JPH08112934A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To stabilize the conveyance state of the image recording medium 3 passing between the electrode array 1 and the back electrode body 2. An electrode array 1 is arranged between a rear electrode body 2 on which an image recording medium 3 abuts and a toner carrying roller 16 so that a plurality of rows of openings 12 are arranged in parallel with a rotation axis of the toner carrying roller 16. The stabilizing roller 22 is disposed in the conveyance path of the image recording medium 3 between the rear electrode body 2 and the fixing device 5. A voltage having a polarity opposite to that of the voltage applied to the back electrode body 2 is applied to the stabilizing roller 22 to suck the back surface of the image recording medium 3 being conveyed, and the front end portion or the rear end portion of the image recording medium 3 is an electrode array. Do not touch the surface of 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an image forming apparatus which can be used in a copying machine, a facsimile machine, a printer, etc., and more specifically, an image forming apparatus for forming an image by flying charged toner by an electric field. It is about.

[0002]

2. Description of the Related Art Heretofore, as one type of image forming apparatus, the present applicant has previously proposed that, in JP-A-6-155798, a toner charged by an electrode array having a plurality of openings arranged in a line. Of the electrically conductive toner carrying roller to form an image on an image recording medium located on the opposite side of the electrode array with respect to the conductive toner carrying roller. The sheet is arranged so as to face the peripheral surface of the toner carrying roller, and on one side of the sheet that faces the image recording medium, control electrodes are arranged separately for each opening and pulled out from the opening. In order to cause the generated toner to fly toward the front surface of the image recording medium by electrostatic force, the back electrode body is arranged so as to contact the back surface side of the image recording medium, and the back electrode body is charged with a predetermined polarity. Configured to apply a. Further, it has been proposed that the toner attached to the surface of the image recording medium as a pixel fixes the image by a fixing device provided on the downstream side of the conveyance.

By the way, in order to obtain a high quality image with this type of image forming apparatus, it is preferable to set the interval (gap) between the surface of the image recording medium and the surface of the electrode array to about 0.5 mm. On the downstream side of the rear surface of the image recording medium, the toner flying from the openings of the electrode array adheres to the surface side of the image recording medium as pixels. It is necessary to stably convey to the fixing device without rubbing against the surface of the array.

[0004]

However, in the above-mentioned conventional configuration, when the image recording medium is conveyed toward the surface of the back electrode body, the image recording medium is conveyed by sandwiching both sides of the image recording medium with a pair of conveying rollers. However, if a pair of conveying rollers is used as described above between the conveying downstream side and the fixing device, the toner as pixels adhering to the surface of the image recording medium is disturbed. As a result, a predetermined image cannot be obtained, so that the conveyance of the image recording medium between the back electrode body and the fixing device becomes very unstable.

In particular, the surface of the image recording medium is the surface of the electrode array until the leading edge of the image recording medium reaches the fixing device or when the rear edge of the image recording medium is separated from the rear electrode body. However, there is a problem in that there is a high possibility that the paper will be conveyed while coming into contact with other objects, which will hinder image formation. In order to solve this problem, it has been considered that the fixing device is arranged close to the back electrode body, but since this type of fixing method generally applies heat to the toner, a heating unit in the fixing device is used. When it comes close to the toner case including the electrode array, there is a problem that the toner may be melted and condensed due to radiant heat, etc., and it is bulky because there is a roller that presses against the image recording medium with an appropriate pressing force at the time of fixing. Therefore, there is also a problem that the fixing device cannot be arranged close to the back electrode body.

The present invention has been made to solve these problems, and an object of the present invention is to provide an image forming apparatus capable of stabilizing the conveyance of an image recording medium so that a high quality image can be obtained. It is what

[0007]

To achieve the above object, an image forming apparatus according to the present invention is an electrode array having a plurality of openings and control electrodes for the openings, and the electrodes. Toner supply means for supplying toner to the openings of the array, a back electrode body and an image recording medium arranged on the side opposite to the toner supply means with respect to the electrode array, and each control electrode of the electrode array are independent. And a control electrode driving unit for selectively flying the toner from the toner supply unit onto the image recording medium through an opening by controlling the toner supply unit. While carrying a charge of a predetermined polarity on the back surface of the image recording medium, a transport stabilizing means for applying a voltage having a polarity opposite to the polarity is provided downstream of the back electrode body in the transport direction of the image recording medium. , But on the position close to the rear surface of the image-recording medium.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the conveyance stabilizing means is configured to move far and far with respect to the conveyance path of the image recording medium. According to a third aspect of the present invention, in the image forming apparatus according to the first aspect or the second aspect, the front surface side of the image recording medium is disposed close to the back electrode body on the upstream side of conveyance of the image recording medium. The regulation means is provided.

