JP3699815B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, or a fax machine.
[0002]
[Prior art]
A contact transfer method in which an image obtained by superimposing a single color or a plurality of colors on a photoconductor is primarily transferred to an intermediate transfer medium having a medium resistance and secondarily transferred onto a transfer sheet by contact transfer using a paper transfer roller is disclosed in Japanese Patent Laid-Open No. Hei. No. 02-15170.
[0003]
[Problems to be solved by the invention]
However, in the system in which an image obtained by superimposing a single color or a plurality of colors on a photoconductor is primarily transferred to an intermediate transfer medium having a medium resistance, and is secondarily transferred to transfer paper by contact transfer using a paper transfer roller, As a result, the transfer body deteriorates and the resistance value decreases.
[0004]
When the resistance value of the intermediate transfer member decreases, the transfer bias easily flows to the intermediate transfer member whose resistance has decreased, and the optimum transfer bias condition is lost, and the portion with the reduced resistance becomes an abnormal image. .
[0005]
The decrease in the resistance of the intermediate transfer member is, as shown in FIG. 7, left non-sheet passing, which is a portion where the transfer sheet 101 is not passed between the intermediate transfer member 100 and the contact transfer type paper transfer roller 102. This is because the resistance of the portion 100b and the right non-sheet passing portion 100c is likely to decrease. That is, if the transfer paper 101 has a size that is less than or equal to the maximum passable size, for example, the maximum passable size is A3 paper, the transfer paper 101 is transferred onto the intermediate transfer body 100 when the A4 size transfer paper 101 is repeatedly used. Portions that are not passed, in other words, left non-sheet passing portions 100b and right non-sheet passing portions 100c, which are portions where the intermediate transfer body 100 and the paper transfer roller 102 are in direct contact, are formed. In both the non-sheet passing portions, the bias applied to the paper transfer roller is more likely to flow than the sheet passing portion 100a which is a portion through the transfer paper 101 having a high resistance. As a result, both non-sheet passing portions of the intermediate transfer body 100 are deteriorated, and the resistance of this portion is reduced.
[0006]
There is no problem as long as the resistance of the intermediate transfer body 100 is uniform as a whole. However, when a sheet having a size not larger than the maximum sheet passing capacity is repeatedly passed through the transfer sheet 101 as described above, both the non-sheet passing section and the sheet passing section are used. When the resistance value is uneven at 100a and the sheet having the maximum sheet passing size is subsequently passed, the transfer bias is not uniformly applied, and the portion having a low resistance value is blanked, resulting in an abnormal image (density unevenness).
[0007]
Based on the above-described matters, the surface resistance value of each part in the sheet passing portion 100a, the left non-sheet passing portion 100b, and the right sheet passing portion 100c of the intermediate transfer member 100 was measured. As a result of measurement, the surface resistance of the left non-sheet passing portion 100b is 1.19 × 10.⁸Ω / cm²The surface resistance of the paper passing portion 100a is 5.40 × 10⁸Ω / cm²The surface resistance of the right non-sheet passing portion 100c is 5.74 × 10⁷Ω / cm²Met. As is apparent from the measurement result, both non-sheet passing portions of the intermediate transfer member have lower resistance than the sheet passing portion 100a and are deteriorated.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to find an abnormality in the intermediate transfer member and prevent the occurrence of abnormal images such as white spots (density unevenness).
[0009]
[Means for Solving the Problems]
  According to the first aspect of the present invention, there is provided a photosensitive member that carries a toner image, an intermediate transfer member that transfers a toner image on the photosensitive member, and a plurality of members in a longitudinal direction that is perpendicular to the moving direction of the surface of the intermediate transfer member. A detection unit that detects the amount of toner that is arranged and transferred onto the intermediate transfer member, a control unit that compares a detection value from the detection unit, and controls the apparatus in accordance with the detected value; An image forming apparatus in which the control unit detects a detection value as resistance value unevenness of the intermediate transfer member, and the control unit limits a copyable document to a character image document based on the detection value from the detection unit. It is characterized by that.
[0011]
  According to a second aspect of the present invention, there is provided a photosensitive member carrying a toner image, an intermediate transfer member for transferring the toner image of the photosensitive member, and movable on the intermediate transfer member. The detection means for detecting the toner amount at a plurality of locations, the control means for comparing the detection value by the detection means, and controlling the apparatus according to the value, and the control means for obtaining the detection value from the detection means. An image forming apparatus that detects an uneven resistance value of an intermediate transfer member, wherein the control unit limits a copyable document to a character image document based on a detection value from the detection unit.
[0012]
  According to the first and second aspects of the present invention, when the detection value by the detection unit satisfies a predetermined condition, the control unit limits the subsequent copy-capable documents to character images. In other words, the intermediate transfer member having a long life can be used to some extent.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
A color copying apparatus to which the present invention is applied will be described below. FIG. 1 is a schematic configuration diagram of a color copying apparatus 50 according to the present invention, and FIG. 2 is an enlarged view around an intermediate transfer belt as a photosensitive member and an intermediate transfer member. The configuration and operation of this apparatus will be described below.
[0034]
A color image reading apparatus (hereinafter referred to as a “color scanner”) 1 forms an image of an original 3 on a color sensor 7 via an illumination lamp 4, a mirror group 5, and a lens 6 to obtain color image information of the original. Is read for each color separation light of, for example, blue, green and red, and converted into an electrical image signal. Then, based on the color separation image signal intensity levels of blue, green, and red obtained by the color scanner 1, color conversion processing is performed by an image processing unit (not shown), and black (hereinafter referred to as “BK”). ), Cyan (hereinafter referred to as “C”), magenta (hereinafter referred to as “M”), and yellow (hereinafter referred to as “Y”) color image data.
[0035]
This is visualized in BK, C, M, and Y by a color image recording apparatus (hereinafter referred to as “color printer”) 2 described below, and these are superimposed to form a four-color full-color image. .
[0036]
Next, an outline of the color printer 2 will be described. The writing optical unit 8 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 9.
[0037]
The photosensitive drum 9 rotates counterclockwise as indicated by an arrow. Around the photosensitive drum 9, a photosensitive member cleaning unit (including a pre-cleaning static eliminator) 10, a static elimination lamp 11, a charger 12, a potential sensor 13, and a BK developing unit 14 are provided. A C developing unit 15, an M developing unit 16, a Y developing unit 17, a developing density pattern detector 18, an intermediate transfer belt 19 as an intermediate transfer member, and the like are arranged. Each developing device includes developing sleeves 14a, 15a, 16a, and 17a that rotate so that the developer faces the photoreceptor 9 in order to develop the electrostatic latent image, and a developing paddle that rotates to pump up and stir the developer. 14b, 15b, 16b, 17b and developer toner density detection sensors 14c, 15c, 16c, 17c. The order of development operations (color image formation order) will be described below using examples of BK, C, M, and Y. However, the image forming order is not limited to this.
[0038]
When the copying operation is started, reading of the BK image data is started from the color scanner 1 at a predetermined timing, and optical writing by the laser beam and latent image formation are started based on this image data. (Hereinafter, the electrostatic latent image based on the BK image data is referred to as “BK latent image”. The same applies to C, M, and Y.) The developing position of the BK developing unit 14 is set so that development can be performed from the leading end of the BK latent image. Before the leading edge of the latent image arrives, the developing sleeve 14a starts rotating to develop the BK latent image with BK toner. Thereafter, the developing operation of the BK latent image area is continued, but when the rear end of the BK latent image has passed the BK developing position, the development inoperative state is set. This is completed at least before the leading edge of the C latent image by the next C image data arrives.
[0039]
The BK toner image formed on the photosensitive member 9 is transferred onto the surface of the intermediate transfer belt 19 that is driven at the same speed as the photosensitive member 9 (hereinafter, the toner image transfer from the photosensitive member 9 to the intermediate transfer belt 19 is referred to as “ Called belt transfer). The belt transfer is performed by applying a predetermined bias voltage to the transfer bias roller 20 while the photoconductor 9 and the intermediate transfer belt 19 are in contact with each other. The intermediate transfer belt 19 sequentially aligns the BK, C, M, and Y toner images formed on the photosensitive member 9 on the same surface to form a four-color belt transfer image. Perform batch transfer. The configuration and operation of the intermediate transfer belt unit 60 will be described later.
[0040]
By the way, on the photoconductor 9 side, the process proceeds to the C process after the BK process, but C image data reading by the color scanner 1 starts at a predetermined timing, and a C latent image is formed by laser beam writing with the image data.
[0041]
The C developing unit 15 starts to rotate the developing sleeve 15a after the rear end of the previous BK latent image has passed with respect to the developing position and before the leading end of the C latent image has passed, and the C latent image is converted into the C latent image. Develop with toner. Thereafter, development of the C latent image area is continued, but when the rear end portion of the latent image passes, the development inoperative state is set in the same manner as in the previous BK developing unit. This is also completed before the leading edge of the next M latent image arrives. In addition, about the process of M and Y, each image data is read. Since the latent image forming and developing operations are the same as those in the above-described steps BK and C, description thereof will be omitted.
[0042]
Next, the intermediate transfer belt unit 60 will be described. The intermediate transfer belt 19 is stretched around a drive roller 21, a belt transfer bias roller 20, a tension roller 39, and a driven roller group, and is driven and controlled as described later by a drive motor. Further, the maximum sheet passing size of the transfer belt 19 is set to A3 vertical. That is, the width in the direction perpendicular to the moving direction of the transfer belt 19 is substantially the same as the vertical width of A3.
[0043]
The belt cleaning unit 22 includes a brush roller 22a, a rubber blade 22b, a contact / separation mechanism 22c from the belt, and the like. After the first color BK image is transferred to the belt, the second, third, and fourth colors are transferred to the belt. During this time, the contact / separation mechanism 22c is separated from the belt surface.
[0044]
The paper transfer unit 23 includes a paper transfer bias roller 23a, a roller cleaning blade 23b, a contact / separation mechanism 23c from the belt, and the like. The bias roller 23 a is usually separated from the surface of the intermediate transfer belt 19, but is contacted at a timing when the four color superimposed images formed on the surface of the intermediate transfer belt 19 are collectively transferred to the transfer paper 24. It is pressed by the separation mechanism 23c, and a predetermined bias voltage is applied to the roller 23a to perform transfer onto the transfer paper 24. The transfer paper 24 is fed by a paper feed roller 25 and a registration roller 26 in accordance with the timing when the leading end of the four-color superimposed surface image on the surface of the intermediate transfer belt 19 reaches the paper transfer position.
[0045]
The intermediate transfer belt 19 is moved by a constant speed forward movement method, a skip forward movement method, or a reciprocating movement (quick return) as an operation method after the belt transfer of the BK toner image of the first color is completed to the rear end. There are three methods, and one of these methods is used, or the operation is performed by a combination of efficient methods (in terms of copy speed, etc.) according to the copy size.
[0046]
An outline of the constant speed forward movement method is described below. Even after the transfer of the BK toner image to the belt, the forward movement continues at a constant speed. When the front end position of the BK image on the surface of the intermediate transfer belt 19 reaches the belt transfer position at the contact portion with the photoconductor 9 again, the front end portion of the next C toner image is exactly at that position on the photoconductor 9 side. As shown, the image is formed with the timing. As a result, the C image is accurately transferred to the BK image and superimposed on the surface of the intermediate transfer belt 19 and transferred onto the belt. Thereafter, the same operation is followed to proceed to the M and Y image processes to obtain a four-color superimposed belt transfer image. The four-color superimposed toner image on the surface of the intermediate transfer belt 19 is collectively transferred to the transfer paper 24 as described above while moving forward as it is after the fourth color Y toner image belt transfer step.
[0047]
The outline of the skip forward method is described below. When the belt transfer of the BK toner image is completed, the intermediate transfer belt 19 is separated from the surface of the photosensitive member 9, and is skipped by one high speed in the forward movement direction as it is, and when the predetermined amount is moved, the original forward movement speed is restored. Thereafter, the intermediate transfer belt 19 is brought into contact with the photosensitive member 9 again. When the leading edge position of the BK image on the surface of the intermediate transfer belt 19 reaches the belt transfer position again, the photoconductor 9 side forms an image at a timing so that the leading edge of the next C toner image is exactly at that position. Has been. As a result, the C image is accurately aligned with the BK image and superimposed and transferred onto the belt. Thereafter, the same operation is followed to proceed to the M and Y image processes to obtain a four-color superimposed belt transfer image. The four-color superimposed toner images on the surface of the intermediate transfer belt 19 are collectively transferred onto the transfer paper 24 at the same forward speed as the fourth color Y toner image belt transfer step.
