JP2009162900A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of controlling cleaning frequency of a contact type electrifying device so that faulty electrification can be effectively prevented from occurring without shortening the service life of a photoreceptor. <P>SOLUTION: The image forming apparatus, where an electrification part, an exposure part, a developing unit and a transfer part are arranged around the photoreceptor, performs image formation by an electrostatic copying system, while it uses a contact type rolling member which rotates following the photoreceptor as the electrification part, and further includes a cleaning means for cleaning the peripheral surface of the rotating contact type rolling member. The image forming apparatus includes a calculation means (step S904) calculating an amount equivalent to cumulative consumption of toner in the developing unit, and a cleaning control means (step S905) performing control so that the cleaning frequency by the cleaning means can be lower stepwise as the amount equivalent to the cumulative consumption becomes larger. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a fax machine, or a multifunction machine thereof, and more particularly to a technique for cleaning a charging device that charges a photosensitive member used in the image forming apparatus.

In recent years, in an image forming apparatus, a contact type charging device that operates at a low voltage and generates a small amount of ozone has been used as a charging device for charging a photosensitive drum.
The contact type charging device uniformly charges the surface of the photosensitive drum to a predetermined potential by applying a voltage to the charging roller in a state where the charging roller is in contact with the surface of the photosensitive drum.
Now, when an electrostatic latent image formed on the surface of the photosensitive drum during image formation is visualized with a developer, some developer remains on the surface of the photosensitive member after the toner image is transferred. This developer is composed of a toner and an external additive. Since the toner has a large particle size, it is almost removed by a cleaning tool such as a cleaning blade.

On the other hand, since the external additive has a small particle size, it cannot always be completely removed and is conveyed as it is and adheres to the charging roller. If the external additive accumulates on the charging roller to form a resin film, charging failure is caused. Therefore, conventionally, for example, a sponge or the like is pressed against the charging roller to remove the external additive.
Japanese Patent Laid-Open No. 10-232535

  However, in the cleaning of the charging roller, since the charging roller is driven and rotated by the rotation of the photosensitive member, the photosensitive member is driven to rotate every time the charging roller is cleaned. It is scraped off by a member such as a cleaning blade or a developer that is in pressure contact with the surface. Therefore, if the number of times of cleaning the charging roller is increased unnecessarily, there arises a problem that the life of the photosensitive member is shortened.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an image forming apparatus capable of cleaning a contact type charging device so as to effectively prevent the occurrence of charging failure without shortening the life of the photoreceptor. Objective.

In order to solve the above-described problems, the present invention provides a charging unit, an exposure unit, a developing unit, and a transfer unit around a photoconductor, and performs image formation by an electrostatic copying method. An image forming apparatus that uses a contact-type rolling member that rotates following a photoreceptor, and further includes a cleaning unit that cleans a peripheral surface of the rotating contact-type rolling member. And a cleaning control means for controlling so that the cleaning frequency by the cleaning means decreases stepwise as the cumulative consumption equivalent amount increases.

  Here, the developing unit includes a toner storage unit that stores toner and a transport unit that transports the toner stored in the toner storage unit, and substantially between the toner storage unit and the transport unit. It can be assumed that there is no partition wall.

  By providing the above-described configuration, the flow pattern of the free external additive that flows out from the developing unit and adheres more to the contact charging member as the remaining amount of toner increases is represented by the equivalent amount of accumulated toner consumption. Since the cleaning frequency is detected and adjusted, the cleaning frequency is unnecessarily increased, and the free external additive adhering to the contact charging member can be efficiently removed without increasing the amount of abrasion due to the rotational drive of the photosensitive member. Can do.

Accordingly, an increase in the amount of abrasion of the photosensitive member can effectively prevent the occurrence of charging failure due to adhesion of a free external additive to the contact charging member without shortening the life of the photosensitive member.
Here, a plurality of types of developing units can be attached to and detached from the image forming apparatus, and the cleaning control unit performs, for each type of developing unit, an amount equivalent to the cumulative consumption amount of toner and the cleaning frequency for each type of developing unit. In the table storage means for storing the cleaning frequency management table showing the correspondence relationship, the specifying means for specifying the type of the developing unit mounted, and the cleaning frequency management table for the specified type of the developing unit, And a determination unit that determines a cleaning frequency associated with the cumulative amount of toner consumption calculated by the calculation unit as a cleaning frequency by the cleaning unit.

  Thereby, since the cleaning frequency of the contact charging member is adjusted according to the type of the developing unit, even when the outflow pattern of the free external additive corresponding to the toner equivalent consumption amount varies depending on the type of the developing unit, The contact charging member can be efficiently cleaned by determining the cleaning frequency most suitable for the flow pattern of the free external additive of the type of developing unit used in the image forming apparatus.

  According to the present invention, a charging unit, an exposure unit, a plurality of development units, and a transfer unit are arranged around the photoconductor, and image formation is performed using a plurality of development units by an electrostatic copying method. The image forming apparatus further comprising a cleaning unit that uses a contact-type rolling member that rotates following the photosensitive member as a unit, and that cleans a peripheral surface of the rotating contact-type rolling member. And calculating means for calculating the equivalent amount of accumulated toner consumption in each of the developing units, and cleaning by the cleaning means step by step as the average value of the calculated equivalent amounts of accumulated toner consumption in the plurality of developing units increases. It is good also as providing the cleaning control means which controls so that frequency may become low.

Here, the developing unit includes a toner storage unit that stores toner and a transport unit that transports the toner stored in the toner storage unit, and substantially between the toner storage unit and the transport unit. It is good also as a partition wall not existing.
As a result, even when a toner image is formed using toner supplied from a plurality of developing units, the cumulative amount of toner per developing unit is obtained by the average value of the amount corresponding to the cumulative consumption amount of toner in each developing unit. When the amount of consumption is estimated and the estimated amount of accumulated toner consumption is small, the cleaning frequency is increased, and when the estimated amount of accumulated toner consumption increases, the cleaning frequency is controlled to decrease.

