JPH0858142A - Image forming device - Google Patents

Abstract

PURPOSE: To form an image with an adequate print density at a low control voltage by arranging an aperture electrode element with apertures between a back electrode and a toner carrying roller which a recording medium comes into contact with, and transporting an insulating toner. CONSTITUTION: An electroconductive magnetic brush 17 consisting of a carrier 14 of eleotroconductive magnetic powder is formed on the surface of a toner carrying roller 18 which rotates in a relative direction to the magnetic roller 19 of an inner diameter part, and an insulating toner 22 is carried by the electroconductive magnetic brush 17. The electroconductive magnetic brush 17 is caused to have the function of a reference electrode by applying a voltage of specified potential difference to a control electrode 13 of an aperture electrode element 1 and the toner carrying roller 18. If the eleotroconductive magnetic brush 17 is caused to come into contact with the insulating sheet 11 of the aperture electrode element 1, the insulating toner 22 can be actively transported to a position near the aperture 1, 2, and further, an electric field area between the electroconductive magnetic brush 17 and the control electrode 13 can be widened.

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, by charging an electrically insulating toner,
The present invention relates to an image forming apparatus that flies by an electric field to form an image.

[0002]

2. Description of the Related Art Conventionally, as one type of image forming apparatus, the applicant of the present invention has previously disclosed in Japanese Patent Laid-Open No. 3-215874 that an aperture electrode body having a plurality of apertures is used to pass an aperture of charged toner. And an image forming apparatus for forming an image on a recording medium located on the opposite side of the toner supply source with the aperture electrode body sandwiched therebetween, wherein the aperture electrode body is one side of an insulating sheet. A reference electrode is formed on the side facing the toner supply source, and a control electrode is arranged on the side facing the recording medium separately for each aperture. The toner supply source is a brush. A large number of rotating toner carriers that are planted on the circumferential surface,
It has been proposed that the blade be configured to come into contact with the brush to splash the toner into a cloud shape (cloud shape).

[0003]

However, in the above device, the region affected by the electric field can be formed only in the narrow space between the reference electrode and the control electrode in the aperture of the aperture electrode body. Further, the brush and the blade do not play a role of forming an electric field, but only form a cloud of toner (cloud), and moreover, the location where the cloud of toner occurs is a position away from the aperture,
Cloud-shaped (cloud-shaped) toner cannot be positively conveyed and guided into the electric field in the aperture between the reference electrode and the control electrode of the aperture electrode body, and the toner concentration in the electric field is insufficient. Therefore, there is a problem that the print density cannot be sufficiently increased.

In order to eliminate this drawback, the toner is conveyed into the area of the aperture where the electric field influences it. Therefore, when the brush is brought into contact with the aperture electrode body, wrinkles are generated in the thin aperture electrode body, and abrasion is caused. There is a problem that durability is poor. On the other hand, in order to increase the flying amount of toner and to achieve sufficient print density, in order to increase the strength of the electric field in the aperture,
In order to increase the potential difference between the reference electrode and the control electrode, the drive circuit needs to withstand a high voltage, which causes a problem of high manufacturing cost.

An object of the present invention is to provide an image forming apparatus which achieves these technical problems and can obtain a sufficient print density by a low control voltage.

[0006]

In order to achieve the above object, the image forming apparatus of the invention according to claim 1 is a surface of a toner carrying means for carrying and carrying an electrically insulating toner in an aperture of an aperture electrode body. Are arranged close to each other, and by applying an image signal to the aperture electrode body,
An image forming apparatus that controls the passage of toner particles through an aperture and obtains an image on a recording medium disposed on the opposite side of the toner transport means with an aperture electrode body interposed therebetween. The toner carrier means is composed of an electric insulating means and a control electrode attached to the electric insulating means, while the toner conveying means is constituted so as to also serve as an electrode, and the electric insulating toner is removed by a magnetic brush made of conductive magnetic powder. A voltage for applying a predetermined potential to the control electrode in the aperture electrode body and the toner transporting means, the part of the magnetic brush being configured to come into contact with the sheet-like electrical insulating means. And an application circuit.

