JP5106838B2 - Image forming apparatus and control method thereof - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and more particularly to an image forming apparatus that adjusts a potential level of an image carrier such as a photosensitive drum and a control method thereof.

  In general, in an image forming apparatus, after the surface of a photosensitive drum as an image carrier is uniformly charged, the photosensitive drum is exposed in accordance with image data to form an electrostatic latent image on the photosensitive drum. . Thereafter, the electrostatic latent image is developed with toner to form a toner image, and the toner image formed on the photosensitive drum is transferred onto a recording sheet by a transfer roller. Then, the recording paper is conveyed to the fixing unit, and the toner image is fixed on the recording paper.

  By the way, as a charging method for charging the surface of the photosensitive drum described above, a scorotron method using corona discharge (see, for example, Patent Document 1), a conductive elastic roller in contact with the photosensitive drum, and a portion near the nip. There is a roller system using near discharge. These methods have a detrimental effect that ozone is generated because the discharge phenomenon is used to ensure the uniformity of charging.

The ozone generated in this way can be removed by using an ozone filter, but it is desirable to suppress the ozone generation itself so as not to put a burden on the ozone treatment. As one method for suppressing the generation of ozone, a method of stopping charging at the time of non-printing is employed. The non-printing time is the time from the end of printing of the preceding recording paper to the start of printing of the succeeding recording paper on successive recording papers, but a period based on on / off of the registration sensor that detects the front and rear edges of the recording paper The inner time can also be used.
JP 2004-163457 A

  However, when the above-described method for stopping charging at the time of non-printing is employed, there is a phenomenon that fog occurs in the first half of the recording paper, particularly in a low temperature environment. This phenomenon is considered to be caused by a decrease in the mobility of the carrier in the photosensitive layer in a low temperature environment, and the carrier generated by the static elimination light stays in the photosensitive layer and lowers the potential during recharging. This phenomenon is greatly affected as the time of exposure to static elimination light increases.

  The present invention has been made to solve the above-described problems of the prior art, and provides an image forming apparatus capable of preventing the generation of fog while suppressing the generation of ozone, and a control method thereof. Objective.

An image forming apparatus according to a first aspect of the present invention includes a rotating image carrier, a charger for charging the image carrier, and a downstream side of the charger in the rotation direction of the image carrier. In an image forming apparatus having a static eliminator for neutralizing an image carrier, and a control unit for individually controlling on / off of the charger and the static eliminator, the control unit is provided for two recording sheets to be printed continuously. After turning off the charger based on the detection of the trailing edge of the first sheet, a timer related to the time required for the photosensitive drum to rotate from the charger to the position of the static eliminator is started, and the timer has passed the time. Or if it is determined whether the leading edge of the second sheet in the recording sheet has been detected, and if it is determined that the leading edge of the second sheet has been detected, the second sheet is printed after clearing the timer. The timer is When it is determined that the recording time has elapsed, the static eliminator is turned off, and the static eliminator of the image carrier that has been neutralized by the static eliminator is not charged by the charger. In order to prevent the static electricity from being removed again, control is performed to turn off the static eliminator before the static eliminator reaches the location where the static eliminator is subjected to static elimination.

According to a second aspect of the present invention, there is provided a control method for an image forming apparatus comprising: a rotating image carrier; a charger that charges the image carrier; and a downstream side of the charger in a rotation direction of the image carrier. In a control method in an image forming apparatus having a static eliminator provided to neutralize the image carrier,
A timer relating to the time required for the photosensitive drum to rotate from the charger to the position of the static eliminator after the charger is turned off based on detection of the trailing edge of the first sheet of two recording sheets to be printed continuously. Start, whether the timer has elapsed the time, or the timer when the second sheet of the leading end of the recording sheet is determined whether detected were determined and detects the leading end of the second sheet The second sheet is printed after clearing, and when it is determined that the time has passed, the charge eliminator is turned off by the charge eliminator of the image carrier. The static eliminator is turned off before the static eliminator reaches the location to be neutralized by the static eliminator in order to prevent the static eliminator from being neutralized again without being charged by the charger. To do.

  A control method for an image forming apparatus according to a third aspect of the present invention is the control method for an image forming apparatus according to the second aspect, wherein the control method is executed when the temperature is equal to or lower than a predetermined temperature.

  In the image forming apparatus according to the first aspect of the present invention and the image forming apparatus control method according to the second aspect, the charge removal portion of the image carrier by the charge eliminator is discharged again without being charged by the charger. There is nothing. Therefore, it is possible to prevent a decrease in potential during recharging and to prevent occurrence of fog. Further, since there is no problem even if the charger is turned off during non-printing, the generation of ozone can be suppressed.

  In the case of the image forming apparatus control method according to the third aspect, since the control method according to the second aspect is executed when the temperature is equal to or lower than a predetermined temperature, the occurrence of fog due to a potential drop due to carrier retention is prevented particularly in a low temperature environment. It becomes possible to do.

  The present invention will be specifically described below.

