JPH11320948A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus capable of high-quality printing without printing omission. SOLUTION: The toner carried on a carrying roller 22 is:
It is attracted to the opposing electrode 25 arranged opposite to the carrying roller 22. An electrically insulating substrate having a plurality of through holes 29 is disposed between the support roller 22 and the counter electrode 25. A drive potential or a non-drive potential is selected and applied to the first control electrode 27a provided on the support roller 22 side of the through hole 29, and is applied to the second control electrode 27b provided on the counter electrode 25 side of the through hole 29. Also, a drive potential or a non-drive potential is selected and applied. Before the start of the printing state, the potential at which the developer is attracted to the carrier is applied to the first or second control electrode, so that high-quality printing can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which is applied to a digital copying machine, a facsimile machine, a digital printer or a plotter, and forms an image directly on a recording medium by flying a developer.

[0002]

2. Description of the Related Art As a technique for forming a visible image on a recording medium such as recording paper based on an electric signal output from a computer, a word processor, a facsimile, or the like, an ink jet method, a fusion method for melting and transferring ink. 2. Related Art An image forming apparatus using a thermal transfer method, a sublimation thermal transfer method in which ink is sublimated and transferred, and an electrophotographic method are known.

[0003] With the recent increase in printing speed, image quality, and the cost of image forming apparatuses, the ink-jet system, which is a non-impact, relatively simple structure in which a print head is integrated, is often used. It has become to. However,
In the ink-jet method, since a liquid ink is used, bleeding may occur on paper and a good image may not be obtained.In addition, when performing overprinting in color printing, it is not possible to expect a mixed color of ink. There are problems such as
When high image quality is required, printing using an electrophotographic toner is adopted. Printing with toner, without blurring, in addition to obtaining a visually excellent image with a dark color tone,
In color printing, different color toners are mixed in the fixing process, and a good mixed color is obtained. From such a thing,
There has been proposed a direct printing method using toner in which a simple configuration of the ink jet method is combined with image printing without bleeding using toner.

For example, Japanese Patent Application Laid-Open No. 4-358856 discloses an aperture electrode having an opening, a toner carrier for conveying charged toner near the opening, and a toner carrier opposed to the aperture electrode and having a toner carrier. There has been proposed a direct printing method in which an image forming apparatus is configured with an opposing electrode provided on the opposite side, and an image is formed by controlling the modulation of toner carried on a toner carrier with an aperture electrode.

[0005]

Further, in order to simplify the circuit system, generally, a driving circuit of a matrix driving system is often used. In the matrix driving method, a plurality of scanning signal side electrodes and printing signal side electrodes respectively extending vertically and horizontally are arranged, and the printing signal is applied to the selected printing signal side electrode in synchronization with the scanning signal applied to the scanning signal side electrode. This is a driving method in which toner is caused to fly to dots that need printing by outputting. However, in the matrix driving method, printing leakage may occur. The following three factors can be considered as factors of such print omission.

First, even in a half-select state in which only one of the scanning signal side electrode and the printing signal side electrode is at the driving potential, a part of the toner flies and printing leaks. In particular, there is a great effect when only the electrodes arranged in the vicinity of the flying toner on the scanning signal side and the printing signal side have the driving potential. Secondly, the next print timing is reached while the toner that has flown once from the carrier does not return to the carrier, and the toner flies in the half-selected state, causing print leakage. Third, the toner flying from the carrier adheres to the electrode on the scanning signal side or the printing signal side and flies again in the half-select state of the subsequent printing timing, resulting in printing leakage. The printing leakage generated as described above deteriorates the printing quality.

An object of the present invention is to provide an image forming apparatus which enables high-quality printing without printing leakage.

[0008]

SUMMARY OF THE INVENTION The present invention provides at least one
A carrier that carries a charged developer of a color, a counter electrode arranged to face the carrier, a counter electrode for attracting the developer from the carrier, and a plurality of electrodes disposed between the carrier and the counter electrode. A first control electrode, comprising: an electrically insulating substrate having a through hole; a first control electrode disposed around the through hole on the carrier side; and a second control electrode disposed around the through electrode on the counter electrode side. By selecting one of the driving potential and the non-driving potential applied to the second control electrode and selecting one of the driving potential and the non-driving potential applied to the second control electrode. A printing state in which the developer is allowed to pass through the through-hole and the developer is attached to the recording medium conveyed between the second control electrode and the counter electrode, and a non-printing state in which the developer is prevented from passing through the through-hole is prohibited. In an image forming apparatus that selects one of the printing states Before the start of printing state, an image forming apparatus characterized by imparting a potential developer is attracted to the carrier to the first control electrode and the second control electrode.

According to the present invention, a drive potential or a non-drive potential is selected and applied to the first control electrode, and a drive potential or a non-drive potential is similarly selected and applied to the second control electrode. And four types of potential application states. 4
Only when the drive potential is applied to both the first control electrode and the second control electrode among the different application states, the developer passes through the through-hole and printing is performed. In the other three application states, the developer does not pass through the through-hole and printing is not performed.

In such an image forming apparatus, before the printing state is started, that is, before the first control electrode and the second control electrode are both at the drive potential, the potential at which the developer is attracted to the carrier is required. Is applied to the first control electrode or the second control electrode. As a result, the excess developer floating between the substrate and the carrier or the excess developer adhering to the substrate and the first control electrode is drawn back toward the carrier before the start of the printing state. In addition, printing leakage due to floating or adhered developer can be prevented, and high-quality printing can be performed.

The present invention is also directed to a carrier for supporting at least one color charged developer, a counter electrode disposed to face the carrier and attracting the developer from the carrier, and a counter electrode for the carrier. An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the through-hole on the counter electrode side. A control electrode, and selects one of a drive potential and a non-drive potential applied to the first control electrode, and selects one of a drive potential and a non-drive potential added to the second control electrode By selecting the printing condition, the developer is allowed to pass through the through-hole and the developer is attached to the recording medium conveyed between the second control electrode and the counter electrode. Any of the non-printing states that prohibit passing through the through hole In an image forming apparatus either select one, driving time of the first control electrode in the printing state is an image forming apparatus characterized by shorter than the drive time of the second control electrode.

According to the present invention, the drive time of the first control electrode is made shorter than the drive time of the second control electrode, so that the first control electrode close to the carrier is driven faster than the second control electrode. Thus, printing can be performed using only the developer that has already begun to fly without attracting a new developer. This reduces excess developer floating or adhering in the vicinity of the first control electrode, so that printing leakage can be prevented and high quality printing can be achieved.

Further, the present invention provides a carrier for carrying at least one color developer, a counter electrode disposed to face the carrier and attracting the developer from the carrier, and a counter electrode facing the carrier. An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the through-hole on the counter electrode side. A control electrode, and selects one of a drive potential and a non-drive potential applied to the first control electrode, and selects one of a drive potential and a non-drive potential added to the second control electrode By selecting the printing condition, the developer is allowed to pass through the through-hole and the developer is attached to the recording medium conveyed between the second control electrode and the counter electrode. Any of the non-printing states that prohibit passing through the through hole In one of the image forming apparatuses, the driving time of the first control electrode is shorter than the time until the developer separates from the carrier and reaches the first control electrode. is there.

According to the present invention, the drive time of the first control electrode is made shorter than the time required for the developer, which has left the carrier, to reach the first control electrode. Printing can be performed using the developer that has already begun to fly without drawing the image agent. This makes it possible to reduce the amount of the developer floating or adhering, to prevent printing leakage, and to realize high-quality printing.

According to the present invention, there is further provided a carrier for carrying at least one color developer, an opposing electrode arranged to face the carrier, and for attracting the developer from the carrier; An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the through-hole on the counter electrode side. A control electrode, and selects one of a drive potential and a non-drive potential applied to the first control electrode, and selects one of a drive potential and a non-drive potential added to the second control electrode By selecting the printing condition, the developer is allowed to pass through the through-hole and the developer is attached to the recording medium conveyed between the second control electrode and the counter electrode. Any of the non-printing states that prohibit passing through the through hole In one of the image forming apparatuses, the longer the distance between the carrier and the first control electrode, the longer the drive time of the first control electrode, or the longer the distance between the carrier and the second control electrode, the greater the second control. An image forming apparatus characterized in that the driving time of the electrode is long.

According to the present invention, the longer the distance between the carrier and the first control electrode, the longer the drive time of the first control electrode, for example, the more uniform the distance between the carrier and the first control electrode. If not, the developer can be made to fly uniformly by compensating for the difference, and high quality printing can be realized. Similarly, by increasing the drive time of the second control electrode as the distance between the carrier and the second control electrode is longer, for example, when the distance between the carrier and the second control electrode is not uniform, The developer can be made to fly uniformly by compensating for the difference, and high-quality printing can be realized.

According to the present invention, there is also provided a carrier for carrying at least one color developer, an opposing electrode arranged to face the carrier, and for attracting the developer from the carrier; An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the through-hole on the counter electrode side. A control electrode, wherein one of a scanning signal and a printing signal consisting of a driving potential and a non-driving potential is applied to the first control electrode, and the other is applied to the second control electrode. In an image forming apparatus for selectively adhering a developer to a recording medium conveyed between a control electrode and a counter electrode, a driving time of a print signal is shorter than a non-driving time. is there.

According to the present invention, one of the scanning signal and the printing signal is applied to the first control electrode, and the other is applied to the second control electrode. The scanning signal is a signal that repeats a driving potential and a non-driving potential at a constant cycle,
The print signal is a signal composed of a drive potential and a non-drive potential synchronized with the scanning signal. Therefore, there are four potential application states, and the developer passes through the through hole only when the drive potential is applied to both the first control electrode and the second control electrode among the four application states. Then, printing is performed. In the other three cases, the developer does not pass through the through-hole and printing is not performed.

In such an image forming apparatus, the non-driving time of the print signal is ensured longer than the driving time.
Excess developer is pulled back to the carrier, and the amount of developer floating or adhering is reduced. As a result, printing quality can be prevented and printing with high image quality can be realized.

According to the present invention, there is also provided a carrier for carrying at least one color developer, an opposing electrode disposed to face the carrier, and for attracting the developer from the carrier; An electrically insulating substrate having a plurality of through holes, a plurality of first control electrodes disposed around the carrier side of the through hole, and a plurality of first control electrodes disposed around the counter electrode side of the through hole; By providing a plurality of second control electrodes, applying one of a scanning signal and a printing signal consisting of a driving potential and a non-driving potential to the first control electrode, and applying the other to the second control electrode, In an image forming apparatus for selectively attaching a developer to a recording medium conveyed between a second control electrode and a counter electrode, one of a first control electrode and a second control electrode to which a scanning signal is applied Is more electrical than the other to which the print signal is applied. An image forming apparatus, wherein the number is small.

According to the present invention, by making the number of electrodes on the scanning signal side smaller than the number of electrodes on the printing signal side, one scan can be completed in a short time and high-speed printing can be performed. Become. Alternatively, a long non-driving time can be taken in place of high-speed printing, a time for returning the floating or adhered excess developer to the carrier is secured, and high-quality printing can be realized by preventing printing leakage. .

