JP3402893B2 - 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.

An 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,
The counter electrode 75 is made of, for example, an aluminum tube having a diameter of 50 mm, and the control electrode 76 is provided between the counter electrode 75 and the toner carrier 72. The counter electrode 75 is arranged with a distance of about 1 mm from the outer peripheral surface of the toner carrier 72. A high voltage of, for example, 2 kV is applied to the counter electrode 75 by the DC power supply unit 80, and the counter electrode 75 is rotationally driven in the direction of arrow F at a surface speed of 30 mm / sec in the figure. That is,
Between the counter electrode 75 and the toner carrier 72, the toner 71 carried on the toner carrier 72 is placed between the counter electrode 75 and the counter electrode 75.
An electric field necessary to fly in the direction is applied.

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

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 ... With a diameter of about 150 .mu.m serving as a passage portion of the toner 71 are formed on the substrate 76a, and the ring 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 according 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 the potential not to pass the toner 71 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.
The degree is set. This ensures that the toner adheres to the recording paper 55 on the counter electrode 75.

[0010]

In the conventional image forming apparatus described above, the high voltage applied to the counter electrode 75 is applied at the same time when the potential is applied to the other electrode and the rotation of the toner carrier 72 is started. In this case, after the main body of the image forming apparatus is stopped for a long time, or immediately after the rotation of the toner carrier 72 is started,
The surface of the toner carrier 72 does not have a desired charge, and the layer thickness of the carried toner is not stable.
There are a lot of unstable toners 71.

In such a state, when a high voltage is applied to the counter electrode 75 in order to execute the image forming operation, even if a potential that does not allow the toner 71 to pass through is applied to the control electrode 76, the toner carrying member 72 causes the counter electrode to move. There is toner 71 which starts moving to 75 and tries to pass through the gate 79. For this reason, the surface of the counter electrode 75 becomes dirty with the toner 71, or the recording paper 5 conveyed by the flying toner.
The back surface of No. 5 becomes dirty with toner.

Further, among the unstable toners 71, a potential at which the toner 71 does not fly to the control electrode 76 (in the conventional case,
Even if 200 V) is applied, the toner 71 may fly to the control electrode 76 due to the potential difference from the counter electrode 75.
In this way, the toner 71 adheres to the control electrode 76, and the charge of the toner 71 causes the ring-shaped electrode 7 to move.
The apparent potential of 7 ... Changes, and it becomes difficult to control the passage of normal toner. Alternatively, the gate 79 for passing the toner may be clogged with the toner adhering to the control electrode 76, so that printing cannot be performed in the worst case.

Further, among the unstable toners 71, there is a considerable amount of reversely charged toner 71 whose charge polarity is opposite to the desired polarity. If such a reversely charged toner 71 is present, the control electrode 76 is applied even if a potential (-200 V in the above-mentioned related art) that does not cause the toner 71 to fly is applied to the control electrode 76.
The reversely charged toner 71 adheres to the. Reverse charging toner 7
1 adheres to the control electrode 76, the toner 7
The apparent electric potential of the ring electrode 77 is changed by the electric charge of 1 and it becomes difficult to control the toner normally. Alternatively, a problem such as clogging of the gate 79 may occur, and in the worst case, printing may be impossible.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to solve the problems that occur at the start of image formation.

Another object of the present invention is to control so that the toner does not fly and adhere to the control electrode and the counter electrode side at the initial stage of the start of image formation.

[0016]

Image forming apparatus for achieving the above object of the present invention In order to achieve the above object, according a <br/> carrier for carrying the developing particles, which is disposed opposite to said supported member A counter electrode,
A control electrode having a plurality of gates, which are arranged between the carrier and the counter electrode and serve as a passage for the visualized particles, and a potential for generating a predetermined potential difference are applied between the carrier and the counter electrode. In addition, an image forming device including a control unit that controls the passage of the visualized particles through the gate by changing the potential applied to the control electrode to form an image on a recording medium conveyed on the counter electrode. In the apparatus, the above-mentioned control means is provided as a step before starting the image forming operation.
The charge amount of the visualized particles carried on the carrier is stabilized.
In, without imparting a voltage to the control electrode, the visible
After the charge amount of the visualized particles becomes stable, the visualized particles carry the above
It is characterized by applying a potential that does not fly from the body .

