JP3098601B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a laser printer, etc. using an electrophotographic process. The present invention relates to an image forming apparatus that executes control of a transfer current and control of a pre-cleaning charge elimination current based on potential measurement data.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a facsimile, a laser printer, etc. using an electrophotographic process, in order to avoid a change in image quality due to a use environment, particularly, stabilization of image quality during transfer processing. As means for (1), the humidity of the use environment is detected or the resistance value of the recording paper is measured, and the transfer current is controlled based on the measured value.

[0003] As a conventional example related to this, for example,
There is an "electrophotographic recording apparatus" disclosed in JP-A-62-50782 and a "multi-transfer apparatus" disclosed in JP-A-62-287271.

To explain the gist of this conventional example, an "electrophotographic recording apparatus" disclosed in Japanese Patent Application Laid-Open No. 62-50782 has a wetness detecting means for detecting the wetness of a recording paper and an output signal from the wetness detecting means. And a control means for controlling the transfer corona charge amount based on the control signal, and the wetness detecting means comprises a resistance measuring means for measuring a resistance value of the recording paper. Japanese Patent Application Laid-Open No. 62-287271 discloses a "multi-transfer apparatus" in the vicinity of a dielectric supporting means for supporting and driving a dielectric for holding a recording sheet and conveying and guiding the recording sheet to a transfer position of a photosensitive member. A temperature or (and / or) humidity sensor for detecting the temperature or / and / or humidity prior to the copying operation, and considering the detected value and a preset reference value, the transfer current of the corona charger for transfer. Is controlled.

As a measure for improving the cleaning quality of the photosensitive member according to the present invention, for example, Japanese Patent Laid-Open No.
No. 6,687,832 entitled "Cleaning control device for image recording apparatus", and JP-A-1-29528.
No. 8 discloses a "method of cleaning a photoreceptor in an electrophotographic copying machine", the gist of which is as follows.

[0006] Japanese Patent Application Laid-Open No. 64-68783 discloses a "cleaning control device for an image recording apparatus" in which a reflection type sensor for detecting a defective cleaning state is provided before and after a transfer charger. The state of background contamination of the photoreceptor is determined based on the ratio of the output values of the two reflection-type sensors, which are positioned to face each other outside the image area. Based on this determination, the current supplied to the pre-cleaning charger is changed to prevent the photoconductor from being stained. That is, detection is performed by detection sensors arranged before and after the pre-cleaning charger, and the supply current supplied to the pre-cleaning charger is corrected.

[0007] Japanese Patent Laid-Open Publication No. 1-295288 discloses a "method of cleaning a photosensitive member in an electrophotographic copying machine".
Is to measure the pre-cleaning static elimination potential performed in the pre-cleaning process, compare it with a predetermined potential, control the output voltage of the pre-cleaning static eliminator based on the potential, and control the potential after the pre-cleaning neutralization. is there.

[0008]

However, the prior arts as shown in the above and above have problems in the following points. In a device that detects the humidity in the device and controls the transfer corona charge amount based on the detection output (Japanese Patent Application Laid-Open No. 62-287271, “Multi-Transfer Device”), the device continuously operates under high humidity environmental conditions. When the image forming process is performed, the transfer corona charge amount can be increased by increasing the transfer corona charge amount. However, since the lower portion of the stacked recording paper is substantially unaffected by humidity, excessive transfer corona charge is generated. There was a problem that it would be performed.

Therefore, an apparatus has been proposed which measures the resistance value of the recording paper and controls the transfer corona charge amount based on the measurement result (Japanese Patent Application Laid-Open No. 62-50782 "electrophotographic recording apparatus"). Since a dedicated measuring means for measuring the resistance value must be provided in the paper section, the cost of the apparatus itself is increased, and there is a problem in economy.