According to the present invention, there is also provided a carrier which carries at least one color negatively charged developer and is grounded, and a counter electrode which is arranged to face the carrier and attracts the developer from the carrier. An electrically insulating substrate disposed between the carrier and the counter electrode and having a plurality of through holes; a first control electrode disposed around the carrier on the side of the through hole; And a second control electrode disposed on the first control electrode,
A recording medium conveyed between a second control electrode and a counter electrode by applying one of a scan signal and a print signal consisting of a drive potential and a non-drive potential, and applying the other to the second control electrode. In the image forming apparatus for selectively adhering the developer to the image forming apparatus, the driving potential of the scanning signal is higher than the ground potential, the non-driving potential of the scanning signal is lower than the ground potential, An image forming apparatus characterized in that the potential is equal to or higher than the ground potential.

According to the present invention, the drive circuit for the print signal can be realized with a single power supply, and the integration can be simplified.

According to the present invention, there is also provided a carrier for carrying at least one color developer, a counter electrode disposed to face the carrier, and for attracting the developer from the carrier; An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the through-hole on the counter electrode side. A control electrode, and selects one of a drive potential and a non-drive potential applied to the first control electrode, and selects one of a drive potential and a non-drive potential added to the second control electrode By selecting the printing condition, the developer is allowed to pass through the through-hole and the developer is attached to the recording medium conveyed between the second control electrode and the counter electrode. Any of the non-printing states that prohibit passing through the through hole An image forming apparatus for selecting one of the two, further comprising: an insulating film covering the first control electrode and the second control electrode; and a conductive member arranged in contact with the insulating film. is there.

According to the present invention, the electric charge accumulated on the surface of the insulating film can be evacuated by the conductive member, the influence of the developer on the flight can be eliminated, and high quality printing can be realized by preventing printing leakage. Can be. Alternatively, the print density can be controlled by positively applying a charge to the surface of the insulating film via the conductive member.

The present invention is further characterized by further comprising a potential adjusting mechanism for applying a predetermined potential via a conductive member in order to adjust the potential on the surface of the insulating film.

According to the present invention, the print density can be controlled by positively applying charges to the surface of the insulating film via the conductive member.

Further, according to the present invention, when a potential different from a ground potential is applied to the first control electrode or the second control electrode, one end of the conductive member is grounded and the other end is brought into contact with an insulating film. It further comprises a slide mechanism for sliding the conductive member.

According to the present invention, the first control electrode or the second control electrode
When a potential different from the ground potential is applied to the control electrode, the conductive member is slid. At this time, the electrode and the surface of the insulating film operate like a capacitor with the insulating film interposed therebetween, that is, electric charges are induced on the surface of the insulating film facing the electrode via the insulating film in accordance with the electric charge appearing on the charge surface. Is done. Thereby, the print density of the image to be formed can be adjusted. Alternatively, fogging, which is a phenomenon that is printed on a portion of an image that should not be printed, can be adjusted.

Further, the present invention is characterized in that the carrier is a cylindrical roller supported by a shaft, and carries a developer on the surface thereof.

According to the present invention, the carrying of the developer and the application of a constant potential can be realized by a carrier having a simple structure consisting only of a cylindrical roller, and the structure of the apparatus can be simplified.

Further, according to the present invention, the carrier has a belt for carrying a developer, a pair of rollers for bridging the belt, and a back electrode disposed opposite to the second control electrode with the belt interposed therebetween. It is characterized by the following.

According to the present invention, since the developer is carried on the belt stretched over the pair of rollers, the distance between the carrier and the first control electrode can be made uniform, and uneven printing can be eliminated. High-quality printing is possible.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, image forming apparatuses 101 and 102 according to an embodiment of the present invention will be described with reference to the drawings. The configuration corresponding to the negatively charged toner will be described in detail as the image forming apparatuses 101 and 102. However, when a positively charged toner is used, the potentials to be applied to various portions may be set as appropriate.

(First Embodiment) FIG. 1 is a view showing an image forming apparatus 101 according to a first embodiment of the present invention, and FIG. 2 is a view showing a main part of the image forming apparatus 101. The image forming apparatus 101 includes a sheet feeding unit 10, an image forming unit 1, and a fixing unit 1.
1 and the like. The image forming unit 1 visualizes an image corresponding to an image signal on a recording sheet 5 as a recording medium using toner as a developer. That is, the image forming apparatus 101 directly forms an image on the recording paper 5 by controlling the flying of the toner based on an image signal while causing the toner to fly and adhere to the conveyed recording paper 5. .

The paper feed unit 10 is provided upstream of the image forming unit 1 in the transport direction of the recording paper 5, and is a paper cassette 4 that stores the recording paper 5, and a pickup roller 6 that sends out the recording paper from the paper cassette 4. , A pair of registration rollers 11
1 and 112 and a paper feed sensor (not shown) for detecting the sent recording paper 5. The pickup roller 6 is driven by a driving device (not shown).

The fixing unit 11 is provided downstream of the image forming unit 1 in the transport direction of the recording paper 5, and fixes the toner image formed on the recording paper 5 to the recording paper 5 by heating and pressing. . The fixing unit 11 includes a heating roller 12, a heater 13, a pressure roller 14, a temperature sensor 15, and a temperature control circuit 80. The heating roller 12 is made of, for example, an aluminum tube having a thickness of 2 mm. The heater 13 is formed of, for example, a halogen lamp, and is built in the heating roller 12. The pressure roller 14 is made of, for example, a silicone resin. The heating roller 12 and the pressure roller 14 are provided so as to face each other, and have springs (not shown) at both ends of each shaft for pressing the recording sheet 5 therebetween. The spring applies a load of, for example, 2 kg.

