JP7315074B2 - Heating device and image forming device - Google Patents

Description

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

2. Description of the Related Art As heating devices used in image forming apparatuses such as copiers and printers, there are known a fixing device that fixes toner on paper by heat, a drying device that dries ink on paper, and the like.

For example, Japanese Patent No. 6336026 discloses a fixing device having a planar heater. In this fixing device, a thermistor as a temperature detecting element is brought into contact with the back side of the heater substrate to detect the temperature of the heater.

However, in the configuration in which the temperature is detected by contacting the thermistor to the heater substrate as in Patent Document 1, the thermistor is likely to be heated by the heat of the heater, so a thermistor with high heat resistance is required.

In order to solve the above-mentioned problems, the present invention provides a heating apparatus comprising a planar heating member having a heat generating portion, an endless belt member provided rotatably, and a pressurizing rotator that forms a nip portion in contact with the outer peripheral surface of the belt member. and non-passing area temperature detecting means for detecting the temperature of the pressurizing rotating body in an area corresponding to the non-passing area of the heat generating portion.

According to the present invention, the non-passing area temperature detecting means is arranged so as to detect the temperature of the pressurizing rotating body in the area corresponding to the non-passing area of the heat generating portion, so that the temperature rise of the non-passing area temperature detecting means can be suppressed.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 1 is a schematic configuration diagram of a fixing device according to an exemplary embodiment; FIG. It is a top view of a heater. It is an exploded perspective view of a heater. It is a figure which shows the state which mounted|worn the heater and the heater holder with the connector. FIG. 4 is a diagram showing the positional relationship between a thermistor, a heat generating portion, and a paper passing area; It is a figure which shows an example of a structure of a 1st thermistor and a 2nd thermistor. It is a figure which shows an example of a structure of a 3rd thermistor. 4 is a graph showing surface temperatures measured on the back surface of the heater and on the nip entrance side and the nip exit side of the pressure roller. FIG. 10 is a diagram showing an example in which a third thermistor is arranged on the nip entrance side; It is a figure which shows the other example of a heater. FIG. 10 is a diagram showing another example of a heater; FIG. 10 is a diagram showing yet another example of a heater; It is a figure which shows the structure provided with a 4th thermistor. It is a figure which shows the structure provided with a 4th thermistor. FIG. 10 is a diagram showing a configuration capable of detecting the temperature of a non-sheet-passing area when erroneously set sheets are passing; FIG. 4 shows a configuration with a thermostat; FIG. 10 is a diagram showing the configuration of another fixing device; FIG. 10 is a diagram showing the configuration of another fixing device; FIG. 10 is a diagram showing the configuration of still another fixing device;

The present invention will be described below with reference to the accompanying drawings. In addition, in each drawing for explaining the present invention, constituent elements such as members and constituent parts having the same function or shape are given the same reference numerals as much as possible, and once explained, the explanation thereof will be omitted.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to one embodiment of the present invention. In addition to the printer, the image forming apparatus may be a copier, a facsimile machine, or a multifunction machine of these.

The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk, which are image forming units. Each of the image forming units 1Y, 1M, 1C, and 1Bk is configured to be detachable from the image forming apparatus main body 103, and has the same configuration except that it accommodates developers of different colors of yellow, magenta, cyan, and black corresponding to color separation components of a color image. Specifically, each of the image forming units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 3 that charges the surface of the photoreceptor 2, a developing device 4 that supplies toner as a developer to the surface of the photoreceptor 2 to form a toner image, and a cleaning device 5 that cleans the surface of the photoreceptor 2.

The image forming apparatus 100 also includes an exposure device 6 that exposes the surface of each photoreceptor 2 to form an electrostatic latent image, a paper feeder 7 that supplies paper P as a recording medium, a transfer device 8 that transfers the toner image formed on each photoreceptor 2 to the paper P, a fixing device 9 that fixes the toner image transferred to the paper P, and a paper discharge device 10 that discharges the paper P to the outside of the device.

The transfer device 8 has an endless intermediate transfer belt 11 as an intermediate transfer body stretched by a plurality of rollers, four primary transfer rollers 12 as primary transfer members for transferring the toner images on the photoreceptors 2 onto the intermediate transfer belt 11, and secondary transfer rollers 13 as secondary transfer members for transferring the toner images transferred on the intermediate transfer belt 11 to the paper P. Each of the primary transfer rollers 12 is in contact with the photoreceptor 2 via the intermediate transfer belt 11 . As a result, the intermediate transfer belt 11 and each photoreceptor 2 come into contact with each other, forming a primary transfer nip therebetween. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretch the intermediate transfer belt 11 through the intermediate transfer belt 11 . A secondary transfer nip is thereby formed between the secondary transfer roller 13 and the intermediate transfer belt 11 .

Further, in the image forming apparatus 100, a paper transport path 14 is formed for transporting the paper P fed from the paper feeding device 7. As shown in FIG. A pair of timing rollers 15 are provided on the paper transport path 14 from the paper feeding device 7 to the secondary transfer nip (secondary transfer roller 13).

Next, the printing operation of the image forming apparatus will be described with reference to FIG.

When there is an instruction to start the printing operation, the photoreceptor 2 in each of the image forming units 1Y, 1M, 1C, and 1Bk is driven to rotate clockwise in FIG. Next, based on the image information of the document read by the document reading device or the print information instructed to print from the terminal, the exposure device 6 exposes the surface of each photoreceptor 2, thereby lowering the potential of the exposed portion and forming an electrostatic latent image. Toner is supplied from the developing device 4 to the electrostatic latent image, and a toner image is formed on each photosensitive member 2 .

