JPH05119553A - Electrophotographic recorder - Google Patents

Abstract

PURPOSE:To prevent soiling of the back of a record sheet. CONSTITUTION:The number of record sheets is counted by a record sheet counting means 13a. When the number of the record sheets reaches the specified value, a transfer roller cleaning control means 13b makes a record sheet carrying motor 15 to rotate, thereby rotating a sheet feed roller 11 and a regist roller 12, and passing the sheet of record paper P through a transfer position between a photosensitive drum 1 and a transfer roller 50.

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 an image by an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, as one of electrophotographic recording apparatuses, there is an electrophotographic recording apparatus to which a contact transfer system is applied for transfer processing. The contact transfer method is a method in which transfer is performed by a transfer device (for example, a transfer roller) disposed in contact with the photoconductor.

Normally, the image formation on the photoconductor and the conveyance of the recording paper are in a synchronous relationship, and only during the period when the recording paper exists between the photoconductor and the transfer roller (hereinafter referred to as a transfer position). The image formed on the photoconductor reaches the transfer position. Therefore, no toner should adhere to the transfer roller.

However, in reality, a small amount of toner adheres to the photoconductor even in the non-recording area. When such toner, so-called fog toner, reaches the transfer position, there is no recording paper at the transfer position and the photoconductor and the transfer roller are in contact with each other. As a result, the toner adheres to the transfer roller. Specifically, in the case of the reversal development method, the non-recording area of the photoconductor is, for example, -500V. Therefore, the toner charged to the same polarity (negative polarity) and having a developing bias of, for example, -200 V, does not adhere to the photoconductor because the photoconductor side has a wide potential. By the way, the toner is negatively charged by frictional charging, but not all toners are negatively charged when charged in this way, and some toners are positively charged although a small amount. .. There are also toners that are negatively charged but have a small amount of charge. Such toner easily adheres to the non-recording area of the photoconductor.

Further, at the time of starting from the operation stopped state,
The potential of the photoconductor is indefinite, and a relatively large amount of toner adheres to the photoconductor, or when a paper jam occurs, the image remains on the photoconductor and a relatively large amount of toner adheres to the photoconductor. ing. When the portion to which the toner adheres in this way passes the transfer position, the recording paper does not exist at the transfer position, so the toner adheres to the transfer roller.

The toner thus attached to the transfer roller is gradually accumulated on the transfer roller, and eventually the toner is attached to the back surface of the recording paper passing through the transfer position. As a result, the back surface of the recording paper is smeared.

[0007]

As described above, in the conventional electrophotographic recording apparatus, when the contact transfer system is applied, the toner adheres to the transfer device such as the transfer roller and the back side of the recording paper is not adhered. There was a problem of causing dirt.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrophotographic recording apparatus capable of preventing back stains on a recording paper. is there.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a recording amount is counted from, for example, the number of recording sheets, and at least one recording sheet is recorded, for example, in a recording sheet cassette, when the counted recording amount exceeds a predetermined amount. The recording paper is stored in the recording paper storage section and is passed between a photoconductor such as a photoconductive drum and a transfer device such as a transfer roller.

[0010]

By taking such means, each time a predetermined amount of recording is performed, the recording paper is passed between the photoconductor and the transfer device in addition to the passing of the recording. Therefore, the toner accumulated in the transfer device adheres to the recording paper and is removed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Here, a reversal development type electrophotographic recording apparatus is exemplified.

FIG. 1 is a view showing the arrangement of an electrophotographic recording apparatus according to this embodiment. In the figure, 1 is a photosensitive drum. Around the photosensitive drum 1, a charging device 2, an exposure device 3, a developing device 4, a transfer device 5 and a cleaning device 6 are provided along the peripheral surface of the photosensitive drum 1, and these devices are well known. An electrophotographic process is performed.

