JPH07290752A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent the positional shift of formed dots and missing dots by making the gap between a recording head and a recording material constant. CONSTITUTION:In an image forming apparatus equipped with a recording head 23 selectively passing toner through toner passing holes 33 by utilizing the control electric field corresponding to image data and a toner supply means 24 supporting the toner 22 on the surface thereof to supply the same to the position of a recording head 23 and transferring the toner passed through the toner passing holes 33 to a recording material 28, aperture parts 34 are provided to a back electrode 29 and air is sucked from the aperture parts 34 by an air suction means 35 to bring the recording material into close contact with the back electrode to keep the gap between the recording head 23 and the recording material 28 constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a page printer or a copying machine which prints according to image data by dots.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image carried on a latent image carrier such as a photosensitive drum by using modulated light in a dot pattern according to an original image or image information can be transferred using a developing device. A method generally referred to as an electrophotographic method, in which the visualized toner image is transferred to a recording material after being visualized, is widely used in printers, copiers and other image forming apparatuses.

However, in such an electrophotographic system, since the toner image on the latent image carrier is transferred onto the recording material by the transfer means including the electrostatic forming means, the image information is converted into optical information. In addition to the means, the latent image carrier, the transfer means, etc., a means for removing the residual toner adhering to the latent image carrier, a means for removing the charges written in the latent image carrier and recharging are required. This leads to larger equipment and higher cost.

As a solution to these problems, there is a printing technique known as a toner flying recording system among electrostatic printing techniques. The toner flying recording method is a method in which the toner carried on a toner supply means is directly transferred onto a recording material in a dot pattern according to image information, and is disclosed in US Pat. No. 3,689,935.

In US Pat. No. 3,689,935, an insulating layer, a continuous layer made of a conductive material provided on one side of the insulating layer (hereinafter, referred to as a conductive continuous layer), and another side of the insulating layer are provided. The provided partial layer made of a conductive material (hereinafter,
And a conductive partial layer) and at least one row of toner passage holes penetrating the central portion of the conductive partial layer, the electrostatic line printer is disclosed.

In this electrostatic line printer, a constant potential is applied to the conductive continuous layer and a potential is selectively applied to the conductive partial layer according to image information, so that the toner is passed through the toner passage hole. Pass through to form an image.

An image forming apparatus using a conventional toner flying recording system will be described below. 9 is a schematic configuration diagram of a conventional image forming apparatus, FIG. 10 is an enlarged view of a toner flying portion of the conventional image forming apparatus, and FIG. 11 is a plan view of a recording head of the conventional image forming apparatus. In FIGS. 9 and 10, a sponge roller 3 is pressed against a toner supply roller 2 disposed inside the toner storage tank 1, and a layer is formed on the downstream side in the circumferential direction of the toner supply roller 2 with a constant pressure. The thickness regulating member 4 is pressed. Further, a back electrode 5 is arranged facing the toner supply roller 2 with the recording head 6 interposed therebetween. The recording head 6 is composed of three layers of a conductive continuous layer 7, a polyimide intermediate insulating layer 8 and a conductive partial layer 9, and the conductive continuous layer 7 is disposed on the toner supply roller 2 side. The gap between the toner supply roller 2 and the recording head 6 is 100 to 50.
0 μm, the gap between the recording head 6 and the back electrode 5 is 400
It is configured to be maintained at ˜1000 μm. Reference numeral 21 denotes a fixing roller that heats and pressure-bonds the toner 10 that has flown and adhered to the recording material 11.

The operation of the image forming apparatus configured as described above will be described below. The toner 10 in the toner storage tank 1 is pressed against the sponge roller 3 and the toner supply roller 2, and the sponge roller 3 rotates in the opposite direction to the toner supply roller 2, so that the toner supply roller 2 is frictionally charged.
Supplied on. The toner 10 adhering to the toner supply roller 2 is conveyed to the position of the layer thickness regulating member 4 by the toner supply roller 2, and is 10 to 50 μm by the layer thickness regulating member 4.
Is regulated to a constant layer thickness, is charged again at the same time, and is conveyed by the toner supply roller 2 to a position facing the recording head 6.