[0009]

Next, an embodiment of the present invention will be described. FIG. 1 shows an outline of an image forming apparatus according to the present invention, which is about 0.
A metal flat plate-shaped back electrode body 2 is supported by a frame (not shown) with an interval of 5 mm to 1 mm. An image recording medium 3 such as a printing paper, which is inserted in a gap between the electrode array 1 and the back electrode body 2, can be conveyed in the direction of arrow A by a paper feeding device 4 including a roller pair. A fixing device 5 including a heating roller 6 and a pressing roller 7 for fixing an image is provided on the downstream side of the image recording medium 3 in the conveying direction.
Is arranged.

Further, the electrode array 1 includes a toner supply device 8
The toner case 9 is attached with an appropriate tension applied to the opening hole of the toner case 9. Next, the details of each of the components will be described. A toner supply device 8 as a toner supply unit.
Is a toner case 9 which also serves as a housing, a toner 18 accommodated in the toner case 9, and a supply roller 15.
, A conductive toner carrying roller 16 made of a metal cylinder such as copper or aluminum, and a toner 18 in the toner reservoir chamber 14.
Agitator 17 which supplies the toner to the supply roller 15 while stirring the toner, and the toner 1 on the peripheral surface of the toner carrying roller 16.
It is composed of a regulating blade 19 and the like for rubbing 8 with a constant layer thickness. The toner carrying roller 16, the supply roller 15, and the agitator 17 each having a rotary shaft in a direction orthogonal to the direction in which the image recording medium 3 is conveyed have substantially the same length, and are rotated by a rotary drive device (not shown). 1 is rotated in the direction of the arrow.

A part of the outer peripheral surface of the toner carrying roller 16 is
It is arranged so as to face the back surface of the insulating sheet 11 so as to come into contact with the vicinity of the opening 12 row of the electrode array 1 described later. The base end of a regulation blade 19 for regulating the thickness of the toner layer, which is in pressure contact with the peripheral surface on the upstream side of the rotation of the toner carrying roller 16, is fixed to the toner case 9, and the toner supplied from the agitator 17 via the supply roller 15 is supplied. The wide blade 18 of the regulation blade 19 slidably contacts the outer peripheral surface of the toner carrying roller 16 to regulate the layer thickness of the toner 18 to a predetermined uniform thickness and to charge the toner 18.

The electrode array 1, as shown in FIG.
A plurality of openings 12 having a diameter of about 40 μm are formed in a row in a direction orthogonal to the moving direction of the image recording medium 3 on an insulating sheet 11 made of polyimide as an electrically insulating base material having a thickness of 5 μm. Control electrodes 13 are formed on the side facing the image recording medium 3 so as to be divided into the openings 12.

If the insulating sheet 11 is made too thin,
A polyimide resin having a thickness of 25 μm is suitable because it becomes difficult to form the control electrode 13 and handle the electrode array 1 itself. As shown in FIG. 2, for each opening 12 such as a round hole formed by penetrating the insulating sheet 11, an annular electrode portion is provided on the upper side of the insulating sheet 11 along the circumferential edge of each opening 12. A control electrode 13 composed of 13a and a lead portion 13b for connecting each electrode portion 13a to the control voltage applying circuit 21 is formed of a metal such as copper or gold having a thickness of about 1 μm.

Further, as can be understood with reference to FIG.
In the electrode array 1, the sheet 11 is bent with respect to the toner carrying roller 16 about the row of the openings 12 at the same angle on the upstream side and the downstream side in the moving direction of the image recording medium 3.
The row-shaped openings 12 are evenly pressed against the outer peripheral surface of the toner carrying roller 16 and stretched so that the contact area with the outer peripheral surface of the toner carrying roller 16 is increased.

A DC power supply 20 is connected between the back electrode body 2 and the toner carrying roller 16, and the back electrode body 2
Is applied with a high voltage of about +1 kV, and a data control circuit 28 is connected between the toner carrying roller 16 and the integrated circuit chip 23, and an image forming signal from the data control circuit 28 is connected. Based on the above, voltage is applied to the control electrode 13 to 0V or + 50V.

The agitator 17, the toner supply roller 15, and the regulation blade 19 are grounded at 0V. Further, on the downstream side of the conveyance of the image recording medium 3, between the back electrode body 2 and the fixing device 5, the back electrode body carries a charge of a predetermined polarity on the back side of the image recording medium, A transport stabilizing roller 22 as a transport stabilizing means made of a conductive material such as aluminum to which a voltage having a polarity opposite to the polarity of the voltage applied to the back electrode body 2 (+1 kV in the embodiment) is applied.
Is provided at a position close to the back surface of the image recording medium 3. In the embodiment, a voltage of -5 kV is applied to the conveyance stabilizing roller 22 via the stabilization voltage applying circuit 23. The conveyance stabilizing roller 22 is driven by a drive motor (not shown) in the arrow direction of FIG. Rotate.

The toner 18 is an electrically insulating toner, and is supplied to the surface of the toner carrying roller 16 by the supply roller 15. The surface of the conductive toner carrying roller 16 and the toner 18 attached thereto also have the same potential as a whole. Next, the recording operation (printing operation) of the image forming apparatus thus configured will be described.

First, the toner carrying roller 16 and the toner supply roller 15 and the agitator 17, which have substantially the same length as the toner carrying roller 16, rotate in the directions of the arrows shown in FIG. The insulating toner 18 sent from the roller 15 is rubbed against the surface of the toner carrying roller 16. Next, the toner layer thickness regulating blade 19 reduces the layer thickness of the toner 18 to a predetermined value, and the negatively charged toner 18 is carried on the surface of the toner carrying roller 16. The toner 18 conveyed toward the electrode array 1 by the rotation of the toner carrying roller 16 is rubbed against the insulating sheet 11 of the electrode array 1 and supplied below the opening 12.

On the other hand, in response to a paper feed command, the image recording medium 3
Is transported into the gap between the back electrode body 2 and the electrode array 1 via the paper feeding device 4 shown in FIG. +1 for back electrode body 2
Since the voltage of kV is applied, the back surface of the image recording medium 3 which is in contact with the back electrode body 2 at the location is positively charged by electrostatic force. Next, -5 is applied to the conveyance stabilizing roller 22.
Since the voltage of kV is applied, when the leading edge of the image recording medium 3 which is positively charged reaches the conveyance stabilizing roller 22, it is attracted to the front side of the conveyance stabilizing roller 22 by electrostatic force. .

If there is an image, the control voltage application circuit 21 is driven based on the image signal, and a voltage of +50 V is applied to the control electrode 13 corresponding to the image portion. As a result, in the vicinity of the opening 12 corresponding to the image portion, due to the potential difference between the control electrode 13 and the conductive toner carrying roller 16, an electric force line from the ring-shaped control electrode portion 13a toward the toner carrying roller 16 is generated. It is formed. The strength of the line of electric force at this time is proportional to the potential difference and inversely proportional to the distance between the control electrode 13 and the surface of the toner carrying roller 16.

Then, the negatively charged toner 18
Is subjected to an electrostatic force in the direction of higher potential by the line of electric force from the control electrode 13 toward the toner carrying roller 16, and is drawn out so as to pass through the opening 12. The toner 18 thus extracted is further subjected to the voltage (+1 kV) applied to the back electrode body 2 so that the image recording medium 3
The electric field formed between the electrode array 1 and the electrode array 1 causes the toner 18 to fly toward the image recording medium 3, and the toner 18 is deposited on the surface of the image recording medium 3 to form a visible pixel.

For the non-image portion, the control electrode 1
A voltage of 0 V is applied to 3. As a result, since no electric field is formed between the toner carrying roller 16 and the control electrode 13, the toner 18 on the toner carrying roller 16 is not subjected to electrostatic force, and these toners 18 do not pass through the opening 12. Absent. Further, the opening 1 is formed on the surface of the image recording medium 3.
While one row of toner 18 is formed by the two rows, the image recording medium 3 is conveyed by one pixel in the direction perpendicular to the row of the openings 12 (direction of arrow B in FIG. 1). By repeating such an operation, a predetermined image is formed by the toner 18 on the surface of the image recording medium 3. After that, the toner image is heated and fixed on the image recording medium 3 at the position of the fixing device 5.

In this case, since the image recording medium 3 is conveyed toward the fixing device 5, the back surface of the leading end portion of the image recording medium 3 is attracted by the electrostatic force to the conveyance stabilizing roller 22 in a non-contact state. In this state, the transport stabilizing roller 22 is moved in the direction of arrow A by a distance corresponding to one pixel via a transport mechanism (not shown). As a result, an appropriate tension acts on the image recording medium 3, the surface of the electrode array 1 and the surface of the image recording medium 3 do not come into contact with each other, the gap is stabilized, and the toner image is not disturbed.

