JPH02155758A - Electrostatic recorder - Google Patents

Abstract

PURPOSE:To stably record a satisfactory image directly on paper by feeding a sole common electrode and a plurality of spiral signal electrodes inputting a print signal in parallel in a cross-opposed manner, feeding a toner conveyor to an electrode opposing part, and passing a recording material between the toner conveyor and the spiral signal electrode. CONSTITUTION:A bias power source 5d having the same polarity as that of toner storing charge is connected to a fixed electrode 5a, and auxiliary electrodes 5c, 5c are connected together to the + side terminal of a linear electrode application high voltage power source 4f. Accordingly, switches 4en are controlled to be opened or closed in response to a print signal to form an electric field in the opposing part (intersection point) between linear electrodes 4bn and the fixed electrode 5a, toner charged in - polarity on the surface of the toner conveyor 6 is transferred along the lines of electric force on paper P to be conveyed in a direction of an arrow (b) to print one dot. In this case, since a bias voltage having the same polarity as toner charging polarity is applied to the fixed electrode 5a, a strong electric field force is obtained, and the toner can be transferred rapidly and strongly on the paper P.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrostatic recording device capable of printing on plain paper without forming an electrostatic latent image.

[Prior art]

A multi-stylus printer is known as a recording method that does not use a photoreceptor that has poor durability. A multi-stylus printer uses a large number of needle-like electrodes arranged at minute intervals to directly discharge electricity onto paper in accordance with image signals.
It forms an electrostatic latent image. After the electrostatic latent image is developed with toner, it is fixed by a fixing device.

Also, as shown in Japanese Patent Publication No. 58-54831,
There is also a device in which an electrode provided spirally on the surface of a rotating cylindrical body and a segment electrode are disposed facing each other, a sheet is conveyed between them, and a high voltage is applied between these two electrodes to form an electrostatic latent image. In this case as well, similarly to the multi-stylus printer, an electrostatic latent image is first formed on a sheet of paper, the latent image is developed with toner, and then fixed by a fixing device.

[Problems with conventional technology]

In the case of the above-mentioned multi-stylus printer, the needle electrode is adjusted to correspond to the dot density (DPI) at 0.0846
300DPl) ~ 0.1058mm (240DPI)
The needle electrodes must be arranged in the main scanning direction with an interval of

Furthermore, since the needle electrode has a fine and precise structure, even a small amount of dirt has a large negative effect on image quality.

All of the above-mentioned electrostatic recording devices have a major problem in that they cannot use plain paper. In other words, in order to form an electrostatic latent image directly on the paper, the paper must have high electrical resistance characteristics even in a high humidity environment, and for this reason, it is necessary to use special paper with a high electrical resistance agent coated on the paper surface. There is.

Such special paper is difficult to write on with pencil, ink, etc. due to its surface nature, and is therefore undesirable as paper for office use.

Therefore, as an electrostatic recording device that can use plain paper, a dielectric belt is movably stretched around the dielectric belt, and an electrostatic latent image is formed on the dielectric belt by the above-mentioned multi-stylus recording head, and then developed with toner. A method is known in which the toner image is transferred onto plain paper. This method has the disadvantage that the multi-stylus head has a fine structure and requires a process equivalent to a normal electrophotographic process, making the structure of the entire device extremely complicated. Furthermore, a high pulse voltage is usually used as the printing voltage applied to the multi-stylus head, but this is disadvantageous in terms of both cost and safety.

[Purpose of the invention]

The present invention was made in view of the problems of the prior art described above, and provides an inexpensive and safe electrostatic recording device that can stably form clear and good images on plain paper with a simple structure. The purpose is to provide

[Key points of the invention]

The above object, according to the present invention, includes a toner conveying body that carries toner on its surface and conveys the toner along a predetermined path, and a plurality of toner conveying bodies rotatably disposed opposite to each other on the toner carrying surface side of the toner conveying body and arranged on the circumferential surface thereof. a signal electrode body provided with a spiral electrode; a common electrode provided on the opposite side of the toner carrying surface of the toner transport body; and a bias power supply that applies a bias voltage having the same polarity as the charge of the toner to the common electrode. The toner on the toner carrying surface is fed between the toner conveying body and the signal electrode body by applying a voltage having a polarity opposite to the charge of the toner to the spiral electrode according to the printed information. This is achieved by providing an electrostatic recording device that is characterized by selective transfer onto a recording material.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 3.