By the way, the transfer device 5 includes the transfer roller 5
0, transfer power supply 51, cleaning power supply 52 and transfer switch 5
Have three. The transfer roller 50 is disposed in contact with the photosensitive drum 1, and holds and conveys the recording paper P together with the photosensitive drum 1 when the recording paper P is inserted. Transfer power source 51
Generates a transfer voltage having a predetermined voltage (for example, +1 KV) having a polarity opposite to the charging potential of the photosensitive drum 1 (toner charging potential). The cleaning power supply 52 generates a cleaning voltage having a predetermined voltage (for example, -500V) having a polarity opposite to that of the voltage generated by the transfer power supply 51. The transfer switch 53 turns ON / OFF the voltage application to the transfer roller 50 and selects the voltage (transfer voltage or cleaning voltage) applied to the transfer roller 50.

A recording paper cassette 10 stores recording papers P. The recording paper P stored in the recording paper cassette 10 is carried out by the paper feed roller 11 to the transport path formed by the guide G. A registration roller 12 corrects the skew of the recording paper P that has been conveyed along the conveyance path by the paper feed roller 11 and conveys the recording paper P to a position (transfer position) between the photosensitive drum 1 and the transfer roller 50. To do.

Reference numeral 13 is a control unit for controlling the electrophotographic recording apparatus as a whole. The control unit 13 includes a charging device 2,
In addition to the exposure device 3, the developing device 4, and the transfer device 5 (transfer switch 53), the photosensitive drum motor 14, the recording paper conveyance motor 15, the image memory 16 and the character generator 17 are connected. Photosensitive drum motor 1
4 rotates the photosensitive drum 1 at a predetermined speed. The recording paper transport motor 15 includes a paper feed roller 11 and a registration roller 1.
2 and the transfer roller 50 are rotated at a predetermined speed to convey the recording paper P. The image memory 16 is a memory capable of storing at least one page of image data. The character generator 17 generates pattern data of characters such as characters.

By the way, the control unit 13 is configured to have, for example, a microcomputer as a main control circuit,
In addition to the well-known general control means in the electrophotographic recording apparatus, it has a recording number counting means 13a, a transfer roller cleaning control means 13b, and a cleaning image forming means 13c. Of these, the number-of-recorded-sheet counting means 13a counts the number of recorded sheets. The transfer roller cleaning control means 13b is
The cleaning process of the transfer roller 50 is performed when the count value of the number-of-recorded-sheet counting unit 13a reaches a specified value. Further, the cleaning image creating means 13c creates predetermined image data necessary for cleaning the transfer roller.

Next, the operation of the electrophotographic recording apparatus configured as described above will be described according to the processing procedure of the control unit 13.
First, the control unit 13 waits for a recording request, as shown at step a in FIG. In this state, when image data is given from the outside and an instruction to start recording is given, the control unit 13 performs the process from step a to step b.
Move to. In step b, the control unit 13 sets 1 page to 1
Import image data as a unit. That is,
The captured image data is sequentially stored in the image memory 16. Then, when the acquisition of the image data for one page is completed, the control unit 13 shifts the processing to step c. The controller 13 performs a normal recording operation in step c. This normal recording operation is a known recording operation using the image data stored in the image memory 16. Subsequently, in step d, the control unit 13 determines whether or not the recording operation of step c has been completed normally.

If an abnormality occurs during the recording operation in step c, the controller 13 determines in step e whether or not the abnormality has occurred after the start of exposure.
If the abnormality occurs after the start of exposure, the control unit 13 adds a predetermined value M larger than 1 to the number of recorded sheets L in step f, and then shifts to step g. If the abnormality occurs before the exposure is started, the process directly proceeds to step g. If an abnormality occurs after the start of exposure, the predetermined value M is added to the number of recorded sheets L.
This is because it is considered that M sheets have been recorded because a large amount of toner adheres to the exposed area of the photosensitive drum 1 and this large amount of toner may adhere to the transfer roller 50. Therefore, it is preferable that the predetermined value M be a value of [average amount of toner attached to the photosensitive drum 1 when abnormality occurs / average amount of normal fog toner per sheet]. Then, the control unit 13 waits for the cause of the abnormality to be eliminated in step g, and when it is eliminated, returns to step c and performs the recording operation again.

