JP2016018062A - Fixation device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device capable of detecting a local temperature rise of a fixation member and efficiently preventing the generation of temperature overshoot.SOLUTION: A fixation device comprises: a fixation member 38 that is heated by heating means 56, rotates in a prescribed direction and fuses by heating and fixes an unfixed image T on a recording material P; a pressure member 30b that rotates in a prescribed direction and forms a fixation nip part N by pressure-contacting with the fixation member 38; a thermopile array 34 having a plurality of channels and capable of detecting temperatures of a plurality of areas on the surface of the fixation member 38; and heating control means 42 that controls the heating by the heating means 56. After an operation of conveying the recording material P to the fixation nip part N is completed, an idle rotation mode is executed, for rotating the fixation member 38 and the pressure member 30b in a state in which the heating of the fixation member 38 by the heating means 56 is stopped, when a prescribed condition is satisfied.SELECTED DRAWING: Figure 2

Description

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

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed on an image carrier based on image information, the toner image is transferred onto a recording material such as paper or an OHP sheet, and the toner image is carried. The recorded material is passed through a fixing device, and the toner image is fixed on the recording material by heat and pressure.

  As a heating method of the fixing means in the fixing device, for example, a belt and film method (see Patent Documents 1 and 2), a method of heating a heat insulating roller from the outside (see Patent Document 3), and only an image area based on image information. Technologies for selectively heating have been proposed.

The fixing device described in Patent Document 1 is configured to sandwich a plate-like heating body that contacts a thin cylindrical heat-resistant film and a pressure roller so that the film and the recording material are brought into close contact with each other, thereby applying thermal energy to the recording material. It is. Since the film is as thin as about 100 μm, the start-up time can be substantially increased only by raising the temperature of the plate-like heating body having a small heat capacity, so that the start-up time can be shortened and the preheating power can be reduced.
In Patent Document 1, the control temperature and heating area of the heating body are changed in accordance with the image formed on the recording material, and energy is supplied to the non-image area (the area where no image exists in the image forming area). The structure which enables energy saving by reducing is disclosed.

  Japanese Patent Application Laid-Open No. 2004-228688 has a configuration in which the temperature of each element of the heating element of the thermal head is measured and supplied with appropriate heat so that the influence of the ambient temperature is taken into consideration and heat is applied only to the toner portion on the paper surface. It is disclosed.

  The fixing device disclosed in Patent Document 3 is configured to heat a roller from the outside. This configuration has the advantage that the rise time is shorter and the energy loss is less than the internal heating method that heats the entire fixing roller by melting the toner with the heat stored in the vicinity of the surface of the fixing roller by heating from the outside. is there. In addition, a technique is described in which the external heating unit is controlled so that the temperature of the portion of the fixing roller corresponding to the non-image region is lower than the temperature of the portion corresponding to the image region.

  When a large amount of paper passes continuously, the temperature of the members inside the fixing device is rising and the amount of heat is stored. If the rotation of the fixing member and the pressure member is stopped immediately after the paper is passed in this state, the fixing member (fixing sleeve) is further heated by the heat of the internal member, and a temperature overshoot may occur. Further, the temperature overshoot may cause the generation of contaminants such as volatile organic compounds (VOC) and fine particles from the fixing sleeve.

In order to avoid the occurrence of such a temperature overshoot after paper passing, a technique is known in which the fixing roller is cooled by idling the apparatus for a predetermined time (see, for example, Patent Document 4).
Patent Document 4 describes that the idling mode is executed when the detected temperature detected by the temperature detecting means exceeds a predetermined threshold value. As the temperature detection means, a temperature sensor arranged on the fixing sleeve side is used, and execution of the idling mode is determined based on the detected temperature.

  However, since the temperature detection means is limitedly arranged from the viewpoint of installation space, cost, and the like, it is difficult to detect in detail the temperatures at a plurality of points on the fixing sleeve. When a local temperature rise occurs in a region where temperature cannot be detected, there is a problem that it cannot be detected, and measures for preventing the occurrence of temperature overshoot, for example, execution determination of the idling mode cannot be made.

  In view of the above problems, an object of the present invention is to provide a fixing device that can detect a local temperature increase of a fixing member and can efficiently prevent the occurrence of a temperature overshoot.

  In order to solve the above-described problems, a fixing device according to the present invention is heated by a heating unit and rotates in a predetermined direction, and a fixing member that heats and melts an unfixed image and fixes it on a recording material, and rotates in a predetermined direction. A pressure member that presses against the fixing member to form a fixing nip portion, a thermopile array that has a plurality of channels and can detect temperatures of a plurality of regions on the surface of the fixing member, and is heated by the heating unit. A heating control means for controlling, and after the operation of transporting the recording material to the fixing nip portion is completed, the heating of the fixing member by the heating means is stopped when a predetermined condition is satisfied. The fixing device is configured to execute an idling mode in which the fixing member and the pressure member are rotated.

  According to the fixing device of the present invention, it is possible to detect a local temperature rise of the fixing member without increasing the space and cost required for installing the temperature detecting means, and efficiently prevent the occurrence of temperature overshoot. A possible fixing device can be provided.

1 is a schematic cross-sectional view illustrating an example of an overall configuration of an image forming apparatus according to an exemplary embodiment. FIG. 3 is an explanatory diagram illustrating an example of a configuration of a fixing device according to an exemplary embodiment. FIG. 3 is a schematic diagram illustrating an example of a heating unit of the fixing device according to the exemplary embodiment. 6 is a flowchart showing a flow of an idling mode implementation of the fixing device of the present embodiment. It is explanatory drawing which shows typically the thermopile array and temperature detection range of the fixing device of this embodiment. It is explanatory drawing which shows the aspect of arrangement | positioning of the thermopile array of the fixing device of this embodiment, and the surface temperature detection of a fixing member.

  Hereinafter, a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments of the examples shown below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art. Any aspect is included in the scope of the present invention as long as the operations and effects of the present invention are exhibited.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus provided with the fixing device of the present embodiment.
As shown in FIG. 1, a printer as an example of an image forming apparatus includes a sheet feeding unit 4, a registration roller pair 6, a photosensitive drum 8 as an image carrier, a transfer unit 10, a fixing device 12, and the like. .

The paper feeding means 4 feeds the paper P as a recording material stored in a stacked state and the paper P stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16.
The paper P sent out by the paper feed roller 16 is temporarily stopped by the registration roller pair 6, the posture deviation is corrected, and then the timing synchronized with the rotation of the photosensitive drum 8, that is, the toner formed on the photosensitive drum 8. It is sent to the transfer site 11 by the registration roller pair 6 at the timing when the leading edge of the image coincides with a predetermined position at the leading edge of the sheet P in the transport direction.

The direction of rotation of the photosensitive drum 8 is indicated by an arrow. Outside the photosensitive drum 8, a charging roller 18 as a charging unit, a mirror 20 constituting a part of an exposure unit (not shown), a developing unit 22 including a developing roller 22 a, a transfer unit 10, and a cleaning in order of rotation. A cleaning means 24 having a blade 24a is disposed.
Between the charging roller 18 and the developing unit 22, exposure light Lb is irradiated on the exposure unit 26 on the photosensitive drum 8 through the mirror 20 and scanned.

When the photosensitive drum 8 starts to rotate, the surface of the photosensitive drum 8 is uniformly charged by the charging roller 18. Based on the image information, the exposure light Lb is irradiated and scanned on the exposure unit 26 to form an electrostatic latent image corresponding to the image to be created.
The formed electrostatic latent image is moved to the developing means 22 by the rotation of the photosensitive drum 8, where toner is supplied to be visualized to form a toner image.

  The toner image formed on the photosensitive drum 8 is transferred by transfer bias application onto the paper P that has entered the transfer portion 11 at a predetermined timing in the transfer means 10.

  The paper P carrying the toner image is conveyed toward the fixing device 12, fixed on the fixing device 12, and then discharged and stacked on a paper discharge tray (not shown).

  Residual toner remaining on the photosensitive drum 8 without being transferred at the transfer portion 11 reaches the cleaning means 24 as the photosensitive drum 8 rotates, and is scraped off by the cleaning blade 24 a while passing through the cleaning means 24. Is removed.

  Thereafter, the residual potential on the photosensitive drum 8 is removed by a neutralizing unit (not shown), and is prepared for the next image forming process.

The configuration of the fixing device 12 of this embodiment is shown in FIG.
The fixing device 12 of the present embodiment is heated by a heating unit 56, rotates in a predetermined direction, heats and melts an unfixed image (toner image) T, and fixes it to a recording material (paper) P, and a predetermined member A pressure member 30 that rotates in the direction and presses against the fixing member 38 to form the fixing nip portion N, and a thermopile array 34 that has a plurality of channels and can detect temperatures of a plurality of regions on the surface of the fixing member. And heating control means for controlling heating by the heating means 56, and when the predetermined condition is satisfied after the conveying operation of the recording material (paper) P to the fixing nip N is completed, the heating means 56 An idling mode in which the fixing member 38 and the pressure member 30 are rotated while the heating of the fixing member 38 is stopped is executed.

As shown in FIG. 2, the fixing device 12 includes heating means 56 such as a halogen heater or an IH coil inside a fixing member 38 such as a film or a sleeve. The heating means 56 is pressed against the surface of the fixing member 38 by an urging means (not shown).
The heating unit 56 may be provided outside the fixing member 38. Further, since the heating means 56 functions as a pressing member, it may be disposed at the fixing nip portion N as in the so-called SURF fixing configuration.
As the temperature of the fixing member 38 rises, the unfixed image (toner image) T on the paper P conveyed to the fixing nip N is heated and fixed on the paper P.

  FIG. 3 shows a schematic diagram of the heating means 56. The heating means shown in FIG. 3 is a planar heater in which a resistance heating element is provided on a planar substrate, and heating regions (56a, 56b, 56c) divided into a plurality of parts in the longitudinal direction are provided.

As shown in FIG. 2, the fixing member (fixing belt) 38 includes a base 43 and an elastic layer 44 that covers the surface of the base 43, and has a release layer 45 on the surface.
The base 43 has an outer diameter of about 40 mm and a thickness of about 50 to 100 μm. Examples of the material include a metal base such as nickel and SUS, and a resin base such as polyimide.
The elastic layer 44 has a thickness of about 50 to 300 μm, and examples of the material include silicon rubber.
The release layer 45 has a thickness of about 5 to 50 μm, and the material is not particularly limited as long as it can enhance the durability and ensure the release property. For example, fluorine such as PFA or PTFE can be used. Based resins and the like.

  A supporting member 61 is provided inside the fixing member 38, and a pressing member 60 and a pressing member 30 are provided at a portion where the fixing nip portion N is formed, and the fixing member 38 is connected to a side plate external member (not shown). I support it.

The pressure member 30 (30a, 30b) includes a cored bar 31 (41a, 41b) and an elastic layer 32 (42a, 42b) coated on the surface of the cored bar 31.
The pressure member 30a is a roller for reliably pressing the fixing member against the planar heater.
The pressure member 30b is a pressure roller that presses against the fixing member 38 by an urging unit (not shown) to form the fixing nip portion N.

The cored bar 31b constituting the pressure member 30b forming the fixing nip N has an outer diameter of about 40 mm and a thickness of about 2 mm, and the material is, for example, iron.
The elastic layer 32b has a thickness of about 5 mm, and examples of the material include silicon rubber.
A fluororesin layer having a thickness of about 40 μm is preferably formed on the surface of the elastic layer 32b in order to improve releasability.
The metal core 31a constituting the pressure member (pressure roller) 30a has an outer diameter of about 10 mm, and the material is, for example, iron.
The elastic layer 32a has a thickness of about 4 mm, and examples of the material include silicon rubber.
A fluororesin layer having a thickness of about 30 μm is preferably formed on the surface of the elastic layer 32a in order to improve releasability.

  In the rotation direction of the fixing member 38, in the region downstream of the fixing nip N and upstream of the heating means 56, the thermopile array 34 as a temperature detecting means for detecting the surface temperature of the fixing member 38 and the temperature of the heating means 56 are detected. A thermistor 36 is provided as a heating member temperature detecting means. Furthermore, a power source 40 that supplies power to the heating unit 56 and a heating control unit 42 that controls the power source 40 based on the detected temperature information are provided.

FIG. 5 shows a schematic diagram of the thermopile array 34.
As shown in FIG. 5, the thermopile array 34 has a plurality of channels in which a plurality of elements (341, 342, 343,...) For detecting temperature are arranged, and forms a viewing angle θ as a whole. With such a configuration, it is possible to detect temperatures at a plurality of locations on the surface of the fixing member 38.
The thermopile array 34 preferably has three or more channels. By having many channels, the surface temperature can be detected at finer intervals, and specifically, there are those having 3 to 16 channels.

  The heating control means 42 means a microcomputer including, for example, a CPU, ROM, RAM, and an I / O interface.

6A and 6B show the relationship between the arrangement positions of the fixing member 38 and the thermopile array 34 in the fixing device 12 of the present embodiment.
FIG. 6A and FIG. 6B show a half-length region including one end 38d in the longitudinal direction of the fixing member 38. The regions indicated by 38a, 38b, and 38c are as follows. The area | region heated corresponding to the division | segmentation heating area | region 56a, 56b, 56c of the heating means 56 shown in FIG. 3 is shown.
The temperature of the region indicated by 38a, 38b, 38c on the surface of the fixing member 38 is detected by the thermopile array 34, and the heating of the heating means 56 is controlled based on the detected temperature information.

In FIG. 6A, the reference line Ba for the viewing angle θa of the thermopile array 34 is the viewing angle reference line Ba. The viewing angle reference line Ba equally divides the viewing angle θa.
θ1a and θ1b are angles formed by the viewing angle reference line Ba and the fixing member rotation center R that is the rotation center of the fixing member 38, and the angle formed on the side close to the fixing member end 38d is represented by θ1a and the other is represented by θ2a. ing. That is, θ2a is an angle represented by (180 ° −θ1a).
In the embodiment of FIG. 6A, both θ1a and θ2a are 90 °.
The detection range of the surface of the fixing member 38 by the thermopile array 34 is indicated by Wa.
The distance between the thermopile array 34 and the fixing member 38 is indicated by Da.

FIG. 6B shows an aspect in which the thermopile array 34 is inclined with respect to the surface of the fixing member 38. The reference line for the viewing angle θb of the thermopile array 34 is the viewing angle reference line Bb. The viewing angle reference line Bb equally divides the viewing angle θb.
In FIG. 6B, θ1b <θ2b is established while the detection range Wb of the thermopile array 34 is maintained. Specifically, in this embodiment, θ1b = 73 ° and θ2b = 107 °.

  By arranging the thermopile array 34 so as to be inclined as shown in FIG. 6B, the distance Db between the thermopile array 34 and the fixing member 38 is significantly smaller than the distance Da in the embodiment of FIG. can do. This means that the thermopile array 34 can be disposed in a narrow mounting area.

  6B, the number of detections of the thermopile array 34 for the region 38a is increased from two to three, and the number of detections for the region 38b is also two. It has increased to three places. On the other hand, the number of detections for the region 38c is reduced from four to two. This means that the surface temperature in the vicinity of the end portion (region 38d) of the fixing member 38 can be detected with higher accuracy than in the central region.

  The problem of temperature rise on the non-sheet passing surface of the fixing member 38 and the problem of fixing failure due to insufficient heat quantity often occur near the end (region 38d) of the fixing member 38, so the surface near the end (region 38d). The embodiment shown in FIG. 6B where the temperature can be detected in more detail is more preferable.

By detecting the interval between the detection areas closely, it is possible to detect a local temperature rise of the fixing member, and it is possible to efficiently prevent the occurrence of temperature overshoot by implementing the idling mode.
As conditions for shifting to the idling mode, for example, the number of continuous conveyances of the recording material P to the fixing nip portion N (the number of printed sheets, the printing duration), and a threshold temperature can be set.
The rotation speed and rotation duration of the fixing member 38 and the pressure member 30 in the idling mode can be arbitrarily set. The longer the execution of the idling mode is, the higher the effect of preventing the temperature rise is. However, since the travel distance is increased by the rotation, there is a trade-off relationship from the viewpoint of the life of the member. Therefore, it is preferable to shift to the idling mode under appropriate conditions and set an appropriate rotation speed and rotation duration.

In addition, if the high temperature state is maintained due to heat accumulation of the internal member even after the idling rotation mode is performed and a preset rotation duration has elapsed, the temperature of the fixing member 38 is not sufficiently lowered again. Or the temperature may rise again.
Therefore, when the temperature of the surface of the fixing member 38 detected by the thermopile array 34 exceeds a predetermined value after a preset rotation duration time has elapsed, control is performed so that the idle rotation mode is executed again. Is preferred.

FIG. 4 shows a flow of execution of the idling mode in the fixing device 12 of the present embodiment.
First, the passing (conveying operation) of the recording material P to the fixing nip N is completed (S001).
Predetermined conditions for shifting to the idle rotation mode include the number of sheets to be passed, the sheet passing time, and the fixing member 38 surface temperature detected by the thermopile array 34.
First, it is determined whether or not a predetermined number of sheets (or sheet passing time) has been exceeded (S002), and if it exceeds, the idling rotation mode is executed with the set rotation speed and opening time (S003).
In step S002, when the predetermined number of sheets passed (or the sheet passing time) is not exceeded, and after the idling mode is performed in step S003, all the detected temperatures of all the channels of the thermopile array 34 are below the threshold temperature. It is determined whether or not (S004).
When at least one of the plurality of channels of the thermopile array 34 detects a temperature exceeding a predetermined value, the idling mode is executed again (S003).
On the other hand, when no temperature exceeding a predetermined value is detected in any of the plurality of channels of the thermopile array 34, the idling mode is terminated (S005).

  As described above, by efficiently shifting to and executing the idling mode, it is possible to prevent the temperature of the fixing member 38 from rising and the occurrence of temperature overshoot, and the volatile substance contained in the fixing member 38 can be prevented. And generation of harmful substances such as fine particles can be prevented.

DESCRIPTION OF SYMBOLS 4 Paper feed means 6 Registration roller pair 8 Photosensitive drum 10 Transfer means 11 Transfer site 12 Fixing device 30 Pressure member 34 Thermopile array 36 Thermistor 38 Fixing member 40 Power supply 42 Heating control means 56 Heating means N Fixing nip part P Recording material Paper)
T Unfixed image (toner image)

JP-A-6-95540 JP 2005-181946 A JP 2001-343860 A JP 2013-195862 A

Claims (7)

A fixing member that is heated by a heating unit, rotates in a predetermined direction, heats and melts an unfixed image, and fixes the image on a recording material;
A pressure member that rotates in a predetermined direction and presses against the fixing member to form a fixing nip portion;
A thermopile array having a plurality of channels and capable of detecting temperatures of a plurality of regions on the surface of the fixing member;
Heating control means for controlling heating by the heating means,
When the recording material is transported to the fixing nip portion, when the predetermined condition is satisfied, the fixing member and the pressure member are moved in a state where heating of the fixing member by the heating unit is stopped. A fixing device characterized in that an idling rotation mode is executed.   The idle rotation mode is executed when the temperature of the surface of the fixing member detected by the thermopile array exceeds a predetermined value after the conveyance operation of the recording material to the fixing nip portion is completed. The fixing device according to claim 1.   The fixing device according to claim 2, wherein the idling mode is executed when a temperature at which at least one of the plurality of channels of the thermopile array exceeds a predetermined value is detected.   4. The fixing device according to claim 1, wherein the idling mode is executed when a continuous conveyance number of the recording material to the fixing nip portion exceeds a predetermined value. 5.   5. The fixing device according to claim 1, wherein a rotation speed and a rotation duration time of the fixing member and the pressure member in the idling mode can be arbitrarily set.   In the idling mode, when the temperature of the surface of the fixing member detected by the thermopile array exceeds a predetermined value after a preset rotation duration time has elapsed, the idling mode is executed again. The fixing device according to claim 5.   An image forming apparatus comprising the fixing device according to claim 1.