When the front end portion of the image recording medium 3 is nipped by the fixing device 5, the voltage application to the conveyance stabilizing roller 22 is stopped and the direction of the back electrode body 2 is returned. Immediately before the rear end of the image recording medium 3 is separated from the back electrode body 2, a predetermined voltage (-5 kV) is applied to the conveyance stabilizing roller 22 so that the surface such as the rear edge of the image recording medium 3 becomes an electrode. It is possible to prevent contact with the surface of the array 1. When the conveyance stabilizing roller 22 is moved toward the fixing device 5 in this state, the surface of the image recording medium 3 does not come into contact with the toner case 9 or the like, the toner image is not disturbed, and the fixing device 5 fixes the image cleanly. be able to.

Incidentally, by appropriately setting the value of the voltage of a predetermined reverse polarity applied to the conveyance stabilizing roller 22, or while the applied voltage value remains constant, the conveyance stabilizing roller 22 is
Is configured so that it can be moved in the near and far directions with respect to the back surface of the image recording medium 3, it is possible to suck the back surface of the image recording medium 3 without contacting (non-contacting) with the surface of the conveyance stabilizing roller 22. . By doing so, it is possible to prevent the leading end of the image recording medium from winding around the peripheral surface of the conveyance stabilizing roller 22 and becoming impossible to be caught in the fixing device 5. By rotating and driving the conveyance stabilizing roller 22 in this state, the fixing device can be applied with tension applied to the image recording medium 3 without reciprocating the conveyance stabilizing roller 22 between the back electrode body 2 and the fixing device 5. You may comprise so that it may convey toward 5.

As another embodiment, the conveyance stabilizing roller 22 disposed near the rear end portion of the back electrode body 2 is used as the image recording medium 3.
In the initial state until the front end of the image recording medium 3 reaches the conveyance stabilizing roller 22, the voltage applied to the conveyance stabilizing roller 22 is increased and the image recording is performed. After the transport stabilizing roller 22 is moved so as to approach the back surface of the medium 3 so that the front end of the image recording medium 3 is completely caught by the transport stabilizing roller 22, the transport stabilizing roller 22 is moved to the image recording medium. 3 is slightly separated from the back surface of the sheet 3, and the conveyance stabilizing roller 22 is rotated at a speed higher than the conveyance speed of the sheet feeding device 4 to apply tension. Further, after the rear end of the image recording medium 33 is separated from the back electrode body 2, the conveyance stabilizing roller 22 is rotated so as to be the same as the conveyance speed of the sheet feeding device 4 so that stable conveyance is realized. You can

Further, the value of the reverse polarity applied voltage to be applied is adjusted at a proper timing or the voltage is adjusted at an appropriate timing so that the leading edge or the trailing edge of the image recording medium 3 is not wound around the conveyance stabilizing roller 22. The application may be stopped for an appropriate time. Further, in the above-described embodiment, the conveyance stabilizing roller 22 is made of metal, but if the surface is coated with an electrically insulating synthetic resin material, or if it is made of a semiconductive rubber or resin roller, the periphery of The risk of electrical short circuit with parts can be eliminated.

Further, as shown in FIG. 1, a flat plate-shaped regulating member 24 is provided so that the front end of the image recording medium 3 does not come into contact with the surface of the electrode array 1 when entering toward the back electrode member 2.
May be disposed in the vicinity of the back electrode body 2 on the upstream side of conveyance, and the regulating body 24 may bias the image recording medium 3 against the surface of the back electrode body 2 by a spring. The regulator is in the vicinity of the back electrode body 2 on the upstream side of the conveyance of the image recording medium 3 and at a position facing the back surface of the image recording medium 3,
It may be in the form of a roller that attracts the image recording medium 3 by the applied electrostatic force.

In the image forming apparatus constructed as described above, when the insulating toner 18 is used, the conductive toner carrying roller 16 and the control electrode 1 in the electrode array 1 are used.
The electrical insulation between 3 and 3 is maintained. In the non-image operation, -10 V is applied to the control electrode 13 for the non-image portion.
Alternatively, a negative voltage may be applied. In this case, an electric field opposite to the electric field with respect to the image forming portion is formed between the toner carrying roller 16 and the control electrode 13, and the flying of the toner 18 on the toner carrying roller 16 is further suppressed. It is possible to form an image with less fogging.

According to the above process, the control electric field in the electrode array 1 is formed between the control electrode 13 and the surface of the toner carrying roller 16 as one electrode facing the opening 12. The electric field for control can be directly applied to the toner 18 conveyed by the toner carrying roller 16 to the vicinity of the opening 12, and the toner control efficiency is excellent.

Since the toner carrying roller 16 which is one of the electrodes and the electrode array 1 having the control electrode 13 are extremely close to each other with the toner 18 being conveyed therebetween, the applied voltage for control is lowered. However, since the electric field strength can be increased and the flight force of the toner 18 can be increased,
As the control voltage application circuit 21 for driving the control electrode 13, a low voltage one can be used, which reduces the manufacturing cost of the image forming apparatus.