On the other hand, when the recording operation in step c ends normally without any abnormality, the control unit 13 shifts the processing from step d to step h. In step h, the control unit 13 adds [1] to the number of recorded sheets L, and then proceeds to step i. Then, in step i, the control unit 13
It is determined whether or not there is a next page, and if the recording of the next page is instructed, the processes from step b are repeated to record the next page and thereafter. If there is no next page, the control unit 13 shifts the processing to step j.

When the control unit 13 completes the series of recording operations as described above, before stopping the operation of each unit and ending the processing, whether or not the number of recorded sheets L exceeds the specified value N in step j. Check that. The prescribed value N is an arbitrary value that is smaller than the number of recording sheets on which toner enough to stain the recording paper P on the transfer roller 50 is accumulated, and is set to, for example, about [1000].

Here, when the number of recorded sheets L has not reached the specified value N, the control unit 13 ends the processing as it is and stops the operation of each unit. On the other hand, if the number of recorded sheets L exceeds the specified value N, the control unit 13 performs a predetermined process of the transfer roller cleaning mode in step k, and then ends the process.

The transfer roller cleaning mode is performed as follows. That is, the control unit 13 first creates cleaning image data as shown in step l in FIG. The cleaning image data is image data corresponding to the image shown in FIG. Most of the image shown in FIG. 4 is an image non-forming area, and a message 40 indicating that the paper is for cleaning the transfer roller 50 is formed on a part of the image. The cleaning image data is created by the cleaning image creating means 13c using the character pattern generated by the character generator 17.

Subsequently, the control unit 13 at step m
Perform recording operation during cleaning. The cleaning recording operation is performed by using the cleaning image data created in step l. However, not only the recording operation is performed by using the cleaning image data, but also the operation of the transfer device 5 is different.

The operation of each unit during the cleaning recording operation will be described below with reference to FIG. First, at time T1, the photosensitive drum motor 14 starts rotating under the control of the controller 13, and the photosensitive drum 1 starts rotating in response to this. At the same time, the charging operation of the charging device 2 is turned on. Further, under the control of the control unit 13, the transfer switch 53 is connected to the cleaning power source 52.
Is selected, the voltage applied to the transfer roller 50 becomes a cleaning voltage, that is, a negative polarity.

Subsequently, at the time T2 when a predetermined time TA has elapsed from the time T1, the developing device 4 starts the developing operation under the control of the controller 13. Here, the time TA is the time required for the photosensitive drum 1 to rotate the angle from the charging position A of the charging device 2 to the developing position C of the developing device 4.

After this, the exposure apparatus 3 starts the exposure operation under the control of the control unit 13 (at the time T3 in the figure). This exposure operation is performed based on the cleaning image data. However, most of the cleaning image is the image non-forming area because the message 40 is present in a slight range on the trailing edge side of the image, and therefore the exposure of the photosensitive drum 1 is actually performed for a while even after the exposure operation is started. Is not done.

In this state, the angle from the exposure position B in the exposure device 3 to the transfer position D in the transfer device 5 is set to the photosensitive drum 1
When the time required for rotation of the
Time TB has elapsed from time 3 (time T4 in the figure)
Then, the exposure operation start point on the photosensitive drum 1 (however,
(Actual exposure has not been performed) reaches the transfer position D. The control unit 13 sets the recording paper feed motor 1 at a predetermined timing when the leading edge of the recording paper P reaches the transfer position D at time T4.
The rotation of 5 has started. Therefore, the leading edge of the recording paper P conveyed by the supply roller 11 and the registration roller 12 reaches the transfer position D at time T4. In the case of a normal recording operation, the voltage applied to the transfer roller 50 from this time T4 is the positive transfer voltage generated by the transfer power supply 51.
In the cleaning recording operation, the voltage applied to the transfer roller 50 remains the negative cleaning voltage after the time T4.