[0048]
The outline of the reciprocating (quick return) method is described below. When the belt transfer of the BK toner image is completed, the intermediate transfer belt 19 is separated from the surface of the photoreceptor 9, and the forward movement is stopped and at the same time the high speed return is performed in the reverse direction. In the return, the front end position of the BK image on the surface of the intermediate transfer belt 19 passes through the belt transfer equivalent position in the reverse direction, and further moves by a preset distance, and then stops and enters a standby state. Next, when the leading end portion of the C toner image on the photoconductor 9 side reaches a predetermined position before the belt transfer position, the intermediate transfer belt 19 is started again in the forward movement direction. Further, the intermediate transfer belt 19 is brought into contact with the surface of the photoreceptor 9 again. Also in this case, the C image is transferred to the belt under control of conditions such that the C image accurately overlaps the BK surface image on the surface of the intermediate transfer belt 19. Thereafter, the same operation is followed to proceed to the M and Y image processes to obtain a four-color superimposed belt transfer image. Following the belt transfer process of the Y toner image of the fourth color, the four-color superimposed toner image on the surface of the belt 19 is transferred to the transfer paper 24 at once without moving back at the same speed.
[0049]
The transfer paper 24 onto which the four-color superimposed toner images have been collectively transferred from the surface of the intermediate transfer belt is conveyed to a fixing device 28 by a paper conveyance unit 27, and is toner by a fixing roller 28a and a pressure roller 28b controlled to a predetermined temperature. The image is fused and transported to a copy tray 29 to obtain a full color copy. The surface of the photosensitive member 9 after the belt transfer is cleaned by the photosensitive member cleaning unit 10 and is uniformly discharged by the discharging lamp 11.
[0050]
The intermediate transfer belt 19 after transferring the toner image to the transfer paper 24 cleans the surface by pressing the cleaning unit 22 again with the contact / separation mechanism 22c.
At the time of repeat copy, the operation of the color scanner 1 and the image formation on the photosensitive member 9 are performed at a predetermined timing following the first Y (fourth color) image process to the second BK (first color) image process. move on. Further, the intermediate transfer belt 19 transfers the second BK toner image to the area where the surface is cleaned by the cleaning unit 22 following the batch transfer process of the first four-color superimposed image to the transfer paper 24. To be. After that, the operation is the same as the first sheet.
[0051]
The transfer paper cassettes 30, 31, 32, and 33 store transfer papers of various sizes. The transfer paper cassettes 30, 31, 32, and 33 are fed in the direction of the registration roller 26 in a timed manner from the size paper storage cassette designated on the operation panel (not shown). Be transported. The manual paper feed tray 34 stores OHP paper, cardboard, and the like.
[0052]
The copy mode for obtaining four full colors has been described above. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. In the single color copy mode, only the developing device for that color is in a developing operation state until the predetermined number of sheets is completed, and the intermediate transfer belt 19 is kept in contact with the surface of the photosensitive member 9 at a constant speed in the forward movement direction. The copying operation is performed while the belt cleaner 22 is driven and the intermediate cleaner belt 19 is still in contact with the belt cleaner 22.
[0053]
The resistance value of the intermediate transfer belt 19 is the same in the longitudinal direction, which is a direction perpendicular to the moving direction of the surface of the intermediate transfer belt 19 in the initial use of the intermediate transfer belt 19. However, as the sheet passing is repeated, for example, after passing thousands of sheets, as shown in FIG. 3, the sheet passing portion 19a, the left non-passing portion 19b, and the right non-passing portion of the intermediate transfer belt 19 Differences occur in the resistance values at the respective portions 19c. In this embodiment, the width in the longitudinal direction of the sheet passing portion 19a is set to the A4 vertical width. When the resistance value is thus different, a difference is generated in the formed image density even if the documents have the same density (color). This is particularly noticeable in halftones and causes a problem. In this embodiment, the following configuration is adopted.