According to a second aspect of the present invention, the toner conveying means according to the first aspect is arranged such that a magnet roller is arranged in an inner diameter portion of a toner carrying roller made of a metal cylinder so that both rollers rotate in a relative direction. In this configuration, the electrodes are applied to the toner carrying roller.

[0008]

Next, an embodiment of the present invention will be described. FIG. 1 shows an outline of an image forming apparatus of the present invention, in which an upper side of an aperture electrode body 1 as a toner flow control means is
A cylindrical back electrode roller 2 is rotatably supported by a frame (not shown) with a gap of 1 mm, and is rotated in the direction of arrow A by a driving device (not shown). A recording medium 3 such as a printing sheet inserted in the gap between the aperture electrode body 1 and the rear electrode roller 2 is configured to be conveyed in the direction of arrow B by the paper feeding device 4, and is downstream in the conveying direction of the recording medium 3. A fixing device 5 including a heating roller 6 and a pressing roller 7 for fixing an image is arranged on the side.

The aperture electrode body 1 is arranged on the upper surface of a toner case 9 of a toner supply device 8 which will be described later. Next, the details of each of the components will be described. The aperture electrode body 1 has substantially the same structure as shown in FIGS. 1, 2 and 3.
A plurality of apertures 12 having a diameter of about 100 μm are provided on a polyimide insulating sheet 11 as an electric insulating means having a thickness of 5 μm.
Are formed in one row, and the 12 rows of apertures extend in a direction orthogonal to the transport direction of the recording medium 3. Control electrodes 13 are formed for each aperture 12 on the side facing the recording medium 3. That is, the insulating sheet 1
For each of the round-hole-shaped apertures 12 formed through 1
On the upper side of the insulating sheet 11, an annular electrode portion 13a is provided along the circumference of each aperture 11, and a lead portion 13b for connecting each electrode portion 13a to the control voltage applying circuit 21 of FIG.
The control electrode 13 composed of is formed of a metal such as copper and gold having a thickness of 1 μm.

If the insulating sheet 11 is made too thin,
A polyimide resin having a thickness of 25 μm is suitable because it is difficult to form the control electrode 13 and handle the aperture electrode body 1 itself. The toner supply device 8 includes a toner case 9 also serving as a housing, an insulating toner 22 housed in the toner case 9, a carrier 14 as a conductive magnetic powder, a supply roller 15, a toner conveying unit 16 and the like. It consists of

The carrier 14 is magnetite, which is electrically conductive and magnetic, or iron powder, iron oxide powder,
It may be magnetic powder having conductivity such as copper ferrite and zinc ferrite, and the average particle size of the carrier 14 is 20 to 1
It is preferably about 00 μm. In addition, the insulating toner 22
Is a mixture of non-magnetic powder and a binder resin, and kneads a binder resin that helps fixing to the recording medium 3 and wax that has a releasing effect with the heating roller 6 of the fixing device 5 if necessary. , Pulverize and classify to set the particle size to 20 μm or less.
The insulating toner 22 may be either pulverized toner or dyed toner, depending on the manufacturing method.

The mixing ratio of the toner 22 and the carrier 14 is 5 to 50 parts of the toner 22 and 4 of the carrier 14.
About 0 to 150 parts is preferable. The toner conveying means 16 is
The toner is made of a metal cylinder such as copper or aluminum and is configured to also serve as an electrode, and is configured to convey the insulating toner by the conductive magnetic brush 17 by the carrier 14 as the conductive magnetic powder. A magnet roller 19 having an axis orthogonal to the direction in which the recording medium 3 is conveyed is arranged inside the carrying roller 18. Magnetic poles (N poles and S poles) of the magnet roller 19 are alternately arranged in the rotation direction, and the magnet roller 19 and the toner carrying roller 18 rotate relative to each other and the magnetic force of the magnet roller 19 causes the toner carrying roller to rotate. A conductive magnetic brush 17 of an appropriate length is formed by the carrier 14 on the outer circumferential surface of 18.

