JPH04216565A - Electrophotographic recorder - Google Patents

Abstract

PURPOSE:To reduce the cost of a recorder, to miniaturize the recorder and to make the power consumption thereof low by performing image recording in an electrophotographic process without providing a destaticizing device. CONSTITUTION:A transfer roller 6 is provided to be opposed to a photosensitive drum 1. A power source 62 which generates the specified potential V1 of a reverse polarity to the electrostatically charged polarity of the drum 1 or ground is alternatively connected to the transfer roller 6 through a switch 61. At the time of stopping a recording action, the transfer roller 6 is connected to the ground as soon as the trailing edge of a recording paper 9 passes a transfer position D. Thereafter, a switch 32 and a switch 54 are turned off when a specified point on the photosensitive body positioned at the transfer position D arrives at an electrostatic charging position A and at a developing position C, respectively, and the switch 61 is opened when the specified point on the photosensitive body positioned at the transfer position D goes round and reaches the transfer position D again.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus for recording images by an electrophotographic process.

0002

2. Description of the Related Art In an electrophotographic recording apparatus such as a laser printer, for example, after toner is transferred from the photosensitive surface of a photosensitive drum, residual charges are removed by a charge removing device. Here, as the static eliminator, for example, an LED array, a xenon tube, a fluorescent lamp, etc. are generally used.

By the way, an LED array is constructed by one-dimensionally arranging a large number of LEDs, and is expensive. Furthermore, although xenon tubes and fluorescent lamps are relatively inexpensive, they consume large amounts of power and occupy a large area.

0004

[Problems to be Solved by the Invention] As described above, in conventional electrophotographic recording devices, it is necessary to provide a static eliminator such as an LED array, xenon tube, fluorescent lamp, etc., which increases cost, increases size, and consumes large amounts of electricity. There was a problem that led to electrification.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to record images in an electrophotographic process without installing a static eliminator, and to be inexpensive, small, and compact. An object of the present invention is to provide an electrophotographic recording device with low power consumption.

[0006]

[Means for Solving the Problems] The present invention provides an endless photoconductor such as a photoconductor drum made of a photosensitive conductive member, and a photoconductor rotation means such as a photoconductor drive system for rotating the photoconductor. a charging means provided opposite to the photoreceptor and charging the photoreceptor to a predetermined charging potential; and a charging means that exposes the photoreceptor charged by the charging means to light in accordance with an image to be recorded; an exposure means for forming an electrostatic latent image on the body, and the electrostatic latent image formed on the photoreceptor by the exposure means is developed by a developing bias of a predetermined potential having the same polarity as the charging potential and lower than the charging potential. a developing means for adhering an agent; and a developing means that is in contact with the photoreceptor, and when a recording paper is being supplied, the recording paper is held together with the photoreceptor, and the recording paper is applied to the photoreceptor by the developing means. A transfer means, such as a transfer roller, which transfers the attached developer, and a transfer voltage of a predetermined voltage for transfer processing with respect to the transfer means, or the photoreceptor at a transfer position where the transfer processing is performed by the transfer means. and a power supply means for selectively applying a predetermined charge eliminating voltage, such as a ground potential, which has a smaller absolute value than the charged potential of In response to passing the position, the power source means switches the voltage applied to the transfer means from the transfer voltage to the static elimination voltage. (2) When the photoreceptor is stopped, the predetermined point on the photoreceptor that was located at the transfer position when the voltage applied to the transfer means was switched by the applied voltage switching control means The photoreceptor rotating means is controlled to rotate at least a predetermined amount to bring the developing means to a developing position. (3) After the voltage applied to the transfer means is switched by the applied voltage switching control means, the photoreceptor is located at the transfer position at least at the time when the voltage applied to the transfer means is switched. After the predetermined point on the photoreceptor reaches the charging position of the charging means and before the predetermined point on the photoreceptor, which is located at the developing position when the photoreceptor is stopped, passes the charging position, the charging means operates. to stop. (4) After the operation of the charging means is stopped by the charging control means, a predetermined point on the photoreceptor that was located at the charging position at least at the time when the operation of the charging means was stopped is moved to the developing position. After reaching this point, the operation of the developing means is stopped. (5) After a predetermined point on the photoreceptor located at the charging position when the photoreceptor is stopped passes the transfer position, and from the time when the operation of the charging means is stopped by the charging control means. Stopping the application of the neutralization voltage to the transfer means by the power supply means until a predetermined point on the photoconductor that was located at the charging position at the time when the operation of the charging means stopped reaches the transfer position. let The recording operation is stopped using various controls.

