JP2005181974A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain stable images by simply and precisely grasping whether a transfer member is replaced in an image forming apparatus, having a transfer member such as an intermediate transfer member or a carrying transfer member. <P>SOLUTION: The toner patterns, formed at photoreceptor drums 21a to 24a, are transferred to recording media directly or indirectly by the transfer member 12. A concentration sensor 16 detects the surface state of the transfer member and outputs the detected signals. In a decision control part 45, there are set a first voltage value indicating the lower limit of level values of the detected signals and a second voltage value obtained by the relationship between the number of sheets used at the transfer member and the detected signals. The decision control part decides whether the transfer member has been replaced, on the basis of the detected signals and the first and second voltage values. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and in particular, after a toner image formed on an image carrier such as a photosensitive drum is transferred to an intermediate transfer body, the toner on the intermediate transfer body An image forming apparatus using an intermediate transfer body that forms an image by transferring an image to a recording medium such as recording paper, or a recording in which a toner image formed on an image carrier such as a photosensitive drum is conveyed by a conveying transfer body The present invention relates to an image forming apparatus having a transfer transfer body that directly transfers to a recording medium such as a sheet to form an image.

  In general, as a full-color image forming apparatus using an electrophotographic process, a so-called tandem type color image forming in which a plurality of image forming units are arranged along the conveying direction (moving direction) of an intermediate transfer belt, which is one of intermediate transfer bodies. The device is known. In a color image forming apparatus, a toner image for each color is sequentially superimposed and transferred on an intermediate transfer belt in an image forming unit to form a color toner image (primary transfer), and then a color toner image is formed at a secondary transfer position. The image is transferred to recording paper. In this type of image forming apparatus, in order to ensure image stability, for example, the density of an image transferred onto the intermediate transfer belt is detected by a density (ID) sensor when the power is turned on and every predetermined number of prints. The image density correction including various correction controls such as correction of the developing bias voltage is performed so that an appropriate image density is obtained according to the detection result. Also, registration correction for correcting the positional deviation of each color is performed using the same density sensor at the timing before and after the image density correction.

  By the way, in the primary transfer, the transferability differs depending on the setting conditions and transfer status of the primary transfer roller, and the difference in transferability greatly affects the above-described correction control. In other words, when image formation is performed, titanium oxide, silica, paper dust, and the like, which are toner components, adhere to the intermediate transfer belt, thereby deteriorating the surface of the intermediate transfer belt and changing transferability. In addition, the transfer property changes depending on the pressure applied to the primary transfer roller, and the higher the pressure applied to the primary transfer roller, the better the transfer property. On the other hand, when the pressure is increased, color misregistration occurs. From this point, it is not preferable to increase the pressure.

  Under such circumstances, when the intermediate transfer belt deteriorates due to aging, the transferability changes, and the image for correction is not transferred well to the intermediate transfer member when the image density is corrected. The development bias and the exposure output are set to correct the image density. In order to prevent such a situation, the primary transfer condition is changed so that the image for correction is transferred satisfactorily. However, there is a limit to the range in which the primary transfer condition can be corrected. As the transfer belt deteriorates, the image density correction does not work well, and it becomes difficult to form a high-quality image. In order to avoid such a situation, the life of the intermediate transfer belt is detected and the replacement thereof is promoted.

  For example, a mark is attached on the intermediate transfer belt, this mark is detected by a density detection sensor, and after the mark is detected by the density detection sensor, the use state of the intermediate transfer belt is detected. Here, whether the intermediate transfer belt is new or old is determined based on the presence or absence of a mark. And when there is no mark, only the surface property data is detected, the surface property data stored in the memory in advance and the newly detected surface property data are compared, and it is determined whether there is a difference, If there is no difference, it is determined that they are the same unit (intermediate transfer belt). (See Patent Document 1).

  On the other hand, when an intermediate transfer unit such as an intermediate transfer belt is replaced, in order to set optimal image forming conditions, a memory storing assembly conditions of the intermediate transfer unit is provided on the stay of the intermediate transfer unit. The assembly condition information of the intermediate transfer body unit stored in the memory is taken into the control device on the apparatus main body side, the image formation conditions are changed, and the optimum image formation conditions of the replaced intermediate transfer body unit are set. Here, the operation time and the number of operations of the intermediate transfer body unit are stored in the memory, and the controller transfers the information on the operation time and the number of operations of the intermediate transfer body unit stored in the memory to perform the intermediate transfer. The life of the body unit is also detected (see Patent Document 2).

JP 2002-351269 A (paragraph (0028) to paragraph (0044), FIGS. 3 and 5) JP 11-344875 A (paragraph (0039) to paragraph (0046), FIGS. 2 to 3)

  However, in the image forming apparatus described in Patent Document 1, a mark is attached to the intermediate transfer belt, and the use state of the intermediate transfer belt is detected according to the result of detection of the mark by the density detection sensor. However, it is extremely difficult to determine whether the intermediate transfer belt has reached the end of its life based on the result of simply detecting the mark with the density detection sensor. In particular, the printing conditions such as the image pattern and the transfer conditions, the toner component, The degree of deterioration of the intermediate transfer belt varies greatly depending on the recording paper and the material (material) of the intermediate transfer belt, and it is difficult to accurately grasp the deterioration state of the intermediate transfer belt simply by using the result of detecting the mark density. It is.

