JP2005209493A - Heating device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the margin of temperatures for good fixability and breaking temperatures of a fixing device by using a heater with high thermal efficiency in the state that the quantity of heating element paste on the heater is efficiently reduced, and by decreasing the temperature difference between a paper feeding area and a paper non-feeding area in the longitudinal direction of the fixing device, and to reduce the cost of a heating body. <P>SOLUTION: In the heating body used for a heat pressure type fixing device, the heating body has a plurality of conductors vertically extending against the introducing direction of a heated material in the introducing direction, resistors are formed between the conductors, and the resistors are thinned out. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, an elastic member is pressed against a heating member having a heating body to form a nip, the heated material introduced into the nip portion is sandwiched and conveyed, and the heating member applies heat energy to the heated material. And an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus provided as an image heating apparatus for heating and fixing an unfixed image formed and supported on a recording material as a material to be heated. It is about.

  An example will be described in which a conventional heating device is provided in an image forming apparatus such as a copying machine or a printer and is applied as an image heating device (fixing device) that heats and fixes a toner image on a recording material.

  In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, printing paper, electrophotographic process, electrostatic recording process, magnetic recording process, etc. is used. As a fixing device that heats and fixes an unfixed image (toner image) of image information formed and supported on a recording sheet by a transfer method or a direct method as a permanently fixed image on a recording material surface, a heat roller type heating device is widely used. It was used.

  In recent years, a film heating type heating apparatus has been put into practical use from the viewpoint of quick start and energy saving. For example, Japanese Patent Application Laid-Open No. 63-313182, Japanese Patent Application Laid-Open No. 2-157878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980 have proposed such a heating apparatus of the film heating method.

  As shown in FIG. 6, this film heating type heating apparatus is generally in pressure contact with a film (rotary body) 12 including a ceramic heater (hereinafter also referred to as a heater or a heating body) 13 as a heating body. A pressure roller 18 as another rotating body is supported by a support member (not shown) 11 (hereinafter referred to as a stay), and both the rotating bodies 12 and 18 are pressed by a pressing means (not shown) to form a pressure nip portion N. It is formed. The heater 13 forms a heating element 15 (also referred to as a resistor pattern) on a heat-resistant base material 14 (hereinafter referred to as a heater substrate) by film thickness printing, and the heater slide corresponding to the pressure nip portion N is formed. On the surface of the moving member, a sliding member having a pressure resistance, a heat resistance, and a low friction property such as a glass coat layer 16 is disposed.

  Further, FIG. 7 shows the arrangement of the heating elements 15 in a plan view. As shown in FIG. 7A, the heating element 15 is reciprocated with an equivalent resistance value with respect to the heater substrate 14. Alternatively, as shown in FIG. 7B, the forward path may be formed by the heating element 15 and the return path may be set by the conductor 21. Reference numeral 23 denotes an electrode.

  That is, a heat-resistant film 12 (also referred to as a fixing film, a fixing belt, or a film) is sandwiched between a heater 13 and a pressure roller 18 as a pressure member, and a pressure nip portion N (pressure nip portion, fixing nip portion). A recording material on which an unfixed toner image to be image-fixed is formed and carried between the film 12 and the pressure roller 18 in the pressure nip portion N, and is nipped and conveyed together with the film 12 As a result, the heat of the heater 13 is applied to the recording material through the film 12 at the pressure nip N, and is fixed to the surface of the unfixed toner image recording material by the pressure of the pressure nip N. .

  The heating device applied as the fixing device can be used as a device for improving the surface properties such as gloss by heating a recording material carrying an image, or a device for hypothetical dressing.

  This film heating type heating apparatus can be configured as an on-demand type apparatus using a ceramic heater and a member having a low heat capacity as a fixing film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. It is only necessary to generate heat at a predetermined fixing temperature, the waiting time from power-on of the image forming apparatus to an image forming executable state is short (quick start property), and power consumption during standby can be significantly reduced. There are advantages such as (power saving).

In a film heating type heating apparatus, a cylindrical or endless fixing film as a rotating body is driven by a film guide member (film support member) that guides the inner peripheral surface of the fixing film and a pressure roller. The driven fixing film is driven by rotating the pressure roller (pressure roller driving method), and conversely, the pressure roller is driven and rotated by driving an endless fixing film stretched between the driving roller and the tension roller. Method (fixing film driving method).
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980

  However, in recent years, image forming apparatuses such as copying machines and printers are required to have various problems such as increased printing speed, energy saving, quick startup, and downsizing. As the speed of each part increases, the fixing temperature rises, and in order to realize a quick start, the thermal response of the heater is improved and the heat capacity is reduced. As a result, when the paper is passed through, the heat of the fixing device is relatively taken away by the paper, the area where the paper is in the fixing nip (paper passing area), and the area where the paper is not taken away by heat (non-passing). Therefore, when a relatively small paper (small size paper) is passed with respect to the longitudinal width of the fixing device, the temperature difference increases in the longitudinal direction of the fixing device. . This indicates that the margin between the temperature at which the fixability of the paper can be secured and the breakdown temperature of the fixing device is small. Currently, in order to reduce this temperature difference, relatively large paper (full size) is used. In many cases, when passing relatively small paper, the printing speed is reduced and heat relaxation time is earned compared to passing paper. In this case, useless heat is generated, so that the in-machine temperature of the image forming apparatus rises, causing thermal damage to each part. As a result, it is difficult to reduce the size.

  In recent years, there has been a demand for cost reduction. Conventionally, costs have been reduced by downsizing the heater, but the substrate width has been reduced to several millimeters, and the number of wafers to be picked up further has increased. The situation is not so much affected by cost reduction.

  The present invention has been made to solve the conventional problems as described above, and in a state where the cost is reduced, the temperature difference between the sheet passing state and the non-sheet passing state is determined by the heating value of each heater. The purpose of this is to secure a margin between the fixing property and the fixing device breaking temperature, and to increase the printing speed to the same level as the full size even when passing small-size paper. Furthermore, it aims at saving energy and reducing the size by eliminating wasted heat.

1 A heating device that presses an elastic member to a heating member having a heating body to form a nip, sandwiches and conveys the material to be heated introduced into the nip portion, and applies thermal energy of the heating body to the material to be heated, In the heating device, the heating body has a plurality of conductors extending in a direction perpendicular to the introduction direction of the material to be heated in the introduction direction, and a resistor is formed between the conductors.
The heating device, wherein the resistor is formed between the continuous conductors, and the resistor is thinned out.

  2. The image forming apparatus according to 1, wherein (resistor region) / (resistor region)> 66% or more in the resistor region.

  3. The image forming apparatus according to 1, wherein the thinning-out of the resistor includes at least a resistor with respect to an arbitrary introduction direction in which the resistor is present.

  4 The heating device according to any one of 1 and 3, wherein the thinning is formed obliquely.

  5. The image forming apparatus according to claim 3, wherein (resistor region) / (resistor region)> 30% or more in the resistor-existing region.

  6. Image forming means for forming and carrying an unfixed image on a recording material; and fixing means for heating and fixing an unfixed image formed and supported on the recording material on the recording material, wherein the fixing means 6. The image forming apparatus according to any one of 1 to 5, wherein the image forming apparatus is the heat fixing apparatus according to any one of 5.

  At least two conductors are formed in a direction perpendicular to the heater substrate transport direction, and a heating element is formed therebetween. With this configuration, even when the temperature distribution changes between the paper passing area and the non-paper passing area when a small size is passed, the resistance rises where the temperature rises due to the temperature characteristics of the resistance of the heating element. As a result, the amount of heat generated is suppressed.

  Further, a wide heating element area can be formed with a small heating element area by disposing the heating element in the heater substrate in a thinned state. At that time, if (resistor region) / (resistor existence region)> 66% or more, it is possible to reduce non-uniformity in fixing property due to temperature non-uniformity including the width direction of the heater.

  In addition, since a heating element is always provided with respect to the sheet passing direction of the heater, uneven temperature in the longitudinal direction including the width direction of the heater can be reduced, so that the fixing property can be stably secured.

  Further, by thinning out diagonally, it is possible to further reduce temperature unevenness in the longitudinal direction including the width direction of the heater.

  Further, by setting (resistor area) / (resistor existence area)> 30% or more, it is possible to reduce unevenness in fixing property due to temperature unevenness including the width direction of the heater.

  As described above, according to the present invention, it is possible to obtain a large heat generation area with a small heat generation area by efficiently thinning out the heat generation area in the heater substrate, thereby reducing the heat generation efficiency at low cost. A high heater can be formed. In addition, the temperature difference between the paper-passing area and the non-paper-passing area in the nip longitudinal direction can suppress the amount of heat generated by each heater, ensuring a margin between the fixability and the fixing device breakdown temperature. Even when small-size paper is passed, the print speed can be increased to the same level as the full size. Furthermore, it is possible to save wasteful heat, save energy and make it more compact.

(Example 1)
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is a copying machine or printer using a transfer type electrophotographic process.

  Reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as a latent image carrier that is rotationally driven in a clockwise direction indicated by an arrow at a predetermined process speed. An image forming apparatus main motor M1 drives the photosensitive drum 1 and the like. Reference numeral 103 denotes a controller of the motor M1, which is controlled by the CPU 100. The photosensitive drum 1 has an outer diameter of about 24 mm, and is subjected to a primary charging process uniformly with a predetermined polarity and potential by a primary charging means (a charging roller in this example) 2 during its rotation. The charging surface is exposed to light image L by an exposure apparatus (not shown) (slit imaging exposure means for a document image, laser beam scanning exposure means, etc.) to form an electrostatic latent image of desired image information. . Then, the latent image is visualized as a toner image by the developing means 3. The toner image is fed at a predetermined timing from a sheet feeding unit (not shown) to the photosensitive drum 1 and a transfer unit T (hereinafter referred to as a transfer nip) which is a pressure nip between the transfer roller 4 as a transfer unit. The recording material P is sequentially transferred to the recording material P. The transfer roller 4 is controlled at a constant voltage by a power source 7 and a control circuit (not shown). The recording material P to which the toner image has been transferred at the transfer portion T is separated from the surface of the photosensitive drum 1 and is conveyed to an image heating and fixing device 8 which is a heating device described later, and undergoes a toner image heating and fixing process. It is output as a formed product (copy, print). The developing means and the transfer roller are supplied with a bias by a power source (not shown), and the timing of the supply is controlled based on ON / OFF signals of a sensor 6 (hereinafter referred to as a TOP sensor). In this embodiment, a photo interrupter is used as the TOP sensor. The surface of the photosensitive drum 1 after the transfer of the toner image onto the recording material P is subjected to a removal process of residual deposits such as transfer residual toner by the cleaning means 5 and is repeatedly used for image formation.

(2) Fixing device 8
The fixing device 8 of this example is a pressure member driving type / tensionless type film heating type heating device (Japanese Patent Application Laid-Open Nos. 4-44075 to 44083, Japanese Patent Application Laid-Open Nos. 4-20480 to 204484, etc.). Reference numeral 11 denotes a horizontally long stay made of a heat resistant resin, which serves as an inner surface guide member of the following endless heat resistant film (fixing film) 12. An endless heat-resistant film 12 is externally fitted to the stay 11 including a heater 13 as a heating body. The inner peripheral length of the endless heat-resistant film 12 and the outer peripheral length of the stay 11 including the heater 13 are larger than the film 12 by, for example, about 3 mm. The length fits loosely on the loose. The film 12 has a total thickness of about 40-100 μm to reduce heat capacity and improve quick start performance, and has PI, PTFE, PFA, FEP with heat resistance, releasability, strength, durability, etc. A composite layer film in which PTFE, PFA, FEP, etc. are coated on the outer peripheral surface of polyimide, polyamideimide, PEEK, PES, PPS or the like can be used. In this embodiment, a coating layer in which a conductive agent is added to a fluororesin such as PTFE / PFA is provided on the outer peripheral surface of the polyimide film, but this is not particularly limited. An elementary tube made of metal or the like may be used. The heater 13 as a heating body is formed of an electric resistance material (for example, Ag / Pd (silver palladium)) along the longitudinal direction at the substantially central portion of the surface of the heater substrate 14 made of alumina, aluminum nitride or the like, which is a high thermal conductivity material. A heating element 15 is applied to a thickness of about several tens of μm by screen printing or the like, and a protective layer 16 is coated thereon with glass, fluorine resin, or the like. Reference numeral 18 denotes a film pressure roller as a rotating body that drives the film 12 by forming a fixing portion N as a pressure nip with the film 12 sandwiched between the heater 13 and a core shaft 19 made of aluminum, iron, stainless steel, or the like. And a roller portion 20 having a wall thickness of 3 mm and an outer diameter of 20 mm, which is made of a heat-resistant rubber elastic body having good releasability, such as silicon rubber, which is sheathed on the shaft. Further, a coating layer in which a fluororesin is dispersed is provided on the surface for reasons of transportability of the recording material P, the fixing film 12, and prevention of toner contamination. The end of the metal core 19 is driven to rotate in the counterclockwise direction indicated by the arrow by being driven by the fixing device driving motor M2, and the endless heat-resistant film 12 is heated on the inner surface by the rotational driving of the pressure roller 18. It is driven to rotate in the clockwise direction indicated by the arrow while closely sliding on the surface of 13. When the endless heat-resistant film 12 is not driven, the remaining part of the heat-resisting film 12 except for the part sandwiched between the press-contact nip N between the heater 13 and the pressure roller 18 is tension-free. When the pressure roller 18 is driven to rotate, a moving force is applied to the film 12 by the frictional force with the rotary pressure roller 18 at the nip portion N, and the film 12 has the same inner speed as the rotation peripheral speed of the pressure roller 18. Is driven to rotate clockwise while sliding on the heater 13 surface (= protective layer 16 surface). At the time of driving the film, tension is applied to the film only at the nip portion N and upstream of the nip portion N in the film moving direction and between the film inner surface guide portion near the nip portion and the nip portion.

  Thus, by driving the film with sufficient margin, the shift movement force along the longitudinal direction of the film in the rotation process of the film is reduced to simplify the shift movement control means of the film, and the drive torque is also reduced. Thus, the apparatus can be simplified, downsized, and cost can be reduced.

  Thus, in the state where the film driving and the heating element layer 15 of the heater 13 are energized, the recording material P carrying the unfixed toner image is the rotating film 12 in the nip portion N as the fixing portion. When the recording material P is introduced between the rotary pressure roller 18 and the image bearing surface upward, the recording material P passes through the nip portion N together with the film 12 and is in contact with the inner surface of the film at the nip portion N. 13 is applied to the recording material P via the film 12, and the toner image is thermally fixed by the applied pressure at the nip portion N.

  In the heater 13, voltage application (power supply) is applied between the longitudinal ends of the heating element layer 15, so that the heating element layer 15 generates heat, the substrate 14 is heated, and the entire heater 13, which has a low heat capacity, rises rapidly and rapidly. Raise the temperature. For the temperature control of the heater 13, the output of the thermistor 17 provided on the heater 13 is A / D converted and taken into the CPU 100, and the AC voltage applied to the heating element layer 15 of the heater 13 by the triac 101 based on the information is phase-shifted.・ This is done by controlling the heater energizing power by wave number control. S is an AC power source.

  In order to ensure stable fixing performance, the thermistor 17 always detects the temperature of the recording material passing portion near the recording material conveyance reference portion of the heater 13, and the detected temperature of the thermistor 17 is set to a predetermined value. By controlling the energization so that the heater 13 is heated when the temperature is lower than the temperature, and the heater 13 is lowered when the temperature is higher than the temperature, the heater 13 is adjusted to a constant temperature during fixing.

(heater)
2A and 2B are enlarged views of the heater 13 in the heating apparatus of the present embodiment. 13 is an electrically conductive material (conductor) such as Ag or Ag / Pt, for example, about the heater substrate width direction of about 10 mm along the length of about 220 mm in the substantially central portion of the surface of the heater substrate 14. A pattern having a width of about 1 mm and a thickness of about several tens of μm is applied to the surface by screen printing or the like. 15 is an electric resistance material (heating element) having a PTC characteristic such as Ag / Pd (silver palladium), for example, which is thinned vertically in the sheet passing direction over about 7 mm between the two conductors 21. The pattern is applied to a thickness of about several tens of μm by screen printing or the like. The thinning is performed by 0.5 mm with respect to the heater substrate longitudinal direction. The heating element is formed with a length of 1.0 mm in the heater substrate longitudinal direction. Reference numeral 22 denotes a through hole in the heater substrate 14. A conductor is also formed in the through hole 22, a conduction path is provided on the back surface of the heater substrate, and the other electrode portion 23 is connected. By collecting the electrodes on one side, the connector shape to the electrode portion 23 can be simplified, and the heating element 15 can be efficiently arranged in the heater substrate 14. However, even if the through hole 22 is not provided, another conductive path may be provided on the surface of the substrate and connected to the electrode, and the same effect can be obtained even if the electrode is provided on both sides. Including the above, the pattern described in the present invention is hereinafter referred to as a “sheet feeding direction energization pattern” for the sake of simplicity.

  Next, the energization direction of the heater will be described.

  In the configuration in which the conventional heating element 15 is reciprocated with respect to the length of the heater substrate 14, when small-size paper is passed, the heat of the paper passing portion is relatively lowered due to heat being taken away by the paper, but the longitudinal non-passage is not achieved. The temperature of the paper section tends to rise because heat is not taken away. This is because the heating element used generally has PTC characteristics, and thus the resistance increases as heat is generated. However, in the present embodiment, even if a heating element having the same PTC characteristic is used, a current flow is formed not only in the longitudinal direction but also in the sheet passing direction with respect to the heater substrate 14, so that the non-sheet passing portion or the like In the region where the temperature rises, the current to the heating element 15 becomes difficult to flow, and the current flows through the conductor to the heating element 15 in the paper passing portion where the temperature is relatively low. For this reason, it is difficult for the temperature to rise at the non-sheet passing portion, and the temperature tends to rise at the non-sheet passing portion. In this embodiment, the volume resistance ratio between the conductor and the heating element is about 1000 times or more, and the resistance relationship at points A, B, and C is (between B-A) / (between C-A). ) Ratio is set to about 90%. This is because the temperature difference between the longitudinal end portion and the central portion of the heating element can be reduced, and a uniform heat generation distribution can be obtained. The resistance ratio (between B-A) / (between C-A) is about 90%, but if it is 90% or more, a better tendency is obtained.

  In order to obtain this resistance ratio, in the heater substrate configuration of the present embodiment, the volume resistance of the heating element 15 and the conductor 21 is adjusted. However, the heater substrate configuration is changed, and the width, thickness, and length of the heating element and the conductor are changed. Even if it is realized by a pattern such as the same, the same effect can be obtained. Further, as shown in FIG. 4, the conductor is divided into a plurality in the longitudinal direction, and adjacent conductor portions of the paper passing direction energization pattern are alternately connected in series. Even if the resistance ratio is satisfied, the same effect can be obtained.

  In the present embodiment, the description has been made centering on the configuration of the heater only with the sheet-passing direction energization pattern, but the same effect can be obtained by combining this pattern with a pattern in which the heating element is reciprocated in the heater longitudinal direction.

  Next, the conventional heating element reciprocating pattern is compared with the heating direction energization pattern of the heating element of this embodiment.

  The heating element reciprocating pattern used in the conventional example is the one shown in FIG. The heater substrate 14 has a width of about 10 mm and a longitudinal direction of 220 mm. The electrodes are arranged on one side with respect to the heater substrate 14, and what forms the electrodes is a conductor, and a heating element 15 having a width of about 1 mm is reciprocally arranged at the tip of the conductor. The heating element 15 is formed with a thickness of several tens of μm, and the conductor 21 and the heating element 15 are substantially equal in thickness.

  Further, as Comparative Examples 1 and 2, the results of the thinning ratios in the configuration of Example 1 are listed. Comparative Example 1 has a thinning width of about 2.0 mm with respect to the heater length and a heating element width of about 1.0 mm and a heating element ratio of about 33%. Comparative Example 2 has a thinning width of about 1.0 mm with respect to the heater length and a heating element width. As a comparison, when the heater is installed in the fixing device, the heating element ratio is about 1.0% and the heating element ratio is about 50%. The surface temperature of the pressure roller with respect to the paper part was compared with the non-uniformity of fixing property when the HT pattern was passed as a fixing sample (the worst and minimum difference in density reduction rate). The physical quantity of fixability in this example is a density reduction rate, which is a density reduction rate after rubbing with respect to the density before the HT pattern is rubbed.

  A condition for measuring the pressure roller surface temperature is a temperature difference when ten postcards are continuously passed in an environment of a room temperature of 23 degrees and a humidity of 50%. The surface temperature of the pressure roller was measured by contacting a felt formed of heat-resistant fibers with the pressure roller, placing a thermocouple between the pressure roller and the felt, and measuring the value. As the heater control, a thermistor is arranged on the back surface of the heater in the sheet passing area to control the temperature. Moreover, it set so that electric power might become equal in each heater, and it was set as the same temperature control.

