JP2021119399A - Heating member, fixing device, and image forming apparatus - Google Patents

Abstract

To allow intensive and stable heating of a paper feed area to achieve improvement in fixing quality and energy saving.SOLUTION: A fixing device comprises: determination means that determines the size of a medium on which a toner image is formed; heating means that has a rotating body in an endless shape, a plurality of heating members arranged in contact with the inside of the rotating body, and a switching unit individually switching energization to electrodes of the heating members, and heats the medium; pressure means that is in pressure contact with the heating means at the positions of the plurality of heating members to form a nip and sandwiches and conveys the medium with the heating means in a conveyance direction; and heating control means that selects the heating member corresponding to the position through which the medium passes and energizes the selected heating member to control the heating.SELECTED DRAWING: Figure 6

Description

The present embodiment relates to a fixing device and an image forming device.

As a heat source for a fixing device mounted on an image forming apparatus, a lamp that emits infrared rays such as a halogen lamp or a method of heating with Joule heat by electromagnetic induction has been put into practical use.

Generally, a fixing device is composed of a pair of a heating roller (or a fixing belt spanned by a plurality of rollers) and a press roller, but in order to maximize the thermal efficiency of the fixing device, the heat capacity of the component is reduced as much as possible. It is required to concentrate the heating area.

Japanese Patent No. 2629980

In the above-mentioned heating method, since the heating width is wide, it is difficult to intensively apply the heat energy dispersed over a wide range only to the nip portion, and it is difficult to optimize the thermal efficiency. Further, in the fixing device for electrophotographic, if heat generation unevenness occurs in the direction perpendicular to the paper transport direction, the fixing quality is affected. In particular, in the case of color printing, there is a possibility that differences in color development and gloss may occur.

Furthermore, in a fixing device with an extremely reduced heat capacity, the temperature of the part through which the paper does not pass rises extremely, which may cause problems such as warpage of the heater, deterioration of the belt, and speed unevenness due to expansion of the transport roller. rice field. Further, it is not preferable to heat the portion through which the paper does not pass from the viewpoint of energy saving. Intensive heating of only the part through which the paper passes is an important technical issue from the viewpoint of environmental friendliness.

For this reason, it has been proposed to divide the heat generation area for control, but when dividing the heat generation area, heat generation after division is taken into consideration in consideration of the operating voltage value, installation environment, etc. from safety measures. Since the creepage distance or the space distance at the boundary portion between the members must be provided at a certain value or more, the temperature drops at that portion, and as a result, the fixing quality deteriorates due to the temperature unevenness.

Therefore, in view of the above-mentioned problems of the prior art, it is an object of the present invention to enable intensive and stable heating of the paper-passing area, and to improve fixing quality and save energy.

In the fixing device according to one embodiment, the determination means for determining the size of the medium on which the toner image is formed, the endless-shaped rotating body, and the length of the medium in the transport direction are the same, and the transport direction is the same. It is divided into a plurality of lengths in a direction perpendicular to the above, and the creepage distance between the electrodes formed at both ends, the creepage distance or the spatial distance at the boundary portion after the division is adjusted to a predetermined value, and the above-mentioned A heating means for heating the medium and a heating means for heating the medium, which have a plurality of heat-generating members arranged in contact with the inside of the rotating body and a switching unit for individually switching the energization of the electrodes of the heat-generating members, and the heating means. Corresponds to the pressurizing means that press-contacts the positions of the plurality of heat-generating members to form a nip and sandwiches and conveys the medium together with the heating means in the transport direction, and the position of the plurality of heat-generating members through which the medium passes. It is characterized by comprising a heating control means for controlling heating in the heating means by selecting and energizing the heat generating member to be generated by the switching unit.

The figure which shows the structural example of the image forming apparatus which mounts the fixing apparatus which concerns on one Embodiment. FIG. 6 is an enlarged configuration diagram showing a part of an image forming portion in one embodiment. The block diagram which shows the structural example of the control system of the MFP in one Embodiment. The figure which shows the structural example of the fixing device which concerns on one Embodiment. The layout of the heat generating member group in one embodiment. The cross-sectional view explaining the creepage distance between the heat generating members after division in one Embodiment. The figure which shows the connection state of the heat generating member group and its drive circuit in one Embodiment. The flowchart which shows the specific example of the control operation of the MFP in one Embodiment. FIG. 5 is a cross-sectional view showing a fixed structure of a heat generating member and a ceramic substrate in a modified example of one embodiment. The figure which shows the shape pattern of the heat generating member group in the modification of one Embodiment. The figure which shows the shape pattern of the heat generating member group in the modification of one Embodiment.

Hereinafter, the fixing device according to the embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration example of an image forming apparatus on which the fixing apparatus according to the present embodiment is mounted. In FIG. 1, the image forming apparatus 10 is, for example, an MFP (Multi-Function Peripherals) which is a multifunction device, a printer, a copying machine, or the like. In the following description, the 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 transport unit (ADF) 13 is provided on the platen 12 so as to be openable and closable. Further, an operation unit 14 is provided on the upper part of the main body 11. The operation unit 14 has various keys and a touch panel type display unit.

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 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 (depth direction in FIG. 1).

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 to read one page of the document. 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).

Further, a printer unit 17 is provided in the central portion of the main body 11, and a plurality of paper feed cassettes 18 for accommodating various sizes of paper P are provided in the lower 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 paper. The printer unit 17 is, for example, a tandem color laser printer, and includes image forming units 20Y, 20M, 20C, and 20K of each color of yellow (Y), magenta (M), cyan (C), and black (K). The image forming portions 20Y, 20M, 20C, and 20K are arranged in parallel on the lower side of the intermediate transfer belt 21 from the upstream side to the downstream side. Further, the laser exposure device (scanning head) 19 also has a plurality of laser exposure devices 19Y, 19M, 19C, 19K corresponding to the image forming units 20Y, 20M, 20C, 20K.

FIG. 2 is a configuration diagram showing an enlarged 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 has a photoconductor drum 22K which is an image carrier. A charger (charging charger) 23K, a developing device 24K, a primary transfer roller (transferring device) 25K, a cleaner 26K, a blade 27K, and the like are arranged around the photoconductor drum 22K along the rotation direction t. The exposure position of the photoconductor drum 22K is irradiated with light from the laser exposure device 19K to form an electrostatic latent image on the photoconductor drum 22K.

The charger 23K of the image forming unit 20K uniformly charges the surface of the photoconductor drum 22K. The developer 24K supplies a two-component developer containing black toner and carriers to the photoconductor drum 22K by a developing roller 24a to which a development bias is applied to develop an electrostatic latent image. The cleaner 26K uses a blade 27K to remove residual toner on the surface of the photoconductor drum 22K.

Further, as shown in FIG. 1, a toner cartridge 28 for supplying toner to the developing units 24Y to 24K is provided above the image forming portions 20Y to 20K. The toner cartridge 28 includes toner cartridges of each color of yellow (Y), magenta (M), cyan (C), and black (K).

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

A secondary transfer roller 33 is arranged to face the drive roller 31 on which the intermediate transfer belt 21 is stretched. When the paper P passes between the drive roller 31 and the secondary transfer roller 33, the secondary transfer voltage is applied 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, as shown in FIG. 1, a paper feed roller 35 for transporting 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. A transport roller 37 is provided downstream of the fixing device 36. The transport roller 37 discharges the paper P to the paper ejection unit 38. Further, a reversing transport path 39 is provided downstream of the fixing device 36. The reverse transfer path 39 reverses the paper P and guides it in the direction of the secondary transfer roller 33, and is used when performing double-sided printing. 1 and 2 show a configuration example of the MFP 10, and do not limit the structure of the image forming apparatus portion other than the fixing device 36, and a known electrophotographic image forming apparatus structure can be used.

FIG. 3 is a block diagram showing a configuration example of the control system 50 of the MFP 10 in the present 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, and a paper feed / transport control circuit. It includes 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, control data, and the like that control the basic operation 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 a correspondence relationship between the size (width in the main scanning direction) of the paper passing area and the printing area in the paper and the heat generating member to be energized.

The fixing temperature control program of the fixing device 36 has a determination logic for determining the size of the image forming area on the paper on which the toner image is formed, and the paper passing area of the paper before the paper is conveyed to the inside of the fixing device 36. It includes a heating control logic that selects and energizes the switching element of the corresponding heat generating member and controls the heating in the heating means.

The I / F 122 communicates with various devices such as a user terminal and a facsimile. The input / output control circuit 123 controls the operation panel 123a and the display 123b that constitute the operation unit 14. The paper feed / transport control circuit 130 controls the motor group 130a or the like that drives the paper feed roller 35 or the transport roller 37 of the transport path. The paper feed / transport control circuit 130 controls the motor group 130a and the like based on the control signal from the CPU 100 in consideration of the detection results of various sensors 130b in the vicinity of the paper feed cassette 18 or on the transport path. The image formation control circuit 140 controls the photoconductor drum 22, the charger 23, the laser exposure device 19, the developer 24, and the transfer device 25, respectively, based on the control signal from the CPU 100. The fixing control circuit 150 controls the drive motor 360 of the fixing device 36, the heating member 361, and the temperature detecting member 362 such as the thermistor, respectively, 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, a calculation processing device and a storage device are separately provided for the fixing device 36. You may.

FIG. 4 is a diagram showing a configuration example of the fixing device 36. Here, the fixing device 36 applies tension to the plate-shaped heating member 361, the elastic layer, the endless belt 363 suspended on a plurality of rollers, the belt transport roller 364 for driving the endless belt 363, and the endless belt 363. It includes a tension roller 365 and a press roller 366 having an elastic layer formed on the surface. In the heating member 361, the heat generating portion side comes into contact with the inside of the endless belt 363 and is pressed in the direction of the press roller 366 to form a fixing nip having a predetermined width between the heating member 361 and 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 that in the case of the heating method using a halogen lamp.

In the endless belt 363, for example, a silicon rubber layer having a thickness of 200 um is formed on the outside of a SUS base material having a thickness of 50 um or a polyimide which is a heat resistant resin of 70 um, 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 thereof is covered with a surface protective layer such as PFA.

Further, in the heating member 361, a glaze layer and a heat generation resistance layer are laminated on a ceramic substrate. The heat generation resistance layer is formed of a known material such as TaSiO2 and is divided into a predetermined length and number in the main scanning direction in order to release excess heat to the opposite side and prevent the substrate from warping.

The method for forming the heat generation resistance layer is the same as that of a known method (for example, a method for producing a thermal head), and a masking layer is formed of aluminum on the heat generation resistance layer. The aluminum layer is formed in a pattern in which adjacent heat generating members are insulated from each other and the heat generating resistor (heat generating member) is exposed in the paper transport direction. To energize the heat generation resistance layer, connect the wiring from the aluminum layers (electrodes) at both ends, and connect each to the switching element of the switching driver IC. Further, a protective layer is formed at the uppermost portion so as to cover all of the heat generation resistance layer, the aluminum layer, the wiring and the like. The protective layer is formed of, for example, Si3N4.

FIG. 5 is a layout diagram of the heat generating member group in the present embodiment. As shown in the figure, on the ceramic substrate 361a, heat generating members 361b having a plurality of lengths in the left and right directions shown and formed in a parallelogram or trapezoidal shape are arranged side by side. Electrodes 361c and electrodes 361d are formed at both ends of the 361b in the paper transport direction (vertical direction in the drawing).

As shown in FIG. 5, the heat generating member 361b is divided into a plurality of parts, but as will be described later, these are driven by a DC or AC applied voltage in a heat generating member unit or a heat generating member group unit (block unit). However, for example, in the case of high voltage (100 V or more) by alternating current or when the amount of current is large even by direct current, it is necessary to secure a sufficient creepage distance and space distance between adjacent heat generating members 361b for safety measures. The creepage distance is the shortest distance between the two conductive parts along the surface of the insulator. On the other hand, the spatial distance is the shortest distance between the two conductive portions through the space. However, if these distances are made too long, the temperature will drop at the boundary.

Therefore, in the present embodiment, the shape of each heat generating member 361b is changed in order to adjust the creepage distance or the spatial distance at the boundary between adjacent members to a predetermined optimum value while suppressing the temperature drop. Specifically, in the case of FIG. 5, the upper surface of the heat generating member 361b is a parallelogram or a trapezoid, and electrodes 361c and 361d are formed on the upper side and the lower side, respectively. Therefore, the side surfaces located at the boundary between the heat generating members 361b adjacent to each other are inclined at a predetermined angle with respect to the paper transport direction, and the opposite side surfaces are parallel to each other. Therefore, the creepage distance between the electrodes 361c and 361d between the adjacent heat generating members 361b can be increased as compared with the case of dividing the paper in parallel with the paper transport direction.

Further, as shown in FIG. 5, in the present embodiment, the heat generation pattern of the heating member 361 is composed of a plurality of types of heat generating members 361b corresponding to the size of the paper whose length in the left-right direction shown in the drawing is passed. ing. Specifically, heat generating members having a plurality of lengths corresponding to postcard size (100 x 148 mm), CD jacket size (121 x 121 mm), B5R size (182 x 257 mm), and A4R size (210 x 297 mm) ( Heat generating element) It is divided into 361b. The heat-generating member group consisting of the adjacent heat-generating members 361b has a margin of about 5% or about 10 mm with respect to the heated region in consideration of the transport accuracy of the paper to be conveyed, skew, and heat escape to the unheated portion. Is energized.

For example, in order to correspond to a width of 100 mm, which is the minimum size of a postcard, a first group of heat generating members is provided at the center in the main scanning direction (horizontal direction in the drawing), and the width is 105 mm. In order to correspond to the next largest sizes 121 mm and 148 mm, a second heat generating member group having a width of 50 mm is provided outside the first heat generating member group (in the left-right direction in the drawing), and 148 mm + 5% covers a width of up to 155 mm. In order to correspond to the larger sizes of 182 mm and 210 mm, a third heat generating member group having a width of 65 mm is provided on the outer side of the second heat generating member group to cover a width of up to 220 mm at 210 mm + 5%. .. The number of divisions of the heat generating member group and the width of each are given as an example, and are not limited thereto. For example, when the MFP 10 corresponds to five medium sizes, the heat generating member group may be divided into five according to each medium size.

Further, in the present embodiment, a line sensor (not shown) is arranged in the paper passing area, and the size and position of the passing paper can be determined in real time. The paper size may be determined from the image data or the information of the paper cassette 18 in which the paper in the MFP 10 is stored at the start of the printing operation.

FIG. 6 is a cross-sectional view illustrating the creepage distance between the heat generating members 361b after division. FIG. 6A is a cross-sectional view of the undivided heat generating member 361b in the longitudinal direction. Here, the case where only one heat generating member 361b having a thickness D1 is fixed on the ceramic substrate 361a which is an insulating layer is shown. Further, FIG. 6B shows a case where the heat generating member 361b is divided into a plurality of parts while maintaining the thickness of the heat generating member 361b at D1. Similar to the case of FIG. 6A, the heat generating member 361b (heating layer) is fixed on the ceramic substrate 361a. Since the heat generating member 361b (heating layer) is a conductor, D1 does not affect the creepage distance. Since the boundary portion is insulated, if the space distance between adjacent heat generating members 361b is G1, the creepage distance is G1. On the other hand, FIG. 6C shows the pattern of the heating member 361 in the present embodiment. The thickness of the heat generating member 361b (heating layer) is D1, which is the same as in the cases of FIGS. 6A and 6B, but as a separate insulating layer under the heat generating member 361b separately from the ceramic substrate 361a. A block-shaped ceramic substrate 361a'is provided. The upper surface of the ceramic substrate 361a'has the same shape as the lower surface of the divided heat generating member 361b. By separately providing the ceramic substrate 361a'with a thickness of D2, the space distance between the adjacent heat generating members 361b is G2, which is shorter than G1, but the creepage distance is 2 × D2 + G2. That is, it has been shown that instead of shortening the spatial distance, adjusting the creepage distance to a longer value suppresses the temperature drop at the boundary portion and at the same time takes safety measures.

FIG. 7 is a diagram showing a connection state between the heat generating member group and its drive circuit. As shown in the figure, the heating member 361b is controlled to be energized individually or for each group at a symmetrical position with respect to the central portion by the corresponding drive IC 151. Each heat generating member 361b is connected in parallel as a whole so that the same potential is applied to each of them, but the pair of heat generating members 361b located symmetrically with respect to the central portion are connected to each other in a parallel circuit. They are connected in series and are driven and controlled by the same drive IC 151. Since the number of drive ICs 151 can be made smaller than the number of divisions of the heat generating member 361b, the number of drive ICs 151 can be reduced, and the device size and manufacturing cost can be suppressed.

Specific examples of the drive IC 151, which is a switching unit for energizing each heat generating member 361b, include a switching element, a FET, a triax, a switching IC, and the like. FIG. 7 shows a configuration example in which a voltage is applied to each of the heat generating members 361b by alternating current to generate heat, but direct current can also be used.

For example, when the paper P has the minimum size (postcard size), only the drive IC 151 of the heat generating member 361b (first heat generating member group) arranged in the center is turned on and heated. As the size of the paper P increases, the drive IC 151 of the second heat generating member group and the third heat generating member group is also controlled to be turned ON in sequence. It is assumed that the electric resistance values of the first to third heat generating member groups are adjusted so as to have a uniform temperature rise rate.

Further, in FIG. 7, since the current supplied from the power supply flows in four parts, a safety element 152 is provided for each parallel circuit as in the drive IC 151. When the temperature detection result of the temperature detection member 362 (not shown) that measures the surface temperature of the corresponding heat generating member 361b is "abnormal temperature detection", the safety element 152 controls the drive IC 151 to drive the electric circuit. It is an element that blocks.

Hereinafter, the operation of the MFP 10 configured as described above at the time of printing will be described with reference to the drawings. FIG. 8 is a flowchart showing a specific example of control of the MFP 10 in the present embodiment.

First, when the image data is read by the scanner unit 15 (Act101), the image formation 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 formation process is started, the read image data is processed (Act102), the electrostatic latent image is written on the surface of the photoconductor drum 22 (Act103), and the electrostatic latent image is developed by the developing device 24. (Act104), proceed to Act114.

When the fixing temperature control process is started, for example, the paper size is determined based on the detection signal of the line sensor (not shown) and the paper selection information by the operation unit 14 (Act105), and the position (passing) through which the paper P passes is determined. A group of heat generating members arranged in the paper region) is selected as a heat generating target (Act106).

Next, when the temperature control start signal for the selected heat generating member group is turned ON (Act107), the selected heat generating member group is energized and the surface temperature of the heat generating member group rises. That is, once the heating region is determined, all the selected heat generating members 361b are operated under the same control. At this time, the energized heat generating member 361b generates heat at a uniform temperature rise rate.

Next, when the surface temperature of the heat generating member group is detected by the temperature detecting member (not shown) arranged inside or outside the endless belt 363 (Act108), is the surface temperature of the heat generating member group within a predetermined temperature range? Whether or not it is determined (Act109). Here, if it is determined that the surface temperature of the heat generating member group is within a 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 (Act109: No), the process proceeds to Act111.

In Act111, 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 a predetermined temperature upper limit value (Act111: Yes), the energization of the heat generating member group selected in Act106 is turned off (Act112). Return to Act108. 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 (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 (Act113), and the process returns to Act108.

Next, when the paper P is conveyed to the transfer unit (Act110) while the surface temperature of the heat generating member group is within a predetermined temperature range, the paper P is fixed after the toner image is transferred to the paper P (Act114). Transport within 36.

Next, when the toner image is fixed on the paper P in the fixing device 36 (Act115), it is determined whether or not to end the printing process of the image data (Act116). Here, when it is determined that the printing process is finished (Act116: Yes), the energization of all the heat generating member groups is turned off (Act117), and the process is finished. On the other hand, when it is determined that the printing process of the image data has not been completed (Act116: No), that is, when the image data to be printed remains, the process returns to Act101 and the same process is repeated until the process is completed. ..

As described above, according to the present embodiment, by switching the heat generating member group to be generated based on the group to which the paper size to be used belongs, not only the abnormal heat generation of the non-passing portion can be prevented, but also the non-passing paper can be prevented. Unnecessary heating of the part can be suppressed. Therefore, it is possible to significantly reduce the heat energy consumed by the fixing device 36. Further, since the creepage distance between the electrodes formed at both ends and the creepage distance or the spatial distance at the boundary portion between the adjacent heat generating members 361b are adjusted so as not to cause a temperature drop at the boundary portion, the creepage distance at the boundary portion is adjusted. While suppressing the temperature drop, safety measures can be taken at the same time. As a result, the temperature unevenness of the heating member 361 in the paper passing region is eliminated, and the fixing quality can be improved.

<Modification example>
Hereinafter, some modifications of the above embodiment will be described in detail with reference to the drawings.
FIG. 9 is a cross-sectional view showing a fixed structure of the heat generating member 361b and the ceramic substrate 361a in the modified example of the above embodiment. Here, the upper surface of the ceramic substrate 361a to which the plurality of heat generating members 361b are fixed is formed in a curved shape, and the creepage distance and the space distance are adjusted by the angle of curvature on the upper surface and the fixing positions of the heat generating members 361b. It is shown. As shown in FIG. 9, since a plurality of heat generating members 361b are fixed on the curved surface of the crown-shaped ceramic substrate 361a, the space distance at the boundary portion between the adjacent heat generating members 361b is shortened, but the creepage surface is correspondingly reduced. The distance can be increased. Each of the heat generating members 361b may be independently patterned and attached to the ceramic substrate 361a, or may be formed by a method of simultaneously forming a pattern of the resistance heat generating layer on the ceramic substrate 361a as described above.

10 and 11 are diagrams showing other shape patterns of the heat generating member group in the modified example of the above embodiment. In FIG. 10, the boundary portion between the adjacent heat generating members 361b is formed into a bent shape, and the facing surfaces are formed to be parallel to each other at this boundary portion, so that the creepage distance between the electrodes 361c and 361d is adjusted. It is shown that

In addition, when paper of different sizes is conveyed and printed during continuous printing (especially when paper of a small size to a larger size is printed), a heat generating member that generates heat corresponding to the paper size. In order to secure the time until the temperature detection result of the temperature detection member 362 according to 361b becomes the same between the members, it is preferable to control by a fixing control program so as to extend the paper transfer interval or slow down the transfer speed. Is.

Further, the length of the heat generating member 361b after the division is preferably adjusted so that the boundary portion is outside the end portion of the paper passing region, because the influence from the boundary portion can be suppressed to be small.

Further, in the above embodiment, the size of the paper passing area of the paper P is determined based on the paper setting information before the paper P is conveyed into the fixing device 36. Alternatively, the position through which the print area (image forming area) passes can be determined and heated. As a method of determining the size of the print area of the paper P, a method of using the analysis result of the image data, a method based on print format information such as a margin setting for the paper P, and a method of determining based on the detection result of the optical sensor. And so on. In this case, since only the portion that needs to be fixed can be heated in a limited manner, the energy saving efficiency can be further improved.

On the other hand, FIG. 11 shows a case where the rectangular heat generating member 361b is fixed on the ceramic substrate 361a so as to be inclined by a certain angle with respect to the paper transport direction indicated by the arrow A. When the heat generating member 361b is formed in a parallelogram or trapezoidal shape as shown in FIG. 5, the current flows in the member at the shortest distance. Therefore, depending on the size of the heat generating member 361b, even among the same heat generating members 361b There will be a difference in the ease of heat generation. Therefore, as shown in FIG. 11, the rectangular heat-generating member 361b having the same distance between the electrodes 361c and 361d is arranged so as to be inclined with respect to the paper transport direction, so that the energization conditions and the heat-generating conditions are made uniform. Can be done.

Although the embodiments of the present invention have been described above, the present 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.

36 ... Fixing device 150 ... Fixing control circuit 151 ... Drive IC
361 ... Heating member 361a ... Ceramic substrate 361b ... Heat generating member 361c, 361d ... Electrode 363 ... Endless belt 366 ... Pressurizing roller

The present embodiment relates to a heating member, a fixing device, and an image forming device.

The fixing device according to one embodiment includes a substrate and a plurality of heat generating members. The substrate has a plurality of insulating layer blocks arranged at intervals in a direction orthogonal to the transport direction of the medium, and an insulating layer in contact with one side surface of each of the plurality of the insulating layer blocks. The plurality of heat generating members are arranged on the other side surface of each of the plurality of insulating layer blocks, and each of them is energized to heat the medium.

Claims (5)

A determination means for determining the size of the medium on which the toner image is formed, and
The length of the endless rotating body in the transport direction of the medium is the same, and the medium is divided into a plurality of lengths in the direction perpendicular to the transport direction, and the creepage distance between the electrodes formed at both ends. A plurality of heat generating members arranged in contact with the inside of the rotating body, formed by adjusting the creepage distance or the space distance at the boundary portion after the division to a predetermined value, and energization of the electrodes of these heat generating members. A heating means for heating the medium, which has a switching unit for switching individually,
A pressurizing means for forming a nip by pressure contacting the heating means at the positions of the plurality of heat generating members and sandwiching and transporting the medium together with the heating means in the transport direction.
A heating control means for controlling heating in the heating means by selecting a heat generating member corresponding to a position through which the medium passes by the switching unit and energizing the plurality of heat generating members.
A fixing device characterized by being provided with. Claim 1 is characterized in that the creepage distance at the boundary portion is adjusted by arranging an insulating layer having the same surface shape and a predetermined thickness on the lower side of the plurality of divided heat generating members. The fixing device described. The creepage distance between the electrodes is adjusted by inclining the side surfaces located at the boundary portion at a predetermined angle with respect to the transport direction and forming the side surfaces facing each other to be parallel to each other. The fixing device according to claim 1 or 2. Claim 1 or claim 1, wherein the creepage distance between the electrodes is adjusted by forming the side surfaces of the boundary portion into a bent shape and forming the side surfaces facing each other in parallel at the boundary portion. The fixing device according to claim 2. A transfer belt that moves in one direction,
A photoconductor arranged along the moving direction of the transfer belt and holding an electrostatic latent image on the surface,
A developing device that is arranged to face the photoconductor and adheres the discharged toner to the electrostatic latent image to form a toner image on the photoconductor.
A transfer member that presses against the photoconductor via the transfer belt based on the supply of a transfer voltage and transfers the toner image formed on the photoconductor onto the transfer belt.
A fixing device that fixes the toner image on the transfer belt to the medium by pressurizing and heating.
With
The fixing device is
A determination means for determining the size of the medium on which the toner image is formed, and
The length of the endless rotating body in the transport direction of the medium is the same, and the medium is divided into a plurality of lengths in the direction perpendicular to the transport direction, and the creepage distance between the electrodes formed at both ends. A plurality of heat generating members arranged in contact with the inside of the rotating body, formed by adjusting the creepage distance or the space distance at the boundary portion after the division to a predetermined value, and energization of the electrodes of these heat generating members. A heating means for heating the medium, which has a switching unit for switching individually,
A pressurizing means for forming a nip by pressure contacting the heating means at the positions of the plurality of heat generating members and sandwiching and transporting the medium together with the heating means in the transport direction.
A heating control means for controlling heating in the heating means by selecting a heat generating member corresponding to a position through which the medium passes by the switching unit and energizing the plurality of heat generating members.
An image forming apparatus characterized by having.

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