The magnet roller 19, the toner carrying roller 18, and the supply roller 15 are long along the row direction of the apertures 12 in the aperture electrode body 1 and have a length substantially equal to the row of the apertures 12. The magnet roller 19 and the toner carrying roller 18 are rotated in directions C and D (opposite directions) by a rotation driving device (not shown). When the supply roller 15 rotates in the direction of arrow E (the same direction as the rotation of the toner carrying roller 18) by a rotation driving device (not shown), the conductive surface is formed on the circumferential surface of the toner carrying roller 18 in the toner case 9. The magnetic carrier 14 having the toner is rubbed against the toner 22 having the electric insulating property.

In the toner case 9, the conductive material is provided on the upstream side of the toner carrying roller 18 with respect to the position where the aperture 12 of the aperture electrode body 1 is conveyed, in the vicinity of the outer circumference of the toner carrying roller 18. A restriction blade 20 for restricting the height of the magnetic brush 17 is arranged, and the restriction blade 20 forms the conductive magnetic brush 17 by the carrier 14 in which the layer is restricted to a length of about 1 mm in the embodiment. To be done. The toner carrying roller 18 is arranged so that a part of the conductive magnetic brush 17 contacts the insulating sheet 11 near the aperture 12 in the aperture electrode body 1.

A DC power supply 24 is connected between the back electrode roller 2 and the toner carrying roller 18, and a voltage of +1 kV is applied to the back electrode roller 2. In addition, the control electrode 13 in the aperture electrode body 1,
A control voltage application circuit 25 is connected between the electrode for the toner carrying roller 18 and the control voltage application circuit 2.
5 is configured to apply a voltage of 0 V or +50 V to the control electrode 13 based on the image forming data. In the embodiment, the potential of the toner carrying roller 18 is 0V.

Since the conductive magnetic brush 17 carried on the surface of the toner carrying roller 18 is the carrier 14 which is a conductive magnetic powder, the potential of the toner carrying roller 18 and the potential of the conductive magnetic brush 17 are the same. Becomes Therefore, when the conductive magnetic brush 17 approaches the control electrode 13 near the aperture 12, the conductive magnetic brush 17 serves as a kind of reference electrode.

Next, the recording operation of the image forming apparatus having the above structure will be described. First, the magnetic roller 19 rotates in the direction of arrow C in FIG. 1, and the supply roller 15 and the toner carrying roller 18 rotate in the directions of arrows D and E in FIG. The toner 22 and the carrier 14 which is the conductive magnetic powder are rubbed against the outer circumferential surface of the toner carrying roller 18, and the toner forms the conductive magnetic brush 17 of a predetermined length and the toner 22.
Is negatively charged and carried on the conductive magnetic brush 17.

The toner 22 is conveyed toward the lower surface of the aperture electrode body 1 together with the conductive magnetic brush 17 as the toner carrying roller 18 rotates. The conductive blade 17 is regulated by the regulating blade 20 to about 1 mm. The conductive magnetic brush 17 and the toner 22 are rubbed against the insulating sheet 11 on the lower surface of the aperture electrode body 1, and a part of the toner 22 drops off from the conductive magnetic brush 17 to form a cloud shape (cloud shape). It stays in the space below the vicinity of 12. When the toner 22 falls off from the conductive magnetic brush 17, the toner 22 is greatly negatively charged.

Here, in accordance with an image forming signal, the control voltage applying circuit 25 is applied to the control electrode 13 corresponding to the image portion.
To +50 V is applied. As a result, in the vicinity of the aperture 12 corresponding to the image portion, due to the potential difference between the control electrode 13 and the conductive magnetic brush 17, the control electrode 1 is formed.
A line of electric force is formed from 3 toward the conductive magnetic brush 17. 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 conductive magnetic brush 17.

