JP2022024718A - Heater member, heating device, fixing device, and image forming apparatus - Google Patents

Abstract

To ensure the safety of a heater member with a small number of current breaking members or temperature detection members.SOLUTION: A heater member 330 has: a resistance pattern 332a that has a plurality of rows of resistors 332a1-332a4 formed in a longitudinal direction of a substrate 331 and generating heat upon energization, wherein the plurality of rows of resistors are connected in parallel while being separated from each other in a short direction orthogonal to the longitudinal direction of the substrate; first temperature detection members (thermistors TM1) that are disposed over at least two or more rows of resistors in the short direction and detect the temperature of the resistors; and second temperature detection members (thermistors TM2) that are disposed over at least two or more rows including resistors different from the resistors detected by the first temperature detection members in the short direction and detect the temperature of the at least two or more rows of resistors.SELECTED DRAWING: Figure 6A

Description

The present invention relates to a heater member, a heating device, a fixing device, and an image forming device, and particularly relates to a heater member having a resistance pattern that generates heat by energization, and a heating device, a fixing device, and an image forming device using the heater member.

Various types of fixing devices used in electrophotographic image forming devices are known. One of them is a model in which a thin-walled fixing belt having a low heat capacity is directly heated by a heater member (see Patent Documents 1 to 3). The heater member is composed of a base material and a resistance pattern (plane heater). A pressure roller as a pressure member is disposed on the outside of the fixing belt, and the pressure roller sandwiches the fixing belt and presses it against the heater member to form a fixing nip.

In the fixing devices of Patent Documents 1 to 3, a plurality of resistance patterns are arranged in the longitudinal direction of the base material. Then, the first resistance pattern in the center in the longitudinal direction is energized to heat the small size paper. In addition, second resistance patterns are arranged at both ends in the longitudinal direction, and the first and second resistance patterns are simultaneously energized to heat large-sized paper.

These resistance patterns are generally formed by printing a resistance material on a ceramic substrate or the like at one time by screen printing. The area and thickness of each resistance pattern are made constant so that the resistance value (heat generation distribution) becomes uniform in the longitudinal direction of the base material. In this homogenization, the first resistance pattern in the center is wider and has a larger area than the second resistance patterns at both ends. Therefore, at least the first resistance pattern is divided into a plurality of patterns in the longitudinal direction, and these multiple patterns are divided into a plurality of patterns. I try to connect in parallel.

However, as the number of resistance patterns connected in parallel increases, it becomes difficult to control the temperature of the fixing belt and ensure safety in the event of a disconnection failure. In the fixing device of Patent Document 1 (Japanese Patent No. 6336026), the central first resistance pattern is divided into 15 in parallel, and the second resistance patterns at both ends are divided into three in parallel. Then, the temperature of the fixing belt is controlled by four thermistors, and when the temperature of the first or second resistance pattern reaches the high temperature threshold value due to a failure, the current of the heater member is cut off by the safety element arranged between the two resistance patterns. (See Fig. 3).

As can be seen from this, when the number of resistance patterns of parallel connection is large, the structure becomes complicated, it becomes difficult to cope with miniaturization, and the cost becomes high. Therefore, an object of the present invention is to ensure the safety of the heater member with a small number of temperature detecting members.

In order to solve the above problems, the heater member of the present invention has a plurality of rows of resistors formed in the longitudinal direction of the base material and generates heat by energization, and the plurality of rows of resistors are orthogonal to the longitudinal direction of the base material. A resistance pattern connected in parallel in a state of being separated from each other in the lateral direction and a temperature of the resistors arranged in at least two rows or more of the resistors in the lateral direction. It is arranged over at least two rows including a first temperature detecting member to be detected and a resistor different from the resistor detected by the first temperature detecting member in the lateral direction, and the at least two rows. It is characterized by having a second temperature detecting member for detecting the temperature of the above resistor.

According to the present invention, the safety of the heater member can be ensured with a small number of temperature detecting members.

It is a schematic block diagram of the image forming apparatus which concerns on embodiment of this invention. It is a principle diagram of the image forming apparatus which concerns on embodiment of this invention. It is a schematic block diagram of the fixing device. It is a top view of the heater member which concerns on the basic embodiment of this invention. It is a top view of the heater member which concerns on another basic embodiment of this invention. It is a top view of the heater member as a comparative example which changed the position of a thermistor. It is a top view of the heater member as a comparative example which changed the position of a thermistor. It is sectional drawing of the heater member which shows two examples (a) (b) which changed the position of a resistance pattern. It is (a) plan view, (b) side view, (c) sectional view of the thermistor. It is a top view of the heater member which concerns on application embodiment of this invention. It is a top view of the heater member which concerns on another application embodiment of this invention. It is a top view of the heater member as a comparative example which changed the position of a thermistor. It is a top view of the heater member as a comparative example which changed the position of a thermistor. It is a top view of the conventional heater member. It is an electric circuit diagram of the heater member of FIG. 8A. It is a figure which shows the structure of another fixing device. It is a figure which shows the structure of the other fixing device.

Hereinafter, the heater member, the fixing device, and the image forming apparatus (laser printer) according to the embodiment of the present invention will be described with reference to the drawings. The laser printer is an example of an image forming apparatus, and it goes without saying that the image forming apparatus is not limited to the laser printer. That is, the image forming apparatus can be configured as any one of a copying machine, a facsimile, a printer, a printing machine, and an inkjet recording device, or a multifunction device in which at least two or more of these are combined.

The same or corresponding parts in each figure are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted. Further, the dimensions, materials, shapes, relative arrangements thereof, etc. in the description of each component are examples, and the scope of the present invention is not intended to be limited thereto unless otherwise specified.

In the following embodiments, the "recording medium" which is a sheet material will be described as "paper", but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper (paper) but also OHP sheets, cloths, metal sheets, plastic films, prepreg sheets in which carbon fibers are preliminarily impregnated with resin, and the like.

A medium to which a developer or ink can be attached, a recording paper, and a recording sheet are all included in the "recording medium". In addition to plain paper, "paper" also includes thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

Further, the "image formation" used in the following description is not only to give an image having a meaning such as characters or figures to the medium, but also to give an image having no meaning such as a pattern to the medium. Also means.

(Laser printer configuration)
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. In addition to the printer, the image forming apparatus may be a copying machine, a facsimile, or a combination machine thereof.

The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk, which are image forming units. Each image forming unit 1Y, 1M, 1C, 1Bk is configured to be detachably attached to the image forming apparatus main body 103, and develops different colors of yellow, magenta, cyan, and black corresponding to the color separation component of the color image. It has the same structure except that it is housed.

Specifically, each image processing unit 1Y, 1M, 1C, 1Bk is formed on the drum-shaped photoconductor 2 as an image carrier, the charging device 3 for charging the surface of the photoconductor 2, and the surface of the photoconductor 2. It includes a developing device 4 that supplies toner as a developing agent to form a toner image, and a cleaning device 5 that cleans the surface of the photoconductor 2.

Further, the image forming apparatus 100 is formed on each photoconductor 2, an exposure apparatus 6 that exposes the surface of each photoconductor 2 to form an electrostatic latent image, a paper feeding device 7 that supplies paper P as a recording medium, and each photoconductor 2. A transfer device 8 for transferring the transferred toner image to the paper P, a fixing device 300 for fixing the toner image transferred to the paper P, and a paper ejection device 10 for discharging the paper P to the outside of the device are provided.

