JPH07108705A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To provide an image forming apparatus equipped with a recording means which gives a high quality image and suffers less troubles. CONSTITUTION:In an image forming apparatus, an insulating coating film 5 is placed on an insulating sheet 2 except the control electrode 4 of an aperture electrode body 1. The thickness of the insulating film 5 is greater than at least that of the control electrode 4. In this way, great electric field strength can be applied to a toner layer between a carrier and the aperture electrode body 1 so that low voltage driving is made possible, and troubles due to the short between the carrier and the aperture electrode can be prevented.

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 which can be used in copying machines, printers, plotters, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, as one of image forming apparatuses, an electrode having a plurality of openings (hereinafter referred to as apertures) is used, and a voltage is applied to the electrode based on image data. U.S. Pat. No. 3,689,935 discloses controlling toner particles so that they can pass through the aperture and forming an image on a support by the toner particles that have passed.

This image forming apparatus comprises a flat plate made of an insulating material, a continuous reference electrode formed on one surface of the flat plate, and a plurality of control electrodes insulated from each other formed on the other surface. , An aperture electrode body having at least one row of apertures formed through each of the control electrodes, and a means for selectively applying a potential between the reference electrode and the control electrode. A means for supplying the charged toner particles so that the flow of the toner particles passing through the aperture is modulated by the electric potential, and a means for relatively moving the support and the aperture electrode body to position the support in the particle flow path. It consists of and.

Also, for example, US Pat. No. 4,743,926.
Nos. 4,755,837, 4,780,733, and 4,847,796 disclose an image forming apparatus in which an aperture electrode body is arranged with a control electrode on the support side and a reference electrode on the toner supply side. There is.

In contrast, US Pat. No. 4,912,489
In the specification of the above U.S. Pat. No. 5,967,967, the voltage applied to the control electrode when the aperture electrode body is off is disclosed by disposing the aperture electrode body with the reference electrode on the support side and the control electrode on the toner supply side. It is described that it can be suppressed to about 1/4 as compared with the image forming apparatus.

Further, in the conventional image forming apparatus, in order to drive the toner at a lower voltage, a control electrode is provided on the toner supply side of the aperture electrode body, and discharge control is entirely performed on the control electrode. In some cases, an insulating film was formed for this purpose.

[0007]

However, in the conventional image forming apparatus as described above, since the insulating film is formed over the entire surface of the aperture electrode body, the dielectric gap is formed only by controlling the electric field. Has been done,
It could not be said that it was an efficient electric field control configuration. Naturally, it is also considered to remove the insulating coating film, but in that case, for example, a toner which constitutes the toner supply means is used.
In the case of an abnormality where toner is not on the carrier roller,
The grounded toner carrying roller and the control electrode to which a voltage was applied were brought into close contact with each other to cause discharge, which sometimes destroyed the control electrode.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide an image forming apparatus which can be driven at a low voltage and has a safe structure.

[0009]

In order to achieve this object, an image forming apparatus of the present invention comprises a carrier for supporting and supplying charged particles, the carrier is arranged via charged particles, and is charged by an electric field. An electric field control unit having a control unit for controlling the flow of particles, and the electric field control unit is an image forming apparatus composed of counter electrodes arranged with an image receptor interposed therebetween,
An insulating coating layer is provided on a portion of the electric field control unit except at least the control unit.

[0010]

In the image forming apparatus of the present invention having the above structure, the insulating coating layer is disposed only in the portion excluding at least the control portion, so that the toner layer sandwiched between the carrier and the electric field control means is formed. Makes it possible to apply a very strong electric field force. Further, since the insulating coating layer is also provided, it is possible to prevent a trouble due to a short circuit between the carrier and the electric field control means.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an outline of an image forming apparatus of the present invention. A cylindrical rear electrode roller 22 having a gap of 1 mm above the aperture electrode body 1 as an electric field control means. Is rotatably disposed on a chassis (not shown), and is configured to be able to convey the support 20 inserted into the gap. In addition, below the aperture electrode body 1, along the longitudinal direction of the aperture electrode body 1,
A toner supply device 10 is provided, and further, a fixing device 26 is provided at the destination of the support body 20 conveyed by the back electrode roller 22.

Next, the respective components will be described in detail. In the toner supply device 10, the toner case 11 also serving as a housing of the entire device, the toner 16 housed in the toner case 11, and the supply roller 12 are provided. And a toner carrying roller 14 and a toner layer regulating blade 18. Here, the toner carrying roller 1
Reference numeral 4 is for carrying the toner 16 and carrying it toward the aperture electrode body 1, and the supply roller 12 is for supplying the toner 16 to the toner carrying roller 14.

The supply roller 12 and the toner carrying roller 14 are rotatably supported by the toner case 11 in the direction of the arrow shown in FIG. Further, the toner layer regulating blade 18
Is for adjusting the amount of the toner 16 carried on the toner carrying roller 14 to be uniform on the roller surface and for uniformly charging the toner 16, and is pressed against the toner carrying roller 14. .

The aperture electrode body 1 will be described with reference to FIGS. 2 and 4. 2 is a perspective view of the aperture electrode body, FIG. 4 (a) is a bottom view of the aperture electrode body, and FIG. 4 (b) is a sectional view taken along the line AA ′ in FIG. 4 (a).

In the aperture electrode body 1, a plurality of apertures 6 having a diameter of 100 μm are formed in a row on a 25 μm thick insulating sheet 2 made of polyimide, and a thickness of 1 μm is controlled on the lower surface facing the toner carrier roller 14. Electrode 4 is each aperture 6
It is formed for each. On the lower surface of the insulating sheet 2,
An insulating coating film 5 is applied to the portion excluding the control electrode 4 and the aperture 6. The insulating coating film 5 is made of an insulating material such as polyimide, polyimideamide, epoxy, polyamide, or another resin material, or an inorganic material such as silicon dioxide, tantalum nitride, or chromium oxide.
Can be used. Then, a sectional view of the aperture electrode body 1 is shown in FIG.
As shown in (b), the thickness of the insulating coating film 5 is set to be at least larger than the thickness of the control electrode 4.

Further, in the aperture electrode body 1, as shown in FIG. 1, with the control electrode 4 facing the toner carrying roller 14 side, the toner carrying roller 14 is positioned at the position of the aperture 6 of the insulating sheet 2. Pressed.

Here, the positional relationship between the aperture 6 of the aperture electrode body 1 and the toner carrying roller 14 will be described in detail. As shown in FIG. 3, each center line 30 of each aperture 6 has a toner carrying roller 14. It is arranged so as to pass through the uppermost portion of the peripheral surface of and the central shaft 32 of the toner carrying roller 14. According to this, each aperture 6
Based on the uppermost part of the peripheral surface of the toner carrying roller 14,
By arranging them evenly on the left and right, the distribution of the toner 16 passing through each aperture 6 can be made uniform over the entire area of the aperture. In addition, the wall surface of the aperture 6 and the toner 16
Since the flying direction of the toner is parallel to the flying direction of the toner, it is possible to stably fly the toner.

Further, the aperture electrode body 1 itself has an aperture 6 with respect to the toner carrying roller 14 as shown in FIG.
It is pressed so that it bends to the left and right about the same angle. As a result, the contact area between the aperture electrode body 1 and the toner carrying roller 14 can be increased, and the lower periphery of the aperture 6 can be pressed uniformly to the left and right, so that uneven toner concentration is minimized. Can be suppressed.

A control voltage application circuit 8 is connected between the control electrode 4 and the toner carrying roller 14.
The control voltage application circuit 8 is configured to apply a voltage of 0 V or +50 V to the control electrode 4 based on the image signal.

Further, a DC power source 24 is connected between the back electrode roller 22 and the toner carrying roller 14, and this DC power source is + with respect to the back electrode roller 22.
A voltage of 1 kV can be applied.

Next, the operation of the image forming apparatus configured as described above will be described.

First, by rotating the toner carrying roller 14 and the supply roller 12 in the direction of the arrow shown in FIG. 1, the toner 16 sent from the supply roller 12 is rubbed against the toner carrying roller 14 and is negatively charged. The toner is carried on the toner carrying roller 14. The carried toner 16 is thinned and charged by the layer regulating blade 18, and then is conveyed toward the aperture electrode body 1 by the rotation of the toner carrying roller 14. Then, the toner on the toner carrying roller 14 is supplied to the bottom of the aperture 6 while being rubbed by the insulating sheet 2 of the aperture electrode body 1.

Here, in accordance with the image signal, the control voltage applying circuit 8 adds + to the control electrode 4 corresponding to the image portion.
A voltage of 50V is applied. As a result, an electric force line from the control electrode 4 toward the toner carrying roller 14 is formed in the vicinity of the aperture 6 corresponding to the image portion due to the potential difference between the control electrode 4 and the toner carrying roller 14. As a result, the negatively charged toner receives an electrostatic force in the direction of higher electric potential, passes through the aperture 6 from the toner carrying roller 14, and is drawn out to the control electrode 4 side. The extracted toner 16 further flies toward the support body 20 due to the electric field formed between the support body 20 and the aperture electrode body 1 by the voltage applied to the back electrode 22, and on the support body 20. To form pixels.

A voltage of 0V is applied from the control voltage applying circuit 8 to the control electrode 4 corresponding to the non-image portion.
As a result, since no electric field is formed between the toner carrying roller 14 and the control electrode 4, the toner carrying roller 1
The toner 16 on 4 does not pass through the aperture 6 because it is not subjected to electrostatic force.

At this time, the insulating coating film 5 formed on the aperture electrode body is formed, and the dielectric gap is surely formed between the control electrode 4 and the toner carrying roller 14.
Therefore, even if the toner supply is interrupted and the two are in close contact with each other, at least the insulating coating film near the control electrode is
Since it is thicker than the thickness of the control electrode, it does not cause a short circuit and does not cause a big obstacle. Further, since the insulating coating layer 5 is not arranged on the control electrode 4,
No extra dielectric gap is formed, and toner is supplied in contact with the control electrode. Therefore, a large electric field force can be applied to the toner layer from the control electrode 4. As a result, good controllability of the toner is obtained, and the print quality is improved.

Further, the support 20 is fed by one pixel in the direction perpendicular to the aperture row while the toner 16 forms one row of pixels on the surface thereof. Then, the toner image is formed on the entire surface of the support 20 by repeating the above process. Then, the formed toner image is fixed on the support 20 by the fixing device 26.

If an insulating toner is used in the image forming apparatus constructed as described above, the toner carrying roller 14 is used.
The insulation between the control electrode 4 and the control electrode 4 is maintained, and the aperture 6 does not cause dielectric breakdown.

In the above process, the control electric field generated by the control electrode 4 is formed between the control electrode 4 and the inside of the aperture 6, and between the aperture 6 and the toner carrying surface of the toner carrying roller 14 which faces the aperture 6. Toner 1
Since the control electric field can be directly applied to 6, the control efficiency is good.

Further, even if a part of the supplied toner 16 receives a mechanical force or the like by sliding with the aperture electrode body 1 and enters the aperture 6 corresponding to the non-image portion, inside the aperture 6 Since it can be controlled so as not to pass through the aperture 6 by the electric field, the toner controllability is good.

Further, since the toner carrying roller 14 and the aperture electrode body 1 are opposed to each other with the toner layer in between, the control voltage can be lowered and the inexpensive drive element can be provided because they can be arranged at a relatively short distance. Can be used.

In addition, the insulating sheet 2 of the aperture electrode body 1
Is directed toward the toner carrying roller 14 side, so that the toner
Even if 6 is not present, the control electrode 4 and the toner carrying roller 14 do not come into contact with each other and electrically short-circuit, and the drive element is not destroyed.

Further, since the aperture electrode body 1 and the toner 16 on the toner carrying roller 14 are in contact with each other at the entrance portion of the aperture 6, the toner 16 accumulated at the entrance portion of the aperture 6 is not supported. Since the toner 16 is pushed away by the toner sequentially supplied, the toner 16 does not accumulate and bridge to block the aperture 6.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention.

For example, in the above embodiment, the control voltage of the aperture corresponding to the non-image portion is set to 0V, but this may be a negative voltage. In this case, an image with less fogging can be obtained. Further, in the above embodiment, the aperture electrode body is used as the toner flow control means, but it is also possible to use, for example, a knitted electrode body as described in the specification of US Pat. No. 5,036,341.

It is also possible to have a configuration as shown in FIG. FIG. 5 is a drawing showing a second embodiment of the present invention, and FIG. 5 (a) is a sectional view of an aperture electrode body,
FIG. 5B is a sectional view taken along the line AA ′ of FIG.
In the description, parts having the same functions as those of the above-described embodiment are designated by the same reference numerals.

In this embodiment, the insulating coating layer 5 and the control electrode 4 are constructed so as to have the same height, that is, a smooth surface texture. This shape also makes it possible to have a substantially satisfactory short-circuit failure prevention function. Further, in this embodiment, by eliminating the step between the control electrode and the insulating coating layer, there is no obstacle to the passage of toner, and a good toner supply state can be realized.

[0038]

As is apparent from the above description, in the image forming apparatus of the present invention, since the insulating coating layer is arranged at the portion excluding at least the control portion, it is sandwiched between the carrier and the aperture electrode body. An extremely strong electric field force can be applied to the toner layer. Further, since the insulating coating layer is also provided, it is possible to prevent a trouble due to a short circuit between the carrier and the aperture electrode. As a result, it is possible to realize an excellent image forming apparatus having good recording characteristics and less likely to cause trouble.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment embodying the configuration of an image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a configuration of an aperture electrode body used in the image forming apparatus of the present invention.

FIG. 3 is a diagram schematically showing a configuration of an aperture electrode body and a toner carrying roller used in the image forming apparatus of the present invention.

FIG. 4 is a bottom view and a cross-sectional view showing a configuration of an aperture electrode body.

5A and 5B are a bottom view and a top view of an aperture electrode body showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Aperture electrode body 2 Insulating sheet 4 Control electrode 5 Insulating coating layer 6 Aperture 8 Control voltage application circuit 14 Toner carrier roller 22 Back electrode roller 24 DC power supply

Claims (2)

[Claims] 1. A carrier for supporting and supplying charged particles, an electric field control unit which is disposed with the carrier interposed therebetween and which controls a flow of the charged particles by an electric field, and the electric field control. In the image forming apparatus, the means includes an opposing electrode arranged with an image receptor interposed therebetween, and an image forming apparatus is characterized in that an insulating coating layer is provided on a portion of the electric field control means except at least a control unit. apparatus. 2. The control section is composed of a control electrode provided on the peripheral edge of an aperture of an aperture through which charged particles can pass, and the insulating coating layer is provided on a portion of the electric field control means excluding the control electrode. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided.