JPH05104773A - Electrostatic recording apparatus - Google Patents

Abstract

PURPOSE:To stably form a good recording image of high resolving power not having image inferiority such as density irregularity over a long period of time by certainly preventing the generation of the immobile layer of a developer in a developer feed passage. CONSTITUTION:Two sets of coil parts 16a, 16B are alternately arranged along a developer feed passage in parallel and a switch 17 changing over the connection of the conductors 16aA, 16aB respectively forming both coil parts is interposed between coil parts 16*A (i-1), 16*B (i-1), 16A (i-2)... on an upstream side and coil parts 16Bi, 16Ai, 16*B (i+1)... on a downstream side so as to hold a recording part W between the coil parts. By changing over the connection from (a) to (b) by operating the switch at the time of non- recording, only the feed direction of a developer on the upstream side of the recording part W can be reversed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic recording apparatus that transfers a developer, which is conveyed along a predetermined path, to a recording medium according to recording information to form a recorded image.

[0002]

2. Description of the Related Art Conventionally, a multi-stylus printer is well known as one of electrostatic recording devices.
In this multi-stylus printer, a large number of needle-shaped recording electrodes are arranged in the main scanning direction at equal minute intervals to form a recording head, and a voltage is selectively applied to each needle-shaped electrode according to a recording signal to print on a sheet. It directly discharges to form an electrostatic latent image. In this case, special paper coated with a high electric resistance agent is used so that the electric charge can be easily and stably held on the paper. However, such a special paper is not preferable as a paper for office work because it has a poor writing property with a pencil or a pen and has a problem of storability because it deteriorates depending on environmental conditions such as humidity.

If the distance between the tip of the needle-shaped electrode and the surface of the paper is large, the discharge electric field spreads and the dots formed become large, making it difficult to obtain a high-resolution recorded image. For that reason,
A gap material is provided on the paper surface, and the gap material and the tip of the needle-shaped electrode are brought into sliding contact with each other to secure a minute gap. However, according to this method, there is a problem that the tip of the needle-shaped electrode is worn.

Therefore, after forming a toner image on a drum-shaped intermediate recording medium, as a method in which plain paper can be used and a minute gap with respect to the recording medium can be accurately ensured without wearing the tip of the recording electrode. A method is used in which the toner image is transferred onto the sheet of the final recording medium.
According to this method, there is a drawback that the recording apparatus becomes large in size because the intermediate recording medium is used. In order to solve this drawback, there has been proposed a method of forming a toner image by circulating the developer along a predetermined path and transferring the toner onto the intermediate recording medium according to the recording information. That is, the structure is such that recording and development are performed simultaneously, and the size of the recording apparatus is reduced.

However, in the above-mentioned circulation path of the developer, there are usually some places where the developer easily stays, and the so-called immobile layer is formed by the staying developer adhering to the places. is there. When the immobile layer is formed on the developer transport path,
The developer is not transported smoothly, and the triboelectric charge of the developer is insufficient, which causes image defects such as uneven density.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art and is capable of stably forming a high-resolution recorded image on a plain paper without image defects such as density unevenness. An object is to provide an electrostatic recording device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention is directed to a developer carrying member whose surface serves as a developer carrying path, and a developer carrying member for carrying a magnetic developer along the surface of the developer carrying member. Means, a plurality of recording electrodes arranged in parallel at predetermined intervals in a width direction perpendicular to the developer carrying direction on the surface of the developer carrying member, and a plurality of recording electrodes arranged in parallel according to input recording information to the recording electrodes. The developer transporting means has a recording means composed of an electrode driving circuit for outputting a recording voltage, and a cylindrical electrode arranged to face the recording electrode with a predetermined gap, and the developer carrying means is a base formed of a magnetic material. Is disposed along the back surface of the developer carrying member, and a plurality of recessed grooves are formed to extend in the width direction on the surface of the substrate facing the back surface of the developer carrying member. Laying a plurality of conducting wires along the width direction, A coil portion is formed, the coil portions are divided into m groups, and the coil portions of each group are arranged at intervals of (m-1), and the coil portions belong to the same group among the coil portions. Applies a current with a repetitive waveform so that the directions of the excited magnetic poles are alternately reversed, and the adjacent m coils belonging to different groups are sequentially shifted in phase in the order of π / m. By applying an electric current having a repetitive waveform, a traveling wave magnetic field that advances along the surface of the developer carrying member is formed to convey the magnetic developer in a predetermined forward direction, and the recording electrode causes the cylinder to move. In the electrostatic recording apparatus for forming a recorded image by selectively transferring the magnetic developer conveyed in the recording portion close to the electrode peripheral surface to the cylindrical electrode peripheral surface according to the recording voltage, the recording voltage Is applied to the recording electrode during recording. When the image agent is conveyed in the forward direction and the recording voltage is not applied to the recording electrodes, the developer is conveyed in a direction opposite to the forward direction on the upstream side of the forward direction of the recording section. The essential point is to provide a developer transport control means for transporting the developer in the forward direction on the downstream side of the recording section.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in FIGS. FIG. 1 is a schematic sectional view showing the overall configuration of a recording apparatus as an embodiment of the present invention. In the figure, reference numeral 1 is a paper feed cassette in which plain papers P are stacked and housed, and is attached to the side of the machine so as to be freely inserted and removed. A paper feed roller 1a is disposed above the leading end of the inserted paper feed cassette 1 so as to be rotatable in the arrow direction. In front of the paper feed roller 1a, a paper carry-in path defined by upper and lower transport guide plates 2a and 2b made of an insulating member is formed. A standby roll pair 3 is arranged in the sheet carrying-in path, and after temporarily stopping the progress of the sheet P fed by the sheet feeding roller 1a to adjust the conveying posture, the image transfer unit T on the downstream side is provided. The sheet is re-fed so as to be synchronized with the arrival timing of the recorded image described later.

At the image transfer portion T on the downstream side of the standby roll pair 3, a transfer charger 4 is arranged so as to face a cylindrical electrode 5 which also serves as an image carrier. In this example, the cylindrical electrode 5 is driven and rotated in the counterclockwise direction indicated by the arrow a. In this cylindrical electrode 5,
In the case of this example, since a developer having a negative (-) triboelectrification polarity is used as will be described later, a bias power supply 5a capable of applying a negative bias voltage and applying a bias voltage of -30 to -40V. Are connected. A recording image forming unit U, which will be described later, is installed opposite to the peripheral surface on the opposite side of the cylindrical electrode 5. With this recording image forming unit U, the cylindrical electrode 5
A toner recording image is formed on the surface, and as the cylindrical electrode 5 rotates, the toner recording image is conveyed to the image transfer portion T and transferred onto the sheet that is re-fed. The configuration of the recording image forming unit U will be described later in detail.

On the downstream side of the image transfer section T, a separation claw 6 is arranged with its tip pressed against the peripheral surface of the cylindrical electrode. And
On the downstream side of the separating claw 6, an air suction type conveyor belt 7 is stretched in the horizontal direction, and after the transfer of the recorded image is completed, the separating claw 6 sucks the back surface of the sheet separated from the peripheral surface of the cylindrical electrode 5. And the fixing device 8 provided in front of it
Transport it to. The fixing device 8 is composed of a heating roll 8a and a pressure contact roll 8b, and heat-fixes the toner image when the paper is sandwiched and conveyed between the rolls. The fixed sheet is discharged and stacked on the discharge tray 10 from the discharge port 9 in a face-down state with the image side facing down.

As described above, in the recording apparatus of this example,
Since the entire sheet transport path from sheet feeding to sheet ejection is formed in a substantially straight shape, the sheet passing operation is generally smooth, and sheet defects such as image defects and jams are unlikely to occur.
In addition, there is an advantage that a face-down sheet discharge state that does not require page alignment, which is preferable for the recording apparatus, can be obtained by the straight sheet passage.

The detailed structure of the recording image forming unit U will be described below. The recording image forming unit U generally includes a stirring roll 12 and a supply roll 13 which are rotatably driven at the bottom of a unit container 11 that stores a developer.
A recording unit Uw, in which the image recording means and the developer conveying means are integrated, is arranged such that the recording head portion is positioned in the opening 11a of the container 11 opened toward the peripheral surface of the cylindrical electrode 5. In this example, as the developer, a one-component developer containing at least an insulating resin, magnetic fine powder and colorant particles, and an insulating magnetic toner having a negative (−) triboelectric charging property is used. As the developer, a two-component developer in which a magnetic carrier and an insulating toner are mixed in a predetermined ratio can also be used.

FIG. 2 is a schematic sectional view showing the recording unit Uw and its peripheral structure. Recording unit Uw of this example
Is an outer cover member 1 as a developer carrying member whose surface serves as a conveyance path for the magnetic toner d in a region excluding a part of an outer peripheral surface of a base body 14 having an elliptical cross section and extending in a direction perpendicular to the paper surface.
5 is coated. The base 14 is made of a high magnetic permeability member such as iron, nickel and permalloy, and the outer cover member 15 is made of a non-magnetic material. A large number of concave grooves 14a having a V-shaped cross section are formed on the peripheral surface of the base 14 covered with the jacket member 15.
Are formed in parallel at equal intervals along the longitudinal direction of the substrate (direction perpendicular to the plane of the drawing). The length of each recess groove 14a is
It is set to be longer than the width of the conveyance path set on the peripheral surface of the outer cover member 15.

A conductor wire 16a is embedded in each groove 14a to form a coil portion 16 which constitutes an exciting coil. The coil portion 16 is divided into m groups of A, B, ... M, and the coil portions of the same group are arranged every (m-1). In the illustrated example, the (i-1) th coil unit 16 of the A group
* B to M groups of i-th coil portions 16Bi ... 16Mi are arranged between A (i-1) and the i-th coil portion 16Ai. In this case, the coil portions 16Bi ... 16Mi are arranged in the order of 16M, ... 16B along the forward direction (B) of the magnetic toner described later.

In the same group, a pair of adjoining coil sections with another group of (m-1) coil sections 16 in between, for example, the A group of coil sections 16Ai and 16 * A (i-1) are the same conductor. 16a is formed by winding a plurality of (m-1) pairs of recessed grooves 14a, 14a in a predetermined direction many times. Therefore,
In the same group, (m-1) coil units 16 of another group are placed, and the running directions (winding directions) of the conductors in a pair of adjacent coil units are opposite to each other. For example, coil part 1
In the present example, if the conductor running direction of 6Ai is perpendicular to the paper surface and faces up, the conductor running direction of the coil portion 16 * A (i-1) is perpendicular to the paper surface and faces backward. In addition, "*" of coil part 16 * A (i-1)
Is the coil portion 16 in which the running direction of the conductor 16a is, for example, unmarked.
It is the opposite of Ai, that is, in this example, it is perpendicular to the paper surface and faces down.

With respect to the coil portion 16 constructed as described above,
As a current with a repetitive waveform, π / m
The m kinds of sine wave currents whose phases are sequentially shifted are applied. In this case, for each of the A, B, ... M coil portions 16, π / m
Sine wave current in the direction in which the phase gradually lags
Energize in the order of arrangement along (b). That is, coil section 16Ai ... iAi = Isin (ωt) coil section 16Bi ... iBi = Isin (ωt + π / m) coil section 16Ci ... iCi = Isin (ωt + 2π / m) coil section 16Mi ... iMi = Isin [ωt + (m-1) π /
m] are energized respectively. As a result, the coil portion 16 * A (i-1) ...
... 16 * M (i-1) has a coil portion 16 * A (i-1) ... iA (i-1) =-iAi = -Isin (ω
t) Coil portion 16 * B (i-1) ... iB (i-1) =-iBi = -Isin (ω
t + π / m) Coil part 16 * C (i-1) ... iC (i-1) =-iCi = -Isin (ω
t + 2π / m) Coil portion 16 * M (i-1) ... iM (i-1) =-iMi = -Isin [ω
t + (m-1) π / m], each antiphase current is applied.

Now, consider a case where m = 2 and the coil portion 16 is divided into two groups. In this case, the coil unit 16 of group A
As shown in FIG. 3, π / 2 for the coil portions 16B of the A and B groups.
Two types (two phases) of sine wave currents iA and iB iA = Isin (ωt) ………… (1) iB = Isin (ωt + π / 2) …… (2) Energize.

By supplying a sinusoidal current to the two sets of coil portions 16 as described above, a magnetic field corresponding to the supplied current as shown in FIG. 4 is excited on the peripheral surface of the substrate 14. FIG. 4 is a graph showing the change over time in the excitation magnetic field distribution curve on the surface of the jacket member 15. In the graph, the vertical axis represents the component (radial component) Hr of the exciting magnetic field in the direction perpendicular to the peripheral surface of the base body 14, and the horizontal axis represents the position on the peripheral surface of the base body 14. It should be noted that T is the period of the sine wave current that is conducted. In the present example, as described above, the running directions of the conductors in the coil portions 16 (for example, 16Ai and 16 * A (i + 1)) of each set in a continuous order are reversed. Therefore, when sinusoidal currents of the same phase are passed through the coil portions 16 of the same set, the directions of the magnetic fields excited by the consecutive coil portions 16 are opposite to each other. As a result, the distribution curve of the magnetic field formed on the peripheral surface of the substrate 14 also has a waveform corresponding to the sinusoidal current as shown in FIG. Since this magnetic field changes in the cycle T like the sinusoidal current, as a result, a traveling wave magnetic field that advances in the cycle T in the direction of (c) in the figure is formed.
That is, as shown in FIG.
The traveling wave magnetic field formed on the surface travels in the counterclockwise direction (a) along the surface of the jacket member 15 at a predetermined speed. As a result, the magnetic toner d can be transported in the clockwise direction (b) opposite to the traveling direction (a) of the traveling wave magnetic field.
In this case, the magnetic toner d is conveyed while forming the ears of the toner corresponding to the magnetic force lines of the traveling wave magnetic field.

The transport speed of the magnetic toner d is based on the traveling speed of the traveling wave magnetic field. The traveling speed SH of the traveling wave magnetic field is: SH = G · f [m / s] where G: distance between the coil portions 16Ai and 16 * A (i + 1) on the surface of the jacket member f: energization This is the frequency of the current, which is the same as the frequency of the traveling wave magnetic field, that is, the transport speed of the magnetic toner d is proportional to the frequency f of the current flowing through the coil portion 16 and the coil portion spacing G. The coil portion spacing G is G = π · Ds ÷ (Vc / 2m) [m] where Vc: number of coils Ds: sleeve diameter [m] m: number of current phases. Therefore, the traveling speed SH of the traveling wave magnetic field is SH = (2π · Ds · m · f) / Vc [m / s]. In this example, since two-phase currents are passed, the traveling speed SH of the traveling wave magnetic field is SH = (4π · Ds · f) / Vc [m / s].

Further, the layer thickness of the magnetic toner d to be conveyed is first a magnitude proportional to the magnitude of the current flowing through the coil portion 16, that is, the current peak value I in the above equation (1) to a certain extent. However, finally, the toner layer thickness regulating member 18, which will be described later, regulates the thickness to a desired thickness. In the recording portion W, in order to stably form a good recording image with sufficient density and without causing image defects such as background stain, the toner thin layer formed by the toner layer thickness regulating member 18 is more uniformly recorded at the recording position. Transporting to W is required. In order to uniformly convey the thin toner layer, the interval between peaks (corresponding to the wavelength) in the waveform of the traveling wave magnetic field shown in FIG. 4 is shortened, and the waveform itself is converted into a sin waveform as shown in FIG. Just bring it closer.

To shorten the peak interval of the traveling wave magnetic field,
The number of magnetic poles should be increased. The relationship of P = Vc / m (3) holds between the number of magnetic poles P, the number of coils 4, Vc, and the number of phases of the energized current, m. Therefore, if the number of phases m of the current is constant, the number of poles P is increased and the peak interval of the traveling wave magnetic field is shortened by increasing the number of coils Vc. Correspondingly, the peak interval of the toner thin layer conveyed on the outer cover member 15 is also narrowed, and the magnetic toner can be more uniformly conveyed to the recording portion W.

As shown in FIG. 5 which is a schematic plan view of the toner conveying path, the coil portion 16Bi is disposed downstream of the recording portion W with respect to the toner conveying direction (b). , 16
Ai, 16 * B (i + 1), ... And the coil parts 16 * A (i-1), 16 * B (i-1), 16A (i-2), ... Between the two lead wires 1 forming the coil portion 16 of each set A, B between
A switch 17 for switching the connection between 6aA and 16aB is provided. By operating this connection changeover switch 17, the arrangement of the coil portions 16 of each set can be converted between the upstream side and the downstream side of the recording portion W. That is, [a] of FIG.
When the conductors 16a are connected in parallel as shown in FIG.
16B is arranged, but when the switch 17 is switched to the cross connection as shown in FIG. 8B, the same B group of coil parts 16 * B is sandwiched on both sides of the switching part (recording part W).
(i-1) and 16Bi are located, and the coil portion 16A * (i-1) of the A group and the coil portion 16Ai are the two coil portions 16 * B (i of the B group.
-1), 16Bi is placed. That is, the arrangement of the set of the coil portions 16 on the upstream side is in the order of A, B, A, B along the toner transport direction (b), and the arrangement of the downstream side is B, A, B, A.
It has been switched in the reverse order of.

In FIG. 5, the switch 17 is divided into parts [a].
When the parallel connection shown in FIG. 6 is switched to the cross connection shown in FIG. 6B, only the traveling direction of the traveling wave magnetic field in the toner transport path upstream of the recording portion W is selectively changed from the arrow (a) to the arrow (b). The direction can be switched. The reason is,
It is as follows.

Now, the coil portion 16A on the downstream side of the recording portion W
The respective currents iAi and iBi flowing through i and 16Bi are expressed as iAi = Isin (ωt) iBi = Isin (ωt + π / 2) from the above equations (1) and (2), respectively. A (i-1), 16 * B (i-1)
The currents whose phases are shifted by π respectively flow in the current i
A (i-1) and iB (i-1) are iA (i-1) = Isin (ωt + π) iB (i-1) = Isin (ωt + 3π / 2).

In the case of the cross connection shown in FIG. 5B, the four coil portions 16 sandwiching the recording portion W are 16 * A (i) from the upstream side.
-1), 16 * B (i-1), 16Bi, 16Ai.
These four coil parts 16 * A (i-1), 16 * B (i-1), 16
Bi, each current flowing through 16Ai iA (i-1), iB (i-1), iBi,
iAi is iA (i-1) = Isin (ωt + π) iB (i-1) = Isin (ωt + 3π / 2) iBi = Isin (ωt + π / 2) iAi = Isin (ωt). On the other hand, in the case of the parallel connection shown in FIG. 5A, the four coil portions are 16 * B (i-1), 16 * A.
(i-1), 16Bi, 16Ai are arranged in this order, and the respective currents iB (i-1), iA (i-1), iBi, iAi flowing through them are iB (i-1) = Isin (ωt + 3π / 2 ) IA (i-1) = Isin (ωt + π) iBi = Isin (ωt + π / 2) iAi = Isin (ωt) As can be seen, in the case of parallel connection, the phase of the current flowing through each coil advances by π / 2 in the direction opposite to the toner transport direction (b), whereas in the case of cross connection,
The downstream and upstream sides of the recording section W are in opposite phase advance directions.

Since the traveling wave magnetic field excited by each coil portion 16 travels in the same direction as the traveling direction of the current phase, in the case of parallel connection, as shown in FIG. The traveling wave magnetic field travels in the direction of arrow (a) over the entire stroke,
The magnetic toner is conveyed in the arrow (B) direction. On the other hand, in the case of the cross connection, as shown in FIG. 6B, the traveling wave magnetic field excited by the downstream coil portions 16Bi, 16Ai, .. It is conveyed in the direction of the arrow (b), but on the upstream side the coil parts 16 * A (i-1), 16 *
The traveling wave magnetic field excited by B (i-1), ...
And the magnetic toner is conveyed in the direction of arrow (a). In the case where three or more m coil units are provided, in order to switch the toner transport direction between the upstream side and the downstream side of the recording unit W in the same manner, A, B, C, and …
, M, recording sections W, M, ..., C, B, and A may be provided with a switch capable of switching connection of m conductors so that the coil sections are arranged in the order.

Returning to FIG. 2, in this example, the base body 14 is divided into two pieces that can be brought into contact with and separated from each other, and the internal space S is formed with the divided base bodies 14A and 14B joined together. Each of the divided base bodies 14A, 14B has an outer cover member 15A, 15B individually.
Is installed. Further, in order to form a flat toner transport path, a bridge member 15a is installed at the joint portion between the outer jacket members 15A and 15B.

At the upstream side of the toner conveying path, a doctor blade 18 for regulating the length of the toner to a proper length and forming a toner layer is provided. Doctor blade 1 of this example
8 is a posture in which the tip is brought close to the surface of the outer covering member 15B,
It is fixed to the side wall of the unit container 11. On the downstream side of the doctor blade 18, the peripheral surface of the jacket member 15A has a cylindrical electrode 5
The position closest to the peripheral surface with a minute gap therebetween is the recording portion W, where the magnetic toner d is selectively transferred to the surface of the cylindrical electrode 5 according to the input recording data to form a toner recording image. A scraping plate 19 is disposed on the downstream side of the recording unit W in a posture in which the tip end is in pressure contact with the surface of the outer cover member 15A. The scraping plate 19 scrapes off the residual magnetic toner d ′ that has been conveyed without being used in the recording section W.