  FIG. 1 illustrates an example of an image forming apparatus according to the present invention.

  The image forming apparatus 1 includes a photosensitive drum 2 having a substantially cylindrical shape as an image carrier, and around the photosensitive drum 2, a charger 3, a developing device 4, a transfer roller 5, a polishing roller 6, a cleaning roller. The blade 7 and the static eliminator 8 are arranged along the rotation direction of the photosensitive drum 2.

  The image forming process by the image forming apparatus 1 is performed as follows. After the surface of the photosensitive drum 2 is uniformly charged by the charger 3, the surface of the photosensitive drum 2 is exposed by irradiating laser light 9 according to the image data. An electrostatic latent image is formed. Thereafter, the electrostatic latent image on the photosensitive drum 2 is developed by the developing device 4 into a toner image, and the toner image on the photosensitive drum 2 is transferred onto a transfer material, for example, the recording paper 10 by the transfer roller 5. . At this time, a current flows between the photosensitive drum 2 and the transfer roller 5 due to the movement of the charged toner, and this current is controlled to a predetermined value, that is, constant current control is performed, so that the toner on the recording paper 10 is controlled. The amount of adhesion is stabilized.

  After the transfer, the toner remaining on the photosensitive drum 2 adheres to the polishing roller 6 by polishing the photosensitive drum 2 by the polishing roller 6, and is then collected by the cleaning blade 7. Thereafter, the residual potential on the photosensitive drum 2 is erased by the static eliminator 8. Thereafter, it is charged again by the charger 3 and the above image forming process is repeated.

  On the other hand, the recording paper 10 is fed out from the cassette 11 and then conveyed along the paper conveyance line 12 and is sent between the photosensitive drum 2 and the transfer roller 5. Here, the photosensitive drum 2 is transferred by the transfer roller 5. The upper toner image is transferred and printed, and then discharged to the discharge tray 14 through the fixing unit 13. Reference numeral 15 in FIG. 1 denotes a registration sensor that detects the leading edge and the trailing edge of the recording sheet 10 conveyed along the sheet conveying line 12.

  The detection signal when the registration sensor 15 detects the leading edge and the trailing edge of the recording paper 10 is given to the control unit 20. This control unit 20 has a built-in timer function, controls the conveyance of the recording paper 10 on the paper conveyance line 12 based on the detection signal of the registration sensor 15, and rotates the photosensitive drum 2 and the charger 3 described above. On / off control, control of the developing device 4, rotation control of the transfer roller 5, rotation control of the polishing roller 6, and on / off control of the static eliminator 8 are performed.

  Here, the on / off control of the charger 3 and the on / off control of the static eliminator 8 by the control unit 20, which are the main parts of the present invention, will be described based on the timing chart of FIG. 2. In the illustrated example, an instruction is given to perform printing on two continuous recording sheets.

  As the printing starts, the control unit 20 activates the main motor (see FIG. 2A), and in synchronization with this, the static eliminator 8 is also turned on (see FIG. 2B), and then the charger 3 is turned on. The normal preparation (see FIG. 2C) is performed. In FIG. 2, a portion where the registration sensor 15 is turned on is an image forming portion for forming the toner image (see FIG. 2D).

  When the registration sensor 15 is turned on by detecting the leading edge of the recording paper 10 (see FIG. 2D), the control unit 20 conveys the recording paper 10 in synchronization with the photosensitive drum 2. Printing on the first recording sheet 10 is started. Thereafter, when the registration sensor 15 is turned off by detecting the trailing edge of the first recording sheet 10 (see FIG. 2D), the control unit 20 checks whether there is a next printing instruction. In the example of FIG. 2, since the two recording sheets 10 are continuously printed, there is a next print instruction.

  As the registration sensor 15 is turned off, the control unit 20 starts Yms from the time when the registration sensor 15 is turned off by the timer function (the trailing edge of the recording paper on the paper transport line 12 is the registration sensor as shown in FIG. 3). The charging device 3 is turned off after a lapse of time required for conveyance from 15 to the transfer roller 5 (see FIG. 2C). Subsequently, after elapse of Xms (time required for the photosensitive drum to rotate from the charger 3 to the position of the static eliminator 8 as shown in FIG. 3) by the timer function from the timing (A) when the charger 3 is turned off. Then, the static eliminator 8 is turned off (see FIG. 2B).

  Thereafter, when the registration sensor 15 is turned on by detecting the leading edge of the second recording sheet 10 (see FIG. 2D), the charger 3 is turned on (see FIG. 2C). After the elapse of Xms from the timing (B) when the charger 3 is turned on, the static eliminator 8 is turned on (see FIG. 2B). After that, when the registration sensor 15 is turned off by detecting the trailing edge of the second recording sheet 10 (see FIG. 2D), the control unit 20 does not receive the next print instruction, and therefore performs the print end operation. Do.

  FIG. 4 is a flowchart relating to the above-described print end operation, which is a main part of the present invention.

