Heater, fixing device, and image forming apparatus

Abstract

To solve the problem in which: Ag that is the component of a conductor for energizing a thermistor may be ionized and dissolve due to the influence of water around a heater; a phenomenon called migration may occur in which an electric field between conductors causes ions to move, thereby causing a short circuit between the conductors.SOLUTION: In a longitudinal direction of a heater, the distance from the center part of the heater to a first temperature detection element is a first distance, and the distance from the center part of the heater to a second temperature detection element is a second distance longer than the first distance. In a first area at a longer distance from the center part of the heater than the second temperature detection element in the longitudinal direction of the heater, the distance between a first conductor and a second conductor in a short direction of the heater is a first inter-conductor distance, and the distance between a third conductor and a fourth conductor is a second inter-conductor distance longer than the first inter-conductor distance.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a heater, and more particularly to a heater used in an image forming apparatus such as a copying machine or a laser printer. [Background technology]

[0002] Conventionally, in image forming devices such as electrophotographic copiers and laser beam printers, unfixed images formed on recording materials are fixed by applying heat and pressure using a fixing device equipped with a heater. A film heating method has been proposed and put into practical use as a heating method for fixing devices. In the film heating method, a heat-resistant thin film is slidably conveyed by a pressure roller. The image is fixed to the recording material by applying heat and pressure to the recording material carrying the unfixed image in the nip formed by the heater and pressure roller sandwiching the fixing film.

[0003] Film-heating fixing devices can be constructed entirely from low-heat-capacity materials, enabling power savings and shorter wait times (quick start). For example, the heater has a substrate based on a low-heat-capacity plate-shaped ceramic substrate, such as alumina (Al2O3) or aluminum nitride (AlN). A heating element made of silver-palladium (Ag / Pd) or ruthenium oxide (RuO2), and electrodes made of low-resistance materials such as Ag for conducting electricity to the heating element, are formed on one side of the substrate by screen printing or other methods. The surface on which the heating element is formed is then covered with a thin glass protective layer.

[0004] Furthermore, a thermistor made of a material with a resistance-temperature characteristic whose resistance value changes with temperature is disposed on the side of the substrate opposite the heating element-forming surface. A conductor made of a low-resistance material such as Ag is then formed to energize the thermistor. Proposed thermistors include those in which a chip-type thermistor element is adhesively disposed, as shown in Patent Document 1, and those formed by pattern-printing a paste-type thermistor material, as shown in Patent Document 2.

[0005] The heater generates heat when electricity is applied to the heating element via electrodes. The temperature rise of the heater is detected by a thermistor and fed back to the control unit. The control unit controls the electricity so that the heater temperature detected by the thermistor reaches a target temperature. As shown in Patent Document 3, a configuration has been proposed in which multiple thermistors are placed on the heater to detect the temperature distribution of the heater. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 6-186870 [Patent Document 2] Patent Publication No. 8-297431 [Patent Document 3] Patent Publication No. 2018-194686 Summary of the Invention [Problem to be solved by the invention]

[0007] However, Ag, which is a constituent material of the conductor that conducts current to the thermistor, can become ionized and dissolve due to the influence of moisture around the heater. When the ions move due to the electric field between the conductors, there is a risk of a phenomenon called migration occurring, which can cause a short circuit between the conductors.

[0008] The present invention has been made in view of the above circumstances, and aims to suppress the occurrence of migration. [Means for solving the problem]

[0009] In order to achieve the above object, a thin and long substrate is provided, comprising: a heating element disposed on a first surface of the substrate; a first temperature detection element disposed on a second surface behind the first surface of the substrate; a second temperature detection element disposed on the second surface; a first conductor disposed on the second surface for connecting the first temperature detection element to a first power supply terminal; a second conductor disposed on the second surface for connecting the first temperature detection element to a first ground terminal; a third conductor disposed on the second surface for connecting the second temperature detection element to a second power supply terminal; and a third conductor disposed on the second surface for connecting the second temperature detection element to a second ground terminal. a fourth conductor for detecting a temperature difference between the first and second conductors, wherein in a longitudinal direction of the heater, a distance from a center of the heater to the first temperature detection element is a first distance, a distance from the center of the heater to the second temperature detection element is a second distance longer than the first distance, and in a first region in the longitudinal direction of the heater that is further away from the center of the heater than the second temperature detection element, a distance between the first conductor and the second conductor in a short direction of the heater is a first inter-conductor distance, and a distance between the third conductor and the fourth conductor is a second inter-conductor distance longer than the first inter-conductor distance. In a second region that is farther from the center of the heater than the first region, the distance between the first conductor and the second conductor in the short-side direction of the heater is a third inter-conductor distance, and the distance between the third conductor and the fourth conductor is the third inter-conductor distance. It is characterized by the following. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress the occurrence of migration. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic diagram of a laser printer 100 [Figure 2] Cross-sectional view of fixing device 200 [Figure 3] Schematic diagram of heater 210 [Figure 4] Schematic diagram of the heater drive circuit 400 [Figure 5] 1 is a diagram showing the temperature distribution in the longitudinal direction of the heater 210. [Figure 6] Schematic diagram of heater 310 [Figure 7] Schematic diagram of heater 320 [Figure 8] Schematic diagram of heater 330 [Figure 9] Schematic diagram of heater 340 [Figure 10] Schematic diagram of heater 350 DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present invention with reference to the drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0013] (First embodiment) [Image forming device] FIG. 1 is a schematic diagram of a laser printer 100 serving as an image forming apparatus. Based on information received from an external device (not shown), such as a host computer, the video controller of the laser printer 100 performs processes such as bitmapping character codes and halftoning using dithering of halftone images. It then transmits a print signal and image information to the engine control unit. Upon receiving the image information from the video controller, the engine control unit irradiates a laser beam from a scanner unit 21 in accordance with the image information, scanning a photosensitive drum 19, which serves as a photosensitive member charged to a predetermined polarity by a charging roller 16. This forms an electrostatic latent image on the photosensitive drum 19. Toner is supplied from a developing unit 17 to the formed electrostatic latent image, forming an image on the photosensitive drum 19.

