JPH06171136A - Electrostatic recorder - Google Patents

Abstract

PURPOSE:To prevent developer from coagulating on a recording electrode and stably form a good image. CONSTITUTION:An electrostatic recorder has a direct-current motor 24 which drives a magnet roller, a driver 23 which determines the rotational direction of the direct-current motor 24, and a CPU 21 which controls driver 23 so that the magnet roller rotates in the opposite direction differently depending upon whether the recorder is in or out of recording action.

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 for transferring a developer 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 has been known as one of electrostatic recording devices. The multi-stylus printer has recording electrodes formed by arranging a large number of needle-shaped electrodes (styluses) at minute equal intervals in the main scanning direction. The developer is conveyed to the recording unit along the surface of the developer carrying member by the magnetic force of the magnet roll. And
In this recording section, a voltage is selectively applied to each needle electrode according to a recording signal, and the developer is transferred to the cylindrical counter electrode side by a discharge electric field to form a recorded image.

[0003]

By the way, since the discharge electric field from the recording electrode has a property of spreading with increasing distance, the recording electrode and the counter electrode should be brought into close contact with each other or as close as possible in order to improve the resolution. Deploy. In such a configuration, the developer remains on the recording electrode after printing, but if this state continues for a long time, the developer is agglomerated on the recording electrode due to the pressure and is removed by the conveyance force of the magnet roll. It becomes impossible. The recording electrodes are very sensitive to printing, and even a slight damage affects the image. When the agglomeration occurs, the transport of the developer is hindered, and as a result, an image is lost and a good image cannot be stably formed.

The electrostatic recording apparatus of the present invention has been made in view of such a problem, and its purpose is to make the rotation of the magnet roll different between the image recording operation and the non-recording operation. It is an object of the present invention to provide an electrostatic recording device capable of preventing a developer from aggregating on the recording electrode by controlling the above-mentioned control and stably forming a good image.

[0005]

In order to achieve the above object, an electrostatic recording apparatus of the present invention has a developer carrying member laid along a predetermined path and a surface of the developer carrying member. Magnet roll that conveys the developer made of a magnetic material by magnetic force, a plurality of recording electrodes arranged in parallel on the surface of the developer carrying member at intervals in the main scanning direction, and in contact with the recording electrodes or at minute intervals. And a counter electrode disposed opposite to each other and an electrode driving means for outputting a driving voltage to each of the recording electrodes, by the magnetic force of the magnet roll,
A developer that is conveyed to a recording portion where the recording electrode and the counter electrode face each other is selectively transferred to the counter electrode side by a recording electric field formed according to recording information to form a recorded image. The electrographic recording apparatus further comprises magnet roll driving means for rotationally driving the magnet roll, rotation direction indicating means for determining a rotation direction of the magnet roll driving means, and control means for controlling the rotation direction indicating means. The control means controls the rotation direction instructing means such that the rotation of the magnet roll by the magnet roll driving means is different during the image recording operation and the non-recording operation by the recording electrode.

[0006]

That is, in the electrostatic recording apparatus of the present invention,
The rotation direction instruction means is controlled so that the rotation direction of the magnet roll during image recording by the recording electrode and the rotation direction of the magnet roll during non-recording operation are different.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic sectional view showing the overall construction of an electrostatic recording apparatus according to 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 stored,
It is attached to the side of the machine so that it can be inserted and removed freely. A paper feed roller 2 is disposed above the leading end of the attached paper feed cassette 1 so as to be rotatable in the arrow direction. A standby roll pair 3 is arranged in front of the paper feed roller 2, and after temporarily stopping the progress of the paper P fed by the paper feed roller 2 to adjust the conveyance posture, the image transfer unit on the downstream side is provided. The sheet is re-fed so as to be synchronized with the arrival timing of a recording image described later to T.

A transfer roll 5 is arranged in front of the sheet conveying path 4 extending obliquely downward from the standby roll pair 3. A sleeve-shaped cylindrical electrode 6 as a counter electrode is arranged to face the transfer roll 5. The portions of the cylindrical electrode 6 and the transfer roll 5 that face each other on the peripheral surface serve as the image transfer portion T.
As will be described later, the toner recording image is formed on the circumferential surface of the cylindrical electrode 6 and then conveyed to the image transfer portion T along with its rotation. In synchronism with this, since the sheet is conveyed from the standby roll pair 3 to the image transfer portion T, the toner image is transferred to the transfer roll 5
And is transferred onto the paper sandwiched between the cylindrical electrodes 6.

In this embodiment, the cylindrical electrode 6 is driven and rotated in the clockwise direction indicated by arrow a. A bias power supply 6a for applying a bias voltage having the same polarity as the toner charging polarity is connected to the cylindrical electrode 6. In this embodiment, a two-component developer including a toner having a negative (-) triboelectric charging characteristic and a magnetic carrier having a positive (+) triboelectric charging characteristic is used as the developer. Therefore, a negative voltage is applied by the bias power source 6a and the voltage value is set to -50V. The cylindrical electrode 6 of this embodiment is arranged in a recording image forming unit U which is detachably attached to the machine body. The configuration of the recording image forming unit U will be described in detail later.

On the downstream side of the image transfer section T, an air suction type conveyor belt 7 is horizontally stretched. A fixing device 8 is disposed in front of the downstream side of the conveyor belt 7.
The fixing device 8 of this embodiment includes a heating roll 8a and a pressure contact roll 8b.
The toner image is heat-fixed when the paper is nipped and conveyed between the rolls 8a and 8b. The sheet of paper which has been fixed is discharged and stacked on the discharge tray 10 in a face-down state with the image side facing down from the discharge port 9. Here, the detailed configuration of the recording image forming unit U will be described with reference to FIG.

The recording image forming unit U generally comprises the above-mentioned cylindrical electrode 6, a toner storage tank 11 for storing the replenishment toner t0, and a development recording tank 12 having a recording means and a developer conveying means. Inside the toner storage tank 11, the stirring blade 1
1a is rotatably arranged. The stirring blade 11a stirs the stored replenishment toner t0 to prevent aggregation. A toner supply port Os is formed at the boundary between the toner storage tank 11 and the development recording tank 12, and a toner supply roll 13 is installed at this toner supply port Os. The toner replenishing roll 13 is rotated according to the toner concentration of the developer d flowing in the developing and recording tank 12, and replenishes the replenishment toner t0 into the developing and recording tank 12 by an appropriate amount. As a result, the toner concentration of the developer d in the development recording tank 12 is controlled within the proper range. The developer is not limited to a two-component developer, and a one-component developer such as a magnetic toner composed of an insulating resin, magnetic fine powder and colorant particles can also be used. In this case, the toner density control as described above becomes unnecessary.

At the bottom of the development recording tank 12, two auger rolls 14a and 14b are installed so as to extend parallel to each other in the direction perpendicular to the paper surface. These auger rolls 14a, 14b
Are rotated in the opposite directions B and C, respectively, and circulate and flow the developer d in the horizontal direction while stirring. In the present embodiment, the size of the stirring blades of both auger rolls 14a and 14b is made different, and a large stirring blade auger roll 14a is disposed below the toner replenishing roll 13.

A developing sleeve 15 as a developer carrying member for forming a vertical transport path for the developer is installed horizontally extending diagonally above the auger roll 14b of the small stirring blade. Inside the developing sleeve 15, a magnet roll 16 as a developer carrying means is rotatably mounted inside. Different magnetic poles are alternately magnetized on the circumferential surface of the magnet roll 16, and by rotating the magnet roll 16 in the clockwise direction indicated by the arrow D,
The developer d is conveyed in the direction indicated by the arrow E along the peripheral surface of the developing sleeve 15.

Thus, the developing sleeve 15 is arranged in parallel and opposite to the above-mentioned cylindrical electrode 6. In this case, the both are arranged from the vertical normal line r of the developing sleeve 15 to the toner carrying direction E. The arrangement is such that the center of the cylindrical electrode 6 is located on the normal line r'rotated upstream by the central angle of the developing sleeve 15 by the angle θ. Therefore, the peripheral surface of the cylindrical electrode 6 is closest to the developer carrying path formed along the peripheral surface of the developing sleeve 15 on the normal line r '. The position where the peripheral surface of the cylindrical electrode 6 is closest to the developer transport path is the recording portion W for forming a toner recording image as described later.

By setting the recording portion W at the position inclined by the angle θ to the upstream side as described above, the amount of the developer to be retained on the upstream side of the recording portion without providing the developer transport restricting member is as follows. Then, it can be automatically controlled to a substantially constant proper amount.

The amount of the developer d conveyed on the developer conveying path along the developer conveying direction E is regulated in the vicinity of the upstream side of the recording portion W where the developer conveying path is narrowed. As a result, among the developer d whose progress is regulated, those in the area near the surface of the developing sleeve 15 where the magnetic force of the magnet roll 16 is sufficiently circulate as shown by the arrow in that area,
When the magnet roll 16 has moved to a region where the magnetic force hardly reaches, the auger roll 14 is moved by pressure as shown by the arrow G.
fall on b. In this case, when the amount of the developer regulated to be conveyed increases, the amount of the developer that flows and returns as shown by the arrow G naturally increases, and the amount of staying developer is automatically controlled to a substantially constant appropriate amount. It As a result, it is possible to easily and surely prevent the generation of the immobile developer without performing a troublesome operation such as adjusting the posture of the regulating member. Further, the amount of the developer carried into the recording portion W can be properly regulated without providing a unique developer transport regulation member. Therefore, the cost for installing the developer transport restricting member such as the doctor blade is reduced and simplification of the structure is promoted.

On the peripheral surface of the developing sleeve 15 on the downstream side of the recording portion W, a scraping plate 17 is vertically provided with its tip abutting against the peripheral surface of the developing sleeve 15. Due to the scraping plate 17, the residual developer d'not used in the recording section W is circulated horizontally at the bottom of the developing and recording tank 12.
It is scraped up.

A recording electrode sheet 18 having a large number of recording electrodes formed in parallel at one end is laid along the peripheral surface of the developing sleeve 15 on the upstream side from the recording portion W. As shown in FIG. 3, the recording electrode sheet 18 has a large number of recording electrode wires 18a having recording electrodes EL at the tips thereof extending parallel to each other in the sheet longitudinal direction along the circumferential direction of the peripheral surface of the developing sleeve 15. At the same time, they are arranged in parallel in the sheet width direction (main scanning direction) at a predetermined fine pitch. In this case, the number of recording electrode lines 18a, that is, the number of recording electrodes EL corresponds to the maximum number of data for one main scanning line. The recording electrode sheet 18 of this embodiment is a flexible printed circuit board (FPC).
The recording electrode lines 18a (recording electrodes EL) made of a large number of non-magnetic conductive materials are arranged on the base film 18b made of a flexible insulating material with a spacing of 40 μm.
It is laid at a density of 4.6 μm pitch (300 DPI). An insulating protective coat (not shown) is applied to the surface of the recording electrode sheet 18 except for the tip end region. The tip portion of the recording electrode wire 18a which is not covered with the insulating protective coat serves as the recording electrode EL.

At the end of the recording electrode sheet 18 opposite to the side where the recording electrodes are formed, an LSI 19 as an electrode drive circuit element is provided.
It is equipped with multiple. A plurality of recording electrode wires 18a are separately connected to the plurality of LSIs 19 and connected to each other. Each LSI 19 is connected to a recording control unit (not shown) that controls the entire recording operation of the electrostatic recording apparatus of this embodiment. The recording control unit sends a recording signal corresponding to the recording information to the LSI 19, and also selectively sends an instruction signal for carrying out cleaning of untransferred toner, which will be described later, during non-recording in which no recording signal is sent.

As shown in FIG. 4, on the peripheral surface of the developing sleeve 15, flat portions 15a, 15b and 15c are respectively formed at the recording portion W and at three positions upstream and downstream thereof. The end of the recording electrode sheet 18 on which the recording electrode EL is formed is projected in a curved shape above the area of the substantially half upstream side of the plane portion 15a of the recording portion W.
The protruding end portion of the recording electrode sheet 18 is the developing sleeve 1
5 is laid on a spring plate member (not shown) curved to have substantially the same curvature as the peripheral surface of No. 5. As a result, the recording electrode EL becomes hollow and elastically supported, and the developer d can be flexibly held in the minute gap of the recording portion W formed by the circumferential surface of the cylindrical electrode 6. In the recording portion W, the tip of the recording electrode EL is lightly pressed against the cylindrical electrode 6, but it may be set to a minute gap that allows the toner to pass through.

On the flat surface portion 15b on the upstream side of the recording portion W, an end portion of the recording electrode sheet 18 on which the LSI 19 is mounted is laid. In this way, L on the peripheral surface of the developing sleeve 15
By forming the flat portion 15b for SI installation, the LS
Installation of I19 becomes easy. Then, on the recording electrode sheet 18 and the LSI 19 laid on the flat portion 15b,
A cover film 20 made of a non-magnetic material is covered with a curved surface having substantially the same curvature as the peripheral surface of the developing sleeve 15. As a result, the surface of the cover film 20 serves as a developer transport path, and it is possible to prevent the LSI 19 from being damaged by friction with the developer or the like. Further, since the cover film 20 is bent and installed in an arc shape, the developer can be smoothly moved along the surface thereof. Instead of covering the cover film 20, the surface of the recording electrode sheet 18 may be coated with a non-magnetic material.

LSI of recording electrode EL and electrode driving circuit element
The recording electrode wire portion connecting 19 with the electrode drive circuit element serves as a connecting member that constitutes an electrode drive means. This connecting member portion serves as a cleaning means for cleaning the untransferred toner as described later.

By disposing the electrode driving circuit element of the recording electrode EL on the peripheral surface of the developing sleeve 15 as described above,
The connecting member can be made as short as possible. That is, the recording electrode line connecting the recording electrode EL and the LSI 19 can be short. From these, not only is the recording electrode sheet 18 small and inexpensive, but the so-called antenna effect due to the recording electrode wire is also reduced, making it less susceptible to noise. As a result, it is possible to stably form a recorded image that accurately corresponds to the recorded information. Further, by disposing the electrode driving circuit element on the upstream side of the recording electrode EL, the recording electrode EL is configured to project in the forward direction (trailing direction) with respect to the rotation direction of the cylindrical electrode 6, so that the recording electrode EL is formed.
Will not be damaged.

The flat surface portion 15c on the downstream side of the recording portion W is formed in order to quickly convey the residual developer d'which is carried out without being transferred to the cylindrical electrode 6 in the recording portion W to the downstream side.
By cutting off the peripheral surface portion of the developing sleeve 15 to form the flat surface portion 15c, the developer conveying path (the surface of the flat surface portion 15c) becomes closer to the magnet roll 16 as compared with the case where it is not formed, and the magnet roll 16 has a corresponding portion. The magnetic force increases and the carrying force increases. Therefore, the residual developer d ′ can be quickly carried out from the recording portion W, and the toner recording image formed on the circumferential surface of the cylindrical electrode 6 is not disturbed by the residual developer d ′. Next, a recording image forming operation in the electrostatic recording apparatus of this embodiment will be described.

In FIG. 2, when the magnet roll 16 is driven and rotated in the arrow E direction, a rotating magnetic field for rotating the magnetic carrier particles in the developer d is formed on the outer peripheral surface of the developing sleeve 15. The rotating magnetic field attracts the developer d circulating and flowing in the horizontal direction at the bottom of the developing recording tank 12 to the peripheral surface side of the developing sleeve 15, and the cover film 20.
It is conveyed in the counterclockwise direction e opposite to the rotating direction of the magnet roll 16 while forming the top.

In FIG. 4, the amount of the developer d conveyed upward along the surface of the cover film 20 is regulated on the upstream side of the recording portion W where the peripheral surface of the cylindrical electrode 6 is close and the conveying path is narrowed. To form a developer pool Rt. And
The developer particles that have moved far from the developer transport path (the surface of the recording electrode sheet 18) within the regulated developer are separated from the magnetic field of the magnet roll 16 and naturally fall to the bottom of the development recording tank 12 as indicated by an arrow G. . As a result, the developer pool Rt
The amount of the developer forming the toner is automatically controlled to an appropriate amount, and the generation of the immobile developer is reliably prevented. Further, the amount of the developer carried into the recording portion W is properly controlled, and a proper amount of the developer particles is smoothly carried into the minute gap between the elastically supported recording electrode EL and the circumferential surface of the cylindrical electrode 6 and is flexibly held. It As a result, the developer is excessively compacted in the recording portion W and the recording electrode EL
It is possible to prevent the problem of fusing on the surface of the cylindrical electrode 6 and stably form a high-resolution recorded image having a sufficient image density on the circumferential surface of the cylindrical electrode 6 in the following manner.

That is, in the recording portion W, the peripheral surface of the cylindrical electrode 6 is rotationally moved with respect to the recording electrode EL while maintaining a minute gap, and the developer d is carried into the minute gap in an appropriate amount as described above. . In this recording unit W, each recording electrode EL
On the other hand, the LSI 19 of the electrode drive circuit element selectively applies the recording voltage according to the recording data. In this case, when the 1-bit recording data is, for example, “H”, a voltage (ON voltage) of −200 V is applied to the corresponding recording electrode EL in this embodiment.
Is applied. A bias voltage of -50 V is applied to the cylindrical electrode 6 facing the recording electrode EL by the bias power supply 6a in this embodiment. Therefore, an electric field based on the potential difference of 150 V is formed from the circumferential surface of the cylindrical electrode 6 toward the recording electrode EL. The ears of the developer d pass through the recording portion W in which such an electric field is formed while contacting the peripheral surface of the cylindrical electrode 6. At this time, since the negatively charged toner particles move to the higher potential side, only the toner particles on the recording electrode EL to which the on-voltage of −200 V is applied are selectively on the circumferential surface of the cylindrical electrode 6. , And one black dot is formed.

On the other hand, when the 1-bit recording data is "L", the voltage applied to the recording electrode EL by the LSI 19 is switched to the ground potential (off voltage) side. as a result,
The potential difference seen from the cylindrical electrode 6 to the recording electrode EL at the ground potential is −50 V, and the toner particles of negative polarity are retained on the recording electrode EL side and do not transfer. In this way, the occurrence of background dirt is reliably prevented.

As described above, the potential of each recording electrode EL is selectively controlled to -200 V and the ground potential according to the input recording data, and the toner recording image is formed on the surface of the cylindrical electrode 6 in the recording portion W. In order to adjust the density of the toner recording image, the bias voltage of the bias power source 6a may be changed. In that case, an appropriate adjustment range is about 0 to -50V, and the closer to 0V, the higher the image density.

In the recording portion W, the developer not transferred to the cylindrical electrode 6 side and remaining on the recording electrode EL side drops onto the downstream surface of the flat portion 15a immediately after the toner recording image is formed. The residual developer d'is transported to the downstream flat surface portion 15c by the rotating magnetic field described above. Since the surface of the downstream flat surface portion 15c is formed close to the magnet roll 16, a strong rotating magnetic field is formed on the surface thereof compared to the developer transport path on the upstream side of the recording portion such as the surface of the cover film 20. The residual developer d'has been carried out is promptly carried out to the downstream side. Therefore, the residual developer d'is left in the immediately downstream portion of the recording portion W, so that the toner recording image on the circumferential surface of the cylindrical electrode 6 is not disturbed.

In FIG. 1, the toner recording image formed on the surface of the cylindrical electrode 6 is conveyed to the image transfer portion T along with the rotation of the cylindrical electrode 6 in the counterclockwise direction (a), and the timing is measured by the standby roll pair 3 here. And is transferred onto the paper that is re-fed. The untransferred toner that has not been transferred and remains on the circumferential surface of the cylindrical electrode 6 is returned to the recording portion W again as the cylindrical electrode 6 rotates. The untransferred toner remaining on the circumferential surface of the cylindrical electrode 6 is removed as follows.

That is, in FIG. 2, a recording control unit (not shown) sends a cleaning signal to the LSI 19 in anticipation of a non-recording time such as a time corresponding to a paper-to-paper transportation interval, and the LSI 19 receiving this signal, A cleaning voltage is applied to the recording electrode wire. The cleaning voltage in this case forms an electric field capable of transferring the untransferred toner remaining on the circumferential surface of the cylindrical electrode 6 to the recording electrode sheet 18, that is, an electric field in the direction opposite to the electric field based on the ON voltage described above. Since it is necessary, the potential is set higher than the bias voltage applied to the cylindrical electrode 6. That is, in this embodiment, since the bias voltage of the cylindrical electrode 6 is set to -50V, the cleaning voltage is set to + 50V, for example. As a result, the potential difference when the recording electrode wire 18a is seen from the cylindrical electrode 6 becomes −100V, and the cleaning electric field based on this potential difference is generated from the area where the recording electrode wire 18a and the circumferential surface of the cylindrical electrode 6 face each other, that is, from the recording portion W. It is formed over an area (hereinafter referred to as a cleaning area) where the connecting member portion of the recording electrode wire 18a and the circumferential surface of the cylindrical electrode 6 face each other on the upstream side. The developer pool Rt described above is formed in this cleaning region.

The cleaning electric field has the same direction as the electric field (corresponding to the white dot) based on the potential difference of -50 V formed corresponding to the recording signal of "L" (corresponding to the white dot) and the magnitude thereof is larger than that. By this cleaning electric field, the negatively charged untransferred toner is forcibly separated from the peripheral surface of the cylindrical electrode 6, and is collected in the developer pool Rt. or,
The untransferred toner is also removed from the circumferential surface of the cylindrical electrode 6 by the scraping effect of the developer circulating and flowing in the developer pool Rt. As described above, since the untransferred toner is removed and the cleaning is surely performed on the surface of the cylindrical electrode 6 and the recording operation is performed again after the untransferred toner is removed, a high-quality recording without an image defect such as an afterimage due to defective cleaning is performed. The image is stably formed. Further, since the entire recording means including the recording electrode EL, the LSI 19 as the electrode driving means for the electrode, and the recording electrode wire 18a that is a connecting member for the recording electrode EL is provided on the upstream side of the recording portion W, the formed recorded image is recorded from the time of recording. It is not disturbed by the cleaning electric field when shifting to the non-recording time.

The residual developer d ′ discharged and conveyed downstream from the recording section W is developed by the scraping plate 17 into the developing sleeve 15.
It is scraped off from the peripheral surface and dropped back to the bottom of the development recording tank 12. The residual developer d ′ returned is the auger roll 1
The developer d, which circulates and flows in the horizontal direction as the 4a and 14b rotate, is agitated and mixed.

FIG. 4 shows a state around the recording electrodes during printing. When the magnet roll 16 rotates in the direction D, the developer d is conveyed in the opposite direction E, and is guided between the cylindrical electrode 6 and the electrode tip end EL to perform development. At this time, the progress destination of the developer d becomes gradually narrower between the developer d and the cylindrical electrode 6. Therefore, the density of the developer d becomes higher as it goes further.

FIG. 5 shows the state around the recording electrodes when printing is completed and the next printing is waited. With the above-described structure, the developer is sandwiched between the cylindrical electrode 6 and the recording electrode, that is, on the recording portion W, and the pressure is densely applied. If left as it is for a long period of time, further aggregation will proceed due to pressure and the like. The recording electrode is the most important part and no damage is allowed. The sticking of the developer between the recording electrodes or on the recording electrodes causes a trouble in the conveyance of the developer. Even slight damage will affect the image quality,
A stable and good image cannot be expected. Therefore, in the present embodiment, the above problem is solved by rotating the magnet roll 16 in the reverse direction at the end of printing. Hereinafter, this will be described in detail.

FIG. 6 is a view showing a state in which the magnet roll 16 is rotating in the reverse direction. The rotation direction of the magnet roll 16 at the time of normal printing is the direction shown in FIG.
Then, it is rotated in the direction of a, which is the opposite rotation. The magnetic field generated by this rotation causes the developer, which is a magnetic material, to be conveyed in the direction of (a). Then, the developer accumulated between the cylindrical electrode 6 and the recording electrode advances in the direction of being released from this gap. Here, the rotation direction D of the magnet roll 16 at the time of printing is defined as positive rotation, and the rotation direction of the magnet roll 16 in the direction D in which the developer is not conveyed to the recording portion W is defined as reverse rotation.

FIG. 7 shows a state after the magnet roll 16 has been reversely rotated for a certain period of time. As shown in the figure, since the flat surface portion 15a and the tip portion of the recording electrode EL form a step corresponding to a distance x (x is, for example, about 0.5 mm),
The residual developer d ′ collects under the recording electrode EL and does not enter the recording portion W beyond the step. Further, all or most of the developer existing in the vicinity of the recording portion W is returned to the developing device again.

Here, in the present embodiment, not all the developer may be removed from the recording portion W. The magnetic force of the magnet roll 16 is larger than the cohesive force due to the pressure generated when the developer pool is left for a long period of time, which causes the developer in the vicinity of the recording portion W to form a soft brush and the developer to be densely packed. It just has to be released from the state. As described above, it is possible to prevent the developer from agglomerating on the recording portion W by rotating the magnet roll 16 in the reverse direction.

FIG. 8 is a block diagram showing the configuration of a control circuit for controlling the rotation of the magnet roll 16 described above.
In the figure, a rotation request signal 2 for the magnet roll 16
When 1a is emitted from the CPU 21 as the control means, the pulse generator 22 outputs the PWM (pulse width modulation) signal 22a.
To occur. The PWM signal 22a is a pulse signal having a pulse width that is varied according to the magnitude of the DC voltage output according to the rotation speed of the DC motor 24 in order to keep the rotation speed of the DC motor 24 constant, It is supplied to the driver 23 as a rotation direction indicating means.

Further, a direction designating signal (CW / CCW bar)
21 b is sent from the CPU 21 directly to the driver 23.
The PWM control signal 23a from the driver 23 drives the DC motor 24 as a magnet roll driving means for rotating the magnet roll 16.

FIG. 9 is a detailed circuit diagram of the driver 23. The driver 23 has an H-type bridge configuration. PWM signal 22a when the direction designation signal 21b is H
This turns on the transistors Q1 and Q4, which causes the point at M1 to have a potential of approximately + Vcc and the point at M2 to have a potential of approximately 0V. Therefore, the DC motor 24 rotates the magnet roll 16 forward. Further, when the direction designation signal 21b is at L level, the transistor Q2 and the transistor Q3 are turned on by the PWM signal 22a, so that the point of M2 becomes a potential of approximately + Vcc and the point of M1 becomes approximately 0V. Therefore, the magnet roll 16 can rotate in the reverse direction.

FIG. 10 is a time chart showing the operation of the control circuit shown in FIG. 8 when the magnet roll 16 is rotated in the reverse direction. As shown in the figure, the two signals issued from the CPU 21, the rotation request signal 21a of the magnet roll 16 and the direction designation signal 21b are binary logic signals. The rotation request signal 21a of the magnet roll 16 becomes H level when the magnet roll 16 needs to rotate regardless of whether the magnet roll 16 is forward or reverse for a predetermined period in the sequence. The direction designation signal 21b becomes an L level signal only when the magnet roll 16 rotates in the reverse direction, and becomes an H level signal during other printing or during standby. As described above, in this apparatus, the magnet roll 16 rotates normally when the direction designation signal 21b is at the H level, and reversely rotates when the direction designation signal 21b is at the L level.

At the start of printing, the magnet roll 16 rotates forward. That is, at this time, both the rotation request signal 21a and the direction designation signal 21b of the magnet roll 16 are at the H level. When the printing is completed, the motor 24 stops and the magnet roll 16 stops. But the motor 24
That is, since the magnet roll 16 does not stop suddenly but rotates for a predetermined period due to inertia, if a request for reverse rotation is made at this time, the motor 24 will be overloaded. Therefore, the reverse rotation may be performed after the stop of the magnet roll 16 is detected by a sensor or the like, but in the present embodiment,
Rotation request signal 2 of magnet roll 16 after printing is completed
After a certain time elapses from when 1a becomes L level until the motor 24 actually stops, the direction designation signal 21b is set to L level and the rotation request signal 21a of the magnet roll 16 is set to H level, so that the magnet roll 16 is moved. Reverse rotation. After a lapse of a certain time until the motor 24 actually stops, the rotation request signal 21a of the magnet roll 16 is set to L level to stop the motor 24, and the direction designation signal 21b is set to H level to wait for the next printing. . It should be noted that the present invention should not be limited to the above-mentioned specific embodiments, and it goes without saying that various modifications can be made within the technical scope of the present invention.

For example, although the counter electrode is formed as a sleeve-shaped cylindrical electrode in the above embodiment, the present invention is not limited to this, and the present invention is also applied to an electrostatic recording device in which the cylindrical electrode is formed as, for example, an endless belt. be able to. Further, the developer carrying member may be formed in an endless belt shape. Further, the developer is not limited to a toner having a negative triboelectric charging property, and a developer containing a positive toner may be used.

As described above, according to the above-described embodiment, since the magnet roll 16 is reversely rotated for a fixed time at the end of printing, the developer is not pressed into the gap between the counter electrode and the recording electrode during printing standby, and the developer is compacted. It does not become stuck. As a result, it is possible to prevent the developer from agglomerating on the recording electrode during printing standby and causing a developer conveyance failure during printing. Therefore, it is possible to stably form a high-resolution recorded image without an image defect such as an image loss due to poor conveyance.

[0048]

As described above in detail, in the electrostatic recording apparatus of the present invention, the rotation of the magnet roll is controlled so as to be different during the image recording operation and the non-recording operation. Aggregation of the developer is prevented and a good image is stably formed.

[Brief description of drawings]

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

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

FIG. 3 is a perspective view showing a configuration of a recording electrode sheet and its peripheral portion.

FIG. 4 is a schematic cross-sectional view showing a state around a recording unit during image formation.

FIG. 5 is a schematic cross-sectional view showing a state around a recording unit when waiting for printing.

FIG. 6 is a schematic cross-sectional view of the periphery of a recording unit showing a state in which a magnet roll is rotating in the reverse direction.

FIG. 7 is a schematic cross-sectional view of the periphery of a recording unit showing a state after the magnet roll is reversely rotated for a certain period of time.

FIG. 8 is a block diagram showing a configuration of a control circuit that controls rotation of a magnet roll.

FIG. 9 is a detailed circuit configuration diagram of a driver.

FIG. 10 is a view showing a case where the magnet roll is rotated in the reverse direction.
4 is a time chart showing the operation of the control circuit shown in FIG.

[Explanation of symbols]

6 ... Cylindrical electrode, 15 ... Development sleeve, 16 ... Magnet roll, 19 ... Electrode drive circuit element, 21 ... CPU, 22
... pulse generation circuit, 23 ... driver, 24 ... DC motor, EL ... recording electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Takeuchi 3-2-1 Sakaemachi, Hamura-shi, Tokyo Casio Computer Co., Ltd. Hamura Technical Center

Claims (1)

[Claims] 1. A developer carrying member laid along a predetermined path, a magnet roll for carrying the developer made of a magnetic material by magnetic force along the surface of the developer carrying member, and a developer carrying member of the developer carrying member. A plurality of recording electrodes that are arranged in parallel on the surface in the main scanning direction at intervals, counter electrodes that are in contact with the recording electrodes or are opposed to each other with a minute interval, and an electrode drive that outputs a driving voltage to each recording electrode. Means and
The magnetic force of the magnet roll selects the developer conveyed to the recording portion where the recording electrode and the counter electrode face each other to the counter electrode side by the recording electric field formed according to the recording information. In an electrostatic recording apparatus that transfers a magnetic image to form a recorded image, a magnet roll driving unit that rotationally drives the magnet roll, a rotation direction instruction unit that determines a rotation direction of the magnet roll driving unit, and a rotation direction instruction. Further comprising a control means for controlling the rotation means so that the rotation of the magnet roll by the magnet roll drive means is different during image recording operation by the recording electrode and during non-recording operation. An electrostatic recording device characterized by controlling a direction indicating means.