JP2019120787A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can achieve both prevention of the occurrence of an abnormal sound due to self-excited vibration of a nip forming member, and prevention of an excessive increase in temperature of a fixing member.SOLUTION: A fixing device of the present invention can execute excessive temperature increase prevention rotation for rotating a fixing member without heating when a temperature detected by temperature detection means reaches a predetermined temperature after completion of fixing, comprises usage history acquisition means that acquires the usage history of the device, and changes at least one of the start time and duration time of the excessive temperature increase prevention rotation on the basis of the usage history. When the usage history exceeds a first prescribed value, the fixing device returns both the start time and duration time of the excessive temperature increase prevention rotation to default values. The fixing device can thus achieve both prevention of the occurrence of an abnormal sound due to self-excited vibration of a nip forming member, and prevention of an excessive increase in temperature of the fixing member.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In recent years, market demands for energy saving and speeding up of image forming apparatuses such as printers, copiers and facsimiles have become strong. In the above image forming apparatus, a toner image (unfixed toner image) formed by an image forming process such as electrophotographic recording, electrostatic recording, magnetic recording, etc. is directly or through an intermediate transfer member, recording material sheet, printing paper, photosensitive Transfer to a recording material such as paper or electrostatic recording paper. Then, the recording material carrying the toner image is passed through a fixing device to fix the toner image on the recording material.

  As a fixing device, a fixing device of a contact heating method such as a heat roller method, a film heating method, or an electromagnetic induction heating method is widely adopted. For example, in a configuration using an endless belt, Patent Document 1 proposes a fixing device capable of warming the entire belt and shortening the first print time from the heating standby time. This fixing device responds to the recent demand for reduction in power consumption (energy saving) and shortening of warm-up time (speeding up) by reducing the heat capacity of fixing members such as a fixing belt and a fixing film.

  In the case of such a low heat capacity configuration, the temperature is apt to fluctuate due to the characteristic of being easy to heat and cool, and the temperature of the fixing member is abnormally raised with respect to the target control temperature, that is, overshoot tends to occur. Become. If this overshoot occurs, the temperature of the fixing member becomes high, which may cause deterioration or damage. Further, since the temperature of the fixing member is not stable with respect to the target control temperature, the image quality after fixing may not be stable.

  To address these problems, Patent Document 2 includes a rotation time change control circuit that changes the power supply off rotation time for turning the fixing member off by turning off the power supply to the fixing heat source after the printing operation is completed. The control circuit discloses a fixing device that changes the power supply OFF rotation time according to the condition at the time of printing operation.

  This fixing device can prevent deterioration and damage of the fixing member as a result by suppressing the overshoot. Further, by stabilizing the temperature, it is possible to stabilize the image quality after fixing.

  An object of the present invention is to provide a fixing device capable of achieving both prevention of abnormal noise generation due to self-excited vibration of the nip forming member and prevention of excessive temperature rise of the fixing member.

  The above problems are provided by a rotatable fixing member heated by a heat source, a pressure member provided on the outer side of the fixing member and facing the fixing member, and an inner side of the fixing member, and the fixing member and the fixing member. A nip forming member for forming a fixing nip with the pressure member, a lubricant interposed between the inner circumferential surface of the fixing member and the nip forming member, and at least one of the fixing member and the pressure member A temperature detection means for detecting a temperature is provided, and after fixing is completed, when the temperature detected by the temperature detection means reaches a predetermined temperature, it is possible to carry out the excessive temperature rise prevention rotation for rotating the fixing member without heating In the fixing device, there is provided use history acquisition means for acquiring a use history of the apparatus, and changing at least one of the start temperature and the duration of the excessive temperature rise preventing rotation based on the use history, and If the history exceeds a first predetermined value, it is solved by the fixing device and returning to the initial set value neither the starting temperature and duration of the excessive temperature rise preventing rotation.

  The fixing device of the present invention changes at least one of the start temperature and the duration of the overheat prevention rotation based on the use history. In addition, when the usage history exceeds the first specified value, both the start temperature and the duration time of the excessive temperature rise prevention rotation are returned to the initial set values. Therefore, it is possible to simultaneously prevent the generation of abnormal noise due to the self-excited vibration of the nip forming member and the prevention of excessive temperature rise of the fixing member.