A constant potential having a reverse polarity to that of the toner 10 is applied to the conductive continuous layer 7 of the recording head 6, and the conductive partial layer 9 is a conductive continuous layer when dots are formed according to image information. A potential higher than 7 and having a polarity opposite to that of the toner 10 is applied, and when dots are not formed, a potential having the same polarity as the toner 10 is applied. A potential having a polarity opposite to that of the toner 10 applied to the back electrode 5 is higher than that applied to the conductive partial layer 9 during dot formation. The toner 10 transported to the facing portion of the recording head 6 is subjected to an electric field generated when a potential is applied to the conductive continuous layer 7, the conductive partial layer 9 and the back electrode 5 when forming dots, by the toner supply roller. The force generated in the direction from 2 to the back electrode 5 acts and fly onto the recording material 11. Further, when dots are not formed, the electric field direction inside the toner passing hole 12 is reversed by applying a potential having the same polarity as the charging polarity of the toner 10 to the conductive partial layer 9, so that the conductive partial layer of the toner passing hole 12 is formed. Prevent the toner 10 from passing through 9 parts.

10 and 11, the recording head 6 has a control circuit 13 for generating a signal in accordance with image information, and a drive circuit 1 for applying a potential based on a signal from the control circuit 13.
4 is connected. The toner passage holes 12 are arranged in a plurality of rows in order to represent the dots as a continuous linear image, and the control timing is changed for each of the toner passage hole groups 15 to 19 to form the line image 20. ing.

The above operation is continuously carried out, and the toner 10
By fixing the flying recording material 11 with the fixing roller 21 shown in FIG. 9, a desired image can be obtained.

[0012]

However, in the above-mentioned conventional structure, the gap between the toner supply roller 2, the recording head 6 and the back electrode 5 can be managed as shown in FIG. 12, but the recording material 11 is warped and wrinkled. And the like, the gap between the surface of the recording head 6 and the recording material 11 fluctuates, and the recording material 1 of the dots formed on the recording material 11
The distance from the tip of No. 1 shifted from D to d, and defects such as dot size fluctuations occurred, leading to deterioration of print quality. Further, part of the toner 10 that has flown to the toner passage hole 12 due to environmental changes, dust, etc. adheres to the toner passage hole 12,
As a result, dots formed on the recording material 11 become small, or dots are not formed at all, resulting in a drop in printing quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus having good print quality.

[0014]

In order to achieve this object, the image forming apparatus of the present invention has a first feature that it is provided with an adhering means for adhering the recording material to the back electrode.

Here, the close contact means is composed of an opening provided in the back electrode and an air suction means for sucking air through the opening.

As another construction of the contact means, a recording material charging means for charging the recording material provided on the upstream side in the conveying direction of the recording material to a polarity different from the voltage applied to the back electrode is provided. Is.

A second characteristic is that the recording material does not exist between the toner passage hole of the toner control means and the opening provided in the back electrode, or after the recording material conveyance operation is started. Before the leading edge of the recording material is conveyed between the toner passage hole and the opening, air is sucked through the opening by the air suction means.

Here, the opening of the back electrode can be provided so as to face the toner passage hole of the toner control means.

As a third feature, the shape of the opening for sucking air by the air suction means provided on the back electrode is a slit shape which is long in the direction perpendicular to the conveying direction of the recording material, and the back electrode is formed. Is movable in the conveying direction of the recording material, and is provided with a control means for controlling the timing of the printing operation so that printing is not performed by the toner passage hole of the plurality of toner passage holes that is opposite to the opening. .

A fourth characteristic is that the back electrode has a cylindrical shape that is rotatable long in the direction perpendicular to the conveying direction of the recording material, has an opening on its surface, and faces the toner passage hole in the circumferential direction. The air is sucked by the air suction means at a portion.

[0021]

According to the first aspect of the present invention, since the back electrode and the recording material can be brought into close contact with each other to perform the printing operation, the gap between the toner control means and the recording material can be kept constant. Becomes

Further, air suction means is used as a contact means for bringing the back electrode and the recording material into close contact with each other, or air is sucked from an opening provided in the back electrode, or a toner passage hole is provided in a path for conveying the recording material. The recording material charging means provided on the upstream side of the position facing the recording material causes electric charges to be retained on the surface of the recording material and an electrostatic attraction force to act between the recording material and the back electrode. It is possible to keep the gap constant even at the tip of the.

Further, according to the second feature of the present invention, when the recording material is not present between the toner passage hole and the opening, the air suction means is provided from the opening provided on the back electrode. By sucking the air, it is possible to remove the toner, dust, and the like attached to the toner passage holes due to environmental changes and dust.

Further, the timing at which air is sucked by the air sucking means from the opening provided on the back electrode is set to be higher than that when the leading edge of the recording material reaches the position facing the toner passage hole after the conveyance operation of the recording material is started. By setting the timing to be early, the toner passage hole can be cleaned for each printing operation.

The air suction speed can be increased by providing the opening of the back electrode so as to face the toner passage hole of the toner control means.

Further, according to the third aspect of the present invention, the timing of the printing operation is controlled so that the printing is not performed by the toner passage hole of the plurality of toner passage holes that is opposite to the opening. The dispersion of the electric field generated between the toner passage hole and the back electrode can be suppressed, and the dots formed on the recording material can be converged.

Further, according to the fourth feature of the present invention, air is sucked at the portion facing the toner passage hole in the circumferential direction, so that the portion where the recording material faces the toner passage hole is sucked. It is possible to prevent the recording material from being sucked when the recording material is sucked by the back electrode and passes through the portion where the recording material faces the toner passage hole.

[0028]

【Example】

(Embodiment 1) An image forming apparatus according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged view of a toner flying portion of an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, 22 is a toner, and this toner 22 is a general powder used in an electrophotographic image forming apparatus. Body toner is all right. Reference numeral 23 is a recording head for controlling the flight of the toner 22 according to image information, 24 is a toner supply unit for conveying the toner 22 to a position facing the recording head 23, and 25 is toner attached to the surface of the toner supply unit 24. A layer thickness regulating member for making the layer thickness of 22 constant,
An image processing circuit 26 generates a signal according to image information,
Reference numeral 27 denotes a drive circuit that controls the voltage applied to the recording head 23 according to the signal output from the image processing circuit 26, and 28.
Is a recording material such as paper or resin sheet, 29 is a recording head 23
Is a back electrode for guiding the toner 22 passing through the toner passage hole 33 of the recording head 23 to the recording material 28, which is fixed with a gap between the recording head 23 and the toner supply means 24 and the recording head 23, and the recording head 23 and the rear surface. The gap with the electrode 29 is 100 μm and 500 μm depending on the supporting member.
The recording head 23 is held by the toner supply means 24.
5 row electrodes 30 parallel to the longitudinal direction and column electrodes 32 of a plurality of columns intersecting with the row electrodes 30 through a 25 μm-thick polyimide insulating layer 31, and the row electrodes 30 intersect the column electrodes 32. A toner passage hole 33 is provided in the formed portion in parallel with the longitudinal direction of the toner supply means 24, and the row electrode 30 and the column electrode 32 are provided.
The image processing circuit 26 and the drive circuit 27 according to the image information.
Therefore, when forming dots, 90 V is applied to the row electrode 30,
A voltage of 70 V is applied to the column electrode 32, and a voltage of -50 V is applied to the row electrode 30 and a voltage of -50 V is applied to the column electrode 32 when dots are not formed. The back electrode 29 is provided with an opening 34 penetrating from the front surface to the back surface, and an air suction means 35 using an electric fan or a pump provided in close contact with the back surface of the back electrode 29 is used to pass through the opening 34 to the back surface. By sucking the air on the front surface side of the electrode 29 toward the back surface side, the recording material 28 is transferred to the toner passage hole 33 of the recording head 23.
It comes into close contact with the back electrode 29 when it is conveyed to a position opposed to. As described above, the gap between the recording head 23 and the recording material 28 can be kept constant, and problems such as misalignment of dots formed on the recording material 28 can be prevented.

(Embodiment 2) FIG. 2 is an enlarged view of a toner flying portion of an image forming apparatus according to a second embodiment of the present invention.
In the figure, 36 is a charging means such as a scorotron which is generally used as a charger of an electrophotographic image forming apparatus, and has the same polarity as that of the toner 22 uniform on the surface opposite to the recording surface of the recording material 28 conveyed. Gives an electrostatic charge of. Reference numeral 37 denotes a back electrode, which has a polarity opposite to that of the toner 22 and a voltage of about 1 kV is applied to the back surface of the recording material 28.
Comes into close contact with the back electrode 37 when it is conveyed to a position facing the toner passage hole 33 of the recording head 23. As described above, the gap between the recording head 23 and the recording material 28 can be kept constant, and problems such as positional deviation of dots formed on the recording material 28 can be prevented.

(Embodiment 3) An image forming apparatus according to a third embodiment of the present invention will be described below. FIG. 3 is an enlarged view of the toner flying portion of the image forming apparatus according to the third embodiment of the present invention. In FIG. 3, 38 is a photo interrupter and whether or not the recording material 28 is present at a position facing the recording head 23. When the recording material 28 exists, the digital signal "0" is output, and when the recording material 28 does not exist, "1" is output as the recognition signal. Reference numeral 39 is a drive circuit, which turns on the electric fan or pump of the air suction means 35 when the recording material 28 does not exist (when the recognition signal is "1") in accordance with the recognition signal output from the photo interrupter 38, and turns on the recording material. When 28 is present (when the recognition signal is "0"), the electric fan or pump of the air suction means 35 is turned off. As described above, the toner 22 and dust adhered to the toner passage holes 33 due to environmental changes and dust can be removed, and the dots formed on the recording material 28 become small, or dot dropouts that are not formed at all occur. Can be prevented.

Here, when the shape of the opening 34 provided in the back electrode 29 is made to be a portion facing the toner passage hole 33 of the recording head 23 as shown in FIG. 4, the toner passage hole is further caused by environmental change or dust. It is possible to efficiently remove the toner 22 and dust attached to the 33. Further, as shown in FIG. 5, by providing the first photo interrupter 40, the second photo interrupter 41, and the OR circuit 42, the recording material 28 sets the timing for turning on the air suction means 35 to the first and the second. Of the photo interrupters 40 and 41, the operation noise of the air suction means 35 can be eliminated except during the printing operation, and the recording material 28 is the toner of the recording head 23. Since air is sucked before reaching the position facing the passage hole 33, it is possible to previously remove the toner 22 and dust attached to the toner passage hole 33 due to environmental changes and dust.

(Embodiment 4) An image forming apparatus according to a fourth embodiment of the present invention will be described below. FIG. 6 is a plan view of the opening of the back electrode of the image forming apparatus in the fourth embodiment of the present invention, and FIG. 7 is an enlarged view of the toner flying portion of the image forming apparatus in the fourth embodiment of the present invention. 6 and 7, the back electrode 43 is formed in a cylindrical shape which is long in the longitudinal direction of the toner supply means 24 described in the first embodiment and the like, and has a long and narrow slit parallel to the longitudinal direction of the toner supply means 24 on the surface thereof. A circular opening 34 is provided so as to penetrate the outside and the inside, and is rotated at the same speed as the conveying speed of the recording material 28 in the arrow A direction during the printing operation by a motor (not shown).

The openings 34 are provided in the back electrode 43 at intervals so as to oppose to the five row electrodes 44 to 48 on the recording head 23, and the row electrodes are always provided even if the back electrode 43 rotates. At least one of the electrodes 44 to 48 does not face the opening 34. On the other hand, a detection hole 49 penetrating the recording head 23 is provided on an extension line of the row electrode 46 on the recording head 23, and a light emitting means 50 is provided above the detection hole 49 so as to face the detection hole 49. On the back side of the back electrode 43 (the side not facing the recording head 23), when the detection hole 49 and the opening 34 of the back electrode 43 overlap, the light emitting means 50 is provided.
The light receiving means 51 is provided at a position where the light from
When the detection hole 49 and the opening 34 of the back electrode 43 overlap,
The light from the light emitting means 50 reaches the light receiving means 51, and the light receiving means 51 outputs a digital signal “0” to the drive circuit 27 as a position detection signal of the opening 34. In addition, the detection hole 4
9 and the opening 34 of the back electrode 43 do not overlap, the light from the light emitting means 50 is blocked by the back electrode 43 and does not reach the light receiving means 51, and the light receiving means 51 digitally detects the position detection signal of the opening 34. Drive circuit 2 for signal "1"
Output to 7.