[0007]

[Operation] By taking such measures, at the end of the recording process, the voltage applied to the transfer means by the power supply means is removed from the transfer voltage in response to the trailing edge of the recording paper passing the transfer position. Switched to voltage. When the voltage applied to the transfer means is switched by the applied voltage switching control means in this manner, the predetermined point on the photoreceptor that was located at the transfer position is at least in the developing position of the developing means when the photoreceptor is stopped. The photoreceptor is rotated a predetermined amount to reach the position. In this state, after the voltage applied to the transfer means is switched as described above, at least After the predetermined point reaches the charging position of the charging means, and before the predetermined point on the photoreceptor, which is located at the developing position when the photoreceptor is stopped, passes the charging position, the operation of the charging means is stopped. . Furthermore, after the operation of the charging means has stopped in this way,
The operation of the developing means is stopped after a predetermined point on the photoreceptor that was located at the charging position at least when the operation of the charging means stopped reaches the developing position. Then, after a predetermined point on the photoreceptor located at the charging position when the photoreceptor is stopped passes the transfer position,
and as described above, from the time when the operation of the charging means stops until the predetermined point on the photoreceptor, which was located at the charging position at the time when the operation of the charging means stopped, reaches the transfer position. The application of the neutralization voltage to the transfer means by the power supply means is stopped. Therefore, when the photoreceptor starts rotating after the recording process is completed, at least the portion of the photoreceptor located between the charging position and the developing position is exposed to a predetermined charge-eliminating voltage applied to the transfer roller. It is in a state where the static electricity has been removed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of an electrophotographic recording apparatus according to this embodiment. In the figure, reference numeral 1 denotes a photosensitive drum, which is rotationally driven in the direction of arrow A in the figure by a photosensitive drum drive system 2 consisting of a motor, gears, and the like. A charging device 3, an exposure device 4, a developing device 5, a transfer roller 6, and a cleaning device 7 are provided around the photosensitive drum 1 and facing the photosensitive drum 1, respectively.

The charging device 3 is a well-known scorotron type charger composed of a discharger 31, a high-voltage charging power supply 32, a high-voltage Zener diode 33, and a switch 34. The exposure device 4 is, for example, a well-known laser scanner or the like that turns on/off a laser beam or the like according to image data of an image to be recorded, although the specific configuration thereof is not shown in the drawings.

The developing device 5 uses toner 51 as a developer.
A cylindrical sleeve 53 containing a built-in magnet (not shown) is provided at the opening of the hopper 52 in which the liquid is stored, with a portion of the sleeve located inside the hopper 52. The sleeve 53 is configured to be turned on/off by a switch 54 and a high voltage generated by a high voltage power source 55 for developing bias is applied. Note that 56 is a blade for keeping the amount of toner 51 carried by the sleeve 53 and guided to the outside of the hopper 52 constant.

The transfer roller 6 is made of a material such as rubber or sponge that has a certain degree of elasticity and is semiconductive, and does not come into contact with the photosensitive drum 1 when no recording paper is supplied. In addition, when the recording paper is supplied, the recording paper is held together with the photosensitive drum 1. The transfer roller 6 is connected via a switch 61 to a power source 62 that generates a predetermined potential V1 having a polarity opposite to the charged potential of the photosensitive drum 1 or to the ground.

Although the specific structure of the cleaning device 7 is not shown, it is a well-known device that is configured to scrape off the toner 51 adhering to the photosensitive drum 1 using, for example, a plate-like member. .