FIG. 1 is a schematic cross-sectional view showing an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing a fixing device according to an embodiment of the present invention. It is a graph (single condition) which shows the conditions which prescribe the setting value of rotation-examination prevention rotation concerning one embodiment of the present invention. It is a figure which shows the setting value prescribed | regulated by conditions I-III. It is a graph (compound condition) which shows the conditions which prescribe the setting value of rotation-examination prevention rotation concerning another embodiment of the present invention.

  Hereinafter, before describing the embodiments, preliminary matters for facilitating the understanding of the embodiments will be described.

  In a fixing device using an endless belt as described in Patent Document 1, the nip portion has a sliding configuration. Therefore, a lubricant is applied to the nip portion so that the fixing device has sufficient durability. However, when this lubricant is in the mixed lubrication area (unstable lubrication state in which fluid lubrication and solid lubrication are mixed), noise may be generated due to self-excited vibration of the nip portion.

  This abnormal noise is (1) beginning to move (at the start of rotation), (2) the viscosity of the lubricant is low (ie, high temperature), (3) the sliding speed is slow (the rotational speed is slow), (4) It is known from past findings that it is likely to occur when the four factors of high pressure are satisfied.

  Patent Document 2 described above describes a method for preventing the temperature rise of the fixing member by rotating the fixing member without heating after completion of printing. When the non-heating rotation (hereinafter, referred to as excessive temperature rise preventing rotation (non-heating rotation)) is performed, if the above four factors are satisfied, noise due to self-excited vibration of the nip portion is generated.

  Also, looking at the change with time of the fixing device, the lubricant is abundant at the early stage of use (new), and the lubricant is exhausted at the later stage of use (close to the product life). Is suppressed. However, the lubricant is in an incompletely reduced state (mixed lubrication region) from the early stage of use to the late stage, and noise due to self-oscillation tends to occur.

  From the viewpoint of protection of the fixing member, it is useful to carry out the overheat protection rotation. Therefore, it is desirable to prevent abnormal noise generated by the overheat protection rotation for the entire use period of the fixing device.

  In the following embodiments, a fixing device capable of achieving both prevention of abnormal noise generation due to self-excited vibration of the nip forming member and prevention of excessive temperature rise of the fixing member will be described.

First Embodiment
FIG. 1 is a schematic sectional view showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is a tandem color laser printer, and four image forming units 4Y, 4M, 4C, and 4K are provided at the center of the apparatus main body. The image forming units 4Y, 4M, 4C and 4K contain developers of different colors of yellow (Y), magenta (M), cyan (C) and black (K) corresponding to color separation components of a color image. It has the same configuration except for

  Specifically, each of the image forming units 4Y, 4M, 4C, and 4K includes a drum-shaped photosensitive member 5 as a latent image carrier, a charging device 6 for charging the surface of the photosensitive member 5, and the photosensitive member 5. The developing device 7 for supplying toner to the surface, and the cleaning device 8 for cleaning the surface of the photosensitive member 5 are provided. In FIG. 1, the photosensitive member 5, the charging device 6, the developing device 7, and the cleaning device 8 are designated by reference numerals only for the black imaging unit 4 K, and the reference numerals are omitted for the other imaging units 4 Y, 4 M, and 4 C. doing.

  Under the image forming units 4Y, 4M, 4C, and 4K, an exposure device 9 for exposing the surface of the photosensitive member 5 is disposed. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photosensitive member 5 with a laser beam based on image data.

  The transfer device 3 is disposed above the image forming units 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, and a secondary transfer backup roller 32. . The transfer device 3 further includes a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35.

  The intermediate transfer belt 30 is an endless belt, and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, when the secondary transfer backup roller 32 is rotationally driven, the intermediate transfer belt 30 travels (rotates) in the direction indicated by the arrow in the drawing.

  The four primary transfer rollers 31 respectively sandwich the intermediate transfer belt 30 with the respective photosensitive members 5 to form a primary transfer nip. Further, a power supply is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) and / or an alternating voltage (AC) is applied to each primary transfer roller 31.

  The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Further, as in the case of the primary transfer roller 31, a power supply is connected to the secondary transfer roller 36 so that a predetermined DC voltage (DC) and / or an AC voltage (AC) is applied to the secondary transfer roller 36. It has become.

  In the upper part of the printer main body, a bottle storage portion 2 is provided, and four toner bottles 2Y, 2M, 2C, 2K containing toner for replenishment are detachably mounted in the bottle storage portion 2. A supply passage (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each developing device 7 is provided with each toner bottle 2Y, 2M, 2C, 2K through this supply passage. Toner is replenished.

  On the other hand, at the lower portion of the printer main body, a paper feed tray 10 accommodating paper P as a recording medium, a paper feed roller 11 for discharging the paper P from the paper feed tray 10 and the like are provided. Here, the concept of the recording medium includes, in addition to plain paper, thick paper, postcard, envelope, thin paper, coated paper (such as coated paper and art paper), tracing paper, OHP sheet, and the like. Although not shown, a manual sheet feeding mechanism may be provided.

  In the printer main body, a conveyance path R for discharging the sheet P from the sheet feed tray 10 through the secondary transfer nip and out of the apparatus is disposed. In the conveyance path R, on the upstream side of the secondary transfer roller 36 in the sheet conveyance direction, a pair of registration rollers 12 as conveyance means for conveying the sheet P to the secondary transfer nip is disposed.

  Further, on the downstream side of the secondary transfer roller 36 in the sheet conveyance direction, a fixing device 20 for fixing the unfixed image transferred to the sheet P is disposed. Further, on the downstream side of the fixing device 20 in the sheet conveyance direction of the conveyance path R, a pair of sheet discharge rollers 13 for discharging the sheet P to the outside of the apparatus is provided. Further, a sheet discharge tray 14 for stocking the sheet P discharged to the outside of the apparatus is provided on the upper surface portion of the printer main body.

  Subsequently, the basic operation of the printer according to the present embodiment will be described. When the image forming operation is started, each photosensitive member 5 in each of the image forming units 4Y, 4M, 4C, 4K is rotationally driven clockwise by a driving device (not shown), and the surface of each photosensitive member 5 is charged. Is uniformly charged to a predetermined polarity. Laser light is irradiated from the exposure device 9 on the surface of each charged photosensitive member 5 to form an electrostatic latent image on the surface of each photosensitive member 5. At this time, the image information to be exposed on each photosensitive member 5 is monochrome image information obtained by decomposing a desired full color image into yellow, magenta, cyan and black color information. Thus, the electrostatic latent image is visualized (visualized) as a toner image by supplying toner to each electrostatic latent image formed on each photosensitive member 5 by each developing device 7 .

  Further, when the image forming operation is started, the secondary transfer backup roller 32 is rotationally driven counterclockwise in the figure to cause the intermediate transfer belt 30 to run in the direction shown by the arrow in the figure. Then, a constant voltage or a constant current controlled voltage having a reverse polarity to the charging polarity of the toner is applied to each primary transfer roller 31. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

  Thereafter, when the toner image of each color on the photosensitive member 5 reaches the primary transfer nip as the photosensitive member 5 rotates, the toner image on each photosensitive member 5 is generated by the transfer electric field formed in the primary transfer nip. Are sequentially superimposed and transferred onto the intermediate transfer belt 30. Thus, a full color toner image is carried on the surface of the intermediate transfer belt 30. Further, the toner on each photosensitive member 5 which has not been transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Thereafter, the surface of each photosensitive member 5 is neutralized by the static elimination device, and the surface potential is initialized.

  At the lower part of the image forming apparatus 1, the sheet feeding roller 11 starts rotational driving, and the sheet P is fed out from the sheet feeding tray 10 to the conveyance path R. The sheet P fed to the conveyance path R is timed by the registration roller 12 and is sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to that of the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, whereby a transfer electric field is formed in the secondary transfer nip. .

  Thereafter, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 circulates, the transfer electric field formed in the secondary transfer nip causes the toner image on the intermediate transfer belt 30 to The toner images on the sheet P are collectively transferred onto the sheet P. At this time, the residual toner on the intermediate transfer belt 30 which has not been transferred to the sheet P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the sheet P is conveyed to the fixing device 20, and the toner image on the sheet P is fixed to the sheet P by the fixing device 20. Then, the sheet P is discharged to the outside of the apparatus by the sheet discharge roller 13 and is stocked on the sheet discharge tray 14.

  The above description is an image forming operation when forming a full color image on a sheet. In addition to this, one of the four image forming units 4Y, 4M, 4C, 4K may be used to form a monochromatic image, or two or three image forming units may be used to perform two colors or three colors. It is also possible to form a color image.

  FIG. 2 is a schematic sectional view showing a fixing device according to an embodiment of the present invention. The fixing device 20 includes a fixing belt 21 which is a rotatable fixing member, and a halogen heater 22 which is provided inside the fixing belt 21 and which heats the fixing belt 21 and which is provided outside the fixing belt 21. And a pressure roller 23, which is a pressure member facing the belt 21.

  The fixing device 20 is provided inside the fixing belt 21 and provided at both ends in the longitudinal direction of the fixing belt 21 and a nip forming member 24 forming the fixing nip N between the fixing belt 21 and the pressure roller 23. And a holding member 25 for guiding the rotation of the fixing belt 21.

  The fixing belt 21 may be configured to be protected by the belt protection member 26 in a portion where the fixing nip N is not formed. Further, the above components except the pressure roller 23 are included in the pair of holding members 25. The holding member 25 also functions as a guide unit for guiding the fixing belt 21.

  An area where the fixing belt 21 is directly heated by the halogen heater 22 emitting light is controlled by the light shielding member 27. The shape of the light shielding member 27 is, for example, a stepped shape in which a light shielding area is provided in accordance with the width of the recording paper to be passed, and rotates in a noncontact manner along the inside of the fixing belt 21. Placed and pivoted to shield areas not needed for heating.

  The fixing belt 21 is an endless belt (or film) using a metal belt such as nickel or SUS, or a resin material such as polyimide. A release layer such as a PFA layer or a PTFE layer is provided on the surface layer of the belt, and has a release property so that the toner does not adhere.

  It is desirable to provide an elastic layer formed of a silicone rubber layer or the like between the base material of the belt (or film) and the releasing layer. When the silicone rubber layer is not provided, the heat capacity is reduced and the fixability is improved. However, when the unfixed image is crushed and fixed, the minute unevenness on the belt surface may be transferred to the image, and the uneven glossiness (yuzu skin image) may be left on the solid portion of the image.

  Therefore, it is desirable to provide the silicone rubber layer with a thickness of 100 (μm) or more, and the fine unevenness can be absorbed by the deformation of the silicone rubber layer to improve the dull skin image.

  In the pressure roller 23, an elastic rubber layer 23b is provided on a cored bar 23a, and a release layer (PFA or PTFE layer) for obtaining releasability is provided on the surface of the elastic rubber layer 23b. The pressure roller 23 is rotated by transmitting a driving force from a driving source such as a motor provided in the image forming apparatus 1 through a gear. The pressure roller 23 is pressed against the fixing belt 21 by a spring or the like, and the elastic rubber layer 23 b is crushed and deformed to generate a predetermined nip width.

  The pressure roller 23 may be a hollow roller, and may have a heat source such as a halogen heater inside the hollow. The elastic rubber layer 23 b may be solid rubber, but if there is no heat source inside the pressure roller 23, sponge rubber may be used. Sponge rubber is more desirable because it has high thermal insulation and the heat of fixing belt 21 is less likely to be taken away.

  Although the halogen heater 22 as a heat source is shown by FIG. 2, it may replace with this and may use an induction heating apparatus (IH), a resistance heating element, or a carbon heater.

  The fixing nip N of the nip forming member 24 has a flat shape, but is not limited to this, and may have a concave shape or another shape. For example, when the shape of the fixing nip N is a concave shape, the discharge direction of the leading end of the recording material is closer to the pressure roller 23, and the separability is improved. Therefore, there is an effect that the occurrence of jamming is suppressed.

  In addition, a sliding sheet, which is a sliding member, may be wound around the surface of the nip forming member 24 so as to slide on the inner surface of the fixing belt 21. Alternatively, the nip forming member 24 may slide directly on the inner surface of the fixing belt 21. A lubricant is interposed between the inner circumferential surface of the fixing belt 21 and the nip forming member 24 (sliding surface).

  Inside the fixing belt 21, a stay 28 which is a support member for supporting the fixing nip N is provided. The stay 28 prevents deflection of the nip forming member 24 that is subjected to pressure by the pressure roller 23, so that it is possible to obtain a uniform nip width in the axial direction. Both ends of the stay 28 are held by the holding member 25 and positioned.

  A reflective member 29 is provided between the halogen heater 22 and the stay 28. The reflection member 29 reflects radiant heat and the like from the halogen heater 22 and suppresses wasteful energy consumption due to the stay 28 being heated. The same effect can be obtained even if the surface of the stay 28 is heat-insulated or mirror-polished instead of including the reflection member 29.

  The fixing device 20 further includes usage history acquisition means 37 for acquiring at least one of the number of sheets, the traveling distance of the fixing member, the number of jobs input, and the rotational torque of the device as the value of usage history. In addition, a temperature detection unit 38 that detects the temperature of at least one of the fixing belt 21 and the pressure roller 23 is provided.

  The use history acquisition means 37 can be provided in either the fixing device 20 or the image forming apparatus 1, but is more preferably provided in the image forming apparatus 1 side. This is because it is unnecessary to perform processing for discarding or reusing at the time of replacement of the fixing device 20 and cost.

  Further, it is preferable that the temperature detection means 38 be disposed in the area where the fixing belt 21 is locally heated by the residual heat, ie, the area where the temperature is the closest to the halogen heater 22 and the temperature is the highest.

  In the fixing device 20 having such a configuration, the pressure roller 23 is rotated by the driving source, and the driving force is transmitted to the fixing belt 21 at the fixing nip N, whereby the fixing belt 21 is also rotated. The fixing belt 21 is nipped and rotated by the fixing nip N, and is guided by the holding members 25 at both ends except for the fixing nip N and travels.

  With the above-described configuration, it is possible to realize a fixing device that is inexpensive and has a fast warm-up.

  Next, the subject of the present invention will be described in detail.

(Generation of noise due to self-oscillation)
In the fixing device 20 shown in FIG. 2 described above, the fixing belt 21 rotates in response to the driving force of the pressure roller 23. That is, the inner circumferential surface of the fixing belt 21 and the nip forming member 24 slide. Therefore, the surface of the nip forming member 24 is covered with a sheet material having a low coefficient of friction, the lubricant is applied to the sheet material, or the lubricant is directly applied to the inner peripheral surface of the fixing belt 21. The coefficient of friction with the peripheral surface is lowered.

  By using a lubricant, the lubrication state of the sliding portion is roughly classified into three from the initial use (new) to the late use (temporary goods).

(1) Initial use (new): It is an ideal lubrication state (fluid lubrication area) in which the lubricant is abundant in the sliding portion and the sliding surfaces are completely separated by the oil film.
(2) From the beginning of use to the end of use: Lubricant is decreasing, the oil film is thin, and the contact between convex parts on the sliding surface is locally in a lubrication state (mixed lubrication area) .
(3) Late use period (temporary product): Lubricant is exhausted, and it is in a lubricated state (solid lubrication region) in which contact between the convex portions on the sliding surface occurs.

  In the mixed lubrication area of (2), it is known that abnormal noise is likely to be generated due to the sliding between the inner surface of the fixing belt 21 and the nip forming member 24. Since the frequency of this abnormal noise almost coincides with the natural frequency of the nip forming member 24, it is considered that the nip forming member 24 self-excites and generates abnormal noise.

  Further, the abnormal noise is likely to occur when the linear velocity (rotational velocity) of the fixing device 20 is low, the lubricant is at a high temperature (that is, the viscosity of the lubricant is low), and the pressure on the sliding surface is high. Since it tends to occur when the rotational speed is low, the movement start (transition period from the start of rotation to reaching a constant linear velocity) is also likely to occur.

(Over temperature rise prevention rotation)
Next, the excessive temperature rise prevention rotation will be described. When the fixing operation of the fixing device is completed and the rotation of the fixing member (such as the fixing belt 21) is stopped, the temperature of the fixing member (particularly, in the vicinity of the heat source) may increase excessively due to the remaining heat of the heat source. Excessive temperature rise after the completion of fixing causes the fixing member to be thermally deformed, and in some cases, the thermally deformed portion becomes plastic deformation (kink). When the kink portion is pressurized by the pressing member in the subsequent fixing operation, strong repeated stress is generated, and the fixing member may be finally broken.

  In order to prevent this, it is effective to rotate the fixing member without heating when the temperature of the fixing member rises excessively due to the residual heat of the heat source to equalize the temperature of the fixing member ).

  However, as described above, the excessive temperature rise prevention rotation may cause abnormal noise due to self-excited vibration. Therefore, it is desirable that a fixing device that does not generate abnormal noise due to self-excited vibration of the nip forming member 24 while preventing excessive temperature rise of the fixing member.

  From these considerations, when the lubricated state of the sliding portion is in the mixed lubrication region (during the in-use period to the in-use period), the overheat prevention rotation is started while the lubricant is not at a high temperature, and If the number of rotations is reduced, abnormal noise can be suppressed.

  In the present embodiment, therefore, at least one of the start temperature and the duration time of the excessive temperature rise prevention rotation is changed based on the usage history of the fixing device, thereby preventing abnormal noise generation due to self-excited vibration, and excessive increase of the fixing member. It is compatible with the prevention of temperature.

  FIG. 3 is a graph showing the relationship between the usage history (the number of sheets passed) and the conditions for defining the set value of the excessive temperature rise prevention rotation. In FIG. 3, the horizontal axis is the use history (the number of sheets passed), and indicates the ratio (%) of the (accumulated) number of sheets to the total number of sheets in the product life. In the present embodiment, the total sheet number in the product life of the fixing device is 300 K (sheets).

  Moreover, FIG. 4 is a figure which shows the setting value (The rotation start temperature and rotation continuation time of over temperature rise prevention rotation) prescribed | regulated by conditions I-III. For example, in the case of condition I, when the temperature of the fixing member is 180 ° C., the excessive temperature rise prevention rotation is continuously performed for 10 seconds. Conditions II, III are the same except for the onset temperature and duration.

  Condition I is also an initial set value (default value) of the rotation start temperature and the rotation continuation time.

  As shown in FIG. 3, up to 2% (= 6K) of the ratio of the number of sheets (number of sheets) is regarded as the initial use, and the condition I is maintained. At the initial stage of use, the lubricant is abundant (fluid lubrication state), and it is considered that abnormal noise hardly occurs, so the rotation start temperature is increased (180 ° C.), and the rotation duration is shortened (10 seconds). The reason why the rotation duration time is shortened is also to prevent the traveling distance of the fixing member from being extended (the fixing device is deteriorated) by the excessive temperature rise preventing rotation.

  When the ratio of the number of sheets (number of sheets) is 2% (= 6K) to 20% (= 60K), it is considered to be a so-called mixed lubrication area in which the lubricant is present at a halfway position. This period is changed to condition III because there is a high risk of noise. That is, the rotation start temperature is lowered (165 ° C.), and the rotation duration is increased (30 seconds).

  The rotation duration time is increased in order to prevent the occurrence of multiple overheat prevention rotations. In particular, it is considered that the fixing member is at a high temperature during continuous sheet feeding, and the temperature is not uniformed in a short rotation time. In that case, since the overheat prevention rotation is frequently performed, the risk of noise generation increases. Therefore, in the mixed lubrication region, the duration of one overheat prevention rotation is lengthened to prevent the occurrence of multiple overheat prevention rotations.

  In addition, when the rotation start temperature is lowered, it may be considered that the number of times of implementation of the excessive temperature rise prevention rotation is increased. Therefore, the rotation start temperature may be kept unchanged (180 ° C.), and the rotation duration may be increased (changed from 10 seconds to 30 seconds).

  After 20% (= 60K) of the percentage of the number of sheets passing (number of sheets passing), it is considered to be in the later stage of use. From this point on, lubricant depletion progresses and it can be said that it is in the solid lubrication region. In this region, the rotational torque of the fixing device itself is large but stable, so the condition I (initial set value) is changed. That is, when the usage history exceeds the predetermined value (the first predetermined value), both the start temperature and the duration time of the excessive temperature rise prevention rotation are returned to the initial set values. At the initial setting value, the frequency of the excessive temperature rise prevention rotation and its implementation time decrease (condition I), so it is possible to suppress an increase in the traveling distance of the fixing member, which is advantageous.

  As described above, in the present embodiment, in the fixing device capable of performing the excessive temperature rise prevention rotation, at least one of the start temperature of the rotation operation or the duration time of the rotation operation is changed based on the use history (the number of sheets). Then, when the usage history exceeds a predetermined specified value, both the start temperature of the rotation operation and the duration time of the rotation operation are returned to the initial set values. Thus, it is possible to simultaneously prevent the occurrence of abnormal noise due to the self-excited vibration of the nip forming member and the prevention of the excessive temperature rise of the fixing member.

  In the present embodiment, the number of sheets passed is used as the usage history, but the present invention is not limited to this. Whether or not the lubricant is in the mixed lubrication state may be estimated using at least one of travel distance, the number of input jobs, rotational torque of the apparatus, and accumulated use time as the use history.

  In addition, numerical values such as the rotation start temperature, the rotation continuation time, and the specified value are an example. These values can be appropriately changed according to the specification of the fixing device to which the present invention is applied, the type of lubricant, and the like.

Second Embodiment
In the first embodiment, only the number of sheets passed is used as the usage history. In the second embodiment, conditions I to III shown in FIG. 3 are selected based on the values of two parameters of the number of sheets passed and the travel distance as the usage history.

  FIG. 5 is a graph showing the relationship between the use history (the number of sheets passed and the travel distance) and the condition defining the set value of the excessive temperature rise prevention rotation. In FIG. 5, the horizontal axis is the use history (the number of sheets passed), and indicates the ratio (%) of the (accumulated) number of sheets to the total number of sheets in the product life. The vertical axis represents the traveling distance of the fixing member, and indicates the ratio (%) of the (accumulated) traveling distance to the total traveling distance at the product life.

  As shown in FIG. 5, before the ratio of the number of sheets (the number of sheets) reaches 2% (= 6K) and after the ratio of the number of sheets (the number of sheets) is 20% (= 60K), Condition I (initial set value) is selected because it is considered that no abnormal noise occurs. On the other hand, the period is divided by the number of sheets (%) and the traveling distance (%).

  Specifically, when the ratio of the number of sheets (number of sheets) is between 2% (= 6K) to 20% (= 60K), two sheets shown by Y = 1.7X and Y = 0.6X The area is divided by the broken line of.

  For example, the region below the broken line (Y = 0.6 ×) indicates that the travel distance (%) is small relative to the number of sheets (%). This means that the number of rotational operations other than the sheet passing is small, that is, the number of rotational operations due to the rise and return is smaller than that due to the sheet passing. This is an area where it is estimated that the continuous sheet passing is large, and the fixing device also tends to be high temperature. Therefore, since the viscosity of the lubricant is reduced, abnormal noise is also likely to occur. Therefore, in this region, the condition is changed to condition III, the rotation start temperature is lowered (165 ° C.), and the rotation duration is also extended (30 seconds).

  On the other hand, the area above the broken line (Y = 1.7X) is an area where it is estimated that the continuous sheet passing is small. Since it is estimated that the continuous paper passing is small, the unit does not easily become hot and abnormal noise hardly occurs. Therefore, the condition I is changed in this area.

  Then, the region above the broken line (Y = 0.6 × X) and below the broken line (Y = 1.7 ××) is between the condition I and the condition III, and the rotation start temperature is 170 ° C.), rotation duration (20 seconds) (condition II).

  As described above, in the present embodiment, since the number of sheets passed and the traveling distance are used as the usage history, the start temperature and / or the duration of the overheat prevention rotation can be changed more finely than in the first embodiment. .

  The usage history is not limited to the two usages of the number of sheets passed and the travel distance. At least two such as the number of sheets to be passed, the traveling distance, the number of input jobs, the rotational torque of the apparatus, and the cumulative use time may be used.

  Subsequently, advantageous configurations of the invention will be described.

  As shown in FIG. 3 or FIG. 5 above, the excessive temperature rise prevention rotation is performed until the usage history reaches the initial specified value (here, it is called 2 (%) sheet number, the second specified value). It is desirable not to change any of the start temperature and the duration time from the initial set value (condition I). This is because in the initial stage of use (new product), the lubricant is abundant, so abnormal noise is less likely to occur.

  Moreover, it is desirable not to change the start temperature and the duration of the excessive temperature rise prevention rotation until the excessive temperature rise prevention rotation is completed. For example, assuming that the travel distance is used as the usage history, even if the travel distance exceeds the specified value during the implementation of the over temperature rise prevention rotation, the conditions are not changed until the over temperature rise prevention rotation is completed. After the excessive temperature rise prevention rotation is completed, the implementation condition of the excessive temperature rise prevention rotation is changed.

  Furthermore, it is desirable that the user can arbitrarily change the start temperature, duration, and use history value of the overheat prevention rotation based on the use history. For example, the user may be able to change the start temperature and duration of the excessive temperature rise prevention rotation by using a fixing device or an external input device of the image forming apparatus. By making these parameters changeable in consideration of the use condition of the device, variations, etc., it is possible to change the conditions suitable for the device of the user.

  The foregoing has described preferred embodiments and advantageous configurations of the present invention. The present invention is not limited to the specific embodiment, and various modifications and changes may be made within the scope of the spirit of the present invention described in the claims unless particularly limited in the above description. It is possible.

  Further, the effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects according to the present invention are not limited to those described in the embodiments of the present invention.

Reference Signs List 1 image forming apparatus 2 bottle storage unit 2Y, 2M, 2C, 2K toner bottle 3 transfer device 4Y, 4M, 4C, 4K image forming unit 5 photoconductor 6 charging device 7 developing device 8 cleaning device 9 exposure device 10 paper feeding tray 11 Sheet feed roller 12 registration roller 13 sheet discharge roller 14 sheet discharge tray 20 fixing device 21 fixing belt 22 halogen heater 23 pressure roller 23a core metal 23b elastic rubber layer 24 nip formation member 25 holding member 26 belt protection member 27 light shielding member 28 stay 29 Reflective member 30 Intermediate transfer belt 31 Primary transfer roller 32 Secondary transfer backup roller 33 Cleaning backup roller 34 Tension roller 35 Belt cleaning device 36 Secondary transfer roller 37 Use history acquisition means 38 Temperature detection means N Fixing nip P Paper R Transport path

JP 2007-334205 A JP 2012-230435 A

Claims (7)

A rotatable fixing member heated by a heat source;
A pressure member provided on the outside of the fixing member and facing the fixing member;
A nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the pressure member;
A lubricant interposed between the inner circumferential surface of the fixing member and the nip forming member;
Temperature detection means for detecting the temperature of at least one of the fixing member and the pressure member;
After completion of fixing, in the case of the fixing device capable of performing the excessive temperature rise preventing rotation for rotating the fixing member without heating when the temperature detected by the temperature detecting means has reached a predetermined temperature,
Equipped with usage history acquisition means for acquiring device usage history,
Changing at least one of the start temperature and the duration time of the excessive temperature rise prevention rotation based on the use history, and the start temperature of the excessive temperature rise prevention rotation when the use history exceeds a first specified value And a fixing device for restoring the duration to an initial setting value.   The fixing device according to claim 1, wherein at least one of the number of sheets passing, the traveling distance, the number of input jobs, the rotational torque of the device, and the accumulated use time is used as the use history.   The invention is characterized in that neither the start temperature nor the duration time of the excessive temperature rise prevention rotation is changed from an initial set value until the use history reaches a second specified value smaller than the first specified value. The fixing device according to 1 or 2.   The start temperature and / or the duration of the excessive temperature rise prevention rotation are changed using at least two of the number of sheets, traveling distance, number of input jobs, rotational torque of the apparatus, and cumulative use time. The fixing device according to any one of claims 1 to 3.   The fixing device according to any one of claims 1 to 4, wherein the start temperature and the duration time of the excessive temperature rise prevention rotation are not changed until the excessive temperature rise prevention rotation is completed.   The user is able to arbitrarily change the start temperature and duration of the excessive temperature rise prevention rotation, the first predetermined value, and / or the second predetermined value based on the usage history. The fixing device according to any one of 1 to 5.   An image forming apparatus comprising the fixing device according to any one of claims 1 to 6.

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