JP2005301070A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately control a fixing apparatus without necessitating a complicated mechanism or control by estimating the change in stiffness of an elastic pressurizing roller and nip width by detecting the degree of aging in the fixing apparatus and by varying a control parameter of the fixing apparatus according to it. <P>SOLUTION: The image forming apparatus is provided with the fixing apparatus 8 fixing a developer image on recording material P. The number of pieces of paper which passed in the fixing apparatus 8 (or the number of rotation for a fixing film) is detected as the degree of aging in the fixing apparatus 8. Target temperature adjustment temperature is reduced in steps according to the degree of aging in the fixing apparatus 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device that is used in an image forming apparatus and melts and fixes a developer image on a recording material.

  Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a printer, and a fax machine, a developer (toner) made of a heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording, or magnetic recording. Is used to form an unfixed toner image directly or indirectly on the surface of a recording material (typically paper), and this unfixed toner image is heated and pressed together with the recording material to form a recording material surface. An image is formed by fixing as a permanently fixed image.

  For example, in an electrophotographic laser beam printer as shown in FIG. 1, first, an image carrier whose surface is uniformly charged by a charging device 2 based on an image information signal sent from a host computer (not shown). An electrostatic latent image is formed on the photosensitive drum 1 by irradiating a laser from a scanner 3 as exposure means. Next, due to the rotation of the photosensitive drum 1 in the arrow direction A, the electrostatic latent image is transported to the opposing portion between the developing device 4 and the photosensitive drum 1 and is sequentially developed by the developing device 4. The developed toner images are sequentially transferred by the transfer device 5 to the recording material P sent from the paper feed cassette 7. The recording material P to which the toner image has been transferred is separated along with the rotation of the photosensitive drum 1, and the recording material P passes through the fixing nip portion N in the fixing device 8 to melt and fix the unfixed toner image.

  As the fixing device 8, in addition to the heat roller method, a film heating method device and an electromagnetic induction heating method device have been proposed from the viewpoint of quick start and energy saving. Below, the outline | summary is demonstrated about several heating systems.

a) Heat roller system This is based on a pressure roller pair consisting of a fixing roller (heating roller) and a pressure roller, and the pressure roller pair is rotated to a fixing nip portion (heating nip portion) which is the mutual pressure contact portion. The recording material P on which an unfixed toner image to be image-fixed is formed and supported is nipped and conveyed, and the unfixed toner image is fixed to the surface of the recording material by heat of the fixing roller and the pressure of the fixing nip portion. It is. The fixing roller is generally an aluminum hollow metal roller (core metal), and a halogen lamp as a heat source is inserted and arranged at the center thereof, and the outer peripheral surface is maintained at a predetermined fixing temperature by being heated by the heat generated by the halogen lamp. In this way, the temperature is controlled by controlling the energization of the halogen lamp. Some elastic pressure rollers are also provided with a heat source so that the elastic pressure roller is also heated and temperature-controlled.

  In the heat roller system, since the heat capacity of the fixing roller is large, a considerable waiting time (wait time) is required after the power is turned on until the fixing roller rises to a predetermined temperature. Even after the temperature rises, it is necessary to control the fuser roller temperature to be always high by energizing the heat source (halogen lamp, etc.) of the fuser roller during standby so that the image can be output immediately from the image forming device. Therefore, there were problems such as high energy consumption.

b) Film Heating System A film heating system fixing device has been proposed in, for example, Patent Document 1 and Patent Document 2. That is, a ceramic heater is generally used as a heating body, and a fixing nip is formed by sandwiching a heat resistant film (fixing film, fixing belt) between an elastic pressure roller as a pressing member, and fixing of the fixing nip is performed. The recording material P on which an unfixed toner image to be image-fixed is formed and supported is introduced between the film and the pressure roller, and is nipped and conveyed together with the fixing film, so that the heat of the ceramic heater is increased in the fixing nip portion. This is applied to the recording material P through a fixing film, and an unfixed toner image is fixed to the surface of the recording material by heat and pressure by the pressure applied at the fixing nip portion.

  Such a film heating type fixing device can constitute a so-called on-demand type fixing device using a ceramic heater and a member having a low heat capacity as a fixing film, and can execute image formation when the image forming apparatus is turned on. The waiting time is short (quick start), so it is only necessary to energize the ceramic heater as a heat source to generate heat at a predetermined fixing temperature only when the image forming apparatus performs image formation. Since the power supply to the body can be turned off, there is an advantage that the power consumption during standby is significantly small (power saving).

c) Electromagnetic induction heating method Patent Document 3 proposes a heating device that generates eddy currents in the fixing film itself or a conductive member close to the fixing film and generates heat by Joule heat. In this electromagnetic induction type / film heating method, since the heat generation area can be brought close to the heated object, the efficiency of energy consumption can be improved.

In a film heating type heating device or electromagnetic induction type / film heating type heating device, a driving method of a cylindrical or endless film-like fixing film as a rotating body is a film guide member that guides the inner peripheral surface of the fixing film ( The fixing film pressed by the elastic pressure roller (the film support member) is driven by the elastic pressure roller to be driven and rotated (pressure roller driving method), or conversely, the fixing film is stretched by the driving roller and the tension roller. For example, an elastic pressure roller is driven to rotate by driving an endless film-like fixing film.
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-7-114276 JP-A-8-254913

  However, in the conventional fixing device, the nip width may change depending on the usage time due to the secular change of the hardness of the elastic pressure roller. As the number of sheets passed increases due to secular change, the pressure roller hardness decreases and the nip width widens. As a result, compared to the amount of heat required to fix the unfixed image initially, more heat is added in the latter half of the aging process, which promotes a decrease in the hardness of the pressure roller. In addition to reducing the life of the device, offset is also likely to occur.

  In particular, in the film heating and fixing apparatus driven by the elastic pressure roller, there are problems such as a fixing film slip in which the fixing film and the recording material P slip when the recording material P is conveyed and the image is disturbed, and a fixing jam caused by the fixing film slip. It sometimes occurred.

  There is also a method proposed in Patent Document 4 as a solution to this problem, but this method is complicated because the nip width is kept constant by varying the pressure applied to the elastic pressure roller and the heating member. There is a problem of having a simple mechanism and control.

  The present invention has been made in view of the circumstances as described above, and its purpose is to estimate the change in the elastic pressure roller hardness and the nip width by detecting the degree of aging of the fixing device and respond accordingly. Accordingly, it is an object of the present invention to provide a fixing device that solves the above-mentioned problems without requiring a complicated mechanism or control by changing control parameters of the fixing device.

  An image forming apparatus according to the present invention is an image forming apparatus provided with a fixing device for fixing a developer image on a recording material, the secular change detecting means for detecting the degree of aging of the fixing device, and the fixing device. And a control unit that changes a control parameter of the fixing device in accordance with a detection result of the secular change detection unit.

  The secular change detection means can estimate, for example, a nip width variation due to a decrease in the pressure roller hardness by detecting the degree of aging of the fixing device. The control means can appropriately control the fixing device without requiring a complicated mechanism or control by changing the control parameter of the fixing device in accordance with the estimated nip width.

  The aging change detecting means has a sheet passing number detecting means for detecting the number of passing sheets with respect to the fixing device, and detects the degree of aging change based on the detected number of passing sheets. Alternatively, the fixing device forms a fixing nip portion by bringing a pair of fixing rotators into contact with each other, and the recording material carrying an unfixed developer image is nipped and conveyed at the fixing nip portion. The aging change detecting means has a rotation detecting means for detecting the rotation of the fixing rotator, and detects the degree of aging based on the detected number of rotations.

  The control unit can change the control parameters of the fixing device step by step every time the degree of aging of the fixing device reaches a predetermined value.

  When the fixing device includes a heating member for fixing an unfixed image, the control parameter of the control unit is, for example, a target temperature adjustment temperature of the heating member. More specifically, the fixing device includes a heating member for fixing an unfixed image, and the control unit decreases the value of the target temperature adjustment temperature of the fixing device as the degree of aging increases. I will do it.

  According to the present invention, the degree of aging of the fixing device is detected, and the control parameter of the fixing device is changed according to the detection result, so that fixing can be performed even if the nip width of the fixing device increases due to aging. Since only the necessary temperature can be supplied to the heater, power consumption can be reduced. Further, by supplying an optimum temperature in accordance with the nip width, it is possible to suppress the reduction in the hardness of the pressure roller and extend the life of the fixing device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of an image forming apparatus including a fixing device according to a first embodiment of the present invention. In the present embodiment, a laser beam printer will be described as an example of the image forming apparatus according to the present invention. However, the present invention is not limited to application to a laser printer.

  First, the configuration of the laser beam printer will be described with reference to FIG.

  This laser beam printer includes a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is rotatably supported by the apparatus main body M, and is rotationally driven at a predetermined speed (for example, a process speed of 131 mm / sec) in the direction of arrow A by a driving unit (not shown). Around the photosensitive drum 1, a charging roller 2 as a charging device that uniformly charges the photosensitive drum 1 in almost the order along the rotation direction, a laser scanner 3 as an exposure unit for forming an electrostatic latent image, A developing device 4 that visualizes the electrostatic latent image with toner, a transfer roller 5 that is a transfer device for transferring the toner image on the photosensitive drum 1 to a sheet-like recording material P such as paper, and the photosensitive drum 1 A cleaning device 6 for collecting untransferred toner remaining on the top is disposed.

  A paper feed cassette 7 containing a recording material P is disposed at the lower part of the apparatus main body M, and a fixing device 8 according to the present invention is disposed at the upper part of the photosensitive drum 1. Further, a control board 9 for controlling an image forming operation and the like is disposed on the back surface of the apparatus main body M. On the control board 9, there are mounted a main body CPU 9a that issues a command to execute an image forming operation and the like, a fixing CPU 9b that executes fixing temperature control and the like, and a memory 9c that stores a program and the like. The operation of the printer is realized by these CPUs reading and executing a necessary program from the memory 9c (the same is true of the processing according to the flowchart described in detail later).

  Next, the operation of the laser beam printer configured as described above will be described.

  The photosensitive drum 1 rotated in the direction of arrow A by a driving means (not shown) is uniformly charged to a predetermined polarity and a predetermined potential (for example, −585 V) by the charging roller 2. The surface of the photosensitive drum 1 after charging is subjected to image exposure based on image information by a laser scanner 3 serving as an exposure unit, and the charge of the exposed portion is removed to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 4. The developing device 4 has a developing sleeve 4a whose surface is coated with carbon on an aluminum roller. A predetermined developing bias (for example, AC: 2400 Hz, 1.6 KVpp / DC: -455V) is applied to the developing sleeve 4a. A toner is attached to the electrostatic latent image on the photosensitive drum 1 and developed (visualized) as a toner image.

  The toner image is transferred to the recording material P such as paper by the transfer roller 5. The recording material P is stored in a paper feed cassette 7, and is conveyed by a paper feed roller and a conveyance roller (not shown), and is conveyed to a transfer nip portion N between the photosensitive drum 1 and the transfer roller 5.

  The recording material P carrying the unfixed toner image on the surface by transfer is transported to the fixing device 8 along a transport guide (not shown). In the fixing device 8, the unfixed toner image is heated and pressed to melt the toner, and is fixed on the surface of the recording material P. The specific configuration of the fixing device 8 will be described in detail later.

  On the other hand, after the toner image is transferred, the toner remaining on the surface without being transferred to the recording material P is removed by the cleaning blade 6a of the cleaning device 6 and used for the next image formation.

  By repeating the above operation, image formation can be performed one after another.

  The apparatus main body M has a counter (sheet passing number detecting means) 10 that counts the number of passing sheets of the recording material P. In the present embodiment, whether or not the user can recognize the value of the counter is not particularly important and may be any. In this embodiment, the degree of aging of the fixing device 8 is detected using this count value. The method for detecting the number of sheets to be passed may be the detection of the number of paper feed command signals to the paper feed cassette 7 or the detection of the number of print job end signals detected by the main body CPU 9a in the control board 9.

  Next, an example of the fixing device 8 used in the printer shown in FIG. 1 will be described in detail with reference to FIG. This figure is a longitudinal sectional view cut along the conveyance direction (arrow B direction) of the recording material P. The fixing device 8 is in contact with a ceramic heater 20 as a heating body for heating toner, a fixing film (fixing rotating body) 25 which is a cylindrical film member including the ceramic heater 20, and the fixing film 25. The pressure roller 26 as another fixing rotator and temperature control means for controlling the temperature of the ceramic heater 20 are configured as main components. The temperature control means includes a thermistor (temperature detection element) 21 attached to the back surface of the ceramic heater 20 and a fixing CPU 9b that controls the triac 24 based on the temperature detected by the thermistor 21 and controls the energization of the ceramic heater 20. Composed.

  The ceramic heater 20 is formed by forming a resistor pattern 20b on a heat-resistant substrate 20a such as alumina by printing, for example, and covering the surface with a glass layer 20c. The conveyance direction of the recording material P (the direction of arrow B) ), Which is long in the left-right direction perpendicular to (), that is, longer than the width of the recording material P. The ceramic heater 20 is supported by a heater guide (also referred to as a heater holder) 22 attached to the apparatus main body M. The heater guide 22 is a member formed in a semi-cylindrical shape with heat-resistant resin, and supports the fixing film 25 and also functions as a guide member for guiding the rotation thereof.

  The fixing film 25 is formed by forming a heat-resistant resin such as polyimide in a cylindrical film shape, and is loosely fitted to the ceramic heater 20 and the heater guide 22 described above. The fixing film 25 is pressed against the ceramic heater 20 by a later-described pressure roller 26, so that the back surface of the fixing film 25 is brought into contact with the lower surface of the ceramic heater 20. The fixing film 25 is configured to rotate in the direction of the arrow R25 as the recording material P is conveyed in the direction of the arrow B by the rotation of the pressure roller 26 in the direction of the arrow R26. The left and right end portions of the fixing film 25 are regulated by guide portions (not shown) of the heater guide 22 so that they do not shift in the longitudinal direction of the ceramic heater 20. Further, grease is applied to the inner surface of the fixing film 25 in order to reduce sliding resistance between the ceramic heater 20 and the heater guide 22.

  The pressure roller 26 is provided with a heat-resistant release layer 26b having elasticity such as silicone rubber on the outer peripheral surface of a metal cored bar 26a. The fixing film is formed from below by the outer peripheral surface of the release layer 26b. 25 is pressed against the ceramic heater 20 to form a fixing nip portion N with the fixing film 25. The width (nip width) in the fixing nip portion N in the rotation direction of the pressure roller 26 is defined as a. The nip width a is set to such an extent that the toner on the recording material P can be suitably heated and pressurized.

  As described above, the fixing device 8 heats the toner on the recording material P by the ceramic heater 20 while nipping and conveying the recording material P at the fixing nip portion N by the rotation of the pressure roller 26 in the direction of arrow R26. At this time, the temperature of the ceramic heater 20 can be appropriately controlled by the temperature control means.

  FIG. 3 shows a schematic hardware configuration of the image forming apparatus according to the present embodiment. In this figure, the main control unit 200 includes the main body CPU 9a and the fixing CPU 9b described above, and image code data received from an external device (not shown) such as a host computer via the communication unit 220 is necessary for printing by the printer. The data is expanded into bit data, internal information of the printer is displayed on the display panel 212 of the operation unit 210, a user instruction is received from the input key 211, and the operation of each unit of the printer is controlled. The main control unit 200 is connected to the following units. The sheet conveyance control unit 102 is a part that controls driving and stopping of a drive system such as a motor and a clutch for conveying a sheet in accordance with an instruction from the main control unit 200. The high voltage control unit 103 is a part that performs output control of each high voltage for charging, development, and transfer in accordance with an instruction from the main control unit 200. The optical system control unit 104 is a part that drives / stops the scanner motor and blinks the laser based on an instruction from the main control unit 200. The sensor input unit 105 includes a known registration sensor, a paper discharge sensor, and the like, and is a part for inputting sensor output information to the main control unit 200. The fixing device temperature control unit 106 is a part for adjusting the temperature of the fixing device to a temperature designated by the main control unit 200. The counter 10 is as described above.

  FIG. 4 is a graph showing the relationship between the change in pressure roller hardness and the nip width as the number of sheets pass. The vertical axis indicates the pressure roller hardness (°) on the left side, the nip width (mm) on the right side, and the horizontal axis indicates the number of sheets (10,000). From this figure, it can be seen that as the number of sheets passed increases, the hardness of the pressure roller decreases and the nip width increases.

  Next, the detailed operation of the printer in this embodiment will be described based on the flowchart of FIG.

  When the printer receives a print signal from a host computer (not shown) (S21), the fixing CPU 9b first checks the fixing temperature control mode designated by the user (S22). Next, based on the value of the counter 10, the number of sheets passing through the fixing device is confirmed (S 23), and it is determined whether it is equal to or greater than the first set value (here, 50,000 sheets) (S 24). If it is equal to or less than the first set value, the fixing CPU 9b determines the final target temperature adjustment temperature (control parameter) at the temperature in the fixing temperature adjustment mode designated by the user (S26) (S29). For example, when the user selects plain paper, 190 ° C. is set as the target temperature adjustment temperature.

  If the value of the counter 10 is 50,000 (sheets) or more, the number of sheets to be passed is compared with a second set value (here, 100,000 sheets) (S25). When the number of sheets to be passed is within the range of 50,000 to 100,000, the fixing CPU 9b adds “−10 ° C.” to the temperature of the fixing temperature adjustment mode designated by the user (S27), and after the correction The temperature is determined as the final target temperature control temperature (S29). For example, when the user selects plain paper for adjusting the fixing temperature and the value of the counter 10 exceeds 50,000 (sheets), the final temperature adjustment temperature is 190 ° C.−10 ° C. = 180 ° C.

  Further, when the value of the counter 10 is 100,000 (sheets) or more, a correction of “−15 ° C.” is added to the temperature of the fixing temperature adjustment mode designated by the user (S28), and the corrected temperature is finally set. The target temperature control temperature is determined (S29). For example, when the user selects plain paper for adjusting the fixing temperature and the value of the counter 10 exceeds 100,000 (sheets), the final temperature adjustment temperature is 190 ° C.−15 ° C. = 175 ° C.

  When the final temperature control temperature for fixing is determined, the printing operation is started (S30). After the printing operation is finished, the recording material P is discharged out of the apparatus and the printing is finished (S31).

  In this embodiment, the counter value (number of sheets to be passed) for switching the target temperature control temperature is set in two stages of 50,000 sheets and 100,000 sheets, and the temperature to be corrected is set to −10 ° C. and −15 ° C. Although set, the values of the number of sheets to be passed and the temperature value are not limited to these, and the number of stages may be set larger. Further, although not shown, it is possible to correct the fixing target temperature adjustment temperature according to the value of the counter and the value of the temperature detection sensor in combination with the temperature detection sensor for detecting the in-machine temperature. For example, when the in-machine temperature is higher than a predetermined temperature, correction is performed such that the fixing target temperature adjustment temperature is further lowered by a predetermined value.

  According to this embodiment, it is possible to extend the life of the fixing device. For example, in this embodiment, the life of a specific fixing device was 150,000 sheets, but it was possible to extend the life of the fixing device to 170,000 sheets. In addition, it is possible to maintain a good state without any offset or slip that is likely to occur at the end of the device life. Further, a fixing heating member (ceramic heater in the present embodiment) that requires a relatively large amount of power by lowering the fixing temperature adjustment temperature in accordance with the expansion of the nip width due to the decrease in pressure roller hardness over time. Since the energization time can be shortened, the power consumption can be reduced.

(Second Embodiment)
FIG. 6 shows a schematic configuration of an image forming apparatus including the fixing device according to the second embodiment of the present invention. In this embodiment, a laser beam printer will be described as an example. The overall configuration of this laser beam printer and the configuration of the fixing device are the same as those in the first embodiment, and the duplicate description of the same parts is omitted. The difference from the first embodiment is that, in the operation, “fixing film rotational speed” is used instead of “counter value” as information for detecting the degree of aging of the fixing device. Accordingly, as can be seen by comparing FIG. 6 with FIG. 1, the counter 10 in the first embodiment is not required in the second embodiment. Further, as can be seen from the comparison of FIG. 7 showing the configuration of the fixing device in the second embodiment with FIG. 2, in the second embodiment, a rotation detection sensor 30 for detecting the rotation of the fixing film 25 is provided. Yes. (However, also in the first embodiment, a rotation detection sensor 30 may be provided for controlling the rotation speed of the fixing film 25.)

  As shown in FIG. 7, the fixing rotation control means in this embodiment includes a rotation detection sensor 30 that detects the number of rotations of the fixing film 25, a motor 29 that rotationally drives the pressure roller 26, and the rotation of the motor 29. And a fixing CPU 9b that counts the number of rotations of the fixing film 25, and controls the rotation of a motor 29 that rotationally drives the pressure roller 26 so that the number of rotations of the fixing film 25 per unit time is constant. As a result, even if the pressure roller 26 expands due to heating, the rotation of the pressure roller 26 is controlled so that the rotation speed of the fixing film 25 is constant. Absent. Note that a predetermined marking (for example, white marking) (not shown) is provided at the end of the fixing film 25 so that rotation can be detected. The rotation detection sensor 30 is an optical sensor that identifies this marking. Can be configured.

  The temperature control means includes a thermistor 21 attached to the back surface of the ceramic heater 20, and a fixing CPU 9 b that controls the triac 24 based on the temperature detected by the thermistor 21 and controls the energization of the ceramic heater 20.

  As described above, the fixing device 8 heats the toner on the recording material P by the ceramic heater 20 while nipping and conveying the recording material P at the fixing nip portion N by the rotation of the pressure roller 26 in the arrow direction R26.

  Next, the operation of the second embodiment will be described based on the flowchart of FIG.

  When the printer receives a print signal from a host computer (not shown) (S41), the fixing CPU 9b first checks the fixing temperature control mode designated by the user (S42). Next, the fixing film rotational speed data stored in the fixing CPU 9b is confirmed (S43), and it is determined whether or not it is equal to or more than the first set value (here, 150,000 rotations) (S44). If the value is equal to or smaller than the first set value, the fixing CPU 9b uses the temperature adjustment temperature designated by the user as it is (S46), and determines this as the final target temperature adjustment temperature (S49).

  When the value of the fixing film rotation number is equal to or larger than the first set value, the value of the fixing film rotation number is compared with the second setting value (300,000 here) (S45). When the value of the fixing film rotation number is in the range of 150,000 to 300,000 (rotation), the fixing CPU 9b adds “−10 ° C.” to the fixing temperature adjustment temperature designated by the user (S47). The final target temperature adjustment temperature is determined from the corrected temperature (S49). For example, when the user selects plain paper for adjusting the fixing temperature and the counter value exceeds 50,000 (rotation), the final temperature adjustment temperature is 190 ° C.−10 ° C. = 180 ° C.

  Further, when the value of the rotation speed of the fixing film is 300,000 (rotations) or more, a correction of “−15 ° C.” is added to the target temperature adjustment temperature (S48), and the temperature after this correction is set as the final target temperature adjustment temperature. Determine (S49).

  When the final temperature control temperature for fixing is determined, the printing operation is started (S50). After the printing operation is finished, the recording material P is discharged out of the apparatus and the printing is finished (S51).

  In this embodiment, the fixing film rotation number for switching the target temperature adjustment temperature is set in two stages of 150,000 rotations and 300,000 rotations, and the temperature to be corrected is set to −10 ° C. and −15 ° C. The numerical values and the number of steps are not limited to these. Further, in combination with a temperature detection sensor not included in the present embodiment, it is possible to correct the fixing target temperature adjustment temperature according to the value of the fixing film rotation speed and the value of the temperature detection sensor. For example, when the in-machine temperature is higher than a predetermined temperature, correction is performed such that the fixing target temperature adjustment temperature is further lowered by a predetermined value.

  According to this embodiment, it is possible to extend the life of the fixing device. For example, in the present embodiment, the life of a specific fixing device was 150,000 sheets, but it was possible to extend the life of the fixing device to 180,000 sheets. In this embodiment, since the number of rotations of the fixing film is detected, it is possible to accurately detect and detect a decrease in the hardness of the pressure roller, thereby extending the life by 10,000 sheets compared to the first embodiment. It is thought that it became.

  According to the present embodiment, it is possible to maintain an excellent state without any offset or slip that is likely to occur at the end of the device life. Further, a fixing heating member (ceramic heater in the present embodiment) that requires a relatively large amount of power by lowering the fixing temperature adjustment temperature in accordance with the expansion of the nip width due to the decrease in pressure roller hardness over time. Since the energization time can be shortened, the power consumption can be reduced.

1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus including a fixing device according to a first embodiment of the present invention. FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of an example of a fixing device used in the printer illustrated in FIG. 1. 1 is a block diagram illustrating a schematic hardware configuration of an image forming apparatus according to an embodiment of the present invention. 6 is a graph showing the relationship between the change in pressure roller hardness and the nip width with the number of sheets passing in the embodiment of the present invention. 3 is a flowchart illustrating detailed operation of the printer according to the first embodiment of the present invention. 6 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus including a fixing device according to a second embodiment of the present invention. FIG. It is a longitudinal cross-sectional view which shows schematic structure of an example of the fixing device used for the printer shown in FIG. 6 is a flowchart illustrating detailed operation of a printer according to a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging roller, 3 ... Laser scanner, 4 ... Developing device, 4a ... Developing sleeve, 5 ... Transfer roller, 6 ... Cleaning device, 6a ... Cleaning blade, 7 ... Paper feed cassette, 8 ... Fixing device , 9 ... Control board, 9a ... Main body CPU, 9b ... Fixing CPU, 10 ... Counter, 20 ... Ceramic heater, 20a ... Alumina substrate, 20b ... Resistor pattern, 20c ... Glass layer, 21 ... Thermistor, 22 ... Heater guide 24 ... Triac, 25 ... Fixing film, 26 ... Pressure roller, 26a ... Core, 26b ... Releasing layer including elastic layer, 29 ... Motor, 30 ... Fixing film rotation detection sensor, M ... Device body, P ... Recording material

Claims (7)

In an image forming apparatus having a fixing device for fixing a developer image on a recording material,
Aging detection means for detecting the degree of aging of the fixing device;
Control means for changing a control parameter of the fixing device in accordance with a detection result of the aging detection means of the fixing device;
An image forming apparatus comprising:   The aging change detecting means includes a sheet passing number detecting means for detecting a sheet passing number for the fixing device, and detects the degree of the aging change based on the detected sheet passing number. The image forming apparatus according to 1.   In the fixing device, a pair of fixing rotators are brought into contact with each other to form a fixing nip portion, and a recording material carrying an unfixed developer image is nipped and conveyed by the fixing nip portion, while being placed on the recording material. The secular change detecting means includes a rotation detecting means for detecting the rotation of the fixing rotating body, and detects the degree of the secular change based on the detected number of rotations. The image forming apparatus according to claim 1.   4. The image forming apparatus according to claim 3, wherein one of the pair of fixing rotators is a cylindrical film member.   The image forming apparatus according to claim 1, wherein the control unit changes control parameters of the fixing device step by step each time the degree of aging of the fixing device reaches a predetermined value.   6. The fixing device according to claim 1, wherein the fixing device includes a heating member for fixing an unfixed image, and the control parameter of the control unit is a target temperature adjustment temperature of the heating member. Image forming apparatus.   The fixing device has a heating member for fixing an unfixed image, and the control means decreases the target temperature adjustment temperature value of the fixing device as the degree of aging increases. The fixing device according to claim 6.