FIG. 1 is a schematic cross-sectional view showing the overall configuration of an electrostatic recording device as an embodiment of the present invention. In the figure, reference numeral 1 denotes a paper feed cassette, which stores untreated plain paper P and is detachably installed at the lower side of the machine body. A paper feed roll 1a is disposed above the leading end of the paper feed cassette 1 in the insertion direction so as to be rotatable in the direction of the arrow.

A pair of standby rolls 2 is disposed in front of the paper feed roll 1a in the paper feed direction A, and after temporarily stopping the advance of the paper P fed out by the paper feed roll 1a and adjusting the conveyance posture, the image Re-feed in synchronization with the tip. The standby roll pair 2 of this example has a heater 2c built into the lower roll 2b, and heats and dries the paper when it is conveyed while being held between both rolls 2a and 2b that are in contact with each other. This improves the toner transfer efficiency in the printing process described later. The heater 2c may be built in the upper roll 2a, or may be built in both rolls. Further, a drying roll or a drying heater may be provided separately from the standby roll pair 2.

A static elimination brush 3 is disposed downstream of the pair of standby rolls 2 in the paper conveyance direction. The static elimination brush 3 extends over substantially the entire width direction of the paper conveyance path.
The leading edge is brought into close or sliding contact with the entire width of the paper to remove the electrical charge. Thereby, it is possible to prevent an adverse effect during printing due to the charged charges. In this example, the back side of the paper (
Although the static elimination brush 3 is brought into sliding contact with the surface (on which no image is printed), the present invention is not limited to this, and may be brought into sliding contact with the surface or both sides of the paper.

A print head section H that forms an image on paper according to a print signal is disposed downstream of the static elimination brush 3. In the print head section H, a screw ball 4 as a signal electrode body and a counter electrode 5 as a common electrode body are arranged to face each other, and an endless toner transport body 6 is rotatable so as to pass through this electrode facing part F. It is stretched. Print head section H
The configuration will be explained in detail later.

The toner conveying body 6 is made of an M electric sheet, and is rotatably stretched between two rollers 7 a + 7 b and the tip of the opposing electrode 5 to form an endless toner conveying path in an inverted triangular shape. ing. The toner conveying body 6 is driven in a circular manner in the direction indicated by arrow a, and a corona discharger 8 is disposed around the circular path, in this example, approximately at the center of the upper horizontal path, to polarize the surface of the toner conveying body 6 to a predetermined polarity ( In this example, +) is charged in a negative manner. A toner supply device 9 is provided downstream of the corona discharger 8 . The toner supply device 9 includes a toner hopper 9a and a donor roll 9b, and in this example, one-component magnetic toner t is stored in the toner hopper 9a.

As the donor roll 9b rotates in the direction indicated by the arrow, the magnetic toner t moves along the surface of the donor roll 9b while being triboelectrically charged to a polarity opposite to the charge on the surface of the toner transport body 6 (- in this example). The toner is uniformly electrostatically deposited on the surface of the toner conveying member 6.

The toner uniformly adhered to the surface of the toner conveying body 6 is conveyed to the electrode facing portion F as the toner conveying body 6 rotates. In the electrode facing section F, an electric field is formed according to the print signal, and the force of this electric field selectively transfers the toner adhering to the surface of the toner conveying body 6 onto the paper being conveyed at the same time to form an image. . The surface of the toner conveying body 6 carrying the toner that has not been transferred returns to the toner supply device 9 through a charging process as it rotates, and a new magnetic toner t is uniformly adhered thereto.

A conveyance guide 0 is provided extending horizontally on the downstream side of the print head section ②, and guides the paper on which printing has been performed to a fixing device 11 provided in front of it. Fixing device 11
consists of a heating roll lla and a pressure roll flb, and the paper is held between the two rolls and thermally fixed when being conveyed. The sheets that have been fixed are discharged from the tJi exit 12 onto the paper discharge tray 13 and stacked thereon.