Therefore, in this state, since the negative voltage is applied to the transfer roller 50 with the recording paper P positioned at the transfer position D, the toner accumulated on the transfer roller 50 repels from the transfer roller 50. Then, the recording paper P is attached. As a result, the toner accumulated on the transfer roller 50 is cleaned.

During the period corresponding to the formation position of the message 40 (from time T5 to time T6 in the figure), the exposure device 3 actually exposes the photosensitive drum 1, and the photosensitive drum 1 receives the message 40. The electrostatic latent image of the pattern is formed. This electrostatic latent image is made visible by the developing device 4 and reaches the transfer position D.

The control unit 13 controls the photosensitive drum 1 as described above.
A predetermined period TC including a period in which the area on which the toner image is formed passes through the transfer position (from an arbitrary time point T7 before the time TB has passed from the time point T5 to a predetermined time point after the time TB has passed from the time point T6) During the period until T8), the transfer switch 53 is switched to the transfer power source 51 side, and the transfer voltage having a positive polarity is applied to the transfer roller 50. As a result, the toner image (message 40) formed on the photosensitive drum 1 is transferred onto the recording paper P.

When the cleaning recording operation detailed above is completed or is stopped due to the occurrence of an abnormality, the controller 13 determines in step n whether the cleaning recording operation is completed normally. To do.

If the cleaning recording operation is stopped due to the occurrence of an abnormality, the control unit 13 waits for the cause of the abnormality to be resolved in step o, and then proceeds to step m after the cause of the abnormality is resolved.
Repeat the recording operation during cleaning at. If the recording operation during cleaning is normally completed, the controller 13 clears the number of recording sheets L to "0" in step p, and then ends the process of the transfer roller cleaning mode.

As described above, according to this embodiment, every time the specified number of sheets (for example, 1000 sheets) are recorded, a sheet is passed for cleaning the transfer roller 50, in addition to the normal image recording. There is. Therefore, the toner accumulated on the transfer roller 50 is transferred to the recording paper P passed in this way, and the transfer roller 50 is cleaned. It should be noted that the number of recorded sheets is counted as if M sheets were recorded when an abnormality such as a paper jam occurs, and therefore has a value corresponding to the actual amount of toner adhered to the transfer roller 50. Therefore, the transfer roller 50 can be cleaned at good timing.

Further, in the present embodiment, when cleaning the transfer roller as described above, the cleaning voltage having the opposite polarity to the transfer voltage is applied to the transfer roller 50, so that the toner accumulated on the transfer roller 50 is removed. The electrostatic force transfers the toner onto the recording paper P more reliably, so that effective cleaning can be performed.

Further, according to this embodiment, the recording paper P is passed to the recording paper P for cleaning the transfer roller 50.
Since the message 50 indicating that the transfer roller 50 is for cleaning is recorded, it is possible to prevent the user from worrying about what kind of recording paper is ejected. The present invention is not limited to the above embodiment, and various modifications such as the following are possible. (1) In the above embodiment, the recording amount is counted according to the number of recording sheets, but the recording amount may be counted from other factors such as toner consumption amount.

(2) In the above embodiment, the transfer roller is cleaned before the operation is stopped after the normal recording operation is completed. However, the transfer roller is cleaned, for example, when the power is turned on. , At any time.

(3) In the above embodiment, when the sheet is passed for cleaning the transfer roller, a cleaning voltage having a polarity opposite to the transfer voltage is applied to the transfer roller. Instead of applying a voltage to the roller, the toner may be attached to the recording paper only by a mechanical contact force.

(4) In the above embodiment, when an abnormality occurs during the normal recording operation, the number of recorded sheets is counted assuming that recording of a predetermined value M has been performed. Even if there is one, the number of recorded sheets may be counted assuming that one sheet is recorded.