Therefore, it is possible to efficiently remove the free external additive adhering to the contact charging member without unnecessarily increasing the frequency of cleaning and increasing the amount of abrasion due to the rotational drive of the photosensitive member.
As a result, it is possible to effectively prevent the occurrence of charging failure due to adhesion of the free external additive to the contact charging member without shortening the life of the photoconductor by increasing the amount of abrasion of the photoconductor.
Here, each of the plurality of developing units is equipped with a memory, and each of the memories stores an amount corresponding to the cumulative consumption amount of toner in the developing unit equipped with the memory, and the calculating means includes a toner image. For each of the plurality of developing units, a toner consumption amount calculating means for calculating a toner consumption amount equivalent amount required for forming the toner image, and each developing unit for which the toner consumption amount equivalent amount is calculated. The accumulated toner consumption equivalent amount stored in the memory installed in the developing unit is acquired, and the calculated toner consumption equivalent amount is added to the acquired toner equivalent consumption amount to obtain the latest The toner equivalent consumption amount is calculated, and the toner equivalent consumption amount stored in the memory is updated to the latest toner equivalent consumption amount. It means, for each developing unit calculated by the toner consumption amount equivalent, may have an average value calculating means for calculating an average value of the accumulated consumption amount equivalent updated toner.

As a result, the amount corresponding to the accumulated toner consumption is stored for each developing unit, and is updated to the latest amount corresponding to the latest accumulated toner consumption each time a toner image is formed.
Therefore, even if a part or all of the development unit is replaced, the amount corresponding to the cumulative amount of toner consumption of the development unit fluctuates, and the outflow pattern of the free external additive from the development unit also varies, Based on the accumulated toner consumption stored for the developing unit, the cleaning frequency can be accurately controlled so as to correspond to the flow pattern of the free external additive after the change.

The best mode for carrying out the present invention will be described below.
(Embodiment 1)
<Configuration>
FIG. 1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus 80 in the present embodiment.

As shown in FIG. 1, the image forming apparatus 80 includes a paper feeding unit 810, an image forming unit 820, an intermediate transfer unit 830, a fixing unit 840, a control unit 850, and the like, and is connected to a network (for example, a LAN). .
This image forming apparatus 80 uses a plurality of developing units and has different colors (yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K)) on one image carrier. Toner images are sequentially formed, and the formed toner images are transferred onto a transfer medium such as an intermediate transfer belt, and the transferred toner images of Y to K are collectively transferred onto a sheet. In other words, the image forming apparatus is a so-called intermediate transfer type.
(Image forming unit 820)
A photosensitive drum 91, a contact charging device 92, an exposure unit 93, a developing unit 94, a primary transfer roller 95, a cleaner 96, a waste toner transport box 97, and the like are provided. The cleaner 96 includes a cleaner blade 961. The cleaner blade 961 contacts the surface of the photosensitive drum 91, and scrapes and removes residual toner on the surface of the photosensitive drum 91 to clean the photosensitive drum 91.

(Contact type charging device 92)
FIG. 2 is a diagram illustrating a configuration of a main part of the image forming unit 820 excluding the developing unit 94. As shown in FIG. 2, the contact charging device 92 includes a charging roller 921, a cleaning member 922, and a cleaning member driving unit 923.
The charging roller 921 comes into contact with the photosensitive drum 91, receives the rotational force from the photosensitive drum 91, rotates following, and charges the surface of the photosensitive drum 91.

The cleaning member 922 is composed of a cleaning member such as a sponge and contacts the surface of the charging roller 921 to clean the surface of the charging roller 921.
The cleaning member driving unit 923 is controlled by the control unit 850 and switches contact / non-contact between the cleaning member 922 and the charging roller 921.
(Exposure unit 93)
A laser diode is built in, and the surface of the photosensitive drum 91 is exposed for each of the reproduction colors Y to K based on a drive signal from the control unit 850.

(Photosensitive drum 91)
By receiving exposure of the exposure unit 93 in a state where the surface is uniformly charged by the contact-type charging device 92, an electrostatic latent image is formed on the surface.
(Developer 94)
Consists of a rack 941 and developing units 940Y, 940M, 940C, 940K,
On the surface of the photosensitive drum 91, toner images of each color Y to K are formed.

The rack 941 is provided with four storage units (storage spaces) divided by a partition member 943, and the user stores one of the development units 940Y to 940K from the front side of the apparatus to the back side of the apparatus. It can be attached or detached by inserting it into the unit or pulling it out toward the front of the device.
In the first embodiment, the development unit is replaced when the toner is consumed, and the four development units 940Y to 940K are replaced as a set at the same time.

  FIG. 3 shows a specific example of a toner cartridge used as the developing units 940Y to 940K. 3A and 3B, reference numeral 940 represents a developing unit, reference numeral 9401 represents an agitating member for agitating the toner accommodated in the toner cartridge, and numeral 9402 represents the agitated toner. , And a supply roller that supplies toner to the developing roller denoted by reference numeral 9403.

The toner cartridge in FIG. 3A represents an integrated toner cartridge in which there is substantially no partition wall between the agitating member 9401 and the supply roller 9402, and FIG. A divided toner cartridge partitioned by a partition wall denoted by reference numeral 9404 is shown.
Here, the above-mentioned “integrated cartridge” is not limited to the one having a partitioning function such as a partition wall between the stirring member 9401 and the supply roller 9402, and a step or the like is not present between them. Some of them have a partitioning function, but some of them do not hinder the free flow of toner between them.