[0054]
As shown in FIG. 4, on the transfer surface of the intermediate transfer belt 19, a toner amount detection means (hereinafter referred to as “toner sensor”) is positioned between the tension roller 39 and the drive roller 21 and facing the intermediate transfer belt 19. .) 40 is arranged, and is connected to a control unit 41 which is a control means.
[0055]
The control unit 41 is also connected to an operation unit 43 and a calculation unit 45, which will be described later, and is where information from each part is transferred and the device is controlled. The operation unit 43 is operated by a user or the like from outside the apparatus, sends information to the control unit 41, determines various settings to be described later, and performs various operations on the apparatus. The calculation unit 45 cumulatively measures the length and the number of transfer sheets, and notifies the control unit 41 when it reaches a certain value.
[0056]
The toner sensor 40 changes its output potential (V) in accordance with the amount of toner, that is, the toner concentration. The lower the toner concentration, the larger the output value (V) of the potential of the toner sensor 40. Two toner sensors 40 are arranged at equal intervals on the sheet passing portion 19a of the intermediate transfer belt 19 and one on each non-sheet passing portion (see FIG. 3), and detect the toner density at each position. It can be done. Specifically, the output value (V) detected by the toner sensor 40 is transmitted to the control unit 41. Then, the control unit 41 transmits information corresponding to the output value (V) (in this case, toner density) to the operation unit 43, and the operation unit 43 displays this information. More specifically, the toner density is low because the potential holding force is weak where the resistance on the intermediate transfer belt 19 is low, and the toner holding force is also weak. Therefore, the control unit 41 detects the uneven resistance value of each part in the longitudinal direction of the intermediate transfer belt 19 based on the detected toner density, and displays it on the operation unit 43.
[0057]
The control unit 41 can also determine the life of the intermediate transfer belt 19 from the detection value obtained from the toner sensor 40. As a determination method, if the difference in toner density with respect to the same original density in each part of the intermediate transfer belt 19 exceeds a predetermined value, it is determined that the intermediate transfer belt 19 has reached the end of its life due to deterioration. .
[0058]
The deterioration determination method described above will be described below. An example of the output value (V) of the toner sensor 40 is shown in FIG. In the graph of FIG. 5, the vertical axis represents the output value (V) of the toner sensor 40, and the horizontal axis represents the width of the intermediate transfer belt 19 and the arrangement position of the toner sensor 40. Incidentally, F is the left end (left end of the intermediate transfer belt 19) of the left non-sheet passing portion 19b, C is the center of the sheet passing portion 19a (center of the intermediate transfer belt), and R is the right end (right end of the right non-sheet passing portion 19c). This represents the right end of the intermediate transfer belt 19. As can be seen, the output value (V) of the toner sensor 40 varies greatly between the sheet passing portion 19a and the two non-sheet passing portions in the A4 length, and the difference is about 0.5 (V). Here, when the reference value for determining whether or not the lifetime is 0.4 (V), for example, and this reference is set in the control unit 41, the intermediate transfer belt 19 is 0.5 (V). Therefore, the control unit 41 determines that the lifetime is reached. In determining the reference value, it is preferable to set the reference value to a value that may cause a complaint from the user such as an abnormality when a density difference exceeding this value occurs. As described above, when the control unit 41 determines that the intermediate transfer belt 19 is at the end of its life, the information is displayed on the operation unit 43. Hereinafter, some items to be set in the control unit 41 will be described.
[0059]
When the difference between the detected values at each position on the surface of the intermediate transfer belt 19 is larger than a predetermined reference value of 0.4 (V), the original life is limited if the subsequent document images are limited. The intermediate transfer belt 19 thus obtained can be used to some extent. This is because the difference in image density due to this resistance difference is most noticeable in the halftone image and is not so noticeable in the Bunyu image. Therefore, after the output from the toner sensor 40 exceeds the reference value, the control unit 41 can be set so that the subsequent image is limited to the character image. In such a manner, a message indicating that is displayed on the operation unit 43, or a device that can select a character mode, a photo mode, an automatic separation mode, or the like depending on the type of document, may be set such that only the character mode can be selected. Of course, even if only the character mode is selected, the density difference can be recognized as the resistance further decreases. Therefore, it is necessary to set the reference in this case in the control unit 41 as well. For example, when the resistance difference exceeds 0.6 (V), the operation unit 43 prompts replacement of the intermediate transfer belt 19.