The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer body stretched by a plurality of rollers, and four primary transfer members for transferring a toner image on each photoconductor 2 to the intermediate transfer belt 11. It has a primary transfer roller 12 and a secondary transfer roller 13 as a secondary transfer member that transfers the toner image transferred on the intermediate transfer belt 11 to the paper P. Each of the plurality of primary transfer rollers 12 is in contact with the photoconductor 2 via the intermediate transfer belt 11.

As a result, the intermediate transfer belt 11 and each photoconductor 2 are in contact with each other, and a primary transfer nip is formed between them. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretches the intermediate transfer belt 11 via the intermediate transfer belt 11. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

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

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

When instructed to start the printing operation, in each image forming unit 1Y, 1M, 1C, 1Bk, the photoconductor 2 is rotationally driven clockwise in FIG. 1, and the surface of the photoconductor 2 is uniformly raised by the charging device 3. It is charged to the electric potential. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the document read by the document reader or the print information instructed to print from the terminal, so that the potential of the exposed portion is increased. It is lowered to form an electrostatic latent image. Then, toner is supplied from the developing device 4 to the electrostatic latent image, and a toner image is formed on each photoconductor 2.

When the toner image formed on each photoconductor 2 reaches the primary transfer nip (position of the primary transfer roller 12) as the photoconductor 2 rotates, the intermediate transfer belt is rotationally driven counterclockwise in FIG. It is transferred to 11 so as to sequentially overlap. Then, the toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer nip (position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is conveyed at the secondary transfer nip. Transferred to paper P.

This paper P is supplied from the paper feeding device 7. The paper P supplied from the paper feed device 7 is temporarily stopped by the timing roller 15, and then transferred to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, a full-color toner image is supported on the paper P. Further, after the toner image is transferred, the toner remaining on each photoconductor 2 is removed by each cleaning device 5.

The paper P on which the toner image is transferred is conveyed to the fixing device 300, and the toner image is fixed on the paper P by the fixing device 300. After that, the paper P is ejected to the outside of the paper ejection device 10, and a series of printing operations is completed.

(Principle of laser printer)
FIG. 2A is a principle diagram of a laser printer as an embodiment of an image forming apparatus 100 provided with the fixing apparatus 300 of the present invention. The image forming apparatus 100 has an image carrier 2 (for example, a photoconductor drum) and a drum cleaning apparatus 5. Further, a charging device 3 as a charging means for uniformly charging the surface of the image carrier, a developing device 4 as a developing means for performing visible image processing of an electrostatic latent image formed on the image carrier, and an image carrier. It has a transfer means T disposed below the body 2, a static eliminator, and the like.

The exposure apparatus 6 is arranged above the image carrier 2. The exposure apparatus 6 performs write scanning according to the image information, that is, reflects the laser beam Lb from the laser diode by the mirror 6a based on the image data and irradiates the image carrier 2.

The paper feeding device 50 having a tray for loading the paper P is installed below the image forming device 100. The paper feeding device 50 can accommodate a large number of sheets P as a recording medium in a bundle, and is unitized together with a paper feed roller 60 as a means for transporting the paper P.

A resist roller pair 250 as a separation and transporting means is arranged on the downstream side of the paper feed roller 60. The paper P fed from the paper feeding device 50 is temporarily stopped by the resist roller pair 250. By this temporary stop, a slack is formed on the tip side of the paper P, and the skew of the paper P is corrected.

The paper P, which is abutted against the resist roller pair 250 and has a slack formed at the tip end portion, is sent out to the transfer nip N of the transfer means T at the timing when the toner image on the image carrier 2 is suitably transferred. Then, on the paper P that has been sent out, the toner image on the image carrier 2 is electrostatically transferred to a desired transfer position by the bias applied at the transfer nip N.

A fixing device 300 is arranged on the downstream side of the transfer nip N. The fixing device 300 includes a fixing belt 310 as a fixing member heated by a resistance pattern 332 described later, and a pressure roller 320 as a pressure member that rotates while abutting on the fixing belt 310 at a predetermined pressure. There is.

(Laser printer operation)
Next, the basic operation of the laser printer according to this embodiment will be described. The paper feed roller 60 rotates in response to the paper feed signal from the control unit of the image forming apparatus 100. The rotation of the paper feed roller 60 separates the top-level paper of the bundled paper P loaded on the paper feed device 50 and feeds it to the paper feed path.

When the tip of the fed paper P reaches the nip of the resist roller pair 250, it forms a slack and stands by in that state. Then, the optimum timing (synchronization) for transferring the toner image on the image carrier 2 to the paper P is set, and the tip skew of the paper P is corrected.

The charging device 3 uniformly charges the surface of the image carrier 2 to a high potential. Then, the exposure apparatus 6 reflects the laser beam Lb based on the image data by the mirror 6a and irradiates the surface of the image carrier 2.

On the surface of the image carrier 2 irradiated with the laser beam Lb, the potential of the irradiated portion is lowered to form an electrostatic latent image. The developer 4 has a developer carrier 4a that supports a developer containing toner, and an electrostatic latent image is formed on the unused black toner supplied from the toner bottle via the developer carrier 4a. The image carrier 2 is transferred to the surface portion of the image carrier 2.

The image carrier 2 to which the toner is transferred forms (develops) a toner image on the surface thereof. Then, the toner image formed on the image carrier 2 is transferred to the paper P by the transfer means T.

The drum cleaning device 5 removes residual toner adhering to the surface of the image carrier 2 after the transfer process with the cleaning blade 5a. The removed residual toner is collected in the waste toner accommodating portion.

The paper P on which the toner image is transferred is conveyed to the fixing device 300. The paper P conveyed to the fixing device 300 is sandwiched between the fixing belt 310 and the pressure roller 320, and the unfixed toner image is fixed to the paper P by heating and pressurizing. The paper P on which the toner image is fixed is sent out from the fixing device 300.

(Fixing device)
Subsequently, the configuration of the fixing device 300 will be described. As shown in FIG. 2B, the fixing device 300 according to the present embodiment has a fixing belt 310 made of an endless belt member as a fixing member and an opposing member that contacts the outer peripheral surface of the fixing belt 310 to form a nip N. The pressure roller 320 and the heater member 330 for heating the fixing belt 310 are provided. The heater member 330 is held by the heater holder 344, and the heater holder 344 is reinforced in the longitudinal direction by the stay 350 as a reinforcing member.

The fixing belt 310 is made of a flexible sleeve-shaped rotating member, and has, for example, a polyimide (PI) tubular substrate having an outer diameter of 25 mm and a thickness of 40 to 120 μm. On the outermost surface layer of the fixing belt 310, a mold release layer having a thickness of 5 to 50 μm is formed of a fluororesin such as PFA or PTFE in order to enhance durability and ensure mold release.

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 310 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. Polyimide, PTFE, or the like may be coated on the inner peripheral surface of the fixing belt 310 as a sliding layer.

The pressure roller 320 has, for example, an outer diameter of 25 mm, and has a solid iron core metal 321, an elastic layer 322 formed on the surface of the core metal 321 and a mold release layer formed on the outside of the elastic layer 322. It is composed of 323 and. The elastic layer 322 is made of silicone rubber and has a thickness of, for example, 3.5 mm. It is desirable that the surface of the elastic layer 322 forms a mold release layer 323 made of a fluororesin layer having a thickness of, for example, about 40 μm, in order to improve the mold release property.

The heater member 330 is provided longitudinally across the width direction of the fixing belt 310, and is arranged so as to come into contact with the inner peripheral surface of the fixing belt 310. The heater member 330 may be in non-contact with the fixing belt 310 or indirectly with a low friction sheet or the like, but it is better to bring the heater member 330 into direct contact with the fixing belt 310. The heat transfer efficiency to the fixing belt 310 is improved.

