JP2022145420A - Temperature detection member, heating device, fixing device, and image forming apparatus - Google Patents

Abstract

To prevent adherence of liquid to a temperature detection element or to the periphery thereof.SOLUTION: A thermistor 25 comprises a temperature detection element 251 and a leaf spring 252. The leaf spring 252 is in contact with the temperature detection element 251 to press the temperature detection element 251 toward a heater 22. The leaf spring 252 has a lower side extension part 252d that extends to a lower side in the gravity direction from a contact part 252c in contact with the temperature detection element 251 when attached to the heater 22.SELECTED DRAWING: Figure 8

Description

The present invention relates to a temperature detecting member, a heating device, a fixing device and an image forming apparatus.

It is known that image forming devices such as copiers and printers are equipped with heating members that generate heat, such as a fixing device that fixes toner on paper by heat and a drying device that dries ink on paper. It is Generally, in an apparatus having such a heating member, a temperature sensing member such as a thermistor is provided to sense the temperature of the heating member or the temperature of the member heated by the heating member.

For example, in the fixing device disclosed in Japanese Patent Application Laid-Open No. 2020-91271, a thermistor is provided on the back side of the base material of the heater. A temperature sensing element provided in the thermistor is pressurized by a coil spring via a cushioning material such as sponge or rubber, and is pressed against the back surface of the base material by this pressurizing force.

By the way, in the heating device, a lubricant (liquid) is applied between the inner peripheral surface of the rotating member and the heating member in order to reduce friction therebetween and to rotate the rotating member smoothly. Then, there is a risk that this lubricant will flow into the temperature detecting member side and be absorbed by the cushioning material near the temperature detecting element, impairing the responsiveness of the temperature detecting member.

An object of the present invention is to suppress the influence of liquid adhering to a temperature sensing element or its surroundings.

In order to solve the above-described problems, the present invention provides a temperature detection member including a temperature detection element and a spring, wherein the spring contacts the temperature detection element to move the temperature detection element to a member to be detected. The spring is attached to the member to be detected and has a downward extending portion that extends downward in the direction of gravity from a contact portion that contacts the temperature detecting element. do.

According to the temperature detection member of the present invention, it is possible to suppress the influence of liquid adhering to the temperature detection element or its surroundings.

1 is a schematic configuration diagram of an image forming apparatus; FIG. 1 is a side sectional view showing a schematic configuration of a fixing device according to an embodiment of the invention; FIG. It is a top view of a heater. FIG. 4 is a diagram showing power supply to the heater; It is a perspective view of the state where the connector was attached to the heater and the heater holder. FIG. 4 is a plan view of a heater having a resistive heating element with a different shape from that in FIG. 3 ; FIG. 7 is a plan view of a heater having a different shape of a resistance heating element from FIGS. 3 and 6; 1 is a schematic diagram showing the configuration of a thermistor; FIG. It is a figure which shows the wraparound path|route of lubricating oil. FIG. 4 is a schematic diagram showing a thermistor having a configuration different from that of the present invention; It is a figure which shows the path|route of the lubricating oil in the thermistor of this embodiment. FIG. 9 is a schematic diagram showing a thermistor having a configuration different from that of FIG. 8; FIG. 4 is a side view showing a pressure mechanism that presses a pressure roller; FIG. 3 is a plan view showing an example of a detailed configuration of a thermistor; FIG. 4 is a side view showing an example of the detailed configuration of the thermistor; Fig. 10 shows an example of a different arrangement of thermistors; FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 2 is a schematic configuration diagram of an image forming apparatus different from FIG. 1; 1 is a side sectional view showing a schematic configuration of a fixing device according to an embodiment of the invention; FIG. 22 is a plan view of a heater in the fixing device of FIG. 21; FIG. It is a perspective view of a heater and a heater holder. It is a perspective view which shows the attachment state of the connector with respect to a heater. It is a figure which shows arrangement|positioning of a thermistor and a thermostat. It is a figure which shows the groove part of a flange.

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 will be repeated. omitted. In the following description, a fixing device for fixing a toner image by heat is exemplified as an example of a heating device having a temperature detecting member.

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

The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk detachable from the main body of the image forming apparatus. Each of the image forming units 1Y, 1M, 1C, and 1Bk has the same configuration except that it accommodates different color developers of yellow, magenta, cyan, and black. These colors of developer correspond to the color separations of the color image. Each of the image forming units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photosensitive member 2 as an image carrier, a charging device 3, a developing device 4, and a cleaning device 5. A charging device 3 charges the surface of the photoreceptor 2 . The developing device 4 supplies toner as a developer onto the surface of the photoreceptor 2 to form a toner image. A cleaning device 5 cleans the surface of the photoreceptor 2 .

The image forming apparatus 100 also includes an exposure device 6 , a paper feed device 7 , a transfer device 8 , a fixing device 9 and a paper discharge device 10 . The exposure device 6 exposes the surface of each photoreceptor 2 to form an electrostatic latent image on the surface. The paper feeding device 7 supplies paper P as a recording medium to the paper transport path 14 . The transfer device 8 transfers the toner image formed on each photoreceptor 2 onto the paper P. As shown in FIG. The fixing device 9 fixes the toner image transferred to the paper P onto the surface of the paper P. As shown in FIG. The paper discharge device 10 discharges the paper P to the outside of the device. Each image forming unit 1, photoreceptor 2, charging device 3, exposure device 6, transfer device 8, etc. constitute image forming means for forming an image on a sheet.

The transfer device 8 has an endless intermediate transfer belt 11 as an intermediate transfer body, four primary transfer rollers 12 as primary transfer members, and secondary transfer rollers 13 as secondary transfer members. The intermediate transfer belt 11 is stretched by a plurality of rollers. A primary transfer roller 12 transfers the toner image on each photoreceptor 2 to an intermediate transfer belt 11 . The secondary transfer roller 13 transfers the toner image transferred onto the intermediate transfer belt 11 onto the paper P. As shown in FIG. 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 .

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, in each of the image forming units 1Y, 1M, 1C, and 1Bk, the photoreceptor 2 is driven to rotate clockwise in FIG. charged to a potential. Next, the exposure device 6 exposes the surface of each photoreceptor 2 based on the image information of the document read by the document reading device or the print information instructed to print from the terminal. As a result, the potential of the exposed portion is lowered to form 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 .

The toner image formed on each photoreceptor 2 rotates as each photoreceptor 2 rotates and reaches the primary transfer nip (the position of the primary transfer roller 12). The toner images are transferred onto the intermediate transfer belt 11 rotating counterclockwise in FIG. 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. The toner image 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 will be described.

As shown in FIG. 2, the fixing device 9 according to this embodiment includes a fixing belt 20 as a rotating member or a fixing member, a pressure roller 21 as a counter rotating member or a pressure member, and a heater 22 as a heating member. , a heater holder 23 as a holding member, a stay 24 as a support member, a plurality of thermistors 25 and the like. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer peripheral surface of the fixing belt 20 to form a fixing nip N with the fixing belt 20 . A heater 22 heats the fixing belt 20 . A heater holder 23 holds the heater 22 . The stay 24 supports the heater holder 23 . Thermistor 25 senses the temperature of substrate 30 . That is, the heater 22 is a detected member whose temperature is detected by the thermistor 25 (or thermostat). The direction perpendicular to the plane of FIG. 2 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, etc. Hereinafter, this direction is simply referred to as the longitudinal direction. The longitudinal direction is also the width direction of the sheet to be conveyed, the width direction of the fixing belt 20 , and the axial direction of the pressure roller 21 .

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. This tubular substrate includes the inner peripheral surface of the fixing belt 20 . 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 comprises a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer formed on the outer side of the elastic layer 21b. 21c. The elastic layer 21b is made of silicone rubber and has a thickness of 3.5 mm, for example. On the surface of the elastic layer 21b, it is desirable to form a release layer 21c made of a fluororesin layer having a thickness of about 40 μm, for example, in order to improve release properties.

The pressing roller 21 is pressed against the heater 22 via the fixing belt 20 by pressing the pressing roller 21 toward the fixing belt 20 by the pressing means. Thereby, a fixing nip N is formed between the fixing belt 20 and the pressure roller 21 . Further, the pressure roller 21 is configured to be rotationally driven by a driving means, and when the pressure roller 21 rotates in the direction of the arrow in FIG. 2, the fixing belt 20 is driven to rotate accordingly.

The heater 22 is a planar heating member provided in a longitudinal shape across the width direction of the fixing belt 20 . The heater 22 includes a plate-like substrate 30, a resistance heating element 31 provided on the substrate 30, an insulating layer 32 covering the resistance heating element 31, and the like. The heater 22 is in contact with the inner peripheral surface of the fixing belt 20 on the insulating layer 32 side, and the heat generated from the resistance heating element 31 is transmitted to the fixing belt 20 via the insulating layer 32 . be. In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (fixing nip N side) of the base material 30 . may be provided on the heater holder 23 side. In that case, the heat of the resistance heating element 31 is transmitted to the fixing belt 20 through the base material 30, so the base material 30 is preferably made of a material with high thermal conductivity such as aluminum nitride. Further, by configuring the base material 30 with a material having a high thermal conductivity, the fixing belt 20 can be sufficiently heated even when the resistance heating element 31 is arranged on the opposite side of the base material 30 from the fixing belt 20 side. is possible.

The heater holder 23 and the stay 24 are arranged on the inner peripheral side of the fixing belt 20 . The stay 24 is made of a metal channel material, and both end portions of the stay 24 are supported by both side plates of the fixing device 9 . By supporting the heater holder 23 and the heater 22 by the stay 24 , the heater 22 can reliably receive the pressing force of the pressure roller 21 while the pressure roller 21 is pressed against the fixing belt 20 . Thereby, the fixing nip N is stably formed between the fixing belt 20 and the pressure roller 21 . In this embodiment, the heat conductivity of the heater holder 23 is set lower than that of the base material 30 .

Next, a method for calculating the above thermal conductivity will be described. When calculating the thermal conductivity, first, the thermal diffusivity of the target object is measured, and the thermal conductivity is calculated using the thermal diffusivity.

Thermal diffusivity was measured using a thermal diffusivity/thermal conductivity measuring device (trade name: ai-Phase Mobile 1u, iPhase Co., Ltd.).

In order to convert the above thermal diffusivity into thermal conductivity, values of density and specific heat capacity are required. A dry automatic densitometer (trade name: Accupyc 1330, manufactured by Shimadzu Corporation) was used to measure the density. The specific heat capacity was measured using a differential scanning calorimeter (trade name: DSC-60 manufactured by Shimadzu Corporation) using sapphire as a reference material with a known specific heat capacity. In this example, the specific heat capacity was measured five times, and the average value at 50°C was used. Assuming that the density and specific heat capacity are ρ and C respectively, the thermal conductivity λ can be obtained by the following equation (1) from the thermal diffusivity α obtained by the above thermal diffusivity measurement.

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 having low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed. Thereby, the heater 22 can efficiently heat the fixing belt 20 .

Further, the heater holder 23 is provided with a guide portion 26 for guiding the fixing belt 20 . The guide portions 26 are provided on the upstream side (the lower side of the heater 22 in FIG. 2) and the downstream side (the upper side of the heater 22 in FIG. 2) in the belt rotation direction of the heater 22, respectively. A plurality of guide portions 26 on the upstream side and the downstream side are arranged at intervals in the longitudinal direction of the heater 22 . Each guide portion 26 is formed in a substantially fan shape, and has an arcuate or convex curved belt facing surface 260 extending in the belt circumferential direction so as to face the inner peripheral surface of the fixing belt 20 .

The heater holder 23 has a plurality of openings 23a in the longitudinal direction. The opening 23a is an opening penetrating the heater holder 23 in the thickness direction. A thermistor 25 and a thermostat, which will be described later, are provided in the opening 23a. These thermistor 25 and thermostat are pressurized by a coil spring 29 and pressed against the rear surface of the substrate 30 . In FIG. 2, the thermistor 25 is shown as a rectangle for convenience, and the detailed configuration of the thermistor 25 will be described later.

In the fixing device 9 according to this embodiment, when the printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate. At this time, the inner peripheral surface of the fixing belt 20 is guided by the belt facing surface 260 of the guide portion 26, so that the fixing belt 20 rotates stably and smoothly. Further, the fixing belt 20 is heated by supplying electric power to the resistance heating element 31 of the heater 22 . Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), the paper P bearing the unfixed toner image is moved between the fixing belt 20 and the pressure roller 21 as shown in FIG. (fixing nip N), the unfixed toner image is heated and pressurized to be fixed on the paper P. As shown in FIG. The fixing belt 20 is a member to be heated by a heater 22 .

FIG. 3 is a plan view of the heater according to this embodiment.

As shown in FIG. 3, on the surface of the plate-shaped base material 30, there are provided a plurality (four) of resistance heating elements 31, feeder lines 33A and 33B as conductors, a first electrode portion 34A and a second electrode. A portion 34B is provided. However, the number of resistance heating elements 31 is not limited to this embodiment.

In the present embodiment, the longitudinal direction of the heater 22 and the like (the direction perpendicular to the paper surface of FIG. 2) is also the arrangement direction X of the plurality of resistance heating elements 31, as shown in FIG. Hereinafter, this direction is also simply referred to as the arrangement direction. In addition, the vertical direction Y in FIG. 3, which is a direction (vertical direction in this embodiment) that intersects the arrangement direction and is different from the thickness direction of the base material 30, is a direction that intersects the arrangement direction of the plurality of resistance heating elements 31. , or simply called the crossing direction. The array crossing direction Y is the direction along the surface of the base material 30 on which the resistance heating elements 31 are provided, and is also the lateral direction of the heater 22 or the conveying direction of the paper passing through the fixing device 9 .

A heat generating portion 35 divided into a plurality of pieces in the arrangement direction is configured by the plurality of resistance heating elements 31 . Each resistance heating element 31 is electrically connected in parallel with a pair of electrode portions 34A and 34B provided at one end portion (the left end in FIG. 3) of the substrate 30 in the arrangement direction via feeder lines 33A and 33B. It is connected to the. The power supply lines 33A and 33B are made of a conductor having a resistance value smaller than that of the resistance heating element 31. As shown in FIG. From the viewpoint of ensuring insulation between the resistance heating elements 31, the gap between the resistance heating elements 31 adjacent to each other is preferably 0.2 mm or more, more preferably 0.4 mm or more. Also, if the gap between the resistance heating elements 31 adjacent to each other is too large, the temperature at the gap is likely to drop. Therefore, from the viewpoint of suppressing temperature unevenness across the arrangement direction, the gap is preferably 5 mm or less, more preferably 1 mm or less.

The resistance heating element 31 is made of a material having a PTC (Positive Temperature Coefficient of Resistance) characteristic, and is characterized by an increase in resistance (a decrease in heater output) as the temperature rises.

Due to the fact that the resistance heating element 31 has the PTC characteristic and the configuration of the heating portions 35 divided in the arrangement direction, it is possible to prevent the temperature of the fixing belt 20 from excessively rising when small-sized paper is passed. In other words, when a sheet of paper having a width smaller than the entire width of the heating portion 35 is passed through, the heat of the fixing belt 20 is not taken away by the sheet in the area outside the width of the sheet. rises. Since the voltage applied to the resistance heating element 31 is constant, when the temperature of the resistance heating element 31 outside the paper width rises and its resistance value rises, the output (calorific value) decreases relatively and the edge temperature rises. is suppressed. In addition, by electrically connecting the plurality of resistance heating elements 31 in parallel, it is possible to suppress the temperature rise in the non-sheet passing portion while maintaining the printing speed. It should be noted that the heating element forming the heating portion 35 may be other than the resistance heating element having the PTC characteristic. Also, the resistance heating elements may be arranged in a plurality of rows in the arrangement crossing direction of the heaters 22 .

The resistance heating element 31 can be formed by, for example, applying a paste prepared by mixing silver palladium (AgPd) or glass powder to the base material 30 by screen printing or the like, and then firing the base material 30. . In this embodiment, the resistance value of the resistance heating element 31 is 80Ω at room temperature. As the material of the resistance heating element 31, in addition to the materials described above, a silver alloy (AgPt) or ruthenium oxide (RuO ₂ ) resistance material may be used. Silver (Ag) or silver palladium (AgPd) can be formed by screen printing or the like as the material of the power supply line 33 and the electrode portion 34 . The power supply line 33 is composed of a conductor having a resistance value smaller than that of the resistance heating element 31 .

As the material of the base material 30, ceramics such as alumina and aluminum nitride which are excellent in heat resistance and insulation, and non-metallic materials such as glass and mica are preferable. In this embodiment, an alumina substrate having a width of 8 mm in the crossing direction, a width of 270 mm in the direction of arrangement, and a thickness of 1.0 mm is used. Alternatively, the base material 30 may be formed by laminating an insulating material on a conductive material such as metal. As the metal material for the base material 30, aluminum, stainless steel, or the like is preferable because of its low cost. By configuring the base material 30 with a stainless steel plate, cracks due to thermal stress can be suppressed. Further, in order to improve the heat uniformity of the heater 22 and improve the image quality, the base material 30 may be made of a material having a high thermal conductivity such as copper, graphite, or graphene.

The insulating layer 32 is made of heat-resistant glass with a thickness of 75 μm, for example. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33 to insulate and protect them, and maintains slidability with the fixing belt 20 .

FIG. 4 is a diagram showing a power supply circuit to the heater according to this embodiment.

As shown in FIG. 4, in the present embodiment, a power supply circuit for supplying power to each resistance heating element 31 electrically connects an AC power source 200 and electrode portions 34A and 34B of the heater 22. It is configured. The power supply circuit is also provided with a triac 210 that controls the amount of power supplied. The controller 220 controls the amount of power supplied to each resistance heating element 31 via the triac 210 based on the temperature detected by the thermistor 25 . The control unit 220 is composed of a microcomputer including a CPU, ROM, RAM, I/O interface, and the like. The control section 220 may be provided in the fixing device 9 or may be provided in the main body of the image forming apparatus.

The fixing device 9 also has a thermostat 27 as a cutoff device. The thermostat 27 cuts off the power supply to the resistance heating element 31 when the detected temperature reaches or exceeds a predetermined temperature. Thermistor 25 and thermostat 27 contact and sense the temperature of substrate 30 .

In this embodiment, the thermistors 25 are arranged on the central side and the end side in the arrangement direction. Therefore, the power supply to the heater 22 can be controlled based on the detected temperatures of the heater 22 on the center side and the end side in the arrangement direction.

FIG. 5 is a perspective view showing a state in which the connector 60 is attached to the heater 22 and the heater holder 23. FIG.

As shown in FIG. 5, the connector 60 has a resin housing 71 and contact terminals 72 . The contact terminal 72 is a leaf spring fixed to the housing 71 . The contact terminal 72 has a pair of contact portions 72 a that come into contact with the electrode portions 34 of the heater 22 . A harness (conductor) 73 for power supply is connected to the connector 60 (contact terminal 72).

As shown in FIG. 5, the connector 60 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 72 a of the contact terminal 72 elastically contacts (presses) the electrode portion 34 of the heater 22 , whereby the heater 22 and the power source provided in the image forming apparatus are connected via the connector 60 . It is electrically connected, and power can be supplied from the power supply to the heater 22 . Further, as in the present embodiment, the connector 60 as a power supply member also functions as a clamping member that clamps and holds the heater 22 and the heater holder 23 together. It is possible to reduce the score.

In the present embodiment, the first electrode portion 34A and the second electrode portion 34B are provided on the same side in the arrangement direction (see FIG. 3), but they may be provided on different sides. Moreover, the shape of the resistance heating element 31 is not limited to that of the present embodiment. For example, as shown in FIG. 6, the resistance heating element 31 may have a rectangular shape, or as shown in FIG. It may be a configuration that forms a shape. However, by overlapping the adjacent resistance heating elements 31 in the arrangement direction as shown in FIGS. can be suppressed. Further, as shown in FIG. 6, the portion extending from the block-shaped resistance heating element 31 toward the feeder line 33 (the portion extending in the array crossing direction) may be a part of the resistance heating element 31, It may be made of the same material as the power supply line 33 .

As shown in FIG. 8 , the thermistor 25 as a temperature detection member includes a temperature detection element 251 , a leaf spring 252 , a heat-resistant film 253 , a holder 254 and lead wires 255 .

The holding member 254 has one surface to which the coil spring 29 is connected, and the other surface to which the plate spring 252 is fixed.

One end 252a and the other end 252b of the leaf spring 252 are fixed to the other side surface of the holder 254 . The leaf spring 252 also has a contact portion 252c between one end 252a and the other end 252b. The contact portion 252c is a surface substantially horizontal to the rear surface of the base material 30 (see FIG. 2). The contact portion 252 c contacts the temperature detection element 251 . A portion from the contact portion 252c of the plate spring 252 to the other end 252b, in other words, a portion extending downward in the gravitational direction from the portion contacting the temperature detection element 251 is the downward extending portion 252d.

Note that the lower side in the direction of gravity means the lower side in the direction of gravity when the heating device having the temperature detection member is attached to the apparatus main body (more specifically, when the apparatus main body is placed on a horizontal surface). on the side. In particular, the lower side in the direction of gravity referred to in the present embodiment is the lower side in the direction of gravity when the fixing device 9 is attached to the image forming apparatus. However, when a member to be detected or a specific device (for example, a heating device) to which the temperature detection member is attached is used alone, the temperature detection member is attached to the member to be detected or the specific device. In a state (more specifically, in a state in which the member to be detected or a specific device is placed on a horizontal surface), it may be the lower side in the direction of gravity.

A heat-resistant film 253 circumferentially covers the temperature detection element 251 , leaf spring 252 , and holder 254 .

The temperature detection element 251 is in contact with the back surface of the base material 30 (see FIG. 2) via the heat resistant film 253 . Thereby, the temperature detection element 251 detects the temperature of the heater 22 .

The thermistor 25 is pressurized toward the heater (right side in FIG. 8) by a coil spring 29 . The temperature detection element 251 is pressed against the back surface of the base material of the heater via the heat-resistant film 253 by the elastic force of the leaf spring 252 .

The plate spring 252 is in surface contact with the temperature detection element 251 by means of a contact portion 252c which is a substantially horizontal surface on the back surface of the base material of the heater. As a result, the leaf spring 252 can apply a uniform pressure to the entire surface of the temperature detection element 251, and the temperature detection element 251 can be stably brought into contact with the base material of the heater. However, the leaf spring 252 may indirectly contact the temperature detection element 251 . In this embodiment, a plate spring is used as the spring that abuts on the temperature detection element 251, but a coil spring, disc spring, spiral spring, or the like can also be used.

A lead 255 is connected to the temperature sensing element 251 . The temperature sensing element 251 is connected via a lead wire 255 to a controller that controls the heater 22 .

By the way, as shown in FIG. 9, a lubricating oil (liquid oil) is placed between the inner peripheral surface of the fixing belt 20 and the heater 22 in order to reduce the friction between them and allow the fixing belt 20 to rotate smoothly. or lubricant) is applied.

Then, as shown in FIG. 9, when the image forming apparatus performs a large amount of printing operations, the lubricating oil may flow to the back side of the heater 22 and reach the temperature detection element of the thermistor 25 due to its own weight. (See route D1 in FIG. 9).

10, there is a thermistor 25' in which an elastic body 259 abuts against the temperature detection element 251 instead of the plate spring of the present embodiment. The elastic body 259 is composed of fibers or sponge.

In the thermistor 25 ′ having such a configuration, when the lubricating oil reaches the thermistor 25 ′ as described above, the lubricating oil is absorbed by the elastic body 259 . If the lubricating oil stays in the vicinity of the temperature detection element 251, the heat capacity in the vicinity of the temperature detection element 251 unintentionally increases, resulting in a decrease in the responsiveness of the temperature detection element 251. As a result, the temperature control accuracy of the fixing belt 20 is lowered. As a result of this decrease in temperature control accuracy, for example, the fixing belt 20 cannot be sufficiently heated, causing problems such as toner offset, in which the toner is not sufficiently fixed on the paper, resulting in a decrease in print quality. rice field.

On the other hand, in this embodiment, as shown in FIG. It can flow further below the thermistor 25 along the extending portion 252d (see path D2). In this way, the downward extending portion 252d of the plate spring 252 forms a lubricating oil path extending downward in the gravitational direction from the temperature detecting element 251, so that the lubricating oil stays at or near the temperature detecting element 251. can be suppressed. Therefore, it is possible to suppress the influence of lubricating oil adhering to the temperature detection element 251 or its vicinity, specifically, the deterioration of the temperature detection accuracy of the thermistor 25 . In particular, when a polyimide resin is used for the substrate of the fixing belt 20 as in the present embodiment, more lubricating oil is applied between the fixing belt 20 and the heater 22 in order to suppress abrasion of the fixing belt 20 . be. Therefore, in such a fixing device, it is preferable to use the configuration of the thermistor 25 of the present embodiment to suppress the influence of the lubricating oil adhering to the temperature detecting element 251 or its vicinity. In this embodiment, all the thermistors 25 have the same configuration, but the configuration is not necessarily limited to this. That is, at least one thermistor 25 is configured to press the temperature detection element 251 toward the heater 22 by means of a plate spring 252 having a downward extending portion 252d.

Particularly in the present embodiment, the downward extending portion 252d of the leaf spring 252 is attached to the member to be detected (specifically, in the present embodiment, it is attached to the fixing device 9 and pressed against the heater 22). state), and extends in a direction away from the heater side (the heat-resistant film 253 side on the right side in the figure) as it goes downward in the direction of gravity. In other words, the gap between the heat-resistant film 253 and the plate spring 252 widens downward in the direction of gravity.

A liquid such as lubricating oil generates a staying force between the heat-resistant film 253 and the leaf spring 252 due to surface tension. However, in this embodiment, the gap between the heat-resistant film 253 and the leaf spring 252 widens toward the lower side in the direction of gravity, thereby weakening the surface tension generated in the lubricating oil between the heat-resistant film 253 and the leaf spring 252. Dropping of the lubricating oil can be promoted by the weight of the lubricating oil itself. Furthermore, when the lubricating oil begins to drop due to its own weight on the lower side, the lubricating oil above is pulled by the lubricating oil below due to intermolecular forces. That is, the lubricating oil on the upper side, which has a high surface tension, is also pulled downward by the lubricating oil on the lower side, thereby further promoting the fall of the lubricating oil. As described above, in this embodiment, the structure of the downward extending portion 252d can further suppress the retention of lubricating oil in the temperature detecting element 251 or its surroundings.

Also, as shown in FIG. 12, an intermediate member 36 may be provided between the base material 30 of the heater 22 and the thermistor 25 .

By providing the intermediate member 36 , it is possible to adjust the responsiveness of the temperature detection element 251 to the temperature rise of the heater 22 . Therefore, the operation of the thermistor 25 can be stabilized, and the temperature control of the fixing belt 20 can be stabilized.

Particularly in this embodiment, the intermediate member 36 is made of a member with high thermal conductivity (for example, a member with higher thermal conductivity than the base material 30), and a metal plate or graphite sheet is used. Thereby, the operation of the thermistor 25 can be stabilized without excessively impairing the responsiveness of the thermistor 25 .

In the thermistor 25 configured to press the temperature detecting element 251 against the heater 22 side by the leaf spring 252 as in the above-described embodiment, the pressing state between the fixing belt 20 and the pressure roller 21 continues, so that the leaf spring 252 may continue to be pressurized between the holder 254 and the substrate 30 and be plastically deformed. Due to this plastic deformation, the force of the leaf spring 252 pressing the temperature detection element 251 toward the heater 22 is weakened, and the responsiveness of the thermistor 25 is lowered.

Therefore, in the present embodiment, the mechanism for pressing the pressure roller 21 against the fixing belt 20 is provided with a pressure adjusting function. Then, when pressure contact between the pressure roller 21 and the fixing belt 20 is not required as in the fixing operation, control is performed to weaken the pressing force of the pressure roller 21 to the fixing belt 20 . The pressing force may be weakened, for example, when the fixing device or the image forming apparatus is packed for transportation or when the image forming apparatus has not been started for a long time.

Specifically, as shown in FIG. 13, the pressure mechanism 40 includes a pressure lever 41, a spring 42, a cam 43, a cam contact member 44, and the like. The direction in which the pressure roller 21 applies pressure to the fixing belt 20 is the left direction in FIG. The pressure mechanism 40 can change the pressure applied by the pressure roller 21 to the fixing belt 20 .

A spring 42 is connected to one end of the pressure lever 41 . A cam contact member 44 is provided on the other end side of the pressure lever 41 and contacts the cam 43 . The pressure lever 41 contacts the shaft portion 211 of the pressure roller 21 via the bearing 45 .

The cam 43 has a small diameter portion 43a, a medium diameter portion 43b and a large diameter portion 43c. By rotating the cam 43, the portion to be brought into contact with the cam contact member 44 is switched among the small diameter portion 43a, the medium diameter portion 43b, and the large diameter portion 43c.

During the fixing operation, the cam 43 brings the large diameter portion 43c into contact with the cam contact member 44. As shown in FIG. As a result, the pressure roller 21 is strongly pressed against the fixing belt 20 . Further, when it is desired to weaken the pressure, the cam 43 brings the middle diameter portion 43b into contact with the cam contact member 44, thereby reducing the pressure of the pressure roller 21 on the fixing belt 20. FIG. Also, the cam 43 can bring the small-diameter portion 43a into contact with the cam contact member 44 to release the pressure. The configuration of the pressure mechanism described above is an example, and a pressure mechanism capable of adjusting the pressure of the pressure roller 21 against the fixing belt 20 can be employed as appropriate.

An example of a more detailed configuration of the thermistor 25 will be described with reference to FIGS. 14 and 15. FIG.

As shown in FIGS. 14 and 15, a lead wire 255 is connected to one end of the holder 254 in the longitudinal direction (left-right direction in FIG. 14 and perpendicular to the paper surface of FIG. 2). Further, the holder 254 is provided with a leaf spring 252 and a temperature detection element 251 at a narrow portion on the longitudinal center side. Protrusions 254a are provided at both ends of the holder 254 in the longitudinal direction. The aforementioned coil spring 29 (see FIG. 8) is connected to the projection 254a. Moreover, the holder 254 has a protrusion 254b that protrudes in the opposite direction to the protrusion 254a. The protrusion 254b is a portion that engages with the recess of the heater holder 23 and is positioned on the heater holder 23 . The holder 254 is made of a resin material such as LCP (crystalline polymer) having excellent heat resistance.

The heat-resistant film 253 covers the central side of the holder 254 in the longitudinal direction, the plate spring 252 and the temperature detection element 251 . The heat-resistant film 253 is made of a resin material having good insulation, heat resistance, abrasion resistance, and thermal conductivity, such as polyimide.

Also, the number and arrangement of thermistors 25 are not limited to those shown in FIG. For example, as shown in FIG. 16, the thermistor 25 can be arranged at a position corresponding to each resistance heating element 31 in the arrangement direction. Thereby, the temperature of the region corresponding to each resistance heating element 31 can be detected, and more stable temperature control becomes possible.

In addition to the fixing device described above, the present invention can also be applied to fixing devices as shown in FIGS. 17 to 19. FIG. The configuration of each fixing device shown in FIGS. 17 to 19 will be briefly described below.

First, in the fixing device 9 shown in FIG. 17, the pressure roller 55 is arranged on the opposite side of the fixing belt 20 to the pressure roller 21 side. The pressing roller 55 is a counter rotating member that rotates facing the fixing belt 20 as a rotating member. The pressure roller 55 and the heater 22 are configured to sandwich the fixing belt 20 and heat it. On the other hand, a nip forming member 56 is arranged on the inner periphery of the fixing belt 20 on the pressure roller 21 side. The nip forming member 56 is supported by the stay 24 . A fixing nip N is formed by the nip forming member 56 and the pressure roller 21 with the fixing belt 20 interposed therebetween.

Next, in the fixing device 9 shown in FIG. 18, the pressure roller 55 described above is omitted. is formed in an arc shape. Otherwise, the configuration is the same as that of the fixing device 9 shown in FIG.

Finally, the fixing device 9 shown in FIG. 19 will be described. The fixing device 9 includes a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as a facing member. The heating assembly 92 includes the heater 22, the heater holder 23, the stay 24, the heating belt 120 as a rotating member, and the like, which have been described in the previous embodiment. The fixing roller 93 is a counter rotating member that rotates facing the heating belt 120 as a rotating member. The fixing roller 93 is composed of a solid iron core 93a, an elastic layer 93b formed on the surface of the core 93a, and a release layer 93c formed outside the elastic layer 93b. . A pressure assembly 94 is provided on the opposite side of the fixing roller 93 from the heating assembly 92 side. The pressure assembly 94 has a nip forming member 95 and a stay 96 , and a pressure belt 97 is rotatably arranged to enclose the nip forming member 95 and stay 96 . Then, the paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93 and heated and pressed to fix the image.

17 to 19, lubricating oil (liquid or lubricant) is applied between the inner surface of the fixing belt 20 (the inner surface of the heating belt 120 in the embodiment of FIG. 19) and the heater 22. . Therefore, by adopting the configuration of the thermistor 25 described above, it is possible to suppress the influence of the lubricating oil adhering to the temperature detecting element 251 or its vicinity. That is, it is possible to suppress deterioration in temperature detection accuracy of the thermistor 25 due to lubricating oil.

Further, the present invention is not limited to the fixing device as described in the above embodiments, but may also be applied to a drying device for drying ink applied to paper, and a film as a covering member that is heated on the surface of a sheet such as paper. The present invention can also be applied to a heating device such as a thermocompression bonding device such as a laminator for compression bonding and a heat sealer for thermocompression bonding of the sealed portion of the packaging material. By applying the temperature detection member of the present invention to such a device, it is possible to suppress the influence of lubricating oil adhering to the temperature detection element or its vicinity.

The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile machine, or a multi-function machine of these.

For example, as shown in FIG. 20, the image forming apparatus 100 of this embodiment includes an image forming unit 50 including a photosensitive drum and the like, a sheet conveying section including a pair of timing rollers 15 and the like, a sheet feeding device 7, a fixing A device 9 , a paper ejection device 10 , and a reading unit 51 are provided. The paper feed device 7 has a plurality of paper feed trays, and each paper feed tray accommodates sheets of different sizes.

The reading unit 51 reads the image of the document Q. As shown in FIG. The reading unit 51 generates image data from the read image. The paper feeder 7 accommodates a plurality of papers P and sends out the papers P to the transport path. The timing roller 15 conveys the paper P on the conveying path to the image forming means 50 .

The image forming means 50 forms a toner image on the paper P. As shown in FIG. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a neutralizing device. The toner image indicates the image of the document Q, for example. The fixing device 9 fixes the toner image on the paper P by heating and pressing the toner image. The paper P on which the toner image is fixed is conveyed to the paper discharge device 10 by a conveying roller or the like. The paper discharge device 10 discharges the paper P to the outside of the image forming apparatus 100 .

Next, the fixing device 9 of this embodiment will be described. The description of the configuration common to the fixing device of the above embodiment will be omitted as appropriate.

As shown in FIG. 21, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, and the like.

A fixing nip N is formed between the fixing belt 20 and the pressure roller 21 . The fixing nip N has a nip width of 10 mm, and the linear speed of the fixing device 9 is 240 mm/s.

The fixing belt 20 has a polyimide substrate and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material made of, for example, fluororesin. The fixing belt 20 has an outer diameter of about 24 mm.

The pressure roller 21 includes a metal core 21a, an elastic layer 21b, and a release layer 21c. The pressure roller 21 has an outer diameter of 24 to 30 mm, and the elastic layer 21b has a thickness of 3 to 4 mm.

The heater 22 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element and the like, and an insulating layer, and has a total thickness of 1 mm. Moreover, the width Y of the heater 22 in the array crossing direction is 13 mm.

As shown in FIG. 22, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, power supply lines 33, and electrode portions 34A-34C. Also in this embodiment, as shown in the enlarged view of FIG. 22, divided regions B are formed by dividing a plurality of resistance heating elements 31 in the arrangement direction (however, in FIG. Although B is shown in the figure, divided regions are actually provided between all the resistance heating elements 31). The resistance heating element 31 constitutes three heating portions 35A to 35C. By energizing the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By energizing the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, the heat-generating portion 35B can be caused to generate heat when performing the fixing operation on small-sized paper, and all the heat-generating portions can generate heat when performing the fixing operation on large-sized paper.

As shown in FIG. 23, the heater holder 23 holds the heater 22 in its recess 23b. The recess 23 b is provided on the heater holder 23 on the heater 22 side. The concave portion 23b is provided inside the heater holder 23 on both sides (or one side) in the arrangement direction of the heater holder 23, and a surface 23b1 that is concave on the stay 24 side from the other surface of the heater 22 and is substantially parallel to the base material 30. and wall portions 23b3 provided inside the heater holder 23 on both sides in the arrangement cross direction. The heater holder 23 has a guide portion 26 . The heater holder 23 is made of LCP (liquid crystal polymer).

As shown in FIG. 24, the connector 60 includes a housing made of resin (for example, LCP) and a plurality of contact terminals provided in the housing.

The connector 60 is attached so as to sandwich the heater 22 and the heater holder 23 together from the front side and the back side. In this state, each contact terminal is brought into contact (pressure contact) with each electrode portion of the heater 22 , thereby electrically connecting the heat generating portion 35 and the power supply provided in the image forming apparatus through the connector 60 . As a result, power can be supplied from the power supply to the heating unit 35 . At least a portion of each electrode portion 34 is exposed without being covered with an insulating layer in order to ensure connection with the connector 60 .

The flanges 53 are provided on both sides in the alignment direction of the fixing belt 20 and hold both ends of the fixing belt 20 from the inside of the belt. The flange 53 is fixed to the housing of the fixing device 9 . The flanges 53 are inserted into both ends of the stay 24 (see arrow directions from the flanges 53 in FIG. 24).

The direction in which the connector 60 is attached to the heater 22 and the heater holder 23 is the heater array intersecting direction (see the arrow direction from the connector 60 in FIG. 24). When the connector 60 is attached to the heater holder 23, the protrusion provided on one of the connector 60 and the heater holder 23 may be engaged with the recess provided on the other so that the protrusion relatively moves within the recess. The connector 60 is attached to the heater 22 and the heater holder 23 on one side in the arrangement direction, which is opposite to the side on which the drive motor of the pressure roller 21 is provided.

As shown in FIG. 25 , thermistors 25 are provided on the inner peripheral surface of the fixing belt 20 and on the center side and the end side of the fixing belt 20 in the alignment direction. The heater 22 is controlled based on the temperatures detected by the thermistor 25 at the central side and the end side of the fixing belt 20 in the arrangement direction. One of these thermistors 25 is provided at a position corresponding to the divided area between the resistance heating elements of the heater 22, as in the above-described embodiment.

Thermostats 27 are provided on the center side and the end side of the fixing belt 20 in the arrangement direction so as to face the inner peripheral surface of the fixing belt 20 . When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold value, power supply to the heater 22 is stopped.

Flanges 53 that hold the ends of the fixing belt 20 are provided at both ends of the fixing belt 20 in the arrangement direction. The flange 53 is made of LCP (liquid crystal polymer).

As shown in FIG. 26, the flange 53 is provided with a slide groove 53a. The slide groove 53 a extends in the contact/separation direction of the fixing belt 20 with respect to the pressure roller 21 . An engaging portion of the housing of the fixing device 9 is engaged with the slide groove 53a. The fixing belt 20 can move toward and away from the pressure roller 21 by relatively moving the engaging portion within the slide groove 53a.

Lubricating oil (liquid or lubricant) is applied between the inner surface of the fixing belt 20 and the heater 22 in the fixing device 9 as well. Therefore, by adopting the configuration of the thermistor 25 described above, it is possible to suppress the lubricating oil from adhering to and remaining on the temperature detecting element 251 or its vicinity. Therefore, adverse effects due to adhesion of lubricating oil, specifically, deterioration in temperature detection accuracy of the thermistor 25 can be suppressed.

As a recording medium, in addition to paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, plastic film, prepreg, copper foil, etc. included.

In the above embodiments, the case where the present invention is applied to the thermistor as a temperature detection member was exemplified. may be applied as the temperature detection member of the present invention.

1 image forming apparatus 9 fixing device (heating device)
20 fixing belt (rotating member or fixing member)
21 pressure roller (counter-rotating member or pressure member)
22 heater (heating member or member to be detected)
23 heater holder (holding member)
24 stay (supporting member)
25 thermistor (temperature detection member)
251 temperature detection element 252 leaf spring (spring)
252c contact portion 252d downward extension portion 253 heat-resistant film 254 holder 27 thermostat (temperature detection member)
30 Base material 31 Resistance heating element 35 Heat generating part 40 Pressure mechanism 220 Control part B Divided area N Fixing nip (nip part)
X array direction of multiple resistance heating elements Y array cross direction

Japanese Patent Application Laid-Open No. 2020-91271

Claims (11)

a temperature sensing element;
A temperature sensing member comprising a spring,
the spring abuts against the temperature detection element and presses the temperature detection element toward the member to be detected;
The temperature detection member, wherein the spring has a downward extension portion extending downward in the direction of gravity from a contact portion that contacts the temperature detection element when attached to the member to be detected. 2. The temperature sensing member according to claim 1, further comprising an intermediate member arranged between said temperature sensing element and said spring. 3. The temperature sensing member according to claim 2, wherein said intermediate member is a metal plate or a graphite sheet. 4. The downward extending portion, in a state of being attached to the member to be detected, extends in a direction away from the member to be detected as it goes downward in the direction of gravity. temperature sensing member. The temperature sensing member according to any one of claims 1 to 4, wherein the spring is a leaf spring. A temperature sensing member according to any one of claims 1 to 5;
a rotating member;
and a heating member that is the member to be detected. 7. The heating device according to claim 6, comprising a plurality of the temperature detection members,
The heating member has a substrate and a plurality of resistance heating elements,
The resistance heating element is divided into a plurality of parts and arranged on the base material,
A heating device in which the temperature detection members are arranged at positions corresponding to the respective resistance heating elements in the arrangement direction of the plurality of resistance heating elements. 8. The heating device according to claim 6, wherein the inner surface of the rotating member abuts against the heating member, and the inner surface of the rotating member is made of polyimide resin. a counter rotating member that rotates in contact with the rotating member;
9. The heating device according to any one of claims 6 to 8, further comprising a pressurizing mechanism that pressurizes the counter rotating member and presses the counter rotating member against the rotating member,
A heating device capable of changing the pressing force of the opposing rotating member to the rotating member by varying the pressing force of the pressing mechanism. A fixing device that heats and fixes toner on a recording medium with the heating device according to any one of claims 6 to 9. An image forming apparatus comprising the fixing device according to claim 10 .

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