The drive circuit 27 which receives the position detection signal output from the light receiving means 51 is the row electrodes 45 and 47 when the position detection signal is "0", and the row electrodes when the position detection signal is "1". By controlling the printing operation with 44, 46, and 48, the control electric field formed by the recording head 23 and the back electrode 43 is prevented from diffusing, and the recording material 2
It is possible to prevent the dots formed on the surface 8 from diffusing and deteriorating the printing quality.

(Fifth Embodiment) An image forming apparatus according to a fifth embodiment of the present invention will be described below. FIG. 8 is an enlarged view of the toner flying portion of the image forming apparatus according to the fifth embodiment of the present invention. In FIG. 8, the back electrode 52 is formed in a cylindrical shape elongated in the longitudinal direction of the toner supply means 24, and is formed on the surface thereof. Has an opening penetrating the outside and the inside, and is rotated by a motor (not shown) in the direction of arrow A at the same speed as the conveying speed of the recording material 28 during the printing operation. Reference numeral 53 is an area limiting means in which a soft rubber blade is attached to the tip of a resin flat plate, and 54 is an air suction means using an electric fan or a pump (not shown).

When the air suction means 54 is operated in FIG. 8, air is sucked from the outside to the inside of the back electrode 52, but the area effective for the air suction by the area limiting means 53 is the area 55 shown by hatching in FIG. Can be limited to only. Since the area limiting means 53 is fixed so as to be in contact with the back electrode 52 via a soft rubber blade,
Even if the back electrode 52 rotates, the area 55 is always the recording head 2
It does not move from the position facing 3.

As described above, even if the back electrode 52 is rotated in a cylindrical shape for the purpose of also serving as a sheet conveying roller, the area for sucking air can be limited to only the portion facing the toner passage hole 33 of the recording head 23. , Recording material 28
Can be prevented from being wrapped around the back electrode 52 after passing through the portion facing the toner passage hole 33.

[0038]

According to the first aspect of the present invention, since the back electrode and the recording material can be brought into close contact with each other to perform the printing operation, the gap between the toner control means and the recording material is kept constant. Even if the recording material warps or the like and the gap between the toner control unit and the recording material fluctuates, the back electrode and the recording material are surely brought into close contact with each other. It is possible to suppress the occurrence of defects such as positional deviation of dots formed on the material and fluctuations in dot size.

Further, air suction means is used as a contact means for bringing the back electrode and the recording material into close contact with each other, or air is sucked through an opening provided in the back electrode, or a toner passage hole is provided in a path for conveying the recording material. The recording material charging means provided on the upstream side of the position facing the recording material charges electric charge on the surface of the recording material and applies an electrostatic attraction force between the recording material and the back electrode, thereby forming a roller or the like. It is possible to keep the gap constant even at the leading end of the recording material, as compared with the case of using the recording material support member.

Further, according to the second feature of the present invention, when the recording material is not present between the toner passage hole and the opening, the air sucking means sucks air from the opening provided in the back electrode. By doing so, it is possible to remove the toner, dust, etc. adhering to the toner passage holes due to environmental changes, dust, etc., and the dots formed on the recording material become small, or dot dropouts that are not formed at all occur. Can be prevented.

Further, the timing at which air is sucked by the air sucking means from the opening provided on the back electrode is more than that when the leading edge of the recording material reaches the position facing the toner passage hole after the conveyance operation of the recording material is started. By setting the timing early, you can clean the toner passage hole for each printing operation,
It is possible to prevent deterioration of print quality.

