JP3402906B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a main body of a printing section of a digital copying machine and a facsimile machine, a digital printer, a plotter, etc., and an image is recorded on a recording medium such as a recording paper by flying visible particles. The present invention relates to an image forming apparatus that directly forms a sheet.

[0002]

2. Description of the Related Art In recent years, as an image forming apparatus for outputting a visible image on a recording medium such as a recording paper according to an image signal, by directly adhering toner, which is a visualized particle, to the recording medium, An image forming apparatus for directly forming a toner image on a recording medium is proposed in, for example, Japanese Patent Laid-Open No. 6-155798.

The image forming apparatus disclosed in Japanese Patent Laid-Open No. 6-155798 will be described with reference to FIG.
An image forming unit 51 having a printing unit 53 and a printing unit 53 is provided, and the toner 71 carried by the toner supply unit 52 is selectively ejected to form a sheet-like recording paper 55 as a recording medium.
To adhere to. At this time, by controlling the flight of the toner 71 according to the image signal, the toner is selectively adhered directly onto the recording paper 55 to form a visible image.

The toner supply section 52 is composed of, for example, a toner storage section 70 that stores toner 71 as negatively charged developing particles, and a toner carrier 72 that supports the toner 71 by, for example, magnetic force. ing. The toner carrier 72 is grounded, and is rotationally driven in the direction of arrow E in the figure and at a surface speed of, for example, 30 mm / sec. The toner 71 is a magnetic toner having an average particle size of 10 μm, and has a charge amount of −4 μC / g to a known technique.
The electric charge is applied so as to be −5 μC / g. The toner 71 has an average thickness of 80 on the outer peripheral surface of the toner carrier 72.
It is supported by about μm.

The printing section 53 which constitutes the image forming section 51,
Counter electrode 75 made of aluminum with a thickness of about 2 mm
And a control electrode 76 provided between the counter electrode 75 and the toner carrier 72. The counter electrode 75 is 1 m away from the outer peripheral surface of the toner carrier 72.
They are arranged at a distance of about m. Counter electrode 75
A high voltage of, for example, 2 kV is applied by the DC power supply unit 80. That is, the counter electrode 75 and the toner carrier 7
An electric field necessary for causing the toner 71 carried by the toner carrier 72 to fly toward the counter electrode 75 is applied between the two.

A dielectric belt 73 is movably provided on the counter electrode 75 so as to be in contact with the surface of the electrode 75. The dielectric belt 73 is endless (endless)
And at least two support rollers 73a
And 73b. And the support roller 7
By driving 3b, it is driven to travel in the direction of arrow F. In order to electrostatically attract and convey the recording paper 55 to the dielectric belt 73, the charge supply roller 74, which is in contact with the dielectric belt 73 via the recording paper 55, has a recording paper 55 conveyance direction. A power supply 82 is provided on the downstream side, and is used to apply a predetermined charge to the recording paper 55 to the charge supply roller 74 and attract the recording paper 55 to the dielectric belt 73.

The control electrode 76 is parallel to the tangential direction of the surface of the counter electrode 75 and faces the counter electrode 75.
It is dimensionally spread and has a structure in which the toner flow from the toner carrier 72 toward the counter electrode 75 can pass.
The electric potential supplied to the control electrode 76 changes the electric field applied between the toner carrier 72 and the counter electrode 75, and the flight of the toner 71 from the toner carrier 72 to the counter electrode 75 is controlled. It

Therefore, when a high voltage of, for example, 1 kV is supplied to the charge supply roller 74 by the power source 82, the recording paper 55 is supplied with a negative charge due to the relationship of 2 kV supplied to the counter electrode 75. It is injected, electrostatically attracted to the dielectric belt 73, and conveyed to the area of the printing unit 53 according to the traveling speed of the dielectric belt 73.

The control electrode 76 is arranged so that the distance from the outer peripheral surface of the toner carrier 72 is, for example, 100 μm. The control electrode 76 includes a flexible printed circuit board (FPC) 76a having a thickness of 50 μm, and a ring-shaped electrode 77 made of a copper foil having a thickness of about 20 μm.
It consists of Gates 79 having a diameter of about 150 μm serving as a passage portion of the toner 71 are formed on the substrate 76a, and the ring-shaped electrodes 77 are provided around these gates 79. Each of the ring-shaped electrodes 77 is electrically connected to the control power supply unit 81 via a power supply line and a high voltage driver (neither is shown).

A voltage corresponding to an image signal is applied to the ring-shaped electrodes 77 ... By the control power supply 81. That is, the control power supply unit 81 applies, for example, 200 V to the ring-shaped electrodes 77, ... When the toner 71 carried on the toner carrier 72 is passed in the direction of the counter electrode 75. Gate 7 of ring electrode 77
It is possible to fly to the recording paper on the counter electrode side via 9. When the toner does not pass through, by applying −200 V to the ring-shaped electrode 77, the toner on the toner carrier 72 is prevented from flying to the counter electrode 75 side. In this way, by applying the above-mentioned voltage to the ring-shaped electrodes 77 ... According to the image signal, the toner can be selectively ejected and a visible image corresponding to the image signal can be directly formed on the recording paper 55. .

Here, the rotation of the toner carrier 72, the rotation of the counter electrode 75, the application of a potential that does not allow the toner 71 to pass through to the control electrode 76, and the application of the high voltage to the counter electrode are substantially simultaneously performed by a single trigger. Is applied. In addition, the flight time until the toner 71 on the toner carrier 72 reaches the recording paper 55 depends on the charge amount of the toner and the toner carrier 7.
2 and the distance between the counter electrode 75 and the applied potential difference,
In particular, it depends on the strength of the electric field. The time is 2
It is about 50 μsec, and the voltage applied to the ring electrode 77 is 300 μsec longer than the flight time.
It is set to a degree. This ensures that the toner adheres to the recording paper 55 on the counter electrode 75.

[0012]

In the conventional image forming apparatus described above, at the end of the image recording operation, the driving of the toner carrier 72 is stopped, and at the same time, the high voltage supplied to the control electrode 76 and the counter electrode 75 is applied. , Are driven so that they are shut off at the same time.

Since a high voltage is supplied to the counter electrode 75 and the control electrode 76 described above, the toner 71 carried on the toner carrier 72 has a high voltage due to the time constant even if it is cut off. The electric field due to acts. In particular, since a voltage higher than that of the control electrode 76 is supplied to the counter electrode 75, an electric field that causes the toner to fly to the counter electrode side due to the time constant even when the power supply to the counter electrode 75 is cut off. Will continue to work. Therefore, among the toners 71 carried by the toner carrier 72, there is toner that starts moving toward the counter electrode 75 and tries to pass through the gate 79.

For this reason, unnecessary toner flies at the end of image formation, adheres to the counter electrode 75, and contaminates the counter electrode 75 with the toner. In order to prevent such a situation, when the image formation is temporarily finished, it is sufficient to constantly supply a voltage to the control electrode and the counter electrode so that the toner does not fly. so,
If this is maintained, power consumption is wasted. for that reason,
When the image formation is completed, the voltage supplied to each electrode is usually released at the end.

Therefore, if the voltage supply to the counter electrode 75 and the control electrode 76 is released at the end of the image, the toner flies to the counter electrode and is contaminated with the toner as described above. When the image forming operation is restarted in this state, a problem occurs that the back surface of the recording paper 55 that is sent is soiled with toner.

Supply of high voltage to the counter electrode 75 described above,
In particular, the power supply circuit 80 or the like does not control the high voltage supply interruption control by a relay circuit or the like, but stops the oscillation operation of the voltage generation source, especially the DC-DC converter, and I'm trying to stop the generation. Therefore, the above-mentioned time constant becomes longer, and the above-mentioned problem, that is, the problem that unwanted toner after the image formation is ejected to the counter electrode 75 side and adheres becomes remarkable.

In the toner 71, the counter electrode 7
In addition to 5, some may adhere to the control electrode 76. When the image forming operation is restarted in this state, the control electrode 76
Due to the toner 71 adhering to the toner, the apparent electric potential of the ring-shaped electrodes 77, ... Is changed by the electric charge of the toner 71, and it becomes difficult to control the passage of the toner normally. Alternatively, the gate 79 for passing the toner may be clogged with the toner adhering to the control electrode 76, and in the worst case, the image formation cannot be performed.

Even if the gate 79 of the control electrode 76 is not closed by the toner 71, the toner 71 adheres to the peripheral edge of the gate 79 and narrows the opening diameter of the gate 79. When the image forming operation is restarted in this state, the flying toner 71 reaches the predetermined dot forming area on the recording paper 55 by the toner attached inside the gate 79 without following the desired flying path. Things will disappear. Therefore, if the toner 71 passes through the gate 79 and does not reach a predetermined area on the recording paper 55, fogging due to scattering or the like causes a normal image to be formed, and the toner 71 that reaches the recording paper 55 is not formed. The dots cause bleeding, resulting in a blurred image with no contrast. Therefore, halftone images,
Color reproduction of a color image becomes difficult.

Further, the toner 71 adheres to the control electrode 76 and the counter electrode 75 due to the end of the image forming operation, and the image forming apparatus is often left in the adhered state of the toner. For example, the image forming operation may be completed and left in that state until tomorrow. Therefore, the toner 71, due to its nature, agglomerates if left unattended for a long time, which makes it difficult to remove the toner 71 while it remains attached to the control electrode 76. In this case, the toner 71 cannot be removed by the electrostatic force, and it is necessary to remove the control electrode 76 from the printing section 51 and forcibly remove and clean it using an air brush or a normal cleaning brush. However, such work is very troublesome, and the work of mounting and adjusting the print unit 51 after cleaning becomes more difficult.

In view of the above-mentioned problems, it is an object of the present invention to solve the problems that occur at the end of image formation.

Another object of the present invention is to control the toner so that it will not adhere to the control electrode or the counter electrode at the end of image formation.

[0022]

Image forming apparatus for achieving the above object of the present invention In order to achieve the above object, according a carrier which provides the desired properties for the developing particles to carrying該顕image particles, the carrier bearing member Between the carrier and the counter electrode, and a control electrode having a plurality of gates which are disposed between the carrier and the counter electrode and serve as passage portions for the visualized particles. And a control means for forming an image by controlling the passage of the visualized particles through the gate by changing the potential applied to the control electrode. In the apparatus, at the end of the image forming operation, the control means is carried on the carrier.
Conveying the visualized particles carried by the above-mentioned carrier before releasing the control in the state where the visualized particles do not fly
It is characterized by stopping .

According to this structure, the action force visualizing particles after completion of the image formation is held in the charge of lifting body is applied. Therefore, it is possible to prevent the visualized particles from flying to the control electrode or the counter electrode side. In particular, after the completion of image formation, the continued voltage or the like to maintain the state of developing particles are not fly
Since it is not necessary to supply the power supply, the power consumption can be reduced.

Therefore, the control means carries the carrier.
After stopping the conveyance of the developer particles which are lifting the conveyed on
If so as to release the flying electric field acting between the serial carrier and the counter electrode, it is more effective. That is, the counter electrode is supplied with an electric field for flying the visualized particles, that is, a high voltage, but even if the high voltage is cut off, the counter electrode does not fall to the ground potential due to the time constant. However, developer particles are therefore not an unnecessary flying of developing particles occurs in a state where the holding force that is carried on the carrier is assigned.

Further, the control means, after releasing the flying electric field acting between the carrier and the counter electrode, and finally
By releasing the non-flying potential applied to the control electrode, the non-flying voltage supplied to the control electrode is released in a state where the visualized particles are prevented from flying. It is possible to more effectively prevent the flying of the visualized particles.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. In the following description, an image forming apparatus having a configuration corresponding to negatively charged toner will be described. However, when positively charged toner is used, if the polarity of the voltage to be supplied is set accordingly Good.

FIG. 1 is a schematic sectional view showing the overall construction of the image forming apparatus according to the present invention. In the figure, the image forming apparatus of the present invention includes an image forming unit 1 including a toner supply unit 2 and a printing unit 3. The image forming unit 1 is a recording medium that visualizes on a recording sheet by using toner as a visualized particle according to an image signal. In other words, this image forming apparatus forms the image directly on the recording paper 5 by selectively flying the toner and causing the toner to adhere to the recording paper 5 and controlling the flight of the toner based on the image forming signal. It is a thing.

A paper feeding device 10 is provided on the paper input side of the recording paper 5 into the image forming section 1. The paper feeding measure 10 is
A paper cassette 4 for accommodating a recording paper 5 as a recording medium,
It is composed of a pickup roller (paper feed roller) 6 for feeding the recording papers 5 one by one from the paper cassette 4, and a paper feed guide 7 for guiding the fed recording papers 5. Further, the paper feeding device 10 is provided with a detection sensor (not shown) for detecting that the recording paper 5 is fed in the paper feeding path. The pickup roller 6 is rotationally driven by a driving device (not shown).

The toner image formed on the recording paper 5 in the image forming unit 1 is fixed to the recording paper 5 by heating and pressurizing the recording paper 5 from the image forming unit 1. The fixing device 11 is provided. Fixing device 11
Is composed of a heating roller 12, a heater 13, a pressure roller 14, a temperature sensor 15, and a temperature control circuit 16. The heating roller 12 is formed, for example, in a state in which a surface of an aluminum tube having a thickness of 2 mm is coated with a fluororesin or the like having good releasability for toner. The heater 13 is, for example, a halogen lamp and is built in the heating roller 12.

The pressure roller 14 is formed by coating the surface of a tube of aluminum or the like with a member made of silicone resin. The heating roller 12 and the pressure roller 14 provided so as to face each other have, for example, a spring or the like (not shown) at both ends of each shaft so that the recording paper 5 can be sandwiched and pressed.
A load of kg is applied.

The temperature sensor 15 measures the temperature of the surface of the heating roller 12. The temperature control circuit 16 is controlled by a main control unit (described later) and controls ON / OFF of the heater 13 based on the measurement result of the temperature sensor 15,
The temperature of the surface of the heating roller 12 is maintained at 150 ° C., for example.

The fixing device 11 also includes a paper discharge sensor (not shown) for detecting that the recording paper 5 has been discharged. In addition, the heating roller 12, the heater 13, the pressure roller 1
The material such as 4 is not particularly limited. Moreover, the temperature of the surface of the heating roller 12 is not particularly limited. Further, the fixing device 11 may be configured not only to heat-fix the recording paper 5 but also to fix the toner image by pressure-fixing.

Further, although not shown, on the side of the paper output from the fixing device 11, a paper discharge roller for discharging the recording paper 5 processed by the fixing device 11 onto a paper discharge tray, and the discharged recording paper. A paper discharge tray for receiving 5 is provided. The heating roller 12, the pressure roller 14, and the paper discharge roller described above are rotationally driven by a driving device (not shown) to discharge the recording paper 5.

Toner supply section 2 constituting the image forming section 1
Is a toner storage tank 20 in which toner 21 as visualized particles is stored, a toner carrier 22 as a cylindrical carrier (sleeve) that carries the toner 21 by magnetic force,
And a doctor blade 23 provided inside the toner storage tank 20 for charging the toner 21 and regulating the thickness of the toner layer carried on the outer peripheral surface of the toner carrier 22.

The doctor blade 23 is used for the toner carrier 2
On the upstream side in the rotational direction of No. 2, the distance from the outer peripheral surface of the toner carrier 22 is arranged at an interval of, for example, about 60 μm. The toner 21 has, for example, an average particle size of 6 μm.
The magnetic toner of No. 2 is charged by the doctor blade 23 so that the charge amount is −4 μC / g to −5 μC / g. The distance between the doctor blade 23 and the toner carrier 22 is not particularly limited, and is set appropriately according to the toner conveyance amount. Further, the average particle diameter, the charge amount, etc. of the toner 21 are not particularly limited and may be set as necessary. Toner carrier 22
Is driven by a driving device (not shown), and arrow A in the figure
Direction, for example, the velocity at the surface is, for example, 30 mm / se
It is rotationally driven at about c.

The toner carrier 22 is grounded, and magnets are arranged in a fixed state (not shown) in a position facing the doctor blade 23 inside the toner carrier 22 and a position facing the control electrode 26 (described later). ing. As a result, the toner carrier 22 can carry the toner 21 on the outer peripheral surface thereof, and is further magnetically attracted (carried) by rotating the toner carrier 22 which is a sleeve. Conveying toner. Further, the toner 21 carried on the outer peripheral surface of the toner carrier 22 forms so-called spikes at a position corresponding to the above position on the outer peripheral surface. The rotation speed of the toner carrier 22 is not particularly limited, and the speed may be determined based on the amount of toner conveyed and the like. Further, the toner carrier 22 may be configured to carry the toner 21 by an electric force, or an electric force and a magnetic force, instead of carrying the toner 21 by a magnetic force.

The printing unit 3 of the image forming unit 1 has, for example, a thickness of 1
Toner carrier 2 formed of an aluminum plate of mm
The counter electrode 25 facing the outer peripheral surface of
High-voltage power supply 30 for supplying a high voltage to the toner carrier 2
2 and a control electrode 26 provided between the control electrode 26 and the static elimination brush 32.
And a static elimination power source 17 for applying a static elimination potential to the static elimination brush 32,
A charging roller 33 that charges the recording paper 5, a charging power source 18 that applies a charging potential to the charging roller 33, a dielectric belt 24, support rollers 24a and 24b that support and run the dielectric belt 24, and a cleaner blade. Equipped with 19.

The counter electrode 25 is the toner carrier 22.
Is provided so that the distance from the outer peripheral surface thereof is, for example, 1 mm.

The dielectric belt 24, which runs so as to be in close contact with the counter electrode 25 and is used to convey the recording paper 5, is made of polyvinylidene fluoride (PVDF) as a base material and has a volume resistivity of 10%. It is an endless belt with a thickness of about ¹⁴ Ω · cm and a thickness of about 75 μm. The dielectric belt 24 is stretched between the support rollers 24a and 24b, and is driven by a driving device (not shown), for example, the support roller 2
It is driven via 4b, and is rotated in the direction of the arrow in the figure, for example, at a speed of 30 mm / sec on the surface thereof.

A high voltage of, for example, 2.3 kV is applied to the counter electrode 25 by a high voltage power supply (control means) 30. That is, between the counter electrode 25 and the toner carrier 22, the toner 21 carried on the toner carrier 22 is transferred between the counter electrode 2 and the counter electrode 2 by the high voltage applied from the high-voltage power supply unit 30.
An electric field necessary to fly in five directions is applied.

The charging roller 33 is made of, for example, foamed rubber having urethane as a base material, and the altitude is particularly JIS-A3.
It has characteristics of 0 ° and a resistance value of 10 ⁸ Ω · cm. A high voltage of 1.2 kV, for example, is supplied to the charging roller 33 via a power source 82, and the recording paper 5 is negatively charged and electrostatically attracted to the dielectric belt 24, and the dielectric The belt 24 is configured to be conveyed according to the traveling speed.

The static elimination brush 32 is the dielectric belt 24.
It is provided so as to be in pressure contact with the dielectric belt 24 at the further downstream side of the position facing the control electrode 26 in the rotation direction of. The static elimination power source 17 applies a static elimination potential of 2.5 kV to the static elimination brush 32 to eliminate unnecessary electric charges existing on the surface of the dielectric belt 24.

When the toner 21 adheres to the surface of the dielectric belt 24 due to an unforeseen situation such as paper jam (paper jam), the cleaning blade 19 removes the toner 21 and the back surface of the paper. Is the toner 2
1 to prevent contamination. The counter electrode 2
The material of 5 is not particularly limited, and a necessary material may be set as appropriate. Also, the distance between the counter electrode 25 and the toner carrier 22 is not particularly limited and may be set appropriately. Further, the rotation speed of the counter electrode 25 and the applied voltage are not particularly limited, and may be set appropriately according to the toner used and the speed.

Although not shown, this image forming apparatus
As a control circuit, a main control unit that controls the entire image forming apparatus, an image processing unit that converts surface image data obtained from an image reading apparatus that reads an image of a document or the like into a format of image data to be printed, are converted. Further, an image memory for storing the image data and an image formation control unit for converting the image data obtained from the image processing unit into the image data to be given to the control electrode 26 are provided.

Therefore, the control electrode 26 is the counter electrode 2
5 is parallel to the tangential direction of the surface and is two-dimensionally spread so as to face the counter electrode 25, and the toner flow from the toner carrier 22 to the counter electrode 25 can pass therethrough. The electric potential applied to the control electrode 26 changes the electric field applied between the toner carrier 22 and the counter electrode 25, so that the toner carrier 22 moves to the counter electrode 25.
It is possible to selectively control the flight of the toner 21 to the toner.

The control electrode 26 is arranged so that the distance from the outer peripheral surface of the toner carrier 22 is 100 μm, for example, and is fixed by a support member (not shown). As shown in detail in FIG. 2, the control electrode 26 includes an insulating substrate 26a, a high-voltage driver (not shown), and ring-shaped conductors 27, ...・ It consists of The substrate 26a is made of, for example, a polyimide resin and has a thickness of 25 μm. Further, a gate 29, which will be described later, is provided on the substrate 26a.
..A hole to be used is formed. Ring electrode 27
Are formed of, for example, a copper foil, are provided on the surface of the substrate 26a on the toner carrier 22 side, that is, around the holes 29, and are arranged according to a predetermined arrangement. Each ring-shaped electrode 27 has, for example, a diameter of 220 μm and a thickness of 30 μm.
It is formed in m. Further, the openings 29 ... Of the ring-shaped electrodes 27 are formed to have a diameter of 200 μm, for example, and serve as passage portions for the toner 21 flying from the toner carrier 22 to the counter electrode 25. Hereinafter, this passage will be referred to as a gate 29. The distance between the control electrode 26 and the toner carrier 22 is not particularly limited.

Further, the size of the gates 29, the material and thickness of the substrate 26a and the ring-shaped electrodes 27, etc. are not particularly limited. Gate 29 above
..... That is, the ring-shaped electrodes 27 ...
Each ring-shaped electrode 27 is individually formed and electrically connected to a control power supply unit 31 (described later) via a power supply line 28 and a high-voltage driver (not shown). The above number is the resolution of 300DP in the width of A4 size paper.
It corresponds to I (dot per inch) and forms an image for one line.

The number of the ring-shaped electrodes 27 ... Is not particularly limited. Further, the surface of the ring-shaped electrode 27 ...
It is covered with an insulating layer (not shown) of the order of μm, so that the ring electrodes 27 are insulated from each other, the feed lines 28 are insulated from each other, and are connected to each other. The insulation between the ring-shaped electrodes 27 ... And the power supply lines 28. The material and thickness of the insulator layer are not particularly limited.

The ring-shaped electrode 27 of the control electrode 26 ...
A pulse corresponding to an image signal, that is, a voltage is applied by a control power supply unit (control means) 31 to the. In other words, the control power supply unit 31 applies a voltage of, for example, 150 V to the ring-shaped electrodes 27, ... When passing the toner 21 carried on the toner carrier 22 in the direction of the counter electrode 25, the control power supply unit 31 does not pass it. In this case, for example, a voltage of -200V is applied. In this way, when the voltage (potential) applied to the control electrode 26 is controlled according to the image signal and the recording paper 5 is fed to the surface of the counter electrode 25 facing the toner carrier 22, the surface of the recording paper 5 will be described. A toner image corresponding to the image signal is formed on the. The control power supply section 31 is controlled by a control electrode control signal sent from an image forming control unit (not shown).

Next, the image forming operation of the image forming apparatus will be described with reference to the control flow shown in FIG.

First, for example, when a document to be copied is placed on the image reading section and a copy start button (not shown) is operated, the main control section receiving this input starts the image forming operation. That is, a document image is read by the image reading unit (step n1), the image data is processed by the image processing unit (step n2), and stored in the image memory (step n3). The image data stored in the image memory is transferred to the image forming control unit (step n4), and the image forming control unit starts converting the input image data into a control electrode control signal to be given to the control electrode 26 (step S4). n5). Further, when the image forming control unit obtains a control signal to be supplied to the control electrodes of a predetermined amount, the toner carrier 22 is rotationally driven (step n7).
Then, the same potential as that of the counter electrode 25 is applied to the support roller 24a by the high voltage power source 30 (step n9). The charging power source 18 applies a charging potential of 1.2 kV to the charging roller 33, and the discharging brush 32 applies a discharging potential by the discharging power source 17 (step n9).

If the control electrode signal is not the predetermined amount, the flow is interrupted at step n6 and an error display (step n20) is performed. Further, if it is confirmed that the signal is the desired control electrode signal, when the control signal to be supplied to the desired control electrode is obtained as described above, the counter electrode 25, the charging roller 33, and the charge removal brush 3 are described as described above.
While a predetermined high voltage is applied to No. 2, a potential at which toner does not fly -200 V is applied to all the ring electrodes 27 of the control electrode 26 so that the toner 21 of the toner carrier 22 does not fly. Keep it.

After that, a driving device (not shown) is operated, and the recording paper 5 in the paper cassette 4 is sent toward the image forming section 1 by the pickup roller 6 which is driven to rotate by this driving device (step n10). At this time, it is confirmed in step n11 whether or not the paper is in a normal paper feeding state. That is, when the recording paper 5 to be fed is detected by the paper feed sensor in the feeding path, it is determined that the operation is normal, and step n12
Proceed to.

Here, the recording paper 5 delivered by the pickup roller 6 has the charging roller 33 and the supporting roller 2
It is conveyed between 4a. The recording paper 5 is supplied with an electric charge due to the potential difference between the charging roller 33 and the support roller 24a, and is electrostatically attracted to the recording paper 5 as the dielectric belt 24 runs. The toner is conveyed to the surface opposite to the toner carrier 22. The predetermined amount of the control electrode control signal varies depending on the image forming apparatus and the like.

Then, the image forming control unit sends the control electrode control signal to the control power source 31 in step n12.
Supply to. The supply of the control power supply control signal is performed at a timing synchronized with the timing at which the charging roller 33 supplies the recording paper 5 to the printing unit 3. Control power supply unit 31
Controls the voltage applied to each ring-shaped electrode 27 of the control electrode 26 based on the control electrode control signal. That is, a voltage of 150 V or −200 V is appropriately applied to the predetermined ring-shaped electrode 27 from the control power supply unit 31 to control the electric field near the control electrode 26. That is, at the gate 29 of the control electrode 26, prevention of flying of the toner 21 from the toner carrier 22 to the counter electrode 25 according to image data,
The cancellation is appropriately performed. As a result, the traveling of the dielectric belt 24 causes 30 mm / sec toward the paper output side.
A toner image corresponding to the image signal is directly formed on the recording paper 5 moving at the speed of. In the present invention,
When it is confirmed in step n13 that the image forming operation has ended, control for ending (not shown) is executed. This control will be described in detail later.

The recording paper 5 on which the toner image is formed is separated from the dielectric belt 24 by the curvature of the supporting member 24b and conveyed to the fixing device 11, and then the toner image is formed on the recording paper 5 by the fixing device 11. Is fixed in. The recording paper 5 on which the toner image is fixed is discharged onto the paper discharge tray by the paper discharge roller, and the normal discharge is detected by the paper discharge sensor.

Based on this detection operation, the main control unit determines whether the image recording operation is normally completed. When the image recording operation is finished, the toner 21 on the toner carrier 22 is
Control is performed to prevent the particles from flying and adhering to the dielectric belt 24 on the control electrode 26 and the counter electrode 25.

By the above image forming operation, a good image is formed on the recording paper 5. The image forming apparatus includes a recording paper 5
Since the image is directly formed on the image forming apparatus, a photoreceptor such as a photoconductor or a dielectric drum used in a conventional image forming apparatus is unnecessary.

Therefore, since the transfer operation for transferring the image from the image developer to the recording paper is omitted, the image is not deteriorated.
Therefore, the reliability of the device is improved. Further, since the structure of the apparatus is simplified and the number of parts is reduced, it is possible to reduce the size and cost.

After the image formation in the present invention, the control electrode 26 and the counter electrode 2 including the toner carrier 22 are described below.
The voltage supply control to the No. 5 will be described. That is, the control is for preventing the toner 21 carried on the toner carrier 22 from adhering to the control electrode 26 or the like at the end of image formation.

FIG. 4 is a timing chart at the end of image formation according to the present invention. The control of the image forming apparatus according to the present invention will be described in detail with reference to FIG.

In the present embodiment, when the image forming operation is completed based on the image data, the toner carrier 22 is first
Is stopped first. In FIG. 4, the motor drive signal is a drive signal of a drive motor for rotationally driving the toner carrier 22, and this drive signal is first turned off.
It becomes a state. Before stopping the drive of this motor, as shown in FIG.
Based on the image data as shown in the time chart of
The potential supplied to the control electrode 26 is controlled. For example, when there is image data, that is, when dots are formed, the image data is output (ON), and the toner flying potential (150 V) is selectively supplied to the ring electrode 27 of the control electrode 26 based on the data. To be done.

When the image forming operation is completed, the completed state is confirmed, and the rotation operation of the toner carrier 22 is stopped at the timing t2 after the timing t1 in the time chart of FIG. After that, at timing t3, the potential supplied to the charging roller 33 is cut off and the ground potential (“0”) is applied. As a result, negative charges are supplied to the surface of the dielectric belt 24, and the surface potential of the dielectric belt 24 becomes close to 0V. At this time, the static elimination brush 3 that eliminates static electricity from the dielectric belt 24
The voltage supplied to 2 is also connected to ground potential. This is also for uniformly discharging the dielectric belt 24.

In this state, the dielectric belt 24 is continuously rotated, and if it is rotated by at least one revolution in order to uniformly eliminate the entire periphery, the voltage supplied to the counter electrode 25 at the timing t4. Is cut off, that is, connected to the ground potential state. In this state, the dielectric belt 24 continues to rotate, and when it makes another round, the surface potential with the dielectric belt 24 becomes substantially "0" over the entire circumference.

After the supply of the high voltage to the counter electrode 25 is cut off to the ground potential, the dielectric belt 24 makes at least one revolution and the charged electric charges in the entire region are removed, that is, the potential becomes approximately "0". For example, the driving of the dielectric belt 24 is stopped and controlled at the timing t5. In this stop, the driving of the support roller 24b supporting the dielectric belt 24 is stopped. The driving of the support roller 24b is stopped by cutting off the transmission of the rotational force from the drive motor in the transport system that transports the recording paper 5 and transports it through the dielectric belt 24 and the fixing unit.

Then, after the running state of the dielectric belt 24 is stopped, finally at timing t6, the potential supplied to the control electrode 26 is released. Naturally, at the time when the image forming operation is completed (timing t1), the control electrode 26 has a potential (in this embodiment, a potential for preventing the toner 21 of the toner carrier 22 from flying toward the counter electrode 25). -200 V) is supplied and is continuously maintained. The supply potential to the control electrode 26 is finally stopped and the ground potential is applied to the control electrode 26, particularly to the ring electrode 27.

Power supply circuits 17, 1 for supplying a predetermined voltage to the charging roller 33, the counter electrode 25 and the control electrode 26.
8, 30 and the power supply control circuit 31 are configured to output the ground potential by cutting off the supply voltage. That is, when the supply of voltage is cut off, the output terminal is grounded.

As described above, in the present invention, after the driving of the toner carrier 22 is stopped, the toner flying electric field between the toner carrier 22 and the counter electrode 25 is released,
After that, the electric field that controls the toner flying state acting between the toner carrier 22 and the control electrode 26 is controlled to be removed.

On the other hand, unlike the conventional case, even if the high voltage supplied to each electrode 25 and 26 is simultaneously turned off by a single trigger, the output of the high voltage power source does not become 0V at the same time. It takes time to decrease the output potential as the power becomes higher. In this case, for example, even when the potential of the control electrode 26 becomes 0V, the potential of the counter electrode 25 becomes 0V.
However, the electric potential in the direction of attracting the toner 21 is still maintained. Although this time is very short, the toner 21 starts to fly toward the counter electrode 25 and reaches the counter electrode 25 or the control electrode 26 during this time (hereinafter referred to as erroneous flying toner).

For this reason, the above-mentioned erroneous flying toner adheres to the surface of the counter electrode 25 and the counter electrode 25, especially the counter electrode 25
The surface of the dielectric belt 24 that runs in a state in which it is in close contact with the top is soiled with toner. When the image forming operation is restarted in this state and the recording paper 5 is conveyed, the back surface of the recording paper 5 is soiled with the above-mentioned false flying toner. Alternatively, the apparent potential of the counter electrode 25 viewed from the toner 21 existing on the surface of the toner carrier 22 changes due to the potential of the electric charge of the falsely flying toner.
1 does not fly easily, a sufficient electric field necessary for toner flight cannot be obtained, and the desired toner 21 does not fly in the area where the false flying toner adheres. Sufficient toner 21 cannot fly to the surface of the corresponding recording paper 55, resulting in a decrease in image density and defective printing.
In the worst case, the toner 21 cannot fly and image loss occurs.

When the high voltage supply is cut off, the high voltage is not switched by a relay circuit or the like, but the high voltage power source itself is normally turned off. In this case, the time constant is further lengthened and the above problems are further reduced. It becomes remarkable.

