JP2019105699A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately perform a fixing process regardless of a wear state of a heating member, a pressure member and a paper. SOLUTION: A fixing device 13 of a printer 1 forms a fixing nip N between a heating member 20 for heating a toner image formed on a paper and a heating member 20, and passes the paper through the fixing nip N. The pressurizing member 21 to pressurize, the first temperature detecting unit 23 that detects the first temperature of the detection target with the heating member 20 or the pressurizing member 21 as the detection target, and the second sheet of paper after passing through the fixing nip N. A second temperature detection unit 24 for detecting the temperature is provided. Then, the control device 15 of the fixing device 13 calculates the surface roughness of the paper based on the relationship that the surface roughness of the paper increases as the difference between the first temperature and the second temperature increases. Further, the control device 15 controls the temperature so that the larger the surface roughness of the paper, the higher the fixing temperature of the heating member 20. [Selection diagram] Fig. 2

Description

  The present invention relates to a fixing device for fixing a toner image on a sheet, and an image forming apparatus provided with the fixing device.

  The image forming apparatus includes a fixing device that heats and fixes a toner image formed on a sheet. The fixing device includes a heating member that heats the toner image, and a pressing member that presses the toner image against the sheet. When the fixing device is deteriorated due to repeated driving and sheet feeding, for example, when a belt or a roller constituting the heating member or the pressing member is worn by contact with a sheet, defects such as an image defect or a fixing defect may occur. Since it is necessary to replace the deteriorated fixing device in order to suppress such a problem, it is required to determine the timing of replacing the fixing device, that is, the life (use limit) of the fixing device.

  For example, in Patent Document 1, the image forming apparatus starts printing from a state in which the fixing unit is at or below the first temperature in a predetermined period in order to suppress wear (wear) of the fixing unit (fixing device). Recording means for recording the history information to be shown, setting means for setting the time for activating the fixing means based on the history information stored in the recording means, and the fixing means having the first temperature or less at the time set by the setting means And control means for raising the temperature of the fixing means to the second temperature.

JP, 2016-080987, A

  In the fixing device, when the heating member or the pressing member and the sheet are worn by contact, the amount of heat transferred to the sheet changes according to the worn state. The wear state of the heating member, the pressing member and the sheet changes depending not only on the size of the sheet but also on the material of the sheet. Therefore, when the fixing temperature is constant, the sheet and the toner image can not be stably heated, and problems such as image defects and fixing defects may occur. In the image forming apparatus of Patent Document 1, the worn state of the heating member, the pressure member, and the sheet is not taken into consideration, which may cause a problem.

  In addition, in the fixing device, the usage limit (for example, the number of sheets of serviceable sheets for service life) of the heating member and the pressure member is set in advance, and the use of the heating member and the pressure member (for example, the number of sheets supplied) is monitored. It is determined whether the heating member or the pressing member has reached the use limit. However, the actual use limit of the heating member and the pressing member may change depending on the wear state and may become smaller than the preset use limit, so the heating member and the pressing member may be the actual use limit May be used beyond

  In the image forming apparatus, various mechanisms such as an image carrier that carries a toner image and a transport device that transports a sheet are also deteriorated by repeated driving and sheet feeding, so that the functions of the respective mechanisms are degraded. It is required to determine the usage limit of the mechanism.

  Therefore, in view of the above-described circumstances, the present invention has an object of appropriately performing fixing processing regardless of the wear state of the heating member, the pressing member, and the sheet.

  The fixing device of the present invention comprises a heating member for heating a toner image formed on a sheet, and a pressure member for forming a fixing nip between the heating member and pressing the sheet passing through the fixing nip. A first temperature detection unit that detects a first temperature of the detection target with the heating member or the pressure member as a detection target, and a second temperature that detects a second temperature of the sheet after passing through the fixing nip The surface roughness of the sheet is calculated based on the relationship that the surface roughness of the sheet increases as the difference between the first temperature and the second temperature increases, and the surface roughness is calculated. The temperature control is performed such that the fixing temperature of the heating member becomes higher as the value of the value is larger.

  The first temperature detection unit and the second temperature detection unit may be disposed on the side of the detection target with respect to the conveyance path in a direction intersecting the conveyance path of the sheet passing through the fixing nip.

  The fixing device described above may be reset so as to reduce the number of serviceable sheets, which indicates the usage limit of the fixing device, as the surface roughness is larger.

  An image forming apparatus according to the present invention includes the above-described fixing device.

  The above-described image forming apparatus further includes an image carrier that carries the toner image, and is reset so as to reduce the number of life-passing sheets indicating the usage limit of the image carrier as the surface roughness is larger. It is also good.

  The image forming apparatus may further include a conveying device for conveying the sheet, and may be reset so as to reduce the number of serviceable sheets indicating the usage limit of the conveying device as the surface roughness is larger.

  According to the present invention, the fixing process can be appropriately performed regardless of the wear state of the heating member, the pressing member, and the sheet.

FIG. 1 is a cross-sectional view showing a printer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a fixing device of a printer according to an embodiment of the present invention. FIG. 2 is a top view showing a fixing device of a printer according to an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of a fixing device of a printer according to an embodiment of the present invention. 5 is a flowchart showing an operation of a fixing process in a fixing device of a printer according to an embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view showing a heating member and a sheet in the fixing device of the printer according to the embodiment of the present invention. In the fixing device of the printer concerning one embodiment of the present invention, it is a table showing the relation of the surface correction of a sheet and the temperature amendment value of fixing temperature. In the printer concerning one embodiment of the present invention, it is a table showing the relation between the surface coarseness of paper, and the life correction value of a fixing device, an image carrier, and a conveyance device.

  First, the entire configuration of a printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. Hereinafter, for convenience of description, the front side of the sheet in FIG. 1 is referred to as the front side of the printer 1. Arrows L, R, U, and Lo appropriately attached to the drawings respectively indicate the left side, the right side, the upper side, and the lower side of the printer 1.

  The printer 1 includes a substantially box-shaped printer main body 2, a paper feed cassette 3 for storing paper (recording medium) is provided at the lower part of the printer main body 2, and a paper discharge tray 4 is provided at the upper part of the printer main body 2. Provided. Although one sheet feeding cassette 3 is illustrated in FIG. 1, the printer 1 may supply a plurality of sheets so as to accommodate a plurality of types of sheets (for example, an A4 size sheet, an A5 size sheet, an envelope, a thick sheet, etc.). A cassette 3 may be provided.

  At the top of the printer body 2, the exposure unit 5 formed of a laser scanning unit (LSU) is disposed below the discharge tray 4, and below the exposure unit 5, the image forming unit 6 is provided. . In the image forming unit 6, a photosensitive drum 7 (image carrier) carrying a toner image is rotatably provided, and around the photosensitive drum 7, a charger and a developing device connected to a toner container are provided. The transfer roller 8 and the cleaning device are disposed along the rotational direction of the photosensitive drum 7.

  Further, a sheet conveyance path 10 is provided inside the printer main body 2. A sheet feeding unit 11 (conveying device) is provided in the vicinity of the sheet feeding cassette 3 at the upstream end of the conveying path 10, and a transfer portion configured by the photosensitive drum 7 and the transfer roller 8 in the middle stream portion of the conveying path 10 12 are provided. A fixing device 13 is provided downstream of the conveyance path 10, and a paper discharge unit 14 (conveyance device) is provided near the paper discharge tray 4 at the downstream end of the conveyance path 10. In addition, inside the printer main body 2, a control device 15 that controls the fixing device 13 is provided.

  Next, an image forming operation of the printer 1 having such a configuration will be described. The printer 1 starts an image forming operation when image data is input from an external computer or the like and an instruction to start printing is issued. For example, the printer 1 inputs and accumulates print jobs of image data, sequentially processes the accumulated print jobs by the image forming operation, and deletes the print job after the process. One print job may designate printing of one sheet, or may designate printing of a plurality of sheets. The print job may also specify the type of paper.

  In the image forming operation, first, after the surface of the photosensitive drum 7 is charged by the charger of the image forming unit 6, the laser beam from the exposing unit 5 exposes the photosensitive drum 7 to light corresponding to the image data. And an electrostatic latent image is formed on the surface of the photosensitive drum 7. Next, the developing device of the image forming unit 6 develops the electrostatic latent image into a toner image using toner.

  On the other hand, among the sheets stored in the sheet feeding cassette 3, the sheet designated by the print job is taken out by the sheet feeding unit 11 and conveyed on the conveyance path 10. The sheet on the conveyance path 10 is conveyed to the transfer unit 12 at a predetermined timing, and the toner image on the photosensitive drum 7 is transferred to the sheet by the transfer unit 12. The sheet on which the toner image has been transferred is conveyed to the fixing device 13, and the toner image is fixed on the sheet by the fixing device 13. The sheet on which the toner image is fixed is discharged from the sheet discharge unit 14 to the sheet discharge tray 4.

  Next, the configuration of the fixing device 13 will be described with reference to FIGS. As shown in FIG. 2, the fixing device 13 includes a heating member 20 and a pressure member 21. The fixing device 13 also includes a drive source 22 (see FIG. 4), a first temperature detection unit 23 and a second temperature detection unit 24. The heating member 20 and the pressing member 21 are disposed to face each other across the conveyance path 10 and in contact with each other, and a fixing nip N is formed between the heating member 20 and the pressing member 21.

  The heating member 20 is formed of a cylindrical fixing roller which is long in the width direction (front-rear direction) of the sheet perpendicular to (crossing) the sheet conveyance direction (left-right direction). The heating member 20 is disposed at the top in a frame (not shown) of the fixing device 13. The heating member 20 is rotatably attached to the frame with the front-rear direction as the rotation axis direction, and is rotated following the rotation of the pressure member 21. The heating member 20 is composed of, for example, a cylindrical metal core material, and an elastic layer made of resin such as silicone rubber provided around the core material, and the elastic layer is a fluorine-based resin such as PFA, and a release layer. Is covered by In the present embodiment, an example in which the heating member 20 is configured by a roller will be described, but the heating member 20 may be configured by a belt.

  A heat source 25 is provided inside the heating member 20 to heat the heating member 20 in the width direction of the sheet. The heat source 25 is configured of, for example, a halogen heater, a ceramic heater, or the like. The heat source 25 is switched on and off by the control device 15, and generates heat when supplied with power from a power supply (not shown) when it is turned on to heat the heating member 20. The power supply is shut off to stop the heating of the heating member 20. Alternatively, the heat source 25 may be provided outside the heating member 20 and configured to heat the heating member 20 from the outside, and is not limited to a halogen heater or a ceramic heater, and may be an IH heater.

  The pressure member 21 is formed of a substantially cylindrical roller long in the width direction (front-rear direction) of the sheet. The pressure member 21 is disposed at a lower portion in a frame (not shown) of the fixing device 13, for example, below the heating member 20 so that the outer circumferential surface of the heating member 20 is opposed to each other. The pressing member 21 is rotatably attached to the frame with the front-rear direction as a rotation axis direction, and is rotated by a rotational driving force transmitted from a driving source 22 (see FIG. 4) such as a motor. The pressing member 21 is constituted of, for example, a cylindrical metal core material and an elastic layer such as silicone rubber provided around the core material, and the elastic layer may be covered with a mold release layer. In the present embodiment, an example in which the pressing member 21 is configured by a roller will be described, but the pressing member 21 may be configured by a belt.

  The first temperature detection unit 23 is disposed upstream of the heating member 20 and the pressing member 21 (i.e., the fixing nip N) in the conveyance path 10. Further, the first temperature detection unit 23 is disposed on the heating member 20 side and the pressing member 21 side with respect to the conveyance path 10 in the direction (vertical direction) intersecting the conveyance path 10. The first temperature detection unit 23 is configured of a temperature sensor such as an infrared temperature sensor that detects the temperature of the detection target without contact. The first temperature detection unit 23 on the heating member 20 side detects the surface temperature of the heating member 20 before entering the fixing nip N (preferably just before entering) as a detection target, and detects the first temperature on the pressure member 21 side. The unit 23 detects the surface temperature of the pressure member 21 before entering the fixing nip N (preferably, immediately before entering) as a detection target.

  The second temperature detection unit 24 is disposed downstream of the heating member 20 and the pressing member 21 (i.e., the fixing nip N) in the conveyance path 10. In addition, the second temperature detection unit 24 is disposed on the heating member 20 side and the pressing member 21 side with respect to the conveyance path 10 in a direction (vertical direction) intersecting the conveyance path 10. The second temperature detection unit 24 is configured of a temperature sensor such as an infrared temperature sensor that detects the temperature of the detection target without contact. The second temperature detection unit 24 on the heating member 20 side detects the surface temperature of the sheet on the heating member 20 side of the sheet after passing through the fixing nip N (preferably immediately after the passage) as a detection target. The second temperature detection unit 24 detects the surface temperature of the sheet on the pressure member 21 side after passing (preferably immediately after) passing through the fixing nip N as a detection target.

  The first temperature detection unit 23 and the second temperature detection unit 24 are provided one by one at positions facing each other across the heating member 20 and the pressure member 21 at the center in the width direction of the sheet, as shown in FIG. Be Alternatively, the first temperature detection unit 23 and the second temperature detection unit 24 are provided at positions facing each other across the heating member 20 and the pressure member 21 at a plurality of locations (for example, the center and both ends) in the sheet width direction. It is also good.

  Next, the electrical configuration of the control device 15 for controlling the fixing device 13 will be described with reference to FIG. The control device 15 is configured by a CPU or the like, and is connected to a storage device 16 such as a ROM or a RAM. As the control device 15 and the storage device 16, a main control device and a main storage device that integrally control the respective units of the printer 1 may be applied.

  The control device 15 controls each unit connected to the control device 15 based on a control program and control data stored in the storage device 16. For example, the control device 15 is connected to the drive source 22 of the fixing device 13, the first temperature detection unit 23, the second temperature detection unit 24, and the heat source 25. When the printer 1 processes a print job, the control device 15 controls the fixing device 13 so that the fixing process corresponding to the print job is performed. The fixing process includes a surface roughness calculation process for calculating the surface roughness Zb of the sheet to be used, and a temperature control process for controlling the fixing temperature of the heating member 20 based on the calculated surface roughness Zb. In the storage device 16, the relationship between the surface roughness Zb of the sheet and the temperature correction value of the fixing temperature of the heating member 20 is stored in advance.

  Next, the fixing process of the fixing device 13 will be described with reference to FIG.

  When printing is performed on the first sheet of the predetermined print job (step S1: YES), the control device 15 causes the heating member 20 of the fixing device 13 to have a predetermined fixing temperature, The heating of the heating member 20 by the heat source 25 is controlled (step S2). Then, the fixing process is performed on the first sheet (step S3), and the sheet on which the toner image is formed has the fixing nip N between the heating member 20 and the pressure member 21 at the fixing temperature. The toner image is fixed to the sheet by passing.

  Here, when the sheet is passed through the fixing nip N, the first temperature detection unit 23 detects the surface temperature (first temperature T1) of at least one of the heating member 20 and the pressing member 21 and detects the second temperature. The unit 24 detects the surface temperature (second temperature T2) of at least one side of the heating member 20 and the pressing member 21 of the sheet after passing through the fixing nip N (step S4). The control device 15 calculates the surface roughness Zb of the sheet based on the first temperature T1 detected by the first temperature detection unit 23 and the second temperature T2 detected by the second temperature detection unit 24. Calculation processing is performed (step S5).

In the surface roughness calculation process, for example, the first temperature T1 of the heating member 20 and the second temperature T2 of the sheet on the heating member 20 side are used. The temperature difference ΔT (T1-T2) [K] of the contact interface between the heating member 20 and the sheet and the contact thermal resistance R [m ² K / W] regarding the transfer of the contact heat between the heating member 20 and the sheet in the fixing process. The following equation (1) holds true using

In equation (1), hc [W / m ² K] represents the contact heat transfer coefficient of the heating member 20 and the sheet, and q [W / m ² ] represents the heat flux of the contact interface between the heating member 20 and the sheet. Show. The control device 15 can calculate the contact thermal resistance R of the heating member 20 and the sheet, using this equation (1). Further, regarding the contact thermal resistance R of the heating member 20 and the sheet, and the surface roughness (surface roughness height) Za and Zb [μm], the relationship of the following equation (2) holds.

In Equation (2), ka and kb [W / mK] indicate the thermal conductivity of the heating member 20 and the sheet, and kf [W / mK] indicates the heat of the intervening member (air) of the heating member 20 and the sheet The conductivity is shown, h 0 [m 2 K / W] shows the additional conductance, A [m ² ] shows the true contact area of the heating member 20 and the sheet, and Aa [m ² ] shows the heating member 20 and the sheet. The contact area is shown. The additional conductance h0 is a constant (for example, 1.98 × 10 ⁻⁵ (1 / ka + 1 / kb)).

  The contact area Aa is an apparent contact area of the heating member 20 and the sheet, and the true contact area A is an area where the minute unevenness of the surface of the heating member 20 and the sheet actually contacts as shown in FIG. It is. The true contact area A is calculated by the following equation (3).

  In equation (3), p [Pa] is the pressure between the heating member 20 and the sheet (nip pressure of the fixing nip N), and Ea and Eb [Pa] are the Young's modulus of the heating member 20 and the sheet , Μa and μb are Poisson's ratios of the heating member 20 and the sheet.

  The surface roughness (surface roughness height) Za and Zb of the heating member 20 and the paper is the height of the minute unevenness on each surface. Since the surface of the heating member 20 is made of a fluorine material, the surface roughness Za is very small compared to the paper. In other words, the variation of the surface roughness Za of the heating member 20 is very small compared to the variation of the surface roughness Zb of the sheet. Therefore, in the present embodiment, the surface roughness Za of the heating member 20 is used as a constant value.

  The control device 15 calculates the surface roughness Zb of the sheet based on the temperature difference ΔT (T1-T2) of the heating member 20 and the sheet by using the above formulas (1), (2) and (3). can do. According to the above equations (1), (2) and (3), regarding the relationship between the temperature difference ΔT and the surface roughness Zb of the sheet, the temperature difference ΔT becomes larger as the surface roughness Zb of the sheet becomes larger. It shows that it becomes. In other words, the control device 15 calculates the surface roughness Zb of the sheet based on the relationship that the surface roughness Zb increases as the temperature difference ΔT increases.

  After calculating the surface roughness Zb of the sheet, the control device 15 determines a temperature correction value of the fixing temperature of the heating member 20 when the sheet is used (step S6). The relationship between the surface roughness Zb of the sheet and the temperature correction value of the fixing temperature of the heating member 20 is stored, for example, in a temperature correction table as shown in FIG. In this relationship, the temperature correction value indicates such control that the fixing temperature is increased as the surface roughness Zb of the sheet becomes higher (larger). Then, the control device 15 determines (acquires) a temperature correction value of the fixing temperature based on the sheet surface roughness Zb and the temperature correction table. The temperature correction value is stored and maintained in the storage device 16 while the same sheet is used. Note that the storage device 16 stores a mathematical expression capable of calculating the temperature correction value of the fixing temperature based on the surface roughness Zb of the sheet instead of the temperature correction table, and the control device 15 fixes the value based on this mathematical expression. A temperature correction value of temperature may be calculated.

  After the fixing process of the first sheet of the print job described above is completed, the next sheet (the second and subsequent sheets of the same print job, and other print jobs successively performed with the same print settings) Of the first sheet (step S7: YES, step S1: NO), the control device 15 sets a predetermined fixing temperature for the heating member 20 of the fixing device 13 to one sheet. The correction is performed using the temperature correction value of the fixing temperature calculated for the sheet of eye (step S8). Here, the fixing process of the next subsequent sheet is, for example, the fixing of the second and subsequent sheets of the same print job, and the first and subsequent sheets of other print jobs successively performed with the same print setting. It is a process.

  Further, the control device 15 controls the heating of the heating member 20 by the heat source 25 so as to achieve the corrected fixing temperature (step S8). Then, the fixing process of the next subsequent sheet is performed (step S9), and the sheet on which the toner image is formed is passed through the fixing nip N between the heating member 20 and the pressure member 21 at the fixing temperature. The toner image is fixed to the sheet.

  If there is no continuous fixing process for another sheet, the temperature correction value of the fixing temperature calculated for the first sheet may be reset (set to zero).

  In the surface roughness calculation process of the fixing process described above, although an example using the first temperature T1 of the heating member 20 and the second temperature T2 of the sheet on the heating member 20 side has been described, the present invention is not limited to this example. For example, in the surface roughness calculation process, the first temperature T1 of the pressure member 21 and the second temperature T2 of the sheet on the pressure member 21 side may be used. In this case, in the equation (1), the contact heat transfer coefficient hc of the pressure member 21 and the sheet, and the heat flux q of the contact interface between the pressure member 21 and the sheet are used. The contact thermal resistance R of the pressure member 21 and the sheet is calculated based on (T1-T2). In the equation (2), the thermal conductivity ka of the pressure member 21, the thermal conductivity kf of the pressure member 21 and the intervening fluid of the sheet, the surface roughness Za of the pressure member 21 as a constant value, the pressure member The surface roughness Zb of the sheet is calculated using the actual contact area A and the contact area Aa of the sheet 21 and the sheet. In Equation (3), it is the pressure p between the pressing member 21 and the sheet (nip pressure of the fixing nip N), using the Young's modulus Ea of the pressing member 21 and the Poisson's ratio μa of the pressing member 21. The true contact area A of the pressure member 21 is calculated.

  According to the present embodiment, as described above, the fixing device 13 of the printer 1 (image forming apparatus) includes the fixing nip N between the heating member 20 for heating the toner image formed on the sheet and the heating member 20. A first temperature detection unit that detects a first temperature T1 of the detection target, with the pressure member 21 that pressurizes the sheet passing through the fixing nip N and the heating member 20 or the pressure member 21 as a detection target. And a second temperature detection unit that detects a second temperature T2 of the sheet after passing through the fixing nip N. Then, the control device 15 of the fixing device 13 determines the surface roughness Zb of the sheet based on the relationship that the surface roughness Zb of the sheet increases as the temperature difference ΔT between the first temperature T1 and the second temperature T2 increases. calculate. Further, the control device 15 performs temperature control such that the fixing temperature of the heating member 20 is higher as the surface roughness Zb of the sheet is larger.

  Usually, the fixing temperature of the heating member 20 is preset according to the basis weight set for each sheet in the print setting of the printer 1. However, since the amount of heat transferred from the heating member 20 or the pressing member 21 to the sheet changes with the surface roughness Zb of the sheet, the temperature of the sheet also changes. In addition, when the performance of the fixing device 13 regarding the fixing process changes due to the change of the temperature of the sheet, an appropriate fixing process may not be performed at a predetermined fixing temperature. On the other hand, in the fixing device 13 of the present embodiment, the fixing temperature is controlled to be changed according to the surface roughness Zb of the sheet. As a result, in the fixing device 13, an appropriate fixing temperature is set regardless of the wearing state of the heating member 20, the pressing member 21, and the sheet, so that the fixing process can be appropriately performed.

  Further, in the fixing device 13, the first temperature detection unit 23 and the second temperature detection unit 24 are heating members as detection targets with respect to the conveyance path 10 in a direction intersecting the conveyance path 10 of the sheet passing through the fixing nip N 20 or the side of the pressure member 21. Thus, the first temperature detection unit 23 appropriately detects the first temperature T1 of the heating member 20 or the first temperature T1 of the pressing member 21 required for calculation of the surface roughness Zb of the sheet. The second temperature detection unit 24 can appropriately detect the second temperature T2 of the sheet on the side or the second temperature T2 of the sheet on the pressure member 21 side. In particular, the second temperature detection unit 24 can detect the second temperature T2 of the sheet immediately after passing through the fixing nip N.

  In the embodiment described above, an example in which the first temperature detection unit 23 and the second temperature detection unit 24 are respectively provided on the heating member 20 side and the pressure member 21 side with respect to the transport path 10 has been described. Of the member 20 side and the pressure member 21 side, it may be provided only on one side to be detected.

  When the first temperature T1 of the heating member 20 and the second temperature T2 of the sheet on the heating member 20 side are used in the surface roughness calculation process, the pressure detected by the first temperature detection unit 23 on the pressure member 21 side is used. The first temperature T1 of the heating member 20 may be estimated and calculated based on the temperature of the pressure member 21, and the sheet on the pressure member 21 side detected by the second temperature detection unit 24 on the pressure member 21 side The second temperature T2 of the sheet on the heating member 20 side may be estimated and calculated based on the temperature of. The same applies to the case of using the first temperature T1 of the pressure member 21 and the second temperature T2 of the sheet on the pressure member 21 side in the surface roughness calculation process.

  Furthermore, according to another embodiment, the fixing device 13 is configured to predict the life of the fixing device 13 based on the surface roughness Zb of the sheet calculated as described above. The fixing device 13 is deteriorated due to repeated driving and sheet feeding, and for example, when the belts and rollers constituting the heating member 20 and the pressing member 21 wear due to contact with the sheet, problems such as image defects and fixing defects occur. Sometimes. Therefore, in the fixing device 13, the life driving time from the start of use and the number of paper sheets passed from the start of use are set in advance as the life indicating the use limit until safe use without defects such as image defects and fixing defects. It is stored in the device 16. Then, when the use of the fixing device 13 has reached the end of its life, the printer 1 gives a warning for prompting replacement of the fixing device 13 or gives notification that printing can not be continued.

  In the fixing device 13 of the present embodiment, the control device 15 calculates the surface roughness Zb not only for the first sheet of the print job but also for all the sheets that are passed through the fixing nip N. The calculation of the surface roughness Zb of these sheets is performed in the same manner as the surface roughness calculation processing of the above embodiment.

  Further, in the fixing device 13 of the present embodiment, the control device 15 determines the life correction value of the life of the fixing device 13 after calculating the surface roughness Zb of the sheet. The storage device 16 stores in advance the relationship between the surface roughness Zb of the sheet and the life correction value. For example, the storage unit 16 stores, for example, a life correction table as shown in FIG. 8 with respect to the relationship between the surface roughness Zb of the sheet and the life correction value (life prediction coefficient) of the number of service life sheets of the fixing device 13. doing. In this relationship, the life correction value indicates control such that the number of sheets passed for life is reduced as the surface roughness Zb of the sheet becomes higher (larger).

  By the way, the wear of the heating member 20 and the pressure member 21 of the fixing device 13 when the sheet is passed through the fixing device 13 is the roughness of these members and the paper, the pressure on the paper, the speed difference between the members, It depends on factors such as the speed difference with the sheet and the friction time with the sheet. Therefore, the wear amount of each member may be calculated for each surface roughness Zb of the sheet, and the life correction value for each surface roughness Zb of the sheet may be calculated or set in advance based on the wear amount. Alternatively, the life correction value for each surface roughness Zb of the sheet may be set in advance based on the experimental result in which the fixing process of the fixing device 13 is previously tested.

  Then, every time fixing processing of a sheet of paper is performed, the control device 15 determines (acquires) the life correction value for the sheet based on the surface roughness Zb of the sheet and the life correction table. The storage unit 16 stores a formula capable of calculating the life correction value based on the surface roughness Zb of the sheet instead of the life correction table, and the control unit 15 uses the life correction value based on this formula It may be calculated. Then, the controller 15 subtracts the number of sheets corresponding to the life correction value from the number of life passed sheets to correct the number of life passed sheets (i.e., reset the number of life passed sheets), and the storage device 16 Remember to

  According to the above relationship, for example, in the case of a sheet of 40 μm or more, the life correction value per sheet passing is −0.2. When 1000 sheets of 40 μm or more are passed, the amount of subtraction from the number of end-of-life sheets is 1000 (number of sheets passed) × −0.2 (end-of-life correction value) = − 200. In the fixing device 13 in which the lifetime sheet number of 10000 sheets is set, the lifetime sheet number is reduced to 10000 (the original lifetime sheet number) −200 (subtraction amount) = 9800 and corrected.

  According to the present embodiment, as described above, as the surface roughness Zb of the sheet to be fed is larger, the fixing device 13 of the printer 1 reduces the number of serviceable sheets indicating the usage limit of the fixing device 13. Configured to reconfigure.

  In the fixing device 13, for example, if the surface roughness Zb of the sheet is constant over the lifetime, the wear amount of the heating member 20 and the pressing member 21 per sheet passing will also be constant. The number of life passed sheets of the fixing device 13 may be calculated in advance based on a fixed amount of wear of the heating member 20 and the pressing member 21. However, since the material of the sheet to be passed through the fixing device 13 is not limited, the sheet with various surface roughness Zb contacts the heating member 20 and the pressing member 21 and the heating member 20 and the pressing member The wear amount 21 may vary depending on the material of the sheet (surface roughness Zb). Therefore, the service life of the heating member 20 or the pressure member 21 may be reached before the preset service life number of sheets is reached.

  On the other hand, in the present embodiment, an appropriate life of the fixing device 13 (the heating member 20 and the pressing member 21) is predicted on the basis of the surface roughness Zb of the sheet to be passed through the fixing device 13. The usage limit of the fixing device 13 is reset. Therefore, it is possible to suppress that the fixing device 13 is used beyond the lifetime due to the unevenness of the surface roughness Zb of the sheet.

  Further, in the printer 1, not only the fixing device 13 but also the photosensitive drum 7 (image carrier) and the transfer roller 8 (transfer unit 12) are in contact with the sheet to transfer the toner image to the sheet. . Therefore, in the printer 1, the number of sheets passing through the life is previously set and stored as the life indicating the use limit until the photosensitive drum 7 and the transfer roller 8 can be used safely. For example, as shown in FIG. 8, the storage device 16 has a relationship between the surface roughness Zb of the sheet and the life correction value (life prediction coefficient) of the number of service life sheets of the photosensitive drum 7 (image carrier). Stores the life correction table. Therefore, the printer 1 has a large surface roughness Zb similar to the number of life-passing sheets of the fixing device 13 based on the surface roughness Zb of the sheet calculated by the surface roughness calculation process in the fixing process of the fixing device 13 It is preferable that the setting be made so as to reduce the number of service life sheets of the photosensitive drum 7 and the transfer roller 8 as much as possible. As a result, it is possible to suppress that the photosensitive drum 7 and the transfer roller 8 are used beyond the life due to the uneven surface roughness Zb of the sheet.

  Furthermore, in the printer 1, the transport devices such as the paper feed unit 11 and the paper discharge unit 14 also contact the paper in order to transfer the toner image to the paper. Therefore, in the printer 1, the number of sheets passing through the life is set and stored in advance as the life indicating the use limit until it can be used safely for the conveyance devices such as the paper feed unit 11 and the paper discharge unit 14. For example, the storage device 16 may have a relationship between the surface roughness Zb of the sheet and the life correction value (life prediction coefficient) of the number of serviceable sheets of conveyance devices such as the paper feed unit 11 and the paper discharge unit 14. A life correction table as shown in 8 is stored. Therefore, the printer 1 has a large surface roughness Zb similar to the number of life-passing sheets of the fixing device 13 based on the surface roughness Zb of the sheet calculated by the surface roughness calculation process in the fixing process of the fixing device 13 It is preferable that the setting be made so as to reduce the number of end-of-life sheets of the conveyance device such as the paper feed unit 11 and the paper discharge unit 14. As a result, it is possible to suppress that the transport devices such as the paper feed unit 11 and the paper discharge unit 14 are used beyond the life due to the uneven surface roughness Zb of the paper.

  In the present embodiment, the case where the configuration of the present invention is applied to a monochrome printer 1 has been described, but in another different embodiment, the present invention is applied to another image forming apparatus such as a color printer, a copier, a facsimile, and a multifunction machine. It is also possible to apply the configuration of

1 Printer (image forming device)
6 Image Forming Unit 7 Photosensitive Drum (Image Carrier)
8 transfer roller 10 transport route 11 paper feed unit (transport device)
12 transfer unit 13 fixing device 14 discharge unit (conveying device)
Reference Signs List 15 control device 20 heating member 21 pressing member 22 driving source 23 first temperature detection unit 24 second temperature detection unit 25 heat source

Claims (6)

A heating member for heating a toner image formed on a sheet;
A pressure member forming a fixing nip with the heating member to press the sheet passing through the fixing nip;
A first temperature detection unit that detects a first temperature of the detection target with the heating member or the pressure member as the detection target;
A second temperature detection unit that detects a second temperature of the sheet after passing through the fixing nip;
Equipped with
The surface roughness of the sheet is calculated based on the relationship that the surface roughness of the sheet increases as the difference between the first temperature and the second temperature increases.
A fixing device characterized in that temperature control is performed such that the fixing temperature of the heating member becomes higher as the surface roughness is larger.   The first temperature detection unit and the second temperature detection unit are disposed on the side of the detection target with respect to the transport path in a direction intersecting the transport path of the sheet passing through the fixing nip. The fixing device according to claim 1.   The fixing device according to claim 1, wherein the fixing device is reset so as to reduce the number of service life sheets indicating the use limit of the fixing device as the surface roughness is larger.   An image forming apparatus comprising the fixing device according to any one of claims 1 to 3. It further comprises an image carrier for carrying the toner image,
The image forming apparatus according to claim 4, wherein the image forming apparatus is reset so as to reduce the number of lifetime sheet passing indicating the usage limit of the image carrier as the surface roughness is larger. The apparatus further comprises a conveying device for conveying the sheet.
6. The image forming apparatus according to claim 4, wherein the image forming apparatus is reset so as to reduce the number of sheets of service life that indicates the usage limit of the transport device as the surface roughness is larger.

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