Control means in the image forming apparatus
As a step before starting the image forming operation.
The visualized particles carried by the carrier were made to fly to the counter electrode.
To the above-mentioned control electrode without applying a potential for
After applying an electric potential that does not cause the child to fly, it is carried on the carrier.
A high voltage is applied to fly the visualized particles.

Further, control means in the image forming apparatus
Applies the high voltage to the counter electrode,
After that, apply a potential according to the image signal to the control electrode.
The recording medium conveyed on the counter electrode by controlling
To start the image forming operation.

According to the image forming apparatus configured as described above, the toner, which is the image-forming particle, for example, first rotates the carrier for supporting the toner before the image is formed on the recording paper which is the recording medium. And stabilize it. For example, the charge amount is made stable. In this state, by applying a potential at which the toner does not fly to the control electrode, the toner in a stable state is prevented from flying from the carrier to the control electrode side. Moreover, even if a predetermined high voltage is applied to the counter electrode after applying a potential at which the toner does not fly to the control electrode and a strong electric field for causing the toner to fly is applied between the counter electrode and the counter electrode of the carrier, As described above, since the electric field in the state where the toner does not fly is acting on the control electrode, the toner does not fly from the carrier to the counter electrode side via the control electrode.

Therefore, at the initial stage after the start of image formation, the toner does not fly to the control electrode or the counter electrode and is applied. Therefore, if a control potential according to an image signal is applied to the control electrode for image formation, An image is formed on the recording paper in a normal state. That is, in order to control the flight of the toner on the carrier, the control electrode is formed with a gate which is a hole through which the toner passes, and an electrode for supplying a voltage is formed around this gate. Since the toner does not fly and adhere to the electrode, the gate does not become clogged with the toner, the supplied potential does not change, and the toner surely adheres to the gate when an image is formed on the recording paper. It is possible to fly to the counter electrode side via the. Therefore, the image quality is not disturbed on the recording paper,
A normal image can be formed.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a schematic sectional view showing the overall construction of an 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 visualizes images on a recording sheet, which is a recording medium, by using toner as developing particles according to an image signal.
That is, this image forming apparatus selectively ejects toner onto the recording paper 5 and controls the ejection of the toner based on the image forming signal to thereby cause the recording paper 5 to fly.
A visible image is directly formed on the toner with the toner.

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 device 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, in the paper feeding device 10, a detection sensor (not shown) that detects that the recording paper 5 has been fed is provided 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, 2 kg by a spring or the like (not shown) at both ends of each shaft so that the recording paper 5 can be pressed and pressed. Is being 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 port la 12 is maintained at, for example, 150 ° C.

Further, the fixing device 11 is provided with a paper discharge sensor (not shown) which detects 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 what is called a bristling of toner at a position on the outer peripheral surface corresponding to the magnetic pole position of the fixed magnet. 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 is
Instead of carrying the toner 21 by magnetic force, electric force,
Alternatively, it may be supported by electric force and magnetic force.

The printing unit 3 of the image forming unit 1 has, for example, a thickness of 1
Toner carrier 2 formed of a 2 mm aluminum plate
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 brush 14 that charges the recording paper 5, a charging power source 18 that applies a charging potential to the charging brush 14, a dielectric belt 24, support rollers 16a and 16b 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 is run 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 its volume resistivity is 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 16a and 16b, and is driven by a driving device (not shown), for example, the support roller 1
It is driven via 6b and is rotated in the direction of the arrow in the figure at a speed of 30 mm / sec on the surface thereof, for example.

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

The static elimination brush 28 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 2.3 kV to the static elimination brush 28 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 forming control unit for converting the image data obtained from the image processing section 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.