  When the registration sensor 15 is turned off, the control unit 20 starts a timer related to Yms (step S1). Then, it is determined whether or not the timer has passed Yms (step S2). When Yms has passed, the charger 3 is turned off (step S3). In the timing chart of FIG. 2, the charger 3 is turned off after Yms or more has elapsed since the registration sensor 15 was turned off (see FIG. 2C). The timing for turning off the charger 3 needs to be Yms or more in order to complete the printing on the second recording paper 10. However, if it is too long, the effect of suppressing the generation of ozone is diminished, so a short time of Yms or more is preferable.

  Subsequently, a timer for Xms is started (step S4). Thereafter, it is determined whether the timer has passed Xms or the registration sensor 15 is turned on (step S5). If it is determined that the registration sensor 15 is turned on, the process proceeds to step S6, where the timer is cleared and printing of the next page is started. On the other hand, if it is determined that the timer has passed Xms, the static eliminator 8 is turned off (step S7), and then it is determined whether continuous printing or printing has ended (step S8). Printing is started (step S9). Conversely, when printing is finished, the main motor is turned off to finish printing. In the timing chart of FIG. 2, since the printing of the two recording sheets is completed as scheduled, the static eliminator 8 and the main motor are turned off after Xms or more has passed since the charger 3 is turned off (FIG. 2A ) And (b)). It should be noted that the time for turning off the static eliminator 8 requires Xms or more from the time when the charger 3 is turned off in order to remove the portion of the photosensitive drum 2 charged by the charger 3. However, if the length is too long, the portion of the photosensitive drum 2 that has been neutralized by the static eliminator 8 is not charged by the charger 3 that has already been turned off, and is subjected to static elimination again, and fog is likely to occur. When no charging is performed by the charger 3, it is set to a timing at which the static eliminator 8 does not receive the static elimination twice.

  Therefore, in the case of this embodiment, the charge removal portion of the photoconductor drum 2 by the charge remover 8 is not charged by the charger 3 and is not discharged again. Therefore, it is possible to prevent a decrease in potential during recharging and to prevent occurrence of fog. Further, since there is no problem even if the charger 3 is turned off during non-printing, the generation of ozone can be suppressed.

  In the above-described embodiment, control is performed so that the charger 8 is turned off after the charger 3 is turned off at the end of printing regardless of the temperature of the photosensitive drum 2. The present invention is not limited to this, and the control may be executed when the temperature is lower than the temperature at which fogging is likely to occur. Thus, fogging can be prevented even if control based on temperature is performed.

  In the above-described embodiment, the image forming apparatus having one photosensitive drum is taken as an example. However, the present invention is not limited to this, and for each photosensitive drum of the image forming apparatus having two or more photosensitive drums. The same applies to the polishing roller provided.

1 is a front view illustrating an example of an image forming apparatus according to the present invention. It is a timing chart explaining the contents of control by the present invention. It is explanatory drawing regarding the time of the control content by this invention. It is a flowchart which shows the control by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum (image carrier)
3 Charger 8 Static eliminator 20 Control unit (control means)

Claims (3)

An image carrier that rotates, a charger that charges the image carrier, a static eliminator that is provided downstream of the charger in the rotation direction of the image carrier, and neutralizes the image carrier, and the charger And an image forming apparatus having control means for individually controlling on / off of the static eliminator,
The control means turns off the charger based on detection of the trailing edge of the first sheet of two recording sheets to be printed continuously, and then rotates the photosensitive drum from the charger to the position of the static eliminator. A timer for a required time is started, and it is determined whether the timer has passed the time or the leading edge of the second sheet in the recording sheet is detected, and it is determined that the leading edge of the second sheet has been detected. When the timer is cleared, the second sheet is printed, and when it is determined that the timer has passed, the static eliminator is turned off by the static eliminator of the image carrier. In order to prevent the static elimination portion that has been neutralized from being neutralized again by the static eliminator without being charged by the charger, before the static elimination portion reaches the location where the static elimination is to be eliminated, Turn off the appliance Image forming apparatus and performs control that. Image formation comprising: a rotating image carrier; a charger that charges the image carrier; and a static eliminator that is provided downstream of the charger in the rotation direction of the image carrier and neutralizes the image carrier. In the control method in the apparatus,
A timer relating to the time required for the photosensitive drum to rotate from the charger to the position of the static eliminator after the charger is turned off based on detection of the trailing edge of the first sheet of two recording sheets to be printed continuously. Start, whether the timer has elapsed the time, or the timer when the second sheet of the leading end of the recording sheet is determined whether detected were determined and detects the leading end of the second sheet The second sheet is printed after clearing, and when it is determined that the time has passed, the charge eliminator is turned off by the charge eliminator of the image carrier. The static eliminator is turned off before the static eliminator reaches the location to be neutralized by the static eliminator in order to prevent the static eliminator from being neutralized again without being charged by the charger. Image formation Control method in a location. The control method in the image forming apparatus according to claim 2,
A control method in an image forming apparatus, which is executed when the temperature is not more than a predetermined temperature.

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