The temperature sensor 15 measures the temperature of the surface of the heating roller 12. The temperature control circuit 80 is controlled by a main control unit, which will be described later, controls on / off of the heater 13 based on the measurement result of the temperature sensor 15, and maintains the surface temperature of the heating roller 12 at, for example, 150 ° C. . Further, the fixing unit 11 includes a paper discharge sensor (not shown) that detects that the recording paper 5 has been discharged. The materials of the heating roller 12, the heater 13, the pressure roller 14, and the like are not particularly limited. As described above, the fixing unit 11 fixes the toner image by heating and pressing the recording paper 5, but may have a structure in which the toner image is fixed to the recording paper only by heating or only pressing.

Although not shown, a discharge roller for discharging the recording sheet 5 embedded in the fixing unit 11 and a discharge tray for receiving the discharged recording sheet 5 are further downstream of the fixing unit 11. Is provided. The heating roller 12, the pressure roller 14, and the paper discharge roller are driven by a driving device (not shown).

The image forming section 1 includes a toner supply section 2, a printing section 3, and the like. The toner supply unit 2 includes a toner storage tank 20 storing the toner, a cylindrical supporting roller 22 that supports the toner by magnetic force, and a toner storage tank 2.
And a doctor blade 23 that is provided inside the toner cartridge 0 to charge the toner and regulate the thickness of the toner layer carried on the outer peripheral surface of the carrying roller 22. Doctor blade 23
Is provided on the upstream side in the rotation direction of the carrying roller 22 so that the distance from the outer peripheral surface of the carrying roller 22 is, for example, 60 μm. The toner is, for example, a magnetic toner having an average particle diameter of 6 μm, and is charged by the doctor blade 23 such that the charge amount is, for example, −4 μC / g to −5 μC / g. The distance between the doctor blade 23 and the carrying roller 22, the average particle diameter of the toner, the charge amount, and the like are not particularly limited.

The carrying roller 22 is driven by a driving device (not shown), and rotates in the direction of arrow A in the figure, for example, at a surface speed of 80 mm / sec. In addition, the carrying roller 2
Numeral 2 is a ground (not shown) at a position facing the doctor blade 23 inside the support roller 22 and facing a substrate 26 described later. Thus, the carrying roller 22 can carry the toner on the outer peripheral surface. Further, the toner carried on the outer peripheral surface of the carrying roller 22 forms ears at positions corresponding to the positions on the outer peripheral surface.

The rotation speed of the carrying roller 22 is not particularly limited. Further, instead of carrying the toner by the magnetic force, the carrying roller 22 may be configured to carry the toner only by the electric force or by combining the electric force and the magnetic force.

The printing unit 3 includes a counter electrode 25 facing the outer peripheral surface of the support roller 22, a high-voltage power supply 30 for supplying a high potential to the counter electrode 25, and a substrate 26 provided between the support roller 22 and the counter electrode 25. , A charge elimination power supply 17 for giving a charge elimination potential to the charge elimination brush 9, a charging brush 8 for charging a recording sheet, a charging power supply 18 for giving a charge potential to the charging brush 8, a dielectric belt 24, and a dielectric belt 24. Rollers 16 a and 16 b and a cleaner blade 19 are provided. The same potential as the counter electrode 25 is applied to the roller 16a by the high voltage power supply 30. Counter electrode 25
Is made of, for example, an aluminum plate having a thickness of 1 mm, and is provided so that the distance from the outer peripheral surface of the carrying roller 22 is, for example, 1.1 mm.

The dielectric belt 24 is made of PVDF (polyvinylidene fluoride) as a base material and has a volume resistivity of 10%.
10 Ω · cm, and the thickness is 75 μm. Roller 1
6a and 16b are rotationally driven by a driving device (not shown), and rotationally move the dielectric belt 24 in the arrow direction B at a speed of, for example, 30 mm / sec. A voltage of, for example, 2.3 kV is applied to the counter electrode 25 by the high-voltage power supply 30, and the carrying roller 22 is grounded. An electric field necessary for causing the toner 21 carried on the carrying roller 22 to fly toward the facing electrode 25 is formed between the opposed electrode 25 and the carrying roller 22 by a high voltage applied from the high voltage power supply 30. .

The charging brush 8 is provided on the upstream side of the substrate 26 in the rotation direction of the dielectric belt 24 in pressure contact with the dielectric belt 24. The charging brush 8 includes a charging power source 18.
As a result, 1.2 kV is applied as a charging potential. The neutralization brush 9 is provided on the downstream side of the substrate 26 in the rotation direction of the dielectric belt 24 in pressure contact with the dielectric belt 24. The static elimination brush 9 is applied with a static elimination potential of 2.5 kV by the static elimination power supply 17 and removes unnecessary charges existing on the surface of the dielectric belt 24. Note that the potential indicated by the control electrode control signal differs depending on the configuration of the image forming apparatus, and is determined from physical conditions such as electrode arrangement.

When an unexpected situation such as a paper jam (paper jam) occurs and toner adheres to the surface of the dielectric belt 24, the cleaning blade 19 removes the toner to remove static electricity. Thereby, the recording paper 5
Can be prevented from being contaminated by the toner.
The material of the counter electrode 25, the distance between the counter electrode 25 and the support roller 22, and the rotation speed of the counter electrode 25 are not particularly limited.

Although not shown, the image forming apparatus 101
A main control unit that controls the entire image forming apparatus as a control circuit; an image processing unit that converts image data obtained from an image reading device that reads an image of a document or the like into a format of image data to be printed; And an image forming control unit for converting the image data obtained from the image processing unit into data to be given to a first control electrode 27a and a second control electrode 27b to be described later. I have.

FIG. 3 is a plan view showing the structure of the first control electrode and the second control electrode. The substrate 26 is an electrically insulating substrate, and is arranged in parallel with the counter electrode 25, between the counter electrode 25 and the support roller 22, such that the distance from the outer peripheral portion of the support roller 22 is, for example, 100 μm, It is fixed by a support member (not shown). A through hole 29 penetrating from the support roller 22 side to the counter electrode 25 side is formed in the substrate 26.
Is formed. On the surface of the substrate 26 on the supporting roller 22 side,
A plurality of first control electrodes 27a are provided, and a plurality of second control electrodes 27b are provided on the surface of the substrate 26 facing the counter electrode 25. Each of the first control electrodes 27a1, 27a2,... Extends in a belt-like shape in the transport direction of the recording paper 5, and is arranged in parallel with each other. Each of the second control electrodes 27b1, 27b2,.
Have a shape extending in a belt shape in a direction perpendicular to the conveying direction of the recording paper 5 and are arranged in parallel to each other. In addition, 27a
1, 27a2,... Indicate individual first control electrodes, and 27
b1, 27b2,... indicate individual second control electrodes,
7a is a general term for 27a1, 27a2,.
. are reference symbols for collectively referring to b1, 27b2,. The through-hole 29 is disposed at the intersection of the first control electrode 27a and the second control electrode 27b, and the first control electrode 27a and the second control electrode 27b are formed in an opening 29a that opens on the carrier roller 22 side of the through-hole 29. And an opening 29 b that opens to the counter electrode 25 side of the through hole 29. Thus, the toner flow can pass through the substrate 26.

First control electrode 27a and second control electrode 2
A potential is applied to each of the control power supply units 7b by the connected control power supply unit 31. The electric field applied between the support roller 22 and the counter electrode 25 is changed by the control power supply unit 31, and the flying of the toner from the support roller 22 to the counter electrode 25 is controlled. Since the toner is negatively charged, a potential sufficiently lower than 3.2 kV of the counter electrode 25 is applied to the second control electrode 2.
7b, the toner can fly in the direction from the second control electrode 27b toward the counter electrode 25.

The substrate 26 is, for example, 25 μm thick and made of polyimide resin. The first control electrode 27a and the second control electrode 27b are made of, for example, copper foil or the like. Each opening 2
The inner diameter of 9a is, for example, 220 μm. Note that the distance between the substrate 26 and the carrying roller 22 is not particularly limited. The inner diameter of the opening 29b is, for example, 160 μm.
It is. The size of the through-hole 29 and the material and thickness of the substrate 26, the first control electrode 27a, and the second control electrode 27b are not particularly limited.

The number of the through holes 29 is, for example, 2560 (320
× 8), and the first control electrode 27a and the second control electrode 27b are electrically connected to the control power supply unit 31 via the power supply line 28 and a high-voltage driver (not shown).

The first control electrode 27a, the second control electrode 27b
The surface and the surface of the power supply line 28 are covered with an insulating film (not shown) having a thickness of 30 μm. Thereby, the first control electrode 27
a, the insulation between the second control electrodes 27b, the insulation between the power supply lines 28, and the insulation between the first control electrode 27a, the second control electrode 27b, and the power supply line 28 that are not connected to each other are ensured. I have. The surfaces of the first control electrode 27a, the second control electrode 27b, and the surface of the power supply line 28 are protected so as not to be short-circuited with another member or a conductive substance. The material and thickness of the insulating film are not particularly limited.

The control power supply 31 inputs a print signal pulse, which is a voltage pulse corresponding to a print image, to the first control electrodes 27a1, 27a2,. Second control electrode 2
7b1, 27b2,...
A scanning signal pulse which is a voltage pulse for sequentially scanning is input. When passing the toner carried by the carrying roller 22 in the direction of the counter electrode 25 with respect to the first control electrode 27a and the second control electrode 27b, the control power supply unit 31 opens the corresponding through hole 29. Set of first control electrodes 27a
And the second control electrode 27b has a driving potential of 1
When 50 V is applied and the voltage is not allowed to pass, for example, the non-drive potential is 0 V, and the non-drive potential -200 V is applied to the second control electrode 27b.
Is given. That is, 150 is applied to the first control electrode 27a.
A pulse composed of two potentials of V and 0 V is input,
The second control electrode 27b has two voltages of 150V and -200V.
A pulse composed of two potentials is input.

The first control electrode 27a and the second control electrode 27b are covered with an insulating film and are gradually charged during printing. As a countermeasure, for example, a high-resistivity film is pasted on the insulating film. In the present invention, however, a conductive member such as a brush contacting the insulating film is provided, and the conductive member can further adjust the output voltage. Connect to power. As a result, the surface of the insulating film can be positively charged to a predetermined potential and the print density can be adjusted.

While keeping one end of the conductive member in contact with the surface of the insulating film as described above and the other end grounded,
A slider for sliding the conductive member along the insulating film is provided. Thus, a capacitor in which the insulating film surface in contact with the conductive member and the first control electrode 27a sandwich the insulating film as a dielectric is formed. The combination of the insulating film surface and the second control electrode also forms a capacitor. Depending on the potential of the first control electrode 27a or the second control electrode 27b,
The charge distribution on the nearby insulating film surface changes variously, and the print density of the formed image can be adjusted.

FIG. 4 is a timing chart showing a matrix driving method. First, the first control electrode 27a1 becomes the driving potential, and at the same time, the second control electrodes 27b1-2
The driving potential or the non-driving potential becomes 7bn according to the image. In FIG. 4, 27b1 is the driving state. As a result, the toner passes through the through hole at the intersection of 27a1 and 27b1, and printing is performed. Next, 27a2 is driven. At the same time, 27b1 and 27bn are turned on, and
The toner passes through the through holes at the intersections of 2 and 27b1 and at the intersections of 27a2 and 27bn, and printing is performed. Similarly, when printing is performed up to 27a4, printing for one line is completed. Here, the printing of one page is completed by feeding the recording paper 5 by one pitch and repeating the printing operation.