The size of the gates 29, the material and thickness of the substrate 26a and the ring 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 the image signal, that is, a voltage is applied to the signal by the control power supply unit (control means) 31. That is, the control power supply unit 31 applies a voltage of, for example, 150 V to the ring-shaped electrodes 27 ... When the toner 21 carried on the toner carrier 22 is passed in the direction of the counter electrode 25.
When it is not passed, for example, a voltage of 1200 V 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 onto the counter electrode 25 on the surface of the counter electrode 25 facing the toner carrier 22, A toner image corresponding to the image signal is formed on the surface of the recording paper 5. 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 FIG.

First, for example, when a document to be copied is placed on the image reading unit and a copy start button (not shown) is operated, the main control unit receiving this input starts the image forming operation. That is, the original 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 converts the input image data into a control electrode control signal to be given to the control electrode 26. Start (step 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).
To be done. The rotation of the toner carrier (sleeve) 22 stabilizes the amount of charge of the carried toner. After that, the same potential as that of the counter electrode 25 is applied to the support roller 16a by the high-voltage power supply 30 (step n9). The charging brush 14 has a charging power source 18 as a charging potential of 1.
At 2 kV, the static elimination power source 17 applies a static elimination potential to the static elimination brush 32 (step n9).

If it is not the desired control electrode signal, this flow is interrupted in step n6 and an error display (step n20) is performed. Further, if it is confirmed that the signal is a desired control electrode signal, when the control signal to be supplied to the control electrode of a predetermined amount is obtained as described above, the counter electrode 25, the charging brush 14, and the charge removal brush 3 are described as described above.
Before a predetermined high voltage is applied to 2, in the present invention,
To prevent the toner 21 of the toner carrier 22 from flying,
A potential of -200 V at which the toner does not fly is applied to all the ring-shaped electrodes 27 ... Of the control electrode 26 (step n8).

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

Here, the recording paper 5 sent out by the pickup roller 6 is the charging brush 14 and the support roller 1.
It is conveyed between 6a. The recording paper 5 is supplied with an electric charge due to the potential difference between the charging brush 14 and the support roller 16a, and is electrostatically adsorbed. As the dielectric belt 24 runs, the toner on the dielectric belt 24 in the printing unit 3 of the image forming unit 1 It is conveyed to the side opposite to the 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 control power supply control signal is supplied at a timing synchronized with the timing at which the charging brush 14 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 applied from the control power supply unit 31 to the predetermined ring-shaped electrode 27 according to the image signal, and the electric field near the control electrode 26 is controlled. That is, at the gate 29 of the control electrode 26, the toner 2 from the toner carrier 22 to the counter electrode 25 is transferred in accordance with the image data.
The prevention of the flight of 1 and the cancellation thereof are appropriately performed. As a result, a toner image corresponding to the image signal is formed on the recording paper 5 moving at a speed of 30 mm / sec toward the paper output side due to the traveling of the dielectric belt 24. Regarding the control by the control power supply unit 31 according to the present invention,
The details will be described 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 16b and is conveyed to the fixing device 11, and then the toner image is recorded 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 section determines the normal end of the printing operation. By the above image forming operation, a good image is formed on the recording paper 5. Since the image forming apparatus directly forms an image on the recording paper 5, the image forming body such as the photoconductor and the dielectric drum used in the 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 device is simplified and the number of parts is reduced, the size and cost can be reduced.

Here, the toner carrier 22 and the counter electrode 25
Consider the flying of the toner 21 between the toner carrier 22 and the counter electrode 25, which is caused by the voltage application between and. As described above, the toner carrier 22 is grounded, while the counter electrode 25 is applied with a high voltage of 2 kV.

Between the toner carrier 22 and the counter electrode 25, equipotential surfaces of 0 V to 2 kV are formed at equal intervals. The counter electrode 25 is the toner carrier 2
2 is provided so as to have a distance of 1 mm from the outer peripheral surface, and the control electrode 26 is provided so as to have a distance of 100 μm from the outer peripheral surface of the toner carrier 22, so that the gate 29 of the control electrode 26 is provided. ... Center (gate center)
The potential at the position of is about 200V. still,
The potential at the center of the gates 29 ...
And the counter electrode 25, the position where the control electrode 26 is disposed, the shape of the gates 29 ...

