JP7210675B2 - Fixing device - Google Patents

Description

Embodiments of the present invention relate to fixing devices.

The fixing device heats the paper with a heater to fix the toner. A heater in which a plurality of heating elements are arranged on a ceramic substrate is known. A plurality of heating elements are grouped in the longitudinal direction of the substrate to form a heating element group. Reference 1).

Heater temperature unevenness affects fixing quality (see, for example, Patent Document 2). Especially in the case of color printing, there is a possibility that a difference in color development and gloss may occur. However, in the case of a heater that heats each heating element group, there is a problem that it is difficult to accurately grasp the belt surface temperature of each heating element group, and it is difficult to make the belt surface temperature uniform. .

JP 2015-219417 A JP-A-2008-15235

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, reduce the temperature unevenness in the longitudinal direction of the heater substrate, and provide a fixing device capable of highly accurate temperature control.

In order to achieve the above object, the fixing device of this embodiment includes a rotating endless belt, a heater, and a pressure member. The heater is divided in the direction of the axis of rotation of the belt into a plurality of mutually insulated heater blocks having a first spacing gap, and each heater block is divided into a plurality of heater cells having a second spacing gap. It has a heat-generating region and is arranged in contact with the inner side of the belt. The pressurizing body is arranged at a position facing the heater with the belt interposed therebetween so as to press the paper to be conveyed. One surface of the heater is formed on one surface of the substrate and electrodes are formed on the other surface of the heater. A temperature sensor is provided at each position corresponding to each heater cell on the other surface of the substrate where the heater is not formed. The width of the second spacing gap is narrower than the width of the first spacing gap.

1 is a configuration diagram of an image forming apparatus including a fixing device according to an embodiment; FIG. 2 is a block diagram showing the control system of the image forming apparatus according to the embodiment; FIG. 1 is a configuration diagram showing an example of a fixing device according to an embodiment; FIG. The top view which shows an example of the heater which concerns on embodiment. Sectional drawing which shows an example of the heater which concerns on embodiment. FIG. 4 is an explanatory view showing the heater structure when the heater block is not divided into heater cells; FIG. 4 is a temperature distribution diagram of the heater when the heater block is not divided into heater cells; FIG. 4 is an explanatory view showing the heater structure when the heater block is divided into heater cells; FIG. 4 is a temperature distribution diagram of the heater when the heater block is divided into heater cells; FIG. 5 is an explanatory diagram showing the relationship between the heater cell separation gap and the temperature ripple; FIG. 4 is a flow chart diagram showing an example of a heater design method and an adjustment method.

Hereinafter, embodiments will be described in detail with reference to FIGS. 1 to 11. FIG. In the following description, components having substantially the same functions and configurations are denoted by the same reference numerals, and redundant description will be given only when necessary.

In FIG. 1, an image forming apparatus 10 is, for example, an MFP (Multi-Function Peripherals), a printer, a copier, or the like. In the following description, an MFP is used as an example.

A document platen 12 made of transparent glass is provided on the upper portion of a main body 11 of the image forming apparatus 10, and an ADF (Auto Document Feeder) 13 is provided on the document platen 12 so as to be freely opened and closed. An input/output control section 14 is provided on the upper portion of the main body 11 . The input/output control unit 14 has an operation panel 14a having various keys for operating the image forming apparatus 10 and a touch panel type display unit 14b.

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

When reading the image of the document placed on the document platen 12 , the image sensor 16 moves along the document platen 12 and reads the document image line by line. This is executed over the entire document size to read one page of the document. Further, when reading an image of a document fed by the ADF 13, the image sensor 16 is at a fixed position (position shown in the drawing). The main scanning direction is a direction perpendicular to the moving direction of the image sensor 16 when it moves along the document platen 12 (the depth direction in FIG. 1).

Further, a printer section 17 is provided in the central portion within the main body 11 . The printer unit 17 processes image data read by the scanner unit 15 or image data created by a personal computer or the like, and forms an image on a recording medium (for example, paper). Further, a plurality of paper feed cassettes 18 containing paper of various sizes are provided in the lower portion of the main body 11 (two paper feed cassettes 18a and 18b are shown in FIG. 1). In addition to paper, an OHP sheet or the like is used as a recording medium for forming an image. In the following description, an example of forming an image on paper will be described.

The printer unit 17 has scanning heads 19Y, 19M, 19C, and 19K including LEDs or lasers as exposing devices for yellow (Y), magenta (M), cyan (C), and black (K). A beam of light from each scanning head 19 of the device is scanned to produce an image on the photoreceptor. The printer unit 17 is, for example, a color laser printer based on the pattern beam method, and is composed of image forming units 20Y, 20M, 20C, and 20K for respective colors. The image forming units 20Y to 20K are arranged in parallel under the intermediate transfer belt 21 from upstream to downstream.

The intermediate transfer belt 21 is stretched around a drive roller 31 and a driven roller 32 and moves cyclically. The intermediate transfer belt 21 faces and contacts the photosensitive drums 22Y, 22M, 22C, and 22K.

Since the image forming units 20Y to 20K for each color have the same configuration, taking the image forming unit 20K as an example, a charging device 23K, a developing device 24K, a primary transfer roller 25K, etc. are arranged around the photosensitive drum 22K. ing. 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 charger 23K uniformly charges the surface of the photosensitive drum 22K. The developing device 24K develops the electrostatic latent image by supplying black toner to the photosensitive drum 22K through a developing roller to which a developing bias is applied.

Further, above the image forming units 20Y to 20K, toner cartridges (not shown) for supplying toner to the developing devices 24Y to 24K are provided. A primary transfer voltage is applied by a primary transfer roller 25K to a position of the intermediate transfer belt 21 facing the photoreceptor drum 22K, and the toner image on the photoreceptor drum 22K is primarily transferred to the intermediate transfer belt 21. FIG.

A drive roller 31 on which the intermediate transfer belt 21 is stretched is arranged to face a secondary transfer roller 33 . A secondary transfer voltage is applied to the paper P by the secondary transfer roller 33 when the paper P passes between the drive roller 31 and the secondary transfer roller 33 . Then, the toner image on the intermediate transfer belt 21 is secondarily transferred onto the paper P. A belt cleaner 34 is provided near the driven roller 32 of the intermediate transfer belt 21 .

Further, a paper feed roller 35 for conveying the paper P taken out from the paper feed cassette 18 is provided on the transport path from the paper feed cassette 18 to the secondary transfer roller 33 . Furthermore, a fixing device 36 as a heating device is provided downstream of the secondary transfer roller 33 . Further, a transport roller 37 is provided downstream of the fixing device 36, and the paper P is discharged to the paper discharge section 38 by the transport roller 37. As shown in FIG. Also, the image forming apparatus 10 is integrally controlled by the system control unit 39 .

In addition, the size and position of the transported paper can be determined in real time using the line sensor 40 arranged in the paper passing area.

The fixing device 36 of this embodiment will be described later in detail. Note that FIG. 1 is an example of the embodiment, and the present invention is not limited to this example, and the structure of a known electrophotographic image forming apparatus can be used.

FIG. 2 is a block diagram showing a configuration example of the control system of the image forming apparatus 10 according to the embodiment. The control system of the image forming apparatus 10 is formed by the system control unit 39 , the input/output control unit 14 , the paper feed/conveyance control unit 130 , the image formation control unit 140 , and the fixing control unit 150 , which are interconnected by the bus line 110 . It is

The system control unit 39 includes, for example, a CPU 100 that controls the entire image forming apparatus 10 , a read only memory (ROM) 120 , a random access memory (RAM) 121 and an interface (I/F) 122 .

The CPU 100 executes the programs stored in the ROM 120 or RAM 121 to implement overall control of the apparatus, including image formation control and fixing temperature control. The ROM 120 stores control programs and control data for image formation control and fixing temperature control. A RAM 121 is mainly used as a working memory for controlling the entire apparatus.

The ROM 120 (or RAM 121) stores, for example, control programs for the image forming section 20, the fixing device 36, etc., and various control data used by the control programs. The I/F 122 communicates with various devices such as user terminals and facsimiles.

The input/output control unit 14 controls the operation panel 14 a connected to the input/output control circuit 123 , the display unit 14 b and the scanner unit 15 . The operator can operate the operation panel 14a to specify, for example, the paper size, the number of copies of the document, and the like. The display unit 14b displays the operating state of the image forming apparatus 10 and the like.

The paper feed/conveyance control unit 130 includes a paper feed/conveyance control circuit 131, a motor group 132, and a sensor group 133, and executes control of paper feeding and paper conveyance. The paper feed/conveyance control circuit 131 controls a motor group 132 and the like for driving the paper feed roller 35 or the convey roller 37 on the conveying path. In addition, the paper feed/conveyance control circuit 131 controls the motor group 132 and the like based on the control signal from the CPU 100, depending on the detection results of various sensors 133 near the paper feed cassette 18 or on the conveyance path.

The image forming control unit 140 controls the photosensitive drum 22, the charger 23, the exposure device (scanning head) 19, the developing device 24, and the transfer device (transfer roller) 25 based on control signals from the CPU 100. It is composed of a circuit 141 and executes control of image formation.

The fixing control unit 150 includes a motor 151 constituting the fixing device 36, a heater 152 for heating, various temperature sensors 153 for detecting temperature, and a fixing control circuit 154 for safety control such as fixing temperature control and prevention of excessive temperature rise. and performs fixing control.

FIG. 3 is a configuration diagram showing an example of a fixing device. As shown in FIG. 3 , the fixing device 36 includes an endless belt 53 having a belt surface 51 and a belt back surface 52 and a pressure roller (pressure member) 54 facing the belt 53 . The pressure roller 54 is rotated in the arrow T direction by a driving force transmitted by a motor (not shown).

The endless belt 53 is formed of, for example, a 40 μm-thick Ni (nickel) base material or a 70 μm-thick polyimide heat-resistant resin base material, and a silicone rubber layer having a thickness of about 200 μm is formed on the outer side of the base material. It is coated with a protective layer such as The pressure roller 54 is formed by forming a silicone sponge layer of about 5 mm thickness on the surface of, for example, a φ10 mm iron bar, and the outer periphery thereof is coated with a protective layer such as PFA.

Further, the fixing device 36 is provided with a heater 152 for raising the temperature, which contacts the belt back surface 52 in the rotation axis direction (belt width direction) of the belt 53 . The endless belt 53 rotates in the direction of arrow S while forming a fixing nip width N between itself and the pressure roller 54 . When the paper P passes through the fixing nip portion in the direction of arrow A, the toner image 55 on the paper P is fixed to the paper P by the heat generated by the heater 152 and the pressure at the fixing nip portion.

There are various methods for the various temperature sensors 153 that detect the fixing temperature. FIG. 3 shows a temperature sensor 56 arranged on the rear surface of the heater 152, a temperature sensor 57 arranged on the belt rear surface 52 for detecting the temperature of the belt rear surface, and a temperature sensor 58 arranged on the belt surface 51 for measuring the temperature of the belt surface. ing. Since the temperature sensors 57 and 58 must be arranged on the circumference of the belt 53 away from the fixing nip portion, it is necessary to correct the temperature accompanying the circumference of the belt 53 . Moreover, the temperature sensor 58 is preferably non-contact so as not to damage the belt 53 . The fixing device 36 is controlled by a fixing control circuit 154 .

In fixing temperature control, these temperature sensors 56, 57, and 58 can be appropriately selected, or a plurality of types can be used together. In addition, as will be described later, a heater block whose temperature is to be controlled is selected according to the width of the paper to be transported and the transport position. Become.

FIG. 4 is a plan view showing an example of a heater, and FIG. 5 is a sectional view thereof. The heater 152 is divided into a plurality of heater blocks symmetrically with respect to a heater center line (B-B') indicated by a chain double-dashed line. In this embodiment, an example of dividing into 7 is shown. Of course, the number of divisions is arbitrary. That is, the number of divisions of the heater block and the block width can be freely selected and set according to the corresponding paper size or the image forming area excluding the margin. Further, when the transport position of the paper P is not in the center of the heater, the heater blocks do not have to be arranged symmetrically.

As described above, the heater 152 divided into a plurality of heater blocks in the longitudinal direction has an advantage that the heat generation area width can be appropriately changed for various paper widths and paper positions when the number of divided heater blocks is large. However, there is a trade-off relationship when considering the increase in cost due to the increase in the number of temperature sensors and the complication of temperature control. Therefore, for example, the optimal number of divisions is set according to the paper size that can be accommodated in the paper feed cassette 18 and the paper width of several types of paper sizes mainly used by the user.

In addition, when the image forming apparatus 10 is idling, the temperature is lowered at the outermost end of the outermost heater block when the paper is not conveyed. If the temperature drop area at the end of the heater block is used, fixing failure will occur. Therefore, the block width of the split heater block is set to be wider than the paper width in anticipation of the temperature drop at the end of the heater block.

Power consumption can be reduced by dividing the heater 152 into a plurality of heater blocks and selecting and using only the heater blocks necessary for fixing according to the paper size.

As shown in FIG. 4, the central heater block 41 is the first heater block, the heater blocks 42a and 42b located on both sides of the heater block 41 are the second heater blocks, and the heater blocks 43a and 43b located on both sides are the second heater blocks. The third heater block and the heater blocks 44a and 44b located on both sides thereof are called fourth heater blocks.

In this embodiment, the inside of the heater block is further divided by heater cells, and a separation gap serving as a non-heat generating region is provided between the heater cells.

In the example of FIG. 4, the first heater block 41 is divided into ten heater cells, the second heater blocks 42a, 42b are divided into four heater cells 45, and the third heater blocks 43a, 43b are divided into three heater cells 45. , the fourth heater blocks 44a, 44b are divided into two heater cells 45; Also, all heater cells 45 are of the same size. Each heater cell consists of a resistance region 46 as a heating element and electrodes 47a and 47b for applying a voltage, and the resistance region 46 has a vertical width WT and a horizontal width WL. The heater cross-sectional structure will be described later with reference to FIG.

Each heater block 41-44 is spaced apart with a spacing gap BG. This separation gap BG is set from the insulation characteristics between the heater blocks, etc., in order to control the temperature of each heater block independently.

Also, each heater cell 45 is spaced apart to have a spacing gap CG. The separation gap CG of the heater cells is set to an optimum separation gap for reducing temperature unevenness in the longitudinal direction. A method of setting the optimum separation gap will be described later.

The heater blocks 41 to 44 are each formed with a power supply circuit for controlling the temperature of each heater block. In the example of FIG. 4, only the power supply circuit of the second heater block 42a is shown for explanation. Each heater cell 45 of the second heater block is connected in parallel to the control power supply 48 in the fixing control circuit 154 to generate heat. Other heater blocks have the same configuration.

As shown in FIG. 5, the heater 152 is formed by forming a resistance layer (resistance region 46) as a heating element on a ceramic substrate 49 on which a glaze layer is formed if necessary, and an electrode 47a and an electrode 47a are formed on the resistance layer. 47b is formed. Further, a glass-based protective layer 50 is formed. A current is passed from the fixing control circuit 154 in a direction perpendicular to the longitudinal direction of the heater 152, that is, between the electrodes 47a and 47b, thereby causing the resistance region 46, which is a heating element, to generate heat, thereby lifting the belt 53 in contact therewith. can be warmed. The cross section of each heater block 41-44 has a similar structure.

When the temperature sensor 56 is used under the substrate 49 , the temperature sensor 56 is appropriately added directly under the resistance area 46 whose temperature is to be detected in the belt rotation axis direction, that is, the substrate longitudinal direction of the heater 152. FIG. Specifically, a temperature sensor 56 may be provided directly under each heater cell 45 to detect the temperature variation of each heater cell, or at least one temperature sensor may be used for each heater block 41 to 44 to detect the fixing temperature. may be controlled. A thermistor or the like is used for these temperature sensors 56 .

FIG. 6 shows the structure of heater 152a when each heater block 41-44 is not divided into a plurality of heater cells. For the sake of explanation, the case where all the heater blocks 41 to 44 are selected is shown.

Each of the heater blocks 41 to 44 is composed of one heating element (resistive region 46), and the direction of current flow is perpendicular to the longitudinal direction as in FIG. Using -B' as a reference O, only the right part is illustrated. S1, S2, and S3 are from the reference O to the separation gap of each heater block, and S4 is the end surface of the heater.

FIG. 7 shows a heater temperature distribution diagram when each of the heater blocks 41 to 44 is not divided into a plurality of heater cells. Heater blocks 41 to 44 generally tend to have a high temperature in the center in the longitudinal direction, and temperature drops occur at spaced gap points S1 to S3 of the heater blocks and at heater ends S4. Furthermore, in a heater block having a heating element elongated in the longitudinal direction, a temperature distribution occurs due to variations in resistance values within the heater block. Therefore, the temperature difference in the entire heater is ΔTs. When the temperature difference ΔTs is a predetermined value or more, for example, 5° C. or more, fixing unevenness occurs in the longitudinal direction of the heater 152a, resulting in a difference in coloring and gloss.

In this embodiment, heater cells are introduced to divide the inside of the heater block in order to reduce this problem. FIG. 8 is an explanatory diagram (similar to FIG. 4) showing the heater structure when the heater block 152 is divided into heater cells, and FIG. 9 is a temperature distribution diagram in the longitudinal direction of the heater at that time. The vertical width WT of the heater cell can be set under such a condition that the heater 152 has a sufficient heat generation amount and a uniform heat generation area with respect to the fixing nip width N, and fixing unevenness does not occur in the paper conveying direction.

As shown in FIG. 9, the temperature distribution (temperature ripple) in the longitudinal direction of the heater 152 is such that the temperature rises at the center of each heater cell 45, and heat is dissipated at the separation gap CG between the heater cells and the temperature falls. will be repeated. In this manner, temperature ripples can be generated with the period of the number of heater cells arranged in the heater block, so that the temperature difference in each heater block can be suppressed within the range of ΔTc.

Also, at points S1 to S3, temperature ripples are generated due to the separation gap BG between the heater blocks. Therefore, by making the gap CG between the heater cells equal to or smaller than the gap BG between the heater blocks, the heater as a whole can be kept within the temperature difference ΔTb.

It is conceivable to increase the number of divisions in the heater block by fixing the vertical width WT of the heater cell and narrowing the horizontal width WL. If the number of divisions is increased, the period of temperature ripple determined by the number of heater cells is shortened, so there is an effect that the temperature difference is further reduced. However, if the heater cell separation gap CG is the same, the non-heat-generating area occupied by the entire heater increases, thereby deteriorating the heat-generating efficiency. Therefore, by setting the width WL equal to or slightly smaller than the vertical width WT that does not cause fixing unevenness in the conveying direction, it is possible to effectively reduce the influence of fixing unevenness occurring in the longitudinal direction. Further, it is preferable that the spaced gap CG between the heater cells is 1/10 or less of the lateral width WL.

Since the heater cells divided in each of the heater blocks 41 to 44 are subjected to the same temperature control, if there is a large variation in the resistance value of each heater cell 45, the temperature ripple will increase. In particular, when a thick film process using screen printing is used in the manufacturing process of the heater 152, variations in resistance values are likely to occur due to uneven film thickness. Therefore, the resistance value of each heater cell is measured, and if the variation is large, the resistance value of each heater cell is adjusted by a method such as laser trimming to keep the resistance value of each heater cell within a predetermined variation range. By adjusting the amount of heat generated by the heater cells to be the same, it is possible to control the fixing temperature with high precision without temperature unevenness in the longitudinal direction in units of heater cells.

Furthermore, if uneven fixing occurs in the paper transport direction due to uneven resistance film thickness in each heater cell, it is effective to use a heater cell having a square heat generation area with the same vertical width WT and horizontal width WL. target. At this time, the distribution of the sheet resistance (surface resistivity) in the heat generating region 46 of each heater cell is obtained, and the portion of the low sheet resistance region is adjusted by a method such as laser trimming to reduce the sheet resistance of the resistance region 46 in-plane. uniform. By arranging the heater cells in which the sheet resistance in the plane of the heater cell is made uniform in this way, it is possible to further reduce uneven fixing in the conveying direction and the longitudinal direction of the heater.

FIG. 10 is an explanatory diagram showing the relationship between the heat cell separation gap CG and the temperature ripple ΔTc caused by the heat cell separation gap CG. Since the temperature ripple ΔTc varies depending on the material and configuration of the belt 53 with which the heater 152 abuts, the base material of the belt 53 is nickel (Ni) or polyimide (Pi), and the thickness of the belt rubber (silicone rubber) The measurement results are shown when the thickness is changed. From this result, it can be seen that there is a roughly proportional relationship between the heat cell separation gap CG and the temperature ripple ΔTc. A dashed-dotted line 60 indicates a straight line (inclination) where the value obtained by dividing the temperature ripple by the separation gap CG of the heat cell is 5 (° C./mm).

When Ni is used as the base material, the lower area defined by the dashed line 60 is satisfied when the Ni thickness is 30 μm to 40 μm and the belt rubber thickness is 200 μm.

In the case of using Pi as the base material, if the thickness of Pi is 70 μm, the lower region defined by the dashed line 60 is satisfied when the thickness of the belt rubber is 0 μm to 200 μm.

Therefore, if the film thickness configuration of the base material and the belt rubber shown in FIG. can be reduced to the following. For example, in order to set ΔTc to 5° C. or less, the separation gap CG of the heater cell 45 is 1.0 mm or less. Also, in order to keep the temperature ripple ΔTc at 3° C. or less, the separation gap CG between the heater cells is 0.6 mm or less.

Furthermore, when the base material of the belt 53 and the thickness of the belt rubber used in the heater 152 of the present embodiment are determined, the temperature ripple ΔTc and the distance between the heat cells with respect to the thickness of the belt base material and the belt rubber used A straight line indicating the relationship with the gap CG may be newly obtained, and the heater cell separation gap CG may be determined so as to be within the range of the predetermined temperature ripple ΔTc from this straight line.

FIG. 11 is a flow chart showing an example of a heater design method and an adjustment method. First, in Act 1, the material and configuration of the belt 53 mounted on the image forming apparatus are determined from the fixing characteristics, durability characteristics, and the like. In Act 2, the longitudinal width WT of the heater in the transport direction is determined from the amount of heat generated by the heater 152 that satisfies the fixing characteristics, the fixing nip width N, and the like.

In Act 3, the width WL of the heater cell is set substantially equal to or smaller than the vertical width WT of the heater cell, and the heater cell separation gap CG that satisfies a predetermined (desired) temperature ripple ΔTc is determined according to FIG. .

In Act4, the resistance value of each heater cell 45 is measured. If the resistance value is not within the predetermined value range (Act 4: No), laser trimming or the like is applied to the heater cell with the low resistance value to adjust the resistance value. If all the resistance values of the heater cells are within the predetermined value range (Act4: Yes), the process ends without adjustment. As a result, the heat generation characteristics of the heater cells arranged in the heater block can be made uniform, so that the heat can be uniformed in the longitudinal direction of the heater.

As described above, according to the embodiment, the heater 152 is divided into a plurality of heater blocks, and each heater block is further divided into a plurality of heater cells. The heater cells are arranged with a non-heating element spacing gap. This makes it possible to generate a temperature ripple in heater cell units and reduce the temperature difference in the longitudinal direction of the heater 152 .

Further, by adjusting the resistance value of the heater cells to equalize the amount of heat generated by all the heater cells, highly accurate fixing temperature control without temperature unevenness in the longitudinal direction can be performed for each heater cell as a unit.

Furthermore, if the vertical width WT and the horizontal width WL of the heating element of the heater cell are made approximately the same, the heater cell becomes approximately square. The in-plane resistance distribution of each heater cell can be made uniform. That is, the heat generation distribution in each heater cell can be made uniform not only in the longitudinal direction of the heater, but also in the sheet conveying direction.

Further, if the separation gap CG is set so that the amount of temperature ripple with respect to the separation gap CG of the heater cell is 5 (° C./mm) or less, most commonly used fixing belts can achieve the desired temperature ripple. can be satisfied. This is effective in heater design and replacement maintenance for various fixing belts.

Further, by arranging the temperature sensor 56 directly below each heater cell 45, it is possible to accurately grasp the belt surface temperature of the heating element group formed by the heater block selected according to the paper width.

It should be noted that while several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, replacements, and modifications 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 scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Image forming apparatus 36... Fixing device 41-44... Heater block 45... Heater cell 53... Belt 54... Pressure member 152... Heaters 153, 56, 57, 58... Temperature sensor

Claims (4)

a rotating endless belt;
divided into a plurality of heater blocks insulated from each other with a first spacing gap along the axis of rotation of the belt, and each of the heater blocks being divided into a plurality of heater cells having a second spacing gap. a heater having a heat generating region and arranged in contact with the inner side of the belt;
a pressurizing body arranged to press the paper to be conveyed at a position facing the heater with the belt interposed therebetween;
with
one surface of the heater is formed on one surface of the substrate and an electrode is formed on the other surface of the heater;
A temperature sensor is provided at each position corresponding to each of the heater cells on the other surface of the substrate on which the heater is not formed,
The fixing device, wherein the width of the second spacing gap is narrower than the width of the first spacing gap. wherein the second spacing gap is 1/10 or less of the lateral width of the heater cell;
The fixing device according to claim 1. The heater cell has the same vertical width and horizontal width,
The fixing device according to claim 1 or 2. The fixing device according to any one of claims 1 to 3, further comprising a power supply circuit for controlling the temperature of each heater block.

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