Also, as shown in FIG. 4, before the printing state in which the first control electrode 27a and the second control electrode 27b are at the driving potential is started, the non-printing state in which both electrodes are not driven is required. Exists. As a result, the toner is pulled back to the carrying roller 22 before printing.

Further, by setting the pulse width T1 as the driving time of the first control electrode 27a shorter than the pulse width T2 as the driving time of the second control electrode 27b, the floating toner can be reduced. Also, the pulse width T
By setting 1 to be shorter than the time from when the toner leaves the carrying roller 22 to when the toner reaches the passage hole 29, the floating toner can be reduced. Also, the second control electrode 2
By setting the print signal duty ratio applied to 7b to 50% or less, that is, by setting the pulse width T1 shorter than the pulse interval T0, a sufficient time for returning the toner to the carrying roller 22 can be ensured.

By setting the potential applied to the first control electrode 27a to be equal to or higher than the ground potential, the first control electrode 27a can be set to the scanning signal side and the second control electrode 27b can be set to the printing signal side. Since the print signal is generated by a complex circuit such as an IC, the potential of the print signal is limited to the ground potential or more, that is, the potential applied to the first control electrode 27a is set to the ground potential or more. Can be simplified. One of the first control electrode 27a and the second control electrode 27b, which is on the scanning signal side,
By making the number of electrodes smaller than the other one on the print signal side, printing can be speeded up, or the number of scanning pulses per unit time can be reduced, so that printing leakage is reduced.

In the image forming apparatus 10 described above, when the carrying roller 22 is cylindrical, the curvature of the carrying roller 22 has a great influence on printing. That is, the first control electrode 27
Since the distance from the supporting roller 22 is small at the center of the area a, and the distance from the supporting roller 22 is large at the periphery of the first control electrode 27a, the strength of the electric field formed therebetween is different. For example, when the same level of voltage is applied to each electrode of the first control electrode 27a, the first control electrode 27a
In the central portion, the flying amount of the toner is large, and in the peripheral portion, the flying amount is small. As a countermeasure, the driving time of the first control electrode 27a is changed according to the distance between the support roller 22 and the substrate 26. Specifically, the longer the distance between the support roller 22 and the substrate 26, the longer the drive time, so that the amount of flight can be made uniform and good image quality can be obtained.

The printing section 3 of the image forming apparatus 101 can be used as a facsimile printing section or a printing section of a digital copying machine, in addition to a printing section of a printer.

FIG. 5 is a flowchart showing an image forming operation of the image forming apparatus 101 when used as a printing unit of a digital copying machine.

First, in step s1, a document to be copied is placed on the image reading unit by the operator, for example.
A copy start button (not shown) is input. Upon receiving the input operation, the main control unit starts the image forming operation. In the next step s2, the main control unit controls the image reading unit to read the document image. In the next step s3, the read image data is processed by the image processing unit, and in the next step s4, the processed image data is stored in the image memory.

In the next step s5, the image data stored in the image memory is transferred to the image forming control unit. In step s6, the image forming control unit converts the input image data into a control electrode control signal to be given to the control electrode 26. In the next step s7,
When the image forming control unit obtains a predetermined amount of the control electrode control signal, the process proceeds to step s9. If a predetermined amount of the control electrode signal is not obtained, the process proceeds to step s8 to display an error. After step s9, the driving device drives the pickup roller 6 to rotate. The recording sheet in the sheet cassette 4 is sent out by the pickup roller 6 in the direction toward the image forming unit 1 and the sheet feeding sensor detects that the sheet is in a normal sheet feeding state.

Specifically, in step s9, the carrying roller 22 rotates. In the next step s10, a potential of, for example, -200 V is applied to the first control electrode 27a.
In the next step s11, the above-described high potential is applied to the counter electrode 25, the roller 16 is driven, and the dielectric belt 24 conveys the recording paper 5. The recording paper 5 is supplied with a charge due to the potential difference between the charging brush 8 and the roller 16 and is electrostatically attracted to the recording paper 5 on the surface of the printing unit 3 of the image forming unit 1 facing the supporting roller 22 of the dielectric belt 24. Conveyed. A potential is applied to the recording paper 5 by the charging brush 8, and the dielectric belt 2 is charged by the discharging brush 9.
4 is removed. In the next step s12, the pickup roller 6 is driven. Pickup roller 6
The recording paper 5 sent out by the above is conveyed between the charging brush 8 and the roller 16a. Next, in step s13, it is determined whether the sheet is in a normal sheet feeding state based on the detection result of the sheet feeding sensor. If it is normal, the process proceeds to step s15. If it is not normal, the process proceeds to step s14 to display an error.

At step s15, the image forming control unit supplies a control electrode control signal to the control power supply unit 31.
The supply of the control electrode control signal is performed at a timing synchronized with the supply of the paper 5 to the printing unit 3 by the charging brush 8. The control power supply unit 31 is based on the control electrode control signal,
The high voltage applied to the first control electrode 27a and the second control electrode 27b is controlled. That is, a potential of 150 V or -200 V is appropriately applied from the control power supply unit 31 to a predetermined electrode, and the electric field between the first control electrode 27a and the second control electrode 27b is controlled. That is, the through hole 29 of the substrate 26
In the above, the passage and prevention of the toner 21 from the support roller 22 to the counter electrode 25 are appropriately performed according to the image data. 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 by the rotation of the derivative belt 24. Next, the process proceeds to step s16, and the processes of steps s12 to s16 are repeated until printing is completed. When printing is completed, the process returns to step s2.

The recording paper 5 on which the toner image has been formed is separated from the dielectric belt 24 by the curvature of the roller 16b and is conveyed to the fixing unit 11, where the toner image is fixed on the recording paper 5 by the fixing unit 11. Is done. The recording paper 5 on which the toner image has been fixed is discharged onto a paper discharge tray by a paper discharge roller, and a normal discharge is detected by a discharge sensor. Based on this detection operation, the main control unit determines a 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 101 directly forms an image on the recording paper 5, a visualizing member such as a photoconductor or a dielectric drum used in an electrophotographic image forming apparatus is not required. . Accordingly, the operation of transferring the image from the drum or the like to the recording paper 5 is omitted, so that the image does not deteriorate. Therefore, the reliability of the device is improved. In addition, the configuration of the apparatus is simplified, and the number of parts is reduced, so that downsizing and cost reduction can be achieved.

(Second Embodiment) FIG. 6 is a view showing an image forming apparatus 102 according to a second embodiment of the present invention. The image forming apparatus 102 is an image forming apparatus 101 according to the first embodiment.
Since only a part of the configuration is changed, only the changed part will be described below, and the part having the same configuration will be denoted by the same reference numeral as the image forming apparatus 101, and the description will be omitted. In the first embodiment, the carrier is a carrier, but the carrier of the second embodiment includes a belt 22a, a pair of rollers 121 and 122, and a back electrode 123.
The belt 22a has an endless shape and includes rollers 121,
122 and carries the toner on its surface. The back electrode 123 is connected to the second control electrode 27 with the belt 22a interposed therebetween.
b and is grounded, for example.

In the second embodiment, the same operation as in the first embodiment can be performed, and the belt 22a carrying the toner specific to the second embodiment is bridged between the rollers 121 and 122 to form a planar shape. According to this, the carrier and the first control electrode 27a
Can be made uniform, and uneven printing can be eliminated.

In addition, the present invention is not limited to the embodiment described above and shown in the drawings, and it is needless to say that the present invention can be carried out by appropriately modifying it without departing from the scope of the invention.

[0072]

As described above, according to the present invention, before the printing state starts, the potential at which the developer is attracted to the carrier is set to the first potential.
By applying the voltage to the control electrode or the second control electrode, printing leakage due to the floating developer can be prevented, and high-quality printing can be performed.

Further, according to the present invention, by making the drive time of the first control electrode shorter than the drive time of the second control electrode, it is possible to prevent printing leakage and to achieve high quality printing.

According to the present invention, the driving time of the first control electrode is made shorter than the time required for the developer to separate from the carrier and reach the first control electrode, thereby allowing the floating developer to move. Can be reduced, printing leakage can be prevented, and high-quality printing can be realized.

Further, according to the present invention, the longer the distance between the carrier and the first control electrode, the longer the drive time of the first control electrode. For example, the distance between the carrier and the first control electrode is reduced by one. In such a case, the developer can be made to fly uniformly by compensating for the difference, thereby preventing printing leakage and realizing high-quality printing. Alternatively, by increasing the driving time of the second control electrode as the distance between the carrier and the second control electrode is increased, high-quality printing can be realized similarly.

Further, according to the present invention, by setting the drive time of the print signal shorter than the non-drive time, it is possible to prevent printing leakage and realize high quality printing.

Further, according to the present invention, by making the number of electrodes on the scanning signal side smaller than the number of electrodes on the printing signal side, it is possible to prevent printing leakage and realize high quality printing.

According to the present invention, the developer is negatively charged, the carrier is grounded, the scanning signal is composed of a positive driving potential and a negative non-driving potential, and the printing signal is composed of a positive driving potential and a zero driving potential. With the above-described driving potential, a complicated processing circuit for converting the driver IC to a negative potential is not required, and the configuration of the driving circuit for outputting a signal can be simplified.

Further, according to the present invention, the conductive member
High-quality printing can be realized by preventing printing leakage, and furthermore, the printing density can be controlled by positively applying a charge to the insulating film surface via the conductive member.

Further, according to the present invention, the printing density can be controlled by positively applying charges to the surface of the insulating film via the conductive member.

Further, according to the present invention, it is possible to adjust the print density of an image to be formed. Alternatively, the fog can be adjusted.

Further, according to the present invention, the carrying of the developer and the application of a constant potential can be realized by a carrier having a simple structure consisting of only a cylindrical roller, and the structure of the apparatus can be simplified.

Further, according to the present invention, the developer is carried by the belt extending over the pair of rollers, so that the distance between the carrier and the first control electrode can be made uniform, and uneven printing can be achieved. And high quality printing becomes possible.

[Brief description of the drawings]

FIG. 1 is an image forming apparatus according to a first embodiment of the invention.
FIG.

FIG. 2 is a diagram illustrating a part of the image forming apparatus 101 of FIG.

FIG. 3 is a plan view showing a structure of first and second control electrodes.

FIG. 4 is a timing chart showing matrix driving.

FIG. 5 is a flowchart illustrating an image forming operation of the image forming apparatus 101 when used as a printing unit of a digital copying machine.

FIG. 6 is an image forming apparatus 10 according to a second embodiment of the present invention.
FIG.

[Explanation of symbols]

 5 Recording Paper 11 Fixing Unit 16a, 16b Roller 21 Toner 22 Carrying Roller 22a Belt 24 Dielectric Belt 25 Counter Electrode 26 Substrate 27a First Control Electrode 27b Second Control Electrode 28 Feed Line 29 Through Hole 31 Power Supply 101, 102 Image Forming Apparatus 121, 122 Roller 123 Back electrode T1, T2 Drive time T0 Non-drive time

Claims (12)

[Claims] 1. A carrier for carrying at least one charged developer of at least one color, a counter electrode disposed to face the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the opposite electrode side of the through-hole; And selecting one of the driving potential and the non-driving potential applied to the first control electrode, and selecting one of the driving potential and the non-driving potential applied to the second control electrode. This allows the developer to pass through the through-hole and allows the developer to adhere to the recording medium conveyed between the second control electrode and the counter electrode. One of the non-printing states that prohibit passing In the image forming apparatus-option, prior to the start of printing state, the image forming apparatus characterized by imparting a potential developer is attracted to the carrier to the first control electrode and the second control electrode. 2. A carrier for carrying at least one charged developer of at least one color, a counter electrode disposed opposite to the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the opposite electrode side of the through-hole; And selecting one of the driving potential and the non-driving potential applied to the first control electrode, and selecting one of the driving potential and the non-driving potential applied to the second control electrode. This allows the developer to pass through the through-hole and allows the developer to adhere to the recording medium conveyed between the second control electrode and the counter electrode. One of the non-printing states that prohibit passing In the image forming apparatus-option, the image forming apparatus, wherein a drive time of the first control electrode in the print state is shorter than the driving time of the second control electrode. 3. A carrier for carrying at least one charged developer of at least one color, a counter electrode disposed opposite to the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the opposite electrode side of the through-hole; And selecting one of the driving potential and the non-driving potential applied to the first control electrode, and selecting one of the driving potential and the non-driving potential applied to the second control electrode. This allows the developer to pass through the through-hole and allows the developer to adhere to the recording medium conveyed between the second control electrode and the counter electrode. One of the non-printing states that prohibit passing In the image forming apparatus-option, the image forming apparatus driving time of the first control electrode, the developer is equal to or shorter than the time to reach the first control electrode away from the carrier. 4. A carrier carrying at least one charged developer of at least one color, a counter electrode disposed opposite to the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the opposite electrode side of the through-hole; And selecting one of the driving potential and the non-driving potential applied to the first control electrode, and selecting one of the driving potential and the non-driving potential applied to the second control electrode. This allows the developer to pass through the through-hole and allows the developer to adhere to the recording medium conveyed between the second control electrode and the counter electrode. One of the non-printing states that prohibit passing In the alternative image forming apparatus, the longer the distance between the carrier and the first control electrode, the longer the drive time of the first control electrode, or the longer the distance between the carrier and the second control electrode, the longer the drive of the second control electrode An image forming apparatus characterized by a long time. 5. A carrier for carrying at least one charged developer of at least one color, a counter electrode disposed opposite to the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the opposite electrode side of the through-hole; And applying, to the first control electrode, one of a scanning signal and a printing signal each including a driving potential and a non-driving potential,
In an image forming apparatus in which the other is applied to the second control electrode to selectively adhere the developer to the recording medium conveyed between the second control electrode and the counter electrode, the drive time of the print signal is reduced. An image forming apparatus characterized by being shorter than the non-driving time. 6. A carrier for carrying at least one charged developer of at least one color, a counter electrode disposed opposite to the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through-holes disposed therebetween, a plurality of first control electrodes disposed around the through-hole on the carrier side, and a plurality of first control electrodes disposed around the through-hole on the counter electrode side. A second control electrode, wherein one of a scanning signal and a printing signal comprising a driving potential and a non-driving potential is applied to the first control electrode, and the other is applied to the second control electrode, whereby the second control electrode is provided. In an image forming apparatus for selectively adhering a developer to a recording medium conveyed between an electrode and a counter electrode, one of a first control electrode and a second control electrode to which a scanning signal is applied is printed. Fewer electrodes than the other to which the signal is applied An image forming apparatus. 7. A carrier that carries at least one color negatively charged developer and is grounded; a counter electrode disposed to face the carrier and for attracting the developer from the carrier; An electrically insulating substrate having a plurality of through holes disposed between the body and the counter electrode; a first control electrode disposed around the through-hole on the carrier side; and a first control electrode disposed around the through-hole on the counter electrode side. A second control electrode, wherein one of a scanning signal and a printing signal comprising a driving potential and a non-driving potential is applied to the first control electrode, and the other is applied to the second control electrode. (2) In an image forming apparatus for selectively adhering a developer to a recording medium conveyed between a control electrode and a counter electrode, a driving potential of a scanning signal is higher than a ground potential and a non-driving potential of the scanning signal is grounded. Lower than the driving potential of the printing signal An image forming apparatus, wherein the non-drive potential is equal to or higher than the ground potential. 8. A carrier for carrying at least one charged developer of at least one color, a counter electrode disposed opposite to the carrier for attracting the developer from the carrier, and An electrically insulating substrate having a plurality of through holes, a first control electrode disposed around the through-hole on the carrier side, and a second control electrode disposed around the opposite electrode side of the through-hole; And selecting one of the driving potential and the non-driving potential applied to the first control electrode, and selecting one of the driving potential and the non-driving potential applied to the second control electrode. This allows the developer to pass through the through-hole and allows the developer to adhere to the recording medium conveyed between the second control electrode and the counter electrode. One of the non-printing states that prohibit passing In the image forming apparatus-option, the image forming apparatus, wherein said first control electrode and second control electrode insulating film covering, further comprising a conductive member disposed in contact with the insulating film. 9. The image forming apparatus according to claim 8, further comprising a potential adjusting mechanism for applying a predetermined potential via a conductive member to adjust a potential on a surface of said insulating film. 10. When a potential different from a ground potential is applied to the first control electrode or the second control electrode, one end of the conductive member is grounded, and the other end is brought into contact with an insulating film. The image forming apparatus according to claim 8, further comprising a slide mechanism for sliding. 11. The image forming apparatus according to claim 1, wherein the carrier is a cylindrical roller supported by a shaft, and carries a developer on the surface thereof. apparatus. 12. The carrier according to claim 1, further comprising a belt carrying the developer, a pair of rollers for bridging the belt, and a back electrode disposed opposite to the second control electrode with the belt interposed therebetween. The image forming apparatus according to claim 1, wherein: