JP4194275B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus provided with functional members such as an image carrier, a developing unit, and an image carrier cleaning unit as a cartridge that can be attached to and detached from the apparatus main body.
[0002]
[Prior art]
In recent years, with the widespread use of electrophotographic color image forming apparatuses, there is an increasing demand for speeding up color output in addition to the demand for recording quality of color images. In order to meet this demand, several proposals have been made for image forming methods.
[0003]
For example, in a tandem type color image forming apparatus in which a plurality of photosensitive drums are arranged side by side, toner images of each color of black, cyan, magenta, and yellow are formed on each photosensitive drum, and are carried and conveyed by a transfer material conveyance belt. After sequentially transferring the transfer material by each transfer means, the toner image is fixed by a fixing device.
[0004]
In the tandem type color image forming apparatus, as shown in FIGS. 7A and 7B, the transfer material S set in a feeding cassette 111 mounted on the lower part of the apparatus main body is fed by a sheet feeding roller 112. Then, it is sent to the registration roller pair 114.
[0005]
On the downstream side of the registration roller pair 114 in the transfer material conveyance direction, the transfer material conveyance belt 102 for conveying the transfer material S is transferred in the transfer material conveyance direction (FIG. 7) by a plurality of rotating rollers such as a driving roller 118, a driven roller 119, and a tension roller 121. The suction roller 122 is disposed in the most upstream portion in the transfer material conveyance direction, and is pressed against the driven roller 119 via the transfer material conveyance belt 102.
[0006]
A predetermined bias voltage is applied to the suction roller 122, so that the transfer material S transported onto the transfer material transport belt 102 at a timing by the registration roller pair 114 is electrostatically applied to the transfer material transport belt 102. Adsorbed and carried.
[0007]
The four photosensitive drums 101y, 101m, 101c, and 101k (hereinafter simply referred to as “photosensitive drum 101”) of yellow, magenta, cyan, and black in order from the lower side to the upper side of FIG. ) Are arranged in a straight line.
[0008]
Further, there are primary chargers 103y, 103m, 103c, and 103k (hereinafter, simply referred to as “primary charger 103”) and developing units 109, 109m, 109c, and 109k (hereinafter, simply “ Development unit 109 ”and cleaning units 106y, 106m, 106c, and 106k (hereinafter simply referred to as“ cleaning unit 106 ”) are arranged, and transfer members 108y, 108m, 108c, and 108k are sandwiched between transfer material conveyance belts 102. (Hereinafter simply referred to as “transfer member 108”) is disposed.
[0009]
Each color toner is accommodated in the toner container of the developing device 109, and the toner image of each color is sequentially transferred to the transfer material S carried and conveyed by the transfer material conveyance belt 102 by a known image forming process, and the color image. Is formed.
[0010]
The transfer material S to which the toner image has been transferred is separated in curvature at a position facing the driving roller 118 and guided to the fixing roller pair 115, and is heated and pressurized while being nipped and conveyed by the fixing roller pair 115, and the toner. After the image is permanently fixed, the image is conveyed by a pair of discharge rollers 116 and discharged onto a discharge tray 117 disposed at the top of the apparatus main body.
[0011]
The color image forming apparatus as described above does not always perform multi-color printing, that is, full-color image formation, and the frequency of black-color recording, that is, monochrome image formation is considerably high. In order to cope with such usage, there has been proposed a tandem type color image forming apparatus configured to be able to switch between full color image formation and monochrome image formation.
[0012]
For example, as shown in FIG. 7A, the image carrier and the developing roller are in contact with each other during full-color image formation, and as shown in FIG. 7B during mono-color image formation. Then, the separating means 123 pushes up a part 124 of the bottom surface of the developing device and pushes it upward in FIG. 7B to separate the developing roller 110 from the photosensitive drum 101 of a color other than black, thereby recording only the black image. .
[0013]
With this configuration, the path through which the transfer material S is transported from the suction roller 122 through the black image forming unit to the fixing roller pair 115 does not change between full-color image formation and monochrome image formation, and stable transport performance is achieved. can get.
[0014]
[Problems to be solved by the invention]
However, in the above-described conventional example, when a large number of monocolor images are formed, toner as a lubricant is reduced in the rubbing portion between the image carrier and the cleaning blade in a process cartridge other than black. The contact state is likely to become unstable, and there is a risk of causing a cleaning failure such as toner slipping and an image failure due to contamination of the charging member, and in the worst case, a cleaning blade may be turned over.
[0015]
The present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to provide a monochromatic image in an image forming apparatus having a function of forming both a full color image and a monocolor image. An object of the present invention is to provide an image forming apparatus capable of stably obtaining a high-quality image even when a large amount of formation processing is performed continuously.
[0016]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention provides an image bearing member that is rotatable by carrying an electrostatic latent image on the surface, and a developing roller is brought into contact with the image bearing member to form an electrostatic latent image on the surface of the image bearing member. A plurality of process cartridges that can be attached to and detached from the main body of the image forming apparatus, including developing means for developing the developer by supplying developer and cleaning means for cleaning the surface of the image carrier in contact with the image carrier; A transfer material conveying means for conveying the transfer material, wherein the plurality of process cartridges are arranged along a conveyance path of the transfer material conveying means, and are arranged on one image carrier in the plurality of process cartridges. switchable and monochromatic mode for forming an image contrast, and a full-color mode for forming an image on a plurality of image bearing members of the plurality of process cartridges, in the monochromatic mode, the image Formed by separating the image bearing member of the process cartridge and the developing roller is not performed, the image forming apparatus having a structure for rotating the image bearing member of the plurality of process cartridges regardless not performed an image is formed on the mono-color mode In the mono color mode , an image carrier of a process cartridge that does not perform image formation at a predetermined timing and a developing roller are brought into contact with each other, and the developer is supplied from the developing unit to the cleaning unit of the process cartridge. The amount of the developer supplied to the cleaning unit of the process cartridge that performs the supply operation and does not perform image formation in the mono color mode decreases as the ratio of the mono color mode to the full color mode decreases. To do.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.
[0023]
(First embodiment)
First, a first embodiment embodying an image forming apparatus of the present invention will be described with reference to FIGS.
[0024]
1 and 2 are cross-sectional views showing the configuration of the image forming apparatus according to the present embodiment. FIG. 1 shows how full-color image formation is performed, and FIG. 2 shows how monochrome image formation is performed.
[0025]
1 and 2, the color image forming apparatus A includes four electrophotographic photosensitive drums 1y, 1m, 1c, and 1k (image bearing members linearly arranged in the vertical direction in FIGS. 1 and 2). Hereinafter, the transfer material conveyance belt 2 is provided as a transfer material carrier that adsorbs and conveys the transfer material S by electrostatic adsorption so as to face each of the photoconductor drums 1. Is arranged.
[0026]
Each of the photosensitive drums 1 includes two magenta and cyan photosensitive drums 1m and 1c at the upper and lower ends of the yellow and black photosensitive drums 1y and 1k in FIG. It is arranged so as to protrude to the side, and is driven to rotate counterclockwise in FIG. 1 by a driving means (not shown).
[0027]
Around each photosensitive drum 1, primary chargers 3y, 3m, 3c, and 3k (hereinafter simply referred to as "charging means" for uniformly charging the surface of the photosensitive drum 1 in order from the upstream side in the rotation direction). Exposure unit 4y, 4m, which forms an electrostatic latent image by irradiating the surface of the photosensitive drum 1 uniformly charged by the primary charger 3 with a laser beam based on image information. 4c and 4k (hereinafter simply referred to as “exposure means 4”) are arranged.
[0028]
Further, developing means 5y, 5m, 5c, and 5k (hereinafter simply referred to as "developing means 5") that make each color toner adhere to the surface of the photosensitive drum 1 on which the electrostatic latent image has been formed to visualize the toner image. Cleaning means 6y, 6m, 6c, 6k (hereinafter simply referred to as “cleaning means 6”) for removing toner remaining on the surface of the photosensitive drum 1 after transfer are disposed.
[0029]
The photosensitive drum 1, the primary charger 3, the developing means 5 and the cleaning means 6 are integrated into a cartridge as process cartridges By, Bm, Bc, Bk (hereinafter simply referred to as “process cartridge 7”). It is comprised so that attachment or detachment is possible.
[0030]
Further, a toner image formed on the surface of the photosensitive drum 1 is transferred to a transfer material S carried and conveyed by the transfer material conveyance belt 2 with the transfer material conveyance belt 2 interposed therebetween at a position facing each photosensitive drum 1. Transfer rollers 8y, 8m, 8c, and 8k (hereinafter simply referred to as “transfer roller 8”) serving as transfer means are disposed.
[0031]
The photosensitive drum 1 serving as an image carrier is configured by applying an organic optical conductor layer (OPC) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm. The photosensitive drum 1 is rotatably supported at both ends by flanges, and is driven to rotate counterclockwise in FIG. 1 by transmitting a driving force from one driving motor (not shown) to one end.
[0032]
The primary charger 3 is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and a charging bias voltage is applied by a power source (not shown) to The surface is charged uniformly.
[0033]
The exposure means 4 has a polygon mirror, and this polygon mirror is irradiated with image light corresponding to an image signal from a laser diode (not shown).
[0034]
The developing unit 5 includes toner storage units 9y, 9m, 9c, and 9k (hereinafter simply referred to as “toner storage unit 9”) that store toners of yellow, magenta, cyan, and black, respectively, on the surface of the photosensitive drum 1. Developing rollers 10y, 10m, 10c, and 10k (hereinafter simply referred to as “developing roller 10”) that are adjacently driven and rotated by a driving unit (not shown) and that are developed by applying a developing bias voltage from a developing bias power source (not shown). And so on.
[0035]
From the upstream side in the transport direction of the transfer material S, the toner storage unit 9 stores toner of each color of yellow in the toner storage unit 9y, magenta in the toner storage unit 9m, cyan in the toner storage unit 9c, and black in the toner storage unit 9k. ing.
[0036]
The transfer roller 8 disposed inside the transfer material transport belt 2 is in contact with the transfer material transport belt 2 so as to face the four photosensitive drums 1 respectively. These transfer rollers 8 are connected to a transfer bias power source (not shown), and a positive charge is applied from the transfer roller 8 to the transfer material S via the transfer material conveying belt 2, and contacts the photosensitive drum 1 by this electric field. The negative color toner images on the surface of the photosensitive drum 1 are sequentially transferred onto the transfer material S, thereby forming a color image.
[0037]
A transfer material S made of paper, synthetic resin, or the like housed in a feeding cassette 11 provided at the lower part of the apparatus main body A is fed by a paper feed roller 12 and sent to a registration roller pair 14.
[0038]
The transfer material S sent at a predetermined timing by the registration roller pair 14 is electrostatically adsorbed by the transfer material conveyance belt 2 and is carried between the photosensitive drum 1 serving as image forming means and the transfer roller 8. After a toner image formed on the surface of each photosensitive drum 1 is transferred to a transfer position and sequentially transferred to record a color image, a heating roller 15a that rotates and a pressurization that rotates in contact with the heating roller 15a. After passing through a fixing means 15 having a roller 15b, the toner image is permanently fixed by being heated and pressurized, and then discharged onto a discharge tray 17 provided on the upper portion of the apparatus main body A by a discharge roller pair 16. The
[0039]
Next, an image forming operation in the mono color mode will be described with reference to FIG. FIG. 2 shows a state in which the image forming apparatus described above with reference to FIG. 1 is operated in the mono-color mode, and the same symbols indicate the same members.
[0040]
In the image forming apparatus of the present invention, the protrusions 24y, 24m, 24c, and 24k (hereinafter, simply referred to as “protrusion 24”) of the toner storage portion 9 of the process cartridge 7 are provided with the separation members 23y, 23m, 23c, and 23k ( Hereinafter, a configuration in which the photosensitive drum 1 and the developing roller 10 are separated from each other by rotating the separation member 23 up and down to rotate with reference to a fulcrum (not shown). It has become.
[0041]
When image formation is performed in the mono-color (monochrome) mode, the separation member 23 that is in contact with the protrusion 24 of the process cartridge other than black is moved to push up the protrusion 24 to separate the developing roller 10 from the photosensitive drum 1. In this state, image formation is performed.
[0042]
At the time of image formation, the photosensitive drum 1 of the process cartridge other than black also keeps rotating and obtains stable transfer material conveyance at the nip with the transfer material conveyance belt 2.
[0043]
With respect to the black process cartridge Bk, the separation member 23k is lowered, the photosensitive drum 1k and the developing means 5k are brought into contact with each other to develop the toner image, and the toner image is transferred to the transferred transfer material S.
[0044]
The cleaning means 6 is composed of a rubber blade and a sheet metal. The tip of the cleaning means 6 is brought into contact with the rotation of the photosensitive drum 1 in the counter direction so that the transfer residual toner on the photosensitive drum 1, the fogging toner for development, or the jam processing is performed. It has a function of scraping off generated dirt toner and sending it to a waste toner storage unit.
[0045]
As a method for supplying toner in the present embodiment, the bias applied to the primary charger 3 is turned off, the drum surface potential is reduced, the applied bias to the developing means is turned on, and all process cartridges are turned on. 7 is brought into contact with the photosensitive drum 1, and the toner on the developing roller 10 is transferred to the photosensitive drum 1 about the half circumference of the photosensitive drum 1. At this time, the transfer bias is turned off, the toner on the photosensitive drum 1 is passed through the transfer portion while being placed on the surface, conveyed to the cleaning means 6, and the toner is supplied to the cleaning means 6. In this embodiment, a series of operations for transferring the toner onto the drum and collecting it by the cleaning unit 6 is referred to as “toner supply operation”.
[0046]
On the other hand, the plurality of process cartridges By, Bm, Bc, Bk are respectively provided with storage means 25y, 25m, 25c, 25k (hereinafter simply referred to as “storage means 25”). The printer A includes reading / writing means (not shown) that reads and writes information stored in the storage means 25. The printer A reads a value relating to the process cartridge life calculated by a CPU (not shown), and The printer A is controlled in accordance with the written information, and in particular, the toner supply amount during the toner supply operation is changed in accordance with the degree of consumption of the photosensitive drum 1.
[0047]
In the present embodiment, the calculation is performed so as to represent the film thickness of the photosensitive drum 1. The calculation is performed by multiplying a weighting factor according to a state that affects the degree of wear on the photosensitive drum, such as ON / OFF of a bias for temporary charging, ON / OFF of development separation / contact, ON / OFF of a transfer bias, and process speed. A method of adding the rotation time of the body drum to the value stored in the storage means 25 is employed. At this time, weighting is performed so that the initial value is 0% and the lifetime is 100%.
[0048]
Further, the storage means stores in advance a set value for the timing of the toner supply operation in units of the degree of wear of the photosensitive drum 1. Also, a set value representing the toner supply amount at the time of toner supply operation at each time is stored. Further, it is assumed that the time when the process cartridge being used next supplies toner is to be stored. The storage means basically has a function of performing both reading and writing. These reading and writing operations can be performed without contact.
[0049]
Next, a sequence for performing the toner supply operation will be described with reference to FIG.
[0050]
After starting the image forming operation, information is read from the storage means 25 in step S1. The contents to be read are the degree of wear of the photosensitive drum 1, the set value, the toner supply amount, the next set value, and the next toner supply amount. In step S2, the consumption level of the photosensitive drum is compared with the set value. If the drum consumption level does not reach the set value indicating the timing of the toner supply operation, the image formation in step S5 is performed as it is. If the degree of wear of the photosensitive drum exceeds the set value, a toner supply operation is performed in step 3. Thereafter, the setting value, the toner supply amount, the next setting value, and the next toner supply amount are updated in the storage unit 25 in step 4, and then image formation is performed in step 5.
[0051]
In the present embodiment, the toner supply amount during the toner supply operation performed in step S3 is changed according to the degree of consumption of the photosensitive drum, and the most appropriate amount of toner is supplied to the cleaning unit. Therefore, the degree of wear and the supply amount will be described in more detail with reference to FIG.
[0052]
In FIG. 4, the horizontal axis represents the degree of consumption of the photosensitive drum, and the plotted white circle represents a set value for the timing of performing the toner supply operation. The vertical axis represents the toner supply amount at the time of toner supply operation at each time. In the present embodiment, the inventors have confirmed through experiments that there is a sufficient correspondence between the supply amount and the supply time.
[0053]
Therefore, the time when the developing bias is ON and the developing roller is in contact with the toner supply operation is changed in proportion to the toner supply amount setting value. According to FIG. 4, the photosensitive drum life is slightly increased in the first half and the second half. In the first half, the rubbing between the photosensitive drum and the cleaning unit is stabilized by basically increasing the amount, and in the second half, the life of the photosensitive member and the cleaning unit are deteriorated. Increase toner supply. The middle part of the service life is less than the first half and the second half to save toner consumption.
[0054]
Furthermore, in the present embodiment, the storage unit 25 stores in advance whether the process cartridge is unused or not, and the toner supply operation is performed according to the information. FIG. 5 shows the sequence of the toner supply operation for this unused cartridge, which will be described in detail below. First, in step S11, when the process cartridge is mounted and the door is closed, or when the printer is turned on, in step S12, information in the storage means 25 is read to obtain information on whether the cartridge is an unused cartridge. . In step 13, this information is judged, and if it is not used, the initial sequence of step 16 (conveying belt cleaning, jam paper detection, thermal fixing device temperature adjustment, etc.) is entered. If it is determined in step 13 that the process cartridge is not used, a toner supply operation is performed in step 14. Thereafter, in step 15, information indicating the cartridge already used is written in the storage means 25, and the initial sequence in step 16 is entered.
[0055]
When 10,000 image images were formed in the mono color mode with the image forming apparatus of the present embodiment, the toner is always present in the nip between the cleaning unit 6 and the photosensitive drum 1 so that appropriate slipperiness can always be maintained. High-quality images can be obtained over a long period of time, such as even when full-color printing is performed immediately, without occurrence of poor cleaning or uneven charging, and uniform halftone images can be obtained. Was confirmed.
[0056]
(Second Embodiment)
In the first embodiment, information for determining the toner supply operation timing and the toner supply amount at each time is written in advance in the storage means 25 of the process cartridge. Such information may be given to the person shown in the figure. By doing so, it is possible to widen the time spent for reading / writing the storage means of the printer main body and the process cartridge and the free space in the storage area of the storage means. Therefore, it is possible to further write detailed information about the lifetime in the storage means.
[0057]
In addition, with respect to the stability of the cleaning property, an effect equivalent to that of the first embodiment can be obtained.
[0058]
(Third embodiment)
In the present embodiment, the number of print images in the mono-color mode where printing is performed with a developing roller other than black separated from the photosensitive drum as a storage unit, and all the developing rollers are brought into contact with the photosensitive drum to perform printing. The number of print images in the full-color mode for performing the above is counted, and the supplied toner amount is corrected in accordance with the ratio of the number of images in these modes.
[0059]
FIG. 6A shows an example of a monocolor ratio with respect to the degree of consumption of the photosensitive drum. FIG. 6B shows the toner supply amount setting value. L1 in FIG. 6B is a graph for the first embodiment, and this set value was used when the monocolor ratio was 100%. Since the black cartridge always contacts and forms an image, correction is not performed. For the other process cartridges, the toner supply amount was corrected and slightly decreased as the monocolor ratio decreased.
