JPH09295422A - Printing head for powder jet image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a white line from generating on a black solid printing by a method wherein a developer penetrating hole is made at respective cross points between respective first electrodes on the developer feeding roller side surface of an insulation layer, and respective second electrodes on the recording paper carrying part side surface, and their arrangements are specified. SOLUTION: Dots which are printed by toner penetrating holes 23 at cross points between a first electrode 21-1 at the upstream end and a first electrode 21-8 at the downstream end in the recording paper carrying direction, and two second electrodes 22 being adjacent to each other, are not adjacent in the length direction of a toner feeding roller on a recording paper. In addition, a clot being printed by a toner penetrating hole 23 at a cross point between the first electrode 21-1 at the upstream end in the recording paper carrying direction, and the second electrode 22, and a dot being printed by a toner penetrating hole 23 at a cross point between the first electrode 21-8 at the downstream end and the second electrode 22, are not adjacent in the length direction of the toner feeding roller on the recording paper. The toner penetrating holes 23 are arranged so as to satisfy such conditions for a printing head.

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 First, the basic construction of a powder jet image forming apparatus will be described with reference to FIG. In the powder jet image forming apparatus, the recording paper P is guided by the guide plate 5, and the base roller (base electrode) 3,
It is discharged through the fixing roller 4. The print head 2 is disposed below the base roller 3.

Toner is supplied to the print head 2 from a toner supply unit 10. The toner is assumed to be negatively charged in this example.

The toner supply unit 10 comprises a casing 11 filled with toner, a stirring pad 6 rotatably arranged in the casing 11, and a toner supply roller 1 rotatably arranged in the casing 11. . Stirring pad 6
The toner supply roller 1 is driven to rotate in a predetermined direction by a motor (not shown).

As shown in FIGS. 4 and 5, the print head 2 includes an insulating substrate (insulating layer) 20 and a plurality of first electrodes 21 formed on the surface of the insulating substrate 20 on the toner supply roller 1 side.
And a plurality of second electrodes 22 formed on the surface of the insulating substrate 20 on the base roller 3 side. Multiple first electrodes 2
The one and the plurality of second electrodes 22 form a matrix electrode. Each first electrode 21 and each second electrode 22
A toner insertion hole 23 penetrating the print head 2 is formed at each intersection position of and.

The print head 2 is provided with an ultrasonic vibrator 50 for applying ultrasonic vibration to the print head 2 to prevent the toner insertion hole 23 from being clogged with toner.

The recording paper P is moved by the base roller 3 in a direction orthogonal to the first electrode 21 (direction shown by arrow A in FIG. 4).
Transported to

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. 6 shows the voltage V1-applied to each first electrode 21.
The change of 1-V1-8 is shown. As shown in FIG.
Dynamic scanning control is applied to each first electrode 21, 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 insertion hole 23 at the intersection thereof is applied.
The toner passes through and dot printing is performed.

For example, 0V is applied to the toner supply roller 1.
And a binary periodic voltage of 150 V is applied. A voltage of +200 V, for example, is applied to the base roller 3.

[0011]

In the above powder jet image forming apparatus, the toner supply roller 1 and the first electrode 2 are provided.
The toner is supplied from the toner supply roller 1 side onto the first electrode 21 by the electric field between the toner supply roller 1 and the first electrode 21. Then, by the electric field between the first electrode 21 and the second electrode 22, the first electrode 2
The toner accumulated on the sheet 1 passes through the toner insertion hole 23 and is transferred onto the recording paper.

The toner is supplied from the toner supply roller 1 to the print head 2 by the action of an electric field (toner supply electric field) generated by the difference between the potential of the toner supply roller 1 and the potential of the first electrode 21. . However, as shown in FIG. 7, since the outer surface of the toner supply roller 1 is a curved surface, the shortest distance between each first electrode 21 of the print head 2 and the outer surface of the toner supply roller 1 is different. For this reason, the electric field for toner supply in the vicinity of the first electrodes 21 varies between the first electrodes 21, and white streaks appear in solid black printing.

FIG. 8 shows the two second electrodes 22 on the left side of FIG.
The toner insertion holes 23 formed on the first recording medium are used to print solid black on the first row of the recording paper. The positions of the dots printed by the toner insertion holes 23 formed in each second electrode 22 in the length direction of the toner supply roller 1 are set to P1 to P1.
P8.

The first row of the recording paper is the first electrode 21 of the first stage.
When it is transported to the print position of -1, the first
Dot printing is performed by the toner insertion hole 23 located at the intersection of the electrode 21-1 and the second electrode 22. That is,
A dot is printed on the position P1.

The first row of the recording paper is the first electrode 21 of the second stage.
-2, when it is transported to the printing position,
Dot printing is performed by the toner insertion hole 23 located at the intersection of the electrode 21-2 and the second electrode 22. That is,
A dot is printed on the position P2.

By the same operation, the third line is printed on the first line of the recording paper.
~ When dot printing is sequentially performed on the positions P3, P4, P5, P6, P7 and P8 by the first electrodes 21-3 to 21-8 in the eighth stage, black solid printing in the first row of the recording paper is performed. Ends.

As shown in FIG. 7, among the first electrodes 21 of the first to eighth stages, the first electrodes 21 on both sides have a shorter shortest distance from the toner supply roller 1, so that the toner supply electric field is weaker. Become. Therefore, among the first electrodes 21 of the first to eighth stages, the first electrodes 21 on both sides have a lower image density.

Therefore, in particular, the first electrode 2 of the first stage
The print dot between the print dot on the position P1 by 1-1 and the print dot on the position P8 by the first electrode 21-8 in the eighth row becomes smaller. Conventionally, the print dot on the position P1 by the first electrode 21-1 of the first step having a small print dot and the first electrode 2 of the eighth step having a small print dot
Since the print dots on the position P8 by 1-8 are adjacent to each other on the recording paper in the direction orthogonal to the recording paper conveyance direction,
White lines occur between these positions P1 and P8.

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 white streaks in a solid black print portion.

[0020]

A print head in a first powder jet image forming apparatus according to the present invention comprises a plurality of first electrodes having a developer supply roller of an insulating layer formed on the surface of the insulating layer, and an insulating layer. A matrix-shaped electrode portion is formed by the plurality of second electrodes formed on the surface of the recording paper conveying portion, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode. The plurality of first electrodes extend in the lengthwise direction of the developer supply roller and are arranged at intervals in the recording paper conveyance direction orthogonal to the lengthwise direction of the developer supply roller. In the print head in, the developer insertion hole is arranged so as to satisfy the following three conditions (1), (2) and (3).

(1) On the recording paper, dots printed by a developer insertion hole formed at the intersection of the first electrode at the upstream end in the recording paper conveyance direction and two adjacent second electrodes are formed on the recording paper. The developer supply roller should not be adjacent in the length direction, and (2) the developer insertion hole formed at the intersection of the first electrode at the downstream end in the recording paper conveyance direction and the two second electrodes adjacent to each other. The dots to be printed are not adjacent to each other on the recording paper in the length direction of the developer supply roller, and (3) are formed at the intersection of the first electrode and the second electrode at the upstream end in the recording paper conveyance direction. On the recording paper, the dots printed by the developer insertion hole, the dots printed by the developer insertion hole formed at the intersection of the first electrode and the second electrode at the downstream end in the recording paper conveyance direction, At the developer It is not adjacent in the length direction of the sheet roller.

Specifically, the arrangement of the developer insertion holes is the above-mentioned three.
To satisfy the two conditions (1), (2) and (3),
The second electrode is formed in a polygonal line shape.

The print head in the second powder jet image forming apparatus according to the present invention comprises a plurality of first electrodes formed on the surface of the developer supplying roller of the insulating layer and a recording paper conveying section of the insulating layer. A matrix-shaped electrode portion is formed by the plurality of second electrodes formed on the surface, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode. In the print head of the powder jet image forming apparatus, one electrode extends in the lengthwise direction of the developer supply roller and is arranged at intervals in the recording paper conveyance direction orthogonal to the lengthwise direction of the developer supply roller.
The developer insertion hole is arranged so as to satisfy the following two conditions (1) and (2).

(1) A dot to be printed by the developer insertion hole formed at the intersection of the arbitrary second electrode and the first electrode at the upstream end in the recording paper conveyance direction, and the second electrode or another second electrode. That the dots printed by the developer insertion holes formed at the intersections of the two electrodes and the first electrode at the intermediate position in the recording paper conveyance direction are adjacent to each other on the recording paper in the length direction of the developer supply roller; And (2) a dot printed by a developer insertion hole formed at the intersection of the arbitrary second electrode and the first electrode at the downstream end in the recording paper conveyance direction, and the second electrode or another second electrode. And the dots printed by the developer insertion holes formed at the intersections between the first electrode and the intermediate position in the recording paper conveyance direction are adjacent to each other in the length direction of the developer supply roller on the recording paper.

Specifically, the arrangement of the developer insertion holes is the same as the above-mentioned 2
The second electrode is formed in a polygonal line shape so as to satisfy the two conditions (1) and (2).

In the print head of the second powder jet image forming apparatus according to the present invention, the "first electrode at the intermediate position in the recording paper conveyance direction" means the upstream of the plural first electrodes in the recording paper conveyance direction. The first electrode other than the first electrode at the end and the first electrode at the downstream end.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a part of the print head.
In FIG. 1, an arrow A indicates the recording paper conveyance direction.

In this print head, the toner insertion holes 23 are arranged so as to satisfy the following three conditions.

(1) First condition: a toner insertion hole formed at the intersection of the first electrode 21-1 of the first stage at the upstream end in the recording paper conveyance direction and the two second electrodes 22 adjacent to each other. Two
Dots printed by No. 3 are not adjacent to each other on the recording paper in the length direction of the toner supply roller 1 (direction orthogonal to the recording paper conveyance direction).

(2) Second condition: toner insertion hole formed at the intersection of the second electrode 22 adjacent to each other and the first electrode 21-8 at the eighth stage at the downstream end in the recording paper conveyance direction. Two
That the dots printed by 3 are not adjacent to each other on the recording paper in the length direction of the toner supply roller 1, and

(3) Third condition: Printing is performed by the toner insertion hole 23 formed at the intersection of the first electrode 21-1 of the first stage and the second electrode 22 at the upstream end in the recording paper conveyance direction. On the recording paper, the dots and the dots printed by the toner insertion holes 23 formed at the intersections of the second electrode 22 and the eighth electrode 21-8 of the eighth stage at the downstream end in the recording paper conveyance direction are formed. Must not be adjacent to the toner supply roller 1 in the length direction

Toner insertion hole 23 satisfying the above conditions
In order to realize the above arrangement, the second electrode 22 is formed in a polygonal line shape. Toner supply roller 1 for dots printed by the toner insertion holes 23 formed in each second electrode 22
The positions in the length direction of P are defined as P1 to P8.

In this example, the toner insertion hole 23 formed at the intersection of the second electrode 22 and the first electrode 21 of each step is
The second electrode 22 is formed in a polygonal line shape so as to come to the following position. That is, the toner insertion hole 23 formed at the intersection of the second electrode 22 and the first electrode 21-1 of the first stage is on the position P1. The toner insertion hole 23 formed at the intersection of the second electrode 22 and the second-stage first electrode 21-2 is located on the position P6. The toner insertion hole 23 formed at the intersection of the second electrode 22 and the first electrode 21-3 of the third stage is located on the position P3. The toner insertion hole 23 formed at the intersection of the second electrode 22 and the fourth-stage first electrode 21-4 is located on the position P8.

Second electrode 22 and first electrode 21-5 of the fifth stage
The toner insertion hole 23 formed at the intersection point with
5 is above. Second electrode 22 and first electrode 21-6 of the sixth stage
The toner insertion hole 23 formed at the intersection point with
On two. Second electrode 22 and first electrode 21-7 of the seventh stage
The toner insertion hole 23 formed at the intersection point with
It is on 7. Second electrode 22 and first electrode 21-8 of the eighth stage
The toner insertion hole 23 formed at the intersection point with
4 on.

FIG. 2 shows two adjacent second electrodes 2 of FIG.
The toner insertion hole 23 formed in
It shows that the rows are solidly printed in black.

The first row of the recording paper is the first electrode 21 of the first stage.
When it is transported to the print position of -1, the first
Dot printing is performed by the toner insertion hole 23 located at the intersection of the electrode 21-1 and the second electrode 22. As a result, a dot is printed on the position P1.

The first row of the recording paper is the first electrode 21 of the second stage.
-2, when it is transported to the printing position,
Dot printing is performed by the toner insertion hole 23 located at the intersection of the electrode 21-2 and the second electrode 22. As a result, a dot is printed on the position P6.

By the same operation, the positions P3, P are set by the first electrodes 21-3 to 21-8 at the third to eighth stages.
Dot printing is performed in the order of 8, P5, P2, P7, P4. That is, the print dots are formed on the position P1 by the first electrode 21-1 of the first stage, the print dots are formed on the position P6 by the first electrode 21-2 of the second stage, and the first electrode 2 of the third stage is formed.
1-3, a print dot on the position P3, a print dot on the position P8 by the first electrode 21-4 of the fourth stage, and a print dot on the position P5 by the first electrode 21-5 of the fifth stage, A print dot is placed on the position P2 by the first electrode 21-6 of the sixth row, a print dot is placed on the position P7 by the first electrode 21-7 of the seventh row, and a print dot is placed by the first electrode 21-8 of the eighth row. Print dots are respectively formed on P4.

The size (print density) of each print dot increases as the shortest distance between the toner supply roller 1 and each first electrode 21 decreases. Therefore, as shown in FIG. 2, print dots on positions P8 and P5 printed by the toner insertion holes 23 formed at the intersections of the first electrodes 21-4, 21-5 and the second electrode 22, The print dots on the positions P3 and P2 printed by the toner insertion holes 23 formed at the intersections of the third electrodes and the sixth electrodes 21-3, 21-6 and the second electrode 22 are: It becomes relatively large. That is, the print density becomes relatively high. Second and seventh stage first electrodes 21-2, 21-7 and second electrode 22
The print dots on the positions P6 and P7 printed by the toner insertion holes 23 formed at the intersections with and are slightly smaller. Then, the first electrodes 21 of the first and eighth stages
The print dots on the positions P1 and P4 printed by the toner insertion holes 23 formed at the intersections of −1, 21-8 and the second electrode 22 are further reduced.

In this embodiment, the positions P2 and P adjacent to the positions P1 and P4 at which the smallest print dots are printed are used.
Larger print dots are printed on 3, P5, and P8. In other words, the smallest print dots are not printed adjacent to each other. Therefore, white stripes do not occur during solid black printing as in the conventional case.

The above three conditions (1), (2) and (3) may be replaced with the following two conditions (1 ') and (2').

(1 ') A dot printed by the toner insertion hole 23 formed at the intersection of the arbitrary second electrode 22 and the first first electrode 21-1 at the upstream end in the recording paper conveyance direction, Dots printed by the toner insertion holes 23 formed at the intersections between the second electrode 22 or the other second electrode 22 and the first electrodes 21-2 to 21-7 at the intermediate position in the recording paper conveyance direction are , Toner supply roller 1 on recording paper
Adjacent in the longitudinal direction of

(2 ') A dot printed by the toner insertion hole 23 formed at the intersection of the optional second electrode 22 and the first electrode 21-8 of the eighth stage at the downstream end in the recording paper conveyance direction. , The dots printed by the toner insertion holes 23 formed at the intersections of the second electrodes 22 or the other second electrodes 22 and the intermediate positions 21-2 to 21-7 in the recording paper conveyance direction are recorded on the recording paper. Adjacent to the toner supply roller 1 in the length direction

If the above three conditions (1), (2) and (3) or the above two conditions (1 ') and (2') are satisfied, the shape of the second electrode is different from that of FIG. May be

[0046]

According to the present invention, it is possible to obtain a print head in a powder jet image forming apparatus capable of preventing the occurrence of white streaks in a solid black print portion.

[Brief description of drawings]

FIG. 1 is a partially enlarged plan view showing a print head according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining how a first row of recording paper is solidly printed in black.

FIG. 3 is a configuration diagram showing a basic configuration of a powder jet image forming apparatus.

FIG. 4 is a plan view showing a basic structure of a print head.

5 is a cross-sectional view taken along the line aa of FIG.

FIG. 6 is a time chart showing changes in applied voltage to each first electrode.

FIG. 7 is a cross-sectional view showing a positional relationship between a first electrode and a toner supply roller.

FIG. 8 is a schematic diagram for explaining how the first row of recording paper is solidly printed in black.

[Explanation of symbols]

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

Claims (4)

[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. -Shaped electrode portions are formed, a developer insertion hole is formed at each intersection of the first electrode and the second electrode, and the plurality of first electrodes extend in the length direction of the developer supply roller. In the print head in the powder jet image forming apparatus, which is arranged at intervals in the recording paper conveyance direction orthogonal to the length direction of the developer supply roller, (1) the first electrode at the upstream end in the recording paper conveyance direction , The dots printed by the developer insertion holes formed at the intersections of two adjacent second electrodes are not adjacent to each other in the length direction of the developer supply roller on the recording paper, (2) recording paper The first downstream end in the transport direction That the poles, dots each other is to be printed by the developer through-hole formed in the intersection between the two second electrodes adjacent to each other, not adjacent in the length direction of the developer supply roller in the recording paper,
And (3) A dot printed by a developer insertion hole formed at the intersection of the first electrode at the upstream end in the recording paper conveyance direction and the second electrode, and the first electrode at the downstream end in the recording paper conveyance direction. When,
Dots printed by the developer insertion holes formed at the intersections with the second electrodes are not adjacent to each other in the length direction of the developer supply roller on the recording paper. (3) Conditions (1), (2) A print head in a powder jet image forming apparatus, characterized in that a developer insertion hole is arranged so as to satisfy (3). 2. The powder according to claim 1, wherein the second electrode is formed in a polygonal line shape so that the arrangement of the developer insertion holes satisfies the above three conditions (1), (2) and (3). A print head in a jet image forming apparatus. 3. 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. -Shaped electrode portions are formed, a developer insertion hole is formed at each intersection of the first electrode and the second electrode, and the plurality of first electrodes extend in the length direction of the developer supply roller. In the print head of the powder jet image forming apparatus, which is arranged at intervals in the recording paper conveyance direction orthogonal to the length direction of the developer supply roller, (1) an arbitrary second electrode and upstream of the recording paper conveyance direction. First on the edge
The dots printed by the developer insertion holes formed at the intersections with the electrodes are formed at the intersections between the second electrode or another second electrode and the first electrode at the intermediate position in the recording paper conveyance direction. The dots printed by the developer insertion holes are
Adjacent to the lengthwise direction of the developer supply roller on the recording paper, and (2) an arbitrary second electrode and a first downstream end in the recording paper conveyance direction.
The dots printed by the developer insertion holes formed at the intersections with the electrodes are formed at the intersections between the second electrode or another second electrode and the first electrode at the intermediate position in the recording paper conveyance direction. The dots printed by the developer insertion holes are
A powder jet image forming apparatus characterized in that a developer supply roller is adjacent to a lengthwise direction of a recording paper, and a developer insertion hole is arranged so as to satisfy the two conditions (1) and (2). Print head in. 4. The powder jet image forming apparatus according to claim 3, wherein the second electrode is formed in a polygonal line shape so that the arrangement of the developer insertion holes satisfies the above two conditions (1) and (2). Print head in.