Further, the toner 21 is the gate 2 of the control electrode 26.
When it adheres to the gate 9, it adheres to the inside of the opening of the gate 29 and narrows the diameter of the opening of the gate 29. When the image forming operation is started in this state, the flying toner 21 cannot take a predetermined flying path due to the toner attached inside the gate 29. In such a case, the flight route of the toner 21 cannot be predicted, and the flight arrival point cannot be controlled. Therefore, the flight toner 21 does not always reach the predetermined dot area of the recording paper 5, and the flight toner 21 does not reach the predetermined dot area. To reach. When it reaches the area other than the dot area, the dots on the recording paper 5 are scattered or fog, and the dots on the recording paper 5 are bleeding and have no contrast, and the dots are blurred, causing image deterioration. Therefore, it goes without saying that a desired clear image cannot be formed, but the formed dot density or dot diameter does not reach a desired size, and it becomes difficult to reproduce a halftone or color image.

Further, the charge of the toner attached inside the gate 29 changes the apparent potential of the control electrode 26 as seen from the toner on the toner carrier 22, and specifically, the potential of the control electrode 26 is such that the toner does not fly. Since the electric potential changes so as to be close to the electric potential, it becomes more difficult to fly the toner. Therefore, even if a potential such that toner flies is applied to the control electrode 26, the toner 21 on the toner carrier 22 does not feel a flying electric field and is not flied. In this state, the image forming operation is not performed, resulting in defective printing. Alternatively, image loss occurs partially.

Even if the toner 21 flies in this state, the potential of the equipotential surface near the gate 29 is changed by the electric potential of the toner 21 attached inside the control electrode 26 or the gate 29 as described above. The shape is no longer the predetermined shape, and the shape easily changes due to the adhesion state of the toner 21 and the like, making prediction and control impossible. Even in such a state, the flight path of the toner 21 cannot be predicted, and the flight arrival point cannot be controlled. Therefore, the flight toner 21 does not always fly to a fixed dot area of the recording paper 5, and reaches the area other than the dot area. To do. When it reaches the area other than the dot area, the dots on the recording paper 5 are scattered or fogged as described above, and the dots on the recording paper 5 are blurred with no contrast and cause image deterioration. Therefore, it goes without saying that a desired clear image cannot be formed, but it is difficult to obtain the desired density of the formed dot density or dot diameter or the desired size, and it becomes difficult to reproduce a halftone or a color image.

If the toner adhesion is further aggravated, finally, the gate 29 causes a blinding due to the false flying toner, which causes the worst case in which the image formation itself becomes physically impossible.

Further, if the image forming apparatus is left with the image forming operation completed, the toner 21 is aggregated in a state of being attached to the control electrode 26. In this case, the adhered toner cannot be removed due to the electrostatic force, and it is necessary to forcibly remove it. For example, the control electrode 26
And remove it using cleaning means such as an air brush or a cleaning brush. In particular, since the control electrode 26 is very thin and easily damaged, when removing it by the above-mentioned cleaning means,
This will lead to new problems such as being damaged, broken, deformed, or displaced in the mounting position after cleaning.

On the other hand, according to the present invention, as described with reference to the time chart of FIG. 4, after the image forming operation is completed, the toner carrying member 22 is first driven, in particular, stopped from rotating to carry the carried toner. The speed including vibration of 21 is set to zero. The toner 21 is carried to the image forming area of the printing unit 3 while being carried by the toner carrier 22. As the toner 21 is conveyed, the holding force of the toner 21 on the toner carrier 22 is weakened.

Therefore, the rotation of the toner carrier 21 is stopped, or the transport speed of the toner 21, that is, the moving speed is set to zero at the timing t2 after the timing t1 at which the end of image formation is detected. In this way, the carrying state of the toner 21 is stopped, and the acting force of the toner 21 being attracted to the carrier 22 is increased. That is, a force in the direction of the toner carrier 22 is applied to the toner 21. Here, the rotation operation of the toner carrier 21 is stopped in order to make the transport state of the toner 21 zero, but in addition to this, the doctor blade 2
Although the amount of adhesion to the toner carrier 22 is regulated in 3, the amount of adhesion can be made zero by this. In addition to the doctor blade 23, a shutter or the like is used to control the toner supplied to the toner carrier 22, and the toner supply to the toner carrier is blocked by the shutter in order to zero the toner 21 conveyance. You may do it.

As described above, after the driving of the toner carrier 22 is stopped, the toner flying electric field applied between the toner carrier 22 and the counter electrode 25 is released at the timing t4. At this time, on the control electrode 26 side, as shown in FIG. 4, after the image formation is completed, the electric potential state in which the electric field that does not fly the toner 21 acts is maintained. for that reason,
The supply of the high voltage to the counter electrode 25 is stopped, the ground potential is applied, and the potential gradually changes to the ground potential (“0”) according to the time constant.
However, the flying of the toner 21 on the toner carrier 22 is prevented.

After the counter electrode 25 is switched to the ground potential, if the counter electrode 25 stabilizes in the ground potential state, the potential for preventing the toner from flying to the control electrode 26 is finally timed. Release at t6.
As a result, the toner 21 does not fly from the toner carrier 22. Therefore, all the above-mentioned conventional problems can be avoided. In addition, the counter electrode 25 and the control electrode 26
Since the supply of the voltage is canceled, the power consumption after the image formation is completed can be reduced.

In FIG. 4, the motor drive pulse and the potential of the control electrode 26, or the time difference between the high voltage control of the counter electrode 25 and the charging roller 33 varies depending on the characteristics of the apparatus, but the toner 21 on the toner carrier 22 is carried by the toner carrier. Body 2
2 is not particularly limited as long as it is kept above 2. That is, before releasing the voltage supply to the control electrode 26,
It is optimum to cancel the toner flying electric field to the counter electrode 25.

According to the above-described embodiment, a monochrome image forming apparatus has been described as an example, but a sufficient effect can be obtained even in the case of a color image forming apparatus.
For example, as shown in FIG. 5, a plurality of toner supply units 2a, 2b, 2C and 2d and printing units 3a, 3b, 3C and 3 are provided.
A color image forming apparatus using color toner, yellow, magenta, cyan, and black is provided in each of the toner supply sections 2a, 2b, 2C, and 2d by arranging the image forming sections 1a, 1b, 1C, and 1d including d. It is configured.

In FIG. 4, the image forming portions 1a and 1a corresponding to yellow, magenta, cyan, and black, respectively.
b, 1c and 1d are provided, and the respective control electrodes 26a, 26b, 2 arranged corresponding to these image forming portions are provided.
A color image is formed by controlling the potentials supplied to 6c and 26d based on the color image data. The other precautionary elements have the same configuration as in FIG. 1, and in particular, the counter electrode 25 is commonly used for each image forming section.

According to this color image forming apparatus, when the above-mentioned trouble occurs, for example, the toner stain on the dielectric belt 24 due to the color toner is simply quadrupled, and the above-mentioned trouble appears more remarkably. However, by performing the control according to the present invention, the problem can be solved, and thus the effect of the present invention is promoted.

In the above description of the embodiment, the control electrode 26 is used.
Although the control electrode of the single drive as shown in FIG. 2 is used as the above, the shape of the control electrode can be similarly implemented in the configuration using the matrix drive as shown in FIG. The matrix drive has the effect of reducing costs because the number of drives required can be greatly reduced.

As shown in FIG. 6, the control electrode 26 is connected to the substrate 2
Strip-shaped electrode groups 27a and 27b are formed on the front and back surfaces of 6a so as to be orthogonal to each other. Gates 29 for passing the toner flow are formed at the respective positions where the strip electrode groups 27a and 27b on the front and back surfaces intersect.

Then, for example, a toner flying potential according to an image signal is applied to the band-shaped electrode group 27a on the surface. Further, a toner flying potential according to a scanning signal that is periodically switched is applied to the strip-shaped electrode group 27b on the back surface. As a result, in the state where the toner flying potential is simultaneously applied to the strip-shaped electrode groups 27a and 27b on the front and back surfaces where the gate 29 intersects,
The toner 21 of the toner carrier 22 is ejected and the gate 29
After passing through, the particles will be flown to the counter electrode 25.

Also in the control electrode 26 having such a configuration, even if the electrode group facing the counter electrode 25 is controlled as described above, the same effect as in the above case can be obtained.
That is, after the image formation is completed, the high voltage supplied to the counter electrode 25 is released, and then the non-flyable potential state supplied to the strip electrode groups 27a and 27b is switched to the ground potential.

In this embodiment, the case where the visualized particles are toner has been described as an example, but the visualized particles may be ink or the like.

Further, the structure of the toner supply unit 2 may be a structure to which the ion flow method is applied. That is, the image forming unit 1 may be configured to include an ion source such as a corona charger. Even in this case, the same effects as the above can be obtained.

The image forming apparatus according to the present invention is, for example,
The printing section of digital copiers and facsimile machines,
It can be suitably applied to digital printers, plotters and the like.

[0092]

As described above, the image forming apparatus can prevent the visualized particles from flying after the image forming operation is completed. In particular, if the visualized particles are, for example, a toner, the flying of the toner stains the control electrode and the counter electrode, and various problems due to this contamination do not occur.
Stable image formation can be performed. In this case, even if the power supply to the counter electrode and the control electrode is stopped at the end of image formation,
It is possible to prevent unnecessary toner flying and at the same time reduce power consumption.

In particular, by stopping the carrier carrying the toner after the image formation is completed, the high voltage supply to the counter electrode is released, and the non-flying potential to the control electrode is released later. It is possible to reliably prevent the toner from flying.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an overall configuration of an image forming apparatus according to the present invention.

FIG. 2 is a plan view showing a detailed configuration of a part of a control electrode included in the image forming apparatus of the present invention.

FIG. 3 is a flowchart showing a flow of image forming control in the image forming apparatus according to the present invention.

FIG. 4 is a timing chart showing the timing applied to the control electrode of the present invention.

FIG. 5 is a sectional view showing a configuration of a main part for forming a color image in the image forming apparatus according to the present invention.

FIG. 6 shows another specific example of the control electrode of the present invention,
It is a plan view of a control electrode having a matrix configuration.

FIG. 7 is a sectional view for explaining an image forming principle of a conventional image forming apparatus.

[Explanation of symbols]

1 Image forming section 2 Toner supply unit 3 Printing department 5 Recording paper (recording medium) 17 Power supply (for static elimination of dielectric belt) 18 power supply (for charging dielectric belt) 21 Toner (visualized particles) 22 Toner carrier 25 Counter electrode 26 Control electrodes 27 ring electrode 29 gates 30 High-voltage power supply (control means) 31 Control power supply unit (control means) 32 Static elimination brush 33 charging roller

Claims (3)

(57) [Claims] A bearing member as claimed in claim 1] provides the desired properties for the developing particles to carrying該顕image particles, and a counter electrode disposed opposite to said supported member, between these carriers and the counter electrode A control electrode having a plurality of gates that are arranged in the passage of the visualized particles and a potential that causes a predetermined potential difference between the carrier and the counter electrode, and a potential to be applied to the control electrode. in the image forming apparatus and a control means for forming an image by controlling the passage of the gate of the developing particles by varying the, at the end of the image forming operation, said control means, said carrier
Control of the state of developing particles are not fly carried on
Before releasing, visible conveyed is supported on the carrier
An image forming apparatus, characterized in that the conveyance of chemical particles is stopped . 2. The control means is carried on the carrier.
After stopping the conveyance of the developer particles to be conveyed, the image forming apparatus according to claim 1, wherein the releasing the flying electric field acting between the carrier and the counter electrode. Wherein said control means, after releasing the flying electric field acting between the carrier and the counter electrode, wherein, characterized in that to release the non-flying potential being applied to said control electrode Item 2. The image forming apparatus according to item 2.