JP6960822B2 - Fixing device and image forming device - Google Patents

Description

Embodiments of the present invention relate to a fixing device and an image forming device.

In the fixing device, the paper is heated by a heater to fix the toner. A heater in which a plurality of heating elements are arranged on a ceramic substrate is known, and a plurality of heating elements are grouped in the longitudinal direction of the substrate to form a heating element group, and each heating element group is heated and driven (for example, a patent). Reference 1).

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

Japanese Unexamined Patent Publication No. 2015-219417 Japanese Unexamined Patent Publication No. 2008-15235

An object to be solved by the present invention is to solve the above problems, to reduce temperature unevenness in the longitudinal direction of the heater substrate, and to provide a fixing device and an image forming device capable of highly accurate temperature control.

In order to achieve the above object, the fixing device and the image forming device of the present embodiment are divided into a rotating endless belt and a plurality of heater blocks having a first separation gap in the rotation axis direction of the belt. Each of the heater blocks has a heat generating region divided into a plurality of heater cells having a second separation gap, and a heater arranged in contact with the inside of the belt and the heater sandwiching the belt. At opposite positions, a pressurizing body arranged to pressurize the paper to be conveyed and a fixing control unit for controlling each heater cell in the heater block to the same temperature for each of the heater blocks are provided. The width of the second separation gap is narrower than the width of the first separation gap.

The block diagram of the image forming apparatus including the fixing apparatus which concerns on embodiment. The block diagram which shows the control system of the image forming apparatus which concerns on embodiment. The block diagram which shows an example of the fixing device which concerns on embodiment. The plan view which shows an example of the heater which concerns on embodiment. The cross-sectional view which shows an example of the heater which concerns on embodiment. Explanatory drawing which shows the heater structure when a heater block is not divided into a heater cell. Temperature distribution map of the heater when the heater block is not divided into heater cells. Explanatory drawing which shows the heater structure when a heater block is divided into a heater cell. Temperature distribution map of the heater when the heater block is divided into heater cells. Explanatory drawing which shows the relationship between the separation gap of a heater cell and temperature ripple. The flowchart which shows an example of the design method and the adjustment method of a heater.

Hereinafter, embodiments will be described in detail with reference to FIGS. 1 to 11. In the following description, components having substantially the same function and configuration are designated by the same reference numerals, and duplicate explanations will be given only when necessary.

In FIG. 1, the image forming apparatus 10 is, for example, an MFP (Multi-Function Peripherals), a printer, a copying machine, or the like, which is a multifunction device. In the following description, the MFP will be described as an example.

A transparent glass document base 12 is provided above the main body 11 of the image forming apparatus 10, and an ADF (Auto Document Feeder) 13 is provided on the document table 12 so as to be openable and closable. An input / output control unit 14 is provided on the upper part 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 which is 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 a document placed on a platen to generate image data, and includes, for example, a close contact type image sensor 16 (hereinafter, simply referred to as an image sensor). The image sensor 16 is arranged in the main scanning direction.

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

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

The printer unit 17 has scanning heads 19Y, 19M, 19C, 19K including an LED or a laser as an exposure device for each color of yellow (Y), magenta (M), cyan (C), and black (K), and exposes the printer unit 17. An image is generated on the photoconductor by scanning the light beam from each scanning head 19 of the device. The printer unit 17 is, for example, a color laser printer based on a pattern dem method, and is composed of image forming units 20Y, 20M, 20C, and 20K for each color. The image forming portions 20Y to 20K are arranged in parallel on the lower side of the intermediate transfer belt 21 from the upstream side to the downstream side.

The intermediate transfer belt 21 is stretched on the drive roller 31 and the driven roller 32 and moves cyclically. Further, the intermediate transfer belt 21 is in contact with the photoconductor drums 22Y, 22M, 22C, and 22K so as to face each other.

Since the image forming units 20Y to 20K of each color have the same configuration, if the image forming unit 20K is described as an example, a charger 23K, a developing device 24K, a primary transfer roller 25K, etc. are arranged around the photoconductor drum 22K. ing. The exposure position of the photoconductor drum 22K is irradiated with light from the scanning head 19K to form an electrostatic latent image on the photoconductor drum 22K.

The charger 23K uniformly charges the surface of the photoconductor drum 22K. The developer 24K supplies black toner to the photoconductor drum 22K by a developing roller to which a developing bias is applied to develop an electrostatic latent image.

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

The drive roller 31 that stretches the intermediate transfer belt 21 is arranged so that the secondary transfer roller 33 faces the secondary transfer roller 33. When the paper P passes between the drive roller 31 and the secondary transfer roller 33, the 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 in the vicinity of the driven roller 32 of the intermediate transfer belt 21.

Further, a paper feed roller 35 for transporting the paper P taken out from the paper feed cassette 18 is provided in the transport path from the paper feed cassette 18 to the secondary transfer roller 33. Further, a fixing device 36, which is 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 ejection portion 38 by the transport roller 37. Further, the image forming apparatus 10 is integratedly controlled by the system control unit 39.

Further, the size and position of the conveyed paper can be determined in real time by using the line sensor 40 arranged in the paper passing area.

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

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

The system control unit 39 is composed of, 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 realizes control of the entire device including image formation control and fixing temperature control by executing a program stored in the ROM 120 or the RAM 121. The ROM 120 stores control programs such as image formation control and fixing temperature control, and control data. The RAM 121 is mainly used as a working memory for executing control of the entire device.

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. The I / F 122 communicates with various devices such as a user terminal and a facsimile.

The input / output control unit 14 controls the operation panel 14a connected to the input / output control circuit 123, the display unit 14b, 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 original, and the like. The display unit 14b displays the operating state and the like of the image forming apparatus 10.

The paper feed / transport control unit 130 is composed of a paper feed / transport control circuit 131, a motor group 132, and a sensor group 133, and executes control of paper feed and paper transport. The paper feed / transport control circuit 131 controls a motor group 132 or the like that drives the paper feed roller 35 or the transport roller 37 on the transport path. Further, the paper feed / transport control circuit 131 controls the motor group 132 and the like in the vicinity of the paper feed cassette 18 or according to the detection results of various sensor groups 133 on the transport path based on the control signal from the CPU 100.

The image formation control unit 140 controls image formation control to control the photoconductor drum 22, the charger 23, the exposure device (scanning head) 19, the developer 24, and the transfer device (transfer roller) 25, respectively, based on the control signal 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, a fixing temperature control, and a fixing control circuit 154 for performing safety control such as prevention of excessive temperature rise. It is composed of and executes the fixing control.

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

In the endless belt 53, for example, a silicone rubber layer having a thickness of about 200 μm is formed on the outside of a Ni (nickel) base material having a thickness of 40 μm or a polyimide heat-resistant resin base material having a thickness of 70 μm, and the outer periphery thereof is PFA (Perfluoroalkoxy). It is coated with a protective layer such as. In the pressure roller 54, for example, a silicone sponge layer having a thickness of about 5 mm is formed on the surface of an iron rod having a diameter of 10 mm, and the outer periphery is coated with a protective layer such as PFA.

Further, in the fixing device 36, a heater 152 for raising the temperature that abuts on the back surface 52 of the belt in the rotation axis direction (belt width direction) of the belt 53 is arranged. The endless belt 53 rotates while forming a fixing nip width N with the pressure roller 54 in the direction of arrow S. When the paper P passes through the fixing nip portion in the direction of the 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 various temperature sensors 153 that detect the fixing temperature. FIG. 3 shows a temperature sensor 56 arranged on the back surface of the heater 152, a temperature sensor 57 arranged on the back surface 52 of the belt to detect the temperature of the back surface of the belt, and a temperature sensor 58 arranged on the front surface 51 of the belt to measure the temperature of the surface of the belt. ing. Since the temperature sensors 57 and 58 need to be arranged on the circumference of the belt 53 away from the fixing nip portion, it is necessary to correct the temperature accompanying the rotation of the belt 53. Further, the temperature sensor 58 is preferably non-contact so as not to damage the belt 53. The fixing device 36 is controlled by the fixing control circuit 154.

In the fixing temperature control, these temperature sensors 56, 57, 58 can be appropriately selected, or a plurality of types can be used in combination. Further, as will be described later, since a heater block whose temperature is controlled is selected according to the width of the paper to be conveyed and the transfer position, a plurality of temperature sensors for detecting the temperature of the selected heater block are required. Become.

FIG. 4 is a plan view showing an example of the heater, and FIG. 5 is a cross-sectional view thereof. The heater 152 is divided into a plurality of heater blocks symmetrically with respect to the heater center line (BB') indicated by the alternate long and short dash line. In this embodiment, an example of 7 divisions is shown. Of course, this 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 margins. Further, when the transport position of the paper P is not set in the center of the heater, the heater blocks do not have to be arranged symmetrically.

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

Further, when the paper is not conveyed, such as when the image forming apparatus 10 is idling, the temperature drops at the outermost end of the heater block located on the outermost side. If the temperature drop region at the end of the heater block is used, fixing failure will occur. Therefore, the block width of the divided heater block is set to be wider than the paper width in anticipation of the temperature drop at the end of the heater block.

By dividing the heater 152 into a plurality of heater blocks in this way and selecting and using only the heater blocks necessary for fixing according to the paper size, the power consumption can be reduced.

As shown in FIG. 4, the heater block 41 in the center 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 thereof are. The third heater block and the heater blocks 44a and 44b located on both sides thereof will be referred to as a fourth heater block.

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

In the example of FIG. 4, the first heater block 41 is divided into 10 heater cells, the second heater blocks 42a and 42b are divided into four heater cells 45, and the third heater blocks 43a and 43b are divided into three heater cells 45. The fourth heater blocks 44a and 44b are divided into two heater cells 45. Further, all the heater cells 45 have the same size. Each heater cell includes a resistance region 46 as a heating element and electrodes 47a and 47b to which a voltage is applied, and the resistance region 46 has a vertical width WT and a horizontal width WL. The cross-sectional structure of the heater will be described later in FIG.

The heater blocks 41 to 44 are spaced apart so as to have a separation gap BG. This separation gap BG is set from the insulation characteristics between the heater blocks in order to control the temperature of each heater block independently.

Further, the heater cells 45 are arranged apart so as to have a separation gap CG. The separation gap CG of the heater cell is set to an optimum separation gap for reducing temperature unevenness in the longitudinal direction. The method of setting the optimum separation gap will be described later.

Each of the heater blocks 41 to 44 is formed with a power feeding circuit for controlling the temperature of each heater block. In the example of FIG. 4, for the sake of explanation, only the power feeding circuit of the second heater block 42a is shown. 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, in the heater 152, a resistance layer (resistance region 46) as a heating element is formed on a ceramic substrate 49 on which a glaze layer is formed, if necessary, and an electrode 47a and an electrode are formed on the resistance layer. 47b is formed. Further, a glass-based protective layer 50 is formed. By passing a current from the fixing control circuit 154 in the direction orthogonal to the longitudinal direction of the heater 152, that is, between the electrodes 47a and 47b, the resistance region 46, which is a heating element, is generated to generate heat, and the abutting belt 53 is raised. Can be warmed. The cross sections of the heater blocks 41 to 44 have a similar structure.

When the temperature sensor 56 is used under the substrate 61, the temperature sensor 56 is appropriately added directly below the heat generating region 46 in which the temperature should be detected in the belt rotation axis direction, that is, in the longitudinal direction of the substrate of the heater 152. Specifically, a temperature sensor 56 may be provided directly under each heater cell 45 to detect temperature variation in each heater cell, or at least one temperature sensor may be used for each heater block 41 to 44 to settle the temperature. Control may be performed. A thermistor or the like is used for these temperature sensors 56.

FIG. 6 shows the structure of the heater 152a when each of the heater blocks 41 to 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 (resistance region 46), and the direction of the current is the direction orthogonal to the longitudinal direction as in FIG. 4, the center line B of the heater. Only the right part is shown with −B'as the reference O. S1, S2, S3, and the end face of the heater are S4 from the reference O to the separation gap of each heater block, respectively.

FIG. 7 shows a temperature distribution map of the heater when each heater block 41 to 44 is not divided into a plurality of heater cells. The temperature of the heater blocks 41 to 44 generally tends to increase in the center in the longitudinal direction, and the temperature drops at the separation gap points S1 to S3 of the heater block and the heater end S4. Further, in a heater block having a heating element long in the longitudinal direction, a temperature distribution is generated due to a variation in resistance value in the heater block. Therefore, the temperature difference in the entire heater is ΔTs. When the temperature difference ΔTs is equal to or higher than a predetermined value, for example, 5 ° C. or higher, uneven fixing occurs in the longitudinal direction of the heater 152a, resulting in a difference in color development and gloss.

In the present embodiment, in order to reduce this problem, a heater cell that divides the inside of the heater block is introduced. FIG. 8 is an explanatory view (similar to FIG. 4) showing a 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 the condition that the heater 152 has a sufficient heat generation amount and a uniform heat generation region with respect to the fixing nip width N, and the fixing unevenness does not occur in the paper transport direction.

As shown in FIG. 9, the temperature distribution in the longitudinal direction of the heater 152 is such that the temperature rises at the center of each heater cell 45 and is dissipated at the position of the separation gap CG of each heater cell and the temperature drops. Will be repeated. As described above, since the temperature ripple can be generated in the cycle of the number of heater cells arranged in the heater block, the temperature difference in each heater block can be suppressed within the range of ΔTc.

Further, at points S1 to S3, temperature ripple occurs due to the separation gap BG of the heater block. Therefore, by making the separation gap CG of the heater cell equal to or smaller than the separation gap BG of the heater block, the temperature difference ΔTb of the entire heater can be suppressed.

It is also conceivable to keep the vertical width WT of the heater cell constant, narrow the horizontal width WL, and increase the number of divisions in the heater block. When the number of divisions is increased, the period of the temperature ripple determined by the number of heater cells is shortened, which has the effect of further reducing the temperature difference. However, if the separation gap CG of the heater cells is the same, the heat generation efficiency deteriorates due to the increase in the non-heat generation region occupying the entire heater. Therefore, if a width WL that is equal to or slightly smaller than the vertical width WT that does not cause fixing unevenness in the transport direction is set, the influence of fixing unevenness that occurs in the longitudinal direction can be effectively reduced. Further, the separation gap CG of the heater cell is preferably 1/10 or less of the width WL.

Since the same temperature control is performed for the heater cells divided in the heater blocks 41 to 44, if there is a large variation in the resistance value of each heater cell 45, the temperature ripple becomes large. In particular, when a thick film process using screen printing is used in the manufacturing process of the heater 152, the resistance value tends to vary due to uneven film thickness. Therefore, the resistance value of each heater cell is measured, and if the variation is large, the one having a low resistance value is adjusted by a method such as laser trimming, and the resistance value of each heater cell is kept within a predetermined variation range. By adjusting the calorific value of the heater cells equally, it is possible to control the fixing temperature with high accuracy without temperature unevenness in the longitudinal direction in units of the heater cells.

Furthermore, when fixing unevenness 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 region in which the vertical width WT and the horizontal width WL of the heater cell are equal. Is the target. At this time, the distribution of the sheet resistance (surface resistivity) in the heat generating region 46 of each heater cell is obtained, the portion of the region where the sheet resistance is low is adjusted by a method such as laser trimming, and the sheet resistance of the resistance region 46 is adjusted in the plane. Make it uniform. By arranging the heater cells in which the sheet resistance in the heater cell surface is made uniform in this way, it is possible to further reduce the fixing unevenness in the transport direction and the longitudinal direction of the heater.

FIG. 10 is an explanatory diagram showing the relationship between the separation gap CG of the heat cell and the temperature ripple ΔTc caused by the separation gap CG of the heat cell. Since the temperature ripple ΔTc differs depending on the material and configuration of the belt 53 with which the heater 152 abuts, two types of nickel (Ni) and polyimide (Pi) are used as the base material of the belt 53, and the thickness of the belt rubber (silicone rubber) is used. The measurement result when the temperature is changed is shown. From this result, it can be seen that the separation gap CG of the heat cell and the temperature ripple ΔTc have a substantially proportional relationship. Further, the alternate long and short dash line 60 shows a straight line (slope) in which 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, when the Ni thickness is 30 μm to 40 μm and the belt rubber thickness is 200 μm, the lower region separated by the alternate long and short dash line 60 is satisfied.

Further, when Pi is used as a base material, if the Pi thickness is 70 μm, the lower region separated by the alternate long and short dash line 60 is satisfied at a belt rubber thickness of 0 μm to 200 μm.

Therefore, if the film thickness configuration of the base material and the belt rubber shown in FIG. 10 is adopted, the lower region separated by the alternate long and short dash line 60 is satisfied in any of the belt configurations, and the temperature ripple caused by the heater cell 45 is set to a predetermined value. It can be suppressed to the following. For example, in order to set ΔTc to 5 ° C. or lower, the separation gap CG of the heater cell 45 is 1.0 mm or less. Further, in order to reduce the temperature ripple ΔTc to 3 ° C. or lower, the separation gap CG of the heater cell is 0.6 mm or less.

Further, when the thickness of the base material and the belt rubber of the belt 53 used for the heater 152 of the present embodiment is determined, the temperature ripple ΔTc and the heat cell are separated from each other 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 separation gap CG of the heater cell may be determined so as to be within a predetermined temperature ripple ΔTc from this straight line.

FIG. 11 is a flowchart 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 Act2, the vertical width WT of the heater in the transport direction is determined from the calorific value of the heater 152 satisfying the fixing characteristics, the fixing nip width N, and the like.

In Act3, the width WL of the heater cell having substantially the same dimensions as the vertical width WT of the heater cell or smaller is set, and the separation gap CG of the heater cell that satisfies a predetermined (desired) temperature ripple ΔTc is determined according to FIG. ..

Further, in Act 4, the resistance value of each heater cell 45 is measured. If the resistance value is not within a predetermined value range (Act4: No), the resistance value is adjusted by performing laser trimming or the like on the heater cell having a low resistance value. If the resistance values of the heater cells are all 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 equalized 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 the inside of each heater block is further divided by a plurality of heater cells. The heater cell is arranged so as to provide a separation gap for the non-heating body. As a result, it is possible to generate a temperature ripple in each heater cell and reduce the temperature difference in the longitudinal direction of the heater 152.

Further, by adjusting the resistance value of the heater cells and equalizing the calorific value of all the heater cells, it is possible to control the fixing temperature with high accuracy without temperature unevenness in the longitudinal direction in units of the heater cells.

Further, if the vertical width WT and the horizontal width WL of the heating element of the heater cell are made substantially the same, the heater cell becomes substantially square. Therefore, by measuring and adjusting the sheet resistance in the heater cell, the resistance film thickness is uneven. 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 constant not only in the longitudinal direction of the heater but also in the paper transport 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, the desired temperature ripple can be obtained with most of the commonly used fixing belts. You can be satisfied. This is effective in heater design and replacement maintenance for various fixing belts.

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

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The present 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 the equivalent scope thereof.

10 ... Image forming device 36 ... Fixing device 41-44 ... Heater block 45 ... Heater cell 53 ... Belt 54 ... Pressurizing body 152 ... Heater 153, 56, 57, 58 ... Temperature sensor

Claims (6)

With a rotating endless belt,
In the rotation axis direction of the belt, each of the heater blocks is divided into a plurality of heater blocks having a first separation gap, and each of the heater blocks has a heat generating region divided into a plurality of heater cells having a second separation gap. , The heater placed in contact with the inside of the belt,
A pressurizing body arranged to pressurize the paper to be conveyed at a position facing the heater across the belt.
For each of the heater blocks, a fixing control unit that controls each of the heater cells in the heater block to the same temperature,
Equipped with a,
The second width of the spacing gap, said first spacing gap narrower der Ru fixing device than a width of. The fixing device according to claim 1, wherein the width of the second separation gap is a width of 1/10 or less of the lateral width of the heater cell. The first or second aspect of the present invention, wherein the current direction of the heating element of the heater cell is the transport direction of the paper, and the resistance value of the heater cell in each heater block is adjusted equally so as to be within a predetermined range. Fixing device. The Hitaseru the fixing device according to claim 1, wherein in any one of 3 that all are positive square in together If it is the same size. The fixing device according to any one of claims 1 to 3, wherein the second separation gap is set so that the amount of temperature ripple with respect to the second separation gap is 5 (° C./mm) or less. An image forming apparatus having a fixing device according to any one of the請Motomeko 1 5.

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