  Further, in Patent Document 1, when the intermediate transfer member is replaced, the toner mark developed on the intermediate transfer member at the time of shipment is measured by a density sensor to determine whether the intermediate transfer member is new. The production process requires not only a process for developing the toner mark on the intermediate transfer member, but also the packaging of the intermediate transfer member without disturbing the toner mark, resulting in an increase in production cost.

  On the other hand, in the image forming apparatus described in Patent Document 2, the operation time and the number of operations of the intermediate transfer body unit are stored in the memory provided on the intermediate transfer body unit side, and the main body side control device is stored in the memory. Although the operation time and operation frequency information (that is, usage history) of the intermediate transfer unit is taken in to detect the life of the intermediate transfer unit, the memory element is generally expensive, and the intermediate transfer unit and the main body side control device are in the middle. There is a problem that the memory provided on the transfer unit side has to be wired, which not only increases the cost but also complicates the configuration of the image forming apparatus due to the wiring.

  In any case, in the conventional image forming apparatus, it is difficult to accurately grasp the deterioration state of the intermediate transfer member such as the intermediate transfer belt with an inexpensive and simple configuration. Therefore, it is possible to always obtain a stable image. There is a problem that it is difficult. Such a problem also occurs in an image forming apparatus that forms an image by directly transferring a toner image formed on a photosensitive drum onto a recording sheet conveyed by a conveyance transfer body without using an intermediate transfer body. (Intermediate transfer member and transport transfer member are collectively referred to as transfer member).

  Therefore, in view of the problems of the prior art, the present invention easily and accurately grasps whether or not the intermediate transfer member or the transfer transfer member has been replaced, and provides a stable image that is not inferior to that before replacement. An object of the present invention is to provide an image forming apparatus that can be obtained.

  Accordingly, in order to solve such problems, the present invention provides a transfer body that directly or indirectly transfers a toner image formed on an image carrier to a recording medium, and a toner image transferred to the recording medium. And a first voltage value indicating a lower limit value of the level value of the detection signal in the image forming apparatus having a fixing device for fixing to the image sensor. And a second voltage value obtained from the relationship between the number of used transfer members and the detection signal is set, and the transfer member is determined based on the detection signal and the first and second voltage values. And determining means for determining whether or not the battery has been exchanged. In the present invention, when it is determined by the determination means that the transfer body has been replaced, when the transfer condition before replacing the transfer body is different from the transfer condition in the initial use of the transfer body, the transfer condition is set. Control means for changing the transfer conditions to the initial transfer conditions of the transfer body and correcting the image density is provided.

  In the present invention, the image forming apparatus includes a fixing temperature sensor that detects a temperature of a fixing roller of the fixing device, and the determination unit is turned on when the fixing temperature detected by the fixing temperature sensor is lower than a predetermined temperature when the power is turned on. It is determined whether or not the transfer member has been replaced. Further, the determination unit replaces the transfer member when the fixing temperature is equal to or higher than the predetermined temperature and satisfies a predetermined condition. It may be determined whether or not it has been done.

  In the present invention, when the level value of the detection signal is greater than or equal to the first voltage value and less than the second voltage value, the determination means determines the level value of the current detection signal and the previous detection signal. Compared to the level value, if the deviation is equal to or greater than a predetermined voltage value, it is determined that the transfer body has been replaced. Therefore, when the number of printed sheets increases, the transfer body replacement time determination is made. There is an effect that can be performed accurately.

  Furthermore, in the present invention, the determination means is configured such that when the level value of the detection signal is equal to or greater than the first voltage value, the cumulative value of the number of printed sheets printed using the transfer body is equal to or greater than a predetermined cumulative threshold. When the accumulated value is less than the accumulated threshold and the level value of the detection signal is less than the second voltage value, the current detection signal level value and the previous detection are determined. The level value of the signal may be compared, and if the deviation is equal to or greater than a predetermined voltage value, it may be determined that the transfer body has been replaced. Is equal to or greater than the first voltage value, it is determined whether the cumulative value of the number of printed sheets printed using the transfer body is equal to or greater than a predetermined cumulative threshold, and the cumulative value is equal to or greater than the cumulative threshold. The third voltage value lower than the second voltage value is used. When the level value of the detection signal is less than the third voltage value, the level value of the current detection signal is compared with the level value of the previous detection signal, and the deviation is equal to or greater than a predetermined voltage value. If so, it may be determined that the transfer body has been replaced.

  In the present invention, the predetermined voltage value is set according to a level value of the detection signal at the initial use of the transfer body and a level value of the detection signal when the transfer body has reached the end of its life. . The second voltage value is varied according to the set life for each transfer body. The transfer body is preferably driven and controlled along a predetermined direction, and the detection of the surface state of the transfer body by the detection sensor is performed along the predetermined direction. At this time, the determination unit uses an average value obtained by averaging the detection results obtained by the detection sensor over a predetermined period as the detection signal. The transfer body may be, for example, an intermediate transfer body that transfers the toner image to the recording medium after the toner image formed on the image carrier is transferred, or the image carrier while transporting the recording medium. It is a conveyance transfer body that directly transfers the formed toner image to the recording medium.

  As described above, the image forming apparatus of the present invention detects the surface state of the transfer body to obtain a detection signal, and whether or not the transfer body has been replaced based on the detection signal and the first and second voltage values. In other words, since it is determined whether or not the transfer body has been replaced using the two discriminant values of the first and second voltage values, the transfer can be easily performed with an inexpensive method. Since the deterioration state of the body can be accurately grasped, and it is determined that the transfer body has been replaced, the transfer condition is changed to the initial use state of the transfer body and the image density correction is performed. There is an effect that it is possible to obtain a stable image that is not inferior to that before the transfer body replacement.

  In the present invention, when the level value of the detection signal is equal to or higher than the first voltage value and lower than the second voltage value, the level value of the current detection signal is compared with the level value of the previous detection signal, If the deviation is equal to or greater than a predetermined voltage value, it is determined that the transfer body has been replaced, so that the deterioration state of the transfer body can be accurately and accurately grasped, and the transfer body has been replaced. When the determination is made, the transfer condition is changed to the initial use state of the transfer body and the image density correction is performed, so that it is possible to obtain a stable image comparable to that before the transfer body replacement. is there.

  In the present invention, when the cumulative value of the number of printed sheets using the transfer body is equal to or greater than a predetermined cumulative threshold, the level value of the detection signal is set to the first voltage value using the third voltage value lower than the second voltage value. When the voltage value is less than 3, the current detection signal level value is compared with the previous detection signal level value, and if the deviation is equal to or greater than a predetermined voltage value, the transfer body is replaced. You may make it determine that it was.

  Further, in the present invention, the above-mentioned predetermined voltage value is set according to the level value of the detection signal at the initial use of the transfer body and the level value of the detection signal when the transfer body reaches the end of its life. In addition, since the second voltage value is made variable according to the set life for each transfer body, differences among individual image forming apparatuses such as initial variations of the transfer body and sensitivity variations among individual density sensors are taken into account. As a result, for example, the average second voltage value is used at the beginning of the set life of the transfer body, and at a time when the transfer body is expected to be likely to be replaced, If the second voltage value is changed to a value that takes into account variations in the image forming apparatus, it can be detected more accurately whether or not the transfer member has been replaced. For this reason, it is possible to accurately grasp the deterioration state of the transfer body and change the transfer condition to the initial use state of the transfer body and perform image density correction when it is determined that the transfer body has been replaced. As a result, there is an effect that it is possible to obtain a stable image that is not inferior to that before replacement of the transfer body.

  In the present invention, since the surface state of the transfer body is detected along the drive direction of the transfer body, the influence of local surface state variations such as scratches generated on the transfer body is reduced, and the surface state As a result, the replacement time of the transfer member can be appropriately determined.

  Hereinafter, exemplary embodiments of the present invention will be described in detail 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 unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a sectional view schematically showing an example of a tandem color printer used as an image forming apparatus. In the illustrated printer 11, for example, color information of document image data sent from an external computer (not shown). Depending on the selection, either full-color image output or monochrome image output is selected. An intermediate transfer belt 12 as an intermediate transfer member is disposed in a housing (housing: not shown) of the printer 11, and the intermediate transfer belt 12 is stretched around a driving roller 13, a driven roller 14, and a backup roller 15. The drive roller 13 is driven to rotate in the direction indicated by the solid line arrow.

  The surface of the intermediate transfer belt 12 changes from the initial state as it is used due to adhesion of components contained in the toner and friction with the recording paper, etc. (the light on the surface of the intermediate transfer belt is irradiated due to secular change). The amount of light reflected from the surface changes (decreases).

  Four image forming units 21 to 24 are sequentially arranged along the intermediate transfer belt 12 from the upstream side in the conveyance direction of the intermediate transfer belt 12, and in the illustrated example, the magenta (M) image forming unit 21 is sequentially arranged from the upstream side. , Cyan (C) image forming unit 22, yellow (Y) image forming unit 23, and black (B) image forming unit 24 are arranged along intermediate transfer belt 12 (in FIG. 1). Only the photosensitive drums (image carriers) 21a to 24a included in the image forming units 21 to 24 are shown).

  When performing image formation, the surfaces of the photosensitive drums 21a to 24a are uniformly charged. When document image data is input from an external computer, the photosensitive drums 21a to 24a are exposed according to the document image data. Thus, an electrostatic latent image is formed. Then, the electrostatic latent image is developed by a developing device (not shown), and an M toner image, a C toner image, a Y toner image, and a B toner image are formed on the photosensitive drums 21a to 24a, respectively.

  The primary transfer rollers 31a to 34a are opposed to the photosensitive drums 21a to 24a with the intermediate transfer belt 12 interposed therebetween, and the respective color toner images on the photosensitive drums 21a to 24a are intermediated by the primary transfer rollers 31a to 34a. A color toner image is formed on the intermediate transfer belt 12 by being sequentially transferred to the transfer belt 12. A density (ID) sensor (for example, Stanley Electric Co., Ltd., product number: KUA0003P) 16 that is also used as a detection sensor is disposed facing the drive roller 13 on the downstream side of the photosensitive drum 24a. The ID sensor 16 detects the image density of the image density correction toner image formed on the intermediate transfer belt 12 or the positional information of the registration correction toner image for correcting the color misregistration of each color as necessary.

