JPH0761029A - Powder jet image forming apparatus - Google Patents

Abstract

PURPOSE:To provide a powder jet image forming apparatus which eliminates irregularity in printing density and obtains an image having uniform density. CONSTITUTION:In a powder jet image forming apparatus, a plurality of pieces of first electrodes 21 and a plurality of pieces of second electrodes 22 are arranged in the form of a matrix with an insulating layer 20 among them, and the apparatus has a printing head 2, in which a developing powder passage hole 23 is opened at each of intersections of the first electrodes 21 and the second electrodes 22, and a developing powder feed roller 1 for feeding the developing powder charged to a predetermined polarity to the printing head 2. According to these arrangements, synchronism is maintained between the dynamic scanning control of each first electrode 21 and an AC voltage aoplied to the developing powder feed roller 1 so that a point in time when the developing powder moving between the developing powdr feed roller 1 and the first electrode 21 comes closest to the first electrode 21 coincides with a point in time when a voltage to be applied to the first electrode 21 is changed over to an ON state.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As an image forming apparatus, the applicant of the present invention has shown in FIG.
The powder jet image forming apparatus as shown in FIG. This powder jet image forming apparatus includes a print head 2 for controlling passage of toner charged to a predetermined polarity, for example, a negative polarity, a toner supply roller 1 for supplying toner to the print head 2, and a recording paper P. A recording paper feed roller 3 for guiding the print head 2 side, and a fixing roller 4 for fixing the toner transferred onto the recording paper P to the recording paper P.
It has and. An AC voltage is applied to the toner supply roller 1.

As shown in FIGS. 1 and 2, the print head 2 includes an insulating substrate 20, a plurality of first electrodes 21 formed on the surface of the insulating substrate 20 on the toner supply roller 1 side, and the insulating substrate 20. It is provided with a plurality of second electrodes 22 formed on the surface of the recording paper conveyance roller 3 side. A plurality of first electrodes 21
And the plurality of second electrodes 22 form a matrix electrode. A toner passage hole 23 penetrating the print head 2 is formed at each intersection of the first electrode 21 and the second electrode 22.

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. The respective first electrodes 21 are subjected to dimic scan control, and the applied voltage is sequentially turned on at a predetermined unit time interval. 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. 2).
Is conveyed in the direction indicated by. The recording paper transport roller 3 has
A voltage of + 500V is applied.

The print head 2 is provided with an ultrasonic vibrator 5 for applying ultrasonic vibration to the print head 2 and preventing the toner from clogging the toner insertion hole 23.

[0007]

In such a powder jet image forming apparatus, since an AC voltage is applied to the toner supply roller 1, an AC voltage is applied between the toner supply roller 1 and the first electrode 21. The toner reciprocates at the same frequency as the frequency. The amount of toner to be printed differs depending on the position of the toner between the toner supply roller 1 and the first electrode 21 at the timing when the voltage applied to the first electrode 21 is turned on (-100V), and the print density varies. Occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a powder jet image forming apparatus capable of eliminating a variation in print density and obtaining an image of uniform density.

[0009]

In a powder jet image forming apparatus according to the present invention, a plurality of first electrodes and a plurality of second electrodes are arranged in a matrix with an insulating layer interposed therebetween, and the first electrode And a second electrode, a print head having a developer insertion hole formed at each intersection, and a developer supply roller for supplying the developer charged with a predetermined polarity to the print head. By applying an AC voltage to the developer, the developer is reciprocated between the developer supply roller and the first electrode, and the potential of each first electrode is always a predetermined off voltage. , The potential of the second electrode is switched to a predetermined off voltage when there is no printing, and the potential of the second electrode is switched to a predetermined on voltage when there is printing, and both the first electrode and the second electrode have the on voltage. In the powder jet image forming apparatus in which the developer passes through the developer insertion holes at their intersections, the time when the developer moving between the developer supply roller and the first electrode comes closest to the first electrode, and It is characterized in that the dynamic scan control of each first electrode and the AC voltage applied to the developer supply roller are synchronized so that the ON voltage switching time of one electrode coincides.

When the charge polarity of the developer is negative, the midpoint of the positive voltage period of the AC voltage applied to the developer supply roller and the time when the ON voltage of the first electrode is switched are matched. , And the dynamic scan control of each first electrode is synchronized with the AC voltage applied to the developer supply roller.

When the charge polarity of the developer is positive, the midpoint of the negative voltage period of the AC voltage applied to the developer supply roller and the on-voltage switching time of the first electrode should coincide with each other. , And the dynamic scan control of each first electrode is synchronized with the AC voltage applied to the developer supply roller.