Further, the heater member 330 can be brought into contact with the outer peripheral surface of the fixing belt 310, but if the outer peripheral surface of the fixing belt 310 is damaged by the contact with the heater member 330, the fixing quality may deteriorate. Therefore, the heater member 330 Should be in contact with the inner peripheral surface of the fixing belt 310.

The heater member 330 is composed of a base material 331, a resistance pattern 332 laminated on the nip N side of the base material 331, and an insulating layer 333.

The base material 331 can be made of, for example, a ceramic such as alumina or aluminum nitride. Since ceramic has a linear expansion coefficient close to that of glass, when glass is used for the insulating layer 333, there is an advantage that shearing force is not easily applied to the resistance pattern 332 due to the displacement between the base material 331 and the insulating layer 333 during thermal expansion.

Further, since the thermal conductivity of ceramic is higher than that of metal such as stainless steel, it is advantageous to conduct heat to the fixing belt 310 via the base material 331. As the material of the base material 331, in addition to ceramic, glass, mica and the like are also preferable because of their excellent heat resistance and insulating properties. In this embodiment, an alumina base material having a short width of 8 mm, a longitudinal width of 270 mm, and a thickness of 1.0 mm is used.

The heater holder 344 and the stay 350 are arranged on the inner peripheral side of the fixing belt 310. The stay 350 is made of a metal channel material, and both end portions thereof are supported by both side wall portions of the fixing device 300.

The stay 350 supports the surface of the heater holder 344 opposite to the heater member 330 side. As a result, the heater member 330 and the heater holder 344 are supported without being significantly bent by the pressure applied from the pressurizing roller 320. A nip N is stably formed between the fixing belt 310 and the pressure roller 320.

Since the heater holder 344 tends to become hot due to the heat of the heater member 330, it is desirable that the heater holder 344 is made of a heat-resistant material. For example, when the heater holder 344 is made of a heat-resistant resin having low thermal conductivity such as LCP or PEEK, heat transfer from the heater member 330 to the heater holder 344 is suppressed, and the fixing belt 310 can be heated efficiently. Is.

The pressure roller 320 and the fixing belt 310 are pressed against each other by a spring as an urging member. As a result, a nip N is formed between the fixing belt 310 and the pressure roller 320. Further, the pressure roller 320 functions as a drive roller that is rotationally driven by transmitting a driving force from the driving means provided in the image forming apparatus main body 103.

On the other hand, the fixing belt 310 is configured to be driven to rotate with the rotation of the pressure roller 320. During rotation, the fixing belt 310 slides with respect to the heater member 330. In order to improve the slidability of the fixing belt 310, a lubricant such as oil or grease may be interposed between the heater member 330 and the fixing belt 310.

When the printing operation is started, the pressure roller 320 is rotationally driven, and the fixing belt 310 starts driven rotation. Further, the fixing belt 310 is heated by supplying electric power to the heater member 330. Then, in a state where the temperature of the fixing belt 310 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2B, the paper P on which the unfixed toner image is carried is the fixing belt 310 and the pressure roller 320. By being conveyed to the space (nip N), the unfixed toner image is heated and pressurized and fixed on the paper P.

(Basic embodiment of heater member)
3A and 3B show a basic embodiment of the heater member 330. As shown in FIGS. 3A and 3B, the main body portion of the heater member 330 is composed of the base material 331. In the longitudinal direction of the base material 331, the main body of the resistance pattern is formed, and three rows of resistance patterns 332 that generate heat by energization are formed linearly and parallel to each other and at equal intervals.

The three rows of resistance patterns 332 are separated from each other in the lateral direction perpendicular to the longitudinal direction of the base material 331, and are connected in parallel with the electrodes 337a and 337b as described later. A thermistor TM1 as a first temperature detecting member is arranged at the central portion (minimum paper width) in the longitudinal direction of the resistance pattern 332.

In FIG. 3A, the thermistor TM1 is arranged so as to straddle the first resistor 332-1 and the second resistor 332-2 from the upstream side in the paper passing direction among the three rows of resistance patterns 332. Here, "straddling" means that the thermistor TM1 overlaps both of the two rows of resistors 332-1 and 332-2 of the resistance pattern 332 in a plan view of the three-row resistance pattern 332 viewed from the thickness direction thereof. It means that it is.

By setting the mounting position of the thermistor TM1 to the upstream side in the paper direction, it is possible to accurately detect and control the temperature on the upstream side of the nip where the coldest fixing belt 310 enters, thereby maintaining good fixing performance. Can be done. Further, by arranging the thermistor TM1 in the central portion (minimum paper width) in the longitudinal direction of the resistance pattern 332, it is possible to reduce the influence of the temperature rise of the non-passing portion during paper passing, and good fixing property is maintained. can do.

A thermostat TH is arranged adjacent to the thermistor TM1 at the central portion (minimum paper width) in the longitudinal direction of the resistance pattern 332. This thermostat TH is arranged across all of the three rows of resistance patterns 332. Here, "straddling" means that the thermostat TH overlaps all three rows (332-1 to 332-3) of the resistance pattern 332 in a plan view of the three-row resistance pattern 332 viewed from the thickness direction thereof. It means that you are.

The thermostat TH is connected between one of the electrodes 337a and 337b described later and the power supply W, and when any of the resistors 332-1 to 332-3 reaches a high temperature threshold value (for example, more than 180 ° C and less than 200 ° C). , The thermostat TH is configured to cut off the power supply to the resistance pattern 332 for safety. In FIGS. 3A and 3B, the wiring of the thermostat TH is omitted for simplification.

The thermostat TH is generally a dish-shaped bimetal housed in a housing, and preferably the thermostat TH bimetal overlaps all three rows (332-1 to 332-3) of the resistance pattern 332 in the plan view. It is better to arrange them as if they were.

Further, another thermistor TM2 as a second temperature detecting member is disposed at one end in the longitudinal direction (right end in FIG. 3A) outside the minimum paper width of the resistance pattern 332. The arrangement position of the thermistor TM2 is the paper passing end region of the maximum paper width.

The thermistor TM2 is arranged so as to straddle the second resistor 332-2 and the third resistor 332-3 from the upstream side in the paper passing direction in the three-row resistance pattern 332. Here, "straddling" means that the thermistor TM2 overlaps both of the two rows (332-2 and 332-3) of the resistance pattern 332 in a plan view of the three-row resistance pattern 332 viewed from the thickness direction thereof. It means that you are.

By arranging the thermistor TM2 on the downstream side in the paper-passing direction, it is possible to accurately detect and control the temperature of the fixing belt 310 that has received heat from the resistance pattern 332 for a long time and has accumulated heat, thereby preventing overheating. It is possible to effectively exert the function as. Although the thermistor TM2 is provided at the right end of the resistance pattern 332 in FIG. 3A, it may be provided at the opposite left end.

On the other hand, the thermistor TM1 in FIG. 3B is arranged so as to straddle the second resistor 332-2 and the third resistor 332-3 from the upstream side in the paper passing direction in the three-row resistance pattern 332. Further, another thermistor TM2 is arranged so as to straddle the first resistor 332-1 and the second resistor 332-2 from the upstream side in the paper passing direction in the three-row resistance pattern 332. In this way, the positions of the thermistors TM1 and TM2 may be exchanged in the lateral direction (paper-passing direction) of the resistance pattern 332.

In the embodiment of FIGS. 3A and 3B, one (or both) of thermistors TM1 and TM2 are overlapped with each other without exception to the three-row resistance pattern 332. Therefore, all the temperatures of the three rows of resistance patterns 332 can be reliably detected by the thermistors TM1 and TM2.

Therefore, when the temperature rise exceeds the set temperature in any of the resistors 332-1 to 332-3, the thermistor TM1 or TM2 detects the temperature rise, and the current control by the triac based on the detection result is performed. The temperature of the resistance pattern 332 can be maintained and controlled to a desired temperature (for example, 170 ° C.). Then, regardless of the paper size, the toner image supported on the paper is fixed on the paper at a desired fixing temperature (for example, 170 ° C.).

By arranging the thermostat TH and thermistors TM1 and TM2 in the paper passing paper of all paper sizes, it is possible to prevent the influence of the temperature rise at the end of the non-paper passing portion. Therefore, when abnormal heat is generated due to a failure, the thermostat TH enables early power interruption. If the thermostat TH is arranged in the non-passing portion, it is necessary to set the operating temperature of the thermostat TH high in order to prevent false detection, which is disadvantageous in terms of safety.

The thermistor TM1 (TM2) is arranged on a surface (upper surface in FIG. 4) opposite to the nip forming surface (lower surface in FIG. 4) of the heater member 330, as shown in FIGS. 4 (a) and 4 (b) described later. Thermistor.

The dimensions and resistance values of the three-row resistance pattern 332 are as follows in the present embodiment.
-Width of one row of resistors in the resistance pattern 332 in the lateral direction: 2.0 mm
・ Interrelationship between the three rows of resistors in the lateral direction: 0.7 mm
-Width in the lateral direction of the resistance pattern 332: 7.4 mm = (2.0 x 3) + (0.7 x 2)
-Resistance value of resistance pattern 332: 16Ω
Longitudinal width of resistance pattern 332: 216 to 220 mm

The three-row resistance pattern 332 is formed by, for example, applying a resistance material paste containing silver-palladium (AgPd), glass powder, or the like to the base material 331 by screen printing or the like, and then firing the base material 331. Can be formed. In addition to these, a silver alloy (AgPt) or ruthenium oxide (RuO ₂ ) resistance material may be used as the resistance material. When a material having a positive temperature coefficient of resistance (PTC) is used as the resistance material, a material having a temperature coefficient of resistance of 300 ppm can be used, for example.

The three-row resistance pattern 332 does not necessarily have to be linear as shown in FIGS. 3A and 3B. Instead of a linear shape, a shape in which the waveform is continuous may be used. As a result, the length of the resistance pattern 332 can be increased, and the specific resistance of the resistance material paste can be lowered.

Two electrodes 337a and 337b to which an AC power source is connected are arranged at both ends in the longitudinal direction of the base material 331. One electrode 337a and one end of the three-row resistance pattern 332 are connected by a conductor 338a having a resistance value smaller than that of the resistance pattern 332. Further, the other electrode 337b and the other end of the three-row resistance pattern 332 are similarly connected by a conductor 338b having a resistance value smaller than that of the resistance pattern 332.

When the fixing device 300 is operated, the thermistors TM1 and TM2 maintain and control the temperature of the fixing belt 310 to a desired fixing temperature (for example, 170 ° C.). That is, based on the temperature detection result of the resistance pattern 332 by the thermistor TM1 or TM2, the temperature of the resistance pattern 332 is maintained and controlled to a desired temperature (for example, 170 ° C.) by the current control by the triac.

The thermostat TH and thermistors TM1 and TM2 are urged toward the base material 331 by, for example, a spring as an elastic member. The urging by this spring reduces the contact gap between the thermostat TH and the thermistor TM with respect to the base material 331. Therefore, the exact temperature of the resistance pattern 332 is transmitted to the thermostat TH and the thermistors TM1 and TM2, and the thermistors TM1 and TM2 transmit the exact temperature of the resistance pattern 332 (332-2, 332-3 and 332-1, 332-2). Can be detected.

(Comparative example)
3C and 3D show comparative examples in which the position of the thermistor TM2 at the end of the resistance pattern 332 in the lateral direction is intentionally changed unfavorably. In these comparative examples, since the resistor 332-1 that does not overlap with any of the thermistors TM1 and TM2 is formed, the temperature of the resistor 332-1 cannot be detected by any of the thermistors TM1 and TM2.

That is, in FIG. 3C, the thermistor TM2 at the end overlaps with the second and third resistors 332-2 and 332-3 like the thermistor TM1 at the center, but the first resistor 332-1 will eventually overlap. Thermistors TM1 and TM2 do not overlap. Further, in FIG. 3D, the thermistor TM2 overlaps with the second resistor 332-2, but neither thermistor TM1 nor TM2 overlaps with the first resistor 332-1.

Therefore, it is not possible to maintain and control the temperature of the resistor 332-1 to a desired temperature (for example, 170 ° C.) even if the resistor 332-1 is likely to cause an excessive temperature rise. Further, even if the resistor 332-1 is disconnected, the detection temperatures of the thermistors TM1 and TM2 do not change (do not decrease), so that the calorific value of the resistance pattern 332 decreases and fixing failure occurs. As shown in FIGS. 3A and 3B of the embodiment of the present invention, by arranging the thermistors TM1 and TM2 so as to overlap all of the resistance patterns 332 (332-1 to 332-3), the above-mentioned inconvenience is avoided. can do.

In particular, when the base material 331 is made of stainless steel having low thermal conductivity such as SUS304 (16.7 W) instead of ceramic such as alumina or aluminum nitride (AlN) having high thermal conductivity (285 W / m · K). / M · K), generally, it becomes difficult to detect the disconnection of the resistance pattern 332. However, as described above, by arranging the thermistors TM1 or TM2 on all of the resistance patterns 332 (332-1 to 332-3), there is an advantage that disconnection detection can be easily performed.

(Example of resistance pattern and thermistor arrangement)
FIGS. 4A and 4B show an example of arrangement of the resistance pattern 332 with respect to the thermistor TM1 as seen from the longitudinal cross section of the heater member 330. In FIG. 4A, a resistance pattern 332 is formed on the fixing belt 310 side of the base material 331. The resistance pattern 332 is fixed to the surface of the base material 331 in a state of being sandwiched between the two layers of insulating glass 334.

The insulating glass 334 can be made of, for example, heat-resistant glass having a thickness of 75 μm. The insulating glass 334 secures the insulating property such as the resistance pattern 332 and also secures the slidability with the inner surface of the fixing belt 310.

On the other hand, the thermistor TM1 is arranged on the back surface of the base material 331 opposite to the fixing belt 310 side. As shown in FIG. 5, which will be described later, the thermistor TM1 is in contact with the back surface of the base material 331 of the heater member 330 in a state of being urged by a spring 560. Then, the heat of the resistance pattern 332 on the front side of the base material 331 is transferred in the thickness direction of the base material 331 and transferred to the thermistor TM1 on the back side, so that the temperature of the resistance pattern 332 is detected by the thermistor TM1. ing.

On the other hand, in FIG. 4B, the resistance pattern 332 is formed on the side opposite to the fixing belt 310 of the base material 331 of the heater member 330. The resistance pattern 332 is fixed to the back surface of the base material 331 in a state of being sandwiched between the two layers of insulating glass 335.

Since the resistance pattern 332 of FIG. 4B is close to the thermistor TM1 with the insulating glass 335 interposed therebetween, it is possible to detect a more accurate temperature as compared with FIG. 4A. Further, in FIG. 4B, since the heat of the resistance pattern 332 is equalized by the base material 331 in the longitudinal direction and the lateral direction, improvement in fixing quality can be expected.

Further, by forming the heater member 330 on the side opposite to the fixing belt 310, the degree of freedom in selecting the material to be provided on the surface of the base material 331 sliding on the fixing belt 310 and the degree of freedom in surface processing are increased. In order to improve the slidability with the fixing belt 310, for example, a coating film 336 having lubricity such as polyimide or PTFE can be provided on the surface of the base material 331. When the heater member 330 is formed on the side opposite to the fixing belt 310 as shown in FIG. 4B, ceramics such as alumina and aluminum nitride (AlN) having high thermal conductivity are preferably used as the material of the base material 331. can do.

(Thermistor structure)
FIG. 5 shows the structure of the thermistor TM1 (TM2) and the state of attachment to the heater member 330. The thermistor TM1 (TM2) is provided with a temperature detection element 520 at the lower part of the main body 510, and the lower part of the main body 510 including the temperature detection element 520 is covered with a heat resistant protective tape 530.

The thermistor TM1 (TM2) is arranged on the back surface of the heater member 330 whose back surface side is held by the heater holder 344. The temperature detection element 520 is arranged at the center of the main body 510 in the longitudinal direction of the heater member 330.

A pair of left and right springs 560 are arranged on the upper surface of the main body 510 so as to sandwich the temperature detection element 520 in the longitudinal direction of the heater member 330. The temperature detection element 520 of the thermistor TM1 (TM2) is pressed against the back surface of the heater member 330 by the urging force of the spring 560.

The pair of lead portions 520a of the temperature detection element 520 are connected to the two lead wires 550 via the welded portion 520b and the conduction member 520c. The lead wire 550 is pulled out from the longitudinal end portion of the heater member 330 and connected to the heating control means (controller). The heating control means means a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

(Application embodiment of heater member)
FIG. 6A shows an application embodiment of the heater member 330, in which three resistance patterns 332a, 332b, and 332c are formed in the longitudinal direction of the base material 331. That is, the first resistance pattern 332a formed in the central portion in the longitudinal direction and the second resistance patterns 332b and 332c formed in both ends in the longitudinal direction.

For the three resistance patterns 332a, 332b, and 332c, for example, a resistance material paste having the same resistivity, which is a mixture of silver palladium (AgPd) or glass powder, is applied to the base material 331 by screen printing or the like, and then the base material is applied. It can be formed by firing 331. In addition to these, a silver alloy (AgPt) or ruthenium oxide (RuO ₂ ) resistance material may be used as the resistance material. When a material having a positive temperature coefficient of resistance (PTC) is used as the resistance material, a material having a temperature coefficient of resistance of 300 ppm can be used, for example.

By selectively energizing and heating these three resistance patterns 332a, 332b, and 332c, each paper size (A3 to A6) is efficiently heated. That is, when passing and heating large size paper such as A3 paper and B4 paper, all resistance patterns 332a, 332b, and 332c are energized and heated. On the other hand, when passing and heating small-sized paper such as A4, B5, A5, B6, and A6, only the central resistance pattern 332a is energized and heated.

(First resistance pattern)
The first resistance pattern 332a at the center of the base material 331 in the longitudinal direction has four rows of resistors 332a1 to 332a4 as the first resistors linearly extending in the longitudinal direction of the base material 331. The thermostat TH1 as a current cutoff member is arranged so as to completely include these four rows of resistors 332a1 to 332a4 in a plan view. Similar to the thermistor TM1 of FIG. 4, the thermostat TH1 is arranged on the surface of the heater member 330 opposite to the nip forming surface.

A thermistor TM1 as a first temperature detecting member is arranged in the vicinity of the thermostat TH1. The thermistor TM1 is arranged so as to straddle the resistors 332a1 and 332a2 in two rows on the upstream side in the paper passing direction, which is the lateral direction.

Further, the thermostat TH1 and the thermistor TM1 are arranged in the longitudinal direction of the base material 331 almost in the center which is not easily affected by the temperature rise of the non-passing portion during paper passing, and are within the range of the minimum paper width (for example, A6 paper width). It is arranged. Thereby, good fixing property can be maintained.

Here, the above-mentioned "straddling" means that the thermistor TM1 overlaps both of the two rows of resistors 332a1 and 332a2 in a plan view of the four rows of resistors 332a1 to 332a4 when viewed from the thickness direction thereof. By setting the mounting position of the thermistor TM1 to the upstream side in the paper direction, it is possible to accurately detect and control the temperature on the upstream side of the nip where the coldest fixing belt 310 enters, thereby maintaining good fixing performance. Can be done.

Another thermistor TM2 as a second temperature detecting member is disposed at the longitudinal end of the first resistance pattern 332a. The thermistor TM2 is arranged so as to straddle the resistors 332a3 and 332a4 in two rows on the downstream side in the paper passing direction. Here, "straddling" means that the thermistor TM2 overlaps both of the two rows (332a3 and 332a4) of the resistors in a plan view of the four rows of resistors 332a1 to 332a4 when viewed from the thickness direction thereof. ..

By arranging the thermistor TM2 on the downstream side in the paper-passing direction, it is possible to accurately detect and control the temperature of the fixing belt 310 that has received heat from the first resistance pattern 332a for a long time and has stored heat, thereby overheating. The function as a temperature prevention sensor can be effectively exerted. Although the thermistor TM2 is provided at the right end of the first resistance pattern 332a in FIG. 6A, it may be provided at the opposite left end.

The four rows of resistors 332a1 to 332a4 have the same length, width, and thickness, and are arranged at equal intervals and in parallel with each other. By using four rows, the amount of heat generated per row can be suppressed (to prevent the resistance value from becoming too small).

The first resistance pattern 332a at the center of the base material 331 in the longitudinal direction has a larger heat generation region than the second resistance patterns 332b and 332c at both ends in the longitudinal direction. Therefore, the first resistance pattern 332a in the center requires a large amount of electric power, and conversely, the resistance value needs to be small.

The resistance value can be reduced by making the four rows of resistors 332a1 to 332a4 linear (shortest length). Thereby, as described later, the first resistance pattern 332a in the center in the longitudinal direction and the second resistance patterns 332b and 332c at both ends in the longitudinal direction can be formed by the material paste having the same resistivity.

Both ends of the four rows of resistors 332a1 to 332a4 in the longitudinal direction are connected in parallel to the electrodes 337c and 337f via conductors 338c, 338f2 and 338f3. The right electrode 337f is connected to one pole of the 100V AC power supply PW, and the other electrodes 337c, 337d, 337e are connected to the other pole of the 100V AC power supply PW via switches SW1 and SW2.

Therefore, by operating the switches SW1 and SW2, the central resistance pattern 332a and the resistance patterns 332b and 332c at both ends can be independently energized / cut off. As a result, the fixing device 300 can be adapted to various paper sizes, and the energy saving of the fixing device 300 can be improved by turning off the electric power of the unnecessary portion. Further, by intermittently energizing and heating only the second resistance patterns 332b and 332c at both ends by operating the switch SW2, it is possible to suppress the tendency of temperature dripping at both ends of the paper passing portion of the fixing belt 310.

The arrangement of the switches SW1 and SW2 can be changed so that the switches SW1 and SW2 are connected in series as shown by the chain line rectangular frame in FIG. 6A. That is, in the chain line rectangular frame on the lower side of FIG. 6A, the switch SW1 and the electrode 337c are branched into the switch SW2. By changing the position of the switch SW1, the ON-OFF control of the central resistance pattern 332a and the ON-OFF control of the full-width resistance patterns 332a to 332c can be switched.

The four rows of resistors 332a1 to 332a4 described above do not necessarily have to be linear as shown in FIG. 6A. Instead of a linear shape, a shape in which the waveform is continuous may be used. As a result, the lengths of the resistors 332a1 to 332a4 can be increased, and the specific resistance of the resistance material paste can be reduced.

(Second resistance pattern)
The second resistance patterns 332b and 332c at both ends in the longitudinal direction are composed of a second resistor that is continuous in a zigzag manner in the lateral direction of the base material 331. The width in the lateral direction of the second resistance patterns 332b and 332c at both ends is the same as the width in the lateral direction of the first resistance pattern 332a in the center. Further, the longitudinal width of the second resistance pattern 332b and 332c is a fraction of the longitudinal width of the central first resistance pattern 332a.

The zigzag fold of the second resistance pattern 332b and 332c is composed of four steps in the lateral direction of the base material 331. The line width and thickness of the resistance patterns 332b and 332c are set so that the resistance value (heat generation distribution) becomes uniform in the longitudinal direction of the base material 331 including the first resistance pattern 332a.

By making the length of the second resistance pattern 332b and 332c by winding in a zigzag manner, the specific resistance of the resistivity material paste can be lowered and the unevenness of the temperature distribution in the short direction can be suppressed. If the second resistance pattern 332b and 332c are not folded in a zigzag manner but are made into a single pattern in the lateral direction, a local high temperature portion is formed, which is not preferable.

On the other hand (left side), the thermistor TM3 as a third temperature detecting member is arranged so as to straddle the second and third stages from the upstream side in the paper passing direction of the resistance pattern 332b. The arrangement position of the thermistor TM2 is the paper passing end region of the maximum paper width. "Straddling" means that the thermistor TM3 overlaps both the second and third stages in a plan view of the resistance pattern 332b when viewed from the thickness direction thereof.

The position of the thermistor TM3 in the longitudinal direction is approximately the center of the resistance pattern 332b in the longitudinal direction. By arranging the thermistor TM3 at the center position of the resistance pattern 332b in this way, the accurate temperature of the second resistance pattern 332b can be detected. Since the second resistance pattern 332b is continuous with one zigzag fold, the energization to the second resistance pattern 332b is cut off regardless of which stage in the paper passing direction the disconnection occurs. Therefore, it is not necessary to arrange the thermistor TM3 so as to include all of the width in the paper passing direction (short side direction).

On the other hand (right side), in the resistance pattern 332c, the thermostat TH2 as the second current cutoff member is arranged across all four stages in the paper passing direction. The longitudinal position of the thermostat TH2 does not necessarily have to be the longitudinal center of the resistance pattern 332c. "Straddling all four steps in the paper passing direction" means that the thermostat TH2 overlaps all four steps in the paper passing direction in a plan view of the resistance pattern 332c in the thickness direction.

As described above, the thermistor TM3 is disposed on one of the second resistance patterns 332b and 332c, and the thermostat TH2 is disposed on the other. This is because the second resistance patterns 332b and 332c are connected in parallel, so that the configuration is sufficient for temperature control of the second resistance patterns 332b and 332c and current cutoff when an overheating occurs.

The temperature of the fixing belt 310 is controlled to a desired temperature by controlling the electric power supplied to the heater member 330 by the heating control means (controller) according to the detection temperature detected by the thermistors TM1 and TM3 described above. However, at the time of paper passing or the like, the temperature of the fixing belt 310 is controlled to a desired temperature by appropriately applying additional power in consideration of the heat removal due to the paper passing, in addition to the detected temperature. As described above, the heating control means means a microcomputer including a CPU, a ROM, a RAM, an I / O interface, and the like.

(Uniformization of heat generation density)
Here, the equalization of the heat generation densities of the first resistance pattern 332a and the second resistance patterns 332b and 332c described above will be described. Assuming that the required calorific value of the entire first resistance pattern 332a is 900 W, the calorific value per row is 225 W in four equal parts. Assuming that the length of the first resistance pattern 332a in the longitudinal direction is 216 mm, the heat generation density [W / mm] is 1.04 [W / mm].

On the other hand, the second resistance patterns 332b and 332c at both ends in the longitudinal direction, which will be described later, are continuous in a zigzag manner in the lateral direction of the base material 331 to increase the total length (the resistance value is earned). Here, when the length of the second resistance pattern 332b and 332c in the longitudinal direction is 43 mm, the resistance pattern 332b and 332c have the same heat generation density [W / mm] in the longitudinal direction as the first resistance pattern 332a in the center. In order to obtain the heat, the second resistance pattern 332b and 332c require a calorific value of 179 W each by the following calculation.
Central first resistance pattern 332a: 900W / 216mm = 4.17W / mm
Second resistance pattern 332b at both ends, c: 179W / 43mm = 4.16W / mm

When the length of the second resistance pattern 332b and 332c in the longitudinal direction is 43 mm and the zigzag folds are formed three times (four steps), the total length of the resistance patterns 332b and 332c is 172 mm. The heat generation density [W / mm] is 179 W / 172 mm = 1.04 [W / mm], which is the same as the heat generation density of the first resistance pattern 332a described above, so that the three resistance patterns 332a to 332c are used. It can be seen that it can be formed with a resistance material having the same resistivity. As a result, the three resistance patterns 332a to 332c can be screen-printed at the same time, which contributes to cost reduction.

(Other embodiments of the heater member)
FIG. 6B shows another embodiment of the heater member 330. In this embodiment, the positions of the thermistors TM1 and TM2 in the lateral direction are reversed from those in FIG. 6A. That is, the thermistor TM1 of FIG. 6B is arranged so as to straddle the third-stage resistor 332a3 and the fourth-stage resistor 332a4 on the downstream side in the paper-passing direction, and another thermistor TM2 is 1 on the upstream side in the paper-passing direction. It is arranged so as to straddle the stage resistor 332a1 and the second stage resistor 332a2.

As described above, even if the positions of the thermistors TM1 and TM2 in the lateral direction are opposite to those in FIG. 6A, the thermistors TM1 or TM2 overlap all of the four rows of resistors 332a1 to 332a4. Therefore, all the temperatures of the resistors 332a1 to 332a4 in the four rows can be detected by any of the thermistors TM1 or TM2, and the excessive temperature rise of the resistors can be prevented.

(Comparative example of heater member)
6C and 6D show comparative examples in which the positions of thermistors TM1 and TM2 of the heater member 330 are intentionally changed unfavorably. That is, the thermistors TM1 and TM2 in FIG. 6C are both in the two rows in the center in the lateral direction of the four rows of resistors 332a1 to 332a4, that is, in the second row of resistors 332a2 and the third row of resistors 332a3. It is arranged straddling.

Therefore, the temperatures of the resistors 332a1 in the first row and the resistors 332a4 in the fourth row cannot be detected by the thermistors TM1 and TM2. Therefore, even if an excessive temperature rise occurs in the resistor 332a1 in the first row or the resistor 332a4 in the fourth row, the temperature rise cannot be detected by the thermistors TM1 and TM2, and the resistance temperature rise is excessive. Cannot be prevented.

FIG. 6D shows the position of the thermistor TM2 in FIG. 6C shifted to the upstream side, and the thermistor TM2 is attached to the first row resistors 332a1 and the second row resistors 332a2 of the four rows of resistors 332a1 to 332a4. It is arranged straddling. In this case, the temperature of the resistors 332a1 to 332a3 in the first to third rows can be detected by the thermistors TM1 or TM2, but the temperature of the resistors 332a4 in the fourth row can be detected by the thermistors TM1 and TM2. Can't.

Therefore, even if an overheating occurs in the resistor 332a4 in the fourth row, it is not possible to prevent the overheating of the resistor. Therefore, it is necessary to dispose the thermistors TM1 and TM2 as shown in FIGS. 6A and 6B of the embodiment of the present invention.

(Suppressing variation in calorific value considering the magnitude of conductor resistance)
Next, the suppression of variation in the calorific value in consideration of the magnitude of the resistance value of the conductor connected to each resistance pattern will be described. FIG. 7A shows the arrangement state of the thermistors TM1, TM2, and the thermostats TH1 to TH5 with respect to the conventional heater member 330'.

Further, FIG. 7B is an electric circuit diagram of the configuration of FIG. 7A. In FIG. 7B, the resistance values R1 to R7 indicate the resistance of each resistor 332a-1 to 332a-5, 332b, 332c, and the resistance values r1 to r14 are conductors 338c2 (r14), 338c1 (r10-r13), 338d. The resistance values of (r1), 338f1 (r2-r8), and 338e (r9) are shown.

Here, the resistors 332a-1 to 332a-5, 332b, and 332c are referred to as heating elements 1 to 7 for convenience, and the electric resistance starts from the electrodes 337c to 337f and passes through the heating elements 1 to 7. The values are as follows.
Heating element 1: r1 + R1 + r2 + r3 + r4 + r5 + r6 + r7 + r8
Heating element 2: r14 + R2 + r3 + r4 + r5 + r6 + r7 + r8
Heating element 3: r14 + r13 + R3 + r4 + r5 + r6 + r7 + r8
Heating element 4: r14 + r13 + r12 + R4 + r5 + r6 + r7 + r8
Heating element 5: r14 + r13 + r12 + r11 + R5 + r6 + r7 + r8
Heating element 6: r14 + r13 + r12 + r11 + r10 + R6 + r7 + r8
Heating element 7: r8 + R7 + r9

Assuming that the resistivityes of the conductors 338c2, 338c1, 338d, 338e and the common conductor 338f are the same, the conductor of the resistance pattern 332b at the left end is longer than the conductor of the resistance pattern 332c at the right end, so that the resistance value is larger by (r2 + r3 + r4 + r5 + r6 + r7). turn into. Therefore, with the switch SW2 turned on, the resistance pattern 332b at the left end has a relatively smaller heat generation amount than the resistance pattern 332c at the right end, and the heat generation amount at both ends varies.

Similarly, the five resistors 332a-1 to 332a-5 in the center have longer conductors than the resistance pattern 332c at the right end, so that the resistance value becomes large. Therefore, when the switches SW1 and SW2 are turned on, the heat generation amount of each of the resistors 332a-1 to 332a-5 is smaller than that of the resistance pattern 332c at the right end, and the heat generation amount varies in the longitudinal direction.

Therefore, as shown in FIG. 7A, in the common conductor 338c and the conductor 338f, the conductors 338c1 and 338f1 connected to the resistors 332a-1 to 332a-5, 332b and 332c have lower resistance than the other conductors. Specifically, as shown in FIG. 7A, the width of the conductors 338c1 and 338f1 is widened.

Instead of widening the conductors 338c1 and 338f1, or in combination with widening, the height (thickness) of the conductor may be increased (thickened), or a material having a low resistivity may be used for the conductors 338c1 and 338f1. can. This makes it possible to prevent heat generation variations of the resistors 332a-1 to 332a-5, 332b, and 332c.

This idea is also applied to the heater member 330 of FIGS. 6A and 6B described above, and by forming the main body portion 338f1 of the common conductor 338f wider than the right end portion 338f2, the variation in the amount of heat generated in the longitudinal direction can be varied. It can be suppressed. Since the branch portion 338f3 is short, the influence on the heat generation variation is small even if the resistance value is ignored.

As described above, in the conventional heater member 330'in FIG. 7A, among the total of seven resistors 332a-1 to 332a-5, 332b, 332c, all the resistances other than the resistance pattern in which the thermistors TM1 and TM2 are arranged. Basically, thermostats TH1 to TH5 are arranged in each pattern. That is, in the heater member 330', five resistance bodies 332a-1 to 332a-5 connected in parallel are arranged in the longitudinal direction in the region corresponding to the central resistance pattern 332a. Therefore, basically, the temperature detection member and the safety element must be arranged corresponding to the total number of resistance patterns of 7.

Therefore, the cost of the heater member 330'is increased by the large number of temperature detecting members and safety elements, and the temperature control based on the detected temperatures of the plurality of temperature detecting members is complicated. On the other hand, in the present embodiment of FIGS. 6A and 6B, since the heat generating portion of the heater member 330 is formed by the first and second resistance patterns 332a to 332c, the number of safety elements is at least two and the temperature is high. The number of detection members may be at least three, and the total number of safety elements and thermistors can be reduced by two as compared with FIG. 7A.

That is, one thermostat TH1 and one thermistor TM1 are provided in, for example, the center (within the minimum paper width) in the region of the first resistance pattern 332a, and the thermostat TH1 and the thermistor TM1 are separately provided at one end (outside the minimum paper width) in the region of the first resistance pattern 332a. Thermistor TM2 is installed. Further, one thermostat TH2 is installed at an arbitrary location in the region of either the left or right resistance pattern (resistance pattern 332c), and one thermistor TM3 is installed at an arbitrary location within the region of the opposite resistance pattern (resistance pattern 332b). All you have to do is provide it. Therefore, the heater member 330 can be made space-saving, lightweight, and low-cost.

(Other types of fixing device)

The present invention can be applied to the fixing device 300 as shown in FIGS. 8 and 9 in addition to the fixing device 300 described above. In the fixing device 300 shown in FIG. 8, a pressing roller 370 is arranged on the side opposite to the pressing roller 320 side with respect to the fixing belt 310, and the fixing belt 310 is sandwiched between the pressing roller 370 and the heater member 330. It is configured to heat with.

On the other hand, on the pressure roller 320 side, the nip forming member 380 is arranged on the inner circumference of the fixing belt 310. The nip forming member 380 is supported by the stay 350, and the nip N is formed by sandwiching the fixing belt 310 between the nip forming member 380 and the pressure roller 320.

In the fixing device 300 shown in FIG. 9, a pressure belt 390 is provided in addition to the fixing belt 310, and the heating nip (first nip) N1 and the fixing nip (second nip) N2 are separately configured. That is, the nip forming member 380 and the stay 381 are arranged on the side opposite to the fixing belt 310 side with respect to the pressure roller 320, and the pressure belt 390 is rotated so as to include the nip forming member 380 and the stay 381. Arranged as possible.

Then, the paper P is passed through the fixing nip N2 between the pressure belt 390 and the pressure roller 320, heated and pressed to fix the image. Others have the same configuration as the fixing device 300 shown in FIG. 2B.

Although the various heater members 330 and the fixing device 300 have been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, as the temperature detecting member of the above embodiment, a semiconductor whose resistance value changes according to a temperature change such as a thermistor may be used, or a diode, a transistor or the like which uses a characteristic value change due to a temperature characteristic may be used.

Further, the current cutoff member is not limited to the thermostat, and a thermal fuse, a thermal protector, or the like can be used instead of the thermostat. Further, the first resistance pattern 332a of the embodiment can be formed of five or more rows of resistors extending in the longitudinal direction of the base material 331.

Further, the heater member according to the present invention can be applied not only to a type fixing device that directly heats a thin-walled fixing belt, but also to a heat roller type fixing device in which a heater member is arranged on the inner circumference. Further, the heater member according to the present invention is not applied only to the fixing device. For example, the heater member according to the present invention can be applied to a drying device mounted on an inkjet image forming apparatus and a heater of an inkjet print head in order to dry the ink applied to the paper.

Further, the heater member according to the present invention can also be applied to a coating device (laminator) that thermocompression-bonds a film as a coating member to the surface of the sheet material while transporting a sheet material such as paper by a belt member. Further, the heater member according to the present invention is applicable not only to the belt heating device for heating the belt member but also to the heating device not provided with the belt member.

Further, the number of the first resistors 332a1 to 332a4 of the first resistance pattern 332a can be increased or decreased as necessary. Further, only one first resistance pattern 332a is arranged in the central portion in the longitudinal direction of the base material 331, and a plurality of patterns can be arranged in the longitudinal direction. For example, the first resistance pattern 332a may be arranged in a number of conventional resistance patterns or less. Can be done.

1Y, 1M, 1C, 1Bk: Image forming unit 2: Photoreceptor (image carrier)
3: Charging device 4: Developing device 4a: Developer carrier 5: Drum cleaning device 5a: Cleaning blade 6: Exposure device 6a: Mirror 7: Paper feeding device 8: Transfer device 10: Paper ejection device 11: Intermediate transfer belt 12 : Primary transfer roller 13: Secondary transfer roller 14: Paper transfer path 15: Timing roller 50: Paper feeding device 60: Paper feed roller 100: Image forming device 103: Image forming device main body 250: Resist roller pair 300: Fixing device 310: Fixing belt 320: Pressurized roller 321: Iron core metal 321: Core metal 322: Elastic layer 323: Demolding layer 330, 330': Heater member 331: Base material 332: Resistance pattern 332a: First resistance pattern 332a1 332a4: First resistor 332b, 332c: Second resistance pattern 336: Coating 344: Heater holder 350: Stay 360: Heater base material 370: Pressing roller 380: Nip forming member 381: Stay 390: Pressurized belt 332 : Resistance pattern 332a: First resistance pattern 332a1 to 332a4: First resistor 333: Insulation layer 334, 335: Insulation glass 337a to 337f: Electrode 338a to 338f: Conductor Lb: Laser light N: Nip P: Paper PW :Power supply
SW1, SW2: Switch TM1 to TM3: Thermistor (temperature detection member)
TH1 to TH5: Thermostat (current cutoff member) T: Transfer means

Japanese Patent No. 6336026 Japanese Unexamined Patent Publication No. 2016-6499 Japanese Patent No. 6228458

Claims (19)

It has a plurality of rows of resistors formed in the longitudinal direction of the substrate and generates heat by energization, and the plurality of rows of resistors are connected in parallel in a state of being separated from each other in the lateral direction orthogonal to the longitudinal direction of the substrate. Resistance pattern and
A first temperature detecting member, which is arranged so as to straddle at least two rows or more of the resistors in the lateral direction and detects the temperature of the resistors of the at least two rows or more.
A second, which is arranged over at least two rows or more including a resistor different from the resistor detected by the first temperature detecting member in the lateral direction, and detects the temperature of the at least two rows or more of the resistors. 2 temperature detection members and
A heater member characterized by having. The heater member according to claim 1, wherein the resistor is continuously formed linearly in the longitudinal direction of the base material. The heater member according to claim 1 or 2, wherein the temperature detecting member is urged toward the base material by an elastic member. It is characterized in that a current cutoff member that cuts off the power supply to the resistance pattern when the temperature of any of the plurality of rows of resistors reaches the high temperature threshold value is arranged over the entire row of the resistors. The heater member according to any one of claims 1 to 3. It has a heating member and a pressurizing member that have a longitudinal direction and are pressed against each other to form a nip. The heating member is in contact with the heater member according to claim 4 to be heated, and the sheet material is passed through the nip. In a heating device that transfers heat from the heating member to the sheet material
The first temperature detecting member is arranged within the range of the minimum width size of the sheet material and upstream of the sheet material in the paper passing direction, and the second temperature detecting member is the most of the sheet material. A heating device that is outside the range of the narrow size and is arranged on the downstream side of the sheet material in the paper passing direction with respect to the first temperature detecting member. The heating device according to claim 5, wherein the current cutoff member and the temperature detecting member are arranged on the side of the heater member of claim 4 opposite to the side in contact with the heating member. A flexible sleeve-shaped rotating member and
The heater member according to any one of claims 1 to 4, which is in sliding contact with the inner circumference of the rotating member.
It has a pressurizing member that sandwiches the rotating member and presses against the heater member to form a nip between the rotating member and the heater member.
A heating device characterized in that heat of the heater member is transferred to the sheet material via the rotating member when the sheet material is sandwiched and conveyed by the nip. A fixing device comprising the heating device according to claim 7, wherein a toner image carried on the sheet material is passed through the nip and fixed by heating. An image forming apparatus including a paper feeding device, an image forming unit, a transfer device, and a fixing device according to claim 8. A heater member having three or more resistance patterns having a resistor that generates heat when energized in the longitudinal direction of the base material.
The first resistance pattern formed in the center of the substrate in the longitudinal direction has a plurality of rows of first resistors formed in the longitudinal direction of the substrate, and the first resistors in the plurality of rows are present. They are connected in parallel in a state of being separated from each other in the lateral direction orthogonal to the longitudinal direction of the substrate.
A first temperature detecting member, which is arranged so as to straddle at least two rows or more of the first resistors in the lateral direction and detects the temperature of the first resistors in the two rows or more.
The first resistor in the two or more rows is arranged so as to include a first resistor different from the first resistor detected by the first temperature detecting member in the lateral direction. A heater member characterized in that a second temperature detecting member for detecting the temperature of the resistor is provided. The heater member according to claim 10, wherein the first resistor is continuously formed linearly in the longitudinal direction of the base material. A current cutoff member that cuts off the power supply to the resistance pattern when the temperature of any of the first resistors in the plurality of rows reaches the high temperature threshold is arranged across the entire row of the first resistors. The heater member according to claim 10 or 11, wherein the heater member is provided. The second resistance pattern formed at both ends in the longitudinal direction of the base material has a second resistance body that is continuous in a zigzag manner in the lateral direction of the base material, and is characterized in that they are connected in parallel to each other. The heater member according to any one of claims 10 to 12. A third temperature detection member is disposed on at least one of the second resistance patterns, and the first and second resistance patterns are independent based on the detection results of the first to third temperature detection members. The heater member according to claim 13, wherein the heater member is turned on and off. A third temperature detection member is arranged on at least one of the second resistance patterns, and the first and second resistance patterns are energized and cut off at the same time as the first control of independently energizing and shutting off. The heater member according to claim 13, wherein the second control can be switched. When the third temperature detecting member is arranged on one of the second resistance patterns and the temperature of the second resistance pattern reaches the high temperature threshold on the other second resistance pattern, both of them. The heater member according to claim 13, wherein a second current cutoff member that cuts off the power supply to the second resistance pattern is provided. A flexible sleeve-shaped rotating member and
The heater member according to any one of claims 10 to 16, which is in sliding contact with the inner circumference of the rotating member.
It has a pressurizing member that sandwiches the rotating member and presses against the heater member to form a nip between the rotating member and the heater member.
When a small-sized sheet material having a sheet width corresponding to the longitudinal width of the first resistance pattern is sandwiched and conveyed by the nip, the heat of the first resistance pattern is transferred to the small size through the rotating member. When transferring heat to the sheet material and sandwiching and transporting a large-sized sheet material having a sheet width corresponding to the sum of the longitudinal width of the first resistance pattern and the longitudinal width of both the second resistance patterns. A heating device characterized in that heat of the first and second resistance patterns is transferred to the large-sized sheet material via the rotating member. A fixing device comprising the heating device according to claim 17, wherein a toner image carried on the small-sized sheet material or the large-sized sheet material is passed through the nip and fixed by heating. An image forming apparatus including a paper feeding device, an image forming unit, a transfer device, and a fixing device according to claim 18.

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