[0060]
As described above, according to the present embodiment, it is possible to improve the stability of the cleaning property by correcting the toner supply amount according to the ratio of the mono color mode and the full color mode to a more appropriate value. become.
[0061]
(Fourth embodiment)
In the first to third embodiments, the toner supply timing is performed using the degree of wear of the photosensitive drum, but it may be performed using a print image. Further, although the toner supply amount is controlled by the supply time from the developing roller, it is also possible to use potential setting such as developing contrast, increasing the peripheral speed of the developing roller, or the like.
[0062]
【The invention's effect】
As described above, according to the present invention, by supplying an appropriate amount of toner to the nip between the cleaning means and the image carrier at an appropriate time, the frequency of image formation in the monocolor mode is high. However, stable photoconductor cleaning can be performed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the configuration of the image forming apparatus according to the embodiment;
FIG. 3 is a flowchart for explaining a sequence of image forming processing according to the embodiment;
FIG. 4 is a graph showing a relationship between the degree of consumption of the photosensitive drum and the toner supply amount during the toner supply operation in the image forming apparatus according to the embodiment;
FIG. 5 is a flowchart for explaining a sequence of image forming processing according to the embodiment;
FIG. 6 is a graph showing a relationship between a degree of wear of a photosensitive drum and a monocolor ratio in an image forming apparatus according to a third embodiment of the present invention.
FIG. 7 is a cross-sectional view showing the configuration of an example of a conventional image forming apparatus.
[Explanation of symbols]
A Color image forming apparatus 1, 1y, 1m, 1c, 1k Photosensitive drum 2 Transfer material conveying belt 3, 3y, 3m, 3c, 3k Primary charger 4, 4y, 4m, 4c, 4k Exposure means 5, 5y, 5m , 5c, 5k Developing means 6, 6y, 6m, 6c, 6k Cleaning means B, By, Bm, Bc, Bk Process cartridge 8, 8y, 8m, 8c, 8k Transfer roller 9, 9y, 9m, 9c, 9k Toner storage Sections 10, 10y, 10m, 10c, 10k Developing roller 11 Feed cassette 12 Feed roller 13 Separation pad 14 Registration roller pair 15 Fixing means 15a Heating roller 15b Pressure roller 16 Discharge roller pair 17 Discharge tray 18 Drive roller 19 Driven roller 21 Tension roller 22 Adsorption rollers 23, 23y, 23m, 23c, 23k Separation members 24, 24y, 24 m, 24c, 24k Protrusion 25, 25y, 25m, 25c, 25k Storage means

Claims (1)

An image bearing member capable of rotating with an electrostatic latent image supported on the surface, and a developing unit for bringing a developing roller into contact with the image bearing member and supplying a developer to the electrostatic latent image on the surface of the image bearing member for visualization. And a plurality of process cartridges including a cleaning unit that contacts the image carrier and cleans the surface of the image carrier, and is detachable from the image forming apparatus main body.
A transfer material conveying means for conveying the transfer material;
With
The plurality of process cartridges are arranged along a conveyance path of the transfer material conveyance unit, and a monocolor mode for forming an image on one image carrier in the plurality of process cartridges, and the plurality of processes It is possible to switch between full color mode for image formation on multiple image carriers in the cartridge,
In the mono-color mode, the image carrier of the process cartridge that does not perform image formation is separated from the developing roller,
An image forming apparatus having a configuration in which image carriers of the plurality of process cartridges are rotated regardless of whether image formation is not performed in the mono-color mode,
In the mono-color mode, an operation of supplying the developer from the developing unit to the cleaning unit of the process cartridge by bringing the image carrier of the process cartridge that does not perform the image formation at a predetermined timing and the developing roller into contact with each other. Done
The amount of developer supplied to the cleaning means of the process cartridge that does not perform image formation in the mono color mode is as follows:
The image forming apparatus, wherein the ratio of the mono color mode to the full color mode decreases as the ratio decreases.

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