Reference numeral 8 denotes a control section for overall control of the present electrophotographic recording apparatus, which controls the photosensitive drum drive system 2 and controls the switch 34.
, 54, 61, and other parts. Note that 9 is a recording paper, and 10 is a registration roller.

Next, the operation of the electrophotographic recording apparatus constructed as above will be explained. Here, the charging position in the charging device 3, the exposure position in the exposure device 4, the developing position in the developing device 5, and the transfer position in the transfer roller 6 are shown in FIG.
Point A, point B, point C, and point D are shown in the figure. Also, at a certain point in time, the photosensitive drum 1 located at point A
T1 is the time it takes for a certain point to move to point B, T2 is the time it takes for a certain point on photosensitive drum 1 located at point B to move to point C, and T2 is the time it takes for a certain point on photosensitive drum 1 located at point B to move to point C. Let T3 be the time it takes for a certain point to move to point D, and T4 be the time it takes for a certain point on the photosensitive drum 1 located at point D to move to point A. Then, the time required for the photosensitive drum to rotate once, that is, T1+T2+T3+T4, is T5.
shall be.

First, when a control unit of a facsimile machine or the like to which the present electrophotographic recording device is applied instructs to start a recording operation, the control unit 8 causes the photosensitive drum drive system 2 to rotate the photosensitive drum 1. photosensitive drum 1.
(time point TA in Figure 3). The control unit 8 turns on the switch 34 at the same time as the photosensitive drum 1 starts rotating, and applies negative high voltage generated by the power source 32 to the discharger 31 . As a result, discharge occurs from the discharger 31, and the photosensitive drum 1 is charged to a uniform potential.

[0016] Subsequently, the control unit 8 controls [T1+
T2], the switch 54 is turned on and the high voltage generated by the developing bias high voltage power supply 55 is applied to the sleeve 53 (time TB in FIG. 3). As a result, a developing bias is applied to the sleeve 53, and the sleeve 53 becomes ready for development.

Furthermore, the control section 8 starts the exposure process and conveyance of the recording paper 9 to perform recording after a time period of T3 or more has elapsed from the time TB. Then, the switch 61 is switched to the power source 62 side when the leading edge of the recording paper 9 reaches the transfer position D and the paper passing through the transfer position D becomes "present" (time TC in FIG. 3). In addition, until now, switch 6
1 is in an open state.

Thus, first, the photosensitive drum 1 is charged by the charging device 3.
After being charged to a uniform potential (for example, about -700V), the exposure device 4 performs an exposure process. In this example, a reversal development method is used, and the exposure process is "black".
indicates exposure, and "white" indicates non-exposure. As a result, the charged electric charge is grounded at a portion of the photosensitive drum 1 corresponding to the "black" portion, and the potential thereof becomes, for example, about -100 V. When the exposed portion of the photosensitive drum 1 reaches the development position, toner 51 is attached to the photosensitive drum 1. This is due to the rotation of the magnet provided in the sleeve 53 and the toner 51.
The toner 51, which is negatively charged due to the movement of the toner 51, adheres to the photosensitive drum 1 due to the action of the developing bias, but the exposed area of the photosensitive drum 1 has a potential of -100 V as described above. The toner 51 adheres because the potential is lower than the developing bias (for example, -550 V). In addition, the potential of the unexposed portion of the photosensitive drum 1 is, for example, about -680 V (slightly lowered due to dark decay), which is higher than the developing bias of -550 V, so the toner 51 is repelled. and does not adhere to the photosensitive drum 1. Therefore, the toner 51 is attached only to the exposed portion of the photosensitive drum 1, that is, the portion corresponding to "black", and development is performed.

As described above, the toner 51 attached to the photosensitive drum 1 through the development process is transferred onto the recording paper 9 by the electric field caused by the voltage V1 applied to the transfer roller 6, and recording is performed.

After that, the photosensitive drum 1 is charged again by the charging device 3 after the toner 51 remaining without being transferred is removed by the cleaning device 7 . At this time, the photosensitive drum 1 has a part with a potential of about -680 V and a part with a potential of -1
However, due to this recharging, the part that had a potential of about -680 V becomes about -750 V, and the part that had a potential of about -100 V changes to about -750 V. It is charged to about -700V. In this way, there are some variations in the potential of the photosensitive drum 1 during recharging, but these both change to -100 when exposed to light.
The potential becomes about V. Therefore, this degree of potential variation has no effect on the quality of the image, and it is possible to perform high-quality recording even after this.

After the recording is completed as described above, the control section 8 stops the recording operation in the following procedure. That is, first, the trailing edge of the last recording paper field passes through the transfer position D, and the time when the paper passing at the transfer position D becomes "no" (Fig. 3
At the middle TD time point), the control section 8 switches the switch 61 to the ground side. As a result, the transfer roller 6 is grounded. At this time, since there is no paper passing through the transfer position D, the transfer roller 6 is in contact with the photosensitive drum 1. Therefore, the photosensitive drum is grounded via the transfer roller 6, and the electric charge on the photosensitive drum 1 is removed.

[0022] Subsequently, the control unit 8 starts [T4] from the TD point.
When the time has elapsed, the switch 34 is turned off, and the discharge from the discharger 31, that is, the charging process is stopped (time TE in FIG. 3). That is, the charging process is stopped when the position that was located at the transfer position D at the time TD when the transfer roller 6 was grounded, that is, the position where static elimination in the photosensitive drum 1 was started, reaches the charging position A. Therefore, photosensitive drum 1
A portion of the photosensitive drum 1 before the position where static elimination is started is uniformly charged, and a portion of the photosensitive drum 1 after the position where static elimination is started is statically eliminated.

[T1+T2
] The operation of the developing device 5 is stopped when the time has elapsed (time TI in FIG. 3). That is, the development process is stopped when the position that was located at the transfer position D at the time TD when the transfer roller 6 was grounded, that is, the position where the charge removal in the photosensitive drum 1 was started, reaches the development position C. Therefore, during the period when the portion of the photosensitive drum 1 before the position where static elimination is started, that is, the portion that is uniformly charged, passes the development position C, the developing bias is in an ON state, and the photosensitive drum 1 is in an ON state. Potential (e.g. -700 V or -750 V)
The toner 51 does not adhere to the photosensitive drum 1 due to the potential difference between the developing bias potential (for example, -550 V). Further, the portion of the photosensitive drum 1 behind the position where static elimination is started, that is, the portion where static elimination has been performed, is at the development position C.
During the period during which the toner 51 passes through, the developing bias is turned off, and the toner 51 does not adhere to the photosensitive drum 1.

After that, the control unit 8 controls [T3
] has elapsed, that is, from the time TD when the transfer roller 6 touches the ground, the time [T5] has elapsed (
At time TG in FIG. 3), the switch 61 is opened. In this way, the photosensitive drum 1 is in a state where the entire circumference is neutralized. Then, the control unit 8 instructs the photosensitive drum drive source 2 to stop driving the photosensitive drum 1 at an arbitrary time TH after this TG time. In response to this, the photosensitive drum drive source 2 stops driving the photosensitive drum 1. After the photosensitive drum 1 stops driving, it rotates slightly due to inertia and then stops (time TI in FIG. 3).

When the photosensitive drum 1 is stopped in this manner, the entire circumference of the photosensitive drum 1 is in a state of being neutralized as described above, and regardless of the timing at which the photosensitive drum 1 stops, the charging position and the developing position are The portion located between is in a static neutralized state. Therefore, the toner 51 does not adhere to the photosensitive drum 1 even in the stopped state. Furthermore, even at the start of the next recording operation, since there is no part of the photosensitive drum 1 where the potential is unstable, toner 51 does not adhere.

By the way, here, the transfer roller 6 is grounded when removing the static electricity from the photosensitive drum 1.
If the photosensitive drum 1 is simply grounded in this manner, the charge on the photosensitive drum 1 may not be completely removed depending on the characteristics of the photosensitive drum 1, the charging potential of the photosensitive drum 1, and other conditions. In such cases, it is best to do the following: That is, as shown in FIG.
2 and a power source 63 can be selected. Here power supply 6
3 generates a predetermined voltage V2 having a polarity opposite to that of the charged potential of the photosensitive drum 1 and having a small absolute value.

As a result, when the switch 61 selects the power source 63, the electric charges on the photosensitive drum 1 are actively canceled out and removed by the voltage V2 that the power source 63 applies to the transfer roller 6. be done. Therefore, reliable static elimination can be performed. However, the value of the voltage V2 needs to be optimally set according to the characteristics of the photosensitive drum 1, the charging potential of the photosensitive drum 1, and other conditions. This is because if the voltage V2 is low, sufficient charge removal cannot be performed, and if the voltage V2 is high, the photosensitive drum 1 will be charged.

As described above, according to this embodiment, by switching the voltage applied to the transfer roller 6 to a predetermined voltage at the time of transfer and at the time of stopping the recording operation, the transfer roller 6 eliminates static electricity from the photosensitive drum 1. It is possible to do so. As a result, the static eliminator can be eliminated, and device cost, power consumption, and size can be reduced.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the period during which the transfer roller 6 is grounded, that is, the period during which static electricity is removed, is set to 1 on the photosensitive drum 1.
The period of rotation is T5, and the photosensitive drum 1 is stopped with static electricity removed from the entire circumference of the photosensitive drum 1. When the photosensitive drum 1 is stopped, the photosensitive drum 1 moves from the charging position A to the developing position C.
It suffices that at least the portion located between them is neutralized, and the period during which the transfer roller 6 is grounded and the stop timing of the photosensitive drum 1 may be set so as to satisfy this condition.

Further, although the above embodiments illustrate a reversal development method, it is also applicable to a normal rotation development method. Further, in the above embodiments, a drum-shaped endless photoreceptor is exemplified, but a belt-shaped one may also be used. In addition, various modifications can be made without departing from the gist of the present invention.

[0031]

Effects of the Invention The present invention provides an endless photoconductor such as a photoconductor drum made of a photosensitive conductive member, a photoconductor rotation means such as a photoconductor drive system for rotating the photoconductor, and a photoconductor rotating means such as a photoconductor drive system for rotating the photoconductor, and A charging means is provided facing the body and charges the photoreceptor to a predetermined charging potential, and the photoreceptor charged by the charging means is exposed to light in accordance with the image to be recorded, and the photoreceptor is electrostatically charged. An exposure means for forming a latent image, and a developer is attached to the electrostatic latent image formed on the photoreceptor by the exposure means by a developing bias of a predetermined potential having the same polarity as the charging potential and lower than the charging potential. a developing means, which is in contact with the photoreceptor, and when a recording paper is being supplied, the recording paper is held together with the photoreceptor, and the developing means is attached to the photoreceptor with respect to the recording paper; A transfer means such as a transfer roller that transfers the agent, and a transfer voltage of a predetermined voltage for transfer processing for this transfer means or a charging potential of the photoreceptor at a transfer position where transfer processing is performed by the transfer means. and a power supply means for selectively applying a static elimination voltage of a predetermined voltage, such as a ground potential, having a small absolute value, and at the end of the recording process: (1) when the trailing edge of the recording paper has passed the transfer position; Accordingly, the voltage applied to the transfer means by the power supply means is switched from the transfer voltage to the neutralization voltage. (2) When the photoreceptor is stopped, the predetermined point on the photoreceptor that was located at the transfer position when the voltage applied to the transfer means was switched by the applied voltage switching control means The photoreceptor rotating means is controlled to rotate at least a predetermined amount to bring the developing means to a developing position. (3) After the voltage applied to the transfer means is switched by the applied voltage switching control means, the photoreceptor is located at the transfer position at least at the time when the voltage applied to the transfer means is switched. After the predetermined point on the photoreceptor reaches the charging position of the charging means and before the predetermined point on the photoreceptor, which is located at the developing position when the photoreceptor is stopped, passes the charging position, the charging means operates. to stop. (4) After the operation of the charging means is stopped by the charging control means, a predetermined point on the photoreceptor that was located at the charging position at least at the time when the operation of the charging means was stopped is moved to the developing position. After reaching this point, the operation of the developing means is stopped. (5) After a predetermined point on the photoreceptor located at the charging position when the photoreceptor is stopped passes the transfer position, and from the time when the operation of the charging means is stopped by the charging control means. Stopping the application of the neutralization voltage to the transfer means by the power supply means until a predetermined point on the photoreceptor that was located at the charging position at the time when the operation of the charging means stopped reaches the transfer position. let The recording operation is stopped using various controls. This allows image recording in an electrophotographic process without providing a static eliminator, resulting in an inexpensive, compact, and low power consumption electrophotographic recording apparatus.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an electrophotographic recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the positions of the photosensitive drum 1 where each process of electrophotography is performed.