The rack 941 is driven to rotate in the direction of arrow B by a development switching motor (not shown) around the support shaft 942, and any of the development units corresponding to the next reproduction color is the photosensitive drum 91. The rotation is controlled by the control unit 850 so as to be positioned at the development position opposite to the control position.
The developing unit located at the developing position develops the electrostatic latent image on the surface of the photosensitive drum 91 and forms a toner image on the surface of the photosensitive drum 91.

The formed toner image is transferred onto the intermediate transfer belt 831 of the intermediate transfer unit 830 that rotates in the direction of arrow A by the electric field generated between the primary transfer roller 95 and the photosensitive drum 91 at the primary transfer position 951. The At this time, the image forming operation on the photosensitive drum 91 is performed on the intermediate transfer belt 831 in this order according to the toner color of the mounted developing unit. This is executed by controlling the timing of exposure, development unit switching operation, etc. so that the image is transferred to the same position. Thus, the color toner images are sequentially superimposed on the intermediate transfer belt 831 of the intermediate transfer unit 830 to form a color toner image.
(Intermediate transfer portion 830)
A driving roller 832, a driven roller 834, a tension roller 833, an intermediate transfer belt 831 as an intermediate transfer member stretched around these rollers, and a cleaner 836 that scrapes and removes residual toner on the intermediate transfer belt 831; A primary transfer roller 95, a secondary transfer roller 815, and the like are provided.

The primary transfer roller 95 is arranged on the intermediate transfer belt 831 that rotates the toner images of the respective colors formed in the developing unit 94 in the direction of arrow A by the electric field generated between the photosensitive drum 91 at the primary transfer position 951. Transcript to.
When the primary transfer of each color toner image onto the intermediate transfer belt 831 is completed, the secondary transfer roller 815 collectively transfers the toner image onto the sheet S and conveys it to the fixing unit 840.
(Paper Feed Unit 810)
A sheet feeding cassette 811 and a feeding roller 812 are provided. The sheet S in the sheet feeding cassette 811 is fed one by one by the feeding roller 812, and the fed sheet S is transferred to the secondary transfer position via the conveying rollers 813 and 814. Transport to 816.
(Fixing unit 840)
The toner image on the paper S, which is composed of a heating roller, a pressure roller, and the like conveyed from the intermediate transfer unit 830, is thermally fixed, and then discharged onto a discharge tray 817.
(Control unit 850)
A microcomputer, a ROM, a RAM, a hard disk unit, and the like are configured, and a computer program is stored in the RAM or the hard disk unit. As the microprocessor operates according to the computer program, the control unit 850 controls the entire image forming apparatus 80.
<Functional configuration related to cleaning frequency control processing A>
FIG. 4 is a functional block diagram illustrating a functional configuration of the image forming apparatus 80 according to the cleaning frequency control process A.

The functional configuration includes a charging roller cleaning mode determination unit 851, a charging roller cleaning mode execution unit 852, a cleaning member driving unit 923, a printed sheet count unit 853, a storage unit 854, an operation panel unit 855, a paper discharge detection unit 856, and a control unit. 850.
(Paper Ejection Detection Unit 856)
It is installed at a position indicated by reference numeral 857 in FIG. 1, detects that the sheet S after heat fixing is discharged from the fixing unit 840, and notifies the control unit 850 that it has been discharged.
(Number of printed sheets counting section 853)
Every time the discharge of the paper S is detected by the paper discharge detection unit 856, the cumulative number of printed sheets of the paper S is counted by counting up, and the control unit 850 is notified of the count value.

Further, in response to an instruction from the control unit 850, the count value of the cumulative number of printed sheets is initialized (set to 0).
Here, the “cumulative number of printed sheets” means that a set of unused development units 940Y to 940K is stored in the rack 941 and is used from the start to the present time, and the toner is heated using the set. This is the total number of sheets S discharged after fixing.
(Storage unit 854)
A cleaning process mode management table A is stored.

Here, the “cleaning process mode management table A” refers to a table indicating the correspondence relationship between the cumulative number of printed sheets, the cleaning frequency, and the cleaning process mode.
Here, “cleaning frequency” refers to the frequency of cleaning the charging roller 921 using the cleaning member 922 as a ratio of the number of cleanings to the number of discharged sheets S after heat fixing.
The “cleaning process mode” refers to an identifier for specifying the cleaning frequency.

In the cleaning processing mode management table A, the correspondence relationship between the cumulative number of printed sheets and the cleaning frequency is determined based on the outflow amount of the free external additive that flows out from the developing units of the developing units 940Y to 940K.
In the developer, external additives such as silica, titanium dioxide, and alumina are included in a state of adhering to the toner in order to improve toner characteristics such as fluidity and chargeability. As shown in FIG. 5, it is included in a free state. Reference numeral 100 in FIG. 5 represents toner particles, and reference numeral 101 represents external additive particles.

The particles of the external additive that have been released are smaller in size than the toner particles, so that they are not removed by the cleaner blade 961 but attached to the charging roller 921 as shown in FIG. The ability is reduced (reference numeral 100 in FIG. 2 represents toner particles, and reference numeral 101 represents an external additive).
In this embodiment, in order to effectively remove the free external additive adhering to the charging roller 921 without shortening the life of the photoconductor, an experiment shown in an example described later using the image forming apparatus 80 is performed. And the correspondence between the cumulative number of printed sheets and the cleaning frequency is determined based on the experimental results.

  That is, for each developing unit, the relationship between the accumulated toner consumption amount (here, the accumulated number of printed sheets is used as the equivalent amount of accumulated toner consumption) and the outflow amount of the free external additive is examined in advance by experiments, and the experimental results are obtained. In the cleaning processing mode management table A, the correspondence relationship between the cumulative number of printed sheets and the cleaning frequency is defined so that the correspondence relationship between the accumulated toner consumption amount and the outflow amount of the free external additive is reflected.

