream, downstream position, etc.) is taken into consideration. The electrode width or the diameter of the toner insertion hole may be changed so that the toner supply amount to one electrode 21 is constant.

[0034]

According to the present invention, the occurrence of image density unevenness can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view showing a first electrode of a print head according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the print head of the first embodiment of the present invention.

FIG. 3 is a plan view showing a first electrode of a print head according to a second embodiment of the invention.

FIG. 4 is a sectional view showing a print head according to a second embodiment of the present invention.

FIG. 5 is a plan view showing a first electrode of the print head according to the third embodiment of the present invention.

FIG. 6 is a plan view showing a first electrode of a print head according to a fourth embodiment of the invention.

FIG. 7 is a configuration diagram showing a schematic configuration of a powder jet image forming apparatus.

FIG. 8 is a plan view showing a conventional print head.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a time chart showing changes in the voltage applied to each first electrode.

FIG. 11 is a cross-sectional view for explaining that image density unevenness occurs due to a difference in distance between each first electrode and the toner supply roller.

FIG. 12 is a cross-sectional view for describing that image density unevenness occurs due to a toner flow generated by rotation of a toner supply roller.

[Explanation of symbols]

 200 print head 20 insulating layer 21 first electrode 22 second electrode 23 toner insertion hole

Claims (6)

[Claims] 1. A matrix comprising a plurality of first electrodes on which a developer supply roller of an insulating layer is formed on the wrinkle surface, and a plurality of second electrodes on which a recording paper conveying portion of the insulating layer is formed on the wrinkle surface. In a print head in a powder jet image forming apparatus in which a striped electrode is formed and a developer insertion hole is formed at each intersection of the first electrode and the second electrode, the position of the plurality of first electrodes A print head in a powder jet image forming apparatus, wherein the electrode width is formed to be larger as it is assumed that the developer supply amount will be smaller. 2. A matrix comprising a plurality of first electrodes on which a developer supply roller of an insulating layer is formed on the wrinkle surface, and a plurality of second electrodes on which a recording paper conveying portion of the insulating layer is formed on the wrinkle surface. In a print head in a powder jet image forming apparatus in which a striped electrode is formed and a developer insertion hole is formed at each intersection of the first electrode and the second electrode, the position of the plurality of first electrodes A print head in a powder jet image forming apparatus, wherein the diameter of the toner insertion hole formed in the developer is increased as the developer supply amount is supposed to decrease. 3. The powder jet image forming according to claim 1, wherein among the plurality of first electrodes, the electrode having a larger distance from the developer supply roller has a wider electrode width. Print head in the device. 4. The diameter of the toner insertion hole formed in the first electrode of the plurality of first electrodes, the larger the distance to the developer supply roller, the larger the diameter of the toner insertion hole formed therein. Print head in the powder jet image forming apparatus of. 5. The powder according to claim 1, wherein among the plurality of first electrodes, the electrode that is located on the upstream side in the rotation direction of the developer supply roller has a larger electrode width. A print head in a jet image forming apparatus. 6. The diameter of the toner insertion hole formed in the first electrode of the plurality of first electrodes is larger on the upstream side in the rotation direction of the developer supply roller. A print head in the powder jet image forming apparatus according to 2.