FIG. 3 is a timing chart showing operation timing.

FIG. 4 is a diagram showing a main part configuration in a modified example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Photosensitive drum drive system, 3... Charging device, 4... Exposure device, 5... Developing device, 6... Transfer roller, 61
...Switch, 62, 63...Power source, 7...Cleaning device, 8...Control unit, 9...Recording paper, 10...Registration roller.

Claims (3)

[Claims] 1. An endless photoconductor made of a photosensitive conductive member, a photoconductor rotation means for rotating the photoconductor, and a photoconductor rotating means provided opposite to the photoconductor, the photoconductor being charged at a predetermined charging potential. a charging device for charging the photoconductor, an exposing device for exposing the photoconductor charged by the charging device to light in accordance with an image to be recorded, and forming an electrostatic latent image on the photoconductor; a developing means for applying a developer to the electrostatic latent image formed on the electrostatic latent image by applying a developing bias of a predetermined potential having the same polarity as the charging potential and lower than the charging potential; A transfer means that holds the recording paper together with the photoreceptor when being supplied and transfers the developer adhered to the photoreceptor by the developing means to the recording paper; and a transfer process for the transfer means. a power source means for selectively applying a transfer voltage of a predetermined voltage for recording or a predetermined static elimination voltage of a predetermined voltage smaller in absolute value than the charged potential of the photoreceptor at the transfer position where the transfer process is performed by the transfer means; applied voltage switching control means for switching the voltage applied to the transfer means by the power supply means from the transfer voltage to the neutralization voltage in response to the trailing edge of the recording paper having passed the transfer position at the end of processing; When the photoreceptor is stopped, the predetermined point on the photoreceptor that was located at the transfer position when the voltage applied to the transfer means was switched by the applied voltage switching control means is at least the developing point. After the voltage applied to the transfer means is switched by the photoreceptor rotation control means for controlling the photoreceptor rotation means to rotate the photoreceptor rotation means by a predetermined amount to bring the photoreceptor to the developing position of the means, and the applied voltage switching control means, at least the After the predetermined point on the photoreceptor, which was located at the transfer position at the time when the voltage applied to the transfer means was switched, reaches the charging position of the charging means,
and charging control means for stopping the operation of the charging means before a predetermined point located at the developing position on the photoreceptor passes the charging position when the photoreceptor is stopped; and the charging means is controlled by the charging control means. After the operation of the charging means is stopped, the operation of the developing means is stopped at least after a predetermined point on the photoreceptor that was located at the charging position at the time when the operation of the charging means was stopped reaches the developing position. development control means for stopping the development; and after a predetermined point on the photoreceptor located at the charging position when the photoreceptor is stopped passes the transfer position, and the operation of the charging means is stopped by the charging control means. A static elimination voltage is applied to the transfer means by the power supply means during the period from the time when the charging means stops operating until the predetermined point on the photoconductor that was located at the charging position reaches the transfer position. 1. An electrophotographic recording apparatus comprising: voltage application stop control means for stopping application of voltage. 2. The power source means applies a predetermined voltage having a polarity opposite to the charged potential of the photoreceptor at the transfer position where the transfer process is performed by the transfer means as a neutralizing voltage to the transfer means. 1. The electrophotographic recording device according to 1. 3. The electrophotographic recording apparatus according to claim 1, wherein the power supply means sets the ground potential to a neutralizing voltage by grounding the transfer means.