Then, due to the lines of electric force from the control electrode 13 toward the conductive magnetic brush 17, the toner 22 is dropped from the conductive magnetic brush 17 into a cloud shape, and the negatively charged toner 22 has a high potential, that is, Control electrode 13
The electrostatic force is applied in the direction, passes through the aperture 12, and is drawn to the electrode portion 13a side of the control electrode 13. The extracted toner 22 is further caused by an electric field formed between the recording medium 3 and the aperture electrode body 1 by the high voltage (+1 kV in the embodiment) applied to the back electrode roller 2,
The toner 22 flies toward the surface of the recording medium 3 (the lower surface in the embodiment), and the toner 22 spreads on the surface of the recording medium 3.
Can be deposited to form visible pixels.

A voltage of -10V is applied from the control voltage applying circuit 25 to the control electrode 13 for the non-image portion. As a result, the conductive magnetic brush 17 and the control electrode 13
Therefore, an electric field in the opposite direction to the above is not formed between the toner and the toner, and the toner 22 on the surface of the conductive magnetic brush 17 and the toner 22 retained in the space below the aperture 12 are directed toward the surface of the toner carrying roller 18. These toners 22 do not pass through the aperture 12 because they receive an electrostatic force directed toward.

Further, the aperture 1 is formed on the surface of the recording medium 3.
While one row of toner 22 is formed by the two rows, the recording medium 3 is conveyed by one pixel in the direction perpendicular to the row of the apertures 12 (direction of arrow B in FIG. 1). By repeating such operations, a predetermined image is formed by the toner 22 on the surface of the recording medium 3. Then, the toner image is fixed on the recording medium 3 at the fixing device 5.

In the image forming apparatus constructed as described above, if the insulating toner 22 is used, the electrical insulation between the conductive magnetic brush 17 and the control electrode 13 of the aperture electrode body 1 is maintained, and the aperture 12 is maintained. Is not subject to dielectric breakdown. As described above, in the present invention, the toner 22 carried in the charged state on the surface of the conductive magnetic brush 17, and
The electrically conductive magnetic brush 17 is rubbed by the insulating sheet 11 in the aperture electrode body 1 and then drops off to form a cloud of charged toner 22 which is conveyed to the vicinity of the aperture 12 in a dense state and has conductivity. The magnetic brush 17 functions as a kind of reference electrode, and the aperture 12
In the vicinity, the conductive magnetic brush 17 which is one of the electrodes
Since the distance between the control electrode 13 and the control electrode 13, in other words, the distance between the two electrodes, is extremely short, a sufficiently high print density can be obtained even with a low potential difference (control voltage).

Further, by using a drive circuit (IC) having a low output voltage as the control voltage application circuit 25, the image forming control operation can be executed, so that the manufacturing cost of the image forming apparatus can be reduced. You can do it. Further, when the thickness of the insulating sheet 11 is reduced in the conventional technique, there is a problem that the tensile strength of the entire aperture electrode body 1 and the like are lowered and durability is extremely deteriorated. By forming the conductive magnetic brush 17 on the surface of the roller 18, the control electrode 13 is brought very close to the inside of the aperture 12 in the aperture electrode body 1.
The opposing electrode (conductive magnetic brush 17) can be exposed, and the force of attracting the toner 22 toward the surface of the recording medium 3 can be increased without reducing the thickness of the entire aperture electrode body 1. However, the durability of the aperture electrode body 1 is also improved.

In the above embodiment, the length of the conductive magnetic brush 17 after passing through the regulating blade 20 is set to about 1 mm, but the length is not limited as long as the contact with the aperture electrode body 1 is stable. Absent.

[0026]

As described above, according to the present invention, the surface of the toner transporting means for carrying and transporting the electrically insulating toner is disposed close to the aperture of the aperture electrode body, and the aperture electrode is provided. An image forming apparatus that controls the passage of toner particles through an aperture by applying an image signal to the body, and obtains an image on a recording medium disposed on the opposite side of the toner transport means with the aperture electrode body interposed therebetween. The aperture electrode body is constituted by a sheet-like electric insulating means and a control electrode attached to the electric insulating means, while the toner carrying means is constituted so as to also serve as an electrode, and the conductive magnetic powder is used. A body magnetic brush is configured to convey the electrically insulating toner, and a portion of the magnetic brush is configured to contact the sheet-shaped electrical insulating means. The control electrode and the conveying means in the aperture electrode is obtained and a voltage applying circuit for applying a predetermined potential.

Therefore, the toner carried in a charged state on the surface of the toner conveying means composed of a conductive magnetic brush is rubbed by the sheet-like insulating means in the aperture electrode body and then falls off to become a cloud shape. The charged toner is conveyed near the aperture with a high density. Further, when a predetermined control voltage is applied between the toner transporting means and the control electrode of the aperture electrode body, the conductive magnetic brush as the toner transporting means serves as one reference electrode, so that the toner is moved toward the aperture. Since the range of the electric field for controlling by electrostatic force can be made wider than the conventional one, a remarkable effect that a sufficiently high print density can be obtained even with a low potential difference (control voltage) is obtained. Play.

According to a second aspect of the present invention, in the toner conveying means according to the first aspect, a magnet roller is arranged in an inner diameter portion of a toner carrying roller made of a metal cylinder so that both rollers rotate in a relative direction. In this configuration, the electrodes are applied to the toner carrying roller. Therefore, when the toner carrying roller is rotated in a predetermined direction while the magnet roller is rotated in the opposite direction while a predetermined voltage is applied to the toner carrying roller made of a metal cylinder, the outer periphery of the toner carrying roller made of a metal cylinder is rotated. A magnetic brush made of conductive magnetic powder is formed on the surface, and an electrically insulating toner is carried on the magnetic brush in a charged state. Then, as the toner carrying roller rotates, the toner is rubbed together with the magnetic brush by the sheet-shaped insulating means in the aperture electrode body, and then falls off into a cloud shape, and the toner in the charged state has a high density in the vicinity of the aperture. It is transported in the state. Further, when a predetermined control voltage is applied between the toner carrying roller and the control electrode of the aperture electrode body, the conductive magnetic brush serves as one of the reference electrodes, so that the movement of the toner toward the aperture is controlled by the electrostatic force. Since the range of the electric field for can be made wider than the conventional one, even if the potential difference (control voltage) is low,
There is a remarkable effect that a sufficiently high print density can be obtained.

[Brief description of drawings]

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

FIG. 2 is a perspective view of an aperture electrode body.

FIG. 3 is an enlarged side sectional view of a main part.

[Explanation of symbols]

 1 Aperture Electrode 2 Back Electrode 3 Recording Medium 8 Toner Supplying Device 11 Insulating Sheet 12 Aperture 13 Control Electrode 14 Carrier 16 Toner Conveying Means 17 Conductive Magnetic Brush 18 Toner Carrier Roller 19 Magnet Roller 22 Insulating Toner 25 Control Voltage Application Circuit

Claims (2)

[Claims] 1. Toner particles are provided by arranging a surface of a toner carrying means carrying and carrying an electrically insulating toner close to an aperture in an aperture electrode body, and applying an image signal to the aperture electrode body. Is an image forming apparatus that controls the passage of the aperture of the recording medium and obtains an image on a recording medium disposed on the opposite side of the toner transport means with the aperture electrode body interposed therebetween. Means and a control electrode attached to the electrically insulating means, while the toner conveying means is constituted so as to also serve as an electrode, and the electrically insulating toner is conveyed by a magnetic brush made of conductive magnetic powder. Is configured so that a part of the magnetic brush contacts the sheet-like electrical insulating means, and the control electrode and the toner in the aperture electrode body are connected to each other. An image forming apparatus comprising: a voltage applying circuit that applies a predetermined potential to the conveying unit. 2. The toner carrying means is configured such that a magnet roller is arranged in an inner diameter portion of a toner carrying roller made of a metal cylinder, the both rollers rotate in relative directions, and an electrode is applied to the toner carrying roller. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as described above.