[0014] Recording material P, such as paper, loaded in a paper feed cassette 11 is fed one sheet at a time by a pickup roller 12 and conveyed by a conveying roller 13 toward a registration roller 14. The recording material P is conveyed from the registration roller 14 to a transfer section in accordance with the timing at which the image formed on the photosensitive drum 19 reaches a transfer section formed by the photosensitive drum 19 and a transfer roller 20. When the recording material P passes through the transfer section, a transfer bias is applied to the transfer roller 20, so that the image on the photosensitive drum 19 is transferred to the recording material P.

[0015] The recording material P onto which the image has been transferred is heated and fixed in a fixing device 200, thereby fixing the image to the recording material P. A control unit 40 controls the supply of power from a commercial AC power source 41 to the fixing device 200. The recording material P with the fixed image is discharged onto a paper discharge tray at the top of the laser printer 100 by a transport roller 26 and a paper discharge roller 27. Toner remaining on the photosensitive drum 19 is cleaned by a cleaner 18. The photosensitive drum 19, charging roller 16, scanner unit 21, developing device 17, and transfer roller 20 described above constitute an image forming unit that forms an image. The charging roller 16, developing device 17, cleaner 18, and photosensitive drum 19 are configured as a cartridge 15.

[0016] [Fusing device] 2 is a cross-sectional view of fixing device 200. Fixing device 200 has the following configuration: a thin heater 210, a heater holder 220, and a cylindrical film 230 that moves while making sliding contact with heater 210. It also has a pressure roller 260 that forms a nip N with heater 210 via film 230, and a pressure mechanism 250 that presses pressure stay 240 toward pressure roller 260.

[0017] Heater 210 is disposed in the internal space of film 230, and film 230 is sandwiched between heater 210 and pressure roller 260. Heater 210 has a substrate based on a plate-shaped ceramic member made of alumina (Al2O3), aluminum nitride (AlN), or the like, or a metal such as stainless steel. Heating element 212 is formed on one surface of the substrate, and multiple thermistors are disposed on the other surface as temperature detection elements for detecting the temperature of heater 210. The detailed configuration of heater 210 will be described later using FIG. 3. Heater 210 is supported on the seat of heater holder 220 made of heat-resistant resin such as liquid crystal polymer.

[0018] Film 230 is based on a heat-resistant resin such as polyimide or a metal such as stainless steel, and has an elastic layer such as heat-resistant rubber and a release layer made of heat-resistant resin on the base. Pressure roller 260 has a core metal 261 made of a material such as iron or aluminum, and an elastic layer 262 made of a material such as silicone rubber, and receives a driving force from motor M to rotate in the direction of the arrow.

[0019] The pressure stay 240 is a thick member made of a rigid material such as metal, and is positioned so as to abut against the surface of the heater holder 220 opposite the heater support surface, and applies pressure to the pressure roller 290 side to form a nip portion N.

[0020] The pressure mechanism 250 has a fixing frame 201, a pressure spring 202, and a pressure plate 203, and applies the pressure force of the pressure spring 202 held by the fixing frame 201 to both longitudinal ends of the pressure stay 240 via the pressure plate 203. The applied pressure force is transmitted to the pressure roller 260 side via the contact portion with the heater holder 220, thereby forming a nip portion N.

[0021] [heater] 3 is a schematic diagram showing the configuration of the heater 210. The direction of the long side of the elongated heater 210 is also referred to as the longitudinal direction (the left-right direction in FIG. 3), the direction of the short side of the heater 210 perpendicular to the longitudinal direction is also referred to as the lateral direction (the up-down direction in FIG. 3), and the thickness direction of the heater 210 perpendicular to the longitudinal and lateral directions is also referred to as the thickness direction (the front-to-rear direction in FIG. 3).

[0022] 3(a) shows a plan view of the first surface on which the heating element of the heater 210 is formed. On a substrate 211, a resistive heating element layer 212 (hereinafter also referred to as the heating element) that generates heat when current is passed through it in the longitudinal direction of the heater 210, electrodes 213 for passing current through the heating element 212, and a protective layer 214 for insulating and protecting the heating element 212 are formed.

[0023] 3(b) shows a plan view of the second surface of heater 210, which is the surface opposite to the first surface on which the heating element is formed. A thermistor is formed on the second surface. Thermistors 215 and 216, each having a negative resistance-temperature characteristic, are arranged on substrate 211. In this example, thermistors used are those formed by pattern printing a paste-like thermistor material, but this is not limiting and chip-like thermistor elements may also be adhesively arranged.

[0024] The thermistor 215 is used for control to maintain the heater 210 at a target temperature. The thermistor 215 is disposed near the center of the heater 210 in the longitudinal direction (at a position a distance L1 from a dotted line C that passes through the center of the heater 210 in the longitudinal direction). On the substrate 211, a conductive layer 215T serving as a first conductor for feeding power to the thermistor 215 and a conductive layer 215G serving as a second conductor for grounding the thermistor 215 are formed. The conductive layer 215T is connected to a power feeding terminal ET1, and the conductive layer 215G is connected to a ground terminal EG1.

[0025] In this embodiment, the conductive layer 215T, the conductive layer 215G, the power supply terminal ET1, the ground terminal EG1, and the areas between these conductors are uncoated and exposed, allowing for the presence of moisture around the heater 210. The conductive layer 215T and the conductive layer 215G are formed near the power supply terminal ET1 and the ground terminal EG1 with an inter-conductor distance S1. The power supply terminal ET1 and the ground terminal EG1 are connected to a heater drive circuit 400 (described later) by a connector (not shown in the figure, which is a pressure-displacement type connector in this embodiment). The conductive layer 215G and the ground terminal EG1 are grounded via the heater drive circuit 400.

[0026] The thermistor 216 is used to detect excessive temperature rise that may occur at the longitudinal end of the heater 210 when fixing a recording material P whose longitudinal length is shorter than that of the heating element 212, and to detect a temperature drop at the end after printing. The thermistor 216 is disposed near the longitudinal end of the heater 210 (at a position a distance L2 from a dotted line C that passes through the longitudinal center of the heater 210). On the substrate 211, there are provided a conductive layer 216T as a third conductor for supplying power to the thermistor 216, and a grounding layer 216A for grounding the thermistor 216. Fourth Conductor The conductive layer 216T is connected to the power supply terminal ET2, and the conductive layer 216G is connected to the ground terminal EG2.

[0027] In this embodiment, the conductive layer 216T, the conductive layer 216G, the power supply terminal ET2, the ground terminal EG2, and the areas between these conductors are uncoated and exposed, allowing for the presence of moisture around the heater 210. The conductive layer 216T and the conductive layer 216G are formed near the power supply terminal ET2 and the ground terminal EG2 with an inter-conductor distance S2. The power supply terminal ET2 and the ground terminal EG2 are connected to a heater drive circuit 400 (described later) by a connector (not shown in the figure, which is a pressure-displacement type connector in this embodiment). The conductive layer 216G and the ground terminal EG2 are grounded via the heater drive circuit 400.

[0028] In this embodiment, the relationship between distance L1 and distance L2 is L2>L1. In this case, the relationship between inter-conductor distance S1 and inter-conductor distance S2 is S2>S1. That is, in the longitudinal direction of heater 210, inter-conductor distance S2 in the thermistor 216 arranged near the end is made larger than inter-conductor distance S1 in the thermistor 215 arranged near the center. The reason for this will be described in detail later. Note that the inter-conductor distance here is the distance in a first region closer to the end than the thermistor 216.

[0029] 4 shows a heater drive circuit 400 for controlling the power supply to the heater 210. The thermistor 215 is connected in series with a pull-up resistor 403 in the heater drive circuit 400, and a DC Vcc voltage is applied to the thermistor 215. Voltage division information corresponding to the temperature of the thermistor 215 is input to a CPU 401 as a Th1 signal and converted into temperature information for the thermistor 215. The CPU 401 controls the amount of power supplied to the heater 210 by switching the ON / OFF timing of a triac 402 based on the temperature information from the thermistor 215, thereby controlling the temperature of the heater 210 based on a target temperature. Note that in this embodiment, control is performed by so-called phase control, in which current is supplied at a timing corresponding to a predetermined phase angle from the zero crossing of the AC voltage waveform.

[0030] Similarly, the thermistor 216 is connected in series with a pull-up resistor 404 in the heater drive circuit 400, and a DC Vcc voltage is applied to it. Voltage division information according to the temperature of the thermistor 216 is input to the CPU 401 as a Th2 signal and converted into temperature information of the thermistor 216. As described above, the thermistor 216 detects the temperature near the longitudinal end of the heater 210.

[0031] FIG. 5 shows an example of a diagram illustrating temperature distribution in the longitudinal direction of the heater 210 when the heater driving circuit 400 supplies power to the heater 210 to heat it, and when heating is stopped.

[0032] The temperature distribution indicated by the solid line in Fig. 5 is the temperature distribution of heater 210 during a period in which heater 210 is controlled to maintain a predetermined target temperature based on the temperature detected by thermistor 215. While power is supplied to heater 210 to heat it, the amount of heat generated by heater 210 is greater than the amount of heat dissipated by the entire fixing device 200. Therefore, the region where heating element 212 is formed maintains a temperature range close to the temperature of thermistor 215, while the temperature of regions near both longitudinal ends where heating element 212 is not formed drops due to heat dissipation to the ambient temperature. However, when the fixing temperature is 200°C or higher, the temperature distribution exceeds the water vapor liquefaction threshold (100°C, dashed line in Fig. 5), including both ends where the temperature drops.

[0033] 5 is the temperature distribution of heater 210 during the period when heating is stopped. When heating is stopped, heat generation from heater 210 ceases, and more heat is dissipated from fixing device 200. Because the heat dissipation rate is higher near the ends of heater 210 than near the center in the longitudinal direction, the temperature of heater 210 has a parabolic temperature distribution in which the temperature difference gradually widens from the center to both ends in the longitudinal direction.

[0034] As the temperature of heater 210 decreases, a region Rw (shaded region in FIG. 5 ) where the temperature falls below the water vapor liquefaction threshold is generated at the longitudinal end of heater 210. That is, near the terminals of conductive layers 215T, 215G, 216T, and 216G on the thermistor-forming surface of heater 210, water vapor present around fixing device 200 begins to liquefy as water vapor. A DC voltage is applied to the thermistors 215 and 216 from the heater drive circuit. That is, a potential difference exists between conductive layers 215T and 215G (hereinafter also referred to as between thermistors 215T and 215G) and between conductive layers 216T and 216G (hereinafter also referred to as between thermistors 216T and 216G). As a result, Ag forming the conductive layers ionizes and dissolves in the liquefied water, and the Ag begins to be attracted to the opposite polarity, i.e., migration begins.

[0035] At this time, different potential differences are applied between thermistors 215T-G and between thermistors 216T-G due to the temperature distribution described above. The thermistors in this embodiment have negative temperature resistance characteristics. Therefore, in the above-described temperature distribution, i.e., the parabolic temperature distribution, the resistance of thermistor 216, which is located near the longitudinal end and has a lower temperature (temperature T2), is greater than the resistance of thermistor 215, which is located near the longitudinal center and has a higher temperature (temperature T1). When the thermistor resistance is high, the potential difference between the conductors sandwiching the thermistor increases, so the potential difference V2 between thermistors 216T-G is greater than the potential difference V1 between thermistors 215T-G. Since the rate at which migration occurs is generally proportional to the potential difference, migration occurs more easily between thermistors 216T-G than between thermistors 215T-G.

[0036] On the other hand, the distance between thermistors 216T-G (inter-conductor distance S2) is greater than the distance between thermistors 215T-G (inter-conductor distance S1). Since the rate at which migration progresses is generally inversely proportional to the inter-conductor distance, in terms of the inter-conductor distance, migration is more difficult to progress between thermistors 216T-G than between thermistors 215T-G.

[0037] In other words, considering both the potential difference and the inter-conductor distance, the migration rate between thermistors 215T-G is reversed from that between thermistors 216T-G. This makes it possible to make the migration rate of the thermistor 216 disposed at the longitudinal end of heater 210 and the migration rate of the thermistor 215 disposed at the longitudinal center of heater 210 comparable. More preferably, the ratio S2 / S1 of the inter-conductor distance S2 to the inter-conductor distance S1 is adjusted to match the ratio V2 / V1 of the potential difference V2 applied to thermistor 216 to the potential difference V1 applied to thermistor 215 while heating is stopped. This makes it possible to match the migration rate between thermistors 215T-G and between thermistors 216T-G.

[0038] It should be noted that larger inter-conductor distances S1 and S2 are advantageous for suppressing the migration phenomenon. However, a larger inter-conductor distance leads to an increase in the size of the substrate, and ultimately to an increase in the size of heater 210 and fixing device 200. As described in this embodiment, by adjusting inter-conductor distances S1 and S2 according to the ratio of the potential difference applied to thermistor 215 and thermistor 216, it is possible to suppress the occurrence of the migration phenomenon while also suppressing an increase in size.

[0039] Next, as a comparative example, a case will be described in which the conductor-to-conductor distance S2 of thermistor 216 is the same as the conductor-to-conductor distance S1 of thermistor 215. In the comparative example, the temperature distribution in the longitudinal direction of heater 210 is the same as in this embodiment. Water vapor present around fixing device 200 begins to liquefy and become present near the longitudinal end of heater 210 after heating is stopped. As in this embodiment, the potential difference V2 across thermistor 216 is greater than the potential difference V1 across thermistor 215. In this situation, when the conductor-to-conductor distance S2 is equal to the conductor-to-conductor distance S1, the rate of migration between thermistors 216T-G becomes faster than the rate of migration between thermistors 215T-G.

[0040] Table 1 shows an example in which a heating and cooling cycle test was performed on the fixing device 200 in a high-temperature, high-humidity environment, and the total power-on time until migration affected the temperature detected by the thermistor was compared between this embodiment and a comparative example.

[0041] [Table 1]

[0042] For example, if the expected lifespan of the fixing device 200 that satisfies the quality requirements is 300 hours as the total power-on time, then in the comparative example, as shown in Table 1, the effects of migration appear relatively soon after the expected lifespan is exceeded. On the other hand, in the present embodiment, the time until the effects of migration appear is relatively longer than in the comparative example, and it can be seen that the occurrence of migration is suppressed. In other words, it can be said that defects caused by migration in the fixing device 200 are suppressed, and the usable period of the fixing device 200 can be extended.

[0043] In this embodiment, as an example, a configuration has been described in which two thermistors are arranged in the heater 210, and one thermistor is connected to one grounded conductive layer. However, the configuration is not limited to this, and may be as shown in Fig. 6. In other words, three or more thermistors may be arranged in the heater 310, and two or more thermistors may be connected to a grounded conductive layer.

[0044] 6 is a schematic diagram showing a heater 310 that is a modification of this embodiment. Thermistor 315 is disposed at a distance L1 from a dotted line C that passes through the center of the heater 310 in the longitudinal direction. Thermistor 316 is disposed at a distance L2 from the dotted line C that passes through the center of the heater 310 in the longitudinal direction. Thermistor 317 is disposed at a distance L3 from the dotted line C that passes through the center of the heater 310 in the longitudinal direction. Thermistor 318 is disposed at a distance L4 from the dotted line C that passes through the center of the heater 310 in the longitudinal direction.

[0045] Thermistors 315 and 316 are connected to the conductor layer 315G connected to the ground terminals EG1 and EG2. Also, thermistors 317 and 318 are connected to the conductor layer 317G connected to the ground terminals EG3 and EG4. Further, thermistor 315 is connected to the conductor layer 315T connected to the power supply terminal ET1. Thermistor 316 is connected to the conductor layer 316T connected to the power supply terminal ET2. Thermistor 317 is connected to the conductor layer 317T connected to the power supply terminal ET3. Thermistor 318 is connected to the conductor layer 318T connected to the power supply terminal ET4. The conduction spacing of thermistor 315 is S1, the conduction spacing of thermistor 316 is S2, the conduction spacing of thermistor 317 is S3, Thermistor 318 and the conduction spacing of

[0046] The relationship between each thermistor and the distance from the central part in the longitudinal direction of the heater 310 is L1 < L2 < L3 < L4. In contrast, the conduction spacing between the conductors of each thermistor is S1 < S2 < S3 < S4. Thereby, it becomes possible to keep the migration progress speed of each of the thermistors 315, 316, 317, 318 within the same range.

[0047] In this way, by setting the conduction spacing of the conductor connected to the thermistor according to the distance from the central part in the longitudinal direction of the heater to the thermistor, the occurrence of migration can be suppressed.

[0048] (Second Embodiment) In this embodiment, a configuration in which a part of the conductor layer connected to the thermistor is covered with a protection member will be described. Regarding the same configurations as those in the previous first embodiment such as an image forming apparatus, detailed descriptions here will be omitted.

[0049] <00所の距離に応じて、サーミスタに接続される導体の導電間距離を設定することで、マイグレーションの発生を抑制することができる。

[0048] (第2の実施形態) 本実施形態においては、サーミスタに接続される導電体層の一部を保護部材で被覆している構成について説明する。なお、画像形成装置など先の第1の実施形態の同様の構成については、ここでの詳しい説明は省略する。

[0049] 図7は、本実施形態におけるヒータ320を示す概略構成図である。なお、ヒータ320に形成される複数のサーミスタの配置は、先の第1の実施形態の図6で説明したヒータ310と同様である。 It seems there are some parts in the original text that might be incomplete or have some encoding issues in the tags. The translation is done as accurately as possible based on the provided text. If you have any further clarifications or corrections regarding the original text, please let me know.

[0050] An FPC (Flexible Printed Circuits), which is a terminal connection connector and a protective member for protecting the conductor layer, is joined to an end portion in the longitudinal direction of the heater 320. The protective member joined to one end portion is designated as FPC1, and the protective member connected to the other end portion is designated as FPC2. Here, the intervals between the power supply terminals ET1 to ET4 and the ground terminals EG1 to EG4, which are arranged at the end portions in the longitudinal direction of the heater 320, are equal to each other. And they overlap with the wire connection portions in the protective members FPC1 and FPC2 and are configured to be covered.

[0051] The FPC, which is the protective member in the present embodiment, has a structure in which a copper foil pattern as a wire is sandwiched between polyimide films via an adhesive layer, and the wire connection portion has the copper foil pattern exposed. The wire connection portion of the FPC is connected to the power supply terminals ET1 to ET4 and the ground terminals EG1 to EG4 of the heater 320 by soldering or the like. At this time, in the overlapping portions of FPC1, FPC2 and the heater 320, portions other than the solder joint portions are filled with an insulating rosin resin-based flux. Thereby, the end region in the longitudinal direction of the heater 320 including the conductor layer is sealed, and it functions as a protective member against water vapor around the heater 320. And the conductor-to-conductor distances in the region covered by the protective member are arranged such that S1 = S2 = S3 = S4. The region covered by this protective member can be said to be a second region on the end side from the previous first region.

[0052] In the end region in the longitudinal direction of the heater 320, in the region where the protective member is not formed, the conductor-to-conductor distances S1 to S4 are set in the same manner as in the previous first embodiment. That is, the conductor-to-conductor distances S1 to S4 are made different according to the distances L1 to L4 from the central portion of the heater 320 of each of the thermistors 325, 326, 327, 328. Similar to the first embodiment, according to the distances L1 < L2 < L3 < L4, the conductor-to-conductor distances S1 < S2 < S3 < S4 are made to be such.

[0053] In this way, when a protective member is formed on the longitudinal end of the heater 320, the area where the protective member is formed is less likely to experience liquefied moisture around the conductive layer even after heating by the fixing device is stopped, making migration less likely to occur. On the other hand, in areas where the protective member is not formed, liquefied moisture begins to intervene between the conductive layers when the temperature falls below the water vapor liquefaction threshold, and migration may occur due to the potential difference across the thermistor. Therefore, in exposed areas where no protective member is formed, migration can be suppressed by setting the inter-conductor distance of the conductors connected to the thermistor according to the distance from the center of the heater in the longitudinal direction to the thermistor.

[0054] (Third embodiment) In this embodiment, a configuration in which multiple types of protective members are used to cover the entire area of ​​the conductor layer connected to the thermistor will be described. Note that detailed descriptions of the same configurations as those in the first and second embodiments will be omitted here.

[0055] Fig. 8 is a schematic diagram showing the configuration of a heater 330 in this embodiment. As shown in Fig. 8(a), the arrangement of the multiple thermistors formed in the heater 330 is similar to that of the heater 320 described in Fig. 7 of the second embodiment. Also, the configuration in which FPC1 and FPC2 are bonded as protective members to the longitudinal ends of the heater 330 is similar to that in Fig. 7.

[0056] In this embodiment, as shown in Fig. 8(b), a thermally conductive glass member 332 is formed as a second protective member to cover the area where the first protective members, FPC1 and FPC2, are not formed, so that no conductive layer is exposed. If there is a difference in the sealing ability between the first protective members, FPC1 and FPC2, and the second protective member, thermally conductive glass member 332, the inter-conductor distances S1 to S4 of the conductive layers formed in the area where the protective member with the lower sealing ability is formed are set according to the distance from the center of the heater 330 in the longitudinal direction to the thermistor. In this embodiment, the sealing ability of the first protective member and the second protective member was confirmed by the following preliminary verification.

[0057] [Pre-verification] A heating and cooling cycle test is performed on the fixing device 200 equipped with the heater 330, and after 500 hours of energized heating, the heater 330 is removed from the fixing device 200. Then, the penetration state of the penetrant liquid into the interfaces between the substrate 331 of the heater 330 and each protective member is confirmed by the test method described below, which conforms to JIS Z2343 penetrant testing. Penetrant: High-sensitivity, water-washable fluorescent penetrant Neoglow F-4A-E Plus (manufactured by Eishinkagakusha) Penetration time: 24 hours ·Ultraviolet light: UV-LED Light ZB-365J (manufactured by Eiken Gakusha) The test is terminated if penetration of the penetrant into any of the protective materials is confirmed. If not, the test is repeated.

[0058] As a result of preliminary testing, after 1500 hours of electrical heating, penetration of the penetrant liquid from the interface between the thermally conductive glass member 332 serving as the second protective member and the substrate 331 was observed. In other words, it was confirmed that the sealing ability of the thermally conductive glass member 332 was lower than that of the FPC.

[0059] In response to this result, in the end regions in the longitudinal direction of the heater 330 in the formation region of the thermally conductive glass member 332, the conductor-to-conductor distances S1 to S4 are made different according to the distances L1 to L4 from the central part of the heater 330 of each of the thermistors 335, 336, 337, 338. Similar to the second embodiment, according to the distances L1 < L2 < L3 < L4, the conductor-to-conductor distances S1 < S2 < S3 < S4 are set. In this way, by setting the conductive distance between the conductors connected to the thermistor according to the distance from the central part in the longitudinal direction of the heater to the thermistor, the occurrence of migration can be suppressed.

[0060] FIG. 9 is a schematic configuration diagram showing a modified example of the heater in the present embodiment. As shown in FIG. 9(a), the arrangement of the plurality of thermistors formed on the heater 340 is the same as that of the heater 330 described in FIG. 8. Also, the configuration in which the FPC1 and FPC2 as protective members are joined to the ends in the longitudinal direction of the heater 340 is the same as that in FIG. 8.

[0061] As shown in FIGS. 9(b) and 9(c), a thermally conductive glass member 342 as a second protective member is formed and coated on the regions where the FPC1 and FPC2 as the first protective members are not formed. Further, by forming and coating a pressure-resistant glass member 343 as a third protective member, the configuration is such that there is no portion where the conductor layer is exposed.

[0062] As a result of checking the sealing performance of the three protective members by the above-described preliminary verification, after 2000 hours of energization heating time, penetration of the penetrant from the interface between the pressure-resistant glass member 343 as the third protective member and the substrate 341 was observed. That is, it was confirmed that the sealing performance of the pressure-resistant glass member 343 is lower than the sealing performance of the FPC and the sealing performance of the thermally conductive glass member 342. The lowest sealing performance Pressure-resistant glass member 343In the formation region, in the end regions in the longitudinal direction of the heater 340, make the conductor-to-conductor distances S1 to S4 different according to the distances L1 to L4 from the central part of the heater 340 to each of the thermistors 345, 346, 347, 348. Similar to the second embodiment, make the conductor-to-conductor distances S1 < S2 < S3 < S4 according to the distances L1 < L2 < L3 < L4. Thus, by setting the conductive distance between the conductors connected to the thermistors according to the distance from the central part in the longitudinal direction of the heater to the thermistor, the occurrence of migration can be suppressed.

[0063] When a plurality of types of protective members are formed over the entire area of the conductor layer to which the thermistors are connected as in this embodiment, there is a possibility that liquefied moisture may penetrate from the interface between the substrate and the protective member or the like into the conductor layers in the formation region of the protective member with the lowest sealing property. Further, there is a possibility that a migration phenomenon may occur due to the potential difference applied to the thermistors. Therefore, in the end regions in the longitudinal direction of the region where the protective member with the lowest sealing property is formed, set the conductive distance between the conductors connected to the thermistors according to the distance from the central part in the longitudinal direction of the heater to the thermistor. Thereby, the occurrence of migration can be suppressed.

[0064] (Fourth Embodiment) In this embodiment, a configuration in which the heating element formed on the heater is divided into a plurality of heating blocks in the longitudinal direction of the heater will be described. Note that detailed descriptions of configurations similar to those of the previous first to third embodiments, such as an image forming apparatus, are omitted here.

[0065] Fig. 10 is a schematic diagram showing the configuration of heater 350. Fig. 10(a) shows a plan view of the first surface of heater 350 on which the heating element is formed. The heating element is divided into multiple heating blocks in the longitudinal direction of heater 350. Power is supplied to divided heating elements 354a-1 to 354a-7 and heating elements 354b-1 to 354b-7 using electrodes E-1 to E-7 and common power sources E2 and E3. The electrodes and heating elements are connected by conductor layers 355-1 to 355-7, conductor layers 351a, and conductor layers 351b.

[0066] FIG. 10(b) shows a plan view of the second surface of the heater 350. A plurality of thermistors are arranged for detecting the temperature of each of the divided heat generating blocks. Then, the power supply to the plurality of heat generating elements is controlled based on the detection results of the thermistors. In FIG. 10(b), FPC1 and FPC2 as first protective members are bonded to the longitudinal end portions of the heater 350. In addition, a thermally conductive glass member 352 is formed as a second protective member, and a pressure-resistant glass member 353 is formed thereon as a third protective member. At this time, the sealing property of the protective members is the weakest. Pressure-resistant glass member 353 In the formation region, the technical concept of the conductor distance explained in the first to third embodiments is applied to the end region in the longitudinal direction of the heater 350.

[0067] Specifically, the distance from the center of the heater 350 in the longitudinal direction to thermistor T1-1 is defined as L1, the distance to thermistor T2-2 as L2, the distance to thermistor T1-7 as L3, and the distance to thermistor T2-6 as L4. The relationships between these distances are L1>L2 and L3>L4. Furthermore, the inter-conductor distance between the conductor layer EGa and the conductor layer ET1-1 connected to thermistor T1-1 is defined as S1. Furthermore, the inter-conductor distance between the conductor layer EGb and the conductor layer ET2-2 connected to thermistor T2-2 is defined as S2. Furthermore, the inter-conductor distance between the conductor layer EGa and the conductor layer ET1-7 connected to thermistor T1-7 is defined as S3. Furthermore, the inter-conductor distance between the conductor layer EGb and the conductor layer ET2-6 connected to thermistor T2-6 is defined as S4. According to the above distances L1>L2, L3>L4, the inter-conductor distances are set to S1>S2, S3>S4.

[0068] In the first to fourth embodiments, the surface on which the heating element is formed is the surface that slides against film 230, but this is not limiting. A surface on which a thermistor is formed and a protective member is formed thereon may also be the surface that slides against film 230. Furthermore, the configurations of the first to fourth embodiments can be used not only in a configuration in which the heater surface slides directly against the film, but also in a fixing device that has a sliding plate between the film and the heater. [Explanation of symbols]

[0069] 210 Heater 211 Substrate 212 Heating element 215, 216 Thermistor 215T, 215G, 216T, 216G conductor layer ET1, ET2 power supply terminals EG1, EG2 ground terminal

Claims

1. A thin board and a heating element disposed on a first surface of the substrate; a first temperature detection element disposed on a second surface behind the first surface of the substrate; a second temperature detection element disposed on the second surface; a first conductor disposed on the second surface for connecting the first temperature detection element and a first power supply terminal; a second conductor disposed on the second surface for connecting the first temperature detection element and a first ground terminal; a third conductor disposed on the second surface for connecting the second temperature detection element and a second power supply terminal; a fourth conductor disposed on the second surface for connecting the second temperature detection element and a second ground terminal, In a longitudinal direction of the heater, a distance from a center of the heater to the first temperature detection element is a first distance, and a distance from the center of the heater to the second temperature detection element is a second distance that is longer than the first distance; a first region in the longitudinal direction of the heater that is farther from the center of the heater than the second temperature detection element, wherein the distance between the first conductor and the second conductor in the short direction of the heater is a first inter-conductor distance, the distance between the third conductor and the fourth conductor is a second inter-conductor distance that is longer than the first inter-conductor distance, and a second region in the short direction of the heater that is farther from the center of the heater than the first region, wherein the distance between the first conductor and the second conductor in the short direction of the heater is a third inter-conductor distance, and the distance between the third conductor and the fourth conductor is the third inter-conductor distance.

2. 2. The heater according to claim 1, wherein, in the second region, the first conductor and the first power supply terminal are connected, the second conductor and the first ground terminal are connected, the third conductor and the second power supply terminal are connected, and the fourth conductor and the second ground terminal are connected.

3. 3. The heater according to claim 2, wherein the second region is covered with a first protective member.

4. the first region is covered with a second protective member different from the first protective member, 4. The heater according to claim 3, wherein the second protective member has a lower sealing property than the first protective member.

5. a third region closer to the central portion than the first region is covered with a second protective member different from the first protective member; the first region and the third region are covered by a third protective member different from the second protective member, 4. The heater according to claim 3, wherein the third protective member has a lower sealing property than the first protective member and the second protective member.

6. a third temperature detection element disposed on the second surface; a fourth temperature detection element disposed on the second surface; a fifth conductor disposed on the second surface for connecting the third temperature detection element and a third power supply terminal; a sixth conductor disposed on the second surface for connecting the fourth temperature detection element and a fourth power supply terminal; the second conductor is a conductor for connecting the third temperature detection element and a third ground terminal, the fourth conductor is a conductor for connecting the fourth temperature detection element and a fourth ground terminal, In a longitudinal direction of the heater, a distance from a center of the heater to the third temperature detection element is a third distance, and a distance from the center of the heater to the fourth temperature detection element is a fourth distance that is longer than the third distance; 2. The heater according to claim 1, wherein in a fourth region of the heater that is farther from the center of the heater than the fourth temperature detection element in the longitudinal direction of the heater, the distance between the first conductor and the fifth conductor in the short direction of the heater is a fourth inter-conductor distance, and the distance between the third conductor and the sixth conductor is a fifth inter-conductor distance that is longer than the fourth inter-conductor distance.

7. 7. The heater according to claim 6, wherein in a fifth region of the heater that is farther from the center of the heater than the fourth region in the longitudinal direction of the heater, the distance between the first conductor and the fifth conductor in the short direction of the heater is a sixth inter-conductor distance, and the distance between the third conductor and the sixth conductor is the sixth inter-conductor distance.

8. 8. The heater according to claim 7, wherein, in the fifth region, the fifth conductor and the third power supply terminal are connected, the first conductor and the third ground terminal are connected, the sixth conductor and the fourth power supply terminal are connected, and the third conductor and the fourth ground terminal are connected.

9. 9. The heater according to claim 8, wherein the fifth region is covered by a first protective member.

10. the fourth region is covered by a second protective member different from the first protective member, 10. The heater according to claim 9, wherein the second protective member has a lower sealing property than the first protective member.

11. a sixth region closer to the central portion than the fourth region is covered with a second protective member different from the first protective member; the fourth region and the sixth region are covered by a third protective member different from the second protective member, 10. The heater according to claim 9, wherein the third protective member has a lower sealing property than the first protective member and the second protective member.

12. a plurality of heating elements arranged side by side in the longitudinal direction on the first surface; a first heat generating block including some of the plurality of heat generating elements; 2. The heater according to claim 1, further comprising: a second heat generating block including a heat generating element disposed closer to the end in the longitudinal direction than the heat generating element included in the first heat generating block.

13. The heater according to claim 12, characterized in that, when viewed in the thickness direction of the heater, the first temperature detection element overlaps with the first heat generating block, and the second temperature detection element overlaps with the second heat generating block.

14. a cylindrical film heated by the heater according to claim 1; a pressure roller that forms a nip portion with the film, A heating device characterized in that the heater is arranged in the internal space of the film, the film is sandwiched between the heater and the pressure roller, and the image formed on the recording material is heated through the film at the nip portion.

15. an image forming means for forming an image on a recording material; An image forming apparatus comprising: the heating device according to claim 14 for fixing an image formed on a recording material.

Images