The above experimental results show that the outflow amount of the free external additive decreases as the cumulative number of printed sheets increases. Therefore, in the cleaning process mode management table A, the level of the outflow of free external additives increases as the cumulative number of printed sheets increases. Therefore, the cleaning frequency is set to be low.
By using this cleaning processing mode management table A to control the cleaning frequency, when the toner consumption in the developing unit is small and the developing unit is in a state where a large amount of free external additive flows out, the cleaning frequency When the toner consumption in the developing unit is large and the developing unit is not in a state where a large amount of free external additive flows out, the cleaning frequency can be adjusted to be low.

Accordingly, it is possible to effectively remove the free external additive attached to the charging roller 921 without performing unnecessary cleaning processing and excessively increasing the amount of abrasion of the photosensitive drum 91.
As a result, it is possible to effectively prevent the occurrence of charging failure without shortening the life of the photosensitive drum 91.
FIG. 6 shows a specific example of the cleaning process mode management table A.

Here, a cleaning process mode management table A applied when the integrated toner cartridge shown in FIG. 3A is used as the four developing units 940Y to 940K in the image forming apparatus 80 is shown.
(Charging roller cleaning mode determination unit 851)
A cleaning process mode specifying process and a cleaning process mode notification process are performed.
1. Cleaning process mode management table A acquisition process Each time the cumulative number of printed sheets counted by the printed sheet count unit 853 is notified from the control unit 850, the cleaning process mode management table A stored in the storage unit 854 is transferred to the control unit. Via 850.
2. Cleaning process mode notification process Referring to the cleaning process mode management table A, the cleaning process mode associated with the notified cumulative print number is specified, and if there is no cleaning process mode specified immediately before or specified immediately before If the cleaning process mode that has been newly identified differs from the cleaning process mode that has been specified most recently, the cleaning process mode that has been specified most recently is determined as the cleaning process mode of the charging roller 921, and the charging roller cleaning mode execution unit is configured via the control unit 850. 852 is notified.
(Charging roller cleaning mode execution unit 852)
When the determined cleaning processing mode is notified from the charging roller cleaning mode determination unit 851, the cleaning processing mode management table A stored in the storage unit 854 is acquired via the control unit 850, and the notified cleaning is performed. Each time the number of discharged sheets S after heat fixing after the cleaning frequency associated with the processing mode is notified and the cleaning processing mode is notified reaches the number of discharged sheets indicated by the specified cleaning frequency, the control unit A cleaning execution instruction is notified to the cleaning member driving unit 923 via 850.
(Operation panel section 855)
A display unit (for example, a liquid crystal display) on which a touch panel is stacked and a plurality of input keys are provided, and an instruction from a user is received and notified to the control unit 850 by touch input from the touch panel or key input from the input key. .
<Operation>
(Cleaning frequency control process A)
Next, the operation of the cleaning frequency control process A performed by the image forming apparatus 80 will be described. FIG. 7 is a flowchart showing the operation of the above processing. The above operation will be described below with reference to FIG.

When a set of four unused development units 940Y to 940K is newly stored in the rack 941, the control unit 850 instructs the print number counting unit 853 to set the count value (T) of the accumulated print number to 0. (Step S901).
Next, when the control unit 850 receives an input of a print instruction from the operation panel unit 855 (step S902), the control unit 850 executes a print process to thermally fix the toner image on the paper S.

Each time the paper S after the printing process is discharged to the paper discharge tray 817 (step S903), the printed sheet count unit 853 counts up the cumulative number of printed sheets (step S904).
When the controller 850 notifies the charging roller cleaning mode determination unit 851 of the counted cumulative number of printed sheets, the charging roller cleaning mode determination unit 851 cleans the cleaning process mode management table A stored in the storage unit 854. Is acquired via the control unit 850, the cleaning process mode associated with the notified cumulative print number is specified with reference to the cleaning process mode management table A (step S905), and the specified cleaning process mode is specified. Is determined to match the cleaning process mode specified immediately before (step S906).

If there is no cleaning process mode specified immediately before, the charging roller cleaning mode determination unit 851 proceeds to the process of step S907.
If the determination result of step S906 is negative (step S906: N), the charging roller cleaning mode determination unit 851 determines the cleaning processing mode specified most recently as the cleaning processing mode of the charging roller 921, and performs control. The charging roller cleaning mode execution unit 852 is notified via the unit 850 (step S907).

Upon receiving the notification of the cleaning process mode, the charging roller cleaning mode execution unit 852 causes the cleaning member driving unit 923 to execute the cleaning process of the charging roller 921 according to the notified cleaning process mode (step S908).
Next, the control unit 850 determines whether or not the power has been turned off (step S909). If the determination result is negative (step S909: N), the process proceeds to step S902, and the determination result is If the determination is affirmative (step S909: Y), the cleaning frequency control process A ends.

When the determination result of step S906 is affirmative (step S906: Y), the control unit 850 proceeds to the process of step S909.
(Example)
1. Relationship Between Cumulative Number of Printed Sheets and Outflow Amount of Free External Additive When the integrated toner cartridge shown in FIG. 3A is used in the image forming apparatus 80 as a developing unit, and the divided type shown in FIG. FIG. 8 shows the result of an experiment for examining the relationship between the cumulative number of printed sheets and the flow rate of the free external additive when the toner cartridge is used in the image forming apparatus 80 as a developing unit.

In the above experiment, a collecting roller for collecting the external additive is provided in the image forming apparatus 80 in place of the charging roller 921, and the printing process is executed. The amount of free external additive recovered by the recovery roller (the flow rate of free external additive) was measured by measuring the lightness (ΔL) with a color difference meter.
As shown by reference numeral 801 in FIG. 8, when the integrated cartridge is used as the developing unit, the outflow amount of the free external additive shows the maximum value when the cumulative number of printed sheets at the start of use is the minimum, and thereafter The tendency to decrease as the cumulative number of printed sheets increases.

On the other hand, as shown by reference numeral 802 in FIG. 8, when the split cartridge is used as the developing unit, the outflow amount of the free external additive shows the maximum value when the cumulative number of printed sheets at the start of use is the minimum. After that, the value was almost constant.
As shown above, the flow pattern of the free external additive varies depending on the type of the developing unit, but in any case, a large amount of free external additive flows out immediately after the start of use, where the cumulative number of printed sheets is small. Showed a trend.
2. Relationship between Adhesive Amount of Free External Additive to Charging Roller and Cumulative Number of Prints When the integrated toner cartridge shown in FIG. 3A is used in the image forming apparatus 80 as a developing unit, FIG. 3B FIG. 9 shows the results of an experiment for examining the relationship between the cumulative number of printed sheets and the amount of free external additive attached to the charging roller when the divided toner cartridge shown in FIG.

In the above experiment, each time the print processing is executed using the image forming apparatus 80 and the predetermined cumulative number of printed sheets is reached, the amount of the free external additive adhering to the charging roller 921 up to that point is measured with a color difference meter. It was measured by measuring the lightness (ΔL) of the surface of the charging roller 921.
As shown by reference numeral 901 in FIG. 9, when the integrated cartridge is used as a developing unit, the amount of free external additive attached increases as the cumulative number of printed sheets increases. The amount of increase until the cumulative number of printed sheets reached 6000 showed a tendency to be larger than after that.

Further, as shown by reference numeral 902 in FIG. 9, even when the split cartridge is used as the developing unit, the increase amount is smaller than that in the case of the integral cartridge, but shows the same tendency as in the case of the integral cartridge. It was.
3. Relationship between the amount of photoconductor drum scraping and the total number of prints The photoconductor drum 91 when the charging roller 921 is cleaned under the three cleaning conditions shown in FIG. FIG. 11 shows the result of an experiment for examining the relationship between the amount of shaving and the total number of printed sheets.

Among the three cleaning conditions shown in FIG. 10, Conventional Example 1 shows a cleaning condition in which the cleaning frequency is increased as the cumulative number of printed sheets in the developing unit increases, and Conventional Example 2 is in a state where the cleaning frequency is high from the beginning. The cleaning conditions for continuous cleaning are shown, and the examples show the cleaning conditions used in the first embodiment.
Reference numeral 111 in FIG. 11 indicates the relationship between the amount of abrasion of the photosensitive drum 91 and the total number of printed sheets when the cleaning conditions of the embodiment are used, and reference numeral 112 indicates the sensitivity when the cleaning conditions of the first conventional example are used. 11 shows the relationship between the amount of abrasion of the body drum 91 and the total number of printed sheets, and reference numeral 113 in FIG. 11 shows the relationship between the amount of abrasion of the photosensitive drum 91 and the total number of printed sheets when the cleaning conditions of Conventional Example 2 are used. .

Further, reference numeral 114 in FIG. 11 indicates the amount of abrasion (15 μm) when the photosensitive drum 91 reaches the end of its life.
As shown in the experimental results of FIG. 11, when the printing process is executed under the cleaning conditions of the embodiment, the amount of abrasion of the photosensitive drum 91 is the smallest, and the printing process is executed under the cleaning conditions of the conventional example 2. The shaving amount of the photosensitive drum 91 was the largest.
4). Conclusion When the cumulative number of printed sheets in the developing unit is small, cleaning of the charging roller 921 is increased by increasing the cleaning frequency of the charging roller 921 and gradually decreasing the cleaning frequency as the cumulative number of printed sheets increases. It can be carried out efficiently according to the change in the flow rate of the additive.

That is, while the amount of free external additive flowing out is small, the amount of free external additive flowing out is effectively prevented from increasing the frequency of cleaning unnecessarily and shortening the life of the photosensitive drum 91. In many cases, the frequency of cleaning can be increased and the free external additive adhering to the charging roller 921 can be efficiently removed.
(Embodiment 2)
In the first embodiment, when four development units are simultaneously replaced as a set, the cleaning control of the contact-type charging device 92 is switched according to the cumulative number of printed sheets printed using the set. However, in the image forming apparatus according to the second embodiment, the cumulative consumption amount of toner is managed for each individual development unit, and the contact-type charging device according to the average value of the cumulative toner consumption amount in the four development units. 92, the cleaning frequency switching control is performed.

Hereinafter, components and operations different from those of the image forming apparatus 80 according to the first embodiment will be mainly described, and description of parts common to the image forming apparatus 80 according to the first embodiment will be omitted.
<Functional configuration related to cleaning frequency control processing B>
FIG. 12 is a functional block diagram illustrating a functional configuration of the image forming apparatus 90 according to the cleaning frequency control process B.

The functional configuration includes a charging roller cleaning mode determination unit 861, a charging roller cleaning mode execution unit 852, a cleaning member driving unit 923, a storage unit 864, an operation panel unit 855, an IC tag reading unit 857, a toner consumption amount calculation unit 858, an image. The storage unit 859 includes development unit IC tags 9401Y, 9401M, 9401C, and 9401K, and a control unit 850.
(Storage unit 864)
A cleaning process mode management table B is stored.

Here, the “cleaning process mode management table B” refers to a table showing a correspondence relationship between the cumulative toner consumption, the cleaning frequency, and the cleaning process mode.
The cleaning process mode management table B uses the “average value of accumulated toner consumption in each developing unit” instead of the “cumulative number of printed sheets” in the cleaning process mode management table A, and shows the correspondence with “cleaning frequency”. Refers to the table.

