JP3862423B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus.
[0002]
[Prior art]
FIG. 4 shows a conventional color image forming apparatus. This will be described with reference to the drawings.
[0003]
The photosensitive drum 101 as an image carrier is driven in the direction of the arrow in the figure by a driving unit (not shown) and is uniformly charged by the primary charger 102. Next, the exposure device 103 irradiates the photosensitive drum 101 with laser light L ′ according to the yellow image pattern, and a latent image is formed on the photosensitive drum 101.
[0004]
When the photosensitive drum 101 further advances in the direction of the arrow, the developing device 104a containing yellow toner among the developing devices 104a, 104b, 104c, and 104d supported by the rotating support 111 rotates so as to face the photosensitive drum 101. It is visualized by the selected developing device 104a.
[0005]
The intermediate transfer belt 105 rotates in the direction of the arrow at substantially the same speed as that of the photosensitive drum 101, and the intermediate transfer belt 105 is formed by a primary transfer bias applied to the primary transfer roller 108a for the toner image formed and supported on the photosensitive drum 101. Primary transfer is performed on the outer peripheral surface.
[0006]
By performing the above process for yellow, magenta, cyan, and black, toner images of a plurality of colors are formed on the intermediate transfer belt 105.
[0007]
Next, the transfer material is fed from the transfer material cassette 112 by the pickup roller 113 at a predetermined timing. At the same time, a secondary transfer bias is applied to the secondary transfer roller 108b, and the toner image is transferred from the intermediate transfer belt 105 to the transfer material.
[0008]
Further, the transfer material is conveyed to the fixing device 106 by the conveying belt 114 and melted and fixed, whereby a color image is obtained. Further, the transfer residual toner on the intermediate transfer belt 105 is cleaned by an intermediate transfer belt cleaner 115.
[0009]
On the other hand, the transfer residual toner on the photosensitive drum 101 is cleaned by a known cleaning device 107 of blade means.
[0010]
Further, the charging roller 102, the photosensitive drum 101, and the cleaning device 107 constitute an integral photosensitive drum cartridge A ', and are configured to be detachable from the main body together with the developing devices 104a, 104b, 104c, and 104d for the four colors. As a result, the user can easily perform member replacement and maintenance that have been performed by a service person.
[0011]
Further, an optical density sensor 109 as a detecting means is provided in the main body. Generally, in an electrophotographic color image forming apparatus, if the image density fluctuates due to various conditions such as changes in the environment used and the number of prints, the original correct color tone cannot be obtained.
[0012]
Accordingly, a toner image (patch) P ′ for density detection is created on the photosensitive drum 101 with each color toner on a trial basis, the density is detected by the density sensor 109, and the exposure amount, development bias, etc. are detected from the detection result. A stable image is obtained by performing image density control that applies feedback to the image.
[0013]
Image density control as described above is executed every time a predetermined number of sheets are printed, when the main body is turned on, and when the photosensitive drum cartridge A ′ or the developing devices 104a, 104b, 104c, and 104d are replaced.
[0014]
Next, as shown in FIG. 5, the density sensor 109 includes a light emitting element 91 such as an LED, a light receiving element 92 such as a photodiode, and a holder 93, and infrared light from the light emitting element 91 is transferred onto the photosensitive drum 101. The density of the patch P ′ is measured by irradiating the patch P ′ and measuring the reflected light from the patch P ′ by the light receiving element 92.
[0015]
The reflected light from the patch P ′ includes a regular reflection component and an irregular reflection component, and the regular reflection component is the state of the surface of the photosensitive drum 101 that is the base of the patch P ′ and the density sensor 109 and the patch P ′. Since the amount of light varies greatly due to the variation in distance, if the reflected light from the patch P ′ to be measured contains a regular reflection component, the detection accuracy is significantly reduced.
[0016]
Therefore, in this density sensor 109, when the normal I is used as a reference so that the regular reflection light from the patch P ′ does not enter the light receiving element 92, the irradiation angle to the patch P ′ is 45 °, and from the patch P ′. Only the irregularly reflected light is measured with the light receiving angle of the reflected light being 0 °.
[0017]
Here, the detection accuracy of the optical density sensor 109 as described above is gradually lowered when the measurement surface of the density sensor 109 is contaminated with toner or the like.
[0018]
In order to prevent this, it is easy to consider a method in which the measurement surface of the density sensor 109 is not soiled until the lifetime of the apparatus main body. In that case, a separation mechanism of the density sensor 109 or a movable dustproof window is used. It is necessary to provide it, which leads to an increase in complexity and cost of the apparatus.
[0019]
Therefore, in practice, a method in which the performance is maintained by regularly cleaning the detection surface of the density sensor 109 by a user or a service person.
[0020]
In the image forming apparatus of this example, every time a predetermined number of sheets are printed, a display prompting the user to clean the density sensor 109 is performed through a user interface panel (not shown). The detection accuracy of the density sensor 109 is maintained when the user cleans the density sensor 109.
[0021]
[Problems to be solved by the invention]
However, the conventional image forming apparatus has the following problems.
[0022]
As described above, when the density sensor 109 becomes dirty, the detection accuracy of the density sensor 109 decreases. Along with this, the control accuracy of image density control gradually decreases.
[0023]
On the other hand, when the user cleans the density sensor 109, the density sensor 109 is in a dirty state. In this case, the control accuracy of the image density control is slightly deteriorated.
[0024]
Further, some users do not immediately clean even if the device displays a stain on the density sensor 109, and after the density balance of the image has deteriorated significantly (that is, after the accuracy of image density control has deteriorated significantly). It is assumed that the sensor 109 is cleaned.
[0025]
However, since the image density control is executed every predetermined number of prints in the above-described conventional image forming apparatus, even if the density sensor 109 is cleaned, the print density balance is not improved immediately after that. Until the next image density control is executed, that is, until a predetermined number of sheets are printed, no improvement in image quality can be obtained.
[0026]
In order to avoid this problem, in the conventional image forming apparatus, after the density sensor 109 is cleaned, the user turns off the power of the main body to execute the image density control. This was not necessarily the best method from the viewpoint of usability.
[0027]
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to automatically perform image density control when it is determined that the detection portion of the detection means has been cleaned. An object of the present invention is to provide an image forming apparatus that improves the image quality immediately after cleaning the detection unit.
[0028]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides:
An image forming apparatus comprising: a detecting unit that detects a density of a density detection toner image; and a unit that controls an image forming condition based on the density detection result, and detects a contamination level of a detection unit of the detecting unit. ,
There line control of the image forming conditions by the concentration detection results for each predetermined number of image formation,
Regardless of the predetermined number of image formations, the image forming conditions are controlled by the density detection result according to the previous contamination level of the detection unit of the detection unit and the current contamination level of the detection unit of the detection unit. It is characterized by determining whether to do.
[0032]
Also, contamination level of the detector, it is also preferable to be determined based on the output value of said detecting means relative to the surface of the image bearing member to be a base of the density detecting toner image.
In addition, when the previous contamination level of the detection unit is equal to or higher than a predetermined value and the current contamination level of the detection unit is equal to or lower than a predetermined value, it is preferable to control the image forming condition based on the density detection result.
[0033]
Further, a detection unit for detecting the density of the density detection toner image, a unit for controlling the image forming condition based on the density detection result, and opening / closing of the door that is opened and closed when cleaning the detection unit of the detection unit is determined. And an image forming apparatus for detecting a contamination level of a detection unit of the detection unit,
There line control of the image forming conditions by the concentration detection results for each predetermined number of image formation,
Regardless of the predetermined number of image forming sheets, whether to control the image forming condition based on the density detection result according to the opening / closing of the door and the contamination level of the detecting unit of the detecting means before opening the door It is characterized by judging.
It is also preferable that the contamination level of the detection unit is determined based on an output value of the detection unit with respect to the surface of the image carrier serving as a background of the density detection toner image.
In addition, when the door is opened and closed and the contamination level of the detection unit before the door is opened is equal to or higher than a predetermined value, it is also preferable to control the image forming conditions.
[0034]
Furthermore, the detection means is preferably an optical density sensor.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below based on the illustrated embodiments.
[0036]
(Embodiment 1)
FIG. 1 is a cross-sectional view of an image forming apparatus representing Embodiment 1 of the present invention.
[0037]
The photosensitive drum 1 serving as an image carrier is driven in the direction indicated by an arrow by a driving unit (not shown) and is uniformly charged by a primary charger 2. Next, laser light L according to the yellow image pattern is irradiated from the exposure device 3 to the photosensitive drum 1, and a latent image is formed on the photosensitive drum 1.
[0038]
When the photosensitive drum 1 further advances in the direction of the arrow, the developing device 4a containing yellow toner among the developing devices 4a, 4b, 4c, and 4d supported by the rotary support 11 rotates so as to face the photosensitive drum 1. It is visualized by the selected developing device 4a.
[0039]
The intermediate transfer belt 5 rotates in the direction of the arrow at substantially the same speed as the photosensitive drum 1, and the intermediate transfer belt 5 is formed by a primary transfer bias applied to the primary transfer roller 8 a with the toner image formed and supported on the photosensitive drum 1. Primary transfer is performed on the outer peripheral surface.
[0040]
By performing the above process for yellow, magenta, cyan, and black, toner images of a plurality of colors are formed on the intermediate transfer belt 5.
[0041]
Next, the transfer material is fed from the transfer material cassette 12 by the pickup roller 13 at a predetermined timing. At the same time, a secondary transfer bias is applied to the secondary transfer roller 8b, and the toner image is transferred from the intermediate transfer belt 5 to the transfer material.
[0042]
Further, the transfer material is conveyed to the fixing device 6 by the conveyance belt 14 and melted and fixed, whereby a color image is obtained. Further, the transfer residual toner on the intermediate transfer belt 5 is cleaned by an intermediate transfer belt cleaner 15.
[0043]
On the other hand, the transfer residual toner on the photosensitive drum 1 is cleaned by a known cleaning device 7 of blade means.
[0044]
Further, the charging roller 2, the photosensitive drum 1, and the cleaning device 7 constitute an integrated photosensitive drum cartridge A, and are configured to be detachable from the main body together with the developing devices 4a, 4b, 4c, and 4d for the four colors.
[0045]
Further, the optical density sensor 9 as the detecting means has the same configuration and operation as the conventional example shown in FIG.
[0046]
Next, stain detection of the density sensor 9 used in this embodiment will be described. The stain detection is determined by a change in the sensor output value of the photosensitive drum 1 that is the background of the density detection toner image (patch) P.
[0047]
Here, a photosensitive drum 1 whose density does not change throughout the sheet passing durability is used. In such a case, the detected value of the density sensor 9 with respect to the surface of the photosensitive drum 1 is a constant value unless the density sensor 9 is dirty, and gradually decreases as the lens surface of the density sensor 9 becomes dirty. Therefore, it is determined whether or not the concentration sensor 9 is cleaned from the fluctuation of this value.
[0048]
Next, the control of the present embodiment will be described in detail according to the flowchart of FIG.
[0049]
In the present embodiment, the presence / absence of cleaning of the density sensor 9 is detected every time immediately before printing.
[0050]
First, when a print execution command is input to the main body CPU, a cleaning presence / absence detection sequence of the density sensor 9 is started.
[0051]
(STEP1)
First, the sensor output value X1 for the surface of the photosensitive drum 1 is measured by the density sensor 9.
[0052]
(STEP2)
The sensor dirt level α0 is calculated from the output value X1 according to the following formula 1.
[0053]
[Expression 1]
α0 = X1 / X0
Here, X0 is a reference output value when the photosensitive drum 1 is measured in a state where the density sensor 9 is not soiled at all, and is set to a predetermined value in advance. Accordingly, when the density sensor 9 is not soiled at all, the soil level α0 is 1, and as the density sensor 9 becomes soiled, α0 decreases.
[0054]
(STEP3)
It is determined whether the density sensor 9 is extremely dirty. When the dirt level α0 of the density sensor 9 is smaller than 0.8, it is determined that the density sensor 9 is extremely dirty.
[0055]
(STEP4)
Since it is necessary to clean the density sensor 9, the density sensor dirt is displayed on the user interface panel.
[0056]
(STEP5)
It is determined in what state the dirt level α1 of the density sensor 9 was in the previous measurement. Α1 is stored in advance in a memory in the main body CPU. If α1 is smaller than 0.8, it is determined that the density sensor 9 is dirty at the previous measurement, and the process proceeds to STEP 6 for cleaning the density sensor 9.
[0057]
(STEP6)
Whether or not the density sensor 9 is cleaned is determined. If the density sensor 9 is dirty at the previous measurement and the measured dirt level α0 is greater than 0.95, it is determined that the density sensor 9 has been cleaned.
[0058]
(STEP7)
When the density sensor 9 is cleaned, image density control is newly executed.
[0059]
(STEP8)
The dirt level α1 stored in the main body CPU is updated and the process ends.
[0060]
As described above, in the present embodiment, when it is determined that the density sensor 9 has been cleaned, the image density control is automatically executed to improve the image quality immediately after the density sensor 9 is cleaned. explained.
[0061]
(Embodiment 2)
The image forming apparatus used in the present embodiment is substantially the same as the apparatus used in the first embodiment, description of the common configuration is omitted, and only the mechanism peculiar to the present embodiment is shown in FIG. This will be described using a cross-sectional view.
[0062]
In FIG. 1, the door sensor 17 is installed to detect the opening and closing of the door B that is opened when the concentration sensor 9 is cleaned. The door B also serves as a replacement door for the photosensitive drum cartridge A.
[0063]
Further, in the photosensitive drum cartridge A, a non-volatile ROM 18 is provided for determining whether or not the photosensitive drum cartridge A is replaced. Different data for each photosensitive drum cartridge is stored in the ROM 18 in advance, and the main body CPU reads the contents and compares them to detect replacement of the photosensitive drum cartridge A.
[0064]
In this embodiment, image density control is performed when the power is turned on, every 100 prints, when the photosensitive drum cartridge A is replaced, and when the developing cartridge is replaced.
[0065]
Further, after execution of image density control, the dirt level of the density sensor 9 is always detected, and the dirt level of the density sensor 9 is stored in the main body CPU.
[0066]
The method for calculating the dirt level is the same as in the first embodiment.
[0067]
Next, the control of the present embodiment will be described in detail according to the flowchart of FIG.
[0068]
First, the sequence of the present embodiment starts when the main body CPU detects opening and closing of the door B.
[0069]
(STEP11)
Since the door B is opened and closed when the density sensor 9 is cleaned or the photosensitive drum cartridge A is replaced, it is first determined whether or not the photosensitive drum cartridge A has been replaced. If the photosensitive drum cartridge A has been replaced, it is necessary to perform new image density control, so the process proceeds to STEP13.
[0070]
(STEP12)
It is determined what state the dirt level α1 of the density sensor 9 was when the density sensor 9 was previously measured for dirt. Α1 is stored in advance in a memory in the main body CPU. If α1 is smaller than 0.8, it is determined that the density sensor 9 is dirty at the previous measurement. In this case, since it is considered that the door B was opened and closed for cleaning the density sensor 9, the image density control in STEP 13 is performed.
[0071]
(STEP 13)
Perform image density control.
[0072]
(STEP14)
A sensor output value X 1 for the surface of the photosensitive drum 1 is measured by the density sensor 9.
[0073]
(STEP 15)
The dirt level α0 of the density sensor 9 is calculated from the output value X1 in accordance with the following formula 2 as in the first embodiment.
[0074]
[Expression 2]
α0 = X1 / X0
(STEP16)
The dirt level α1 stored in the main body CPU is updated and the process ends.
[0075]
As described above, in the present embodiment, whether or not the concentration sensor 9 is cleaned is determined based on the dirt level of the concentration sensor 9 and the opening / closing detection of the cleaning door B of the concentration sensor 9, and it is determined that the concentration sensor 9 has been cleaned. In this case, the image density control is automatically executed to improve the image quality immediately after the density sensor 9 is cleaned, and further, the stain level detection of the density sensor 9 is performed only immediately after the image density control. A method for reducing the number of detections has been described.
[0076]
As described above, in the present embodiment, the optical density sensor is described as the detection unit. However, the detection unit can be applied to an electrostatic sensor that detects the electrostatic capacitance of the toner image and other non-optical detection units.
[0077]
Alternatively, the detection unit may be determined to have been cleaned only by detecting the opening / closing of a door that is opened and closed when the detection unit of the detection unit is cleaned.
[0078]
【The invention's effect】
The present invention has the above-described configuration and operation. When it is determined that the detection unit of the detection unit has been cleaned, the image forming condition is automatically controlled, thereby cleaning the detection unit. Improving the image quality immediately after.
[0079]
Further, the means for determining that the cleaning operation of the detection portion of the detection means has been performed is based on the change in the output value of the detection means with respect to the surface of the image carrier that is the base of the density detection toner image. Since the contamination level of the detection unit can be determined, an electrical system can be used without increasing the number of physical devices.
[0080]
Further, when the contamination level of the detection unit before opening the door that is opened and closed when cleaning the detection unit is a predetermined value or more, it is determined that the cleaning has been performed by opening and closing the door, and image forming conditions By automatically executing this control, it is possible to obtain an improvement in image quality immediately after cleaning the detection unit.
[0081]
Further, it is determined that the detection unit has been cleaned by opening and closing a door that is opened and closed when the detection unit is cleaned, and the control of the image forming conditions is automatically executed. Improving the image quality immediately after cleaning the detection unit is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining a first embodiment of the present invention;
FIG. 3 is a flowchart for explaining a second embodiment of the present invention.
FIG. 4 is a schematic sectional view of a conventional image forming apparatus.
FIG. 5 is an explanatory diagram of an optical density sensor according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Primary charger 3 Exposure apparatus 4a, 4b, 4c, 4d Developing device 5 Intermediate transfer belt 6 Fixing device 7 Cleaning device 8a Primary transfer roller 8b Secondary transfer roller 9 Density sensor 12 Transfer material cassette 13 Pickup roller 14 Conveyance Belt 15 Intermediate transfer belt cleaner 17 Door sensor 18 Non-volatile ROM
91 Light Emitting Element 92 Light Receiving Element 93 Holder A Photosensitive Drum Cartridge B Door L Laser Light P Patch

Claims (7)

An image forming apparatus comprising: a detecting unit that detects a density of a density detection toner image; and a unit that controls an image forming condition based on the density detection result, and detects a contamination level of a detection unit of the detecting unit. ,
There line control of the image forming conditions by the concentration detection results for each predetermined number of image formation,
Regardless of the predetermined number of image formations, the image forming conditions are controlled by the density detection result according to the previous contamination level of the detection unit of the detection unit and the current contamination level of the detection unit of the detection unit. An image forming apparatus that determines whether or not to perform. The image forming apparatus according to claim 1 , wherein the contamination level of the detection unit is determined based on an output value of the detection unit with respect to a surface of an image carrier serving as a base of a density detection toner image. Claim 1 previous contamination level of the detection unit, characterized in that performing the event that the present level of contamination of the detector is equal to or less than the predetermined value, the control of the image forming conditions by the density detection result above a predetermined value or the image forming apparatus according to 2. Detection means for detecting the density of the toner image for density detection, means for controlling image forming conditions based on the density detection result, and means for determining opening / closing of the door that is opened and closed when cleaning the detection unit of the detection means And an image forming apparatus for detecting a contamination level of a detection unit of the detection unit,
There line control of the image forming conditions by the concentration detection results for each predetermined number of image formation,
Regardless of the predetermined number of image forming sheets, whether to control the image forming condition based on the density detection result according to the opening / closing of the door and the contamination level of the detecting unit of the detecting means before opening the door An image forming apparatus characterized by The image forming apparatus according to claim 4 , wherein the contamination level of the detection unit is determined based on an output value of the detection unit with respect to a surface of an image carrier serving as a base of a density detection toner image. The opening and closing of the door is performed, when the detection part of the contamination level before opening the door is equal to or larger than a predetermined value, according to claim 4 or 5, characterized in that for controlling the image forming conditions Image forming apparatus. The detecting device, an image forming apparatus according to any one of claims 1 to 6, characterized in that the concentration sensor optical.

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