As a means for stabilizing the cleaning quality, the conventional apparatus for controlling the pre-cleaning processing conditions has the following problems. Japanese Patent Laid-Open Publication No. 64-68783 discloses a "cleaning control device for an image recording apparatus". When the resistance value of the recording paper changes and the transfer potential changes, the surface potential of the photosensitive member after the transfer process also changes. As a result, there is a problem that the image is adversely affected. Also, JP-A-1-295288, entitled "Method of cleaning photoreceptor in electrophotographic copying machine"
However, the method is insufficient in that it is impossible to control both the transfer condition and the condition of static elimination before cleaning.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and it is possible to economically realize a reduction in image quality due to a change in the resistance value of recording paper during continuous image forming processing, thereby achieving stable image quality. It is an object of the present invention to improve the image quality and to improve the reliability of image quality by realizing the stabilization of the photoconductor surface potential during the cleaning process and the stabilization of the toner charging state in the next transfer process.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a paper feed tray for loading recording paper and a toner image formed on a photoreceptor on the recording paper under predetermined transfer conditions. An image forming apparatus comprising: a transfer unit for performing a transfer process; and a pre-cleaning charge removing unit configured to remove a charge of the photosensitive member after cleaning the residual toner on the photosensitive member after the transfer process by the transfer unit. Humidity measuring means for measuring the humidity in the vicinity of the loaded recording paper; primary correction means for correcting the transfer conditions in the transfer means based on the humidity measured by the humidity measuring means; And a potential measuring means for sequentially measuring a surface potential of a portion of the photoconductor on which the transfer process has been completed in each transfer process or every several transfer processes. A secondary correction unit for correcting the transfer condition in the transfer unit again based on a change in the surface potential measured by the potential measurement unit, and the pre-cleaning static elimination unit based on the surface potential measured by the potential measurement unit And a pre-cleaning static elimination control means for controlling the output value of the image forming apparatus.

[0013]

The image forming apparatus according to the present invention measures the humidity near the recording paper by the humidity measuring means, detects a change in the resistance value of the recording paper from the measured value, and corrects the transfer condition corresponding to the resistance value. Execute. In addition, the recovery of the resistance value of the recording paper is detected from the post-transfer potential of the photoreceptor surface measured by the potential measuring means, an instruction for re-correction of the transfer condition is issued, and the output value of the transfer process is controlled based on the correction signal. I do.

Further, the image forming apparatus according to the present invention controls the output value of the pre-cleaning charge removal process based on the post-transfer potential value.

[0015]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to the present invention. 101 is a photosensitive drum for forming an electrostatic latent image by an electrophotographic process, 102 is a charger for charging the surface of the photosensitive drum 101 by a corotron method prior to exposure processing, and 103 is an optical system (not shown). And 104, a developing unit for containing toner and adhering (developing) the toner to the electrostatic latent image on the photosensitive drum 101 formed by the exposure process by the magnetic brush roller 104a. A transfer belt for transferring the toner image on the photosensitive drum 101 to the recording paper surface, a transfer charger 106 for performing a corona discharge from the inside of the transfer belt 105, and a toner 107 remaining on the photosensitive drum 101 after the transfer process is completed A cleaning unit 108 for collecting and processing with a fur brush and a cleaning blade is provided before the cleaning processing. Toner and the photosensitive drum 101 and the precleaning charger to perform corona discharge in order to reduce the suction force (hereinafter, PCC
Reference numeral 109 denotes a potential sensor which is disposed opposite to the surface of the photosensitive drum 101, reads the surface potential of the surface, and feeds it back to the control system.

Reference numeral 110 denotes a registration roller that conveys recording paper at a predetermined timing so as to match the leading end of the toner image formed on the photosensitive drum 101. Reference numeral 111 denotes a paper feed tray on which recording paper is stacked and set. , 112 are feed rollers that feed the top sheet of the feed tray 111 one by one.
Is a humidity sensor disposed near the paper feed roller 112 to detect humidity.

In the above configuration, the basic operation of this embodiment will be described by taking as an example a case where copying processing is performed by a copying machine. First, a copy process is started by depressing a print start key of an operation unit (not shown) provided at an upper part of the copying machine. The original to be copied is illuminated by an optical system (not shown). The reflected light (image light) obtained by illuminating the original is projected (exposed) onto the surface of the photosensitive drum 101 by a lens and a mirror (not shown). Thereby, the photosensitive drum 101
Reflected light corresponding to the image of the document is projected onto the surface, and the charges in the projected portion are erased by the intensity of the reflected light, thereby forming an electrostatic latent image. The electrostatic latent image is subsequently subjected to development processing (toner attachment processing by the development process) by the magnetic brush roller 104a of the development unit 104,
A toner image is formed on the photosensitive drum 101.