Here, the “toner cumulative consumption amount” is the total consumption amount of toner consumed for the developing unit from the time when each unused developing unit is stored in the rack 941 to start use. This is calculated by a cumulative toner consumption calculation unit 859 described later.
In the cleaning process mode management table B, the correspondence between the average value of the cumulative toner consumption and the cleaning frequency is the free flow out of each of the developing units 940Y to 940K as in the cleaning process mode management table A. It is determined based on the experimental results on the outflow amount of external additives.

Specifically, the cleaning frequency is set to decrease stepwise as the average value of the cumulative toner consumption increases.
(Image storage unit 859)
Temporarily store image data acquired via a scanner (not shown) or a network.
(Toner consumption calculation unit 858)
Based on the dot count of each color of the image data stored in the image storage unit 859, the toner consumption amount in each developing unit is calculated and output to the control unit 850.

Since the toner consumption calculation method is a known technique (for example, described in JP-A-2001-232903, JP-A-2001-166547, JP-A-2001-154472, etc.), a detailed method is described. Description is omitted.
(Toner cumulative consumption calculation unit 859)
The accumulated toner consumption amount stored in the development unit IC tag corresponding to each developing unit for which the toner consumption amount is calculated is acquired via the IC tag reading unit 857 and the control unit 850, and the acquired accumulated toner consumption is obtained. The amount of toner consumption calculated for the developing unit is added to the amount, the value of the cumulative toner consumption is updated, and the updated cumulative toner consumption is updated via the IC tag reading unit 857 and the control unit 850. The development unit IC tag is overwritten.

Further, an average value of the cumulative toner consumption calculated for each color (hereinafter referred to as “average cumulative consumption”) is calculated and notified to the charging roller cleaning mode determination unit 861 via the control unit 850.
(Developing unit IC tags 9401Y, 9401M, 9401C, 9401K)
The accumulated toner consumption amount of the installed development unit is stored in each developing unit, and the stored toner consumption amount is updated by the accumulated toner consumption calculation unit 859 every time the toner is used. Is done.

When the developing unit is not in use (at the time of shipment), the initial value (0) is stored as the accumulated toner consumption amount in the developing unit IC tag mounted on the developing unit.
Here, the development unit IC tag includes an antenna coil, a resonance capacitor that constitutes a resonance circuit with the antenna coil, a switch, a decoding unit, an encoding unit, a communication control unit, a power supply unit, and a memory.

When the developing unit IC tag receives a power supply signal for power transmitted from an IC tag reading unit 857, which will be described later, a current flows through the antenna coil, electric charge is accumulated in the power supply unit, and electric power based on the accumulated electric charge. The information stored in the memory is read out, the switch is turned on / off, and a radio wave signal including the read out information is transmitted to the IC tag reading unit 857 via the antenna coil.
(Charging roller cleaning mode determination unit 861)
A cleaning process mode management table B acquisition process and a cleaning process mode notification process are performed.
1. Cleaning Process Mode Management Table B Acquisition Process Each time the average cumulative consumption is notified from the toner cumulative consumption calculation unit 858, the cleaning process mode management table B stored in the storage unit 864 is sent via the control unit 850. get.
2. Cleaning process mode notification process Refers to the cleaning process mode management table B, specifies the cleaning process mode associated with the notified average cumulative consumption, and if there is no cleaning process mode specified immediately before or immediately before When the specified cleaning processing mode is different from the latest specified cleaning processing mode, the latest specified cleaning processing mode is determined as the cleaning processing mode of the charging roller 921 and the charging roller cleaning mode is executed via the control unit 850. Section 852 is notified.
(IC tag reading section 857)
Communication is performed with the development unit IC tags 9401Y, 9401M, 9401C, and 9401K, and the accumulated toner consumption amount stored in each development unit IC tag is read.

In addition, the cumulative toner consumption amount stored in each IC tag is rewritten to the cumulative toner consumption amount newly calculated by the cumulative toner consumption amount calculation unit 859.
The IC tag reading unit 857 includes a transmission unit having a transmission antenna coil and a reception unit having a reception antenna coil, and communicates with each development unit IC tag via the transmission unit and the reception unit. The data stored in the IC tag for reading is read and the data stored in the IC tag for each developing unit is rewritten.
<Operation>
Next, the operation of the cleaning frequency control process B performed by the image forming apparatus 90 will be described. FIG. 13 is a flowchart showing the operation of the above processing. The above operation will be described below with reference to FIG.

When receiving a print instruction input from operation panel unit 855 (step S1101), control unit 850 temporarily stores image data acquired via a scanner (not shown) or a network in image storage unit 859.
Next, the toner consumption amount calculation unit 858 calculates the toner consumption amount (UY, UM, UC, UK) in each of the developing units 940Y to 940K based on the number of pixels of each pixel of the stored image data. Calculate (step S1102).

Next, the control unit 850 executes printing processing, thermally fixes the toner image on the paper S, and discharges the paper S after the printing processing to the paper discharge tray 817 (step S1103).
Thereafter, the cumulative toner consumption calculation unit 859 calculates the cumulative toner consumption (TUY, TUM, TUC, TUK) stored in the development unit IC tag corresponding to each developing unit for which the toner consumption is calculated. Acquired via the IC tag reading unit 857 and the control unit 850 (step S1104), the acquired toner cumulative consumption amount is added to the toner consumption amount calculated for the developing unit (step S1105), and the toner cumulative consumption amount is obtained. The updated toner accumulated consumption is overwritten on the development unit IC tag via the IC tag reading unit 857 and the control unit 850 (step S1106), and further calculated for each development unit. The average value of the accumulated toner consumption (hereinafter referred to as “average accumulated consumption”) is calculated (step S1107), and the controller Through 50 notifies the charging roller cleaning mode determining unit 861.