Electrically insulating sheet 11 in the electrode array 1
When the toner is carried on the outer peripheral surface of the toner carrying roller 16 as one electrode, there is no electrical short circuit even if the toner 18 is not carried on the toner carrying roller 16. It goes without saying that the back electrode body 2 in the present invention may be formed in a roller shape.

[0033]

As described above, claim 1
The image forming apparatus according to the invention described in (1) above is provided with an electrode array including a plurality of openings and control electrodes for the openings, a toner supply unit for supplying toner to the openings of the electrode array, and the electrode array. On the other hand, by independently controlling the back electrode body and the image recording medium arranged on the opposite side of the toner supply means, and the respective control electrodes of the electrode array,
In an image forming apparatus including a control electrode driving unit that selectively flies the toner from a toner supply unit onto the image recording medium through an opening, the back electrode body provides a predetermined amount on a back surface of the image recording medium. While carrying the electric charge of the polarity, on the downstream side of the back electrode body in the carrying direction of the image recording medium, a carrying stabilizing means to which a voltage of the opposite polarity is applied is provided near the back surface of the image recording medium. It is provided at the position where

Therefore, even before the leading edge of the image recording medium having the toner image on the surface reaches the fixing device, or even when the rear edge of the image recording medium is separated from the rear electrode body, It is possible to avoid a situation in which the back surface of the image recording medium is attracted by the voltage of the opposite polarity applied to the transportation stabilizing means, and the surface of the image recording medium is transported while being in contact with the surface of the electrode array or the like. Therefore, the toner image once formed is not disturbed, and stable image formation can be achieved.

The invention described in claim 2 is the same as claim 1
In the image forming apparatus described in the above,
Since the image recording medium is configured so as to move far and far with respect to the conveying path of the image recording medium, when the back surface of the image recording medium is sucked by the voltage of the reverse polarity applied to the conveying stabilizing means, the suction force is excessive. Alternatively, the shortage is corrected and the image recording medium 2
It is possible to very easily prevent a situation in which the front end portion and the rear end portion of the device are wound around the conveyance stabilizing means, are sucked and cannot be separated, and conversely are too far from the conveyance stabilizing means. Therefore, according to the present invention, in addition to the same effect as that of the first aspect of the invention, there is an effect that the image recording medium can be stably transported.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the front surface side of the image recording medium is brought close to the back electrode body on the upstream side of conveyance of the image recording medium. A regulation means for this is provided. Therefore, the surface of the image recording medium comes into contact with the electrode array at the initial stage when the front end of the image recording medium is conveyed so as to approach the back electrode body, or conversely at the end when the rear end of the image recording medium is separated from the sheet feeding device. As a result, the toner image can be prevented from being disturbed, and in addition to the same effect as that of the first aspect of the invention, the effect that the image recording medium can be stably conveyed can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of an image forming apparatus.

FIG. 2 is a partially cutaway enlarged perspective view of an electrode array.

[Explanation of symbols]

 1 Electrode Array 2 Back Electrode Body 3 Image Recording Medium 4 Paper Feeding Device 5 Fixing Device 8 Toner Supply Device 9 Toner Case 11 Insulating Sheet 12 Opening 13 Control Electrode 16 Toner Carrier Roller 20 DC Power Supply 21 Control Voltage Applying Circuit 22 Stabilization of Transport Roller 23 Stabilizing voltage application circuit 24 Regulator

Claims (3)

[Claims] 1. An electrode array having a plurality of openings and control electrodes for the openings, toner supply means for supplying toner to the openings of the electrode array, and the toner supply for the electrode array. By independently controlling the back electrode body and the image recording medium arranged on the side opposite to the means, and each control electrode of the electrode array, the toner is supplied from the toner supplying means to the image recording medium through the opening. In the image forming apparatus including a control electrode driving unit for selectively flying the image recording medium, the back electrode body carries electric charges of a predetermined polarity on the back surface of the image recording medium, and An image forming apparatus characterized in that, on the downstream side in the carrying direction, a carrying stabilizing means to which a voltage having a polarity opposite to the polarity is applied is provided at a position close to the back surface of the image recording medium. 2. The image forming apparatus according to claim 1, wherein the conveyance stabilizing unit is configured to move in a perspective manner with respect to a conveyance path of the image recording medium. 3. The regulating means for causing the front surface side of the image recording medium to come close to the back electrode body, is provided on the upstream side of the conveyance of the image recording medium. Image forming device.