Here, by providing the opening of the back electrode so as to face the toner passage hole of the toner control means, the suction speed of air can be increased, and the toner, dust, etc. adhering to the toner passage hole can be increased. The removal can be effectively performed.

Further, according to the third feature of the present invention, by controlling the timing of the printing operation so as not to perform printing by the toner passage hole of the plurality of toner passage holes at the position facing the opening, the toner passage The dispersion of the electric field generated between the holes and the back electrode can be suppressed, and the dots formed on the recording material can be converged, so that the printing quality can be improved.

Further, according to the fourth feature of the present invention, by sucking air in the portion facing the toner passage hole in the circumferential direction, the rear electrode is formed in the portion where the recording material faces the toner passage hole. When the recording material is sucked and passes a portion facing the toner passage hole, the recording material is no longer sucked and it is possible to prevent the recording material from being wrapped around the back electrode.

[Brief description of drawings]

FIG. 1 is an enlarged view of a toner flying unit of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a toner flying portion of the image forming apparatus according to the second embodiment of the present invention.

FIG. 3 is an enlarged view of a toner flying portion of an image forming apparatus according to a third embodiment of the present invention.

FIG. 4 is a plan view of an opening of a back electrode of an image forming apparatus according to a third embodiment of the present invention.

FIG. 5 is an enlarged view of a toner flying portion of the image forming apparatus according to the third embodiment of the present invention.

FIG. 6 is a plan view of an opening of a back electrode of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 7 is an enlarged view of a toner flying portion of the image forming apparatus according to the fourth embodiment of the present invention.

FIG. 8 is an enlarged view of a toner flying portion of an image forming apparatus according to a fifth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 10 is an enlarged view of a toner flying unit of a conventional image forming apparatus.

FIG. 11 is a plan view of a recording head of a conventional image forming apparatus.

FIG. 12 is an enlarged view of a toner flying unit when a problem occurs in the conventional image forming apparatus.

[Explanation of symbols]

 22 toner 23 recording head 24 toner supply means 25 layer thickness regulating member 26 image processing circuit 27 drive circuit 28 recording material 29 back electrode 30 row electrode 31 insulating layer 32 column electrode 33 toner passage hole 34 opening 35 air suction means

Claims (8)

[Claims] 1. A toner control means having a plurality of toner passage holes that can be opened and closed electromagnetically according to image information, and a toner is carried on a surface of the toner control means so as to face the toner passage holes of the toner control means. And a back electrode provided at a position facing the toner carrier with the toner control unit interposed therebetween, and a recording material is provided between the toner control unit and the back electrode. An image forming apparatus which conveys the toner carried on the toner carrier to a recording material through a toner control means by applying a voltage to the back electrode, wherein the recording material is brought into close contact with the back electrode. An image forming apparatus comprising a contact means. 2. The image forming apparatus according to claim 1, wherein the contact means comprises an opening provided in the back electrode and an air suction means for sucking air through the opening. . 3. The recording material charging means for charging the recording material provided on the upstream side in the conveying direction of the recording material to a polarity different from the voltage applied to the back electrode. The image forming apparatus according to item 1. 4. The air suction device sucks air through the opening when the recording material is not present between the toner passage hole and the opening. Image forming apparatus. 5. After the recording material conveyance operation is started, air is sucked through the opening by the air suction means before the leading edge of the recording material is conveyed between the toner passage hole and the opening. The image forming apparatus according to claim 2, wherein 6. The method according to claim 4, wherein the opening is provided at a position facing the toner passage hole.
The image forming apparatus described. 7. The opening is formed in a slit shape that is long in the direction perpendicular to the recording material conveying direction, and the back electrode is movable in the recording material conveying direction. 3. The image forming apparatus according to claim 2, further comprising control means for controlling the timing of printing operation so that printing is not performed by the toner passage hole at a position facing the opening. 8. The back electrode is formed into a columnar shape that is rotatable long in a direction perpendicular to the recording material conveyance direction, and air is sucked by the air suction means at a portion facing the toner passage hole in the circumferential direction. The image forming apparatus according to claim 2, which is performed.