When the toner images formed on the photoreceptors 2 reach the primary transfer nip (the position of the primary transfer roller 12) as each photoreceptor 2 rotates, they are sequentially transferred onto the intermediate transfer belt 11 rotating counterclockwise in FIG. Then, the toner image transferred onto the intermediate transfer belt 11 is conveyed 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 conveyed paper P at the secondary transfer nip. This paper P is supplied from the paper feeding device 7 . The paper P supplied from the paper feeding device 7 is temporarily stopped by the timing roller 15, and then conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, the paper P bears a full-color toner image. After the toner image is transferred, toner remaining on each photosensitive member 2 is removed by each cleaning device 5 .

The paper P onto which the toner image has been transferred is conveyed to the fixing device 9 , and the toner image is fixed on the paper P by the fixing device 9 . After that, the paper P is discharged outside the apparatus by the paper discharging device 10, and a series of printing operations is completed.

Next, the configuration of the fixing device 9 will be described.

As shown in FIG. 2, the fixing device 9 according to the present embodiment includes a fixing belt 20 made of an endless belt member as a fixing member, a pressure roller 21 as a pressure rotating body that contacts the outer peripheral surface of the fixing belt 20 to form a nip portion N, and a heating device 19 that heats the fixing belt 20. The heating device 19 includes a planar heater 22 as a heating member, a heater holder 23 as a holding member that holds the heater 22, a stay 24 as a reinforcing member that longitudinally reinforces the heater holder 23, and a plurality of thermistors 25, 26, and 27 as temperature detection means.

The fixing belt 20 has, for example, a cylindrical substrate made of polyimide (PI) having an outer diameter of 25 mm and a thickness of 40 to 120 μm. As the outermost layer of the fixing belt 20, a release layer having a thickness of 5 to 50 μm is formed of a fluorine-based resin such as PFA or PTFE in order to increase durability and ensure release properties. An elastic layer made of rubber or the like having a thickness of 50 to 500 μm may be provided between the substrate and the release layer. Further, the substrate of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK, or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 20 may be coated with polyimide, PTFE, or the like as a sliding layer.

The pressure roller 21 has an outer diameter of 25 mm, for example, and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed outside the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of 3.5 mm, for example. In order to improve the releasability of the surface of the elastic layer 21b, it is desirable to form a release layer 21c of a fluorine resin layer having a thickness of about 40 μm, for example. It is also possible to use a member such as an endless pressure belt instead of the pressure roller 21 as the pressure rotating body that presses the fixing belt 20 .

The heater 22 is provided in a longitudinal shape across the width direction of the fixing belt 20 and arranged so as to be in contact with the inner peripheral surface of the fixing belt 20 . The heater 22 may be in non-contact with the fixing belt 20 or may be in indirect contact with the fixing belt 20 via a low-friction sheet. Further, the heater 22 can be brought into contact with the outer peripheral surface of the fixing belt 20, but if the outer peripheral surface of the fixing belt 20 is damaged by contact with the heater 22, the fixing quality may deteriorate. The heater 22 is configured by sequentially stacking a base layer 50, a conductor layer 51 having a heat generating portion 60, and an insulating layer 52 from the heater holder 23 side toward the nip portion N side.

The heater holder 23 and the stay 24 are arranged inside the fixing belt 20 . The stay 24 is made of a metal channel material, and both end portions thereof are supported by both side wall portions of the fixing device 9 . Since the surface of the heater holder 23 opposite to the heater 22 side is supported by the stay 24, the heater 22 and the heater holder 23 are kept without being greatly bent against the pressure force of the pressure roller 21, and a nip portion N is formed between the fixing belt 20 and the pressure roller 21. - 特許庁

Since the heater holder 23 is likely to reach a high temperature due to the heat of the heater 22, it is desirable to be made of a heat-resistant material. For example, when the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP or PEEK, heat transfer from the heater 22 to the heater holder 23 is suppressed, and the fixing belt 20 can be efficiently heated.

The pressure roller 21 and the fixing belt 20 are pressed against each other by a spring as an urging member. Thereby, a nip portion N is formed between the fixing belt 20 and the pressure roller 21 . Further, the pressure roller 21 functions as a driving roller that is rotationally driven by a driving force transmitted from a driving means provided in the image forming apparatus main body 103 . On the other hand, the fixing belt 20 is configured to rotate following the rotation of the pressure roller 21 . Since the fixing belt 20 slides against the heater 22 during rotation, a lubricant such as oil or grease may be interposed between the heater 22 and the fixing belt 20 in order to improve the slidability of the fixing belt 20 .

When the printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts rotating. Further, the fixing belt 20 is heated by supplying electric power to the heater 22 . Then, in a state where the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG.

3 is a plan view of the heater 22, and FIG. 4 is an exploded perspective view thereof.
In the following description, the fixing belt 20 side (nip portion N side) with respect to the heater 22 will be referred to as "front side", and the heater holder 23 side will be referred to as "back side".

As shown in FIG. 4, the heater 22 is configured by laminating a plurality of constituent layers, including a plate-shaped base layer 50, a conductor layer 51 provided on the front side of the base layer 50, and an insulating layer 52 covering the front side of the conductor layer 51. The conductor layer 51 is composed of a plurality of heat generating portions 60 made of sheet-like resistance heating elements, a plurality of electrode portions 61 provided on both longitudinal end sides of the base layer 50, and a plurality of feeder lines 62 connecting the electrode portions 61 and the heat generating portions 60. Further, as shown in FIG. 3, at least a portion of each electrode portion 61 is not covered with the insulating layer 52 and is exposed in order to ensure connection with a connector, which will be described later.

The base layer 50 is made of an insulating material such as ceramic such as alumina or alumina nitride, or glass. Alternatively, the base material layer 50 may be made of a metal material such as stainless steel (SUS), iron, copper, or aluminum, and an insulating layer may be separately provided between the base material layer 50 and the conductor layer 51 to ensure insulation. A metal material has excellent durability against rapid heating and is easy to process, so it is suitable for cost reduction. Among them, aluminum and copper are preferable because they have high thermal conductivity and are less likely to cause temperature unevenness. In addition, stainless steel has the advantage of being inexpensive to manufacture.

The insulating layer 52 is made of heat-resistant glass. In addition, it is also possible to use ceramics, polyimide (PI), or the like as the material of the insulating layer 52 .

Each heat generating part 60 can be formed by applying a paste prepared by, for example, silver palladium (AgPd) or glass powder to the base material layer 50 by screen printing or the like, and then firing the base material layer 50. As the material of the heating part 60, other than these, a silver alloy (AgPt) or a resistive material such as ruthenium oxide (RuO ₂ ) may be used.

The power supply line 62 is composed of a conductor having a resistance value smaller than that of the heat generating portion 60 . Silver (Ag), silver palladium (AgPd), or the like can be used as the material of the power supply line 62 and the electrode portion 61 . The feeder line 62 and the electrode portion 61 can be formed by screen printing such a material.

In the present embodiment, an alloy such as silver or palladium is used for the heating portion 60, the electrode portion 61, and the power supply line 62, and has PTC characteristics (positive temperature coefficient of resistance). The PTC characteristic is a characteristic in which the resistance value increases as the temperature increases (the heater output decreases when a constant voltage is applied). By using the heat generating portion 60 having the PTC characteristic, it is possible to quickly start up at a low temperature with a high output and to suppress an excessive temperature rise at a high temperature with a low output. For example, if the TCR coefficient of the PTC characteristic is set to about 300 to 4000 ppm/degree, cost reduction can be achieved while securing the necessary resistance value for the heater. More preferably, the TCR coefficient is 500-2000 ppm/degree. The TCR coefficient can be calculated by measuring the resistance at 25 degrees and 125 degrees. For example, if the temperature increases by 100 degrees and the resistance increases by 10%, the TCR coefficient is 1000 ppm/degree.

Further, in the present embodiment, three heat generating portions 60 are provided along the longitudinal direction of the base material layer 50 . One of the three heat-generating portions 60 is a central heat-generating portion 60A as a first heat-generating portion arranged in the center in the longitudinal direction of the base layer 50, and the remaining two are end heat-generating portions 60B as second heat-generating portions arranged on both sides in the longitudinal direction of the central heat-generating portion 60A. The central heat-generating portion 60A and the end heat-generating portions 60B are configured to be capable of heat generation control independently of each other.

In FIG. 3, the plurality of electrode portions 61 are, in order from the left, a first electrode portion 61A, a second electrode portion 61B, a third electrode portion 61C, and a fourth electrode portion 61D. When a voltage is applied to the second electrode portion 61B and the fourth electrode portion 61D, only the central heating portion 60A generates heat. When a voltage is applied to the first electrode portion 61A and the second electrode portion 61B, only the left end heat generating portion 60B in FIG. 3 generates heat, and when a voltage is applied to the second electrode portion 61B and the third electrode portion 61C, only the right end heat generating portion 60B in FIG. 3 generates heat. Further, if the first electrode portion 61A and the third electrode portion 61C are connected in parallel externally so that a voltage can be applied simultaneously, by applying a voltage to these electrode portions 61A and 61C and the second electrode portion 61B, it is possible to simultaneously generate heat in both end heat generating portions 60B. The arrows in FIG. 3 indicate the directions of currents flowing in the longitudinal direction of the heat generating portions 60A and 60B.

When the width of the paper to be passed is equal to or less than the width L1 of the central heat generating portion 60A, only the central heat generating portion 60A is heated, and when the width of the paper to be passed is greater than the width L1 of the central heat generating portion 60, heat is generated not only at the central heat generating portion 60A but also at each end heat generating portion 60B, so that the size of the heat generating region can be changed according to the size of the paper passing region. Furthermore, by matching the width L1 of the central heat generating portion 60A to the width of a small size paper (for example, A4 paper width: 215 mm) and matching the width L2 of the heat generating region including from one end heat generating portion 60B to the other end heat generating portion 60B to the width of a large size paper (for example, A3 paper width: 301 mm), when these papers are passed, an excessive temperature rise in the non-paper-passing area is less likely to occur (on the heat generating portions 60A and 60B). (Since there is almost no paper non-passing area), printing productivity can be improved.

Further, as shown in FIG. 3, in the present embodiment, each of the heat generating portions 60A and 60B has inclined portions 601 inclined with respect to the paper passing direction (vertical direction in FIG. 3) at both ends thereof. In addition, at least a part of the adjacent inclined portions 601 overlap each other in the longitudinal direction of the heater 22 (horizontal direction in FIG. 3), and are arranged in the same region A in the longitudinal direction (see the enlarged view in FIG. 3). By arranging the inclined portions 601 so as to overlap each other in this way, it is possible to suppress the temperature drop between the heat generating portions 60A and 60B, and to reduce uneven fixing in the paper width direction.

FIG. 5 is a perspective view showing a state in which the connector 70 is attached to the heater 22 and the heater holder 23. As shown in FIG.

As shown in FIG. 5 , the connector 70 has a housing 71 made of resin and contact terminals 72 of leaf springs fixed to the housing 71 . The contact terminal 72 has a pair of contact portions 72 a that contact the electrode portions 61 of the heater 22 . A wiring (harness) 73 for power supply is connected to the connector 70 (contact terminal 72).

As shown in FIG. 5, the connector 70 is attached so as to sandwich the heater 22 and the heater holder 23 together from the front side and the back side. As a result, each contact portion 72a of the contact terminal 72 is elastically brought into contact (pressure contact) with the electrode portion 61 of the heater 22, whereby the heat generating portion 60 is electrically connected to the power source provided in the image forming apparatus via the connector 70, and power can be supplied from the power source to the heat generating portion 60. A connector 70 is similarly mounted on the end portion side opposite to the end portion side of the heater 22 shown in FIG.

FIG. 6 is a diagram showing the positional relationship among thermistors 25, 26, 27, heat generating portions 60A, 60B, and paper passing areas W1, W2.

The paper passing area indicated by W1 in FIG. 6 is the widthwise passing area when the paper P1 having a width smaller than the width L1 of the central heat generating portion 60A passes through the nip portion N, and the paper passing area indicated by W2 in FIG.

Here, the thermistor 25, the thermistor 26, and the thermistor 27 are hereinafter referred to as the first thermistor 25, the second thermistor 26, and the third thermistor 27 for convenience. In this manner, the temperature detection portion 25a of the first thermistor 25 is arranged within the width L1 of the central heat generating portion 60A and further within the small size paper passing area W1, so that the first thermistor 25 can detect the temperature of the paper passing area in the central heat generating portion 60A when the small size paper P1 or the paper of each width larger than this is passed. Further, when there are a plurality of types of paper having widths smaller than the width L1 of the central heat generating portion 60A, by disposing the temperature detection portion 25a of the first thermistor 25 in the paper passing area of the paper having the smallest width among them, the first thermistor 25 can detect the temperature of the paper passing areas of all sizes passing over the central heat generating portion 60A.

The temperature detection portion 26a of the second thermistor 26 is arranged outside the width L1 of the central heat generating portion 60A and within the large-size paper passing area W2. In other words, the temperature detecting portion 26a of the second thermistor 26 is arranged corresponding to the paper passing area through which the large size paper P2 passes over the end heat generating portion 60B. In this manner, the temperature detecting portion 26a of the second thermistor 26 is arranged outside the width L1 of the central heat generating portion 60A and within the large size sheet passing area W2, so that the second thermistor 26 can detect the temperature of the sheet passing area in the end heat generating portion 60B when the large size sheet P2 is passed. Further, when there are multiple types of paper passing over the end heat generating portion 60B, the temperature detection portion 2a of the second thermistor 26 is arranged in the paper passing area of the minimum width paper among them, so that the temperature of the paper passing area of all sizes passing over the end heat generating portion 60B can be detected by the second thermistor 26.

The temperature detection portion 27a of the third thermistor 27 is arranged outside the small-size sheet passage area W1 and within the width L1 of the central heat generating portion 60A. In other words, the temperature detection portion 27a of the third thermistor 27 is arranged corresponding to a non-paper-passing region (non-passing region) where the small-sized paper P1 does not pass over the central heat-generating portion 60A. In this manner, the temperature detection portion 27a of the third thermistor 27 is arranged outside the small-size paper passing area W1 and within the width L1 of the central heat generating portion 60A, so that the third thermistor 27 can detect the temperature of the non-paper passing area in the central heat generating portion 60A when the small size paper P1 is passed.

Temperature information detected by each thermistor 25, 26, 27 is sent to a control section for controlling heat generation of each heat generating section 60A, 60B, and each heat generating section 60A, 60B is individually controlled based on the sent temperature information. As a result, the temperature of the nip portion N is controlled to a preset target temperature (fixing temperature). However, when the heat of the heater 22 in the non-sheet-passing area is not consumed much, such as when small-size sheets are continuously passed through, the temperature may rise excessively. In such a case, when the third thermistor 27 detects that the temperature in the non-sheet-passing area has reached or exceeded a predetermined temperature, control is performed to reduce the amount of heat generated by the heater 22 . Furthermore, the temperature rise in the non-paper-passing area is suppressed by lowering the sheet conveying speed, widening the sheet conveying interval, or stopping image formation.

In the present embodiment, the central heat generating portion 60A and the end heat generating portions 60 have inclined portions 601 at their respective longitudinal end portions. Therefore, if the temperature detection portions 26a and 27a of the second thermistor 26 and the third thermistor 27 are arranged in the region corresponding to the inclined portion 601, there is a possibility that the temperature detection accuracy is lowered. Therefore, as shown in FIG. 6, the temperature detection portions 26a and 27a of the second thermistor 26 and the third thermistor 27 are preferably arranged in a portion other than the inclined portion 601 of the central heat generating portion 60A or the inclined portion 601 of the end heat generating portion 60B (for example, the central side in the longitudinal direction of the heat generating portions 60A and 60B). Thereby, the temperature detection accuracy of the second thermistor 26 and the third thermistor 27 can be improved.

Further, in the present embodiment, the second thermistor 26 is arranged only on the one end heat generating portion 60B side, but the second thermistor 26 may also be arranged on the other end heat generating portion 60B side. However, in the case of a so-called center-conveyance-based image forming apparatus in which sheets of paper P1 and P2 of each size are conveyed with their widthwise central position M aligned, as in the present embodiment, the temperature distribution of the fixing belt is basically left-right symmetrical with respect to the widthwise central position M of the paper.

By the way, the first thermistor 25 and the second thermistor 26, which serve as sheet passing area sensors (passing area temperature detection means) arranged corresponding to the sheet passing area, control the temperature of the sheet passing area to an appropriate value. Therefore, as shown in FIG. 2, the first thermistor 25 and the second thermistor 26 are arranged so as to contact the back surface of the heater 22 (the surface opposite to the nip portion N side). Since the first thermistor 25 and the second thermistor 26 are arranged so as to be in contact with the back surface of the heater 22, the temperature of the heater 22, which is a heat source and is close to the nip portion N, can be directly detected, and the temperature of the paper passing area can be controlled to an appropriate temperature based on the detection result.

On the other hand, the third thermistor 27 serving as a non-paper-passing area sensor (non-passing area temperature detecting means) arranged corresponding to the paper-non-passing area may detect an excessive temperature rise in the non-paper-passing area to prevent damage or deterioration of the fixing device, rather than the temperature of the paper-passing area, which greatly affects the fixing quality. Therefore, in this embodiment, as shown in FIG. 2, the third thermistor 27 is arranged not near the heater 22 but so as to face the outer peripheral surface of the pressure roller 21 . When the temperature of the non-paper-passing area in the nip portion N rises, the surface temperature of the pressure roller 21 in the corresponding area also rises. By detecting the temperature of the pressure roller 21 with the third thermistor 27, it is possible to prevent excessive temperature rise in the paper-non-passing area.

Thus, in this embodiment, the third thermistor 27 is arranged to face the outer peripheral surface of the pressure roller 21 . With such an arrangement, the temperature of the third thermistor 27 is less likely to rise than the temperature of the first thermistor 25 and the second thermistor 26 . That is, since the third thermistor 27 is located farther from the heater 22, which becomes hotter than the first thermistor 25 and the second thermistor 26, the third thermistor 27 is less likely to be exposed to the heat of the heater 22 and less likely to raise its temperature. As a result, the third thermistor 27 does not need to have heat resistance as high as that of the first thermistor 25 and the second thermistor 26, so that an inexpensive thermistor with lower heat resistance than the first thermistor 25 and the second thermistor 26 can be used as the third thermistor 27, and the cost of the fixing device 9 can be reduced.

7 shows an example of the configuration of the first thermistor 25 and the second thermistor 26, and FIG. 8 shows an example of the configuration of the third thermistor 27. As shown in FIG.

As shown in FIG. 7, the first thermistor 25 and the second thermistor 26 have a holder 30, an elastic member 31, a temperature detecting element 32 as the temperature detecting portions 25a and 26a, a spring 33 as a biasing member, and an insulating sheet 34. The holder 30 is made of a resin material such as LCP, and is provided with a temperature detection element 32 via an elastic member 31 on the surface facing the heater 22 . The elastic member 31 is made of a material having lower thermal conductivity and rigidity than the holder 30, and has elasticity and heat insulation. The insulating sheet 34 is made of an insulating material such as PI (polyimide), and is provided so as to cover the holder 30 , the elastic member 31 and the temperature detection element 32 . The holder 30 is biased toward the heater 22 by a spring 33 so that the temperature detection element 32 is in contact with the heater 22 via the insulating sheet 34 . Two wires (lead wires) 35 connected to the temperature detection element 32 extend from the holder 30, and each wire 35 is covered with an insulating film. Considering heat resistance, the coating of the wiring 35 preferably has a thickness of, for example, 0.4 mm or more. Moreover, when the thickness of the coating is 0.4 mm or less, a plurality of coatings may be laminated.

On the other hand, as shown in FIG. 8, the third thermistor 27 has a holder 36, a temperature sensing element 37 as a temperature sensing portion 27a, and an insulating sheet 38. As shown in FIG. The temperature detection element 37 is provided on the holder 36 and faces the outer peripheral surface of the pressure roller 21 with the insulating sheet 38 interposed therebetween. Two wires (lead wires) 39 connected to the temperature detection element 37 extend from the holder 36, and each wire 39 is covered with an insulating film.

Since the third thermistor 27 may have lower heat resistance than the first thermistor 25 and the second thermistor 26, it does not have an elastic member having a heat insulating effect. Further, since the heat resistance of the third thermistor 27 can be lowered, the holder 36 can be made of a material having lower heat resistance than the holders 30 of the first thermistor 25 and the second thermistor 26 . Also, the coating of the wiring 39 of the third thermistor 27 can be made of a material with lower heat resistance than the coating of the wiring 35 of the first thermistor 25 and the second thermistor 26, or can be made thinner or the number of films can be reduced. Furthermore, in this example, since the third thermistor 27 is of a type that detects the temperature without contacting the pressure roller 21, there is no need to provide an urging member for bringing the temperature detection element 37 into contact with the pressure roller 21, and the configuration can be made at low cost.

FIG. 9 is a graph showing the surface temperatures of the back surface of the heater 22 and the surface temperatures of the pressure roller 21 on the nip entrance side (rotational direction upstream side of the nip portion N) and nip exit side (rotational direction downstream side of the nip portion N).

In FIG. 9, T1 is the result of measuring the temperature of the back surface of the heater 22 with a thermocouple. T2 is the result of measuring the temperature on the nip outlet side of the pressure roller 21 with a thermo viewer, and T3 is the result of measuring the temperature on the nip inlet side of the pressure roller 21 with the same thermo viewer. Each temperature is the temperature after 30 sheets of A6 size plain paper P having a width smaller than that of the central heat generating portion 60A are passed in the vertical direction per minute and fixed.

As shown in FIG. 9, in this measurement test, the temperature T1 on the back surface of the heater 22 rose to 230°C, while the temperature T2 on the nip exit side of the pressure roller 21 only rose to 200°C, and the temperature T3 on the nip entrance side rose only to 185°C. Thus, it was confirmed that the surface temperature of the pressure roller 21 is lower than the temperature of the back surface of the heater 22 on both the nip exit side and the nip entrance side. Furthermore, the temperature T3 on the nip entrance side of the pressure roller 21 is lower than the temperature T2 on the nip exit side. It is considered that the temperature on the nip entrance side is lower than that on the nip exit side immediately after heating due to heat conduction in the elastic layer due to the rotation of the pressure roller 21 and heat radiation from the pressure roller 21 to the outside.

From the results shown in FIG. 9, in order to more effectively suppress the temperature rise of the third thermistor 27, it is preferable to dispose the third thermistor 27 on the surface of the pressure roller 21, particularly on the upstream side of the nip portion N in the rotational direction of the pressure roller 21 (hereinafter referred to as the "nip inlet side").

FIG. 10 shows an example in which the third thermistor 27 is arranged on the nip entrance side.

In FIG. 10, the third thermistor 27 is of a contact type arranged in contact with the outer peripheral surface of the pressure roller 21, but may be of a non-contact type. By arranging the third thermistor 27 on the nip entrance side in this way, it becomes possible to effectively suppress the temperature rise of the third thermistor 27, and it becomes possible to use a cheaper thermistor with low heat resistance. If the third thermistor 27 cannot be arranged on the nip entrance side due to the layout of parts, etc., the third thermistor 27 may be arranged downstream of the nip portion N in the rotation direction of the pressure roller 21 (nip exit side) or at other locations on the pressure roller 21. Even in that case, the temperature rise can be suppressed more than when the third thermistor 27 is arranged near the heater 22, so it is possible to use an inexpensive thermistor with low heat resistance.