  In a situation where image formation is not performed, a correction mode (an image density correction mode and a registration correction mode, which will be described later), these correction modes are performed continuously. The surface state of the intermediate transfer belt 12 has an effect. Since this is mainly the image density correction mode, the density sensor 16 will measure the toner image density of each color formed on the surface of the intermediate transfer belt 12 when the image density correction mode is described. When titanium oxide (white) or the like contained in the toner adheres to the intermediate transfer belt 12 (for example, light brown) and the color of the intermediate transfer belt 12 changes (that is, a uniform surface state becomes a rough surface state). When the color becomes cloudy), the output from the density sensor 16 decreases (the output voltage that is the detection signal decreases). When the image density is low, the image is affected by reflection from the surface of the intermediate transfer belt 12. Therefore, when correcting the image density, the surface state of the intermediate transfer belt 12 is detected to indicate the surface state. The detection signal is used for image density correction and stored in a printer memory (not shown). In this embodiment, a detection signal indicating the surface state of the intermediate transfer belt 12 is used to determine whether or not the intermediate transfer belt 12 has been replaced during image density correction.

For example, the intermediate transfer belt 12 has a conductive chloroprene rubber (an elastic layer, for example, a thickness of 500 μm) on a PVDF base (for example, a thickness of 100 μm, a volume resistivity of 10 ¹⁰ Ω · cm) as a reinforcing layer. Volume specific resistance 10 ^10.5 Ω · cm) is formed, and conductive silicon rubber and PTFE are formed on this elastic layer as a surface layer (for example, thickness 15 μm, volume specific resistance 10 ¹² Ω · cm). It has been done.

  A recording sheet (hereinafter simply referred to as a sheet) is conveyed from a sheet feeding device (not shown) to a registration roller pair 41 via a sheet conveyance path (not shown), and a registration disposed on the upstream side of the registration roller pair 41. When the sheet is detected by the sensor 42, the registration roller pair 41 is driven in synchronization with the toner image formed on the rotating intermediate transfer belt 12, and the sheet is conveyed to the secondary transfer position. A secondary transfer roller 43 is disposed at the secondary transfer position, and the secondary transfer roller 43 faces the backup roller 15 with the intermediate transfer belt 12 interposed therebetween. After the toner image on the intermediate transfer belt 12 is transferred to the paper at the secondary transfer position (secondary transfer), the paper is sent to a fixing device 44 including a heating roller (fixing roller) 44a and a pressure roller 44b. Here, the toner image on the sheet is fixed on the sheet, and the sheet is discharged to a discharge tray (not shown).

  After the secondary transfer, the intermediate transfer belt 12 is cleaned by the cleaning unit 14a. On the other hand, the toner remaining on the photosensitive drums 21a to 24a is removed by a cleaning device having a cleaning blade or the like (not shown). The charged charges remaining on the surfaces 21a to 24a are neutralized by a neutralizer (not shown). Further, a temperature sensor 47 is disposed in the vicinity of the fixing roller 44 a, and the detected temperature detected by the temperature sensor 47 is given to the determination control unit 45.

  As shown in FIG. 1, the ID sensor 16 is connected to a determination control unit 45, and the determination control unit (for example, the determination control unit is a control device that controls the image forming apparatus) 45, as will be described later. If it is determined whether the intermediate transfer belt 12 has reached the end of its life in accordance with the density signal obtained from the ID sensor 16, and it is determined that the intermediate transfer belt 12 has reached the end of its life, the display unit (this display unit is For example, this is displayed on 46) which is a display arranged on an operation panel provided in the image forming apparatus.

  Here, referring to FIG. 2, the relationship between the detection signal (output voltage) and the number of printed sheets when the surface state of the intermediate transfer belt 12 output from the density sensor 16 in the image forming apparatus is detected. The reference line A shown in FIG. 2 was obtained. That is, the output voltage (V) decreases as the number of printed sheets increases. When determining the reference line A, the relationship between the number of printed sheets and the output voltage was measured for a plurality of image forming apparatuses in consideration of variations among the image forming apparatuses to determine the reference line A (reference When the line A was obtained, the measured value (output voltage) in which the output voltage was greatly lowered to the lower side was excluded).

  Then, in order to absorb the variation of the measured value located above the reference line A, a parallel line segment is drawn along the reference line A, and this is divided into a determination line B (second determination line (second voltage value). (That is, the discriminant line B is a function indicating the relationship between the output voltage and the progress of deterioration due to durable use of the surface of the intermediate transfer belt 12). This discriminant line B indicates that the output voltage of the density sensor 16 is V1 when the number of prints on the intermediate transfer belt 12 is D. From the result of this experiment, in the illustrated printer, V1 = −9.58 × 10−. It is represented by 6 × D + 3.75.