(5) In the above embodiment, it is shown that the recording paper is used for cleaning the transfer roller 50 on the recording paper that has been passed through to create the cleaning image and clean the transfer roller. Although the message is recorded, such a message may not be recorded.

(6) The present invention is applicable not only to the electrophotographic recording apparatus of the process described in the above embodiment,
Recording is performed by a process based on an electrophotographic process, and any application can be applied as long as transfer is performed by a contact transfer method. (7) In the above embodiment, the transfer roller 50 is used as the transfer device, but the present invention is applicable to any contact type such as a brush. In addition, various modifications can be made without departing from the scope of the present invention.

[0041]

According to the present invention, the recording amount is counted from, for example, the number of recording sheets, and at least one recording sheet is recorded in, for example, a recording sheet cassette when the counted recording amount exceeds a predetermined amount. Since the paper is supplied from the paper storage unit and passed between the photoconductor such as the photoconductor drum and the transfer device such as the transfer roller, the backside of the recording paper can be prevented from being stained. It becomes a recording device.

[Brief description of drawings]

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

2 is a flowchart showing a processing procedure of a control unit 13 in FIG.

FIG. 3 is a flowchart showing a processing procedure of a control unit 13 in a transfer roller cleaning mode.

FIG. 4 is a diagram showing an example of a cleaning image.

FIG. 5 is a time chart showing the operation timing of each part in the cleaning recording operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging device, 3 ... Exposure device, 4 ... Developing device, 5 ... Transfer device, 50 ... Transfer roller, 51 ... Transfer power supply, 52 ... Cleaning power supply, 53 ... Transfer switch, 10 ... Recording paper cassette , 11 ... Paper feed roller, 12 ... Registration roller, 13 ... Control unit, 13a ... Recorded sheet counting means, 1
3b ... Transfer roller cleaning control means, 13c ... Cleaning image forming means, 14 ... Photosensitive drum motor, 15 ... Recording paper conveying motor, P ... Recording paper.

Claims (4)

[Claims] 1. A charging unit, an exposing unit, a developing unit, and a transferring unit are arranged along the peripheral surface of a photosensitive member which is rotationally driven by the photosensitive member rotating unit, by which each processing of an electrophotographic process is performed. An image is recorded on the recording paper supplied from the recording paper storage unit, and the transfer unit is arranged so as to come into contact with the photoconductor, and transfers the recording paper supplied from the recording paper storage unit. In an electrophotographic recording apparatus including a transfer device that holds and conveys a photoconductor, at least one sheet is provided according to a counting unit that counts a recording amount and a recording amount that is counted by the counting unit exceeds a predetermined amount. 2. An electrophotographic recording apparatus comprising: an automatic paper feed control means for feeding the recording paper from the recording paper storage section and passing the recording paper between the photoconductor and the transfer device. 2. A transfer voltage generating means for applying a transfer voltage of a predetermined voltage value to the transfer device with a polarity opposite to the charging potential of the photosensitive member, and a transfer voltage generated by the transfer voltage generating means has a polarity opposite to the predetermined value. Reverse voltage generating means for generating a reverse voltage of the voltage, switching means for selectively applying the reverse voltage generated by the reverse voltage generating means and the transfer voltage to the transfer device, and the photosensitive member by the automatic paper feed control means. The electrophotographic recording apparatus according to claim 1, further comprising a voltage application control unit that selects the reverse voltage by the switching unit during a period in which the sheet is passed between the transfer unit and the transfer unit. 3. The counting means counts the recording amount according to the number of recorded sheets, and when the operation is interrupted due to an abnormality, the counting means counts as recording of a predetermined number of sheets. 1. The electrophotographic recording device according to 1. 4. An image data generating unit for generating predetermined image data, wherein a predetermined image is recorded on a recording sheet fed by the automatic sheet feeding control unit. The described electrophotographic recording device.