In this state, the control power source 31 causes the ring-shaped electrode 27 of the control electrode 26 to pass the toner 21 carried on the toner carrier 22 toward the counter electrode 25.
..., a voltage of 150 V is applied to each pixel, for example, 1
Apply for 50 μsec. Then, the equipotential surface near the gate 29 of the control electrode 26 becomes as shown in FIG. That is, the equipotential surface in the space area of the gate 29 is curved toward the toner carrier 22 side.

Similarly, when a potential of -200 V that prevents the toner 21 from passing through the gate 29 is applied to the ring electrode 27, the same potential surface as shown in FIG. 4 can be obtained. The equipotential surfaces shown in FIGS. 3 and 4 were obtained by the inventor of the present application by simulation using a computer. In this way, the control electrode 26 and the toner carrier 2
The direction of the electric field between 2 and 1 is reversed by the potential applied to the control electrode 26. That is, in FIG. 3, the toner carrier 22
In this state, the toner 21 carried on the toner can fly to the counter electrode 25 side. Further, in FIG. 4, the electric field at the gate 29 of the control electrode 26 is in a shielding state with respect to the toner, and is a state of the electric field in which the flying of the toner 21 is blocked.

However, the electric field between the control electrode 26 and the counter electrode 25 changes its intensity to some extent, and its direction is always perpendicular to the surface of the recording paper 5 and does not change. Therefore, the flying toner 21 that has passed through the control electrode 26 is hardly affected by the flying state thereof depending on the potential of the control electrode 26.

In the above description, the toner 21 is used.
The ring-shaped electrode 27 of the control electrode 26 to pass through
The case where the electric potential applied to-is 150 V has been described as an example, but the electric potential is not particularly limited as long as desired flight control of the toner 21 can be performed. In addition, the control electrode 2
By changing the potential applied to the ring-shaped electrode 27 of No. 6, it is possible to change the degree of swelling of the equipotential surface near the gate 29 of the control electrode 26, that is, the state of curving toward the toner carrier 22 side. Therefore, the electric force acting on the toner 21 passing through the gate 29 can be changed. Thereby, the dot diameter (FL) of the image formed on the recording paper 5 can be arbitrarily adjusted by appropriately changing the potential applied by the control power supply unit 3l.

The potential applied to the ring-shaped electrodes 27 ... Of the control electrode 26 to prevent passage of the toner 21 is
It is not particularly limited. Specifically, the above potential may be determined, for example, by conducting an experiment or the like.

Here, the image forming apparatus uses the recording paper 5 of A4 size.
Has a processing capacity capable of processing 6 sheets per minute in the vertical direction (longitudinal direction), the counter electrode 25
The moving speed of the recording paper 5 above is about 30 mm / s.
It becomes ec. Assuming that the resolution is 300 DPI, the processing time required for each dot of the image formed on the recording paper 5, that is, the control electrode unit 31 applies to the ring-shaped electrodes 27 in accordance with the image signal. Pulse width T
(Sec) is about 2.8 × 10 ⁻³ sec or less.

The time t for the toner 21 to fly to the recording paper 5 sent from the toner carrier 22 along the counter electrode 25 is
Under the various conditions described above, the calculation and the measurement by the high-speed camera are about 220 μsec.
2 to the control electrode 26, the time t0 is about 140 μ
sec. Conventionally, the pulse width T of the potential applied to fly the toner 21 applied to the ring-shaped electrode 27 is set to t <T in relation to the flight time t. Therefore, the recording speed cannot be increased due to the limitation of the pulse width T.

Therefore, when the toner 21 passes through the position of the control electrode 26, the control electrode 2 is irrespective of the potential applied to the ring-shaped electrode 27 of the control electrode as shown in FIGS.
Since the electric field direction between 6 and the counter electrode 25 is constant, the electric field flies to the counter electrode 25 side and reaches the recording paper 5 as it is. Therefore, even if the potential (150 V) applied to pass the toner 21 through the gate 29 is switched to a potential (−200 V) at which the toner 21 does not pass through the gate 29 after the toner 21 passes through the ring-shaped electrode 27, The flying toner continues to fly and reaches the recording paper 5 to form an image.

In this embodiment, if the pulse width T of the electric potential applied to the ring-shaped electrode 27 of the control electrode 26 in order to fly the toner 21 is 180 μsec, the sufficiently-floating toner reaches the recording paper 5. To do. The time required for the toner 21 carried at the position corresponding to the gate 29 on the surface of the toner carrier 22 to fly, that is, the time when the potential applied to the control electrode 26 to pass through the gate 29 is applied (pulse). If width is T,
The potential applied to the control electrode 26 is as shown in FIG. 5 depending on the desired image data. In FIG. 5, between the flight time t and the pulse width T, t = 220 μsec> T =
The relationship of 150 μsec> t0 = 140 μsec holds. That is, the potential for causing the toner to fly is 150
The pulse width T, which is a period for applying V to the ring-shaped electrode 27 of the control electrode 26, is set to 150 μsec, and then −200 V is applied to the ring-shaped electrode as the non-flying potential of the toner.

At the time when the voltage of -200 V is applied, the flying toner 21 flies to the recording paper 5, but the flying of the toner on the toner carrier 22 is blocked. Therefore, the time for flying the toner to form the next line can be shortened. In other words, the time period T0 for raising the potential (150 V) to fly can be shortened. As a result, even if the flight time of the toner is the same as the conventional one, the recording speed can be increased by the amount that the period T0 can be shortened as compared with the conventional one. It will be possible.

The above is based on the control of the control potential applied to the control electrode according to the image signal, and the image is directly formed on the recording paper 5 according to the image signal. By controlling the application of the pulse width T to the control electrode 26 in this state, the flight period of the toner is shortened.

The present invention resides in the timing control for applying a potential to the control electrode 26 and the counter electrode 25 at the stage before the image formation on the recording paper 5 as described above, that is, at the beginning of the image forming operation.

Therefore, the embodiment of the present invention will be described in detail with reference to the timing chart shown in FIG. 6 regarding the potential application to the control electrode 26 and the potential application to the counter electrode 25. According to this embodiment, before the recording paper 5 is conveyed by the pickup roller 6, the operation of the image forming unit 1 is controlled in advance in the following order as described above.

First, the rotation of the toner carrier 22 is started in advance by a driving device (not shown) as described in the flowchart of FIG. That is, the drive motor for rotating the toner carrier 22 is set to the timing t1 in FIG.
Drive at the point of. This is the timing of step n7 of the control flowchart shown in FIG.

Then, the toner carrier 22 starts to rotate, and the ring-shaped electrodes 27 ... Of the control electrode 26 are rotated for a predetermined time, that is, the amount of charge of the toner carried on the toner carrier 22 is stable. In the control power supply section 31, the potential (-2
00V) is applied. This applied taming is taming t2 after taming t1 as shown in FIG.
It is the timing of step n8 in the flowchart of FIG.

After that, the support roller 16a is rotationally driven, and the dielectric belt 24 starts to rotate. Then, the counter electrode 2 is aligned with the timing of this rotational drive.
A high voltage is applied to 5 by a high voltage power supply 30. The rotation of the support roller 16a and the application timing of the counter electrode 25 are timing t3 in FIG. 6 and step n9 in the flowchart of FIG.

For the drive control at the above timing,
Depending on the timing of applying the potential to the ring-shaped electrodes 27, the toner layer on the surface of the toner carrier 22 does not have a desired charge amount when the toner carrier 22 starts to rotate slowly or at the same time. Not enough toner. in addition,
The toner layer immediately after the toner carrier 22 starts to rotate,
Often the layer thickness is not at the desired value and is never stable. Further, unless the toner layer is stable, the amount of reversely charged toner is large, and the charge amount is not stable.

In such a toner state, the ring-shaped electrode 2
Even when a potential that does not cause the toner to fly is applied to 7 ..., Reversely charged toner or toner with an unstable charge amount may reach the ring electrodes 27. If in this state,
When a high voltage is applied to the counter electrode 25, the toner reaching the gates 29 of the ring-shaped electrodes 27 ...
Will also fly to the counter electrode.

As described above, the toner 21 that has accidentally fly
In the worst case, the dielectric belt 24 becomes dirty, or in the worst case, the accidentally-fused toner 21 moves the electric charge of the toner 21 to the surface of the dielectric belt 24, so that an appropriate surface potential cannot be obtained.
Therefore, the applied potential of the charging brush 14 and the dielectric belt 2
4 A desired charge is not supplied from the charging brush 14 to the recording paper 5 due to the potential difference from the surface potential, and not only proper electrostatic attraction due to the charge is not performed, but also the recording itself becomes unstable and the image quality is deteriorated. It may deteriorate.

Further, when the toner 21 reaching the control electrode 26 adheres to the control electrode 26, the electric potential of the control electrode 26 that causes the toner 21 on the toner carrier 22 to fly or not fly due to the electric charge of the toner 21. In some cases, the predetermined electric field does not act and the flight control of the toner 21 becomes impossible. If the toner 21 that reaches the control electrode 26 accidentally adheres to the gate 29, the uncontrollable toner 21 may cause the gate 29 to be clogged, which also hinders the flying toner.

In this respect, if the application of the voltage to the control electrode 26 and the counter electrode 25 is controlled according to the timing shown in FIG. 6 of the present invention, the potential applied to the ring-shaped electrodes 27 of the control electrode 26 becomes the toner. After the rotation of the carrier 22 is started, the timing t when the charge amount of the toner 21 becomes stable
It is 2. Further, at the subsequent timing t3, high voltage is applied to the counter electrode 25. Therefore, a strong electric field is not formed at least in the gate 29 of the control electrode 26 while the toner 21 is unstable,
The strong electric field acts after stabilization.

Therefore, the above-mentioned problems are eliminated. That is, while the charge amount of the toner is stable, the control electrode 26
Since a potential is applied to the toner carrier 22 while the toner does not fly, the toner 21 carried on the toner carrier 22 is prevented from flying, and the toner flying to the control electrode 26 side disappears. Moreover, since the high voltage is applied to the counter electrode 25 after the predetermined potential is applied to the control electrode 26, the toner 21 on the toner carrier 22 is still maintained at this point.
However, as described above, the application of the non-flying potential to the control electrode 26 eliminates the toner flying to the counter electrode 25 side.

Here, the toner 21 is in a stable state, for example, the timing at which the charge amount becomes stable depends on the physical properties of the toner used.
It is determined by the rotation speed of the toner carrier 22 and the like. Therefore, it may be obtained and set in advance through experiments or the like.
For example, the rotation speed of the toner carrier 22 is 30 mm / se.
In the case of c, the time (ts) until the toner used reaches a predetermined charge amount is obtained in advance by experiments or the like, and this time is set. Then, the toner carrier 22 is rotated, and after a set time (ts), a potential at which the toner does not fly is applied to the control electrode 26, and then a high voltage is applied to the counter electrode 25.

As described above, the toner 21 becomes in a stable state before the image forming operation is performed, and the above-mentioned control electrode 26 is formed.
After applying a potential to prevent the toner from flying to the counter electrode 25
When a high voltage is applied to the recording paper 5, it is determined that the preparation of the previous step is completed, the control in step n10 and the subsequent steps in FIG. 7 is executed, and the image control potential in step n12 is applied to the control electrode 26, whereby Image formation is started. At this time, the toner reaches the desired position on the recording paper 5 without being disturbed, and the toner image by dots according to the image signal is directly formed in a normal state.

In the description of the embodiment of the present invention, the control electrode 2
Although a single drive control electrode as shown in FIG. 2 is used as 6, the shape of the control electrode can be similarly implemented by a configuration using a matrix drive as shown in FIG. The matrix drive does not require as many drives as the number of gates, so that it is possible to significantly reduce the cost and reduce the cost.

As shown in FIG. 8, the control electrode 26 is connected to the substrate 2
Strip-shaped electrode groups 27a and 27b are formed on the front surface and the back surface of 6a in a state of intersecting (intersecting) each other. Gates 29 for passing the toner flow are formed at respective positions where the strip-shaped 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 strip-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 a 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.

With the control electrode 26 having such a configuration, the same effect as that in the case of the above-described embodiment can be obtained. That is, if the toner carrier 22 is first rotated and then the charge amount of the carried toner becomes stable, after applying a potential at which the toner does not fly to each of the strip-shaped electrode groups 27a and 27b of the control electrode 26 described above, Control may be performed so that a high voltage is applied to the counter electrode 25.

Further, the case where the visualized particles are toners has been described, but the visualized particles may be ink or the like. Further, the configuration of the toner supply unit 2 may be a configuration 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.

[0085]

As described above, the image forming apparatus operates the carrier carrying the image-forming particles at the beginning of the recording operation, particularly before forming the image on the recording paper, to stabilize the image-forming particles. After that, since a potential for controlling the flying of the visualized particles is applied to the control electrode, it is possible to prevent the visualized particles on the carrier, for example, the toner from accidentally flying, and the toner adheres to the control electrode side. You can also eliminate things that you do. As a result, the electric field applied between the control electrode and the carrier does not change due to the attached charged toner, and the gate formed on the control electrode does not become clogged.

Further, the counter electrode is loaded on the carrier after a potential which does not allow the visualized particles to pass through is applied to the control electrode.
Since a high voltage that allows the visualized particles to fly is applied, the visualized particles are prevented from being mistakenly flown via the control electrode when a strong electric field is applied. In particular, since the developer particles are e.g. toner to the control electrode portion is not able to wear with, is not that the toner flies to the counter electrode side. Therefore, also eliminates soiling the recording paper as a recording medium at a toner.

Furthermore, after the visualized particles have stabilized, the above-mentioned application to the control electrode to apply a high voltage to the counter electrode causes the visualized particles on the carrier to erroneously occur on the counter electrode side. It will not fly up to.

Therefore, after the recording on the recording paper is started, the recording paper is not contaminated by the image-forming particles, for example, the toner, and the toner remains on the recording paper under the action of an electric field in a normal state. After reaching the predetermined position, the toner adheres to it and a good quality recorded image can be obtained.

[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 view for explaining the principle of toner flight of the present invention, and is an explanatory diagram showing an equipotential surface when toner is flying.

FIG. 4 is an explanatory diagram for explaining the toner flying principle of the present invention, showing an equipotential surface when the toner does not fly.

FIG. 5 is a timing chart showing timings applied to control electrodes.

FIG. 6 is a timing chart for explaining timing control of rotational driving of the toner carrier, voltage application to the control electrode, and high voltage application to the counter electrode according to the present invention.

FIG. 7 is a flowchart showing the flow of a recording control operation.

FIG. 8 shows another specific example of the control electrode and is a plan view of the control electrode having a matrix configuration.

FIG. 9 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) 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)

Claims (3)

(57) [Claims] 1. A carrier for supporting the visualized particles, a counter electrode arranged so as to face the carrier, and a passage for the visualized particles arranged between the carrier and the counter electrode. A control electrode having a plurality of gates, and a potential that causes a predetermined potential difference between the carrier and the counter electrode is applied, and the potential applied to the control electrode is changed so that the opposing conductive to control the passage of the gate
In an image forming apparatus provided with a control means for forming an image on a recording medium conveyed at the highest level, the control means is a stage before starting the image forming operation.
The charge amount of the visualized particles carried on the carrier is stable.
Until, without imparting a voltage to the control electrode, the upper
After the amount of charge of the visualized particles is stabilized, the visualized particles are
An image forming apparatus characterized by applying a potential which does not fly from the carrier . 2. The control means further performs an image forming operation.
As a step before starting, flying visualized particles to the counter electrode
To the control electrode without applying a potential for
After applying a potential that does not fly the visualized particles,
Apply a high pressure to fly the visualized particles carried
The image forming apparatus according to claim 1, wherein: 3. The control means further applies a high voltage to the counter electrode.
By applying the
By controlling by applying a potential according to the image signal to the pole
Image forming operation on the recording medium conveyed on the counter electrode
The image forming apparatus according to claim 2, which is started .