JP6533972B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus including a fixing unit provided with a heat equalizing member which abuts on a rotating body for fixing toner to a sheet and suppresses temperature unevenness on the surface of the rotating body.

  As a fixing device provided with the above-mentioned heat equalizing member, an image heating apparatus as described in Patent Document 1 is known. In this type of image heating apparatus (hereinafter referred to as a conventional fixing device), in order to reliably clean the surface of the heat equalizing member, a roll-like cloth or the like is brought into pressure contact with the heat equalizing member and wound up. So-called web cleaning is performed to remove dirt on the surface of the heat equalizing member while moving it. However, the mechanism for performing web cleaning requires many parts. Therefore, the cleaning of the heat equalizing member by the web cleaning has been one of the factors that hinder the miniaturization of the fixing device and hence the miniaturization of the image forming apparatus.

JP, 2014-48624, A

  An object of the present invention is to provide an image forming apparatus including a fixing device provided with a heat equalizing member, which can clean the heat equalizing member with a simpler structure.

An image forming apparatus according to an aspect of the present invention is
A fixing device for fixing toner to a sheet by heat and pressure, wherein a first rotating body heated by a first heat source and a nip portion for applying heat and pressure to the sheet are formed as the first rotating body A second rotating body, a heat equalizing member which abuts on the second rotary body and equalizes the temperature of the surface of the second rotary body, and cleaning which cleans the surface of the heat equalizing member by contacting the heat equalizing member A fuser having a member and a second heat source for heating the heat equalizing member;
A control unit that controls the fixing unit and each unit;
Equipped with
The cleaning member is a plate-like member whose corner is pressed against the heat equalizing member,
The heat equalizing member is movable, and while the heat equalizing member is being heated by the second heat source, the heat equalizing member is rotationally driven without being in contact with the second rotating body.
It is characterized by

  In the image forming apparatus which is an embodiment of the present invention, a second heat source for heating the heat equalizing member is provided to the heat equalizing member for equalizing the temperature of the second rotary body surface. When the second heat source heats the heat equalizing member, the dirt on the surface of the heat equalizing member is easily removed. As a result, cleaning of the heat equalizing member can be enabled with a simpler structure.

  According to the present invention, the heat equalizing member can be cleaned with a simple structure.

FIG. 1 is a diagram illustrating an entire configuration of an image forming apparatus according to an embodiment. FIG. 2 is a view showing the configuration of a fixing device according to an embodiment. It is a figure which shows the positional relationship of a pressure roller, a heat equalizing roller, a cleaning member, and a temperature sensor when it sees from the arrow M direction in FIG. It is a block diagram which concerns on control regarding cleaning of a heat equalizing roller. It is a flowchart of control regarding cleaning of a heat equalizing roller. It is a flowchart of control regarding cleaning of a heat equalizing roller. It is a figure which shows the positional relationship of the pressure roller which concerns on a 1st modification at the time of seeing from the arrow M direction in FIG. 2, a heat equalizing roller, a cleaning member, and a temperature sensor. FIG. 7 is a view showing the configuration of a fixing device according to another embodiment. FIG. 7 is a view showing the configuration of a fixing device according to another embodiment. FIG. 7 is a view showing the configuration of a fixing device according to another embodiment.

  Hereinafter, an image forming apparatus according to an embodiment will be described with reference to the accompanying drawings. In the drawings, the same members and portions are denoted by the same reference numerals, and redundant description will be omitted.

(Schematic configuration of the image forming apparatus, see FIG. 1)
The image forming apparatus 1 is a color printer using an electrophotographic method, and prints so-called tandem type toner images of four colors (Y: yellow, M: magenta, C: cyan, K: black) on paper . The image forming apparatus 1 has a function of forming an image on a sheet P based on image data read by a scanner, and as shown in FIG. 1, an image forming unit 2, a sheet feeding unit 15, and a timing roller pair 19. A fixing unit 20, a conveyance sensor 50, a pair of sheet discharge rollers 21, a sheet discharge tray 23, and a control unit 40 are provided.

  The control unit 40 controls the entire image forming apparatus 1 and is configured by, for example, a CPU.

  The sheet feeding unit 15 plays a role of feeding the sheets P one by one, and includes a sheet tray 16 and a sheet feeding roller 17. A plurality of sheets P in a state before printing are stacked and placed on the sheet tray 16. The sheet feeding roller 17 takes out the sheets P placed on the sheet tray 16 one by one.

  The timing roller pair 19 conveys the sheet while adjusting the timing so that the toner image is secondarily transferred to the sheet P conveyed by the sheet feeding roller 17 in the image forming unit 2.

  The image forming unit 2 forms a toner image on the sheet supplied from the sheet feeding unit 15. The image forming unit 2 includes an imaging unit 22 (22Y, 22M, 22C, 22K), a transfer unit 8, an intermediate transfer belt 11, a driving roller 12, two driven rollers 13, and a secondary transfer roller 14. There is.

  The imaging units 22 (22Y, 22M, 22C, 22K) include the photosensitive drums 4 (4Y, 4M, 4C, 4K), the chargers 5 (5Y, 5M, 5C, 5K), and the light scanning devices 6 (6Y, 6M). , 6C, 6K), a developing device 7 (7Y, 7M, 7C, 7K) and a cleaner 9.

  The photosensitive drums 4 (4Y, 4M, 4C, 4K) have a cylindrical shape and are rotated clockwise in FIG. The chargers 5 (5Y, 5M, 5C, 5K) charge peripheral surfaces of the photosensitive drums 4 (4Y, 4M, 4C, 4K). The light scanning device 6 scans a beam on the circumferential surface of the photosensitive drums 4 (4Y, 4M, 4C, 4K). Thereby, an electrostatic latent image is formed on the circumferential surface of the photosensitive drum 4 (4Y, 4M, 4C, 4K).

  The developing devices 7 (7Y, 7M, 7C, 7K) develop toner images based on electrostatic latent images on the photosensitive drums 4 (4Y, 4M, 4C, 4K).

  The transfer belt 11 is stretched between the driving roller 12 and the two driven rollers 13. The transfer unit 8 is disposed to face the inner peripheral surface of the intermediate transfer belt 11, and serves to primarily transfer the toner image formed on the photosensitive drum 4 to the intermediate transfer belt 11. The cleaner 9 recovers the toner remaining on the circumferential surface of the photosensitive drum 4 after the primary transfer. The driving roller 12 drives the intermediate transfer belt 11 in the direction of the arrow α. Thus, the intermediate transfer belt 11 conveys the toner image to the secondary transfer roller 14.

  The secondary transfer roller 14 faces the intermediate transfer belt 11 and has a drum shape. Then, the secondary transfer roller 14 secondarily transfers the toner image carried by the intermediate transfer belt 11 onto the sheet P passing between the intermediate transfer belt 11 and the secondary transfer roller 14 by applying a transfer voltage. .

  The sheet P on which the toner image has been secondarily transferred is subjected to a fixing process by a fixing unit 20 described later, and is discharged onto a sheet discharge tray 23 by a sheet discharge roller pair 21. A conveyance sensor 50 is provided downstream of the fixing unit 20 in the sheet conveyance direction, and detects the passage of the sheet P from the fixing unit 20 toward the discharge roller pair 21.

(Structure of the fixing unit See FIGS. 2 and 3)
The fixing device 20 is a device for fixing the toner image to the sheet P by heat and pressure. The fixing device 20 further includes a heating roller 20a, a pressure roller 20b, and a heating unit 20c.

  The heating roller 20a is composed of a core metal 41, a sponge rubber 42 and a belt 43, and has a diameter of 40 mm. The cored bar 41 is a cylinder made of SUS304. The sponge rubber 42 is bonded around the core 41 and has a thickness of 10 mm. The sponge rubber 42 is made of, for example, silicone rubber.

  The belt 43 is wound around the sponge rubber 42 and is endless. Thereby, the sponge rubber 42 is in contact with the inner peripheral surface of the belt 43. The belt 43 is composed of a Ni layer 431, a silicone solid rubber 432 and a release layer 433.

  The Ni layer 431, the silicone solid rubber 432 and the release layer 433 are laminated in this order from the inner peripheral surface side of the heating roller 20a to the outer peripheral surface side. The Ni layer 431 is a layer having a thickness of 40 μm, and generates eddy current and self heat generation under the influence of magnetic lines of force whose strength changes by a heating unit 20 c described later. The silicone solid rubber 432 has a thickness of 0.2 mm. The release layer 433 is a layer for preventing the toner from adhering to the surface of the belt 43, and is made of, for example, PFA (perfluoroalkoxy fluorine resin). The release layer 433 has a thickness of 30 μm.

  The pressure roller 20b is composed of a core metal 51 and silicone solid rubber 52, and has a diameter of 40 mm. The pressure roller 20 b is in pressure contact with the belt 43.

  The cored bar 51 is a cylinder (for example, STKM pipe) made of metal with a diameter of 32 mm. The silicone solid rubber 52 is bonded around the core 51 and has a thickness of 4 mm. A release layer (not shown) made of PFA is provided on the surface of the silicone solid rubber 52 to prevent the toner from adhering to the pressure roller 20b.

  The pressure roller 20b is connected to a drive source (not shown). Then, when the pressure roller 20b, which receives power from a drive source (not shown), is rotated, the heating roller 20a, which forms a nip with the pressure roller 20b, is driven to rotate.

  The heating unit 20 c includes an exciting coil 61 and ferrite cores 62, 62 a and 62 b, and heats the belt 43 by supplying a high frequency alternating current to the exciting coil 61. The heating unit 20c is provided outside the heating roller 20a.

  The exciting coil 61 is a coil manufactured by winding a conducting wire, and generates a magnetic flux whose direction is periodically changed by supplying an alternating current. The ferrite cores 62, 62a, 62b guide the magnetic flux generated by the exciting coil 61 to the belt 43. As a result, magnetic flux whose direction changes periodically passes through the Ni layer 431. As a result, an eddy current is generated in the Ni layer 431 and the Ni layer 431 generates heat.

  Here, in order to control the heating of the heating roller 20a by the exciting coil 61, a temperature sensor TC1 is provided at a central portion in the longitudinal direction of the heating roller 20a (a direction parallel to the rotation axis of the heating roller 20a). The temperature sensor TC1 is, for example, a thermistor disposed near the surface of the heating roller 20a, detects the surface temperature of the heating roller 20a, and outputs the detected temperature to the control unit 40. When the control unit 40 receives the surface temperature from the temperature sensor TC1, the power supplied to the exciting coil 61 is maintained such that the surface temperature of the heating roller 20a is maintained at a predetermined fixing temperature (that is, the target temperature at the time of image heating). Control.

  The fixing device 20 further includes two temperature sensors TC2 and TC3 in addition to the temperature sensor TC1. As shown in FIG. 3, the temperature sensor TC2 is provided at the central portion of the pressure roller 20b in the longitudinal direction (direction parallel to the rotational axis of the pressure roller 20b), and the temperature sensor TC3 is in the longitudinal direction of the pressure roller 20b. It is provided at the end. The temperature sensors TC2 and TC3 are, for example, thermistors disposed in the vicinity of the surface of the pressure roller 20b, detect the surface temperature of the pressure roller 20b, and output the detected temperature to the control unit 40. The control unit 40 calculates the temperature difference between the central portion and the end portion of the pressure roller 20b using the temperatures detected from the temperature sensors TC2 and TC3 and detects the occurrence of temperature unevenness in the pressure roller 20b.

  The fixing device 20 configured as described above fixes the toner image on the sheet P passing between the heating roller 20 a and the pressing roller 20 b. Specifically, as shown in FIG. 2, the sheet P having the toner image formed on the main surface contacts the heating roller 20 a to heat and melt the toner image. Further, the toner image is pressed against the sheet P by the pressure from the heating roller 20 a and the pressure roller 20 b. That is, the toner image is fixed on the sheet P by heat and pressure.

  The fixing device 20 further includes a heat equalizing roller 20d, a cleaning member 20e, and a temperature sensor TC4.

  The heat equalizing roller 20 d is a member for suppressing temperature unevenness on the surface of the pressure roller 20 b. Specifically, the heat equalizing roller 20d is a cylindrical member made of a material having high thermal conductivity, such as copper or aluminum. Then, by bringing the heat equalizing roller 20 d into contact with the pressure roller 20 b, heat is transferred from the high temperature portion to the low temperature portion of the pressure roller 20 b via the heat equalizing roller 20 d. Thereby, the temperature unevenness on the surface of the pressure roller 20b is suppressed. In the state where the heat equalizing roller 20d is in contact with the pressure roller 20b, the heat equalizing roller 20d is driven to rotate by the rotation of the pressure roller 20b.

  The cleaning member 20 e is a member for cleaning the surface of the heat equalizing roller 20 d. The cleaning member 20e is a rectangular plate-like member, a so-called blade, and is made of polyimide having a thickness of 0.125 mm. Further, as described above, since the heat equalizing roller 20d is in contact with the pressure roller 20b, paper dust and toner of the sheet P pressurized by the pressure roller 20b adhere to the surface of the heat equalizing roller 20d. ing. Here, the corner of the cleaning member 20e is in contact with the surface of the heat equalizing roller 20d. Thus, when the heat equalizing roller 20 d rotates, the dirt on the surface of the heat equalizing roller 20 d is mechanically removed by the corner portion of the cleaning member 20 e. In the present embodiment, the width W of the portion of the cleaning member 20e in contact with the heat equalizing roller 20d is, as shown in FIG. 3, the width of the heat equalizing roller 20d in the direction orthogonal to the rotation direction of the heat equalizing roller 20d. Equal to Further, as shown in FIG. 2, the cleaning member 20 e is a so-called trailing method in which the cleaning member 20 e is in contact with the heat equalizing roller 20 d in the forward direction. When a sheet with a high ash fraction, such as recycled paper or foreign paper, containing a large amount of inorganic particles such as talc and kallion and calcium carbonate is used as the paper P, the amount of generated paper dust is generally large.

  By the way, when the state where the heat equalizing roller 20 d is pressed against the pressure roller 20 b continues for a long time, stains such as paper dust and toner attached to the heat equalizing roller 20 d grow and solidify. As a result, the dirt on the surface of the heat equalizing roller 20 d can not be removed sufficiently only by bringing the end of the cleaning member 20 e into contact with the surface of the heat equalizing roller 20 d. Then, if the stains on the surface of the heat equalizing roller 20d are not removed, the stains damage the surface of the pressure roller 20b, which affects the print quality. Therefore, a halogen heater 20f for heating the heat equalizing roller 20d is provided inside the heat equalizing roller 20d.

  The halogen heater 20 f lights up, for example, every 500 sheets of paper P passing through the fixing device 20. That is, the halogen heater 20f is turned on when a certain amount of paper dust, toner and the like adhere to the surface of the heat equalizing roller 20d. By this lighting, the surface of the heat equalizing roller 20 d is heated to, for example, about 150 ° C. When the surface of the heat equalizing roller 20 d is heated to about 150 ° C., dirt such as paper dust and toner fixed on the surface of the heat equalizing roller 20 d is softened. Thus, the dirt on the surface of the heat equalizing roller 20d can be easily removed by the cleaning member 20e. The dirt on the surface of the heat equalizing roller 20d may not be completely removed or may be leveled. This is because if the surface of the heat equalizing roller 20 d can be kept smooth, the surface of the pressure roller 20 b can be prevented from being scratched.

  Further, during heating of the heat equalizing roller 20d by the halogen heater 20f, the heat equalizing roller 20d is not in contact with the pressure roller 20b. This is to prevent the dirt on the surface of the heat equalizing roller 20 d from adhering to the pressure roller 20 b by softening the dirt on the surface of the heat equalizing roller 20 d. As described above, in order to prevent the heat equalizing roller 20d from temporarily contacting the pressure roller 20b, the heat equalizing roller 20d is connected to moving means 110 (not shown in FIG. 2) that enables the movement of the heat equalizing roller 20d. There is. Further, the heat equalizing roller 20d is connected to a drive motor 120 (not shown in FIG. 2) so that the heat equalizing roller 20d can rotate independently even when not contacting the pressure roller.

  The temperature sensor TC4 is provided for controlling the heating of the heat equalizing roller 20d by the halogen heater 20f. The temperature sensor TC4 is, for example, a thermistor disposed in the vicinity of the surface of the heat equalizing roller 20d, detects the surface temperature of the heat equalizing roller 20d, and outputs the detected temperature to the control unit 40. When receiving the surface temperature from the temperature sensor TC4, the control unit 40 controls the power supplied to the halogen heater 20f so that the surface temperature of the heat equalizing roller 20d is maintained at a predetermined temperature.

(Control related to cleaning of heat equalizing roller See FIGS. 4 to 6)
As shown in FIG. 4, the control unit 40 controls the cleaning of the heat equalizing roller 20 d in the image forming apparatus 1 based on signals from the conveyance sensor 50, the user interface 130, the temperature sensors TC 2, TC 3, TC 4, etc. This is performed by activating a member related to cleaning of the heat equalizing roller 20d, for example, a halogen heater 20f or the like. Hereinafter, control relating to the cleaning of the heat equalizing roller 20d will be described with reference to the flowcharts of FIGS. 5 and 6.

  The control starts with the temperature difference between the central portion and the end portion of the pressure roller 20b becoming equal to or greater than a predetermined temperature difference as a trigger. The temperature difference between the central portion and the end portion of the pressure roller 20b is calculated by the CPU 104 in the control unit 40 which has received information on the temperature detected from the temperature sensors TC2 and TC3. Further, at the start of this control, the heat equalizing roller 20 d is not in contact with the pressure roller 20 b.

  In the first step R1 relating to the cleaning of the heat equalizing roller 20d, the control unit 40 brings the heat equalizing roller 20d into contact with the pressure roller 20b via the moving means 110.

  In the second step R2, in response to the signal from the conveyance sensor 50, the control unit 40 counts up the count number n of the counter related to the cleaning of the heat equalizing roller 20d by one. That is, when one sheet of paper P passes the fixing device 20 after the heat equalizing roller 20 d contacts the pressure roller 20 b, the count number n is increased by one.

  In the third step R3, the control unit 40 determines whether the sheet P having passed through the fixing unit 20 is the final sheet in the present print job, that is, whether or not the image formation is completed. When the image formation ends, the present control proceeds to the fifth step R5, and when the image formation does not end, the present control proceeds to the fourth step R4.

  In the fourth step R4, the control unit 40 determines whether the temperature difference between the central portion and the end portion of the pressure roller 20b is less than a predetermined temperature difference, that is, the temperature unevenness in the pressure roller 20b has been eliminated. It is determined whether or not. When the temperature non-uniformity is eliminated, the present control proceeds to a fifth step R5, and when the temperature non-uniformity is not eliminated, the present control proceeds to a sixth step R6.

  In the fifth step R5, the control unit 40 separates the heat equalizing roller 20d from the pressure roller 20b via the moving means 110. As a result, the heat equalizing roller 20 d is not in contact with the pressure roller 20 b. And when it progresses to 5th step R5, this control is complete | finished after that.

  In the sixth step R6, the control unit 40 determines whether the count number n of the counter related to the cleaning of the heat equalizing roller 20d has reached 500. That is, after the control unit 40 brings the heat equalizing roller 20 d into contact with the pressure roller 20 b, the control unit 40 determines whether 500 sheets of paper P have passed through the fixing device 20. When it is determined that the count number n has reached 500, the present control proceeds to a seventh step R7, and when it is determined that the count number n has not reached 500, the present control returns to the second step R2.

  In the seventh step R7, the control unit 40 temporarily stops the image formation.

  In the eighth step R8, the control unit 40 separates the heat equalizing roller 20d from the pressure roller 20b via the moving means 110. As a result, the heat equalizing roller 20 d is not in contact with the pressure roller 20 b.

  In the ninth step R9, the control unit 40 controls the lighting time and heating temperature of the halogen heater 20f for heating the heat equalizing roller 20d based on the history of image formation up to that point in the data storage unit 102 in the control unit 40. Select from a table with heating temperatures, stored in a plurality of lighting times, and decide. For example, it is assumed that the lighting time of the halogen heater 20 f is stored for 7 seconds and 15 seconds and the heating temperature is 130 ° C. and 150 ° C. in the table in the data storage unit 102. Here, by the time the counter number n reaches 500, the paper on which relatively large amount of paper dust such as recycled paper or overseas paper is generated is image-formed for a fixed number of times or more, and the average value of the printing rate is a predetermined value If it is lower than the above, the amount of stains adhering to the heat equalizing roller 20d increases. Specifically, when the ratio of generation of paper dust is high, since the toner and paper dust mix well, the viscosity of the stain becomes high. As a result, the stains are easily fixed to the heat equalizing roller 20d, and the amount of the stains fixed to the heat equalizing roller 20d is increased. In this case, the lighting time of the halogen heater 20 f is 15 seconds, and the heating temperature is 150 ° C. This is to lengthen the lighting time of the halogen heater 20 f and raise the heating temperature to soften the dirt on the heat equalizing roller 20 d and promote the removal of the dirt. On the other hand, when the number of times of selection of paper such as recycled paper or foreign paper is less than a certain number and the average value of the printing rate is higher than a predetermined value, the amount of dirt adhering to the heat equalizing roller 20d is Relatively few. Specifically, when the number of times of selection of paper such as recycled paper or foreign paper is less than a certain number and the average value of printing rates is higher than a predetermined value, that is, the ratio of generated paper dust is low Since the amount of toner and paper dust mixed is small, the viscosity of the stain generated thereby is also low. Therefore, even if the cleaning member 20e is pressed against the heat equalizing roller 20d, it is possible to remove a large amount of dirt, and the amount of dirt remaining on the heat equalizing roller 20d and remaining is reduced. In this case, the lighting time of the halogen heater 20 f is 7 seconds, and the heating temperature is 130 ° C. That is, when the amount of contamination is small, the lighting time is shortened and the heating temperature is lowered.

  In the tenth step R10, the control unit 40 turns on the halogen heater 20f.

  In an eleventh step R11, the control unit 40 rotates the heat equalizing roller 20d via the drive motor 120. As a result, the dirt on the surface of the heat equalizing roller 20d is scraped off or leveled off by the cleaning member 20e. In the present embodiment, the start of the drive motor 120 is substantially simultaneous with the lighting of the halogen heater 20f.

  In a twelfth step R12, the control unit 40 starts a timer that counts time T1. The time T1 is a time until the control unit 100 stops the halogen heater 20f with reference to the operation start time of the halogen heater 20f.

  In a thirteenth step R13, the control unit 40 determines whether or not the time T1 has elapsed. If the time T1 has elapsed, the process proceeds to a fourteenth step R14. If the time T1 has not elapsed, the present process waits until the time T1 elapses in a thirteenth step R13.

  In the fourteenth step R14, the control unit 40 turns off the halogen heater 20f.

  In the fifteenth step R15, the control unit 40 stops the drive motor 120. That is, the control unit 40 stops the heat equalizing roller 20 d. In the present embodiment, the stop of the drive motor 120 is substantially simultaneous with the turning off of the halogen heater 20 f.

  In the sixteenth step R16, the control unit 40 resets the count number n of the counter n related to the cleaning of the heat equalizing roller 20d.

  In the seventeenth step R17, the control unit 40 resumes the image formation which has been stopped. At this point, the control relating to the cleaning of the heat equalizing roller ends. When the temperature difference between the central portion and the end portion of the pressure roller 20b becomes equal to or greater than a predetermined temperature difference, the present control is resumed.

(effect)
In the image forming apparatus 1, a halogen heater 20f for heating the heat equalizing roller 20d is provided to the heat equalizing roller 20d which equalizes the temperature of the surface of the pressure roller 20b. When the halogen heater 20f heats the heat equalizing roller 20d, the dirt adhering to the surface of the heat equalizing roller 20d is easily softened and fallen off. As a result, cleaning of the heat equalizing roller 20d can be performed with a simple structure such as blade cleaning without using a complicated mechanism such as web cleaning.

  Further, in the image forming apparatus 1, the heat equalizing roller 20d is not in contact with the pressure roller 20b while the heat equalizing roller 20d is being heated by the halogen heater 20f. As a result, the dirt softened on the surface of the heat equalizing roller 20 d can be prevented from adhering to the pressure roller 20 b. Furthermore, the heat of the heat equalizing roller 20d heated by the halogen heater 20f can be transmitted to the pressure roller 20b, and the quality of the image formed on the sheet P can be prevented from being affected.

  In addition to this, in the image forming apparatus 1, the heat equalizing roller 20d is in contact with the pressure roller 20b even when the temperature difference between the center portion and the end portion of the pressure roller 20b is less than the predetermined temperature difference. Absent. By doing so, it is possible to suppress the adhesion of dirt from the pressure roller 20b to the surface of the heat equalizing roller 20d.

  By the way, in the image forming apparatus 1, the lighting time and heating temperature of the halogen heater 20f are determined based on the history of image formation up to that point. Specifically, for example, when it is judged from the image formation history that the control unit 40 has little adhesion of dirt to the surface of the heat equalizing roller 20 d, the lighting time of the halogen heater 20 f is shortened. Thereby, the cleaning time of the heat equalizing roller 20d can be shortened. As a result, the image formation which has been temporarily stopped for cleaning the heat equalizing roller 20d can be resumed early. Further, when it is judged from the image formation history that the control unit 40 has little adhesion of the stain to the surface of the heat equalizing roller 20 d, the heating temperature of the halogen heater 20 f is lowered. Thereby, the power consumption of the halogen heater 20f accompanying cleaning of the heat equalizing roller 20d can also be suppressed. That is, in the image forming apparatus 1, by determining the lighting time and heating temperature of the halogen heater 20f based on the history of image formation up to that point, the productivity of image formation is improved, and the suppression of power consumption is realized. It is possible.

(Refer to FIG. 7 in the first modification)
The difference between the image forming apparatus 1A according to the first modification and the image forming apparatus 1 according to the embodiment is the cleaning member 20e.

  Specifically, the width W of the portion of the image forming apparatus 1A where the cleaning member 20e is in contact with the heat equalizing roller 20d is the width of the heat equalizing roller 20d in the orthogonal direction v orthogonal to the rotation direction of the heat equalizing roller 20d. It is narrower than. That is, the cleaning member 20 e in the image forming apparatus 1 A is smaller than the cleaning member 20 e in the image forming apparatus 1. However, the cleaning member 20e in the image forming apparatus 1A is provided with a moving mechanism (not shown) for reciprocating in the orthogonal direction v during cleaning of the heat equalizing roller 20d. Accordingly, in the image forming apparatus 1A, the heat equalizing roller 20d can be cleaned by the cleaning member 20e smaller than the image forming apparatus 1.

  The other configurations, effects, and the like in the image forming apparatus 1A according to the first modification are the same as those described in the image forming apparatus 1 according to the embodiment.

(2nd modification)
The difference between the image forming apparatus 1B according to the second modification and the image forming apparatus 1 according to the embodiment is control regarding cleaning of the heat equalizing roller.

  In the image forming apparatus 1B, after turning off the halogen heater 20f in the fourteenth step R14, the control unit 40 resumes image formation after a predetermined time has elapsed. Therefore, when the heat equalizing roller 20 d comes into contact with the pressure roller 20 b again, the heat equalizing roller 20 d is cooled and then brought into contact with the pressure roller 20 b. As a result, the heat equalizing roller 20d immediately after heating by the halogen heater 20f comes into contact with the pressure roller 20b, and the pressure roller 20b is prevented from being heated more than necessary. As a result, it is possible to suppress the situation where the image quality of the sheet P passing through the fixing device 20 is affected by the pressure roller 20b which is heated more than necessary. In particular, since a coated paper or the like may generate blisters due to a high temperature, it is effective to cool the heat equalizing roller 20d to a predetermined temperature and then contact the pressure roller 20b as described above.

  The other configurations, effects, and the like in the image forming apparatus 1B according to the second modification are the same as those described in the image forming apparatus 1 according to the embodiment.

(Third modification)
The difference between the image forming apparatus 1C according to the third modification and the image forming apparatus 1 according to the embodiment is the method of detecting the temperature difference between the center and the end of the pressure roller 20b.

  The image forming apparatus 1C is not provided with temperature sensors TC2 and TC3 for detecting the occurrence of temperature unevenness in the pressure roller 20b. Instead, the control unit 40 estimates that temperature unevenness occurs in the pressure roller 20b when a relatively small sheet P is selected by an input from the user interface 130 or the like. Based on the estimation result, the control unit 40 brings the heat equalizing roller 20 d into contact with the pressure roller 20 b.

  As described above, in the image forming apparatus 1C, the temperature sensors TC2 and TC3 for detecting the occurrence of temperature unevenness in the pressure roller 20b are unnecessary. Therefore, the image forming apparatus 1C has a smaller number of members relating to the heat equalizing roller 20d than the image forming apparatus 1 and is simpler. The other configurations, effects, and the like in the image forming apparatus 1C according to the third modification are the same as those described in the image forming apparatus 1 according to the embodiment.

(4th modification)
The difference between the image forming apparatus 1D according to the fourth modification and the image forming apparatus 1 according to the embodiment is control regarding cleaning of the heat equalizing roller.

  In the second step R2 of the control related to cleaning of the heat equalizing roller in the image forming apparatus 1D, the control unit 40 controls the cleaning of the heat equalizing roller 20d according to the type and printing rate of the sheet passing through the fixing device 20. Change the count-up number of the count number n. For example, in the case of paper in which relatively large amounts of paper dust are generated, such as recycled paper and foreign paper, and the printing rate is low, the count-up number is set to 3, and paper other than recycled paper and overseas paper; When is low, the count-up number is 2, and when the printing rate is high, the count-up number is 1.

  As described above, the cleaning interval on the surface of the heat equalizing roller 20 d is adjusted by changing the count-up number of the count number n of the counter related to the cleaning of the heat equalizing roller 20 d according to the type of paper and the printing rate. Can. This can optimize the cleaning timing of the heat equalizing roller 20d, and contributes to the improvement of the productivity of the image forming apparatus 1D and the power saving.

  The other configurations, effects, and the like in the image forming apparatus 1D according to the fourth modification are the same as those described in the image forming apparatus 1 according to the embodiment.

(Other embodiments)
The image forming apparatus according to the present invention is not limited to the above embodiment, and can be variously modified within the scope of the invention. For example, the count number n of the counter related to the cleaning of the heat equalizing roller 20d is arbitrary. Further, as shown in FIG. 8, the cleaning member 20e may be a so-called leading system in which the contact direction of the cleaning member 20e with respect to the heat equalizing roller 20d is counter contact. Furthermore, the cleaning member 20e may be a so-called cleaner roller provided with PPS brush fibers having a hair length of about 2 mm as shown in FIG. 9 on the surface of a metal roller, and silicone rubber as shown in FIG. It may be a cuboid pad member impregnated with an abrasive. And each embodiment may be combined.

  As described above, the present invention is useful for an image forming apparatus, and is particularly excellent in that cleaning of the heat equalizing member can be performed with a simple structure.

TC2, TC3 Temperature sensors 1, 1A, 1B, 1C, 1D Image forming apparatus 20 Fixing device 20a Heating roller (first rotating body)
20b Pressure roller (second rotating body)
20c heating unit (first heat source)
20d Heat equalizing roller (heat equalizing member)
20e cleaning member 20f halogen heater (second heat source)
40 control unit

Claims (11)

A fixing device for fixing toner to a sheet by heat and pressure, wherein a first rotating body heated by a first heat source and a nip portion for applying heat and pressure to the sheet are formed as the first rotating body A second rotating body, a heat equalizing member which abuts on the second rotary body and equalizes the temperature of the surface of the second rotary body, and cleaning which cleans the surface of the heat equalizing member by contacting the heat equalizing member A fuser having a member and a second heat source for heating the heat equalizing member;
A control unit that controls the fixing unit and each unit;
Equipped with
The cleaning member is a plate-like member whose corner is pressed against the heat equalizing member,
The heat equalizing member is movable, and while the heat equalizing member is being heated by the second heat source, the heat equalizing member is rotationally driven without being in contact with the second rotating body.
An image forming apparatus characterized by Cleaning the surface of the heat equalizing member while moving the cleaning member in a predetermined direction;
The image forming apparatus according to claim 1, wherein The heat equalizing member is rotatable;
The image forming apparatus according to any one of claims 1 and 2 , characterized in that A fixing device for fixing toner to a sheet by heat and pressure, wherein a first rotating body heated by a first heat source and a nip portion for applying heat and pressure to the sheet are formed as the first rotating body A second rotating body, a heat equalizing member which abuts on the second rotary body and equalizes the temperature of the surface of the second rotary body, and cleaning which cleans the surface of the heat equalizing member by contacting the heat equalizing member A fuser having a member and a second heat source for heating the heat equalizing member;
A control unit that controls the fixing unit and each unit;
Equipped with
The heat equalizing member is movable and does not contact the second rotating body under predetermined conditions.
The heat equalizing member is heated by the second heat source without being in contact with the second rotating body, is cooled to a predetermined temperature, and then contacts the second rotating body.
Images forming device you characterized. When the temperature difference between the center and the end in the direction of the rotation axis parallel to the rotation axis of the second rotation body in the second rotation body is smaller than a predetermined temperature difference, the heat spreader is Not contacting the second rotating body,
The image forming apparatus according to any one of claims 1 to 4, wherein The temperature difference between the central portion and the end portion in the rotational axis direction is measured by a temperature sensor that detects the temperature of the second rotating body,
The image forming apparatus according to claim 5 , wherein The control unit estimates a temperature difference between a central portion and an end portion in the rotation axis direction from the size of a sheet on which an image is formed.
The image forming apparatus according to claim 5 , wherein The control unit may determine a heating temperature when the heat equalizing member is heated by the second heat source, based on a history of images formed so far.
The image forming apparatus according to any one of claims 1 to 7 , wherein The control unit may determine a heating time when heating the heat equalizing member by the second heat source based on a history of images formed so far.
The image forming apparatus according to any one of claims 1 to 8 , wherein The control unit may determine an interval for heating the heat equalizing member by the second heat source based on a history of images formed so far.
The image forming apparatus according to any one of claims 1 to 9 , wherein The second heat source heats the heat equalizing member when image formation is not performed.
The image forming apparatus according to any one of claims 1 to 10 , wherein

Images