The recording paper conveyed by the paper feed roller 112 is conveyed to the photosensitive drum 101 in a timely manner so as to match the leading end of the toner image formed on the photosensitive drum 101 by the registration roller 110. You.
Further, the recording paper fed by the registration roller 110 is attracted to the transfer belt 105 and is
1 is transferred to the transfer section.

The transfer charger 106 applies an electric charge having a polarity opposite to that of the toner to transfer the toner image formed on the photosensitive drum 101 onto the recording paper conveyed by the registration roller 110. After completion of the transfer process, the recording sheet is sent to a fixing unit (not shown), where the fixing process is performed, and then the sheet is discharged out of the apparatus, thereby completing a series of processes.

The photosensitive drum 101 after the transfer process
, A pre-cleaning charge removal process is performed by the PCC 108, and subsequently, the residual toner is removed by the fur brush and the cleaning blade that constitute the cleaning unit 107. Further, the photosensitive drum 101 is initialized by erasing residual charges by a discharging lamp (not shown), and is in a standby state until a next image processing command is issued.

FIG. 2 is an enlarged explanatory view of the transfer section shown in FIG. The potential of the surface of the photosensitive drum 101 after the transfer processing changes due to corona discharge of the transfer charger 106. For example, as shown in the figure, in an image forming process using a toner of a negative polarity, a transfer corona of a positive polarity is applied. In this case, the surface potential of the non-image portion (background portion) of the photosensitive drum 101 is about 0 V during the development processing.
However, when the toner image is transferred onto the recording paper by corona discharge of the transfer charger 106, the photosensitive drum 101 is charged by leaking in the recording paper, so that the surface potential after the transfer processing has a positive polarity. That is, when the resistance value of the recording paper changes in this manner, the amount of leaked electric charge changes, so that the surface potential after the transfer processing changes. In the present invention, focusing on the change in the surface potential, the surface potential of the photosensitive drum 101 after the transfer process (hereinafter, referred to as a post-transfer potential) is detected by the potential sensor 109, and the recording paper is detected based on the detected potential value. The change in the resistance value is detected.

FIG. 3 is a graph showing the relationship between the number of recording paper layers and the water content. This graph shows that the operating environment is high temperature and high humidity (30 ° C, 90% RH) and low temperature and low humidity (10
(° C., 30% RH) shows the water content (%) of the recording paper when the humidity of the recording paper was adjusted. From this graph, it is clear that among the recording papers stacked on the paper feed tray 111, the upper recording paper is easily affected by humidity. This remarkably shows that the water content characteristic which affects the transfer efficiency changes. This change in the water content results in a change in the resistance value. For example, when the use environment of the apparatus is high humidity, the recording paper has a low resistance value, and conversely, when the humidity is low, the recording paper has a high resistance value. The recording paper stacked on the lower side of the paper feed tray 111 is hardly affected by humidity, and thus has a resistance value at normal humidity. In this way, the recording paper depends on the humidity.
The resistance value fluctuates. Next, the resistance value and the transfer characteristic of the recording paper will be described with reference to FIG.

FIG. 4 is a graph showing the relationship between the resistance value of the recording paper and the transfer potential. This graph shows the relationship between the resistance value (Ω) of the recording paper and the transfer potential (kV) between the transfer belt 105 formed by the transfer charger 106 and the toner image. From this graph, it can be seen that when the resistance of the recording paper decreases when a transfer electric field is formed between the transfer belt 105 and the toner image by the transfer charger 106 having a constant output current value, the amount of leaked charge increases and the transfer potential decreases. You can see. Therefore, when the resistance value of the recording paper decreases, the output value of the transfer charger 106 is increased, thereby preventing the transfer potential from lowering.

FIG. 5 is a block diagram showing a control system of the image forming apparatus according to the present invention. In the figure, reference numeral 501 denotes a transfer current correction value storage circuit for storing correlation data of a correction amount of a transfer current corresponding to the humidity detected by the humidity sensor 113, and reference numeral 502 denotes a first copy (first copy) at high humidity. A post-transfer potential reference value storage circuit for storing a reference value of a ratio between the post-transfer potential and the post-transfer potential in continuous copying under high humidity;
03 is a comparison circuit for comparing the data stored in the transfer current correction value storage circuit 501 with respect to the humidity detected by the humidity sensor 113, and 504 is stored in the post-transfer potential reference value storage circuit 502 for the potential value detected by the potential sensor 109. A comparison circuit 505 for comparing with data, a transfer current control circuit 505 for controlling a transfer current based on output signals of the comparison circuits 503 and 504, and a reference numeral 506 is applied to the transfer charger 106 based on a control signal of the transfer current control circuit 505. This is a transfer power pack that supplies a high voltage.

A PCC potential correction value storage circuit 507 stores correlation data between the surface potential of the photosensitive drum 101 after the transfer process and the surface potential of the photosensitive drum 101 after the static elimination process before cleaning by the PCC 108. Potential value after transfer processing detected by potential sensor 109 and PCC
A comparison circuit 509 compares the data stored in the potential correction value storage circuit 507 with a data stored in the potential correction value storage circuit 507. A control circuit 509 controls a current supplied to the PCC 108 based on an output signal of the comparison circuit 508.
PCC control circuit for performing output control of power pack for power supply 510, PC 510 for supplying a high voltage to be applied to PCC 108 based on a control signal from PCC control circuit 509
This is a power pack for C.

The transfer current correction value storage circuit 501
And a comparison circuit 503 as a primary correction means 511, and a block formed of the post-transfer potential reference value storage circuit 502 and the comparison circuit 504 as a secondary correction means 51.
Let it be 2. Further, a block including the PCC potential correction value storage circuit 507 and the comparison circuit 508 is referred to as a PCC correction unit 513.

With respect to the control system configured as described above,
This will be described with reference to FIGS. FIG. 6 is a graph showing a transfer corona current with respect to humidity according to the present invention. As shown in the relationship of this graph, the transfer corona current of the transfer charger 106 is corrected by the primary correction unit 511 based on the humidity detected by the humidity sensor 113. That is, the transfer current correction value storage circuit 501 to the transfer current control circuit 505
The first copy (first copy) is executed by controlling the transfer current as shown in FIG.

FIG. 7 is a graph showing post-transfer potential data after the transfer process according to the present invention. As described above, the surface potential of the photosensitive drum 101 after the transfer process at the time of the first copy is measured by the potential sensor 109, and the minimum value of the measured potential value is determined as the potential of the non-image portion (white portion). It is stored in the potential reference value storage circuit 502. Then, at the time of continuous copying, the photosensitive drum 101 is provided every time or every several sheets.
Is similarly measured after the transfer. By comparing the potential value at the time of continuous copying with the potential value at the time of the first copy by the comparing circuit 504, recovery of the resistance value of the recording paper is detected, and the output current value of the transfer charger 106 is again transferred to the transfer current control circuit. 505 is controlled.

FIG. 8 is a graph showing the relationship between the change in the resistance value of the recording paper and the post-transfer potential according to the present invention. The graphs indicated by the dashed lines a and b show the values at normal humidity and high humidity (80%
This is a characteristic with respect to transfer conditions after correction at the time of (RH). Point A0 indicates the post-transfer potential at the time of first copy in normal humidity, and point B indicates the post-transfer potential at the time of first copy at high humidity (80% RH). When the resistance of the recording paper recovers to the resistance at normal humidity by continuous copying, point B moves to point A1. The detection ratio of the potential value at this time is VA1
/VB=0.75, and this detection ratio is stored as a reference value. When the detection ratio reaches the reference value, the correction of the transfer condition is canceled to move the point A1 to the point A0. The reference value (ratio) can be set in advance for each correction, such as 0.75 for correction at 80% RH and 0.5 for correction at 70% RH. Corresponding.

FIG. 9 is a graph showing an output control example of the pre-cleaning charger (PCC) 108 according to the present invention. The surface potential of the photosensitive drum 101 after the transfer process changes due to the change in the resistance value of the recording paper. This change in potential also affects the process conditions during the cleaning process.
That is, when the surface potential of the photosensitive drum 101 after the transfer process changes while the condition of the PCC 108 is constant, the PCC 108
, The residual toner charge amount after the transfer process changes, and the cleaning performance (efficiency) changes. Therefore, in the present invention, the surface potential of the photosensitive drum 101 after transfer is measured by the potential sensor 109, and control processing by the PCC potential correction value storage circuit 507 and the comparison circuit 508 is executed based on the measured potential value. The output value of the PCC 108 is controlled by the PCC control circuit 509 so as to keep the input condition of the residual toner to the cleaning unit 107 constant.

Further, in the above embodiment, the transfer belt 105 and the transfer charger 106 are used as the transfer processing means, but instead, a configuration for applying a voltage to a well-known transfer roller is adopted, and the supply voltage is similarly set. May be controlled.

In this embodiment, a copying machine has been described as an example of an image forming apparatus. However, the present invention is not limited to this, and can be applied to a facsimile or laser printer using an electrophotographic process. You can do it.

[0033]

As described above, according to the image forming apparatus of the present invention, the humidity near the recording paper is measured, and the transfer processing conditions are corrected based on the resistance value of the recording paper corresponding to the humidity. Further, since the recovery of the resistance value of the recording paper is detected based on the surface potential after the transfer process and the transfer condition is re-corrected, the continuous image forming process in a high-humidity environment is performed.
Optimal transfer conditions are always obtained, and economically stable image quality can be obtained.

Further, according to the surface potential after the transfer processing,
In order to control the output value of pre-cleaning static elimination, changes in the input toner state to the cleaning device due to changes in the resistance value of the recording paper are eliminated, stabilizing the cleaning performance and improving reliability at the same time. It becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a partially enlarged view showing a transfer unit in the image forming apparatus shown in FIG.

FIG. 3 is a graph showing the relationship between the number of sheets of recording paper and the water content thereof.

FIG. 4 is a graph showing a relationship between a resistance value of a recording sheet and a transfer potential.

FIG. 5 is a block diagram showing a control system of the image forming apparatus according to the present invention.

FIG. 6 is a graph showing transfer corona current with respect to humidity according to the present invention.

FIG. 7 is a graph showing post-transfer potential data after a transfer process according to the present invention.

FIG. 8 is a graph showing the relationship between the change in the resistance value of the recording paper according to the present invention and the potential after transfer.

FIG. 9 shows a pre-cleaning charger (PC) according to the present invention.
It is a graph which shows the example of output control of C).

[Explanation of symbols]

Reference Signs List 101 photosensitive drum 106 transfer charger 109 potential sensor 113 humidity sensor 501 transfer current correction value storage circuit 502 post-transfer potential reference value storage circuit 503 comparison circuit 504 comparison circuit 505 transfer current control circuit 507 PC
C potential correction value storage circuit 508 Comparison circuit 509 PC
C control circuit 511 Primary correction means 512 Secondary correction means 513 PCC correction means

Continuation of the front page (56) References JP-A-63-298379 (JP, A) JP-A-57-99675 (JP, A) JP-A-3-8884 (JP, A) JP-A-2-284183 (JP) JP-A-59-86686 (JP, A) JP-A-2-17885 (JP, A) JP-A-64-68783 (JP, A) JP-A-4-1790 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/14-13/16 G03G 15/00 303 G03G 15/14-15/16 103 G03G 15/36 G03G 21/00 370-540 G03G 21/02 -21/08 G03G 21/14 G03G 21/20

Claims (1)

(57) [Claims] A sheet feed tray on which recording paper is stacked; a transfer means for transferring a toner image formed on a photosensitive member onto the recording paper under predetermined transfer conditions; An image forming apparatus comprising: a pre-cleaning static elimination means for neutralizing the photoconductor before cleaning residual toner on the body; a humidity measuring means for measuring humidity near the recording paper stacked on the paper feed tray; A primary correction unit that corrects a transfer condition in the transfer unit based on the humidity measured by the humidity measurement unit; and a primary correction unit that is disposed in front of the pre-cleaning static elimination unit and that has completed the transfer process on the photoconductor. A potential measuring means for sequentially measuring the surface potential in each transfer processing or every several transfer processings; and a change in the surface potential measured by the potential measuring means. Secondary correction means for correcting the transfer conditions in the transfer means again based on the transfer means; and pre-cleaning charge removal control means for controlling the output value of the pre-cleaning charge removal means based on the surface potential measured by the potential measurement means. An image forming apparatus comprising: