JP2008123709A - Heating body, fixing device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an increase of a temperature of a paper non-passing part region even when a recording material is conveyed lopsidedly to a longitudinal direction of a heating body. <P>SOLUTION: Resistance heating elements 102, 103 provided on the heating body 100 have different heating distributions from each other in the longitudinal direction of the heating body, and the respective resistance heating elements have different heating values per unit area in regions of both end parts in the longitudinal direction of the heating body. Furthermore, power supply rates to the respective resistance heating elements are controlled depending on a detection state of a recording material detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a function of forming an image on a recording material, such as a copying machine or a printer, and more particularly, a heating body including a resistance heating element, and a fixing device including the heating body. It is about.

  2. Description of the Related Art Conventionally, a recording material heat fixing apparatus for image heat fixing or the like sandwiches a recording material as a material to be heated by a heating roller maintained at a predetermined temperature and a pressure roller pressed against the heating roller. A heat roller system that heats while carrying is often used. In addition, various systems and configurations such as a flash heating system, an open heating system, and a hot plate heating system are known and put into practical use.

  Recently, instead of such a method, an image heating fixing method (film heating method heating device) as described below has been devised (for example, see Patent Document 1).

  This includes a heating body (heater), a heating body support (stay), a heat-resistant film (fixing film) that is conveyed while being pressed against the heating body, and recording as a material to be heated via the fixing film. And a pressure body (pressure roller) for bringing the material into close contact with the heating body. In this method, the heat of the heating body is applied to the recording material through the fixing film to heat and fix the unfixed image formed and supported on the recording material surface to the recording material surface.

  As a heating body of this heat fixing apparatus, a structure in which a resistance heating element is formed on a ceramic substrate, the resistance heating element is heated by power feeding, and the recording material is heated is general. The temperature of the heating body is detected by a temperature measuring element such as a thermistor that is in contact with or bonded to the heating body, and the temperature is controlled by a CPU that is a control means based on the detected temperature.

In such a film heating type heat fixing apparatus or image heating apparatus, a low heat capacity heating body can be used as the heating body. For this reason, it is possible to save power and shorten the wait time (quick start) as compared with conventional devices such as a heat roller method and a belt heating method.
JP-A-4-44075 JP-A-4-44076 JP-A-4-44077 JP-A-4-44078 JP-A-4-44079 JP-A-4-44080 JP-A-4-44081 JP-A-4-44082 JP-A-4-44083 JP-A-4-204980 JP-A-4-204981 JP-A-4-204982 JP-A-4-204983 JP-A-4-204984

  However, with the recent increase in processing capacity of the heat fixing device, it is necessary for the heat fixing device to heat a large number of recording materials in a certain time. Accordingly, the amount of heat generated in the heating body is increasing.

  By increasing the amount of heat generated in the heating body in this way, the temperature difference between the sheet passing area and the non-sheet passing area of the recording material becomes larger, and the problem that the temperature of the non-sheet passing area increases is more prominent. It has become to.

  In other words, in the paper passing area, the heat generated from the heating element is consumed by the recording material, but in the non-paper passing area, there is no consumption by the recording material, so heat gradually accumulates, causing a temperature rise. To do. As the speed increases, the supply to the recording material in a certain time increases, so the temperature rise in the non-sheet passing portion increases.

  Such a temperature rise in the non-sheet passing portion region has a problem that it is necessary to improve the heat resistance of the member used in the region, and it is necessary to improve the stability of the performance of the member in a high temperature state. Therefore, measures are desired.

  The temperature rise of the non-paper portion area as described above increases under the condition that the width of the non-paper passage area is wide.

There are the following two states as the state where the width of the non-sheet passing portion region is widened.
(Condition 1) A state where a recording material having a narrower width than a recording material having the maximum width capable of passing paper is passed.
(Condition 2) In a configuration in which the sheet passing reference of the recording material is the center, the sheet passing position is conveyed toward either of the longitudinal ends with respect to the center.

  When the conditions of condition 1 and condition 2 overlap, the width of the non-sheet passing area increases, and the temperature of the non-sheet passing area increases.

  In the conventional heat fixing apparatus, when the recording material having a narrow width shown in the condition 1 is passed, the recording material to be passed in a predetermined time is reduced by widening the interval between the recording material and the recording material. ing.

  By reducing the number of recording materials that are passed during a certain period of time, the amount of heat accumulated in the non-sheet passing area is reduced, and the temperature is reduced by securing a time for equalizing the temperature in the longitudinal direction.

  Regarding the deviation in the longitudinal direction of the recording material shown in Condition 2, the width of the non-sheet passing area on the opposite side of the recording material in the longitudinal direction is widened and is not consumed by the recording material in the non-sheet passing area on one side. This is a state in which the amount of heat increases and the temperature further increases. This deviation in the longitudinal direction of the recording material is very large when considering the worst of the state where the user has set the recording material close to the reference position on one side, and the temperature is very high. The rise will increase.

  Therefore, when the configuration that reduces the number of recording materials to be passed in a certain time by widening the interval between the recording materials described above, it is necessary to significantly reduce the number of recording materials to be passed, and a countermeasure is desired. ing.

  The present invention has been made in view of the above-described circumstances, and it is possible to reduce the temperature rise in the non-sheet passing portion region even when the recording material is transported to one side in the longitudinal direction of the heating body. Objective.

In order to achieve the above object, the present invention provides:
In the heating element provided with a resistance heating element provided along the longitudinal direction of the substrate and provided in the short direction of the substrate,
At least two resistance heating elements among the plurality of resistance heating elements have different heat generation distributions in the longitudinal direction and have different heat generation amounts per unit area in both end regions in the longitudinal direction.

In addition, in a heating element provided with a resistance heating element provided along the longitudinal direction of the substrate and provided in the short direction of the substrate,
At least two resistance heating elements among the plurality of resistance heating elements are provided such that at least widths in the short direction in both end regions in the longitudinal direction are different from each other at the same position in the longitudinal direction. To do.

In addition, in a heating element provided with a resistance heating element provided along the longitudinal direction of the substrate and provided in the short direction of the substrate,
At least two resistance heating elements among the plurality of resistance heating elements are provided such that resistance values per unit area at least in the both ends in the longitudinal direction are different from each other at the same position in the longitudinal direction. To do.

  According to the present invention, even when the recording material is conveyed toward one side in the longitudinal direction of the heating body, it is possible to reduce the temperature rise in the non-sheet passing portion region.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram of an example of an image forming apparatus applicable to the present invention. The image forming apparatus of this embodiment is a laser beam printer using an electrophotographic process.

  Reference numeral 1 denotes an electrophotographic photosensitive drum (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow.

  Reference numeral 2 denotes charging means such as a contact charging roller, and the surface of the photosensitive drum 1 is uniformly charged (primarily charged) to a predetermined polarity and potential by the charging means.

  Reference numeral 3 denotes a laser beam scanner as an image exposure means, which outputs a laser beam L modulated on / off in accordance with an electric digital pixel signal of target image information input from an external device, and charges the photosensitive drum 1. The processing surface is subjected to scanning exposure (irradiation). By this scanning exposure, the charge of the exposed bright portion on the surface of the photosensitive drum 1 is eliminated, and an electrostatic latent image corresponding to the target image information is formed on the surface of the photosensitive drum 1.

Reference numeral 4 denotes a developing device. Developer (toner) is supplied from the developing sleeve 4a to the surface of the photosensitive drum 1, and the electrostatic latent image on the surface of the photosensitive drum 1 is sequentially developed as a toner image which is a transferable image. .

  Reference numeral 5 denotes a feeding cassette on which the recording material P is loaded and stored.

  The feeding roller 6 is driven, and the recording material P in the feeding cassette 5 is separated and fed one by one, passes through the registration roller 7 and the sheet path 8a, and the photosensitive drum 1 and the transfer roller 9 as a transfer member. Are introduced at a predetermined timing into the transfer portion T, which is the contact nip portion of the. In other words, when the leading edge of the toner image on the photosensitive drum 1 reaches the transfer site T, the recording material P is conveyed by the registration roller 7 so that the timing of the leading edge of the recording material P also reaches the transfer site T. Is controlled.

  The recording material P introduced into the transfer site T is nipped and conveyed by the transfer site T, and a transfer voltage (transfer bias) controlled in a predetermined manner from a transfer bias application power source (not shown) is applied to the transfer roller 9 during that time. . A transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 9, whereby the toner image on the surface of the photosensitive drum 1 is electrostatically transferred to the surface of the recording material P at the transfer portion T.

  The recording material P that has received the transfer of the toner image at the transfer portion T is separated from the surface of the photosensitive drum 1 and is transported and introduced into the heat fixing device (fixing device) 11 through the sheet path 8b to heat and pressurize the toner image. Receive fixing process. As a result, the unfixed image is fixed on the recording material P.

  On the other hand, the surface of the photosensitive drum 1 after separation of the recording material (after transfer of the toner image to the recording material P) is cleaned by the cleaning device 10 after removal of transfer residual toner, paper dust, etc., and is repeatedly used for image formation. Is done.

  The recording material P that has passed through the heat fixing device 11 is guided to the sheet path 8c side and discharged onto the discharge tray 14 from the discharge port 13.

  Next, the heat fixing device 11 in the present invention will be described.

  FIG. 3 is a schematic configuration diagram of a film heating type heat fixing apparatus applicable to the present invention. This device is a tensionless type device disclosed in Patent Documents 1 to 14 and the like.

  This tensionless type film heating type heat fixing device is as follows. That is, an endless belt-like or cylindrical heat-resistant member is used, and at least a part of the circumference of the film is always tension-free (a state in which no tension is applied). It is a device that is driven to rotate.

  Reference numeral 21 denotes a stay, which is a heat resistant and rigid member as a support (holding member) and a film guide member for fixing and supporting the heating body. Reference numeral 100 denotes a ceramic heater as a heating body, which is disposed and held on the lower surface of the stay 21 along the length of the stay.

  Reference numeral 22 denotes an endless (cylindrical) heat-resistant film that is externally fitted to a stay 21 that is a film guide member including the heating body 100. The inner peripheral length of the endless heat-resistant film 22 and the outer peripheral length of the stay 21 including the heating body 100 are larger than the film 22 by, for example, about 3 mm. Therefore, the film 22 is externally fitted with a margin in the peripheral length. ing.

  The stay 21 can be composed of a high heat-resistant resin such as polyimide, polyamideimide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins with ceramics, metal, glass, or the like. In this example, a liquid crystal polymer was used.

  For the film 22, a single layer film such as PTFE, PFA or FEP having a heat resistance with a film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more is used in order to reduce the heat capacity and improve the quick start property. . Alternatively, a composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of a film such as polyimide, polyamideimide, PEEK, PES, PPS, or SUS is used. In this example, a polyimide film having a film thickness of about 50 μm coated with PTFE on the outer peripheral surface was used. The outer diameter of the film 22 was 18 mm.

  Reference numeral 24 denotes a pressure roller as a pressure member (film outer surface contact driving means) that forms a nip portion N with the film 22 interposed between the heating body 100 and rotationally drives the film 22. The pressure roller 24 is composed of a cored bar, an elastic layer, and an outermost release layer. The pressure roller 24 is pressed against the surface of the heating body 23 with a predetermined pressing force by a bearing means and a biasing means (not shown). Are arranged. In this embodiment, the core metal is aluminum, the elastic layer is silicone rubber, and the release layer is a PFA tube having a thickness of about 30 μm. The outer diameter of the pressure roller 24 was 20 mm, and the thickness of the elastic layer was 3 mm.

  The pressure roller 24 is rotationally driven at a predetermined peripheral speed in the direction of the arrow by a drive system (not shown). By the rotational driving of the pressure roller 24, a rotational force acts on the film 22 by the frictional force between the pressure roller and the film outer surface in the nip portion N. As a result, the film 22 is driven in the direction of the arrow around the outer periphery of the stay 21 in the direction of the arrow at the same peripheral speed as that of the pressure roller 24 while the inner surface of the film 22 slides in close contact with the surface of the heating body 23 at the nip N. Rotating state.

  FIG. 1 is a diagram illustrating a configuration of a heating body 100 and a circuit for performing energization control in the present embodiment.

  The heating element 100 includes a substrate (heating element substrate) 101, two resistance heating elements 102 and a resistance heating element 103, a heat-resistant overcoat layer (not shown) that protects the surface of the heating element on which the resistance heating elements are formed, This is a heating body having a low heat capacity as a whole consisting of the power supply electrodes 104, 105 and 106. Here, the substrate 101 is an elongated heat-resistant / insulating / good thermal conductive substrate whose longitudinal direction is substantially perpendicular to the conveying direction of the recording material P as a material to be heated. In addition, the resistance heating element 102 and the resistance heating element 103 are respectively formed on the surface (film sliding surface) side of the substrate 101 along the longitudinal direction of the substrate, and the resistance heating element 102 and the resistance heating element 103 are recorded. It is provided side by side in the conveyance direction (substrate short direction) of the material P. Further, the power supply electrodes 104, 105, and 106 are disposed at the longitudinal ends of the resistance heating element 102 and the resistance heating element 103.

The resistance heating elements 102 and 103 of this embodiment are formed by forming a paste prepared by kneading silver, palladium, glass powder (inorganic binder), and organic binder into a line band shape on the substrate 101 by screen printing. It was obtained. As a material for the resistance heating element, an electrical resistance material such as RuO ₂ or Ta ₂ N may be used in addition to silver palladium (Ag / Pd). The resistance value of the resistance heating element was 40Ω at room temperature.

  Reference numeral 101 denotes a substrate having heat resistance and insulation, and for example, a ceramic material such as alumina or aluminum nitride is used. In this embodiment, an alumina substrate having a width of 7 mm, a length of 370 mm, and a thickness of 1 mm is used. Silver-palladium screen printing patterns were used for the power supply electrodes 104, 105, and 106. The overcoat layer (not shown) is mainly intended to ensure electrical insulation between the resistance heating elements 102 and 103 and the surface of the heating body 100 and the slidability of the film 22. In this example, a heat-resistant glass layer having a thickness of about 50 μm was used.

  FIG. 1 also shows the back side 100b (non-film sliding surface) of the heating body 100.

Reference numeral 31 denotes a temperature measuring element provided for detecting the temperature of the heating body. In this embodiment, an external contact type thermistor separated from the heating body 100 is used as the temperature measuring element.

  This external contact type thermistor 31 is provided with a heat insulating layer on a support, for example, and an element of a chip thermistor is fixed thereon, and the element is directed downward (on the back side of the heating body) with a predetermined pressure to be heated. It is configured to contact the back surface. In this example, a highly heat-resistant liquid crystal polymer was used as the support, and ceramic paper was laminated as the heat insulating layer. The external contact type thermistor 31 is provided in the minimum sheet passing area, and is connected to a CPU 32 that controls the apparatus.

  The heating body 100 is fixedly disposed by holding the resistance heating elements 102 and 103 on the lower surface side of the stay 21 with the surface side exposed downward.

  With the configuration as described above, the entire heating element can be reduced in heat capacity as compared with the heat roller system, and a quick start is possible.

  The heating element 100 rises in temperature when the resistance heating elements 102 and 103 generate heat by supplying power to the power supply electrodes 104, 105, and 106 at the longitudinal ends of the resistance heating element. The temperature rise is detected by the external contact type thermistor 31, and the output of the external contact type thermistor 31 is A / D converted and taken into the CPU 32. Based on the information, the CPU 32 controls the electric power supplied to the resistance heating elements 102 and 103 by the triac 33 for the resistance heating element 102 and the triac 34 for the resistance heating element 103 by phase control or wave number control, etc. 100 temperature control is performed.

  That is, the heating body 100 is fixed by controlling energization so that the heating body 100 is heated when the temperature detected by the external contact type thermistor 31 is lower than a predetermined set temperature, and the temperature is lowered when the temperature is higher than the set temperature. At a constant temperature. In this embodiment, the resistance heating element 102 and the resistance heating element 103 can be controlled independently of each other, and the energization ratio between the resistance heating element 102 and the resistance heating element 103 is controlled by the CPU 32 as an energization control means (control device). The

  A nip formed by the heating body 100 and the pressure roller 24 with the film 22 sandwiched in a state in which the temperature of the heating body 100 rises to a predetermined level and the rotation peripheral speed of the film 22 by the rotation of the pressure roller 24 becomes steady. A recording material P to be image-fixed is introduced into the portion N from the transfer portion. Then, the recording material P is nipped and conveyed together with the film 22 at the press nip portion N, so that the heat of the heating body 100 is applied to the recording material P through the film 22 and the unfixed visible image (toner) on the recording material P. Image) is heat-fixed on the recording material P surface. The recording material P that has passed through the nip portion N is separated from the surface of the film 22 and conveyed.

  Next, the structure of the heating body 100 used in the present embodiment will be described in more detail with reference to FIG.

  In FIG. 1, reference numeral 100a denotes a heating element forming surface of the heating element, and 100b denotes a surface opposite to the heating element forming surface of the heating element.

  As described above, the reference numerals 102 and 103 on the heating body 100 are resistance heating elements that can be energized independently, and are formed on the substrate.

The resistance heating elements 102 and 103 are, in the longitudinal direction, portions of a central region A (region with a width of 210 mm that is 105 mm to the left and right from the central reference line X), an end region B (width 45 mm), and an end region C (width 45 mm). It consists of The resistance heating elements 102 and 103 are configured to have different widths of the resistance heating elements (dimensions in the substrate short direction (recording material conveyance direction)) in the end region B and the end region C, respectively.

  In the resistance heating element 102, the width of the resistance heating element in the end region B becomes wider toward the end compared to the width of the resistance heating element in the central region A, and the resistance heating element width in the end region C is larger than that of the central region A. Compared to the resistance heating element width, the width becomes narrower toward the end. Therefore, the resistance heating element width of the end region C is narrower than the resistance heating element width of the end region B.

  In contrast, in the resistance heating element 103, the resistance heating element width in the end region B becomes narrower toward the end compared to the resistance heating element width in the central region A, and the resistance heating element width in the end region C is the central part. Compared to the width of the resistance heating element in the region A, the width increases toward the end. Therefore, the resistance heating element width in the end region C is thicker than the resistance heating element width in the end region B.

  The distribution of the heat generation amount in the longitudinal direction in the heating body 100 having the above configuration is shown in FIGS.

  4 shows the distribution of the heat generation amount in the longitudinal direction of the resistance heating element 102, and FIG. 5 shows the distribution of the heat generation amount in the longitudinal direction of the resistance heating element 103. The calorific value is shown as a ratio when the calorific value per unit area in the central region A is 100%.

  The amount of heat generated by the resistance heating element is small when the width of the resistance heating element is wide, and increases when the width is narrow. Therefore, in the end region B of the resistance heating element 102 shown in FIG. 4, the heat generation amount decreases as it goes to the end portion, and conversely, in the end region C, the heat generation amount increases as it goes to the end portion. It is.

  Further, in the end region B of the resistance heating element 103 shown in FIG. 5, the heat generation amount increases toward the end portion, and conversely, in the end region C, the heat generation amount decreases toward the end portion. It is.

  Further, the total heat generation amount of the two resistance heating elements 102 and 103 is configured to be the same in each part in the longitudinal direction of the heating element.

  Next, energization control of the heating body in the present embodiment will be described.

  FIG. 6 is a diagram showing a conveyance state of the recording material.

  The broken line in the figure is the center reference line X of the heat fixing device, and the recording material is conveyed so that the center in the width direction is along the center reference line X. In addition, the resistance heating elements 102 and 103 in the heating body 100 are equally arranged on the left and right with respect to the central reference line X.

  Reference numerals 35 and 36 denote recording material detection elements as recording material detection means provided in the recording material conveyance path, which detect the presence or absence of conveyance of the recording material at the position of the recording material detection element and control the heating and fixing device 11. A signal is sent to the CPU 32 to perform. The recording material detection elements 35 and 36 are arranged at a position 110 mm from the center reference line X to the left and right (substrate longitudinal direction). The recording material detection elements 35 and 36 may be provided on the heating body 100.

In the figure, P is a recording material, and shows the following four recording material conveyance states.
(Conveyance state 1) A3 size (width 297 mm) is conveyed around the center reference line X.
(Conveyance state 2) A4 size length (width 210 mm) is conveyed around the center reference line X. (Conveyance state 3) A4 size length (width 210 mm) is conveyed toward the recording material detection element 35 side.
(Conveyance state 4) A4 size vertical (width 210 mm) is conveyed toward the recording material detection element 36 side.

  As shown in Table 1, the above state can be determined by a combination of the recording material detection element 35 and the recording material detection element 36.

  Table 1 is a table showing the energization ratio of the resistance heating element 102 and the resistance heating element 103 to the outputs of the recording material detection elements 35 and 36. 7, 8, and 9 are diagrams showing the heat generation amount per unit area in the longitudinal direction of the heating body in the recording material conveyance states of the conveyance states 1 to 4. The calorific value is the sum of the calorific values of the resistance heating elements 102 and 103, and the calorific value of the central region A is expressed as 100%.

  The control operation of the heating body in each recording material conveyance state is shown below.

  The CPU 32 which is a control device controls the ratio of energizing the resistance heating elements 102 and 103 based on the output signals from the recording material detection elements 35 and 36.

  In the conveyance state 1 and the conveyance state 2, since the recording material is conveyed right and left evenly with respect to the center reference line X, the resistance heating element 102 and the resistance heating element 103 have the same ratio (1: 1). The energization is controlled at. The distribution of heat generation in the longitudinal direction of the heating body is uniform as shown in FIG.

  As shown in Table 1, the conveyance state 3 is a state in which the recording material detection element 35 detects the recording material and the recording material detection element 36 does not detect the recording material. In this transport state 3, the recording material P is transported in a state of being closer to the recording material detection element 35 with respect to the central reference line X, and is not passed on the end region C side (right side in the figure). The width of the paper area is increased.

  In this state, the energization ratio of the resistance heating element 103 is made larger than the energization ratio of the resistance heating element 102. In this state, the heat generation ratio of the entire heating element 100 including the resistance heating element 102 and the resistance heating element 103 in the entire longitudinal direction is as shown in FIG. As shown in FIG. 8, the amount of heat generated on the side where the non-sheet passing area of the end area C (the right side in the figure, the area where the recording material detection element 36 that does not detect the recording material is provided) is widened is reduced. The The total amount of heat generation in the end region C is reduced by 12.5% compared to the conveyance state 1.

As shown in Table 1, the transport state 4 is a state in which the recording material detection element 36 detects the recording material and the recording material detection element 35 does not detect the recording material. In the transport state 4, the recording material P is transported in a state of being closer to the recording material detection element 36 with respect to the center reference line X, and the non-passage on the end region B side (left side in the figure). The width of the paper area is increased.

  In this state, the energization ratio of the resistance heating element 102 is made larger than the energization ratio of the resistance heating element 103. The heat generation ratio of the entire heating element 100 including the resistance heating element 102 and the resistance heating element 103 in that state is as shown in FIG. As shown in FIG. 9, the amount of heat generation on the side where the non-sheet passing area of the end area B (the left side in the figure, the area where the recording material detection element 35 that does not detect the recording material is provided) is widened is reduced. The The total amount of heat generated in the end region B is reduced by 12.5% compared to the conveyance state 1.

  Next, the amount of heat generated in the non-sheet passing regions at both ends when the recording material P is shifted 10 mm to the left side (detection element 35 side) in the drawing in the conveyance state 3 will be described.

  The width of the non-sheet passing area on the right side in the figure is increased by 10 mm from the normal 45 mm to 55 mm, and thus increases by 22%. However, since the heat generation amount in the end region C is reduced by 12.5% as described above, it can be reduced to a total increase of 6.9%.

  On the other hand, the width of the non-sheet passing area on the left side in the figure is reduced by 22% because it is reduced by 10 mm to 35 mm from the usual 45 mm. In the control described above, the heat generation amount in the end region B is increased by 12.5%, but the total heat amount is not increased.

  As described above, when the recording material P is conveyed to the left and right with respect to the central reference line X, the amount of heat generated by the heating body 100 on the side where the non-sheet passing portion area is widened is reduced. The temperature rise can be reduced by reducing the amount of heat generation in the paper passing area.

  In addition, the amount of heat generated by the heating element on the side where the non-sheet-passing area is narrowed is increased, but the amount of heat generated in the non-sheet-passing area decreases as the width decreases, so the temperature of the non-sheet-passing area increases. I will not let you. Therefore, there is no problem with the image defect of the recording material P and the performance of the member due to the temperature rise.

  In FIG. 20, the structure of the heating body 600 of a prior art example is shown as a comparison.

  The resistance heating elements 602 and 603 in the heating body 600 of the conventional example are configured with the same width in the longitudinal direction, and the heat generation amount per unit area in the longitudinal direction of the heating body is uniform in the longitudinal direction.

  In the energization control of the heating element 600, the resistance heating element 602 and the resistance heating element 603 are energized at the same ratio (1: 1) regardless of the conveyance state of the recording material.

  In the configuration using the heating element 600 as the conventional example as described above and the configuration of the first embodiment of the present invention, the recording material P is 10 mm on the end region B side as in the recording material conveyance state 3 shown in FIG. The temperature of the heating body in the end region C when 10 sheets were passed in the gathered state was measured. The temperature of the heating body was controlled so that the temperature detection element 31 at the center was 190 ° C., and the recording material P was 80 g paper.

  In the configuration of the conventional example, the maximum temperature of the heating body is 230 ° C., whereas in the form of this embodiment, the maximum temperature is 210 ° C., and the maximum temperature of the heating body in the non-sheet passing portion region is reduced by 20 ° C. I was able to.

  In the present embodiment, the width of the resistance heating element is gradually changed from the central region A toward both longitudinal ends.

  As a result, the amount of heat generation can be gradually changed in the longitudinal direction, so that there is no partial sudden change in the amount of heat generation.

  Therefore, thermal stress due to a partial temperature difference in the longitudinal direction of the heating body can be reduced, and there is no occurrence of an abrupt temperature difference in the longitudinal direction even in a member such as a pressurizing body. A sufficient margin can be provided for poor conveyance.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected about the component similar to Example 1, and the description is abbreviate | omitted.

  The structure of the heating body used in the present embodiment will be described in detail with reference to FIG.

  The broken line in the figure is the center reference line X of the heat fixing device, and the recording material is conveyed so that the center in the width direction is along the center reference line X. The heating element 100 has the same configuration as that described in the first embodiment, and the resistance heating elements 102 and 103 of the heating element 100 are also arranged equally to the left and right with respect to the central reference line X.

  Reference numerals 37 and 38 denote external contact type thermistors which are temperature detecting elements as heating body temperature detecting means provided for detecting the temperature of the heating body. The temperature detection elements 37 and 38 are arranged at a position 127.5 mm on the left and right (substrate length) from the center reference line X, detect the temperature on the heating body, and send a signal to the CPU 32 that controls the heating and fixing device 11.

In FIG. 11, P is a recording material, and shows the following four recording material conveyance states.
(Conveyance state 1) A3 size (width 297 mm) is conveyed around the center reference line X.
(Conveyance state 2) A4 size length (width 210 mm) is conveyed around the center reference line X. (Conveyance state 3) A4 size vertical (width 210 mm) is conveyed near the temperature detection element 37 side.
(Conveyance state 4) A4 size vertical (width 210 mm) is conveyed close to the temperature detection element 38 side.

  The energization control for the resistance heating element 102 and the resistance heating element 103 in this embodiment will be described.

  Table 2 is a table showing the energization ratio of the resistance heating element 102 and the resistance heating element 103 depending on the difference in the detection temperature between the temperature detection elements 37 and 38. 12, 13, and 14 are diagrams showing the heat generation amount per unit area in the longitudinal direction of the heating body in the recording material conveyance states of the conveyance states 1 to 4. The calorific value is the sum of the calorific values of the resistance heating element 102 and the resistance heating element 103, and the calorific value of the central region A is expressed as 100%.

  The control operation of the heating body in each recording material conveyance state is shown below.

  The CPU 32 serving as a control device controls the ratio of energization to the resistance heating element 102 and the resistance heating element 103 based on output signals from the temperature detection elements 37 and 38.

  In the transport state 1 and the transport state 2, the recording material is transported equally to the left and right with respect to the center reference line X. For this reason, since the temperature difference T between the temperature detection element 37 and the temperature detection element 38 is in the range of 10 ° C. ≧ T ≧ −10 ° C., the resistance heating element 102 and the resistance heating element 103 have the same ratio (1: 1). The energization is controlled at. The distribution of the heat generation amount in the longitudinal direction of the heating body is uniform as shown in FIG.

  In the transport state 3, the recording material is transported in a state of being closer to the temperature detection element 37 side with respect to the center reference line X, and is a non-sheet passing region on the end region C side (right side in the drawing). Since the width becomes wider, the amount of heat generation increases. In this state, the detected temperature of the temperature detecting element 38 is higher than that of the temperature detecting element 37, and the energization ratio of the resistance heating element 103 is made larger than the energization ratio of the resistance heating element 102 in accordance with the temperature difference level. In this state, the heat generation ratio of the entire heating element including the resistance heating element 102 and the resistance heating element 103 is as shown in FIG.

  In the transport state 4, the recording material is transported in a state of being closer to the temperature detection element 38 side with respect to the center reference line X, and is a non-sheet passing region on the end region B side (left side in the drawing). Since the width becomes wider, the amount of heat generation increases. In this state, the detected temperature of the temperature detecting element 37 is higher than that of the temperature detecting element 38, and the energization ratio of the resistance heating element 102 is made larger than the energization ratio of the resistance heating element 103 according to the level of the temperature difference. In this state, the heat generation ratio of the entire heating element including the resistance heating element 102 and the resistance heating element 103 is as shown in FIG.

Thus, in this embodiment, when the detected temperature of one of the temperature detecting elements 37 and 38 is higher than the detected temperature of the other temperature detecting element by a predetermined value or more, one temperature detecting element The energization ratio is controlled so that the amount of heat generated in the area where the is disposed is reduced. A plurality of the predetermined values are set as shown in Table 2 (10 ° C., 20 ° C., 30 ° C.), and the corresponding energization ratio is set to increase as the value increases. The predetermined value may be set as appropriate, and an inequality sign indicating a range in Table 2 or an inequality sign with an equal sign may be set as appropriate.

  As described above, when the recording material is conveyed to the left and right with respect to the center reference line X, the non-sheet passing portion area becomes wider according to the level of the temperature difference detected by the temperature detecting elements 37 and 38. The amount of heat generated by the heating element on the side can be reduced, and the rise in the temperature of the non-sheet passing portion can be reduced.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the component similar to Example 1, and the description is abbreviate | omitted.

  The structure of the heating body used in the present embodiment will be described in detail with reference to FIG.

  The heating element 300 has a shape in which the heating element width of the resistance heating element 302 becomes wider toward the left side in the figure, and the heating element width of the resistance heating element 302 becomes wider toward the right side in the figure.

  The resistance heating element 302 gradually increases in heat generation toward the right end in the longitudinal direction of the figure.

  The resistance heating element 303 gradually increases in heat generation toward the left end in the longitudinal direction.

  Further, the total amount of heat generated by the resistance heating element 302 and the resistance heating element 303 is configured to be the same at the position in the longitudinal direction.

  Using the heating element having the above-described configuration, the amount of heat generated by the heating element on the side where the non-sheet passing portion area is widened can be reduced using the control in the first and second embodiments, and the temperature of the non-sheet passing portion can be reduced. The rise of the can be reduced.

  In the present embodiment, the width of the resistance heating element is gradually changed from the longitudinal end portion to the other end portion.

  As a result, the calorific value can be gradually changed in the longitudinal direction, so that there is no partial sudden calorific value change. Therefore, there is little thermal stress due to a partial temperature difference in the longitudinal direction of the heating body, and there is no sudden temperature difference in the longitudinal direction even in a member such as a pressurizing body. Enough margin.

  Next, Embodiment 4 of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the component similar to Example 1, and the description is abbreviate | omitted.

  The structure of the heating body used in the present embodiment will be described in detail with reference to FIG.

  The heating element 400 has a configuration in which the resistance value per unit area differs in the longitudinal direction of the heating element by changing the thickness of the resistance heating element (dimension in a direction substantially perpendicular to the substrate surface on which the resistance heating element is provided). . As the resistance heating element 402 goes to the right side in the figure, the thickness of the resistance heating element decreases, and the resistance value per unit area increases, so that the amount of heat generation increases. As the resistance heating element 403 goes to the left side in the figure, the thickness of the resistance heating element decreases, and the resistance value per unit area increases, so that the amount of heat generation increases.

  FIG. 17 and FIG. 18 show the distribution of heat generation in the longitudinal direction in the heating element configured as described above.

  FIG. 17 shows the distribution of the heat generation amount in the longitudinal direction of the resistance heating element 402, and FIG. 18 shows the distribution of the heat generation amount in the longitudinal direction of the resistance heating body 403. The calorific value is shown as a ratio when the calorific value per unit area at the center is 100%.

  The resistance heating element 402 gradually increases in heat generation toward the right end in the longitudinal direction of the figure.

  The resistance heating element 403 gradually increases in heat generation toward the left end in the longitudinal direction.

  Further, the total amount of heat generated by the resistance heating element 402 and the resistance heating element 403 is configured to be the same at the position in the longitudinal direction.

  By using the heating element having the above-described configuration, the amount of heat generated by the heating element on the side where the non-sheet passing portion area is widened can be reduced by using the control in the first and second embodiments, and the temperature of the non-sheet passing portion can be reduced. The rise of the can be reduced.

  In the present embodiment, the resistance value is changed depending on the thickness of the resistance heating element, but the same effect can be obtained even if the resistance value is changed by changing the material or the like.

  In the present embodiment, the resistance value per unit area of the resistance heating element is gradually changed from the end portion in the longitudinal direction toward the other end portion.

  As a result, the calorific value can be gradually changed in the longitudinal direction, so that there is no partial sudden calorific value change. Therefore, there is little thermal stress due to a partial temperature difference in the longitudinal direction of the heating body, and there is no sudden temperature difference in the longitudinal direction even in a member such as a pressurizing body. Enough margin.

  Next, Embodiment 5 of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the component similar to Example 1, and the description is abbreviate | omitted.

  The structure of the heating body used in the present embodiment will be described in detail with reference to FIG.

  In the heating element 500, the heating element length of the resistance heating element 502 is 5 mm longer on the left side in the figure than the resistance heating element 503, and conversely, on the right side in the figure, the heating element length of the resistance heating element 503 is larger than that of the resistance heating element 502. The shape is 5 mm long.

  Further, the total amount of heat generated by the resistance heating element 502 and the resistance heating element 503 is configured to be the same at the position in the longitudinal direction.

  Using the heating element having the above-described configuration, the amount of heat generated by the heating element on the side where the non-sheet passing portion area is widened can be reduced using the control in the first and second embodiments, and the temperature of the non-sheet passing portion can be reduced. The rise of the can be reduced.

The figure showing the circuit which performs a heating body and energization control concerning Example 1 of the present invention. 1 is a schematic configuration diagram showing a main part of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram of a fixing device according to the present invention. The figure showing the emitted-heat amount of the longitudinal direction of the resistance heating element which concerns on Example 1 of this invention. The figure showing the emitted-heat amount of the longitudinal direction of the resistance heating element which concerns on Example 1 of this invention. FIG. 3 is a diagram illustrating a conveyance state of a recording material according to the first embodiment of the invention. The figure showing the emitted-heat amount of the longitudinal direction of the heating body which concerns on Example 1 of this invention. The figure showing the emitted-heat amount of the longitudinal direction of the heating body which concerns on Example 1 of this invention. The figure showing the emitted-heat amount of the longitudinal direction of the heating body which concerns on Example 1 of this invention. The figure showing the circuit which performs the heating body which concerns on Example 2 of this invention, and energization control. FIG. 6 is a diagram illustrating a conveyance state of a recording material according to a second embodiment of the invention. The figure showing the emitted-heat amount of the longitudinal direction of the heating body which concerns on Example 2 of this invention. The figure showing the emitted-heat amount of the longitudinal direction of the heating body which concerns on Example 2 of this invention. The figure showing the emitted-heat amount of the longitudinal direction of the heating body which concerns on Example 2 of this invention. The figure showing the circuit which performs the heating body which concerns on Example 3 of this invention, and energization control. The figure showing the circuit which performs the heating body which concerns on Example 4 of this invention, and energization control. The figure showing the emitted-heat amount of the longitudinal direction of the resistance heating element which concerns on Example 4 of this invention. The figure showing the emitted-heat amount of the longitudinal direction of the resistance heating element which concerns on Example 4 of this invention. The figure showing the circuit which performs the heating body which concerns on Example 5 of this invention, and energization control. The figure showing the circuit which performs the heating body which concerns on a prior art example, and electricity supply control.

Explanation of symbols

11 Heat Fixing Device 31, 37, 38 Temperature Sensing Element 32 Control Device (CPU)
35, 36 Recording material detection element 100 Heating body 102, 103 Resistance heating element P Recording material X Center reference line

Claims (15)

In the heating element provided with a resistance heating element provided along the longitudinal direction of the substrate and provided in the short direction of the substrate,
The heating element, wherein at least two resistance heating elements among the plurality of resistance heating elements have different heat generation distributions in the longitudinal direction, and different amounts of heat generation per unit area in both end regions in the longitudinal direction.   The heating element according to claim 1, wherein the resistance heating element is provided so that a calorific value continuously changes in the longitudinal direction. In the heating element provided with a resistance heating element provided along the longitudinal direction of the substrate and provided in the short direction of the substrate,
At least two resistance heating elements among the plurality of resistance heating elements are provided such that at least widths in the short direction in both end regions in the longitudinal direction are different from each other at the same position in the longitudinal direction. Heating body to do.   The heating element according to claim 3, wherein the resistance heating element is provided so that the width continuously changes in the longitudinal direction. In the heating element provided with a resistance heating element provided along the longitudinal direction of the substrate and provided in the short direction of the substrate,
At least two resistance heating elements among the plurality of resistance heating elements are provided such that resistance values per unit area at least in the both ends in the longitudinal direction are different from each other at the same position in the longitudinal direction. Heating body to do.   The heating element according to claim 5, wherein the resistance heating element is provided such that a resistance value per unit area continuously changes in the longitudinal direction. A fixing device comprising the heating body according to any one of claims 1 to 6, wherein an unfixed image on a recording material is heated and fixed by the heating body.
A fixing device comprising: an energization control unit that independently controls energization of the at least two resistance heating elements. Provided with a recording material detection means for detecting the recording material,
The fixing device according to claim 7, wherein the energization control unit controls an energization ratio to the two resistance heating elements based on a detection result of the recording material detection unit. At least two recording material detection means are provided,
The two recording material detection means are respectively disposed in both end regions in the longitudinal direction of the heating body,
The energization control unit detects the recording material in a region where the recording material detection unit that detects the recording material is provided when any one of the two recording material detection units detects the recording material. The fixing device according to claim 8, wherein an energization ratio to the two resistance heating elements is controlled so that a heat generation amount in a region where the recording material detection unit is not provided is reduced. A heating element temperature detecting means for detecting the temperature of the heating element;
The fixing device according to claim 7, wherein the energization control unit controls an energization ratio to the two resistance heating elements based on a detection result of the heating body temperature detection unit. At least two heating body temperature detection means are provided,
The two heating body temperature detecting means are respectively disposed in both longitudinal end regions of the heating body,
The fixing device according to claim 10, wherein the energization control unit controls an energization ratio to the resistance heating element based on detection results of the two heating body temperature detection units.   When the temperature detected by one of the two heating element temperature detection means is higher than the detection temperature by the other heating element temperature detection means by a predetermined value or more, the energization control means The fixing device according to claim 11, wherein an energization ratio to the two resistance heating elements is controlled so that a heat generation amount in a region where the heating element temperature detecting unit is disposed is reduced. A plurality of the predetermined values are set, and the energization ratio to the two resistance heating elements is controlled based on the difference between the temperatures detected by the two heating body temperature detection means,
The fixing device according to claim 12, wherein the energization ratio corresponding to the predetermined value increases as the predetermined value increases. A heat-resistant film-like member that is conveyed while being pressed against the heating body fixedly supported by the support; and
A pressure member for closely attaching the recording material to the heating body via the heat-resistant film-like member;
With
14. The fixing according to claim 7, wherein an unfixed image is fixed to the recording material by applying heat of the heating body to the recording material through the heat-resistant film-like member. apparatus. An image forming apparatus comprising the fixing device according to claim 7.

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