In addition, since the heat flow rate of the elastic layer of the pressure roller 21 accompanying rotation is proportional to the thermal conductivity and cross-sectional area of the elastic layer 21b, by increasing these, the surface temperature of the pressure roller 21 on the nip entrance side can be further reduced, and the temperature rise of the third thermistor 27 can be further suppressed. In order to secure a large cross-sectional area of the elastic layer 21b, it is desirable to set the outer diameter of the pressure roller 21 to 20 mm or more and the thickness of the elastic layer 21b to 2 mm or more. Further, the elastic layer 21b preferably has a thermoelectric constant of 0.1 W/mK or more, more preferably 0.2 W/mK or more. Thermal conductivity can be measured using, for example, ai-Phase Mobile2 manufactured by i-Phase. It is also possible to improve the thermal conductivity of the pressure roller 21 in the longitudinal direction by adding an additive having good thermal conductivity to the material of the elastic layer 21b.

Moreover, the configuration of the heater 22 to which the present invention is applied may be the configuration shown in FIG. 11, FIG. 12, or FIG. 13 in addition to the above example.

In the example shown in FIG. 11, the central heat generating portion 60A is divided into a plurality of heat generating blocks 59 along its longitudinal direction. In this way, by dividing the central heating portion 60A into a plurality of short heating blocks 59 instead of one long heating block, the widths of the heating blocks 59 and the end heating portions 60B become substantially the same, and the resistance values thereof can be made substantially the same. For example, when the width L1 of the central heat generating portion 60A is the width of A4 paper (215 mm) and the width L2 of the heat generating region including the heat generating portions 60B at both ends is the width of A3 paper (301 mm), by dividing the central heat generating portion 60A into five heat generating blocks 59, the heat generating blocks 59 and the end heat generating portions 60B can have the same width (43 mm). As a result, the respective resistance values of the heat generating blocks 59 and the end heat generating portions 60B become substantially the same, so that the fixing belt 20 can be uniformly heated across the width direction.

Furthermore, in the example shown in FIG. 12, each heat generating block 59 of the central heat generating portion 60A and each end heat generating portion 60B are formed in a folded pattern. In this case, current flows along the folded pattern.

Further, in the example shown in FIG. 13, each of the heat-generating portions 60A and 60B is connected to the power supply line 62 at each end portion in the short direction. In this case, as indicated by the arrows in FIG. 16, current flows in the longitudinal direction and the lateral direction (oblique direction) of each of the heat generating portions 60A and 60B.

Embodiments different from the above-described embodiments will be described below. Mainly different parts will be explained, and other parts are basically the same as the above-described embodiment, so the explanation will be omitted.

In the embodiment shown in FIG. 14, in addition to the first thermistor 25, the second thermistor 26, and the third thermistor 27, the fixing device 9 includes a fourth thermistor 28 as a non-paper-passing area sensor (non-passing area temperature detecting means) for detecting the temperature of the non-paper-passing area (non-passing area) of the end heat generating portion 60B. The temperature detection portion 28a of the fourth thermistor 28 is arranged outside the large-size sheet passing area W2 and within the width of the end heat generating portion 60B (within the width L2 including both end heat generating portions 60B). As a result, the fourth thermistor 28 can detect the temperature of the non-paper-passing area of the end heating portion 60B when the large-sized paper P2 is passed. Further, in order to improve the temperature detection accuracy of the fourth thermistor 28, it is desirable that the temperature detection portion 28a of the fourth thermistor 28 is arranged corresponding to a portion of the end heat-generating portion 60B other than the inclined portion 601 (the central side in the longitudinal direction of the end heat-generating portion 60B), similarly to the second thermistor 26 and the third thermistor 27.

Like the third thermistor 27, the fourth thermistor 28, which detects the temperature of the non-sheet-passing area, may have slightly lower temperature detection responsiveness and accuracy than the first thermistor 25 and the second thermistor 26. Therefore, as shown in FIG. 15, the fourth thermistor 28 may also be arranged (near the pressure roller 21) so as to detect the temperature of the pressure roller 21, similarly to the third thermistor 27. FIG. By arranging the fourth thermistor 28 in the vicinity of the pressure roller 21 in this way, the temperature rise of the fourth thermistor 28 can be suppressed more than the first thermistor 25 and the second thermistor 26, and an inexpensive thermistor with low heat resistance can be used as the fourth thermistor 28. Furthermore, by arranging the fourth thermistor 28 on the nip inlet side of the pressure roller 21 having a lower surface temperature, the temperature rise of the fourth thermistor 28 can be more effectively suppressed.

Next, in the embodiment shown in FIG. 16, the third thermistor 27 can detect the temperature rise in the paper non-passing area even when the paper is erroneously set. Specifically, the temperature detection portion 27a of the third thermistor 27 is arranged within the width L1 of the central heat generating portion 60A and further outside the paper passing area W3' in the case of erroneous setting. The paper passing area W3′ when there is an erroneous setting is a paper passing area when the paper P3 is erroneously brought to one side in the width direction and misaligned in the width direction from the normal position (the position indicated by the solid line in FIG. 16), and the paper P3 is conveyed as it is without correction of the deviation. As described above, in the present embodiment, the temperature detection portion 27a of the third thermistor 27 is arranged within the width L1 of the central heat generating portion 60A and further outside the paper passing region W3′ in the case of erroneous setting, so that the third thermistor 27 can detect the temperature of the non-paper passing region in the central heat generating portion 60A when the erroneously set paper P3 is passed.

Further, in the example shown in FIG. 16, the width L1 of the central heat generating portion 60A is set to the same width size as the paper P3. In this case, when the paper P3 is passed at the regular position indicated by the solid line in FIG. 19, the third thermistor 27 detects the temperature of the paper passing area in the central heating portion 60A. On the other hand, when the sheet P3 is passed at the erroneously set position indicated by the two-dot chain line in FIG. 19, the third thermistor 27 detects the temperature of the non-sheet-passing area in the central heat-generating portion 60A. In this way, when there is an erroneous setting, the third thermistor 27 detects the temperature of the non-paper-passing area, and basically higher temperature is detected than the temperature of the paper-passing area detected when there is no erroneous setting. Therefore, by confirming the difference in temperature detected by the third thermistor 27 at this time, it is possible to determine whether or not there is an erroneous setting. When it is determined that the setting is incorrect, image formation is stopped, and the user is notified of the incorrect setting by sound, screen display, or the like, so that the incorrect setting state can be resolved. Note that the configuration for determining whether or not there is such an erroneous setting is not limited to the case where the width of the sheet P3 and the width L1 of the central heat generating portion 60A are the same size. If the area where the third thermistor 27 is arranged changes depending on whether or not there is an erroneous setting, it is possible to determine whether or not there is an erroneous setting by similarly confirming the difference in temperature detected by the third thermistor 27 if the type of paper changes between a paper passing area and a non-paper passing area.

Next, in the embodiment shown in FIG. 17, the fixing device 9 has two thermostats 41 and 42 in addition to the three thermistors 25, 26, and 27. As shown in FIG. The two thermostats 41 and 42 function as power cut-off means for cutting power to the heat generating portions 60A and 60B when it is detected that the temperatures of the heat generating portions 60A and 60B are equal to or higher than a predetermined temperature. Specifically, each of the thermostats 41 and 42 is arranged in contact with the back surface of the heater 22 . One thermostat 41 is electrically connected to an electrode portion 61D that supplies power to the central heating portion 60A, and the other thermostat 42 is electrically connected to an electrode portion 61A that supplies power to the end heating portion 60B. When the thermostats 41 and 42 detect excessive temperature rise in the heat generating portions 60A and 60B, power supply to the heat generating portions 60A and 60B is interrupted, thereby stopping further heat generation of the heater 22. FIG. A fuse may be used instead of the thermostat as the current interrupting means.

Also, as in the example shown in FIG. 17, when the central heat generating portion 60A is composed of a plurality of heat generating blocks 59 connected in parallel, the thermostat 41 arranged in the central heat generating portion 60A is desirably arranged in the same heat generating block 59 as the heat generating block 59 in which the first thermistor 25 is arranged. Thus, by arranging the thermostat 41 and the first thermistor 25 in the same heat generating block 59, even if the heat generating block 59 is disconnected and the thermostat 41 cannot detect excessive temperature rise, the first thermistor 25 detects an abnormal temperature drop caused by the disconnection, so that the failure of the heater 22 can be grasped.

In addition, in the example shown in FIG. 17, two thermostats 41 and 42 are housed in addition to the first thermistor 25 and the second thermistor 26 on the inner circumference of the fixing belt 20, so the number of wirings arranged in the fixing belt 20 is increased. In such a case, if all the wiring connected to the external device 80 such as the control section or the power supply section is exposed to the outside from one end of the fixing belt 20, it becomes difficult to perform the wiring work, especially with the fixing belt 20 having a small diameter, and there is a risk that the workability will decrease. In addition, since it is necessary to secure a space for the wires to pass through, it also prevents the diameter of the fixing belt 20 from being reduced.

Therefore, in the example shown in FIG. 17, some of the wires k1, k2, k3 among the plurality of wires connected to the first thermistor 25, the second thermistor 26, and the thermostats 41, 42 are exposed to the outside from the one end 21a side of the fixing belt 20, and the other wires m1, m2, m3 are exposed to the outside from the other end 21b side of the fixing belt 20. In this way, by exposing the wiring separately on one end side and the other end side of the fixing belt 20, it is possible to avoid a reduction in wiring work due to concentration of the wiring on one end and an obstacle to reducing the diameter of the fixing belt 20.例文帳に追加

As described above, in the fixing device according to each of the above-described embodiments, when a sheet of a specific width is passed through the nip portion, a portion of the heat-generating portion serves as a paper-passing region and the other region serves as a non-paper-passing region. In addition, since the temperature rise of the thermistor is suppressed, it becomes possible to use a thermistor with low heat resistance, and the cost can be reduced.

In each of the above-described embodiments, a configuration having a plurality of heat generating portions (the central heat generating portion 60A and the end heat generating portions 60B) that are independently controlled as heaters is taken as an example.

In addition, when the configuration according to the present invention is applied to a heater having PTC characteristics, a greater effect can be expected. That is, when the heater has the PTC characteristic, when the temperature rises in the non-paper-passing area, the resistance value of that portion rises and the amount of heat generated increases, resulting in a significant temperature rise. Therefore, in a configuration using a heater having such a PTC characteristic, the temperature rise of the thermistor can be effectively suppressed by moving the thermistor that detects the temperature of the non-sheet-passing area away from the heater and arranging it near the pressure roller. Note that the temperature rise in the non-paper-passing area due to the above-described PTC characteristic similarly occurs in the heater 22 shown in FIG. 3 as well as the heaters 22 shown in FIGS.

In addition to the fixing device described above, the present invention can also be applied to fixing devices as shown in FIGS. 18 to 20. FIG. The configuration of each fixing device shown in FIGS. 18 to 20 will be briefly described below.

First, the fixing device 9 shown in FIG. 18 has a pressure roller 90 arranged on the opposite side of the fixing belt 20 from the pressure roller 21 side, and is configured to sandwich and heat the fixing belt 20 between the pressure roller 90 and the heater 22. On the other hand, a nip forming member 91 is arranged on the inner periphery of the fixing belt 20 on the pressure roller 21 side. The nip forming member 91 is supported by the stay 24 , and the fixing belt 20 is sandwiched between the nip forming member 91 and the pressure roller 21 to form a nip portion N.

Next, in the fixing device 9 shown in FIG. 19, the pressure roller 90 described above is omitted, and the heater 22 is formed in an arc shape in accordance with the curvature of the fixing belt 20 in order to secure the contact length between the fixing belt 20 and the heater 22 in the circumferential direction. Otherwise, the configuration is the same as that of the fixing device 9 shown in FIG.

Finally, in the fixing device 9 shown in FIG. 20, a pressure belt 92 is provided in addition to the fixing belt 20, and the heating nip (first nip portion) N1 and the fixing nip (second nip portion) N2 are separated. That is, a nip forming member 91 and a stay 93 are arranged on the opposite side of the pressure roller 21 from the fixing belt 20 side, and the pressure belt 92 is rotatably arranged so as to enclose the nip forming member 91 and stay 93 . Then, the paper P is passed through the fixing nip N2 between the pressure belt 92 and the pressure roller 21 and heated and pressed to fix the image. Otherwise, the configuration is the same as that of the fixing device 9 shown in FIG.

Although the configurations of various fixing devices have been described above, the heating device according to the present invention is not limited to being applied to fixing devices. For example, the heating device according to the present invention can also be applied to a drying device installed in an inkjet image forming apparatus in order to dry ink applied to paper. Furthermore, the heating device according to the present invention is not limited to a heating device that heats paper as a member to be heated. For example, the present invention can also be applied to a coating device (laminator) that stacks a film as a coating member on the surface of a sheet and heats and presses them.

9 fixing device 19 heating device 20 fixing belt (belt member)
21 pressure roller (pressure rotating body)
22 heater (heating member)
25 first thermistor (passing area temperature detection means)
26 second thermistor (passing area temperature detection means)
27 third thermistor (non-passing area temperature detection means)
28 fourth thermistor (non-passing area temperature detection means)
30 holder 32 temperature detection element 34 insulation sheet 35 wiring 36 holder 37 temperature detection element 38 insulation sheet 39 wiring 60 heating part 60A central heating part 60B end heating part P paper (recording medium, member to be heated)
N Nip part

Japanese Patent No. 6336026

Claims (12)

a planar heating member having a plurality of heat generating portions capable of controlling heat generation independently of each other;
a rotatably provided endless belt member;
a pressure rotating body that forms a nip portion by contacting the outer peripheral surface of the belt member;
with
The heat generating portion has a PTC characteristic, and the direction of the current flowing to the heat generating portion is a direction that intersects the passage direction of the member to be heated passing through the nip portion,
When a heating target member having a specific width is passed through the nip portion to heat the heating target member, a part of the region of the heat generating portion becomes a passing region through which the heating target member passes, and the other region becomes a non-passing region through which the heating target member does not pass,
The plurality of heat generating portions includes a central heat generating portion arranged in the center of the heating member in the longitudinal direction, and end heat generating portions arranged closer to the ends in the longitudinal direction of the heating member than the central heat generating portion,
a first temperature detection means arranged in a region corresponding to the central heat generating portion and detecting the temperature of the heating member;
a second temperature detection means arranged in a region corresponding to the end heat generating portion and detecting the temperature of the heating member;
non-passing area temperature detection means for detecting the temperature of the pressurizing rotating body in an area corresponding to the non-passing area of the end heat generating portion;
The heating device, wherein the non-passing region temperature detection means is arranged closer to the end than the second temperature detection means in the longitudinal direction of the heating member. a planar heating member having a plurality of heat generating portions capable of controlling heat generation independently of each other;
a rotatably provided endless belt member;
a pressure rotating body that forms a nip portion by contacting the outer peripheral surface of the belt member;
with
The heat generating portion has a PTC characteristic, and the direction of the current flowing to the heat generating portion is a direction that intersects the passage direction of the member to be heated passing through the nip portion,
When a heating target member having a specific width is passed through the nip portion to heat the heating target member, a part of the region of the heat generating portion becomes a passing region through which the heating target member passes, and the other region becomes a non-passing region through which the heating target member does not pass,
The plurality of heat generating portions includes a central heat generating portion arranged in the center of the heating member in the longitudinal direction, and end heat generating portions arranged closer to the ends in the longitudinal direction of the heating member than the central heat generating portion,
a first temperature detection means arranged in a region corresponding to the central heat generating portion and detecting the temperature of the heating member;
a second temperature detection means arranged in a region corresponding to the end heat generating portion and detecting the temperature of the heating member;
first non-passing area temperature detection means for detecting the temperature of the pressurizing rotating body in an area corresponding to the non-passing area of the central heat generating portion;
a second non-passing area temperature detection means for detecting the temperature of the pressurizing rotating body in an area corresponding to the non-passing area of the end heat generating portion;
The first non-passing area temperature detection means is arranged between the first temperature detection means and the second temperature detection means in the longitudinal direction of the heating member,
The heating device, wherein the second non-passing area temperature detection means is arranged closer to the end than the second temperature detection means in the longitudinal direction of the heating member. 2. The heating device according to claim 1, wherein said non-passing area temperature detecting means is a thermistor. 3. The heating device according to claim 2, wherein both the first non-passing area temperature detecting means and the second non-passing area temperature detecting means are thermistors. 5. The heating device according to claim 1, wherein both said first temperature detection means and said second temperature detection means are thermistors. 5. The heating device according to any one of claims 1 to 4, further comprising a plurality of thermostats that detect the temperature of said heating member. the heating member is disposed inside the belt member;
5. The heating device according to any one of claims 1 to 4, wherein both the first temperature detection means and the second temperature detection means are arranged on the back side of the heating member. 7. The heating device according to claim 6, wherein said first temperature detection means, said second temperature detection means, and said plurality of thermostats are all arranged on the back side of said heating member. An image forming apparatus comprising the heating device according to claim 1 . An image forming apparatus comprising the heating device according to claim 6 . An image forming apparatus comprising the heating device according to claim 7 . An image forming apparatus comprising the heating device according to claim 8 .

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