On the surface of the outer cover member 15A, a recording electrode sheet 20 is laid in an area upstream of the recording portion W in the toner conveying direction B. As shown in FIG. 7, the recording electrode sheet 20 of this example has a flexible printed circuit board (FP
C), a plurality of recording electrode wires 20a extending parallel to each other in the longitudinal direction of the sheet are connected to the base film 20b.
Sheet width direction on top (toner conveyance path width direction: main scanning direction)
Are formed so as to extend in parallel at a predetermined fine pitch. The number of the recording electrode lines 20a corresponds to the maximum number of data for one main scanning line. In this example, a large number of recording electrode wires 20
a with a pitch of 86 μm (300
The pattern is formed by etching at a density of DPI). Then, a protective coat 20c made of an insulating material is deposited on the recording electrode wires 20a except for the tips, and the exposed tips of the recording electrode wires 20a are used as the recording electrodes EL. The protective coat 20c is applied to prevent the recording electrode wires 20a from being worn due to friction with the magnetic toner and to ensure insulation between the recording electrode wires 20a.

The recording electrode sheet 20 constructed as described above.
Is submerged below the bridge member 15a, and the divided base 14
The inner space S is laid through the joint surfaces of A and 14B. In the internal space S, a plurality of electrode drive circuit elements 21 for driving the recording electrode lines according to the recording data are arranged. The recording electrode lines of the above-described recording electrode sheet 20 are connected to these electrode driving circuit elements 21 in an appropriate number of lines. From each electrode drive circuit element 21, an input wiring circuit 22 is drawn out of the recording unit Uw from the other joint surface of the divided substrates 14A and 14B. The input wiring circuit 22 is connected to a recording control unit (not shown).

Further, as shown in FIG. 2, in the internal space S,
Switch 17 for switching the conductor connection of the coil section described above
A toner transport control circuit element 23 connected to the printer (see FIG. 5) is also provided. This toner transport control circuit element 23 and FIG.
The switch 17 shown in FIG. 2 constitutes a developer transport control means. The toner transfer control circuit element 23 selectively switches the connection changeover switch of the conductor 16a from parallel connection to cross connection during non-recording to switch the toner transfer direction on the upstream side of the recording unit W. However, the non-recording time is a time when print data is not input to the electrode drive circuit element 21 from the print control unit (not shown).

Now, a recording image forming operation in the electrostatic recording apparatus having the above-mentioned structure will be described. In FIG. 2, when a sine wave current as described above is applied to the exciting coil, a traveling wave magnetic field moving in the direction of arrow (a) is formed on the outer peripheral surface of the area of the recording unit Uw where the exciting coil is arranged. , The magnetic toner d forms an ear and the opposite arrow
It is conveyed in the (b) direction. The magnetic toner d conveyed is regulated by the doctor blade 18 to have a predetermined thickness and then conveyed to the recording unit W. At this time, the magnetic toner d is negatively charged by friction.

In the recording portion W, the drive circuit element 21 selectively applies a recording voltage to each recording electrode EL in accordance with recording data to form an electric field between the recording electrode EL and the peripheral surface of the cylindrical electrode 5 to thereby generate a magnetic field. The toner d is selectively transferred to the peripheral surface of the cylindrical electrode 5. In this example, when the 1-bit recording data is “H”, a voltage of −180 V is applied to the corresponding recording electrode EL. At this time, a bias voltage having the same polarity as the toner charging polarity is applied to the cylindrical electrode 5 facing the recording electrode EL by the bias power source 5a. In this example, since the triboelectrification polarity of the toner is negative (-), a negative bias voltage is applied and the voltage is set to -30V.
Therefore, 150 V from the cylindrical electrode 5 to the recording electrode EL
An electric field is formed based on the potential difference between the two. Since the negatively charged magnetic toner d moves to the higher potential side, in the recording portion W where the distance is the smallest and the electric field is maximum, −18
Only the magnetic toner d on the recording electrode EL to which the voltage of 0 V is applied is selectively transferred to the surface of the cylindrical electrode 5 to form a black dot.

On the other hand, when the 1-bit recording data is "L", the recording electrode EL becomes the ground potential. As a result, the potential difference seen from the cylindrical electrode 5 to the corresponding recording electrode EL is -30V.
Therefore, the negative polarity magnetic toner d remains held on the recording electrode EL side and does not transfer.

As described above, the potential of the recording electrode EL is selectively controlled to -180 V and the ground potential in accordance with the input recording data, and the toner recording image corresponding to the recording data is formed on the facing portion of the circumferential surface of the cylindrical electrode 5. It is formed. The density of the toner recorded image can be adjusted by changing the bias voltage of the bias power source 5a. In that case, the appropriate adjustment range is 0
It is about -40V, and the closer to 0V, the higher the image density.

The magnetic toner d'which has not been transferred to the cylindrical electrode 5 side at the recording portion W moves to the downstream side and is scraped off from the surface of the outer covering member 15A by the scraping plate 19 and agitated and mixed with the stored magnetic toner. To be done.

As shown in FIG. 1, the toner recording image formed on the surface of the cylindrical electrode 5 has a counterclockwise direction a of the cylindrical electrode 5.
Is conveyed to the image transfer portion T with the rotation of, and is transferred onto the sheet which is re-fed by the standby roll pair 3 at a timing. The untransferred toner dr, which is not transferred and remains on the circumferential surface of the cylindrical electrode 5, is conveyed to the recording portion W again as the cylindrical electrode 5 rotates.

Untransferred toner d returned to the recording section W
r is pulled to the recording electrode side when the input recording data is “L” and the recording electrode line is at the ground potential in the upstream region of the recording portion W, and is temporarily separated from the surface of the cylindrical electrode 5. or,
In this area, since the toner transport path on the recording unit Uw side is sharply narrowed facing the cylindrical electrode 5, the transported magnetic toner d temporarily stays and is separated from the cylindrical electrode 5 side. The untransferred toner dr is added to form a toner reservoir Rt in which the magnetic toner is retained at a relatively high density. The untransferred toner dr is also removed from the surface of the cylindrical electrode 5 by the scraping effect of the toner chain grown in the toner pool Rt. In this way, after the untransferred toner dr is removed from the peripheral surface of the cylindrical electrode 5 by cleaning, the recording operation is performed again in the recording portion W,
Even if a dedicated cleaning means is not provided, a high-resolution recorded image without image defects such as an afterimage can be stably formed.

However, in the above-mentioned toner pool Rt, the magnetic toner d which stays for a long time tends to be deposited on the surface of the outer covering member 15A to form a toner immobile layer. When the toner immovable layer is formed, it interferes with toner transportation and triboelectric charging, and deteriorates the image quality of a recorded image. In order to prevent the generation of this immovable layer, in the present invention, the switch 17 for switching the conductor connection of the coil portion shown in FIG. 5 is operated to selectively set the toner transport direction on the upstream side of the recording portion W to the forward direction during non-recording. Switch from (b) to the opposite direction (a). That is, the recording control unit determines that it is in the non-recording state, sends a signal to the toner transport control circuit element 23 to switch the transport direction, and receives the signal, the toner transport control circuit element 2 receives the signal.
3 switches the changeover switch 17 of FIG. 5 from the parallel connection shown in the diagram [a] to the cross connection shown in the diagram [b]. As a result, only the magnetic toner on the upstream side of the recording portion W is conveyed to the upstream side in the direction opposite to the forward direction indicated by the arrow (B). The magnetic toner on the downstream side is conveyed to the downstream side along the forward direction (b) as before switching. As a result, the toner pool Rt is eliminated and the generation of the immovable layer is reliably prevented. Therefore,
An adequate amount of the sufficiently charged magnetic toner can be smoothly conveyed to the recording unit W, and a recorded image of good quality without image defects such as density unevenness and afterimage can be stably formed.

The present invention is not limited to the above specific embodiment, and various modifications can be made within the technical scope of the present invention. For example, a PWM (pulse width modulation) current as shown in FIG. 8 is also applicable as the current having a repetitive waveform that is applied to the coil portion of the developer transport means. The example shown in FIG. 8 shows the PWM current that is supplied when the coil unit is divided into two sets. In this case, the PWM current represented by iA = PWM [Isin (ωt)] can obtain the same integrated current as when the above-mentioned sine wave current defined by iA = Isin (ωt) is applied. That is, the same result as when two kinds of sinusoidal currents as indicated by the broken line are applied.

Further, in order to switch the toner carrying direction,
Not limited to the method of switching the connection of the conductor 16a using the switch 17 as shown in FIG. 5, the currents to be transmitted to the respective coil parts on the upstream side and the downstream side of the recording part are individually controlled, and the upstream side and the downstream side are controlled. A configuration may be adopted in which the traveling direction of the phase of the current flowing through the coil section is independently switched.

[0042]

As described above in detail, according to the present invention, m sets of coil portions are arranged in parallel along the developer transport path and the connection of m conductor wires forming the coil portions is recorded. The coil parts on the upstream side and the downstream side can be switched with the parts sandwiched therebetween, and currents having repetitive waveforms are applied to these coil parts by shifting the phase by π / m in the order of arrangement, and the current is supplied to each coil part. By selectively switching the connection of the m conductors at the time of non-recording so that the arrangement order is reversed between the upstream side and the downstream side with respect to the recording section, the conveying direction of the developer only on the upstream side of the recording section W is changed. It can be reversed when not recording. As a result, the developer pool formed on the upstream side of the recording portion can be eliminated, and the generation of the immobile layer of the developer can be reliably prevented.
Therefore, the developer can be sufficiently triboelectrically charged and can be smoothly conveyed to the recording portion in an appropriate amount, and it is possible to stably obtain a high-resolution recorded image without image defects such as image unevenness.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the overall configuration of an electrostatic recording device as an embodiment of the present invention.

FIG. 2 is a schematic enlarged cross-sectional view showing a configuration of a recording image forming unit and its peripheral portion in the electrostatic recording device.

FIG. 3 is a graph showing a sinusoidal current flowing through the electrostatic recording device.

FIG. 4 is a graph showing a waveform of a traveling wave magnetic field formed in the electrostatic recording apparatus, the waveform traveling in the forward transport direction.

FIG. 5 is an explanatory diagram showing a conductor connection structure of a coil portion and a connection switching operation in the recording image forming unit.

FIG. 6 is a schematic cross-sectional view showing an operation of converting the toner conveyance direction in accordance with the switching of the arrangement of the coil portions and the conductor connection.

FIG. 7 is a partially cutaway perspective view showing a configuration of the recording image forming unit.

FIG. 8 is a graph showing a PWM current to be passed as another embodiment of the present invention.

[Explanation of symbols]

 5 Cylindrical electrode 14 Substrate 14A, 14B Divided substrate 15, 15A, 15B Enclosure member 16, 16Ai ... 16Mi Coil part 16a Conductor wire 17 Switch (conductor wire connection switching) 18 Doctor blade 19 Scraping plate 20 Recording electrode sheet 21 Electrode drive circuit element 23 Toner Transport Control Circuit Element Rt Developer Reservoir W Recording Section

Claims (1)

[Claims] 1. A developer carrying member whose surface serves as a developer carrying path, a developer carrying means for carrying a magnetic developer along the surface of the developer carrying member, and a developer carrying member on the surface of the developer carrying member. Recording means comprising a plurality of recording electrodes arranged in parallel in a width direction perpendicular to the direction at a predetermined interval while electrically insulating, and an electrode drive circuit for outputting a recording voltage according to input recording information to the recording electrodes. And a cylindrical electrode disposed opposite to the recording electrode with a predetermined gap provided therebetween, wherein the developer transport means disposes a base body made of a magnetic material along the back surface of the developer carrying member. Then, a plurality of recessed grooves are formed to extend in the width direction on the surface of the substrate facing the back surface of the developer carrying member, and a plurality of conductive wires are laid in the recessed grooves along the width direction. Forming a plurality of coil parts,
The coil section is divided into m sets, and each set of coil sections is (m-
1) It is formed by arranging every other coil, and each coil part belonging to the same group among the coil parts is supplied with a current having a repetitive waveform so that the directions of excited magnetic poles are alternately reversed, and By supplying currents having repetitive waveforms whose phases are sequentially shifted by π / m to m adjacent coil units belonging to different groups,
A traveling wave magnetic field that travels along the surface of the developer carrying member is formed to convey the magnetic developer in a predetermined forward direction, and the recording electrode is conveyed in a recording unit in the vicinity of the cylindrical electrode peripheral surface. In an electrostatic recording device that selectively transfers the magnetic developer to the peripheral surface of the cylindrical electrode according to the recording voltage to form a recorded image, the developer is used during recording when the recording voltage is applied to the recording electrode. Is conveyed in the forward direction, and at the time of non-recording in which the recording voltage is not applied to the recording electrode, the developer is conveyed in a direction opposite to the forward direction on the upstream side of the forward direction of the recording section, An electrostatic recording apparatus characterized in that a developer transport control means for transporting the developer in the forward direction is provided on the downstream side of the recording section.