  When the average cumulative consumption amount is notified from the control unit 850 to the charging roller cleaning mode determination unit 861, the charging roller cleaning mode determination unit 861 controls the cleaning process mode management table B stored in the storage unit 864. The cleaning process mode acquired through the unit 850 and referring to the cleaning process mode management table B is specified for the notified average accumulated consumption (step S1108), and the specified cleaning process mode is immediately before. In step S1109, it is determined whether or not the cleaning process mode matches the above-described cleaning process mode.

When there is no cleaning process mode specified immediately before, the charging roller cleaning mode determination unit 861 proceeds to the process of step S1112 described later.
If the determination result in step S1108 is negative (step S1109: N), the charging roller cleaning mode determination unit 861 determines the most recently specified cleaning processing mode as the cleaning processing mode for the charging roller 921, and performs control. The charging roller cleaning mode execution unit 852 is notified via the unit 850 (step S1110).

Upon receiving the notification of the cleaning process mode, the charging roller cleaning mode execution unit 852 causes the cleaning member driving unit 923 to execute the cleaning process of the charging roller 921 in accordance with the notified cleaning process mode (step S1111).
Next, the control unit 850 determines whether or not the power is turned off (step S1112). If the determination result is negative (step S1111: N), the process proceeds to step S1101, and the determination result is If the result is affirmative (step S1111: Y), the cleaning frequency control process B is terminated.

If the determination result of step S1108 is affirmative (step S1108: Y), the control unit 850 proceeds to the process of step S1112.
<Supplement>
As described above, the image forming apparatuses 80 and 90 according to the present invention have been described based on the embodiment. However, the present invention is not limited to this embodiment.
In the first and second embodiments, the four-cycle image forming apparatus has been described. However, the cleaning frequency control processes A and B in the first and second embodiments are similarly applied to a tandem type image forming apparatus. Can do.
In the first embodiment, only one type of cleaning processing mode management table A is stored in the storage unit 854. However, a plurality of types of cleaning processing mode management tables A are provided for each type of developing unit used in the image forming apparatus 80. As shown in FIGS. 14A and 14B, a plurality of cleaning processing mode management tables A are stored in the storage unit 854 in association with identifiers indicating the types of development units. A memory for storing an identifier indicating the type of the developing unit (for example, a developing unit IC tag used in the second embodiment) may be mounted.

  In this case, in step S905 of the operation of the cleaning frequency control process A, the control unit 850 reads information stored in the memory mounted on the developing unit (the image forming apparatus 80 reads the IC tag according to the second embodiment). 857, and the information is read through the IC tag reading unit 857.) Based on the information, the cleaning process mode management table A to be referred to is specified, and the specified cleaning process mode management table A is determined. By acquiring the data from the storage unit 854 and outputting it to the charging roller cleaning mode determination unit 851, the charging roller cleaning mode determination unit 851 is in accordance with the type of the developing unit stored in the rack 941 of the image forming apparatus 80. The cleaning process mode management table A can be referred to.

As a result, in an image forming apparatus that can use a plurality of types of developing units, the cleaning frequency control pattern can be switched according to the difference in the flow pattern of free external additives between the types of developing units. Frequency control can be optimized according to the type of development unit.
Also in the second embodiment, as described above, the cleaning processing mode management table B is stored in the storage unit 864 in association with the type of the development unit, and development is performed in the development unit IC tags 9401Y, 9401M, 9401C, and 9401K. An identifier indicating the unit type may be stored.

  Also in this case, in step S1107 of the operation of the cleaning frequency control process B, the control unit 850 reads the identifier indicating the type stored in the development unit IC tag via the IC tag reading unit 857, and based on the identifier. Then, the cleaning process mode management table B to be referred to is specified, the specified cleaning process mode management table B is acquired from the storage unit 864, and is output to the charging roller cleaning mode determination unit 861. 861 can be referred to the cleaning processing mode management table B corresponding to the type of the developing unit stored in the rack 941 of the image forming apparatus 90.

Thereby, the effect similar to the above is acquired.
(3) In the first and second embodiments, the image forming apparatus in which the developing unit can be replaced has been described. In the cleaning frequency control processes A and B, the developing unit, the photosensitive drum, and the charging roller are integrated. The same can be applied to an image forming apparatus using a so-called process cartridge.
(4) In the first embodiment, in the cleaning frequency control process A, the cleaning frequency is controlled according to the cumulative number of printed sheets. However, instead of the cumulative number of printed sheets, as described in the second embodiment, The accumulated toner consumption amount for the developing unit may be calculated, and the cleaning frequency may be controlled according to the total amount of accumulated toner consumption amount calculated for each developing unit, or the accumulated toner consumption amount calculated for each developing unit may be controlled. The cleaning frequency may be controlled according to the average value.
(5) In the second embodiment, in the cleaning frequency control process B, the cleaning frequency is controlled according to the average cumulative consumption. However, instead of the average cumulative consumption, the cumulative toner consumption for each developing unit is used. The cleaning frequency may be controlled in accordance with the total amount of accumulated toner consumption calculated for each developing unit.
(6) In the first and second embodiments, the charging roller 921 is cleaned using the cleaning member. However, the cleaning of the charging roller 921 is not limited to the case where the cleaning member is used. For example, as disclosed in a publicly known document (Japanese Patent Laid-Open No. 2004-219872), the charging roller 921 is cleaned by applying a reverse polarity bias to the charging roller 921 during normal image formation. The method may be used

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a fax machine, or a combination of these, and can be used particularly as a technique for cleaning a charging device that charges a photosensitive member used in the image forming apparatus.