[0012]

The dynamic of each first electrode is adjusted so that the time when the developer moving between the developer supply roller and the first electrode comes closest to the first electrode coincides with the time when the ON voltage of the first electrode is switched. The scan control is synchronized with the AC voltage applied to the developer supply roller. As a result, the amount of developer supplied to the developer insertion hole at the time of printing is constant and increases, so that the print density can be made uniform and the density can be increased.

[0013]

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

FIG. 1 shows a schematic structure of a powder jet image forming apparatus.

The powder jet image forming apparatus has a print head 2 for controlling the passage of toner, a toner supply roller 1 for supplying toner charged to a predetermined polarity to the print head 2, and a recording paper P for the print head. The recording sheet feeding roller 3 is provided for guiding the recording sheet P to the second side, and the fixing roller 4 for fixing the toner transferred to the recording sheet P to the recording sheet P.

The toner conveyed by the toner supply roller 1 is assumed to be negatively charged here.
As shown in FIG. 3, a square wave voltage VBIS having a maximum value of 100V and a minimum value of -200V is applied to the toner supply roller 1.

As shown in FIGS. 1 and 2, the print head 2 includes an insulating substrate 20, a plurality of first electrodes 21 formed on the surface of the insulating substrate 20 on the toner supply roller 1 side, and the insulating substrate 20. A plurality of second electrodes 22 (control electrodes) formed on the surface of the recording / conveying roller 3 side are provided.
In this example, eight first electrodes 21 parallel to each other are arranged at equal intervals. In addition, 400 second electrodes 22 extending in a direction parallel to each other and slightly inclined with respect to a direction orthogonal to the first electrode 21 are arranged at equal intervals. That is, the eight first electrodes 21 and 400
The second electrode 22 of the book constitutes a matrix electrode of 8 rows and 400 columns.

Then, each first electrode 21 and each second electrode 22
A toner passage hole 23 penetrating the print head 2 is formed at each intersection position with and. That is, 3200 toner passage holes 23 are formed in 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. As shown in FIG. 3 showing changes in the applied voltages V1-0 to V1-7 of the first electrodes 21, the first electrodes 21 are subjected to the dynamic scan control, and the applied voltages are sequentially turned on at predetermined unit time intervals. To be voltage. 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 of the electrodes 21 and 22 is caused to pass through the toner by the electric field generated between the electrodes 21 and 22. Passes and 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. 2).
Is conveyed in the direction indicated by. The recording paper transport roller 3 has
A voltage of + 500V is applied.

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.

FIG. 5 shows the electrical construction of the powder jet image forming apparatus.

An electric clutch 11 for controlling the drive of the toner supply roller 1, an electric clutch 12 for controlling the drive of the recording paper conveying roller 3, an applied voltage generation circuit 13 for the toner supply roller 1, and an applied voltage for each first electrode 21. The switching circuit 14, the switching circuit 15 for the voltage applied to each second electrode 22, and the drive circuit 16 for the ultrasonic transducer 5 are controlled by the CPU 10. The CPU 10 includes a ROM 17 that stores the program and other data, and a RAM 18 that stores necessary data. Print dot data, an input signal from the operation unit 19, and the like are input to the CPU 10.

In the printing process, the toner supply roller 1
Also, the ultrasonic vibrator 5 is driven and an AC voltage is applied to the toner supply roller 1. In addition, the first electrode 21
Is controlled by dynamic scan. Further, each second electrode 22 is switched to the on-voltage or the off-voltage based on the print dot data.

The electric field generated between the first electrode 21 and the toner supply roller 1 causes the toner to reciprocate between the toner supply roller 1 and the first electrode 21. The potential of each second electrode 22 is an on-voltage (0 V) when there is printing and an off-voltage (-200 V) when there is no printing. When the potential of the first electrode 21 is the on-voltage (-100V) and the potential of the second electrode 22 is the on-voltage (0V), the toner passes through the toner insertion hole 23 at the intersection of the two and the recording paper P Is printed with dots.

FIG. 6 shows a simulation of the movement of toner particles in an AC electric field generated by applying an AC voltage to the toner supply roller 1.

In FIG. 6, the curve S1 shows the AC electric field, and the curve S2 shows the speed of the toner. At a point B, which is delayed by a half cycle from the time A when the AC electric field strength reaches the strength for attracting the negatively charged toner to the first electrode 21 side most, the toner speed becomes 0 and the displacement becomes maximum. That is, at the point B, the toner comes closest to the first electrode 21 side. Although the example of the AC sine wave has been described above, the timing at which the displacement of the toner becomes maximum is the same for the rectangular wave and the triangular wave. That is, the timing when the negatively charged toner comes closest to the first electrode 21 side is the midpoint of the positive voltage period of the AC voltage applied to the toner supply roller 1.

FIG. 4 shows an AC voltage VBIS applied to the toner supply roller 1, an applied voltage V1 of the first electrode 21 and an applied voltage V2 of the second electrode 22. As shown in FIGS. 3 and 4, the midpoint between the start time of the applied voltage of each first electrode 21 becoming the on-voltage (−100 V) and the positive voltage period of the rectangular wave voltage VBIS applied to the toner supply roller 1. The dynamic scan control of each first electrode 21 and the applied voltage of the toner supply roller 1 are synchronized so that B and B match.

Then, during the period when the applied voltage to the first electrode 21 becomes the on-voltage (-100 V), the second electrode 22
When the applied voltage of 2 becomes the on-voltage (0 V), the toner passes through the toner insertion hole 23 at the intersection of the electrodes 21 and 22. As described above, when the toner comes closest to the first electrode 21 between the toner supply roller 1 and the first electrode 21, the first electrode 21 becomes the on-voltage, so that the print density becomes uniform and the density becomes high. Can be achieved.

In the above embodiment, a rectangular wave is used as the alternating current applied to the toner supply roller 1, but an alternating current having another waveform such as a triangular wave or a sine wave can be used.

The present invention can also be applied to the case where a positively charged toner is used. In this case, the values of the on-voltage and the off-voltage of the first electrode 21 and the second electrode 22 are also changed according to the fact that the polarity of the toner becomes opposite. Further, the timing when the positively charged toner comes closest to the first electrode 21 is at the midpoint of the negative voltage period of the AC voltage applied to the toner supply roller 1. Therefore, the dynamic scan of each first electrode 21 is performed so that the start time of the applied voltage of each first electrode 21 becomes the on-voltage and the midpoint of the negative voltage period of the AC voltage applied to the toner supply roller 1. The control and the voltage applied to the toner supply roller 1 are synchronized.

[0032]

According to the present invention, the print density can be made uniform and high.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of a powder jet image forming apparatus.

FIG. 2 is a plan view showing the arrangement of first electrodes and second electrodes in the print head.

FIG. 3 is a time chart showing a voltage applied to each first electrode and a voltage applied to a toner supply roller.

FIG. 4 is a time chart showing applied voltages of a toner supply roller, a first electrode and a second electrode, respectively.

FIG. 5 is an electrical block diagram showing an electrical configuration of the powder jet image forming apparatus.

6 is a time chart showing a simulation of toner particle movement in an AC electric field generated by applying an AC voltage to the toner supply roller 1. FIG.

[Explanation of symbols]

 1 Toner Supply Roller 2 Print Head 3 Recording Paper Conveying Roller 10 CPU 20 Insulating Substrate 21 First Electrode 22 Second Electrode 23 Toner Insertion Hole

Claims (3)

[Claims] 1. A plurality of first electrodes and a plurality of second electrodes are arranged in a matrix with an insulating layer interposed therebetween, and a developer insertion hole is formed at each intersection of the first electrode and the second electrode. And a developer supply roller for supplying the developer charged with a predetermined polarity to the print head. By applying an AC voltage to the developer supply roller, the developer supply roller The developer is reciprocated between the first electrode and the first electrode, and the potential of each first electrode is always a predetermined off voltage. The dynamic scan control sequentially switches to a predetermined on voltage and the potential of the second electrode. Is switched to a predetermined off voltage when there is no printing, and to a predetermined on voltage when there is printing, and when both the first electrode and the second electrode are on voltage, the developer passes through the developer insertion hole at the intersection of them. Passing through the powder In the wet image forming apparatus, each of the first first electrode is adjusted so that the time when the developer moving between the developer supply roller and the first electrode comes closest to the first electrode and the time when the ON voltage of the first electrode is switched. A powder jet image forming apparatus characterized in that the dynamic scan control of the electrodes and the AC voltage applied to the developer supply roller are synchronized. 2. When the developer has a negative polarity, the midpoint of the positive voltage period of the AC voltage applied to the developer supply roller coincides with the on-voltage switching time of the first electrode. 2. The powder jet image forming apparatus according to claim 1, wherein the dynamic scan control of each first electrode is synchronized with the AC voltage applied to the developer supply roller. 3. When the developer has a positive polarity, the midpoint of the negative voltage period of the AC voltage applied to the developer supply roller coincides with the on-voltage switching time of the first electrode. 2. The powder jet image forming apparatus according to claim 1, wherein the dynamic scan control of each first electrode is synchronized with the AC voltage applied to the developer supply roller.