JP5360551B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation device of direct recording system which can avoid the birth of toner smudge in the non-pictured part of an intermediate record belt 101 while reducing a recording-on voltage Vc-off applied to a fly control electrode 12Y corresponding to the non-pictured part further than before. <P>SOLUTION: While an object equipped with a plurality of A phase and B phase electrodes located in a line along with the surface of a toner supporting sleeve 30Y is used as the sleeve, a conveying control part 91Y which applies a repetition pulse voltage for making the toner hop on surface between two or more A phase electrodes and B phase electrodes to these electrodes is prepared. Irrespective of environment, the difference between a mean voltage Vs of the repetition pulse voltage and a recording-off voltage Vc-off is established to the value which makes the toner hop on the surface of the toner supporting sleeve 30Y and not entering into the through-hole 14Y corresponding to the non-pictured part. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, or a printer that forms an image by a direct recording method.

  As an image forming apparatus that forms an image by a direct recording method, for example, an apparatus described in Patent Document 1 is known. In the direct recording method, the toner is applied to the image forming area of the recording body on which the latent image is not formed without using an indirect electrophotographic process in which the latent image is formed and then the toner is attached to the latent image. A toner image is formed by a direct process of selective deposition. FIG. 1 is a configuration diagram showing a main configuration of a conventional direct recording type image forming apparatus. In the figure, a toner carrying roller 901 as a toner carrying member is disposed in such a posture that its rotation axis extends in the left-right direction in the figure, and is driven to rotate by a driving means (not shown). A substrate 903 having a plurality of through holes 902 is disposed below the toner carrying roller 901 carrying the toner particles T on the surface thereof. Around the through hole 902, a ring-shaped flight control electrode 904 surrounding the hole is formed. In the figure, for the sake of convenience, only one combination of the through-hole 902 and the flight control electrode 904 (hereinafter referred to as “hole-electrode pair”) is shown, but a plurality of combinations are actually provided.

  Below the substrate 903 in the figure, a counter electrode 906 facing the toner carrying roller 901 via the substrate 903, and a recording paper 907 conveyed on the counter electrode 6 in a direction perpendicular to the drawing sheet by a conveying means (not shown). Are arranged. The toner carrying roller 901 carries, for example, negative polarity toner on the surface thereof in a grounded state. When, for example, a positive recording on voltage is applied to the flight control electrode 904 in this state, the toner at the position facing the flight control electrode 904 on the surface of the toner carrying roller 901, or the toner in the vicinity thereof, An electric field from the roller side toward the electrode side acts. By the action of this electric field, the aggregate of toner particles T flies from the toner carrying roller 901 in a dot shape and enters the through hole 902. Then, it continues to fly by being attracted by an electric field formed between the flight control electrode 904 and the counter electrode 906 having a higher potential, and passes through the through hole 902 and adheres to the surface of the recording paper 7. To do. Due to this adhesion, the aggregate of toner particles T records dots.

  In such a direct recording method, it is necessary to individually turn on / off the recording on voltage with respect to the plurality of flight control electrodes 904, and the number of ICs is considerable. For example, in the specification of forming an image with a resolution of 600 [dpi], it is necessary to provide 4960 “hole-electrode pairs” composed of the through-holes 902 and the flight control electrodes 904, and thus 4960 ICs are required. Become. In general, an IC becomes more expensive as its withstand voltage becomes higher, so it is important to keep the value of the recording on voltage as low as possible in the direct recording method. However, in order to form an electric field that can overcome the adhesion force between the toner carrying roller 901 and the toner by mirror image force, van der Waals force, liquid bridging force, etc., the value of the recording on voltage must be at least 500 [V] or more. There is. This has been an obstacle to cost reduction.

  On the other hand, an image forming apparatus that performs development by a so-called hopping development method is conventionally known. In the hopping development method, toner attached to a roller or a magnetic carrier is not used for development, but toner hopped on the surface of the toner carrier is used for development. For example, the image forming apparatus described in Patent Document 2 includes a cylindrical toner carrier having a plurality of hopping electrodes arranged at a predetermined pitch in the circumferential direction. Among the plurality of hopping electrodes, the same A-phase repetitive pulse voltages are applied to the even-numbered arrangement positions, while the same B is applied to the odd-numbered arrangement positions. Apply repetitive pulse voltage of phase. As a result, an alternating electric field is formed between two adjacent hopping electrodes, and the toner is hopped between the electrodes. Then, development is performed by attaching the hopped toner to the latent image on the latent image carrier. In such a hopping development method, the toner that has lost its adhesion to the surface of the toner carrier by hopping is attached to the latent image, and thus cannot be realized in the normal one-component development method or the two-component development method. The low potential development can be realized. For example, toner can be selectively attached to an electrostatic latent image having a potential difference of only a few tens [V] with respect to surrounding non-image portions.

  The present inventors are developing an image forming apparatus that employs both a direct recording method and a hopping development method. In this image forming apparatus, by eliminating the adhesion force of the toner to the surface of the toner carrier by hopping, it is not necessary to form an electric field for passing the toner through the through hole of the substrate so as to overcome the adhesion force. . Therefore, the recording on voltage can be greatly reduced.

  However, it has been found that this image forming apparatus is likely to cause toner contamination on the non-image portion of the recording paper for the reasons described below. In other words, between a plurality of through holes provided in the substrate and the counter electrode facing the substrate, the toner is electrostatically directed toward the counter electrode regardless of whether the toner is allowed to pass through the through hole. An electric field to be moved is formed. For example, it is assumed that the average potential of the repetitive pulse voltage for hopping the negatively charged toner on the surface of the toner carrier is set to 0 [V]. In order to draw the toner hopping with such a repetitive pulse voltage to the "image hole" corresponding to the image portion among the plurality of through holes, the potential of the flight control electrode surrounding the "image hole" Needs to be larger than 0 [V] on the plus side. Therefore, it is assumed that the recording on voltage applied to the flight control electrode surrounding the “image hole” is set to +50 [V]. In order to electrostatically move the toner passed through the “image hole” toward the counter electrode by applying the recording on potential, the toner is electrostatically moved toward the counter electrode between the hole outlet and the counter electrode. An electric field needs to be formed. Therefore, it is assumed that the counter voltage applied to the counter electrode is set to +1000 [V]. On the other hand, in the “non-image hole” corresponding to the non-image portion among the plurality of through holes, it is necessary to push back the toner being hopped from the hole side toward the toner carrier side to prevent the toner from entering. Therefore, the recording off voltage applied to the flight control electrode surrounding the “non-image hole” is set to +200 [V], and the toner during hopping is directed to the surface of the toner carrier having an average potential of 0 [V]. And push it back. At this time, since a counter voltage of +1000 [V] is applied to the counter electrode facing all the flight control electrodes, the toner is also provided between the hole outlet of the “non-image hole” and the counter electrode. Thus, an electric field for electrostatically moving the electrode toward the counter electrode is formed.

  In the conventional general direct recording method, the toner facing the “non-image hole” on the surface of the toner carrier is not allowed to fly from the surface of the toner carrier, but is left attached to the surface. Therefore, the toner did not enter the “non-image hole”. For this reason, even if an electric field is formed between the hole outlet of the “non-image hole” and the counter electrode, the toner is transferred to the non-image hole of the recording paper through the “non-image hole”. It did not adhere to the part. However, in the image forming apparatus under development, since the toner is hopped over the entire surface of the toner carrier, the toner is hopped even in the area where the toner carrier and the “non-image hole” are opposed to each other. For the toner hopped in the area opposite to the “non-image hole”, the toner is directed toward the toner carrier by the electric field between the flight control electrode (applying the recording off voltage) around the “non-image hole” and the toner carrier. Pushing back. However, depending on the environment, it may not be able to push back sufficiently and may enter a “non-image hole”. Specifically, depending on the environment, the charge amount and fluidity of the toner become very large. Then, the toner hopped vigorously on the surface of the toner carrier does not stop in the above-described electric field, but reaches the “non-image hole” by inertia. The toner that has reached the “non-image hole” electrostatically moves to the recording paper on the counter electrode according to the electric field from the hole outlet toward the counter electrode, causing toner contamination.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to avoid the occurrence of toner contamination in the non-image area of the recording member while reducing the recording on-voltage as compared with the prior art. It is an object of the present invention to provide a direct recording type image forming apparatus.

In order to achieve the above object, the invention of claim 1 comprises a combination of a flat substrate, a through hole penetrating the substrate in the thickness direction, and a flight control electrode provided in the vicinity of the through hole. A plurality of substrates, a toner carrier that carries toner on its surface facing the substrate via a predetermined gap, and a surface of the substrate opposite to the surface facing the toner carrier A counter electrode facing through a predetermined gap, a counter voltage applying means for supplying a counter voltage to the counter electrode, and a recording member on which an image is formed by toner adhesion is conveyed on the surface of the counter electrode. A recording on voltage is applied to the transport control electrode and the flight control electrode having the above combination with the image hole which is a through hole at a position corresponding to the image portion of the recording member among the plurality of through holes. On the other hand, multiple through holes A non-image hole that is a through hole at a position corresponding to the non-image portion of the recording member, and a recording voltage applying unit that applies a recording off voltage to the flight control electrode that is in the above combination, In the image forming apparatus for forming an image by electrostatically moving the toner on the surface of the toner carrier toward the counter electrode through the image hole and attaching the toner to the recording member on the counter electrode, the toner carrier A pulse voltage application that uses a plurality of hopping electrodes arranged along the surface and applies a repetitive pulse voltage to the hopping electrodes for hopping the toner on the surface between the hopping electrodes. means provided respectively corresponding to the plurality of the through hole, out of the entire area in the thickness direction at the base, the flying which is arranged in the end position of the toner carrier side Provided with a control electrode only one,
Regardless of the environment, as a value to prevent entry into the toner carrying member surface on hopping toner of the non-image hole at the maximum of the minimum and humid environment in the environment ranges manufacturers to ensure the normal operation The difference between the average potential of the repetitive pulse voltage and the recording off voltage is set to a value that prevents the toner from entering the non-image hole in each of the low temperature and low humidity environments , and the recording off voltage Is set to 0 [V] .
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the average potential of the repetitive pulse voltage is a value between the recording on voltage and the recording off voltage. Is.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the recording on voltage is turned on and off and the recording off voltage is turned on and off with respect to a plurality of the flight control electrodes. It is characterized by that.
According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect, the average potential of the repetitive pulse voltage is 250 [V], the counter voltage is 1250 [V], and the recording is performed. The on-voltage is 300 [V].

In these inventions, by eliminating the adhesive force between the surface of the toner carrier and the toner by hopping the toner, the recording on voltage applied to the flight control electrode of the substrate can be reduced as compared with the prior art.
Even if the toner whose charge amount and fluidity are greatly increased due to environmental fluctuations hops vigorously on the surface of the toner carrier, the difference between the average potential of the repeated pulse voltage and the recording off voltage Since the value prevents entry into the non-image hole, it is possible to avoid the occurrence of toner contamination in the non-image portion of the recording member.

FIG. 6 is a configuration diagram illustrating a main configuration of a conventional direct recording type image forming apparatus. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is a perspective view showing a toner carrying sleeve of an image forming unit for Y in the printer. FIG. 3 is a transverse sectional view showing the toner carrying sleeve. FIG. 3 is a plan development view in which a cylindrical portion of the toner carrying sleeve is developed in a plane. The graph which shows the waveform of the A phase pulse voltage applied to the A phase electrode of the toner carrying sleeve, and the B phase pulse voltage applied to the B phase electrode. The graph which shows the modification of the same waveform. FIG. 3 is an enlarged configuration diagram illustrating a part of an image forming unit for Y and the periphery thereof. FIG. 3 is an enlarged configuration diagram illustrating the toner carrying sleeve and a control board. The graph which shows the relationship between the recording on voltage Vc-on and the recording off voltage Vc-off applied to a flight control electrode. FIG. 3 is an enlarged configuration diagram illustrating an image forming unit for Y of the printer. The perspective view which shows the hopping unit for Y of the printer which concerns on a modification.

Hereinafter, an embodiment of a color printer (hereinafter simply referred to as a printer) which is an image forming apparatus of a direct recording system to which the present invention is applied will be described.
First, the basic configuration of the printer will be described. FIG. 2 is a schematic configuration diagram illustrating the printer according to the embodiment. In this figure, this printer is configured to form an image forming unit 90Y for Y, M, C, and K that forms an image using toners of yellow (Y), magenta (M), cyan (C), and black (K), respectively. , M, C, K, an intermediate recording device 100, a paper feed cassette 120, a registration roller pair 122, a fixing device 130, and the like.

  The image forming units 90Y, 90M, 90C, and 90K are arranged so as to be arranged at a predetermined pitch in the vertical direction, and control substrates 10Y, 10M, 10C, and 10K, and toner carrying sleeves 30Y, 30M, C, K, etc.

  The intermediate recording apparatus 100 is disposed on the right side of the image forming units 90Y, 90M, 90C, 90K in the drawing. An endless intermediate recording belt 101, a driving roller 102, a pressing roller 103, four counter electrode rollers 104Y, 104M, 104C, and 104K, a transfer roller 115, and the like are included. The intermediate recording belt 101 is stretched in a vertically long posture by a driving roller 102 and four counter electrode rollers 104Y, 104M, 104C, and 104K, while the driving roller 102 is rotated counterclockwise in the drawing. It can be moved endlessly in the counterclockwise direction. The front surface (loop outer surface) of the intermediate recording belt 101 sequentially passes through the position facing the image forming units 90Y, 90M, 90C, 90K as the belt endlessly moves. At this time, Y, M, C, and K toner images are sequentially superimposed and recorded. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate recording belt 101.

  The four counter electrode rollers 104Y, 104M, 104C, and 104K of the intermediate recording apparatus 100 are connected to the control substrates 10Y, 10M, and 90K of the image forming units 90Y, 90M, 90C, and 90K via the belt in the loop of the intermediate recording belt 101. It is arranged so as to face C and K. In addition, the transfer roller 115 of the intermediate recording apparatus 100 is disposed outside the loop of the intermediate recording belt 101 and forms a transfer nip by abutting on the belt around the driving roller 102. In this transfer nip, a transfer electric field is formed by a potential difference between the transfer roller 115 to which a positive transfer bias is applied by a power source (not shown) and the drive roller 102.

  The paper feed cassette 120 accommodates a plurality of recording papers P, and a paper feed roller 120a for the uppermost recording paper P is brought into contact therewith. Then, the sheet feeding roller 120 is driven to rotate at a predetermined timing, and the uppermost recording sheet P is sent out toward the sheet feeding path 121. The fed recording paper P is sandwiched between the rollers of the registration roller pair 122 disposed immediately before the transfer nip described above. The registration roller pair 122 sends out the recording paper P sandwiched between the rollers toward the transfer nip at a timing when the recording paper P can be brought into close contact with the four-color superimposed toner image on the intermediate recording belt 101. The four-color superimposed toner image brought into close contact with the recording paper P at the transfer nip is transferred to the recording paper P by the action of the transfer electric field and nip pressure, and becomes a full-color toner image together with the white color of the recording paper P. The recording paper P on which the full-color toner image is formed in this manner is sent from the transfer nip to the fixing device 130, where the full-color toner image is fixed, and then discharged outside the apparatus. The fixing device 130 forms a fixing nip by contact between a heating roller 131 containing a heat source such as a halogen lamp and a pressure roller 132 pressed toward the heating roller 131. When the recording paper P is sandwiched in the fixing nip, the full color toner image is fixed on the surface of the recording paper P by the action of nip pressure or heating.

  FIG. 3 is a perspective view showing the toner carrying sleeve 30Y of the Y image forming section (90Y). FIG. 4 is a cross-sectional view of the toner carrying sleeve 30Y. FIG. 5 is a plan development view in which the cylindrical portion 31Y of the toner carrying sleeve 30Y is developed in a plane. As shown in FIG. 3, the toner carrying sleeve 30Y includes a cylindrical portion 31Y, flanges 36Y and 38Y respectively connected to both end faces in the axial direction thereof, shaft members 37Y and 39Y protruding from the centers of the respective flanges, and the like. doing. A plurality of electrodes 33Y having a shape extending in the roller axis direction are formed on the circumferential surface of the cylindrical portion 31Y so as to be arranged at a predetermined pitch in the circumferential direction (rotation direction). Of these electrodes, every other one arranged in the circumferential direction is an electrically in-phase electrode that is in the same potential state. Specifically, as shown in FIGS. 4 and 5, A-phase electrodes 33aY and B-phase electrodes 33bY as hopping electrodes are alternately arranged in the circumferential direction on the circumferential surface of the cylindrical portion 31Y. ing. The A-phase electrode 33aY extends to one end in the axial direction of the cylindrical portion 31Y, and a metal flange 36Y is connected to one end of the cylindrical portion 31Y (see FIG. 3). The plurality of A-phase electrodes 33aY are electrically connected to each other by the flange 36Y. The B-phase electrode 33bY extends to the other end in the axial direction of the cylindrical portion 31Y, and a metal flange 38Y is connected to the other end of the cylindrical portion 31Y. The plurality of B-phase electrodes 33bY are electrically connected to each other by the flange 38Y.

  The toner carrying sleeve 30Y shown in FIG. 3 is driven to rotate while axial members 37Y and 39Y at both ends in the axial direction are rotatably supported. Then, as shown in the figure, the A-phase pulse voltage is applied to the left flange 36Y in the figure by the conveyance control unit 91Y. This application is performed via a rubbing electrode (not shown) that rubs against the flange 36Y. The A-phase pulse voltage applied to the flange 36Y is guided to the plurality of A-phase electrodes 33aY. In addition, a B-phase pulse voltage is applied to the right flange 38Y in the figure by the conveyance control unit 91Y. This application is performed via a rubbing electrode (not shown) that rubs against the flange 38Y. The B-phase pulse voltage applied to the flange 38Y is guided to the plurality of B-phase electrodes 33bY.

  FIG. 6 is a graph showing waveforms of the A-phase pulse voltage applied to the A-phase electrode 33aY and the B-phase pulse voltage applied to the B-phase electrode 33bY. The A-phase pulse voltage and the B-phase pulse voltage are in opposite phases as shown in the figure, and the average potentials per unit time are the same. A line extending in the horizontal direction at the center position in the waveform of each pulse voltage indicates this average potential. As a result, the A-phase electrode 33aY and the B-phase electrode 33bY have an electric potential having a polarity opposite to that of the toner on average. When such a pulse voltage is applied to each electrode, the Y toner on the surface of the cylindrical portion 31Y in the toner carrying sleeve 30Y reciprocates between the A-phase electrode 33aY and the B-phase electrode 33bY. Repeat hopping. Hereinafter, the state in which the toner repeats hopping on the surface of the toner carrying sleeve 30Y at a predetermined cycle is referred to as flare.

  Note that with the rectangular wave pulse voltage as shown in the figure, the polarity is instantaneously switched, so that a large electrostatic force can be applied to the toner. However, a sinusoidal pulse voltage or a triangular wave pulse voltage may be employed. In addition, a rectangular wave pulse voltage having a frequency f is applied to one of the A-phase electrode 33aY and the B-phase electrode 33bY, while a DC voltage that is an average potential of the pulse voltage is applied to the other. Even so, it is possible to cause a flare phenomenon as in the case of employing a pulse voltage having an opposite phase (FIG. 7).

  The Y toner forming a flare on the peripheral surface of the cylindrical portion 31Y by repeating reciprocating movement by hopping between the A-phase electrode 33aY and the B-phase electrode 33bY on the peripheral surface of the cylindrical portion 31Y is a toner carrying sleeve. By the rotational drive of 30Y, the sheet is conveyed to the Y recording area facing the Y control board 10Y shown in FIG. In the recording area, when it reaches the vicinity of the control board 10Y near the apex of the parabolic hopping locus, it is taken into a through hole (not shown) of the control board 10Y as necessary, and the toner image Contributes to recording.

  As shown in FIG. 4, a surface protective layer 34Y made of an insulating material is provided on the surface of the cylindrical portion 31Y. This surface protective layer 34Y avoids direct contact between the Y toner and the A-phase electrode 33aY or B-phase electrode 33bY, thereby avoiding the occurrence of charge injection from the electrode to the Y toner.

  As the cylindrical base material 32Y of the cylindrical portion 31Y, an insulating film such as SiO2 is formed on a substrate made of an insulating material such as a glass substrate, a resin substrate or a ceramic substrate, or a substrate made of a conductive material such as stainless steel. A substrate made of a deformable material such as a polyimide film can be used.

  The A-phase electrode 33aY and the B-phase electrode 33bY can be created as follows. That is, first, a conductive material such as Al or Ni—Cr is formed on the substrate 32Y in a thickness of 0.1 to 10 [μm], preferably 0.5 to 2.0 [μm]. Are patterned into a required electrode shape by a photolithography technique or the like to obtain each electrode.

  As the surface protective layer 34Y, for example, a layer formed of SiO2, TiO2, TiN, Ta2O5 or the like with a thickness of 0.5 to 10 [μm], preferably 0.5 to 2 [μm] is exemplified. it can. An organic material such as polycarbonate, polyimide, or methyl methacrylate may be applied by thin film printing to a thickness of 0.5 to 10 μm and heat cured.

  FIG. 8 is an enlarged configuration diagram showing a part of the Y image forming unit 90Y and its periphery. The toner carrying sleeve 30Y as a toner carrying member is driven to rotate in the clockwise direction in the figure while hopping the toner on the surface between the A phase electrode and the B phase electrode to form a flare. A control substrate 10Y for Y is disposed opposite to the toner carrying sleeve 30Y with a predetermined gap, and a gap of a distance d is interposed between the sleeve and the sleeve 30Y. Further, above the control board 10Y, the intermediate recording belt 101 moves in the direction of the arrow in the figure, and further above the counter electrode roller 104Y faces the toner carrying sleeve 30Y via the belt and the control board 10Y. ing. Between the toner carrying sleeve 30Y and the control board 10Y, as shown in FIG. 9, the toner on the toner carrying sleeve 30Y hops and approaches the control board 10Y.

  The control substrate 10Y includes an insulating substrate 11Y as a base. In addition, a plurality of through holes 14Y formed in the insulating substrate 11Y and a plurality of flight control electrodes 12Y individually corresponding to the respective through holes 14Y are provided. 8 and 9, only one combination of the through hole 14Y and the flight control electrode 12Y is shown for convenience, but a plurality of combinations are formed on the control board 10Y. The flight control electrode 12Y as the hole vicinity electrode is formed so that one through hole 14Y is positioned inside the ring-shaped loop. The plurality of flight control electrodes are connected to lead parts 15Y made of metal, and these lead parts 15Y are connected to the recording control part 28Y while maintaining insulation from each other.

  The transport control unit 91Y applies the A-phase pulse voltage and the B-phase pulse shown in FIG. 8 to the A-phase electrode and B-phase electrode of the toner carrying sleeve 30Y, so that the toner on the sleeve surface is transferred between the electrodes. Let it hop. Since these pulse voltages all have a duty ratio of 50%, the half potential of the peak-to-peak voltage Vpp becomes the average potential Vs on the sleeve surface. For example, when a pulse voltage having one peak of +150 [V] and the other peak of −150 [V] is used, the average potential Vs is 0 [V]. The frequency f of the pulse voltage is, for example, about 0.5 to 7 [KHz]. The pulse voltage Vpp is preferably about ± 60 to ± 300.

  On the other hand, the flight control electrode 12Y of the control board 10Y is connected to the switching driver 27Y. The switching driver 27Y individually turns on and off the application of the recording on voltage Vc-on and the recording off voltage Vc-off output from the power supply 26Y, and individually controls the plurality of flight control electrodes 12Y. In order to realize on / off, the same number of ICs as the flight control electrodes 12Y are provided.

  FIG. 10 is a graph showing the relationship between the recording on voltage Vc-on and the recording off voltage Vc-off applied to the flight control electrode 12Y. In the figure, a dotted line between the recording on voltage Vc-on and the recording off voltage Vc-off indicates the average potential Vs between the A-phase pulse voltage and the B-phase pulse voltage described above. That is, the average potential Vs is a value between the recording on voltage Vc-on and the recording off voltage Vc-off applied to the flight control electrode 12Y. More specifically, the recording on voltage Vc-on has a value larger than the average potential Vs of the sleeve on the side opposite to the charged polarity of the toner. As a result, among the plurality of flight control electrodes 12Y, the one to which the recording on voltage Vc-on is applied draws the hopping toner on the sleeve surface located above it toward itself. The attracted toner passes through the through hole 14Y, flies toward the counter electrode roller 104K, and lands on the intermediate recording belt 101 on the counter electrode roller 104K to form dots. On the other hand, the recording off voltage Vc-off has a larger value on the charging polarity side of the toner than the average potential Vs of the sleeve. As a result, among the plurality of flight control electrodes 12Y, the one to which the recording off voltage Vc-off is applied repels the hopping toner on the sleeve surface positioned above it.

  The value of the counter bias Vp applied to the counter electrode roller 104K is set according to the distance between the control substrate 10Y and the counter electrode roller. Of course, the counter bias Vp is set to a larger value as the distance increases.

  FIG. 11 is an enlarged configuration diagram illustrating the Y image forming unit (90Y). In FIG. 2, for convenience, the peripheral configuration of the toner carrying sleeve 30Y is omitted, but as shown in FIG. 11, the toner carrying sleeve 30Y is accommodated in the casing 41Y of the hopping unit 40Y. In addition to the toner carrying sleeve 30Y, the hopping unit 40Y includes a first agent storage portion 48Y, a second agent storage portion 46Y, a magnetic brush portion, and the like.

  The first agent accommodating portion 48Y accommodates a first conveying screw 49Y that is rotationally driven in the clockwise direction in the drawing together with a mixture of a magnetic carrier and toner (not shown). Further, the second agent accommodating portion 46Y accommodates the second conveying screw 47Y that is driven to rotate counterclockwise in the drawing together with the mixed agent. Although these agent accommodating parts are mutually partitioned off by the partition wall, a part is mutually connected via a communicating port.

  The first conveying screw 49Y conveys the mixture in the first accommodating portion 48Y from the near side to the far side in the direction orthogonal to the drawing sheet while rotating and stirring the mixture in the first accommodating portion 48Y by its rotational drive. At this time, the toner concentration of the mixture being transported is detected by the toner concentration sensor 50Y fixed to the top plate of the first container 48Y. And the mixed agent conveyed to the edge part vicinity of the back | inner side in the figure enters into the 2nd accommodating part 46Y through the communicating port of a partition wall.

  The second storage section 46Y communicates with a magnetic brush forming section that stores a toner supply roll 42Y, which will be described later. The second transport screw 47Y and the toner supply roll 42Y are parallel to each other in the axial direction through a predetermined gap. Facing each other. The second conveying screw 47Y in the second accommodating portion 46Y conveys the mixture in the second accommodating portion 46Y from the back side to the near side in the drawing while rotating and stirring the mixture in the second accommodating portion 46Y. In this process, a part of the mixture conveyed by the second conveying screw 47Y is pumped up by the cylindrical toner supply sleeve 43Y of the toner supply roll 42Y. Then, as the toner supply sleeve 43Y is driven to rotate counterclockwise in the drawing, the toner supply sleeve 43Y passes through a toner supply region, which will be described later, and then comes off from the surface of the toner supply sleeve 43Y and is returned again into the second housing portion 46Y. . Thereafter, the mixture conveyed to the vicinity of the end on the near side in the figure by the second conveying screw 47Y is returned into the first accommodating part 48Y through the communication port of the partition wall.

  The toner density sensor 50Y described above is formed of a magnetic permeability sensor. The detection result of the magnetic permeability of the mixture by the toner concentration sensor 50Y is sent to a control unit (not shown) as a voltage signal. Since the magnetic permeability of the mixed agent has a correlation with the K toner concentration of the mixed agent, the toner concentration sensor 50Y outputs a voltage having a value corresponding to the toner concentration.

  A control unit (not shown) of the printer includes a CPU (Central Processing Unit) as calculation means, and a RAM (Random Access Memory) and ROM (Read Only Memory) as data storage means. The ROM stores the Vtref for Y, which is the target value of the output voltage from the toner density sensor 50Y. Then, the output voltage value from the toner density sensor 50Y is compared with the Y Vtref in the RAM, and the toner supply device (not shown) is driven for a time corresponding to the comparison result. By this driving, an appropriate amount of toner is supplied into the first container 48Y with respect to the mixture whose toner density has been reduced by toner consumption accompanying image formation. For this reason, the toner concentration of the mixture in the second container 46Y is maintained within a predetermined range.

  The toner supply roll 42Y includes a cylindrical toner supply sleeve 43Y made of a non-magnetic material that is driven to rotate counterclockwise in the drawing, and a magnet roller 44Y that is included so as not to rotate. . The cylindrical toner supply sleeve 43Y is a cylindrical non-magnetic material such as aluminum, brass, stainless steel, or conductive resin. As shown in the figure, the magnet roller 44Y has a plurality of magnetic poles arranged in the rotational direction (N pole, S pole, N pole, S pole, N pole, S pole in order from the 12 o'clock position in the counterclockwise direction). )have. By these magnetic poles, the admixture is adsorbed on the peripheral surface of the toner supply sleeve 43Y, and a magnetic brush that rises along the lines of magnetic force is obtained.

  The mixture pumped up on the surface of the toner supply sleeve 43Y rotates in the counterclockwise direction in the drawing as the toner supply sleeve 43Y rotates. Then, it enters the carrying amount regulating position, which is a position facing the regulating member 45Y that makes its tip end face the surface of the toner supply sleeve 43Y with a predetermined gap. At this time, the carrying amount on the sleeve surface is regulated by passing through the gap between the regulating member 45Y and the sleeve surface.

  On the left side of the toner supply sleeve 43Y in the drawing, the toner carrying sleeve 30Y as a toner carrying body faces the surface of the toner supply sleeve 43Y with a predetermined gap and is driven to rotate counterclockwise in the drawing by a driving means (not shown). Has been. As the toner supply sleeve 43Y rotates, the admixture that has passed through the above-mentioned carrying amount regulation position enters the toner supply area that is the contact position with the toner carrying sleeve 30Y and moves while rubbing the tip of the magnetic brush. . Due to this rubbing and the potential difference between the toner supply sleeve 43Y and the toner carrying sleeve 30Y, the toner in the magnetic brush is supplied onto the surface of the toner carrying sleeve 30Y. Note that a variable bias is applied to the toner supply sleeve 43Y by the bias controller 55Y. When toner is supplied from the toner supply sleeve 43Y to the toner carrying sleeve 30Y, a bias supply unit 55Y applies a toner supply bias to the toner supply sleeve 43Y. Thereby, an electric field for moving the toner from the former to the latter is formed between the toner supply sleeve 43Y and the toner carrying sleeve 30Y. The supply bias may be a DC voltage having the same polarity as the charging polarity of the toner, or may be an AC voltage superimposed on the DC voltage.

  The magnetic brush (mixture) on the toner supply sleeve 43Y that has passed through the toner supply region is conveyed to a position facing the second storage portion 46Y as the sleeve rotates. In the vicinity of this opposed position, no magnetic pole is provided on the magnet roller 44Y, and no magnetic force attracts the mixture to the sleeve surface, so that the mixture separates from the sleeve surface and enters the second housing portion 46Y. Return to. As the magnet roller 44Y, one having more than six magnetic poles may be used instead of the one having six magnetic poles.

  The toner carrying sleeve 30Y carrying the toner supplied from the toner supply sleeve 43Y exposes a part of the peripheral surface from an opening provided in the casing 41Y. This exposed portion faces the control board 10Y.

  The toner supplied onto the surface of the toner carrying sleeve 30Y is hopped on the surface of the toner carrying sleeve 30Y, and from the toner supply area toward the area facing the control substrate 10Y as the toner carrying sleeve 30Y rotates. Be transported. Then, in the area facing the control substrate 10Y, it is taken into the through hole of the control substrate 10Y as necessary, and contributes to dot recording. The Y image forming section (90Y) has been described in detail, but the other color image forming sections (90M, C, K) have the same configuration as that for Y.

  In the printer having the above-described configuration, unlike the image forming apparatus described in Patent Document 1, the toner attached to the surface of the toner carrier is taken into the through hole of the control board. The toner hopped on the surface is taken into the through hole of the control board. This can reduce the cost of the recording control unit (for example, 28Y) that controls the voltage applied to the flight control electrode of the control board. Specifically, the recording on voltage Vc-on and the recording off voltage Vc-off with respect to the plurality of flight control electrodes need to be individually performed by a dedicated IC. The number of ICs is considerable. For example, in the specification for forming an image with a resolution of 600 [dpi], it is necessary to provide 4960 ICs. In general, an IC is expensive because it requires a chip area as its withstand voltage increases. In the direct recording method, how to lower the control voltage is an important factor in reducing the cost of the recording control unit. However, in the image forming apparatus described in Patent Document 1, it is necessary to use an IC having a withstand voltage of at least 500 [V] or more. This is for the reason explained below. That is, the toner and the toner-carrying sleeve have an adhesion force that attracts each other by mirror image force, van der Waals force, liquid bridging force, and the like. To create an electric field that can overcome this, at least absolutely A bias having a value of 500 [V] or more must be applied to the flight control electrode. On the other hand, in this printer, the toner is hopped on the surface of the toner carrying sleeve 30Y to eliminate the adhesive force between the sleeve surface and the toner, so a bias of about several tens [V] is applied to the flight control electrode. It is possible to control the on / off of recording by applying to the above. That is, the above-described IC may have a withstand voltage of about 100 [V].

  Further, in this printer, by hopping the toner on the surface of the toner carrying sleeve 30Y, it is possible to promote the frictional charging of the toner and suppress the occurrence of insufficient toner charge amount. Specifically, when the toner is repeatedly hopped on the surface of the toner carrying sleeve 30Y, the toner is repeatedly collided against the surface of the sleeve, and the frictional charging of the toner can be promoted.

Next, experiments conducted by the present inventors will be described.
The inventors prepared a printer testing machine having the same configuration as the printer according to the embodiment. Conditions in the image forming unit for each color in this printer are as follows.
A gap between the toner carrying sleeve and the control substrate: 200 [μm]
・ Gap between the control board and the intermediate recording belt: 300 [μm]

An experiment was conducted to examine the difference in toner contamination between the case where flare was not formed and the case where the flare was formed, using only the image forming portion for K among the image forming portions for each color in the printer tester. Specifically, first, the relationship between the recording off voltage and the toner contamination was examined under the condition that no flare was formed. Specifically, all the flight control of the control board is performed with the K toner not being hopped on the surface of the toner carrying sleeve (a pulse voltage and a B phase pulse voltage are not applied) and the intermediate recording belt 101 is stopped. A recording off voltage Vc-off was applied to the electrodes for a predetermined time. Thereafter, the toner adhering to the surface of the intermediate recording belt 101 was transferred to an adhesive tape, and the presence or absence of toner contamination was evaluated based on the result of observing the amount of toner adhering to the tape. Such evaluation was performed under four conditions of recording off voltage Vc-off of −50 [V], −100 [V], −150 [V], and −200 [V], respectively. The counter voltage Vp applied to the counter electrode roller 104K was constant at 1000 [V]. Next, the same experiment was performed with the K toner hopped on the surface of the toner carrying sleeve (A pulse voltage and B phase pulse voltage applied) and the intermediate recording belt 101 stopped. The A-phase pulse voltage and B-phase pulse voltage applied to the electrode of the toner carrying sleeve are rectangular waves having a peak-to-peak voltage of 1 [kV] and a frequency f of 1 [kHz], and having phases opposite to each other. The thing was adopted. The results of this experiment are shown in Table 1 below.

  As shown in Table 1, when flare is not formed with the toner on the surface of the toner carrying sleeve, the toner can be used even if a recording off voltage Vc-off having a very small value of −50 [V] is adopted. Dirt was not caused. On the other hand, when flare was formed, it was found that toner smearing would occur unless the recording off voltage Vc-off was increased to -200 [V]. From this result, it was found that in this printer that forms flare, toner contamination is more likely to occur than in a conventional image forming apparatus that did not form flare. In addition, when flare is formed, toner contamination occurs unless the recording off voltage Vc-off is increased to some extent. That is, even if an electric field is formed between the toner carrying sleeve and the flight control electrode to push the toner back from the flight control electrode side to the sleeve side, depending on the strength of the electric field, the hopped toner may be It was found that it would enter.

  In view of this experiment, the present inventors set the recording off voltage Vc-off in the printer tester to −200 [V] and perform various experiments over a long period of time. However, it has been found that depending on time and circumstances, toner smearing may occur in the non-image area of the intermediate recording belt 101 even under the condition of the recording off voltage Vc-off of −200 [V]. This is thought to be because the charge amount and fluidity of the toner become excessive depending on the environment.

  Therefore, regardless of the environment, the toner hopped on the surface of the toner carrying sleeve can be prevented from entering the “non-image hole” in the center of the flight control electrode to which the recording off voltage Vc-off is applied. I checked the value. Specifically, first, the compensation environment of the printer tester was set. This compensation environment compensates the user that normal image formation is performed as long as the apparatus is used in the environment range indicated by the compensation environment. This compensation environment (appropriate environment range) is generally specified in the instruction manual of a commercially available image forming apparatus. After setting the compensation environment of the printer testing machine, next, after creating the maximum hot and humid environment conditions in the compensation environment, the minimum value of the recording off voltage Vc-off that can avoid toner contamination is experimentally determined. Examined. Thereafter, the minimum low-temperature and low-humidity conditions in the compensation environment were created in the laboratory, and similarly, the minimum value of the recording off voltage Vc-off was examined by experiment. Of these minimum values, the larger one is set to a value at which the hopped toner can be prevented from entering the “non-image hole” regardless of the environment. As a result of the experiment, it was found that the value was −250 [V].

In view of this experimental result, in the printer of the embodiment, as shown in Table 2 below, the recording off voltage Vc− applied to the flight control electrode surrounding the “non-image hole” in each color image forming unit. The value of off is set to −250 [V]. In Table 2, Vs represents an average potential of the A-phase pulse voltage and the B-phase pulse voltage applied to the electrode of the toner carrying sleeve. Vp represents the counter voltage applied to the counter electrode roller. Vc-on represents a recording on voltage applied to the flight control electrode surrounding the “image hole”.

  In this printer having such a configuration, the control board flying control is performed by hopping the toner on the surface of the toner carrying sleeve in each color image forming unit to eliminate the adhesion between the surface of the toner carrying sleeve and the toner. The recording on voltage applied to the electrode can be reduced as compared with the conventional case. Further, by preventing the toner hopped on the surface of the toner carrying sleeve from entering the “non-image hole” regardless of the environment, it is possible to avoid the occurrence of toner contamination in the non-image portion of the intermediate recording belt 101. it can.

Next, a printer according to an example in which a more characteristic configuration is added to the printer according to the embodiment will be described.
In the example shown in Table 2, the recording off voltage Vc-off and the recording on voltage Vc-on have opposite polarities. In such a setting, for each of the plurality of flight control electrodes, an IC for turning on / off the negative polarity recording off voltage Vc-off and an IC for turning on / off the positive polarity recording on voltage Vc-on. Both are needed.

Therefore, in the printer according to the embodiment, the same potential difference as that between the various voltages shown in Table 2 is secured, and the average potential Vs and the counter voltage are set to values that can set the recording off voltage to 0 [V]. Vp, recording off voltage Vc-off, and recording on voltage Vc-on are set. Specifically, various potential differences in Table 2 are as follows.
The potential difference between the average potential Vs and the counter voltage Vp = 1000 [V]
The potential difference between the average potential Vs and the recording off voltage Vc-off = 250 [V]
The potential difference between the average potential Vs and the recording on voltage Vc-on = 50 [V]
The potential difference between the recording off voltage Vc-off and the recording on voltage Vc-on = 300 [V]

In order to set the recording off voltage Vc-off to 0 [V] while securing the same potential difference as these potential differences, as shown in the following Table 3, various voltages are increased by 250 [V] each. What is necessary is just to shift to the polarity side. Thus, the recording off voltage Vc-off can be set to 0 [V] while exhibiting the same function as in Table 2.

  Therefore, in the printer according to the embodiment, the same voltage condition as that shown in Table 3 is set as the voltage condition in the image forming unit for each color.

Next, a modified example of the printer according to the embodiment will be described.
FIG. 12 is an enlarged configuration diagram showing a Y hopping unit 40Y in a printer according to a modification. This hopping unit 40Y contains toner itself instead of containing a mixture of toner and magnetic carrier. The toner contained in the toner containing portion is frictionally charged by interposing the toner between the roller portion made of an elastic material of the rotating toner supply roller 52Y and the charging roller 53Y rotating while contacting the toner. The toner is pumped up on the surface of the toner supply roller 52Y. The pumped toner is transported to a region facing the toner carrying sleeve 30Y as the toner supply roller 52Y rotates, after the layer thickness is regulated by the regulating member 51Y that is in contact with the toner supply roller 52Y.

  During a print job, a supply bias is applied to the toner supply roller 52Y by the bias controller 55Y. This supply bias is a bias having a larger value on the side opposite to the charging polarity of the toner than the average potential Vs of the pulse voltage applied to the A-phase electrode and B-phase electrode of the toner carrying sleeve 30Y. Therefore, an electric field for moving the toner from the toner supply roller 52Y side to the sleeve side is formed between the toner supply roller 52Y and the toner carrying sleeve 30Y. The toner on the surface of the toner supply roller 52Y is transferred from the roller surface to the sleeve surface by the action of the electric field. On the surface of the toner carrying sleeve 30Y, as already described, flare due to toner hopping is formed. Part of the toner forming the flare is taken into the through hole of the control substrate 10Y and contributes to the formation of dots.

  The toner that has not been taken into the through hole of the control board 10Y in the region facing the control board 10Y reaches the inside of the casing as the toner carrying sleeve 30Y rotates, and then the surface of the toner carrying sleeve 30Y is collected by a collecting means (not shown). Recovered from. The collected toner is again stored in the toner container.

  In such a configuration, the structure of the hopping unit 40Y can be simplified as compared with the embodiment.

  As described above, in the printer according to the embodiment, since the recording off voltage Vc-off is set to 0 [V], values having opposite polarities are set as the recording off voltage Vc-off and the recording on voltage Vc-on. Compared to the case, the number of ICs for turning on / off the voltage to the flight control electrode can be halved.

10Y: Control board (board)
11Y: Insulating substrate (base)
12Y: Flight control electrode (near hole electrode)
14Y: Through hole 26Y: Power supply (part of recording voltage applying means)
27Y: Switching driver (part of recording voltage applying means)
30Y: Toner carrying sleeve (toner carrier)
914Y: Conveyance control unit (pulse voltage application means)
100: Intermediate recording apparatus (conveying means)
101: Intermediate recording belt (recording member)
104Y, M, C, K: counter electrode roller (counter electrode)
116: Counter power supply (counter voltage applying means)

Japanese Patent Laid-Open No. 10-810 JP 2007-133387 A

Claims (4)

A substrate having a flat base, a plurality of through-holes penetrating the base in the thickness direction, and a plurality of combinations of flight control electrodes provided in the vicinity of the through-hole;
A toner carrier that carries toner on its surface facing the substrate with a predetermined gap therebetween;
A counter electrode opposed to a surface of the substrate opposite to the surface facing the toner carrier via a predetermined gap;
A counter voltage applying means for supplying a counter voltage to the counter electrode;
Conveying means for conveying a recording member on which an image is formed by adhesion of toner on the surface of the counter electrode;
Among the plurality of through holes, a recording on voltage is applied to the flight control electrode having the above combination with an image hole that is a through hole at a position corresponding to the image portion of the recording member. Recording voltage applying means for applying a recording off voltage to the flight control electrode in combination with the non-image hole which is a through hole in a position corresponding to the non-image portion of the recording member And
In the image forming apparatus for forming an image by electrostatically moving the toner on the surface of the toner carrier toward the counter electrode through the image hole and attaching the toner to a recording member on the counter electrode.
As the toner carrier, a toner carrier having a plurality of hopping electrodes arranged along the surface thereof is used.
Providing a pulse voltage applying means for applying a repetitive pulse voltage for hopping the toner on the surface between the hopping electrodes to the hopping electrodes ;
In correspondence with each of the plurality of through-holes, only one flight control electrode disposed at the end position on the toner carrier side in the entire thickness direction of the base is provided,
Regardless of the environment, as a value to prevent entry into the toner carrying member surface on hopping toner of the non-image hole at the maximum of the minimum and humid environment in the environment ranges manufacturers to ensure the normal operation Set the difference between the average potential of the repetitive pulse voltage and the recording off voltage to a value that prevents the toner from entering the non-image hole in each of the low-temperature and low-humidity environments ,
An image forming apparatus characterized in that the recording off voltage is set to 0 [V] .   The image forming apparatus according to claim 1,
An image forming apparatus, wherein an average potential of the repetitive pulse voltage is a value between the recording on voltage and the recording off voltage.   The image forming apparatus according to claim 2.
An image forming apparatus characterized in that on / off of the recording on voltage and on / off of the recording off voltage with respect to a plurality of the flight control electrodes are respectively performed by dedicated ICs.   The image forming apparatus according to claim 3,
The average potential of the repetitive pulse voltage is 250 [V],
The counter voltage is 1250 [V],
An image forming apparatus wherein the recording on voltage is 300 [V].

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