[0060]
As a method for easily and appropriately detecting the resistance value unevenness of the intermediate transfer belt 19, there is a method using a halftone image 47. This forms a halftone image 47 in the longitudinal direction on the photosensitive member 9, transfers it to the intermediate transfer belt 19, and uses the toner sensor 40 to detect density unevenness of the halftone image 47 with the toner sensor 40. (See FIG. 6). The controller 41 may be set so that the above-described operation of detecting the uneven resistance value of the intermediate transfer belt 19 by the toner sensor 40 is performed when the apparatus main body is turned on. Further, when the apparatus main body is left for a long time with the power on, the control unit 41 is set so that the resistance value non-uniformity detection operation of the intermediate transfer belt 19 is performed every operation of a certain number of sheets. More specifically, the number of transfer sheets passing over the intermediate transfer belt 19 is cumulatively measured by the calculation unit 45. For example, the cumulative number may be set to be performed every 1000 sheets.
[0061]
Further, as long as A3, which is the maximum sheet passing size of the apparatus, is copied, both non-sheet passing portions do not exist, and hence the resistance value unevenness of the intermediate transfer belt 19 does not occur. Therefore, the operation for detecting the uneven resistance value of the intermediate transfer belt 19 is set to be performed for every predetermined number of transfer sheets less than A3, for example, A4 size transfer sheets, for example, to be performed for every 1000 sheets. You may take a method.
[0062]
Further, the length of the transfer paper with respect to the moving direction of the surface of the intermediate transfer belt 19 is cumulatively measured by the calculation unit 45. There is also a method of setting the control unit 41 so that a signal is transmitted to the control unit 41 when the cumulative length reaches, for example, 300 (m). Thus, when the calculation unit 45 detects 300 (m), a signal is transmitted to the control unit 41, and the control unit 41 that has received the signal activates the toner sensor 40. Further, the measurement by the calculation unit 45 may be set in the control unit 41 so that the measurement is limited to transfer paper of A4 or less, for example.
[0063]
In this embodiment, four toner sensors 40 for detecting the density of the toner transferred onto the intermediate transfer belt 19 are arranged in the longitudinal direction of the intermediate transfer belt 19, and the intermediate transfer belt 19 is detected based on the detection value from the toner sensor 40. It is possible to detect the uneven resistance value in the longitudinal direction. Since the deterioration of the intermediate transfer belt 19 can be known from the resistance value unevenness, the life of the intermediate transfer belt 19 due to the deterioration can be recognized. Then, by displaying this fact on the operation unit 43, it is possible to accurately notify the user or service person. Then, the user or service person or the like replaces the intermediate transfer belt 19 to prevent the occurrence of an abnormal image.
[0064]
In the detection method using a halftone image, since the toner density on the photoconductor 9 is uniform, the density unevenness of the image on the intermediate transfer belt 19 can be detected easily and appropriately, and thereby the resistance value unevenness of the intermediate transfer belt 19 is detected. Can know.
[0065]
By setting so that the detection operation by the toner sensor 40 is performed when the power of the apparatus main body is turned on, it is possible to know the state of the intermediate transfer belt 19 before the copy operation without taking time for the detection operation. Further, by setting the detection operation to be performed for each predetermined number of transfer sheets determined in advance, it is possible to grasp without overlooking the deterioration of the intermediate transfer belt 19. Furthermore, by setting the detection operation to be performed for every predetermined number of transfer sheets less than the maximum sheet passing size, the detection operation is not performed wastefully, and the deterioration of the intermediate transfer belt 19 is determined at an appropriate time. I can grasp it. In addition, by setting the detection operation to be performed for every fixed transfer length of transfer paper of all sizes or transfer paper of a predetermined size or less, the intermediate transfer belt 19 can be detected at a more appropriate time. The degree of deterioration can be grasped.
[0066]
Next, although the modification of this invention is demonstrated, in the description, the same code | symbol is attached | subjected to the member and site | part which have the same function as the above-mentioned member and site | part, and the description is abbreviate | omitted. As shown in FIG. 6, one toner sensor 40 is provided at a position facing the transfer belt 19. The toner sensor 40 can be moved to the left and right in the longitudinal direction of the transfer belt 19 by a driving unit (not shown). By moving this one toner sensor 40 to the left and right in the longitudinal direction, it is scanned and the resistance value of each part of the intermediate transfer belt 19 is detected.
[0067]
As described above, when the toner sensor 40 is scanned, it takes time to scan and detect the toner amount. Therefore, during the normal image forming operation, the intermediate transfer belt 19 is moved. The area becomes large. Therefore, the controller 41 may be set to stop the intermediate transfer belt 19 during scanning.
[0068]
In this modified example, one toner sensor 40 can detect the uneven resistance value in the longitudinal direction of the intermediate transfer belt 19. Also, this person scans the toner sensor 40 by moving the toner sensor 40 to a necessary position at any number of positions, for example, a position corresponding to A4 length, B4 length, A5 length, A5 width, B5 length, B5 width. This is advantageous. Further, since the intermediate transfer belt 19 during scanning is stopped, the image range scanned by the toner sensor 40 is reduced, and the toner amount at the same position in the longitudinal direction can be easily detected. The control unit 41 can detect resistance value unevenness.
[0069]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, in this embodiment and the modification, a belt is used as the intermediate transfer member, but a roller or the like may be used instead of the belt. In this embodiment and the modification, a color image is used, but a monochromatic image may be used. Since the toner sensor 40 only needs to be able to measure at different positions on the intermediate transfer belt 19, the same effect can be obtained even if the toner sensor 40 is arranged in a diagonal line with respect to the longitudinal direction. Similarly, in a modified example, the toner sensor 40 may be scanned obliquely with respect to the longitudinal direction. Furthermore, the reference value of the number of sheets measured by the calculation unit 45 may be set to 2000 sheets or 3000 sheets, for example. Further, the reference value of the length measured by the calculation unit 45 may be set to 400 m or 500 m.
[0070]
【The invention's effect】
  According to the first and second aspects of the present invention, when the detection value by the detection unit satisfies a predetermined condition, the control unit limits the subsequent copy-capable documents to character images. In other words, the intermediate transfer member having a long life can be used to some extent.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a color copying machine according to an embodiment.
FIG. 2 is a detailed view of the vicinity of the photoreceptor according to FIG.
FIG. 3 is a front view illustrating a state of the intermediate transfer belt according to the present exemplary embodiment.
FIG. 4 is a perspective view illustrating an arrangement state of toner sensors according to the present exemplary embodiment.
FIG. 5 is a graph illustrating a state of the intermediate transfer belt according to the present embodiment.
FIG. 6 is a perspective view illustrating an arrangement state of toner sensors according to a modified example.
FIG. 7 is a perspective view illustrating a state of an intermediate transfer belt and transfer paper.
[Explanation of symbols]
9 Photoconductor
19 Intermediate transfer belt (intermediate transfer member)
19a Paper passage
19b Left side paper
19c Right-hand section
40 Toner sensor (detection means)
41 Control unit (control means)
43 Operation unit
45 Calculation unit
47 Halftone image

Claims (2)

A plurality of photosensitive members that carry a toner image, an intermediate transfer member that transfers the toner image on the photosensitive member, and a plurality of rollers arranged in a longitudinal direction that is perpendicular to the moving direction of the surface of the intermediate transfer member are transferred onto the intermediate transfer member. Detection means for detecting the amount of toner that has been detected, control means for comparing the detection values from the detection means, and controlling the apparatus in accordance with the values, and the control means for detecting the detection values from the detection means An image forming apparatus that detects an uneven resistance value of an intermediate transfer member,
The image forming apparatus according to claim 1, wherein the control unit limits a copyable document to a character image document based on a detection value from the detection unit. A photosensitive member carrying a toner image, an intermediate transfer member for transferring the toner image on the photosensitive member, and movable on the intermediate transfer member. By moving, the amount of toner at a plurality of locations on the surface of the intermediate transfer member is detected. A detection unit, a control unit that compares the detection value by the detection unit, and controls the apparatus according to the value, and a detection value from the detection unit is detected as uneven resistance value of the intermediate transfer member. An image forming apparatus that
The image forming apparatus according to claim 1, wherein the control unit limits a copyable document to a character image document based on a detection value from the detection unit.

Images