JP7491069B2 - Heating device and image forming apparatus - Google Patents

Description

The present invention relates to a heating device and an image forming device.

In image forming devices such as copiers and printers, known heating devices for heating recording media such as paper include fixing devices that fix images on paper using heat, and drying devices that dry ink on paper.

For example, in fixing devices, in response to demands for energy saving and high speed, rotating members such as endless belts and films that have a smaller heat capacity than rollers are beginning to be used.

Generally, in fixing devices that use rotating members such as belts and films, the rotating members tend to experience localized temperature increases in non-paper passing areas where paper does not pass. For this reason, Patent Document 1 (JP 2018-169467 A) proposes a configuration in which a heat transfer assistant member made of a material with high thermal conductivity such as copper or aluminum is placed inside the rotating member (fixing belt) to suppress localized temperature increases in the rotating member. This heat transfer assistant member is in contact with the inner circumferential surface of the rotating member along its length, so that when the rotating member experiences a localized temperature increase, the heat in the high-temperature portion moves longitudinally through the heat transfer assistant member and disperses. This suppresses localized temperature increases in the rotating member.

The likelihood of temperature rise in non-paper passing areas and the extent of the temperature rise vary depending on the performance of the heating device and the image forming device in which it is installed. That is, in models with high printing speeds, the heater is turned on more frequently per unit time, making it easier for temperature rise to occur in non-paper passing areas and the extent of the temperature rise more noticeable. For this reason, the performance of the heat transfer auxiliary member required to suppress the temperature rise also differs from model to model.

However, when using heat transfer assisting parts of different types (performance) for each model, there is an issue that when trying to check the installation status and type of the heat transfer assisting parts after installation, it is difficult to check the heat transfer assisting parts from the outside by visual inspection, etc., because the heat transfer assisting parts are located inside the rotating parts.

In order to solve the above-mentioned problems, the present invention provides a heating device comprising a first rotating member, a second rotating member that contacts the outer peripheral surface of the first rotating member to form a nip portion, a heating source that heats the first rotating member, a heat transfer auxiliary member that directly or indirectly contacts the inner peripheral surface of the first rotating member at the position of the nip portion, and a metal sidewall member, wherein a portion of the heat transfer auxiliary member is arranged on the outside of the first rotating member, and a cross-sectional area of the heat transfer auxiliary member in a direction intersecting the longitudinal direction is smaller in the portion arranged on the outside of the first rotating member than in the portion arranged on the inside of the first rotating member, the sidewall member has a through hole, and the portion of the heat transfer auxiliary member arranged on the outside of the first rotating member is inserted into the through hole and is arranged so as not to contact the sidewall member without any other member between it and the surface that forms the through hole .

The present invention makes it easier to check the heat transfer assistance member.

1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a schematic configuration diagram of a fixing device according to the present embodiment. FIG. 3 is a diagram of the fixing device according to the present embodiment as viewed from above in FIG. 2 . FIG. 2 is a perspective view of a heat transfer assistance member according to the present embodiment. FIG. 4 is a cross-sectional view showing a state in which the heat transfer assistance member is assembled in the fixing device. 6 is a cross-sectional view of the fixing device shown in FIG. 5 as viewed from above. 5A to 5C are schematic diagrams showing temperature distributions of a fixing belt when heat transfer assistance members of different shapes are used. FIG. 13 is a perspective view of a heat transfer assistance member according to a conventional example. FIG. 13 is a perspective view of a heat transfer assistance member according to a comparative example.

The present invention will be described below with reference to the attached drawings. In each drawing for explaining the present invention, components such as parts and components having the same function or shape are given the same reference numerals as far as possible to distinguish them, and the description will be omitted after the first description.

Figure 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention.

The image forming device 100 shown in FIG. 1 includes an image forming unit 200, a transfer unit 300, a fixing unit 400, a recording medium supply unit 500, and a recording medium discharge unit 600.

The image forming section 200 is provided with four imaging units 1Y, 1M, 1C, and 1Bk, and an exposure device 6. Each imaging unit 1Y, 1M, 1C, and 1Bk is configured to be detachable from the image forming apparatus main body. In addition, each imaging unit 1Y, 1M, 1C, and 1Bk has a basically similar configuration except that it contains developers of different colors, yellow, magenta, cyan, and black, which correspond to the color separation components of the color image. Specifically, each imaging unit 1Y, 1M, 1C, and 1Bk includes a photoconductor 2, which is an image carrier that carries an image on its surface, a charging roller 3, which is a charging means for charging the surface of the photoconductor 2, a developing device 4, which is a developing means for forming a toner image on the photoconductor 2, and a cleaning device 5, which is a cleaning means for cleaning the surface of the photoconductor 2. The exposure device 6 is a latent image forming means that exposes the charged surface of the photoconductor 2 based on image information to form an electrostatic latent image. In FIG. 1, only the photoconductor 2, charging roller 3, developing device 4, and cleaning device 5 of one imaging unit 1Bk are labeled with reference numerals, and the reference numerals of the other imaging units 1Y, 1M, and 1C are omitted.

The transfer unit 300 is provided with a transfer device 8 that transfers an image onto a recording medium, which is paper. The recording medium on which an image is formed (transferred) may be paper (including plain paper, thick paper, thin paper, coated paper, label paper, envelopes, etc.), or a resin sheet such as an OHP sheet. The transfer device 8 has an intermediate transfer belt 11, four primary transfer rollers 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is a transfer member that carries an image on its surface and transfers the image onto paper, and is composed of an endless belt member. Each primary transfer roller 12 contacts a different photoconductor 2 via the intermediate transfer belt 11. As a result, a primary transfer nip is formed between the intermediate transfer belt 11 and each photoconductor 2, where the intermediate transfer belt 11 and each photoconductor 2 contact each other. On the other hand, the secondary transfer roller 13 contacts one of the multiple rollers that stretch the intermediate transfer belt 11 via the intermediate transfer belt 11, and forms a secondary transfer nip between the intermediate transfer belt 11 and the secondary transfer roller 13.

The fixing section 400 is provided with a fixing device 9, which is a heating device that heats the paper and also fixes the image on the paper using heat.

The recording medium supply unit 500 is provided with a paper feed cassette 14 that stores paper P, and a paper feed roller 15 that feeds paper P from the paper feed cassette 14.

The recording medium ejection section 600 is provided with a pair of ejection rollers 17 that eject paper outside the image forming device, and an ejection tray 18 on which the paper ejected by the ejection rollers 17 is placed.

Next, the printing operation of the image forming device 100 according to this embodiment will be described with reference to FIG.

When an instruction to start the printing operation is given, the photoconductors 2 of each of the imaging units 1Y, 1M, 1C, and 1Bk and the intermediate transfer belt 11 start to rotate. In addition, the paper feed roller 15 rotates, causing paper P to be fed out of the paper feed cassette 14. The fed paper P comes into contact with a pair of timing rollers 16 and is temporarily stopped.

In each of the imaging units 1Y, 1M, 1C, and 1Bk, the surface of the photoconductor 2 is first charged to a uniform high potential by the charging roller 3. Next, the exposure device 6 exposes the surface (charged surface) of each photoconductor 2 based on the image information of the document read by the document reading device or the print image information instructed to be printed from the terminal. This reduces the potential of the exposed part and forms an electrostatic latent image on the surface of each photoconductor 2. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoconductor 2. When the toner image formed on each photoconductor 2 reaches the primary transfer nip (the position of the primary transfer roller 12) as each photoconductor 2 rotates, it is transferred to the rotating intermediate transfer belt 11 so that the toner images are overlapped one after another. Thus, a full-color toner image is formed on the intermediate transfer belt 11. After the toner image is transferred from the photoconductor 2 to the intermediate transfer belt 11, the toner and other foreign matter remaining on each photoconductor 2 is removed by the cleaning device 5, and the photoconductor 2 is prepared for the formation of the next electrostatic latent image.

The toner image transferred onto the intermediate transfer belt 11 is transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is transferred onto the paper P that has been transported by the timing roller 16. The paper P onto which the toner image has been transferred is then transported to the fixing device 9, which fixes the toner image onto the paper P. The paper P is then discharged onto the paper discharge tray 18 by the paper discharge rollers 17, completing the printing process.

The above description of the printing operation is for forming a full-color image, but it is also possible to use any one of the four imaging units to form a monochrome image, or to use two or three imaging units to form a two- or three-color image.

Figure 2 is a schematic diagram of the fixing device 9 according to this embodiment, and Figure 3 is a diagram of the fixing device 9 according to this embodiment as viewed from above in Figure 2. The configuration of the fixing device 9 according to this embodiment will be described below with reference to Figures 2 and 3.

