JP6586483B2 - Fixing device - Google Patents

Description

This embodiment relates to the fixing equipment.

  Conventionally, as a heat source of a fixing device mounted in an image forming apparatus, a lamp emitting infrared rays such as a halogen lamp or a method of heating with Joule heat by electromagnetic induction has been put into practical use. These heating methods not only require time to warm the entire fixing device, but also require a lot of electric energy. In addition, heat generated in the fixing device is transmitted to other units in the image forming apparatus, causing problems.

  In recent years, shortening the start-up time of the apparatus, energy saving, prevention of excessive heat generation, and the like have become important issues. For this reason, two heating resistors having different resistance values are provided in the fixing device, and each heating resistor is connected to a different power input system, so that one heating resistor is always energized during the standby of the fixing device. Some have been preheated. With such a structure, an optimum temperature gradient is realized in the fixing nip while accommodating various sizes of recording paper, and good fixing characteristics can be obtained.

  However, in the above prior art device structure, when small size paper and large size paper are mixedly supplied, the power supply to the heater is finely controlled to the minimum necessary at both ends and the center. It was difficult to do.

JP 2000-243537 A

  In view of the above-described problems of the prior art, the present invention enables intensive and stable heating of a sheet passing area even when small-size paper and large-size paper are mixedly supplied. It is an object of the present invention to provide a fixing device and a fixing temperature control program for the fixing device that can achieve improvement and energy saving.

The fixing device of this embodiment is divided into an endless rotating body and an orthogonal direction perpendicular to the medium conveyance direction, and a plurality of openings are arranged along two or more parallel lines perpendicular to the conveyance direction. A heating resistance layer that is covered with a masking layer patterned in a pattern and exposed to the rotating body as a plurality of heating members in which exposed portions exposed from the plurality of openings form a two-dimensional array; and heating means for heating said in heating means to press-contact at the position of the plurality of heating members to form a nip, and a pressurizing means for holding and conveying the medium to the conveying direction together with said heating means, said opening , the relative direction perpendicular to the divided one heat generating resistor layer, a plurality of formed in the conveying direction, characterized in Rukoto.

1 is a diagram illustrating a configuration example of an image forming apparatus in which a fixing device according to a first embodiment is mounted. FIG. 2 is a configuration diagram illustrating an enlarged part of an image forming unit according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration example of a control system of the MFP according to the first embodiment. FIG. 3 is a diagram illustrating a configuration example of a fixing device according to the first embodiment. FIG. 3 is a layout view of a heat generating member group in the first embodiment. FIG. 3 is a top view illustrating a method for forming a heat generating member group in the first embodiment. FIG. 3 is a side view illustrating a method for forming a heat generating member group in the first embodiment. FIG. 6 is a layout view of another pattern of heat generating member groups in the first embodiment. FIG. 6 is a diagram illustrating simulation results of toner temperature on a sheet and surface temperature of a fixing belt. The figure which shows the simulation result of the surface temperature distribution according to the size of the exposed part of the heating resistor in a heating member, and the number. 6 is a flowchart illustrating a specific example of an MFP control operation according to the first exemplary embodiment. FIG. 6 is a top view illustrating an example of a heating pattern of a heat generating member group in the second embodiment. 10 is a flowchart illustrating a specific example of an MFP control operation according to the second exemplary embodiment.

<Embodiment 1>
FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus in which a fixing device according to the present embodiment is mounted. In FIG. 1, an image forming apparatus 10 is, for example, an MFP (Multi-Function Peripherals), a printer, a copier, or the like, which is a multifunction peripheral. In the following description, an MFP will be described as an example.

  A transparent glass platen 12 is provided above the main body 11 of the MFP 10, and an automatic document feeder (ADF) 13 is provided on the platen 12 so as to be freely opened and closed. An operation panel 14 is provided on the upper portion of the main body 11. The operation panel 14 has various keys and a touch panel type display unit.

  A scanner unit 15 serving as a reading device is provided below the ADF 13 in the main body 11. The scanner unit 15 generates image data by reading a document sent by the ADF 13 or a document placed on a document table, and includes a contact image sensor 16 (hereinafter simply referred to as an image sensor). The image sensor 16 is arranged in the main scanning direction (the depth direction in FIG. 1).

  When reading the image of the document placed on the document table 12, the image sensor 16 reads the document image line by line while moving along the document table 12. This is executed over the entire document size, and one page of document is read. Further, when reading an image of a document sent by the ADF 13, the image sensor 16 is in a fixed position (position shown in the drawing).

  Further, a printer unit 17 is provided at the center of the main body 11, and a plurality of paper feed cassettes 18 for storing various sizes of paper P are provided at the bottom of the main body 11. The printer unit 17 includes a photosensitive drum and a scanning head 19 including an LED as an exposure device, and scans the photosensitive member with light beams from the scanning head 19 to generate an image.

  The printer unit 17 processes image data read by the scanner unit 15 or image data created by a personal computer or the like to form an image on a sheet. The printer unit 17 is a tandem color laser printer, for example, and includes image forming units 20Y, 20M, 20C, and 20K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 20Y, 20M, 20C, and 20K are arranged below the intermediate transfer belt 21 in parallel from upstream to downstream. The scanning head 19 also has a plurality of scanning heads 19Y, 19M, 19C, and 19K corresponding to the image forming units 20Y, 20M, 20C, and 20K.

  FIG. 2 is an enlarged configuration diagram illustrating the image forming unit 20K among the image forming units 20Y, 20M, 20C, and 20K. In the following description, since the image forming units 20Y, 20M, 20C, and 20K have the same configuration, the image forming unit 20K will be described as an example.

  The image forming unit 20K includes a photosensitive drum 22K that is an image carrier. A charging charger 23K, a developing device 24K, a primary transfer roller (transfer device) 25K, a cleaner 26K, a blade 27K, and the like are arranged around the photosensitive drum 22K along the rotation direction t. The exposure position of the photosensitive drum 22K is irradiated with light from the scanning head 19K to form an electrostatic latent image on the photosensitive drum 22K.

  The charging charger 23K of the image forming unit 20K uniformly charges the surface of the photosensitive drum 22K. The developing device 24K supplies a two-component developer containing black toner and a carrier to the photosensitive drum 22K by a developing roller 24a to which a developing bias is applied, and develops the electrostatic latent image. The cleaner 26K removes residual toner on the surface of the photosensitive drum 22K using the blade 27K.

  As shown in FIG. 1, a toner cartridge 28 that supplies toner to the developing devices 24Y to 24K is provided above the image forming units 20Y to 20K. The toner cartridge 28 includes toner cartridges of yellow (Y), magenta (M), cyan (C), and black (K).

  The intermediate transfer belt 21 moves cyclically. The intermediate transfer belt 21 is stretched around a driving roller 31 and a driven roller 32. The intermediate transfer belt 21 is in contact with the photosensitive drums 22Y to 22K. A primary transfer voltage is applied to the position of the intermediate transfer belt 21 facing the photosensitive drum 22K by the primary transfer roller 25K, and the toner image on the photosensitive drum 22K is primarily transferred to the intermediate transfer belt 21.

  A secondary transfer roller 33 is disposed opposite to the drive roller 31 that stretches the intermediate transfer belt 21. When the paper P passes between the driving roller 31 and the secondary transfer roller 33, a secondary transfer voltage is applied to the paper P by the secondary transfer roller 33. Then, the toner image on the intermediate transfer belt 21 is secondarily transferred to the paper P. A belt cleaner 34 is provided near the driven roller 32 of the intermediate transfer belt 21.

  Further, as shown in FIG. 1, a paper feed roller 35 for conveying the paper P taken out from the paper feed cassette 18 is provided between the paper feed cassette 18 and the secondary transfer roller 33. Further, a fixing device 36 is provided downstream of the secondary transfer roller 33. Further, a conveyance roller 37 is provided downstream of the fixing device 36. The conveyance roller 37 discharges the paper P to the paper discharge unit 38. Further, a reverse conveyance path 39 is provided downstream of the fixing device 36. The reverse conveyance path 39 reverses the paper P and guides it in the direction of the secondary transfer roller 33, and is used when performing duplex printing.

  1 and 2 show an example of the embodiment of the present invention. The structure of the image forming apparatus other than the fixing device 36 is not limited, and the structure of a known electrophotographic image forming apparatus may be used. it can.

  FIG. 3 is a block diagram illustrating a configuration example of the control system 50 of the MFP 10 according to the first embodiment. The control system 50 includes, for example, a CPU 100 that controls the entire MFP 10, a read only memory (ROM) 120, a random access memory (RAM) 121, an interface (I / F) 122, an input / output control circuit 123, a paper feed / conveyance control circuit. 130, an image formation control circuit 140, and a fixing control circuit 150.

  The CPU 100 realizes a processing function for image formation by executing a program stored in the ROM 120 or the RAM 121. The ROM 120 stores a control program and control data for performing basic operations of the image forming process. The RAM 121 is a working memory. The ROM 120 (or RAM 121) stores, for example, control programs such as the image forming unit 20 and the fixing device 36 and various control data used by the control programs. Specific examples of the control data in the present embodiment include the correspondence between the paper size and the heating member to be energized, the basis weight of the sheet detected by various sensors in the MFP 10, the surface temperature of the heating member, the value of the outside air temperature, and the like. The correspondence with the heat generating member to be energized can be mentioned.

  The fixing temperature control program of the fixing device 36 includes determination logic for determining the size, thickness and basis weight of the paper, the surface temperature of the heating member, the value of the outside air temperature and the like based on the detection signal of the sensor in the MFP 10. And a heating control logic for selecting a heat generating member corresponding to the position through which the sheet passes and energizing by control of the drive IC to control heating in the heating means. Specific examples of driving that is the switching unit of the heat generating member include a switching element, FET, triax, and switching IC.

  The I / F 122 performs communication with various apparatuses such as a user terminal and a facsimile. The input / output control circuit 123 controls the operation panel 123a and the display 123b. The paper feed / conveyance control circuit 130 controls a motor group 130a or the like that drives the paper feed roller 35 or the conveyance roller 37 in the conveyance path. The paper feed / conveyance control circuit 130 controls the motor group 130a and the like in consideration of detection results of various sensors 130b in the vicinity of the paper feed cassette 18 or on the conveyance path based on a control signal from the CPU 100. The image formation control circuit 140 controls the photosensitive drum 22, the charger 23, the scanning head 19, the developing device 24, and the transfer device 25 based on a control signal from the CPU 100. The fixing control circuit 150 controls the driving motor 360 of the fixing device 36, the heating member 361, and the temperature detection member 362 such as the thermistor based on the control signal from the CPU 100. In the present embodiment, the control program and control data of the fixing device 36 are stored in the storage device of the MFP 10 and executed by the CPU 100. However, the arithmetic processing device and the storage device are separately provided exclusively for the fixing device 36. May be.

  FIG. 4 is a diagram illustrating a configuration example of the fixing device 36. Here, the fixing device 36 is formed with a plate-like heating member 361, an elastic layer, an endless belt 363 suspended from a plurality of rollers, a belt conveying roller 364 for driving the endless belt 363, and an endless belt 363. A tension roller 365 and a press roller 366 having an elastic layer formed on the surface thereof are provided. The heating member 361 is in contact with the inside of the endless belt 363 on the heat generating portion side and is pressed in the direction of the press roller 366, thereby forming a fixing nip having a predetermined width with the press roller 366. Since the heating member 361 heats while forming the nip region, the responsiveness at the time of energization is higher than in the case of the heating method using a halogen lamp.

  The endless belt 363 has, for example, a silicon rubber layer having a thickness of 200 μm formed on the outer surface of a polyimide that is a 50 μm thick SUS base material or a 70 μm heat-resistant resin, and the outermost periphery is covered with a surface protective layer such as PFA. . In the press roller 366, for example, a silicon sponge layer having a thickness of 5 mm is formed on the surface of an iron rod having a diameter of 10 mm, and the outermost periphery is covered with a surface protective layer such as PFA.

  FIG. 5 is a layout view of the heat generating member group in the present embodiment. The heating member 361 has three lengths of heat generating members so as to correspond to a postcard size (100 × 148 mm), a CD jacket size (121 × 121 mm), a B5R size (182 × 257 mm), and an A4R size (210 × 297 mm). It is divided into (heat generating elements) and classified into three heat generating member groups. The heating member group is energized so as to have a margin of about 5% in the heating area in consideration of the conveyance accuracy of the conveyed sheet, skew, and heat escape to the non-heated portion.

  In the example of FIG. 5, in order to correspond to a postcard size width of 100 mm, which is the minimum size, a first heating member group is provided at the center in the main scanning direction (the left-right direction in the figure), and the width is 105 mm. In order to correspond to the next largest size of 121 mm and 148 mm, a second heat generating member group having a width of 25 mm × 2 is provided outside the first heat generating member group (horizontal direction in the figure), and covers a width of 148 mm + 5% up to 155 mm. To do. In order to cope with larger sizes 182 mm and 210 mm, a third heat generating member group having a width of 32.5 mm × 2 is provided on the outer side of the second heat generating member group, and 210 mm + 5% up to 220 mm. Cover the width.

  In addition, the division | segmentation number and each width | variety of a heat generating member group are mentioned as an example, and are not limited to this. For example, when the MFP 10 supports five medium sizes, the heat generating member group may be divided into five according to each medium size.

  In the present embodiment, it is assumed that a line sensor (not shown) is arranged in the sheet passing area so that the size and position of the passing sheet can be determined in real time. A configuration may be adopted in which the paper size is determined from image data or information of the paper feed cassette 18 in which paper is stored in the MFP 10 at the start of the printing operation.

  6 and 7 are a top view and a side view for explaining a method of forming the heat generating member group in the first embodiment. As shown in FIGS. 6A and 7A, in the heating member 361, a glaze layer (not shown) and a heating resistance layer (361b, 361c, 361d) are stacked on a ceramic substrate 361a. The heating resistance layers (361b, 361c, 361d) are made of a known material such as TaSiO 2. An aluminum heat sink 361e is bonded to the lower side of the ceramic substrate 361a in order to release excess heat to the opposite side and prevent the substrate from warping.

  Next, as shown in FIG. 7B, an aluminum layer 361f is formed in a pattern in which adjacent heat generating members are insulated and a plurality of heat generating resistors are exposed along the paper transport direction. The heat generation resistance layer is divided by the formation of the aluminum layer 361f, and is divided into a predetermined length and number in the main scanning direction and the sheet conveyance direction, and the exposed portions form a two-dimensional array. This exposed portion becomes a heat generating member. In addition, the width of each exposed portion in the transport direction is narrower than the width in the transport direction of the portion masked by the aluminum layer 361f.

  Next, in order to energize all the exposed portions (heat generating members) of the plurality of heating resistors arranged in the transport direction simultaneously, as shown in FIG. 7C, the wiring 361g is connected to the aluminum layers 361f at both ends, and Connected to a driving IC (switching driver IC) 151. A protective layer 361h is formed on the top so as to cover all of the heating resistor layers (361b, 361c, 361d), the aluminum layer 361f, the wiring 361g, and the like. The protective layer 361h is formed of, for example, Si3N4. 5 and 6, the method of forming the heat generating member in the case of center-aligned paper conveyance has been described. However, the same applies to the case of forming on one side corresponding to paper conveyance as shown in FIG.

  FIG. 9 is a diagram showing thermal simulation results of the toner temperature on the paper and the surface temperature of the fixing belt (endless belt 363). Here, the result of simulating the fixing condition when using the toner mounted on the MFP whose toner fixing temperature range is 80 ° C. to 130 ° C. is shown. If the process speed of the printing apparatus is 120 mm / sec and the heating member width (= fixing nip width) is 10 mm, the heating time of the recording material on which the unfixed toner is placed is about 83 msec. Further, under conditions for forming a full-color and high-density image, for example, the toner layer thickness is 20 μm at the maximum, and in the case of a thick recording material such as a tack sheet, the thickness is 270 μm, for example.

  Assuming that the entire surface of the heating member 361 is heated to a uniform temperature under the above-mentioned conditions, the belt surface temperature reaches 160 ° C. in about 3 seconds from the start of energization (POWER ON), and the recording at 25 ° C. It can be seen that when the material (toner particles) is heated in the 83 msec nip, the temperature of the portion where the toner contacts the recording paper (= toner interface) reaches a fixable temperature of 80 ° C. or higher. Since the heating rate of this portion is determined by the material and thickness of the recording material, the heating time cannot be shortened by reducing the nip (= the width of the heating member) in order to reduce the size of the apparatus. Further, as can be seen from the fact that the belt back surface temperature has risen to 200 ° C., since the heating member 361 is in direct contact with the back of the belt, heating only the vicinity of the nip portion raises the fixing nip portion to the required temperature. The time required to make it very short. On the other hand, when an elastic layer is formed on the belt surface, a temperature gradient is generated on the front surface and the back surface of the belt, and the temperature of the back surface is considerably higher than that of the front surface. The elastic layer cannot be eliminated in order to increase the adhesion between the belt surface and the recording material (toner particles) and efficiently transfer heat. In addition, in order to prevent thermal degradation of the elastic layer, heating conditions such that the back surface becomes high temperature are not appropriate. Therefore, in this embodiment, fixing is performed under heating conditions in which the toner interface temperature is 80 ° C. or higher and the belt back surface temperature is 220 ° C. or lower, which is the heat resistant upper limit temperature of the elastic layer.

  FIG. 10 is a diagram illustrating a thermal simulation result of the surface temperature distribution according to the size and the number of exposed portions of the heating resistors in the heating member 361. Here, in order to determine how the heating resistor (exposed portion) should be arranged on the surface of the heating member 361, the temperature uniformity of the heating member surface is calculated by changing the size of the heating resistor. . When there is one heating resistor of 80 um in the center, the surface temperature of the heating member 361 is 170 ° C. maximum and 110 ° C. minimum at about 1.4 seconds after energization start (POWER ON), and the temperature difference is I understand that it is serious. In addition, even if the width of the heating resistor is increased to 3 mm, the temperature non-uniformity is not eliminated if there is only one heating resistor. However, it can be seen that even if the heating resistor width is 80 um, the temperature non-uniformity is considerably improved by arranging a plurality of the heating member surfaces at intervals. For this reason, it is effective to arrange a plurality of heat generating members along the conveying direction.

  Hereinafter, the printing operation of the MFP 10 configured as described above will be described with reference to the drawings. FIG. 11 is a flowchart illustrating a specific example of control of the MFP 10 according to the first embodiment.

  First, when the scanner unit 15 reads image data (Act 101), the image forming control program in the image forming unit 20 and the fixing temperature control program in the fixing device 36 are executed in parallel.

  When the image forming process is started, the read image data is processed (Act 102), an electrostatic latent image is written on the surface of the photosensitive drum 22 (Act 103), and the developing unit 24 develops the electrostatic latent image. (Act 104), the process proceeds to Act 114.

  On the other hand, when the fixing temperature control process is started, the paper size is determined based on the detection signal of the line sensor (not shown) (Act 105), and the heat generating member group arranged at the position where the paper P passes is heated. A target is selected (Act 106). For example, when the paper P is the minimum size (postcard size), the first heating member group arranged at the center is selected, and as the size of the paper P increases, the second heating member group, third These heating member groups are selected together with the first heating member group.

  Next, when the temperature control start signal for the heat generating member group selected in Act 106 is turned ON (Act 107), the selected heat generating member group is energized and the surface temperature of the heat generating member group rises.

  Next, when the surface temperature of the heat generating member group is detected by a temperature detecting member (not shown) disposed inside or outside the endless belt 363 (Act 108), whether the surface temperature of the heat generating member group is within a predetermined temperature range. It is determined whether or not (Act 109). If it is determined that the surface temperature of the heat generating member group is within the predetermined temperature range (Act109: Yes), the process proceeds to Act110. On the other hand, when it is determined that the surface temperature of the heat generating member group is not within the predetermined temperature range (Act 109: No), the process proceeds to Act 111.

  In Act 111, it is determined whether or not the surface temperature of the heat generating member group exceeds a predetermined temperature upper limit value. Here, when it is determined that the surface temperature of the heat generating member group exceeds the predetermined temperature upper limit value (Act 111: Yes), the power supply to the heat generating member group selected in Act 106 is turned off (Act 112). Return to Act108. On the other hand, when it is determined that the surface temperature of the heating member group does not exceed the predetermined temperature upper limit value (Act111: No), the surface temperature is less than the predetermined temperature lower limit value based on the determination result of Act109. Therefore, the energization of the heat generating member group is maintained in the ON state or is turned ON again (Act 113), and the process returns to Act 108.

  Next, when the sheet P is transported to the transfer section in a state where the surface temperature of the heat generating member group is within a predetermined temperature range (Act 110), after the toner image is transferred to the sheet P (Act 114), the sheet P is fixed to the fixing device. It is conveyed into 36.

  Next, when the toner image is fixed on the paper P in the fixing device 36 (Act 115), it is determined whether or not the printing process of the image data is finished (Act 116). If it is determined that the printing process is to be terminated (Act 116: Yes), the power supply to all the heat generating member groups is turned off (Act 117), and the process is terminated. On the other hand, if it is determined that the image data printing process has not yet ended (Act 116: No), that is, if there remains image data to be printed, the process returns to Act 101, and the same process is repeated until the end. .

  As described above, in the fixing device 36 according to the present embodiment, the heating resistors (heating members) constituting the heating member 361 are arranged along two or more parallel lines in the vertical direction (main scanning direction) of the sheet conveyance direction. In addition, the heat generating member groups that are divided at common points on the parallel lines to form a two-dimensional array in the paper conveyance direction and the main scanning direction and are arranged in the paper conveyance direction are controlled to be energized at the same timing. As shown in FIG. 10, since the heat generating members are heated at a plurality of locations separated by a certain distance along the conveying direction, the temperature during heating can be adjusted uniformly, and as a result, the fixing quality can be improved. it can. Even when printing with a mixture of small and large paper, switching the heat generation area based on the size of the paper to be printed can prevent abnormal heat generation in the non-sheet passing area. In addition, since the wasteful heating of the non-sheet passing portion can be suppressed, the heat energy consumed by the fixing device 36 can be significantly reduced. Furthermore, since the concentrated and stable heating can be performed on the printed portion, the fixing quality can be improved.

<Embodiment 2>
Hereinafter, the fixing device 36 according to the second embodiment will be described with reference to the drawings. The configuration of the MFP 10 in the present embodiment is substantially the same as that in the first embodiment, and the same reference numerals as those in the first embodiment also indicate the same object. Below, it demonstrates centering on a different location from Embodiment 1. FIG.

  FIG. 12 is a layout diagram of a heat generating member group in the second embodiment. Here, two energization patterns when the paper size is B5R size (182 × 257 mm) are illustrated. In (A), the first heat generating member group and the second heat generating member group are all energized and are in a fully lit state. On the other hand, in the case of (B), the second line is controlled to be de-energized and is in a 2/3 lighting state. Control such as (B) is performed, for example, when the thickness of the paper to be used is thinner than that of the normal type paper or when the surface temperature of the heat generating member group is sufficiently high. Unlike the case of the first embodiment, the energization of each heat generating member is controlled individually, not in units of groups arranged in the paper transport direction.

  Hereinafter, the printing operation of the MFP 10 in the present embodiment will be described with reference to the drawings. FIG. 13 is a flowchart illustrating a specific example of control of the MFP 10 according to the second embodiment.

  First, when the scanner unit 15 reads image data (Act 201), the image forming control program in the image forming unit 20 and the fixing temperature control program in the fixing device 36 are executed in parallel.

  When the image forming process is started, the read image data is processed (Act 202), an electrostatic latent image is written on the surface of the photosensitive drum 22 (Act 203), and the developing unit 24 develops the electrostatic latent image. (Act 204), the process proceeds to Act 214.

  On the other hand, when the fixing temperature control process is started, the paper size and the paper thickness are respectively determined based on detection signals of a line sensor (not shown) and a sound wave sensor (not shown) (Act 205). Based on the size and the thickness of the paper, a heat generating member to be heated is selected from a group of heat generating members arranged at a position where the paper P passes (Act 206). For example, when the paper P is the minimum size (postcard size), the first heating member group arranged at the center is selected. As the size of the paper P increases, a second heat generating member group and a third heat generating member group are added. In addition, even if the paper size is the same, based on the thickness of the paper, the normal or thick paper type is fully lit, and the thin paper is 1/3 or 2/3. The heating member to be de-energized in the same group is determined as appropriate. It is preferable to predefine control conditions for deenergization in a storage device such as the MFP 10. The thickness of the sheet may be determined and selected by the user himself / herself from the user interface without having a sensor for judging.

  Next, when the temperature control start signal to the heat generating member group selected in Act 206 is turned ON (Act 207), the selected heat generating member group is energized and the surface temperature of the heat generating member group rises.

  Next, when the surface temperature of the heat generating member group is detected by a temperature detecting member (not shown) disposed inside or outside the endless belt 363 (Act 208), whether the surface temperature of the heat generating member group is within a predetermined temperature range. It is determined whether or not (Act 209). If it is determined that the surface temperature of the heat generating member group is within the predetermined temperature range (Act 209: Yes), the process proceeds to Act 210. On the other hand, when it is determined that the surface temperature of the heat generating member group is not within the predetermined temperature range (Act 209: No), the process proceeds to Act 211.

  In Act 211, it is determined whether or not the surface temperature of the heat generating member group exceeds a predetermined temperature upper limit value. Here, when it is determined that the surface temperature of the heat generating member group exceeds the predetermined temperature upper limit value (Act 211: Yes), the power supply to the heat generating member group selected in Act 206 is turned off (Act 212). Return to Act 208. On the other hand, when it is determined that the surface temperature of the heat generating member group does not exceed the predetermined temperature upper limit value (Act 211: No), the surface temperature is less than the predetermined temperature lower limit value based on the determination result of Act 209. Therefore, the energization of the heat generating member group is maintained in the ON state, or is turned ON again (Act 213), and the process returns to Act 208. In Act 212 and Act 213, in order to adjust the temperature increase rate and the temperature decrease rate, the ratio of the heat generating member to be turned ON / OFF in the heat generating member group to be controlled is the difference between the surface temperature of the heat generating member group and the fixing temperature. It can also be appropriately changed according to the difference value. For example, when the temperature difference is slightly low, it is preferable to control energization so that the lighting is 1/3 instead of full lighting.

  Next, when the sheet P is transported to the transfer unit in a state where the surface temperature of the heat generating member group is within a predetermined temperature range (Act 210), after the toner image is transferred to the sheet P (Act 214), the sheet P is fixed to the fixing device. It is conveyed into 36.

  Next, when the toner image is fixed on the paper P in the fixing device 36 (Act 215), it is determined whether or not the printing process of the image data is finished (Act 216). If it is determined that the printing process is to be terminated (Act 216: Yes), the power supply to all the heat generating member groups is turned off (Act 217), and the process is terminated. On the other hand, if it is determined that the image data printing process has not yet ended (Act 216: No), that is, if there remains image data to be printed, the process returns to Act 201, and the same process is repeated until the end. .

  As described above, according to the fixing device 36 according to the present embodiment, the heat generating member to be energized is selected from the heat generating member group corresponding to the position where the paper passes based on the paper size and the paper thickness. Since the configuration is such that energization is controlled more finely than in the above case, it is possible to suppress excessive heating of the paper and to save energy compared to the case of the first embodiment.

  In the above embodiment, the length and material of the heat generating member group in the paper transport direction are uniform. However, for example, the heat generating member arranged on the upstream side in the transport direction with respect to the same energization amount is more downstream than the downstream side. In order to heat to a high temperature, the length, thickness, and material of each heat generating member can be changed.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, the configurations of the first embodiment and the second embodiment may be combined. That is, in the second embodiment, the heating member group can be selected based on the size of the print size (image forming area) as in the first embodiment instead of the paper size.

36... Fixing device 150... Fixing device control circuits 151, 151 a, 151 b, 151 c and 151 d... Driving IC (switching element)
361 ... heating member 361a ... heating member 362b ... electrode 363 ... endless belt 366 ... pressure roller

Claims (4)

An endless rotating body and a masking layer that is divided into a perpendicular direction perpendicular to the conveyance direction of the medium and patterned in a pattern in which a plurality of openings are arranged along two or more parallel lines perpendicular to the conveyance direction A heating resistance layer that is in contact with the rotating body as a plurality of heat generating members that are exposed by the plurality of openings and that are exposed from the plurality of openings, and heating the medium; and
A pressure unit that press-contacts the heating unit at the positions of the plurality of heat generating members to form a nip, and holds and conveys the medium in the conveyance direction together with the heating unit;
A plurality of the openings are formed in the transport direction with respect to one heating resistance layer divided in the orthogonal direction.   2. The fixing device according to claim 1, further comprising: a switching unit that selects the heat generating member in units of groups of the plurality of heat generating members grouped for each of the divided heat generating resistance layers and switches energization.   The masking layer of the divided heating resistance layer is connected to the switching unit by wiring connected to the upstream end of the masking layer in the transport direction and the downstream end of the masking layer in the transport direction. The fixing device according to claim 2.   The fixing device according to claim 1, wherein a length of the divided heating resistance layer in the orthogonal direction is based on a size of a medium.

Images