As described in 2 below, in the electrostatic recording device of this example, the entire paper conveyance path from paper feeding to paper ejection is formed horizontally and approximately straight down, so the paper passing operation is generally smooth. It is smooth, and paper feeding defects such as printing defects and jams are less likely to occur.

Here, the configuration of the print head section H will be explained using FIG. 2.

The screw ball 4 includes a plurality of linear electrodes 4b1 to 4b5, which are five in this example, laid out in a spiral shape on the circumferential surface of a cylindrical base 4a. It is rotated by The linear electrodes 4bn are laid in parallel so as not to contact each other, and are wound around the circumferential surface of the base 4a by a little less than one turn. In this case, the narrower the width of the linear electrode 4b is, the more stable the electric field formation state will be.

On one side end surface of the base 4a, five side end electrodes 4cl to 4c5 for feeding power to each linear electrode 4bn are laid concentrically, and each side end electrode 4cn corresponds to the corresponding linear electrode 4.
electrically connected to bn.

A feeder 4d having five shoes (not shown) is brought into sliding contact with each side end electrode 4cn.

A high-voltage power source 4f capable of applying a high voltage having a polarity opposite to that of the toner charge (+ in this example) is connected to the feeder 4d via five switches 4el to 4e5, and is connected to the feeder 4d via five switches 4el to 4e5. The five switches 4el to 4e5 are controlled to open and close, and a secondary output voltage is selectively applied to each linear electrode 4bn by the high voltage power supply 4f.

On the other hand, the counter electrode 5 has an elongated flat plate-shaped fixed electrode 5a in the center, and has insulating plates 5b on both sides of the fixed electrode 5a.

The auxiliary electrodes 5c, 5c are fixed to each other via the toner conveyor 6, and are supported in a posture in which the longitudinal direction extends parallel to the axial direction of the screw ball 4. An electrode facing portion F is formed facing the circumferential surface.

The fixed electrode 5a is covered with a toner band? ! ! A bias power supply 5dlJ1 capable of applying a bias voltage of the same polarity as the charge (- in this example) is connected to the auxiliary electrode 5c.

5c are both connected to the + side terminal of the high voltage power supply 4f for applying the linear electrode.

Therefore, by controlling the opening and closing of each switch 4en according to the print signal, an electric field is formed at the opposing portion (intersection) between each linear electrode 4bn and the fixed electrode 5a, and the electric field line (first
The monopolarly charged toner on the surface of the toner conveying body 6 is transferred onto the paper P that is conveyed in the direction of the arrow, and one dot is printed. In this case, since a bias voltage with the same polarity as the charging polarity of the toner is applied to the fixed electrode 5a, a stronger electric field force is obtained compared to the case where only a high voltage is applied to the linear electrode 4b, and the toner is It is possible to transfer the image onto the paper P more quickly and strongly.

Furthermore, by increasing the voltage applied to the bias power supply 5d, the voltage applied to the high voltage power supply 4f can be set to a correspondingly lower value, allowing a simple and inexpensive power supply to be used, and improving operational safety.

Furthermore, since the auxiliary electrodes 5C95C are arranged in parallel on both sides of the fixed electrode 5a and the same high voltage as the linear electrode 4b is applied to each, the lines of electric force formed between each linear electrode 4bn and the fixed electrode 5a are narrowed down. It becomes approximately linear. As a result, it is possible to form sharp dots and obtain a clearer image.

In addition, since the voltage is applied via the dielectric toner conveyor 6, the electric field strength does not change much depending on the electrical resistance of the recording paper, unlike conventional multi-stylus printers, and can be used even in high humidity environments. Good print quality can always be stably obtained.

In addition, since unnecessary charges on the recording paper are also removed by the static eliminating brush 3, the print quality becomes more stable.

Here, the positional relationship between the linear electrode 4b and the fixed electrode 5a will be explained based on FIG. 3. FIG. 3 is a perspective view of the electrode facing portion F seen from above the facing electrode 5 with the linear electrode 4b expanded. The total length Ls of the fixed electrode 5a is set to be slightly longer than the effective printing width Lsu, and in this example, non-printing areas R of the same size are provided at both ends of the effective printing area Ru.
+, R+ are set. By providing the non-printing area R1 in this way, the scanning time of that area can be used as the reference timing for transmitting printing signals. Each linear electrode 4bn intersects the fixed electrode 5a at an angle θ8p.