As shown in FIG. 2, the fixing device 9 according to this embodiment includes a fixing belt 20 as a first rotating member, a pressure roller 21 as a second rotating member, a halogen heater 22 as a heat source, end heaters 27A and 27B as another heat source, a nip forming member 23, a reflecting member 24, a stay 25, a heat transfer auxiliary member 26, and temperature sensors 19A and 19B. As shown in FIG. 3, the fixing device 9 according to this embodiment includes a pair of belt holding members 28 that hold the fixing belt 20, and a pair of side plates 29 as side wall members.

The fixing belt 20 is a first rotating member and is a fixing member that is arranged on the unfixed image carrying surface side of the paper P and fixes the unfixed image on the paper P. The fixing belt 20 is composed of an endless belt member. The fixing belt 20 is rotatably held by a pair of belt holding members 28 that serve as rotating holding members inserted at both ends in the longitudinal direction Z (see FIG. 3). Each belt holding member 28 is formed, for example, in a flange shape, and is inserted inside the fixing belt 20 with a margin. Therefore, the fixing belt 20 is rotatably held by the pair of belt holding members 28 in a non-stretched state (no tension is applied to the belt, so-called free belt method). Each belt holding member 28 is attached and fixed to a pair of side plates 29.

The pressure roller 21 is a second rotating member and a pressure member that is pressed against the outer peripheral surface of the fixing belt 20. Specifically, the pressure roller 21 is composed of a core metal, an elastic layer made of foamed silicone rubber, silicone rubber, or fluororubber, etc., provided on the surface of the core metal, and a release layer made of PFA or PTFE, etc., provided on the surface of the elastic layer. The pressure roller 21 is pressed (pressed) against the fixing belt 20 by a biasing member such as a spring, and a nip portion N is formed between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is configured to be rotated by a drive source provided in the image forming apparatus body. When the pressure roller 21 is rotated, the drive force is transmitted to the fixing belt 20 at the nip portion N, causing the fixing belt 20 to rotate. As shown in FIG. 2, the paper P carrying the unfixed image is transported in the direction of the arrow Y in the figure and enters between the fixing belt 20 and the pressure roller 21 (nip portion N). The paper P is heated and pressurized by the rotating fixing belt 20 and pressure roller 21 as it is transported, and the unfixed image is fixed to the paper P.

In this embodiment, the pressure roller 21 is a solid roller, but it may be a hollow roller. In that case, a heater may be disposed inside the pressure roller 21. Also, if the pressure roller 21 does not have an elastic layer, the heat capacity is reduced, and the fixing performance is improved. However, on the other hand, when fixing unfixed toner, minute irregularities on the belt surface may be transferred to the image, causing uneven gloss in the solid part of the image. To prevent this, it is desirable for the pressure roller 21 to have an elastic layer with a thickness of 100 μm or more. By having an elastic layer with a thickness of 100 μm or more, minute irregularities can be absorbed by the elastic deformation of the elastic layer, and the occurrence of uneven gloss can be avoided. The elastic layer of the pressure roller 21 may be solid rubber, but if there is no heater inside the pressure roller 21, sponge rubber can also be used. Sponge rubber is more desirable than solid rubber in that it has higher insulation properties and is less likely to take away heat from the fixing belt 20.

The halogen heater 22 is a heat source that is disposed inside the fixing belt 20 and heats the inner peripheral surface of the fixing belt 20 by directly irradiating it with light (e.g., infrared light). As such a heat source, other radiant heat heaters such as carbon heaters and ceramic heaters may be used in addition to halogen heaters. It is also possible to use an electromagnetic induction heating type heat source. In this embodiment, two halogen heaters 22 are disposed inside the fixing belt 20, but the number of heat sources may be one or three or more.

The end heaters 27A and 27B are a pair of end heat sources that heat both longitudinal end sides of the fixing belt 20 at the nip portion N. The end heaters 27A and 27B are independently disposed at positions spaced apart from each other in the longitudinal direction of the fixing belt 20, and are integrally provided in the nip forming member 23.

The temperature sensors 19A and 19B are disposed opposite the outer peripheral surface of the fixing belt 20, and are temperature detection means for detecting the surface temperature of the fixing belt 20. The surface temperature of the fixing belt 20 is detected by the temperature sensors 19A and 19B, and the output of the halogen heater 22 and the end heaters 27A and 27B is controlled based on the detection results, so that the temperature of the fixing belt 20 is controlled to the desired temperature (fixing temperature). As the temperature sensors 19A and 19B, for example, known temperature sensors such as a thermopile, a thermostat, a thermistor, and an NC sensor can be applied. The temperature sensors 19A and 19B may be of a non-contact type disposed in a non-contact manner with respect to the fixing belt 20 as shown in FIG. 2, or may be of a contact type in contact with the fixing belt 20.

The nip forming member 23 is a member disposed inside the fixing belt 20 and forms a nip portion N between the fixing belt 20 and the pressure roller 21 by receiving a pressure from the pressure roller 21. The nip forming member 23 is in contact with the inner peripheral surface of the fixing belt 20 via the heat transfer auxiliary member 26. It is preferable to use a heat-resistant member having a heat resistance temperature of 200°C or more as the material of the nip forming member 23. Specifically, examples of the material of the nip forming member 23 include general heat-resistant resins such as polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), and polyetheretherketone (PEEK). By configuring the nip forming member 23 with such a heat-resistant member, it is possible to prevent the nip forming member 23 from being deformed by heat in the fixing temperature range, so that a stable state of the nip portion N can be ensured and the output image quality can be stabilized.

The stay 25 is a support member that contacts the side of the nip forming member 23 opposite to the pressure roller 21 side and supports the nip forming member 23. The heat transfer auxiliary member 26 is also supported by the stay 25 via the nip forming member 23. By supporting the nip forming member 23 and the heat transfer auxiliary member 26 by the stay 25, the deflection of the nip forming member 23 and the heat transfer auxiliary member 26 due to the pressure of the pressure roller 21, particularly the deflection across the longitudinal direction of the fixing belt 20, is suppressed, and a nip portion N of uniform width is formed. The stay 25 is attached to and supported by each belt holding member 28 at both ends in the longitudinal direction. The stay 25 may also be directly attached to each side plate 29. As a material for the stay 25, an iron-based metal material such as SUS or SECC is preferable in order to ensure rigidity.

The reflective member 24 is a member that reflects heat and light (e.g., infrared light) radiated from the halogen heater 22. The reflective member 24 reflects the heat and light from the halogen heater 22 toward the fixing belt 20, thereby efficiently heating the fixing belt. In addition, the reflective member 24 is disposed between the stay 25 and the halogen heater 22, and can also suppress heating of the stay 25 by the halogen heater 22. This reduces the wasteful consumption of thermal energy, and also contributes to energy conservation.

The function of the reflective member 24 may also be imparted to the stay 25. For example, the surface of the stay 25 facing the halogen heater 22 may be mirror-finished so that the stay 25 also functions as the reflective member 24. In this case, there is no need to provide a separate reflective member 24, which is advantageous for miniaturization and cost reduction.

The heat transfer assistant member 26 is a member that is interposed between the nip forming member 23 and the fixing belt 20, and transfers the heat of the fixing belt 20 mainly in its longitudinal direction, suppressing the variation in the surface temperature of the fixing belt 20. The heat transfer assistant member 26 is made of a highly heat-conductive material that has a higher thermal conductivity than the resin nip forming member 23. For example, copper, aluminum, or silver can be used as the material for the heat transfer assistant member 26. In this embodiment, the contact surface (opposing surface) of the heat transfer assistant member 26 that contacts (opposes) the inner peripheral surface of the fixing belt 20 is formed in a flat shape, but it may be concave or have other shapes. If the contact surface of the heat transfer assistant member 26 is concave, the nip portion N also becomes concave accordingly, improving the separation of the paper P from the fixing belt 20.

Since the heat transfer auxiliary member 26 is in contact with the inner peripheral surface of the fixing belt 20, when the fixing belt 20 rotates, the heat transfer auxiliary member 26 slides against the fixing belt 20. In order to reduce the frictional resistance between the heat transfer auxiliary member 26 and the fixing belt 20 at this time, the contact surface of the heat transfer auxiliary member 26 with the fixing belt 20 is coated (low-friction treatment) with, for example, diamond-like carbon, PTFE, molybdenum disulfide, graphite, etc. Furthermore, in order to reduce the frictional resistance, a lubricant is applied to the inner peripheral surface of the fixing belt 20. As the lubricant, a liquid lubricant containing any one of silicone oil, silicone grease whose base oil is silicone oil, fluorosilicone oil, fluorosilicone grease whose base oil is fluorosilicone oil, fluorine oil, or fluorine grease whose base oil is fluorine oil, or a combination of these, is preferable. The heat transfer assistance member 26 may be in direct contact with the inner circumferential surface of the fixing belt 20, not necessarily indirectly through a low-friction coating layer or lubricant.

However, in a fixing device using a fixing belt with a small heat capacity as described above, while heating efficiency and energy saving are improved compared to a configuration using a roller as a fixing member, there is a tendency for temperature rises to occur in non-paper passing areas where paper does not pass. In other words, when paper with a width smaller than the width of the heating area of the heater is continuously passed through, the heat of the fixing belt is not easily consumed in the non-paper passing areas where paper does not pass, so heat is stored and the temperature is likely to rise locally. However, in the fixing device 9 according to this embodiment, the heat transfer auxiliary member 26 with high thermal conductivity is continuously in contact with the inner surface of the fixing belt 20 in the longitudinal direction, so that the heat in the non-paper passing areas moves and disperses in the longitudinal direction via the heat transfer auxiliary member 26, and local temperature rises in the non-paper passing areas can be suppressed.

In this way, by using a heat transfer auxiliary member, it is possible to suppress temperature rise in non-paper passing areas, thereby increasing the productivity (number of sheets output per unit time) of continuous printing of small size paper. However, when a heat transfer auxiliary member is used, the heat transfer auxiliary member is more likely to remove heat from the fixing belt, which raises concerns that the warm-up time required to heat the fixing belt to a specified target temperature may be longer.

In addition, since the likelihood of temperature rise in non-paper passing areas and the degree of temperature rise vary depending on the productivity of the image forming device, it is preferable to use a heat transfer auxiliary member suitable for each model to achieve both suppression of temperature rise in non-paper passing areas and shorten the warm-up time. That is, in highly productive image forming devices, the heater is turned on at a high rate per unit time and the temperature rise in non-paper passing areas is also significant, so it is preferable to apply a heat transfer auxiliary member with high thermal conductivity and relatively large heat capacity. Conversely, in low-productivity image forming devices, the temperature rise in non-paper passing areas is not significant, so it is possible to shorten the warm-up time by using a heat transfer auxiliary member with small heat capacity.

However, if different types (performance) of heat transfer assistant members are used for each model, when attempting to check the installation state and type of the heat transfer assistant member after installation, there is a problem that it is difficult to check the heat transfer assistant member from the outside by visual inspection, etc., because the heat transfer assistant member is located on the inside of the fixing belt. Therefore, to improve such a problem, in the fixing device of this embodiment, the heat transfer assistant member is configured as follows.

Figure 4 is a perspective view of the heat transfer assistance member according to this embodiment.

As shown in FIG. 4, the heat transfer assistant member 26 according to this embodiment is composed of a plate-like member formed long in one direction. Here, the configuration of the heat transfer assistant member 26 will be described with the mutually orthogonal directions of arrow A, arrow B, and arrow C in FIG. 4 being the longitudinal direction A, width direction B, and thickness direction C of the heat transfer assistant member 26, respectively. Note that the longitudinal direction A corresponds to the longitudinal direction Z of the fixing belt 20 or the rotational axis direction of the pressure roller 21 shown in FIG. 3 when the heat transfer assistant member 26 is assembled in the fixing device, and the width direction B corresponds to the paper passing direction (recording medium passing direction) Y shown in FIG. 2.

The heat transfer assisting member 26 according to this embodiment has a main body 30 and a pair of protruding portions 31 provided to protrude from both ends of the main body 30 in the longitudinal direction A. The main body 30 also has a nip forming portion 32 that directly or indirectly contacts the inner peripheral surface of the fixing belt 20 to form a nip portion N (see FIG. 2), and a pair of bending portions 33 provided to bend from both ends of the nip forming portion 32 in the width direction B in the thickness direction C (the side opposite the pressure roller 21 side shown in FIG. 2).

Each protrusion 31 is formed with a smaller dimension in the width direction B than the nip forming portion 32, and is provided so as to extend from the nip forming portion 32 in the longitudinal direction A. In addition, each protrusion 31 is provided with an identification recess 34 for identifying the type of heat transfer assistance member 26.

Figure 5 is a cross-sectional view showing the heat transfer assistance member according to this embodiment assembled into the fixing device, and Figure 6 is a cross-sectional view of Figure 5 as seen from above.

5 and 6, when the heat transfer assistant member 26 is assembled to the fixing device 9, at least a part of each protrusion 31 is exposed to the outside from both ends 20a, 20b in the longitudinal direction Z of the fixing belt 20. That is, the total length L1 from the tip 31a of one protrusion 31 to the tip 31b of the other protrusion 31 in the heat transfer assistant member 26 is longer than the total length L2 from one end 20a to the other end 20b in the longitudinal direction Z of the fixing belt 20. Therefore, when the longitudinal center M1 of the heat transfer assistant member 26 is arranged to correspond to the longitudinal center M2 of the fixing belt 20, at least the tip 31a, 31b side part of each protrusion 31 is arranged in a state where it protrudes outward from both ends 20a, 20b in the longitudinal direction of the fixing belt 20. On the other hand, the main body 30 of the heat transfer assistant member 26 is arranged entirely inside the fixing belt 20.

If the side of the longitudinal center M2 of the fixing belt 20 relative to the belt holding member 28 and the side plate 29 is defined as the "inner side" and the opposite side as the "outer side", the overall length L1 of the heat transfer assistant member 26 is longer than the distance L3 between the outer side surfaces 28a, 28b of each belt holding member 28, and is also longer than the distance L4 between the outer side surfaces 29a, 29b of each side plate 29. Therefore, when the heat transfer assistant member 26 is assembled, at least the portions of the tips 31a, 31b of each protrusion 31 are arranged in a state where they are exposed outward relative to the outer side surfaces 28a, 28b of each belt holding member 28 and the outer side surfaces 29a, 29b of each side plate 29.

In this way, in the fixing device 9 according to the present embodiment, at least the tip 31a, 31b side of each protrusion 31 of the heat transfer auxiliary member 26 is arranged outside the fixing belt 20, the belt holding member 28, and the side plate 29, so that the identification recess 34 (see FIG. 6) provided on each protrusion 31 is exposed outside these. Therefore, even after the heat transfer auxiliary member 26 is assembled, the identification recess 34 can be easily visually confirmed. The identification recess 34 differs in position, shape, number, etc. for each type of heat transfer auxiliary member 26, and the type of heat transfer auxiliary member 26 can be identified by visually confirming the recess 34. This makes it possible to confirm whether the type of assembled heat transfer auxiliary member 26 and the assembly state (assembly direction and position) of the heat transfer auxiliary member 26 are appropriate, and it becomes possible to avoid a decrease in performance due to incorrect assembly. In addition, since it is sufficient for the protrusions 31 to be identifiable visually, instead of providing identification recesses 34, the heat transfer assistance members 26 may be identifiable by, for example, varying the color or glossiness (surface roughness) of the protrusions 31.

In this embodiment, the protrusion 31 of the heat transfer assistant member 26 is arranged so as to be exposed outward from the belt holding member 28 and the side plate 29, but as long as the heat transfer assistant member 26 can be seen through a cutout portion, for example, by cutting out a portion of the belt holding member 28 or the side plate 29, the heat transfer assistant member 26 does not necessarily have to be exposed outward from the belt holding member 28 or the side plate 29. In other words, it is sufficient that the heat transfer assistant member 26 is arranged in a state where it is exposed at least to the outside of the fixing belt 20.

In addition, for the purpose of improving the visibility of the heat transfer assistant member 26, the heat transfer assistant member 26 according to the present invention may have only one end in the longitudinal direction A protruding outward from at least the fixing belt 20. In addition, the heat transfer assistant member 26 may not be a single integrally molded member as in this embodiment, but may be made up of two or more divided members.

As described above, in the fixing device 9 according to this embodiment, the protrusions 31 of the heat transfer assistance member 26 are exposed to the outside, improving visibility and making it possible to check the type of heat transfer assistance member 26 and its installation state. However, on the other hand, since the protrusions 31 are provided to extend from the main body 30, heat is more likely to diffuse through the protrusions 31, which may cause a drop in temperature, especially at both longitudinal ends of the fixing belt 20.

Therefore, in the fixing device 9 according to the present embodiment, in order to reduce the diffusion of heat due to the provision of the protruding portion 31, the cross-sectional area of the heat transfer assistance member 26 in the direction intersecting the longitudinal direction A is made smaller in the protruding portion 31 arranged on the outside of the fixing belt 20 than in the main body portion 30 arranged on the inside of the fixing belt 20. Specifically, in the present embodiment, the width of the protruding portion 31 is made smaller than the width of the main body portion 30, so that the cross-sectional area of the protruding portion 31 is made smaller than the cross-sectional area of the main body portion 30. In this way, by reducing the cross-sectional area of the protruding portion 31 and reducing its heat capacity, the diffusion of heat due to the protruding portion 31 can be reduced, and the temperature drop at both ends of the longitudinal direction of the fixing belt 20 can be suppressed.

Figure 7 is a schematic diagram showing the temperature distribution of the fixing belt when heat transfer assistance members of different shapes are used.

In FIG. 7, the solid line indicates the temperature distribution when an embodiment of the present invention having the same structure as the example shown in FIG. 4 is used, the two-dot chain line indicates the temperature distribution when a conventional example shown in FIG. 8 is used, which does not have the protruding portion 31 of the example shown in FIG. 4 and only has the main body portion 30, and the dashed line indicates the temperature distribution when a comparative example shown in FIG. 9 is used, which does not have the protruding portion 31 of the example shown in FIG. 4 and has the main body portion 30 extended to the same length as the total length L1 shown in FIG. 4. In addition, in the horizontal axis shown in FIG. 7, the regions α and β correspond to the regions α and β of the heat transfer auxiliary member 26 shown in each of the examples in FIG. 4, FIG. 8, and FIG. In particular, the region γ in the region β indicates the region through which the maximum image formation region on the paper passes.

As shown in FIG. 7, in the comparative example (dotted line), by extending the main body 30, the heat of the fixing belt is more likely to diffuse to both ends in the longitudinal direction than in the embodiment of the present invention (solid line) or the conventional example (dotted line), and the temperature of the fixing belt at both ends of the maximum image forming area γ is lower than the target temperature T required for image fixing. In contrast, in the embodiment of the present invention (solid line), the temperature of the fixing belt is slightly lower at the ends of the maximum image forming area γ due to the presence of the protrusion 31 compared to the conventional example (dotted line), but the temperature drop can be suppressed compared to the comparative example. Therefore, in the embodiment of the present invention, the temperature T required for image fixing can be maintained throughout the entire maximum image forming area γ.

In this way, in the embodiment of the present invention, by providing the protrusion 31 and making the overall length longer than in the conventional example, visibility is improved, while by reducing the cross-sectional area of the lengthened portion (protrusion 31), heat diffusion to both ends of the fixing belt in the longitudinal direction can be reduced and a drop in temperature of the fixing belt can be suppressed. Therefore, according to the present invention, it is possible to achieve both improved visibility of the heat transfer assistance member and suppression of a drop in temperature of the fixing belt. Furthermore, by reducing the diffusion of heat to both ends of the fixing belt in the longitudinal direction, it is also possible to shorten the warm-up time when heating the fixing belt to a specified target temperature.

In the heat transfer assistance member 26 shown in FIG. 4, the main body 30 is configured with the same cross-sectional shape along the longitudinal direction A, and therefore the protruding portion 31 is configured to have a smaller cross-sectional area than any cross-section of the main body 30. However, the cross-sectional shape of the main body 30 does not have to be the same along the longitudinal direction A, and may vary. In such a case, the cross-sectional area of the protruding portion 31 only needs to be smaller than the cross-sectional area of at least a portion of the cross-section of the main body 30 along its entirety.

In addition, in the fixing device 9 according to this embodiment, since the stay 25 and the side plate 29 are made of a metal material, if the heat transfer assistant member 26 is in direct contact with the stay 25 or the side plate 29, it is considered that the heat of the fixing belt 20 will flow unnecessarily to the stay 25 or the side plate 29 via the heat transfer assistant member 26. In particular, since the stay 25 and the side plate 29 have a large heat capacity, if heat flows into these members, there is a risk that the warm-up time will be longer or the temperature of the fixing belt 20 will drop. Therefore, in this embodiment, the heat transfer assistant member 26 is arranged so as not to come into direct contact with the stay 25 and the side plate 29 so that the heat of the fixing belt 20 will not flow unnecessarily to the stay 25 or the side plate 29 via the heat transfer assistant member 26.

2 and 5, the heat transfer assistant member 26 is in indirect contact with the stay 25 via the resin nip forming member 23. That is, by interposing the resin nip forming member 23, which has a lower thermal conductivity than metal, between the heat transfer assistant member 26 and the metal stay 25, the nip forming member 23 functions as a heat insulator and can suppress the transfer of heat from the heat transfer assistant member 26 to the stay 25. In addition, the side plate 29 is provided with a through hole 35 shown in FIGS. 5 and 6, so that the heat transfer assistant member 26 is arranged in a non-contact state through the through hole 35.

In this manner, in this embodiment, the heat transfer assistant member 26 is positioned so as not to come into direct contact with the stay 25 or the side plate 29, thereby suppressing the transfer of heat from the heat transfer assistant member 26 to the stay 25 or the side plate 29, and reducing the diffusion of heat in the fixing belt 20. This improves the thermal efficiency of the fixing belt 20, shortening the warm-up time and suppressing temperature drops.

Furthermore, in order to maintain the temperature of the fixing belt 20 at a uniform temperature across the width of the maximum image forming area, it is preferable to reduce the temperature deviation between the left and right sides of the fixing belt 20 with respect to the center of the longitudinal direction of the fixing belt 20. Therefore, in this embodiment, the heat transfer assistance member 26 is arranged so as to have a symmetrical shape with respect to the center M2 of the longitudinal direction of the fixing belt 20 (see Figures 5 and 6). This makes it possible to equalize the amount of heat transferred from the fixing belt 20 to the transfer assistance member 26 at one end side and the other end side with respect to the center M2 of the longitudinal direction, thereby making it possible to significantly reduce the temperature deviation between the left and right sides of the fixing belt 20.

The protrusions 31 of the heat transfer support member 26 do not necessarily have to be perfectly symmetrical as long as they have approximately the same heat capacity. Therefore, the position, shape, and number of the identification recesses 34 provided on each protrusion 31 may be different on the left and right.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the spirit of the invention.

In the above embodiment, a free-belt fixing device in which the fixing belt is held in an unstretched state by a pair of belt holding members has been described as an example, but the present invention can also be applied to a configuration in which the fixing belt is stretched around a number of rollers. Furthermore, the present invention is not limited to being applied to a fixing device, which is an example of a heating device. For example, the present invention can also be applied to a heating device such as a drying device that heats paper to dry the ink (liquid) on the paper in an inkjet image forming device.

9 Fixing device (heating device)
20 Fixing belt (first rotating member)
21 Pressure roller (second rotating member)
22 Halogen heater (heat source)
26 Heat transfer auxiliary member 25 Stay (support member)
28 Belt holding member (rotating holding member)
29 Side plate (side wall member)
100 Image forming apparatus

JP 2018-169467 A

Claims (7)

A first rotating member;
a second rotating member that contacts an outer circumferential surface of the first rotating member to form a nip portion;
A heat source that heats the first rotating member;
a heat transfer assistance member that directly or indirectly contacts an inner circumferential surface of the first rotating member at a position of the nip portion;
A metal sidewall member;
A heating device comprising:
a portion of the heat transfer assistance member is disposed outside the first rotating member;
a cross-sectional area of the heat transfer assistance member in a direction intersecting with a longitudinal direction is smaller in a portion of the heat transfer assistance member disposed on the outer side of the first rotating member than in a portion of the heat transfer assistance member disposed on the inner side of the first rotating member;
The sidewall member has a through hole,
A heating device in which a portion of the heat transfer auxiliary member, which is arranged on the outside of the first rotating member, is inserted into the through hole and is arranged so as not to come into contact with the side wall member without any other member between it and the surface forming the through hole . The heat transfer assistance member is formed to be longer in the longitudinal direction than the first rotating member,
The heating device according to claim 1 , wherein both ends in the longitudinal direction of the heat transfer assistance member are disposed outside both ends in the longitudinal direction of the first rotating member. The heating device according to claim 1 or 2, wherein the heat transfer assistance members are arranged symmetrically with respect to the center of the first rotating member in the longitudinal direction. a rotation holding member that rotatably holds the first rotation member at a longitudinal end thereof;
4. The heating device according to claim 1, wherein a part of the heat transfer assistance member is arranged so as to be exposed to the outside of the rotation holding member. The heating device according to claim 1 , wherein a part of the heat transfer assistance member is arranged so as to be exposed to the outside of the side wall member. a metal support member provided on a surface of the first rotating member opposite to a contact surface of the heat transfer assistance member with an inner circumferential surface of the first rotating member, the metal support member supporting the heat transfer assistance member;
6. The heating device according to claim 1, wherein the heat transfer assistance member is in contact with the supporting member via a member having a lower thermal conductivity than the supporting member . An image forming apparatus comprising the heating device according to claim 1 .

Images