  Further, the fixing unevenness measurement conditions are those when 10 full-size papers are passed in an environment of a room temperature of 15 degrees and a humidity of 10%. The paper type used is the LTR size of NeenahBond 60g paper. For each sheet, the fixability of the best part and the worst part was calculated, and the difference was defined as the unevenness of fixability. In the table below, the largest value among the 10 sheets was determined as the unevenness of fixability.

  Table 1 below shows the results of the comparison.

  In the configuration of the conventional example, when a small size paper such as a postcard is passed, the paper passing part is 230 degrees in the non-paper passing part compared with 130 degrees, and the ratio is about 177%, and the non-paper passing part is In contrast to the fact that the temperature was raised, in the configuration of this example, it can be seen that when the sheet passing portion is 140 degrees, the non-sheet passing portion is 180 degrees, and the ratio is reduced to about 129%. In the present embodiment, the temperature difference is 100 degrees in the prior art and 40 degrees in the present embodiment, and a margin increase of 60 degrees is achieved with respect to the temperature difference between the sheet passing portion and the non-sheet passing portion in the heater longitudinal direction. It has been. In Comparative Example 1 and Comparative Example 2, although the temperature difference between the paper passing portion and the non-paper passing portion is substantially the same as in the present embodiment, the fixing unevenness is worse than that in the conventional example and Embodiment 1. This is because there are places where the heating element area is insufficient and the temperature is locally lowered with respect to the length of the heater. The threshold value for fixing unevenness defined in this example was about 15%. If it is larger than this, it is impossible to achieve both the offset due to the fixing temperature being too high and the fixing property.

  With the configuration of the present embodiment described above, it is possible to reduce the temperature difference between the sheet passing portion and the non-sheet passing portion in the longitudinal direction of the fixing device when a small size or the like is passed through the fixing device. The margin between the fixing temperature for fixing the size and the breakdown temperature of the fixing device increases. As a result, it is possible to increase the printing speed with a relatively small size paper compared to the longitudinal size of the fixing device at present. Further, by thinning out and efficiently disposing the heating element on the heater, it is possible to produce the above effects using a high-efficiency and low-cost heater.

  Further, in the present embodiment, an example of a film driving type heat and pressure fixing device has been described, but a similar configuration may be adopted in other fixing devices. Although the heater is placed on the flat substrate, the same effect can be seen in the configuration in which the heater is provided in the film portion in this embodiment.

  Further, in this embodiment, the heating element surface is set on the film side with respect to the heater substrate, but the same effect can be obtained even on the back surface.

(Example 2)
In the first embodiment, the heating element is thinned vertically in the sheet passing direction to reduce the amount of the heating element. However, in this embodiment, a configuration in which the heating element can be further thinned out is proposed. FIG. 5 shows the heater of this embodiment. The configuration of the second embodiment is almost the same as that of the first embodiment. However, in the second embodiment, the heating element region is approximately the same in each sheet passing direction in the region where the heating element exists. . It is characterized by thinning out at an angle.
The thinning out in FIG. 5 is performed in an oblique direction with respect to the paper passing area. The width of each heating element is 1.0 mm in the longitudinal direction, and the heating element width is also 1.0 mm.

  Next, the effect of the present embodiment will be described.

  In addition, as Comparative Example 3, the results of the thinning ratios in the configuration of Example 2 are listed. Comparative Example 3 has a thinning width of about 4.0 mm with respect to the heater length and a heating element width of about 1.0 mm and a heating element ratio of about 20%. Comparative Example 4 has a thinning width of about 2.3 mm with respect to the heater length and a heating element width. The heating element ratio is about 1.0% at about 1.0 mm.

  As a comparison, when the heater is incorporated into the fixing device, the surface temperature of the pressure roller between the non-sheet passing portion and the sheet passing portion with respect to the length of the heater when the paper is passed through the fixing nip, and the fixing property As a sample, the fixing unevenness (the worst difference and the smallest difference in density reduction rate) when the HT pattern was passed was compared.

  The condition is the temperature difference when ten consecutive postcards are passed in an environment of room temperature 23 degrees and humidity 50%. The surface temperature of the pressure roller was measured by contacting a felt formed of heat-resistant fibers with the pressure roller, placing a thermocouple between the pressure roller and the felt, and measuring the value. As the heater control, a thermistor is arranged on the back surface of the heater in the sheet passing area to control the temperature. Moreover, it set so that electric power might become equal in each heater, and it was set as the same temperature control.

  As a comparison, the surface temperatures of the pressure rollers of the non-sheet passing portion and the sheet passing portion with respect to the length of the heater when the paper was passed through the fixing nip when the heater was incorporated in the fixing device were compared.

  The measurement conditions are the same as in Example 1.

  Table 2 below shows the results of the comparison.

  First, the temperature difference between the paper passing portion and the non-paper passing portion when passing small-size paper is about 40 degrees in any item. Good and almost equivalent.

  Next, regarding the fixing unevenness, it can be confirmed that the present embodiment has an effect equal to or greater than that of the first embodiment. The fixing unevenness equivalent to or higher than that of the configuration 1 of the embodiment can be achieved with the heating element amount of 50% as the configuration of the embodiment. In Comparative Example 3, although the temperature difference between the non-sheet passing portion and the sheet passing portion was substantially the same, the fixing unevenness in the heater length was 25%, which exceeded the threshold value of 15%. This is because unevenness in temperature occurs on the heater surface side with respect to the heater length as in the first embodiment, and thus uneven fixing occurs. Further, Comparative Example 4 was OK in practical use because it was the same as Example 1 and the fixing unevenness was within 15% defined in this Example.

  With the configuration of the present embodiment described above, it is possible to reduce the temperature difference between the sheet passing portion and the non-sheet passing portion in the longitudinal direction of the fixing device when a small size or the like is passed through the fixing device. The margin between the size fixability securing temperature and the fuser destruction temperature increases. As a result, it is possible to increase the printing speed with a relatively small size paper compared to the longitudinal size of the fixing device at present. Further, by thinning out and efficiently disposing the heating element on the heater, it is possible to produce the above effects using a high-efficiency and low-cost heater.

  Further, in the present embodiment, an example of a film driving type heat and pressure fixing device has been described, but a similar configuration may be adopted in other fixing devices. Although the heater is placed on the flat substrate, the same effect can be seen in the configuration in which the heater is provided in the film portion in this embodiment.

  Further, in the present embodiment, thinning is performed obliquely and continuously across the entire width direction, but the same effect can be obtained by providing a plurality of thinned portions by dividing in the width direction. Moreover, you may thin out like a checkered pattern.

  Further, in this embodiment, the heating element surface is set on the film side with respect to the heater substrate, but the same effect can be obtained even on the back surface.

FIG. 2 is a diagram illustrating a schematic diagram of an image forming apparatus according to the first embodiment. 2 is a diagram illustrating a heating body (heater) in the invention of Example 1. FIG. 3 is a diagram illustrating a heating body (heater) used as a comparative example of the invention of Example 1. FIG. 3 is a diagram illustrating a heating body (heater) in the invention of Example 1. FIG. It is a figure showing the heating body (heater) in invention of Example 2. FIG. It is a figure showing the fixing device structure of a prior art example. It is a figure showing the heater structure of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Developing means 4 Transfer roller 8 Heating and fixing device 13 Heater 14 Heater substrate 15 Heating element 16 Protective layer 18 Pressure roller 21 Conductor 22 Through hole 23 Electrode

Claims (6)

A heating device that presses an elastic member to a heating member having a heating body to form a nip, sandwiches and conveys the material to be heated introduced into the nip portion, and applies the thermal energy of the heating body to the material to be heated, In the heating body, the heating device has a plurality of conductors extending in a direction perpendicular to the introduction direction of the material to be heated in the introduction direction, and a resistor is formed between the conductors.
The heating device, wherein the resistor is formed between the continuous conductors, and the resistor is thinned out.   2. The image forming apparatus according to claim 1, wherein (resistor region) / (resistor region)> 67% or more in the resistor existence region.   The image forming apparatus according to claim 1, wherein the thinning of the resistor includes at least a resistor in an arbitrary introduction direction of the resistor existence region.   The heating apparatus according to claim 1, wherein the thinning is formed obliquely.   5. The image forming apparatus according to claim 3, wherein (resistor region) / (resistor region)> 30% or more in the resistor presence region.   6. Image forming means for forming and supporting an unfixed image on a recording material; and fixing means for heating and fixing an unfixed image formed and supported on the recording material to the recording material, wherein the fixing means is defined in claims 1 to 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is a heat fixing apparatus according to claim 1.

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