In this case, as described above, each linear electrode 4bn is wound a little less than one turn, so it intersects the fixed electrode 5a at only one point within the effective printing width Lsu, and each linear electrode 4bn is individually wound. 1 main scanning line is printed.

Since the screw ball is rotated in the direction of arrow C in the figure,
Each of the linear electrodes 4bl to 4b5 moves from left to right in the figure and prints each main scanning line in parallel.

In this example, the three linear electrodes 4b intersect the fixed electrode 5a at the same time, and three lines are printed in parallel.

Note that the parallel lines downward to the right indicate each printing line, and each line Ln and Ln' represents a printing line formed by each linear electrode 4bn.

In FIG. 3, the linear electrode 4bl finishes printing the final driver (D) on line L1, and at the same time, the linear electrodes 4b2 and 4b3 start printing the intermediate drivers (D2 and Ds) on lines L2 and L3, respectively. The finished state is shown.

The solid line parts of the lines Ll' to L5' and the lines Ll-L3 are the parts where printing has been completed, respectively, and the lines Ll-L
The broken line part 3 represents the part that will be printed from now on. In line Ll', Ds is the first dot and Dfl is the last dot.

It should be noted that the present invention is not limited to the preferred embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, the auxiliary electrode 5c may not be commonly connected to the high voltage power source 4f, but a separate bias voltage applying power source may be provided and the auxiliary electrode 5c may be connected to this. Further, the number of linear electrodes 4b is not limited to five, but two to four, or six or more may be provided. In this case, as the number of linear electrodes 4b increases, the printing speed can be increased without increasing the rotational speed of the screw ball, which is advantageous for high-speed printing. Furthermore,
As the developer, not only magnetic toner but also non-magnetic toner can be used.

〔Effect of the invention〕

As described above in detail, according to the present invention, a single common electrode and a plurality of spiral signal electrodes to which print signals are input are arranged in parallel and cross-opposed, and a toner conveying body is run in the portion facing the electrodes. Electrostatic recording enables stable direct recording of good images on plain paper through a simple image forming process that does not form an electrostatic latent image by passing the recording material between the toner transport body and the spiral signal electrode. The device can be easily realized. In this case, the electrostatic recording device can be provided at low cost because a print head with a complicated structure such as a multi-stylus is not required, and individual image forming process members such as a developer and a cleaner are not required.

In addition, since a polar bias voltage is applied to the common electrode to amplify the strength of the electric field formed with the spiral signal electrode, it is possible to increase the toner transfer efficiency and stably obtain better images. , it is possible to use an inexpensive and safe high-voltage power supply for signals.

Furthermore, since only the minimum amount of toner required is transferred to the paper, toner consumption efficiency is improved and running costs are reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the overall structure of an electrostatic recording device as an embodiment of the present invention, FIG. 2 is a perspective view showing the print head section of the electrostatic recording device, and FIG. FIG. 3 is a developed plan view showing the positional relationship between fixed electrodes and linear electrodes in the electrostatic recording device. 1... Paper feed cassette 4... Screw pole 4b (4bn)... Linear electrode (each linear electrode) 4c (4
cn)...Side end electrode (each side end electrode) 4d...Feeder 4e (4en)...Switch (each switch) 4f...
- High voltage power source 5... Counter electrode 5a... Fixed electrode 5c... Auxiliary electrode 5d... Bias power source 6... Toner transport body 8... Charger 9... Toner supply device

Claims (1)

[Claims] a toner conveying body that carries toner on its surface and conveys the toner along a predetermined path; and a signal electrode body that is rotatably arranged opposite to the toner carrying surface of the toner conveying body and has a plurality of spiral electrodes on its circumferential surface. a common electrode provided on the opposite side of the toner carrying surface of the toner transporting body, and a bias power source that applies a bias voltage having the same polarity as the charge of the toner to the common electrode, By applying a voltage having a polarity opposite to the charge of the toner according to the information, the toner on the toner carrying surface is selectively transferred onto the recording material fed between the toner conveying body and the signal electrode body. An electrostatic recording device characterized by: