JPH0930031A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an image forming apparatus capable of performing stable printing of high image quality. SOLUTION: A transfer unit 30 is constituted of a back electrode roller 31, a transfer roller 32, a transfer belt 33, a tension roller 34, a pressure roller, a cleaning blade 36 and a waste toner case 37. At a time of usual printing, the transfer belt 33 and an aperture electrode element are in a non-contact state but, at a time of cleaning, the back electrode roller 31 is moved to be brought into contact with the aperture electrode element 1 and slid around the aperture of the aperture electrode element 1 to remove bonded toner 39 and the cleaning blade 36 and the waste toner case 37 approach the transfer belt 33 to recover the bonded toner 39.

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 for a copying machine, a printer, a plotter, a facsimile, 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 a method in which toner particles are controlled so that they can pass through the aperture and an image is formed on a support such as paper 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 charged toner particles so that the flow of toner particles passing through the aperture is modulated by an electric potential, and a means for positioning the support in the particle flow path so that the support and the aperture electrode body can move relative to each other. 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.

[0006] Here, the off-time means the time when the toner particles are not adhered to the support, that is, the time when a blank portion of the image is formed. At the time when a toner image is formed.

Further, in the specification of US Pat. No. 5,305,026, there is disclosed a system in which an intermediate medium is arranged between an aperture electrode body and a support, a toner image is once formed on the intermediate medium and then transferred to the support. Invented. According to this method, since the gap between the aperture electrode body and the intermediate medium is accurately determined, the printing characteristics are improved, and various types of supports can be applied, which is very applicable.

[0008]

However, the conventional image forming apparatus as described above has the following problems. That is, when printing with the aperture electrode body,
Toner sometimes adhered to the periphery of the aperture and became a deposit. If such a substance adheres to the vicinity of the aperture, the flying of the toner is disturbed at the time of printing and the intermediate medium is contaminated, resulting in deterioration of the quality of the output image.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of stably forming an image of high quality.

[0010]

In order to achieve this object, an image forming apparatus according to a first aspect of the present invention is provided with a carrier for supporting and supplying charged particles, and the carrier and the charged particles. And an intermediate medium arranged between the electric field control means and the image receptor to control the flight of the charged particles by directly controlling the electric field, and formed on the intermediate medium by the electric field control means. The image forming apparatus for transferring the formed image onto the image receiving body is provided with a cleaning unit for cleaning the electric field control unit on the intermediate medium. Therefore, when the carrier supplies the charged particles to the electric field control means while supporting them, the electric field control means directly controls the electric field to control the flight of the charged particles, and the intermediate medium receives the image formed by the electric field control means. Transfer to the body. Then, the cleaning unit causes the intermediate medium to clean the electric field control unit.

An image forming apparatus according to a second aspect of the present invention comprises a cleaning means for cleaning the electric field control means by bringing the intermediate medium into contact with the electric field control means. Therefore, the cleaning unit cleans the electric field control unit by bringing the intermediate medium into contact with the electric field control unit.

The image forming apparatus according to claim 3 is
A cleaning unit having a stripping unit for stripping the charged particles attached to the intermediate medium is provided. Therefore, the stripping unit of the cleaning unit strips the charged particles attached to the intermediate medium.

[0013]

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

First, the overall structure of the image forming apparatus will be described with reference to FIG.

An image forming apparatus according to an embodiment of the present invention is
A toner supply device 10 is provided below the toner supply device 10, and an aperture electrode body 1 as an electric field control means for controlling the toner flow is provided above the toner supply device 10.
A transfer unit 3 serving as an intermediate medium is provided above the aperture electrode body 1 while maintaining a space from the aperture electrode body 1.
0 is provided. Further, in the gap between the transfer unit 30 and the pressure roller 35, the image recording medium 20 as an image receiving member on which an image is formed by toner is inserted and conveyed in the direction of arrow C. Then, the image recording medium 2 being conveyed
A fixing device 26 that fixes an image on the image recording medium 20 is provided in the transport direction of 0.

Next, details of each part of the image forming apparatus will be described with reference to the drawings.

As shown in FIG. 1, the toner supply device 10 is provided with a toner case 11 which also serves as a housing of the entire toner supply device 10. In the toner case 11, toner 16 as charged particles is stored. A toner carrier roller 14 as a cylindrical carrier that carries the toner 16 and conveys it to the aperture electrode body 1 is rotatably supported in the toner case 11 in the direction of arrow B. In FIG. 1, the toner 16 accumulated in the toner case 11 is provided on the lower left portion of the toner carrying roller 14.
Is provided to the toner carrying roller 14, and the cylindrical supplying roller 12 is provided. The supplying roller 12 and the toner carrying roller 14 are arranged in parallel with each other, and the generatrix of the cylindrical surface thereof is in contact with each other.

In the toner case 11, above the supply roller 12, the amount of the toner 16 carried by the toner carrying roller 14 is adjusted so as to be uniform on the roller surface of the toner carrying roller 14. A toner layer regulating blade 18 for uniformly charging the toner 16 is provided, and one end of the toner layer regulating blade 18 is pressed against the toner carrying roller 14.

Next, the aperture electrode body 1 will be described with reference to the drawings.

As shown in FIG. 2, the aperture electrode body 1 comprises a polyimide insulating sheet 2 having a thickness of 25 μm. The insulating sheet 2 has a plurality of circular apertures 6 having a diameter of 60 μm. The electrodes 1 are formed in a line in the longitudinal direction. Further, a control electrode 4 made of a copper foil having a thickness of 8 μm is formed around each aperture 6 for each aperture 6.

Here, the aperture 6 is not necessarily limited to the circular shape as shown in FIG. 2, and for example, one side has 6 sides.
The shape may be a quadrangle of 0 μm, or may be oval, triangular, parallelogram, or the like.

Next, the aperture 6 of the aperture electrode body 1
The positional relationship between the toner carrying roller 14 and the toner carrying roller 14 will be described in detail. As shown in FIG.
5 is arranged so as to pass through the uppermost portion of the peripheral surface of the toner carrying roller 14 and the central shaft 16 of the toner carrying roller 14. According to this, the respective apertures 6 are evenly arranged on the left and right with respect to the uppermost portion of the peripheral surface of the toner carrying roller 14, so that the distribution of the toner 16 passing through the apertures 6 is distributed over the entire area of the aperture. Can be uniform. Further, since the wall surface of the aperture 6 and the flying direction of the toner 16 are parallel to each other, it is possible to stably fly the toner.

Further, the aperture electrode body 1 itself is pressed against the toner carrying roller 14 so as to bend to the left and right about the aperture 6 by the same angle, as shown in the figure. This makes it possible to increase the contact area between the aperture electrode body 1 and the toner carrying roller 14, and
Since the periphery of the lower portion of the aperture 6 can be pressed uniformly to the left and right, it is possible to suppress the occurrence of toner density unevenness as much as possible.

Next, the control device for each electrode will be described. As shown in FIG. 1, a control voltage applying 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 -30V or + 30V to the control electrode 4 based on an image signal sent from an image signal receiving means (not shown). The carrying roller 14 is grounded. The image signal receiving means (not shown) is connected to an external computer, image reading device, image communication device, or the like.

Now, the transfer unit 30 which is the main part of the present invention will be described.

The transfer unit 30 includes an endless transfer belt 33 as a center, and a back electrode roller 31, a transfer roller 32, a pair of tension rollers 34, and a pressure roller 35 arranged on the back surface of the paper inside. It is configured. Further to the side, a cleaning blade 36
And a waste toner case 37 are provided.

The back electrode roller 31 has a cylindrical shape made of metal, is rotatably provided on the chassis 40 as shown in FIG. 4, and moves up and down in the direction of the aperture electrode body 1 by the drive motor 41 together with the chassis 40. It is possible. A DC power supply 24 is connected to the back electrode roller 31, and this DC power supply 24 is connected to the back electrode roller 3
+1 kV or 0 V can be applied to 1. The transfer roller 32 also has a metal cylindrical shape, and the transfer belt 33 can be pressed against the image recording medium 20 in cooperation with the pressure roller 35. The transfer belt 33 is a semi-conductive resin belt, and normally forms a toner image on its surface and transfers the toner image at the contact portion with the image receiver. The tension roller 34 is a member that applies tension so that the transfer belt 33 does not sag, is movable in the left-right direction in FIG. 4, and is always urged outward by a spring or the like.

The cleaning blade 36 as a stripping means strips and removes the adhered toner on the transfer belt 33 so as to scrape it off. Waste toner case 37
Is configured to accommodate and store the toner removed by the cleaning blade 36. The cleaning blade 36 and the waste toner case 37 are provided on the chassis 42.
And a chassis 42 and a drive motor 43.

A CPU 44 for controlling the driving of both drive motors 41 and 43 is provided. Therefore,
The cleaning blade 36 and the waste toner case 3
7, the drive motors 41 and 43, and the CPU 44 constitute the cleaning means of the present invention.

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

First, the toner supply operation will be described with reference to FIG.

By rotating the supply roller 12 in the direction of arrow A, the toner 16 stored in the toner case 11 is conveyed toward the toner carrying roller 14. Then, the conveyed toner 16 is rubbed against the toner carrying roller 14 and is negatively charged and carried on the toner carrying roller 14. The toner 16 carried on the toner carrying roller 14 is conveyed while being carried on the cylindrical roller surface of the toner carrying roller 16 as the toner carrying roller 14 rotates in the direction of the arrow B, and is thinned by the toner layer regulating blade 18. After being layered and uniformized in charge, the toner carrying roller 14 is conveyed toward the aperture electrode body 1 by rotating in the direction of arrow B. Then, the toner on the toner carrying roller 14 is supplied under the aperture 6 while being rubbed by the insulating sheet 2 of the aperture electrode body 1.

Next, the image forming operation will be described with reference to FIGS. 1, 2 and 3.

The control voltage applying circuit 8 applies a voltage of +30 V to the control electrode 4 corresponding to the image portion in accordance with the image signal sent from the image signal receiving means (not shown). As a result, due to the potential difference between the control electrode 4 and the toner carrying roller 14, an electric force line from the control electrode 4 toward the toner carrying roller 14 is formed in the aperture 6 in the control electrode 4 to which the voltage is applied. As a result, the negatively charged toner 16 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 to the control electrode 4 side. The extracted toner 16 is applied to the back electrode roller 31 by the DC power supply 24 + 1k.
The image recording medium 20 and the aperture electrode body 1 by the voltage of V
By the electric field formed between and, the particles fly toward the transfer belt 33 and are accumulated to form pixels.

A voltage of -30 V 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 16 on the toner carrying roller 14 does not receive the electrostatic force and therefore does not pass through the aperture 6. Therefore, no pixel is formed in the portion of the transfer belt 33 facing the control electrode 4.

Here, when one row of pixels is formed on the surface of the transfer belt 33 by the toner 16, the transfer belt 33 is then moved by the conveying means (not shown) in the direction perpendicular to the six rows of apertures.
Pixels are conveyed. Then, the toner image is formed on the entire surface of the transfer belt 33 by repeating the above-described image forming process.

By repeating the above process,
An image is recorded on the transfer belt 33.
As shown in FIG. 5, excessive adhered toner 39 is generated around the aperture 6 during printing. The attached toner 39 is a so-called uncontrollable toner, and its charging characteristics and mechanical characteristics are not suitable for printing. The inventor of the present invention has studied to reduce the amount of such toner, but at present, it is difficult to eliminate all of them. If the adhering toner 39 is generated in the vicinity of the aperture 6, the controlled flight of the toner may be hindered, or the adhering toner 39 may adhere to the conveyed paper and stain the image.

Therefore, as a countermeasure against the adhered toner 39, its operation will be described with reference to FIGS. 4 and 5. FIG. 4 shows a state of the transfer unit 30 during normal image formation, and FIG. 5 is an explanatory diagram showing a state of the transfer unit 30 during cleaning. Normally, the transfer unit 30
4 is arranged as shown in FIG. 4, and when the adhered toner 39 is generated, the CPU 44 rotates the drive motor 41 and moves the rear electrode roller 31 together with the chassis 40 to the aperture electrode body 1 side during the non-printing period. Note that the tension rollers 34, 3
4 moves inward.

Then, when the transfer belt 33 wound around the back electrode roller 31 rubs the surface of the aperture electrode body 1, the adhered toner 39 is taken into the transfer belt 33 side and conveyed. That is, the transfer belt 33 can clean the surface of the aperture electrode body 1 around the aperture 6. In this manner, the transfer belt 33 is brought into contact with the aperture electrode body 1 to remove the adhered toner 39, so that the surface of the aperture electrode body 1 around the aperture 6 can be reliably cleaned.

The attached toner 39 is placed on the transfer belt 33 and arrives near the cleaning blade 36. At this time, the CPU 44 rotates the drive motor 43 to move the cleaning blade 36 and the waste toner case 37 together with the chassis 42 to the transfer belt 33 side, and particularly the tip of the cleaning blade 36 is arranged at a position in contact with the transfer belt 33. As a result, the cleaning blade 36 removes the toner 39 from the transfer belt 33.
The waste toner 3 in the waste toner case 37
Keep as 8. In this way, the toner 39 attached to the transfer belt 33 is peeled off by the cleaning blade 36, so that it is possible to perform good image formation without contaminating the image recording medium 20.

The non-printing time in this embodiment means not only the time during which no printing is performed by image data on one image recording medium, but also the clearance between the image recording mediums conveyed continuously. Indicates the time when toner is not used for printing, including the time it takes to pass under the aperture electrode, the time to start the machine and start printing, the time to finish printing and stop the machine, etc. There is.

After that, the formed toner image is conveyed to the fixing device 26 by a conveying device (not shown), and is fixed on the image recording medium 20 by the fixing device 26. Note that the fixing device 26 may be any type of a heat fixing system or a pressure fixing system.

Further, in the image forming apparatus of this embodiment, the insulating sheet 2 of the aperture electrode body 1 has the toner carrying roller 14
Since the toner is directed to the side, even if the toner 16 is not present on the toner carrying roller 14 due to a malfunction of the toner supply system, the control electrode 4 and the toner carrying roller 14 are in contact with each other and electrically short-circuited. Never break 8.

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.

Although the belt is used as the transfer member in this embodiment, a cylindrical transfer roller may be used.

In the present invention, the toner attached to the waste toner case is stored and discarded, but as shown in the specification and drawings of Japanese Patent Application No. 7-118348 filed by the present applicant, this toner is used. It is also possible to recycle the toner by returning it to the toner case of the printing unit again.

Further, in the above embodiment, the control voltage of the aperture corresponding to the non-image portion is set to -30V, but this may be zero voltage. In this case, lower voltage driving is possible.

In the above embodiment, the aperture electrode body is used as the toner flow control means. For example, a stitched electrode body as described in the specification of US Pat. No. 5,036,341 or JP-A-6- It is also possible to use the edge electrode body described in JP-A-255163.

[0049]

As is apparent from the above description,
In the image forming apparatus according to the first aspect of the present invention, since the electric field control means can be cleaned by the intermediate medium, stable and high quality image formation can be performed.

Further, in the image forming apparatus according to the second aspect, the electric field control means is cleaned by bringing the intermediate medium into contact with the electric field control means, so that the charged particles attached to the electric field control means can be surely removed.

Furthermore, in the image forming apparatus according to the third aspect of the present invention, since the charged particles that have been removed from the electric field control means and adhered to the intermediate medium can be stripped off, the charged particles adhered to the intermediate medium stain the image receptor. It is possible to form a good image without causing any trouble.

[Brief description of drawings]

FIG. 1 is a front view showing the configuration of an image forming apparatus that is an embodiment of the present invention.

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

FIG. 3 is a front view showing a positional relationship between an aperture electrode body and a toner carrying roller used in the image forming apparatus.

FIG. 4 is an explanatory diagram showing an operation of a transfer unit used in the image forming apparatus during normal image formation.

FIG. 5 is an explanatory diagram showing an operation at the time of cleaning a transfer unit used in the image forming apparatus.

[Explanation of symbols]

 1 Aperture electrode body 14 Toner carrying roller 30 Transfer unit 31 Rear electrode roller 33 Transfer belt 36 Cleaning blade 37 Waste toner case 40 Chassis 41 Drive motor 42 Chassis 43 Drive motor 44 CPU

Claims (3)

[Claims] 1. A carrier for supporting and supplying the charged particles, an electric field control means for controlling the flight of the charged particles by directly controlling the electric field while being arranged via the carrier and the charged particles, and the electric field control thereof. And an intermediate medium disposed between the image receiving body and the image receiving apparatus, wherein the image formed on the intermediate medium by the electric field controlling means is transferred onto the image receiving body, the intermediate medium having the electric field controlling means. An image forming apparatus comprising a cleaning unit for performing cleaning. 2. The image forming apparatus according to claim 1, wherein the cleaning unit cleans the electric field control unit by bringing the intermediate medium into contact with the electric field control unit. 3. The image forming apparatus according to claim 1, wherein the cleaning unit has a stripping unit for stripping the charged particles attached to the intermediate medium.