  For example, the difference (indicated by X in FIG. 2) between the output voltage when the initial intermediate transfer belt 12 (for example, a new intermediate transfer belt) is used and the output voltage when the intermediate transfer belt 12 reaches the end of its life. A shift amount (indicated by Y in FIG. 2, where Y = about 3/8 × X. Actually, the shift is 0.7 V plus) is set to 1/2 to 1/10. The reference line A is translated upward by the shift amount to obtain the discrimination line B. Further, in consideration of variations among the image forming apparatuses with reference to the output voltage of the initial intermediate transfer belt 12, a determination line C (first determination line (first voltage value)) parallel to the horizontal axis is obtained. This discrimination line C was set as a lower limit value (lower limit threshold value) when the intermediate transfer belt 12 was determined to be replaced. The determination line C (voltage value) is determined in consideration of variations in the output voltage of the density sensor 16 in the initial intermediate transfer belt 12.

  Here, referring to FIGS. 1 to 3, when the main power switch (not shown) of the printer is turned on (MSW ON: step S1), the image density correction mode is turned off in the determination control unit 45. It is determined whether or not (step S2). When the image density correction mode is off (Calibration Off Mode), the determination control unit 45 displays on the display unit 46 that the intermediate transfer belt 12 (image unit) is not replaced (step S3). On the other hand, if the image density correction mode is not OFF, the determination control unit 45 checks the fixing temperature detected by the temperature sensor 47 (step S4), and if the fixing temperature is less than 80 ° C., the image density correction ( (Calibration) is executed (Calibration execution: step S5). When the number of printed sheets reaches a predetermined number, an image density correction command (calibration command) is automatically interrupted (step S6), and image density correction is executed.

  In step S4, if the fixing temperature is 80 ° C. or higher, the determination control unit 45 displays whether or not manual image density correction is performed on the display unit 46 (manual calibration: step S7). When an instruction to perform manual image density correction is input from the operation panel, the process proceeds to step S5. On the other hand, if no manual image density correction instruction is given, no image unit replacement is displayed in step S3. If the fixing temperature is less than 80 ° C., it is determined that the time for performing the image density correction is sufficient, and the image density correction is executed. Even if the fixing temperature is 80 ° C. or higher, As described above, image density correction may be performed manually.

  When the image density correction mode is executed, the determination control unit 45 determines whether the output voltage of the ID sensor 16 that has read the reflection from the surface of the intermediate transfer belt 12 is equal to or higher than the voltage value indicated by the determination line C. (First determination: step S8). When the output voltage is less than the voltage value indicated by the discrimination line C, the above-described step S3 is executed. On the other hand, if the output voltage is greater than or equal to the voltage value indicated by the discrimination line C, whether or not the output voltage is greater than or equal to the voltage value indicated by the discrimination line B (calculated according to the number of used intermediate transfer belts 12). (Second determination: step S9).

  In step S9, if the output voltage is not less than the voltage value indicated by the discrimination line B, that is, if the output voltage is not less than the voltage value indicated by the discrimination line C and not less than the voltage value indicated by the discrimination line B, the image It is determined that the unit has been replaced, and the number of printed sheets on the intermediate transfer belt 12 so far is reset (image unit count reset: step S10). If it is determined that the intermediate transfer belt 12 has been replaced, the determination control unit 45 resets the primary transfer voltage (current) to the voltage when the intermediate transfer belt 12 is new. Otherwise, the primary transfer voltage (current) is increased according to the deterioration of the intermediate transfer member, and therefore the primary transfer voltage (current) may be too high for the intermediate transfer belt 12 in the initial state. This is because if it is too high, the transfer efficiency may be lowered, resulting in problems such as missing images. The same applies to the secondary transfer voltage (current). Since the image density changes when the primary transfer voltage (current) changes, the image density correction is executed again.

  On the other hand, if the output voltage is less than the discrimination line B, the output voltage at the previous execution of image density correction (this value is held in the judgment control unit 45) is compared with the current output voltage (third). In step S11), if the deviation is equal to or greater than 1/10 to 1/2 × X = Z (here, 3 / 8X, that is, Z = 0.7 V in consideration of variation), intermediate transfer is performed. It is determined that the belt 12 has been replaced, and step S10 is executed. If the deviation is less than 1/10 to 1/2 × X = Z, it is determined that the intermediate transfer belt 12 has not been replaced and step S3 is executed. Is done. Here, as described above, X is the difference between the output voltage when the new intermediate transfer belt 12 is used and the output voltage when the intermediate transfer belt 12 reaches the end of its life. The image unit count reset is also executed when a counter reset command is input (step S12).

  The above-described discrimination line B is obtained based on the number of printed sheets, but may be obtained according to the driving time of the intermediate transfer belt 12 or the number of image formations, for example. When the deviation between the previous output voltage and the current (current) output voltage is 1/10 to 1/2 × X or more, it is determined that the image unit has been replaced, and the number of prints is reset. Specifically, if this deviation is 0.7 V or more, it is determined that the image unit has been replaced, and the number of printed sheets is reset.

  1 and FIG. 4 and FIG. 5, in general, in the initial use of the intermediate transfer belt 12, the transition of the output voltage of the density sensor 16 as a result of detecting the surface state of the intermediate transfer belt 12 Is unstable with respect to the increase in the number of image formations, but as the image formation (printing) is performed (in the example shown in FIGS. 4 and 5, after printing about 20,000 sheets), the transition of the output voltage of the density sensor 16 changes. The change in the output voltage of the density sensor 16 can be approximated by a straight line with respect to the increase in the number of printed sheets.

  In the example shown in FIGS. 4 and 5, the output voltage of the density sensor 16 from when 50,000 sheets have been printed to when 50,000 sheets have been printed when the number of printed sheets has elapsed from the initial use of the intermediate transfer belt 12. An approximate straight line represented by a linear equation is calculated from the reference line A2 as a new reference line A2, and a discrimination line B2 shifted from the reference line A2 by Y2 (0.3V) shown in FIGS. 4 and 5 in the positive direction is set. . The reason why the shift amount Y2 of the discrimination line B2 with respect to the reference line A2 is 0.3 V, which is smaller than Y described in the first embodiment, is that it is only necessary to consider the variation in the output voltage of the density sensor 16 in each image forming apparatus. It is.

  In the initial use of the intermediate transfer belt 12, components such as toner on the surface of the intermediate transfer belt 12 are locally attached, and wear due to contact with the recording paper also occurs locally. Although the output voltage of the sensor 16 varies, as the image formation (printing) is repeated, the entire surface of the intermediate transfer belt 12 gradually becomes uniform, and the output voltage of the density sensor 16 is stabilized.

  Here, with reference to FIG. 1 and FIG. 6, a procedure for determining whether or not the intermediate transfer belt 12 has been exchanged will be described. Now, when a main power switch (not shown) of the printer is turned on (MSW ON: Step T1), the determination control unit 45 determines whether or not the temperature of the fixing roller 44a is 80 ° C. or more (fixing temperature). Confirmation: Step T2). If the temperature of the fixing roller is less than 80 ° C., the determination control unit 45 performs a correction operation including image density correction described later (step T3).

  In step T2, if the temperature of the fixing roller 44a detected by the temperature sensor 47 is 80 ° C. or higher, the determination control unit 45 determines whether or not a predetermined condition is satisfied (satisfying the predetermined condition: step T4). . Here, the predetermined condition is, for example, whether or not a predetermined number (for example, 1000) of image formation has been performed since the previous image density correction, or whether or not the intermediate transfer belt 12 has been attached to or detached from the apparatus main body immediately before. Show. For example, if the image forming apparatus is installed in a store that is open 24 hours, the temperature of the fixing roller is always 80 ° C. or higher, and in this case, an intermediate transfer belt using image density correction and image density correction is used. Step 12 is provided because it becomes impossible to determine whether or not 12 is exchanged. The determination in step T4 may be performed for each continuous image forming job so as not to interrupt the continuous image forming job.

  In step T4, if the predetermined condition is not satisfied, the determination control unit 45 determines whether there is an image formation command (step T5), and if there is an image formation command, executes image formation (step T6). Return to. If there is no image formation command, the determination control unit 45 returns to step T2 without performing image formation. On the other hand, if the predetermined condition is satisfied in step T4, the discrimination control unit 45 proceeds to step T3.

  When step T3 is performed, the determination control unit 45 reads a detection signal (output voltage) indicating the surface state of the intermediate transfer belt 12 output from the density sensor 16 (step T7). Here, when detecting the surface state of the intermediate transfer belt 12, an intermediate portion of a specified length (for example, 10 cm) is used in order to avoid the influence of scratches on the surface of the intermediate transfer belt 12 and local density unevenness. It is desirable that the surface state of the transfer belt 12 is sequentially detected, and the determination control unit 45 uses the average value of the detection signals.

  Further, an image density correction toner image is formed on the intermediate transfer belt 12 as described above at the same position where the surface state is detected, and the image density obtained by detecting the image density correction toner image is obtained. If correction is performed using the detection result (average value) indicating the surface state, high-precision image density correction can be performed. In other words, since the surface state of the intermediate transfer belt 12 is not uniform over the entire circumference, if the average value is used as described above, the variation is offset and the image density correction can be performed with high accuracy. Will be able to.

  Subsequently, the determination control unit 45 determines whether or not the output voltage value of the concentration sensor 16 is equal to or higher than the voltage value indicated by the determination line C (see FIG. 2) (first determination: step T8). If the output voltage value is less than the voltage value indicated by the determination line C, it is determined whether or not the output voltage value of the concentration sensor 16 is less than 1.1 V (fifth determination: step T9). If the output voltage value is less than a predetermined specified voltage value (for example, 1.1 V), the determination control unit 45 determines that the intermediate transfer belt 12 needs to be replaced, and gives an instruction to replace the intermediate transfer belt 12. A message is displayed on the display unit 46 (exchange instruction: step T10).

  On the other hand, if the output voltage is 1.1 V or more, the determination control unit 45 determines that the intermediate transfer belt 12 is not exchanged and that the intermediate transfer belt 12 is not exchanged (step T11). Image density correction is executed (step T12). Further, although not shown, registration correction is performed as necessary, and the determination control unit 45 proceeds to Step T5.

  In step T8, if the output voltage value (average value) of the density sensor 16 is equal to or higher than the voltage value indicated by the determination line C, the determination control unit 45 starts using the intermediate transfer belt 12 currently in use. It is determined whether or not the number of formed images has reached a specified number (for example, 50,000) (fourth determination: step T13). The specified number can be changed according to the material of the intermediate transfer belt 12 or the degree of deterioration of the intermediate transfer belt 12.

  The relationship between the number of images formed and the output voltage value of the density sensor 16 as a result of detecting the surface state of the intermediate transfer belt 12 is as described above over a predetermined number (for example, 30,000). If the ratio of the output voltage value that falls within ± 0.3 V according to the linear function obtained from the calculated result is equal to or higher than a specified ratio (for example, 90%), the third determination (step T18) is performed at that time. You may do it.

  If it is determined in step T13 that the number of formed images is less than 50,000, the determination control unit 45 outputs the voltage value indicated by the determination line B (a value calculated according to the number of used intermediate transfer belts 12). ) It is determined whether or not (second determination: step T14). In step T14, the output voltage value is equal to or greater than the voltage value indicated by the discrimination line B, that is, the output voltage value is equal to or greater than the voltage value indicated by the discrimination line C and is equal to or greater than the voltage value indicated by the discrimination line B. The determination control unit 45 determines that the intermediate transfer belt 12 has been replaced (transfer belt is replaced: step T15), interrupts the counter reset command step T16, and resets the counter. In other words, the counter that has counted the number of images formed using the intermediate transfer belt 12 is reset (transfer belt counter reset: step T17).

  When it is determined that the intermediate transfer belt 12 has been replaced, the determination control unit 45 proceeds to step T12 after resetting the primary transfer voltage to a voltage when the intermediate transfer belt 12 is new. Also at this time, registration correction is performed as necessary.

  On the other hand, if the output voltage value is less than the determination line B in step T14, the determination control unit 45 outputs the output voltage value at the previous execution of image density correction (this output voltage value is held in the determination control unit 45). And the current output voltage are compared to determine whether or not the deviation P is greater than or equal to the specified deviation threshold Z (third determination: step T18). If the deviation P is equal to or greater than 1/10 to 1/2 × X = Z (here, Z = 3 / 8X, that is, Z = 0.7 V in consideration of variation), the determination control unit 45 performs step. At T15, it is determined that the intermediate transfer belt 12 has been replaced, and the routine goes to Step T17.

  In this case as well, after the primary transfer voltage is reset to the voltage when the intermediate transfer belt 12 is new, the process proceeds to step T12. If the deviation P is less than the deviation threshold Z in step T18, the determination control unit 45 determines in step T11 that the intermediate transfer belt 12 has not been replaced, and the process proceeds to step T12. Here, as described above, X is the difference between the output voltage value when the new intermediate transfer belt 12 is used and the output voltage value when the intermediate transfer belt 12 reaches the end of its life.

  If it is determined in step T13 that the number of formed images (cumulative number) is equal to or greater than a cumulative number threshold (for example, 50,000 sheets), the discriminant line is used instead of the discriminant line B by the method described in FIGS. B2 is obtained (calculation of the discrimination line B2: step T19), and using this discrimination line B2, whether or not the output voltage value of the concentration sensor 16 is equal to or higher than the voltage value (third voltage value) indicated by the discrimination line B2. (Sixth determination: step T20). In step T20, it is determined that the output voltage is not less than the voltage value indicated by the discrimination line B2, that is, the output voltage is not less than the voltage value indicated by the discrimination line C and not less than the voltage value indicated by the discrimination line B2. The controller 45 determines in step T15 that the intermediate transfer belt 12 has been replaced, and proceeds to step T17.

  When it is determined that the intermediate transfer belt 12 has been replaced, step T12 is performed after the primary transfer voltage is reset to the voltage when the intermediate transfer belt 12 is new. On the other hand, in step T20, if the output voltage is less than the determination line B2, the determination control unit 45 proceeds to step T18 and executes the process as described above.

  By the way, the above-described discrimination line B2 is obtained based on the number of printed sheets. However, for example, it may be obtained according to the driving time of the intermediate transfer belt 12 or the number of image formations. When the deviation between the previous output voltage and the current (current) output voltage is 1/10 to 1/2 × X or more, it is determined that the intermediate transfer belt 12 has been replaced, and the number of prints is reset. Specifically, if the deviation P is 0.7 V or more, it is determined that the intermediate transfer belt 12 has been replaced, and the number of printed sheets is reset.

  In the first and second embodiments described above, whether or not the intermediate transfer member of the type in which the sheet-like intermediate transfer member is covered with the intermediate transfer belt of the type that carries and conveys the sheet or the sheet-like intermediate transfer member is replaced is determined. Can also be used.

  Further, in the first and second embodiments, the printer having the intermediate transfer body belt as the intermediate transfer body has been described. However, as described above, the surface of the intermediate transfer belt adheres to the components contained in the toner and the recording paper. It changes from the initial state with use due to friction and the like. On the other hand, even in a printer in which a toner image formed on a photosensitive drum is directly transferred onto a recording sheet conveyed by a conveyance transfer body (for example, a conveyance transfer belt), the conveyance transfer belt is not as large as an intermediate transfer belt. However, the same is true in that the component contained in the toner adheres and friction with the recording paper occurs. In a tandem printer in which recording paper is carried and conveyed mainly by electrostatic force, paper dust and recording paper are received because of receiving a transfer electric field for transferring the toner image to the recording paper at four locations. These components tend to adhere more than the intermediate transfer belt. For this reason, since the surface state of the transport transfer belt changes from the initial state is the same as that of the intermediate transfer belt, Embodiments 1 and 2 can also be applied to the transport transfer body. In the first and second embodiments, the determination control unit 45 functions as a determination unit and a control unit.

  As a result of determining whether or not the intermediate transfer member or the conveyance transfer member has been replaced using a plurality of determination lines (first and second voltage values), the deterioration state of the intermediate transfer member or the conveyance transfer member can be accurately determined. Therefore, it can be applied to the determination of the replacement timing of the intermediate transfer member or the transfer member in various copying machines, printers, facsimile machines, and the like.

1 is a diagram schematically showing a printer as an example of an image forming apparatus according to the present invention. It is a figure which shows the 1st and 2nd discrimination line used with the image forming apparatus by this invention. 6 is a flowchart illustrating an operation when determining whether or not the intermediate transfer belt has been replaced in the first exemplary embodiment of the image forming apparatus according to the present invention. It is a figure for demonstrating an example of the operation | movement at the time of changing a 2nd discriminant line after performing image formation of a prescribed number of sheets. It is a figure for demonstrating an example of the operation | movement at the time of changing a 2nd discriminant line after performing image formation of a prescribed number of sheets. 10 is a flowchart illustrating an operation when determining whether or not the intermediate transfer belt has been replaced in the second embodiment of the image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Printer 12 Intermediate transfer belt 13 Drive roller 14 Driven roller 15 Backup roller 16 Density (ID) sensors 21-24 Image forming units 21a-24a Photosensitive drums 31a-34a Primary transfer roller 41 Registration roller pair 42 Registration sensor 43 Secondary Transfer roller 44 Fixing device 45 Determination control unit 46 Display unit 47 Temperature sensor

Claims (12)

An image forming apparatus comprising: a transfer body that directly or indirectly transfers a toner image formed on an image carrier to a recording medium; and a fixing device that fixes the toner image transferred to the recording medium to the recording medium. In
A detection sensor that detects a surface state of the transfer body and outputs a detection signal;
A first voltage value indicating a lower limit value of the level value of the detection signal and a second voltage value obtained from the relationship between the number of used transfer members and the detection signal are set, and the detection signal and the first voltage value are set. An image forming apparatus comprising: determination means for determining whether or not the transfer member has been replaced based on the first voltage value and the second voltage value.   When it is determined by the determination means that the transfer body has been replaced, when the transfer condition before replacing the transfer body is different from the transfer condition at the initial use of the transfer body, the transfer condition is changed to the initial use of the transfer body. The image forming apparatus according to claim 1, further comprising a control unit that changes to the transfer condition and performs image density correction. A fixing temperature sensor for detecting the temperature of the fixing roller of the fixing device;
The determination unit is configured to determine whether or not the transfer member has been replaced when the fixing temperature detected by the fixing temperature sensor is lower than a predetermined temperature when the power is turned on. The image forming apparatus according to claim 1.   2. The determination unit according to claim 1, wherein when the fixing temperature is equal to or higher than the predetermined temperature and satisfies a predetermined condition, it is determined whether or not the transfer member has been replaced. 2. The image forming apparatus according to 2.   The determination means compares the level value of the current detection signal with the level value of the previous detection signal when the level value of the detection signal is greater than or equal to the first voltage value and less than the second voltage value. 5. The image forming apparatus according to claim 1, wherein when the deviation is equal to or greater than a predetermined voltage value, it is determined that the transfer body has been replaced.   The determination means determines whether or not the cumulative value of the number of prints printed using the transfer body is equal to or greater than a predetermined cumulative threshold when the level value of the detection signal is equal to or greater than the first voltage value. When the accumulated value is less than the accumulated threshold and the level value of the detection signal is less than the second voltage value, the level value of the current detection signal and the level value of the previous detection signal are 5. The image formation according to claim 1, wherein when the deviation is equal to or greater than a predetermined voltage value, it is determined that the transfer body has been replaced. apparatus.   The determination means determines whether or not the cumulative value of the number of prints printed using the transfer body is equal to or greater than a predetermined cumulative threshold when the level value of the detection signal is equal to or greater than the first voltage value. When the cumulative value is equal to or greater than the cumulative threshold, when the level value of the detection signal is less than the third voltage value using a third voltage value lower than the second voltage value, The level value of the current detection signal is compared with the level value of the previous detection signal, and when the deviation is equal to or greater than a predetermined voltage value, it is determined that the transfer body has been replaced. The image forming apparatus according to claim 1.   The predetermined voltage value is set according to a level value of the detection signal at the initial use of the transfer body and a level value of the detection signal when the transfer body reaches the end of its life. The image forming apparatus according to claim 5, wherein the image forming apparatus is an image forming apparatus.   7. The image forming apparatus according to claim 5, wherein the second voltage value is made variable according to a set life for each transfer body. The transfer body is driven and controlled along a predetermined direction,
The image forming apparatus according to claim 1, wherein the detection sensor detects a surface state of the transfer body along the predetermined direction.   The image forming apparatus according to claim 10, wherein the determination unit uses, as the detection signal, an average value obtained by averaging detection results obtained by the detection sensor over a predetermined period.   The transfer member is formed on the image carrier while transferring the toner image formed on the image carrier and then transferring the toner image to the recording medium. The image forming apparatus according to claim 1, wherein the image forming apparatus is a conveyance transfer body that directly transfers a toner image to the recording medium.

Images