2 is a schematic cross-sectional view illustrating the overall configuration of the image forming apparatus 80. FIG. FIG. 10 is a diagram illustrating a configuration of a main part of an image forming unit 820 excluding a developing unit 94. Specific examples of toner cartridges used as the developing units 940Y to 940K are shown. 4 is a functional block diagram showing a functional configuration of an image forming apparatus 80 according to cleaning frequency control processing A. FIG. It is a schematic diagram which shows the structure of a developing agent. The specific example of the cleaning process mode management table A is shown. 7 is a flowchart illustrating an operation of a cleaning frequency control process A performed by the image forming apparatus 80. When the integrated toner cartridge shown in FIG. 3A is used as the developing unit in the image forming apparatus 80, and the divided toner cartridge shown in FIG. 3B is used as the developing unit in the image forming apparatus 80. 6 is a graph showing the results of an experiment for examining the relationship between the cumulative number of printed sheets and the flow rate of free external additive. When the integrated toner cartridge shown in FIG. 3A is used as the developing unit in the image forming apparatus 80, and the divided toner cartridge shown in FIG. 3B is used as the developing unit in the image forming apparatus 80. 6 is a graph showing the results of an experiment for examining the relationship between the cumulative number of printed sheets and the amount of free external additive attached to the charging roller. 7 is a table showing cleaning conditions for the charging roller 921 in the embodiment, the conventional example 1, and the conventional example 2. An experiment for examining the relationship between the amount of abrasion of the photosensitive drum 91 and the total number of prints when the charging roller 921 is cleaned under the three cleaning conditions shown in FIG. It is a graph which shows the result of. 3 is a functional block diagram illustrating a functional configuration of an image forming apparatus 90 according to a cleaning frequency control process B. FIG. 6 is a flowchart illustrating an operation of a cleaning frequency control process B performed by the image forming apparatus 90. The modification of the cleaning process mode management table A is shown.

Explanation of symbols

80, 90 Image forming apparatus 91 Photosensitive drum 92 Contact-type charging device 93 Exposure section 94 Development section 95 Primary transfer roller 96, 836 Cleaner 97 Waste toner transport box 810 Paper feed section 811 Paper feed cassette 812 Feed roller 813, 814 Transport roller 815 Secondary transfer roller 816 Secondary transfer position 817 Ejection tray 820 Image forming unit 830 Intermediate transfer unit 831 Intermediate transfer belt 832 Drive roller 833 Tension roller 834 Driven roller 840 Fixing unit 850 Control unit 851, 861 Charging roller cleaning mode determination unit 852 Charging roller cleaning mode execution unit 853 Printed sheet count unit
854, 864 Storage unit 855 Operation panel unit 856 Paper discharge detection unit 857 IC tag reading unit 858 Toner consumption calculation unit 859 Image storage unit 921 Charging roller 922 Cleaning member 923 Cleaning member driving unit 940Y, 940M, 940C, 940K Development unit 941 Rack 942 Support shaft 943 Partition member 951 Primary transfer position 961 Cleaner blade 9401Y, 9401M, 9401C, 9401K Development unit IC tag

Claims (6)

A charging unit, an exposure unit, a developing unit, and a transfer unit are arranged around the photosensitive member, and image formation is performed by an electrostatic copying method. An image forming apparatus, further comprising a cleaning unit that cleans the peripheral surface of the rotating contact-type rolling member using a member,
Calculating means for calculating an equivalent amount of cumulative toner consumption in the developing unit;
An image forming apparatus comprising: a cleaning control unit that performs control so that the cleaning frequency of the cleaning unit decreases stepwise as the cumulative consumption equivalent amount increases. The developing unit includes a toner storage unit that stores toner and a transport unit that transports toner stored in the toner storage unit;
The image forming apparatus according to claim 1, wherein there is substantially no partition wall between the toner storage unit and the transport unit. A plurality of types of developing units can be attached to and detached from the image forming apparatus,
The cleaning control means includes
Table storage means for storing a cleaning frequency management table indicating a correspondence relationship between the cumulative consumption amount of toner in the type of developing unit and the cleaning frequency for each type of the developing unit;
A specifying means for specifying the type of the developing unit installed;
In the cleaning frequency management table for the specified type of the developing unit, a determination unit that determines a cleaning frequency associated with a cumulative amount of toner consumption calculated by the calculation unit as a cleaning frequency by the cleaning unit. The image forming apparatus according to claim 1, further comprising: A charging unit, an exposure unit, a plurality of development units, and a transfer unit are arranged around the photoconductor, and image formation is performed using a plurality of development units by an electrostatic copying method. An image forming apparatus comprising: a contact-type rolling member that is driven and rotated; and further comprising a cleaning unit that cleans a peripheral surface of the rotating contact-type rolling member.
Calculating means for calculating an equivalent amount of accumulated toner consumption in each of the plurality of developing units;
And a cleaning control unit that performs control so that the frequency of cleaning by the cleaning unit decreases stepwise as the calculated average value of the equivalent amount of accumulated toner consumption in the plurality of developing units increases. Image forming apparatus. The developing unit includes a toner storage unit that stores toner and a transport unit that transports toner stored in the toner storage unit;
The image forming apparatus according to claim 4, wherein there is substantially no partition wall between the toner containing portion and the conveying portion. Each of the plurality of development units is equipped with a memory,
Each of the memories stores an amount corresponding to the cumulative consumption amount of toner in the developing unit equipped with the memory,
The calculating means includes
A toner consumption amount calculating means for calculating, for each of the plurality of development units, a toner consumption amount equivalent amount required for forming the toner image each time a toner image is formed;
For each development unit for which the toner consumption equivalent amount has been calculated, the toner equivalent consumption amount stored in the memory installed in the development unit is acquired and calculated as the acquired toner equivalent consumption amount. The calculated toner consumption equivalent amount is added to calculate the latest toner cumulative consumption equivalent amount, and the toner cumulative consumption equivalent amount stored in the memory is updated to the latest toner equivalent consumption amount. Updating means to
6. The image forming apparatus according to claim 4, further comprising: an average value calculating unit that calculates an average value of the updated cumulative toner consumption amount for each developing unit for which the toner consumption amount equivalent amount is calculated. .

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