JP5375512B2 - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the temperature of a heat roller from becoming too high; and also to prevent an increase in cost. <P>SOLUTION: The heat roller 71 has, in the inside thereof: a first heat generation part 711a extending in one direction; and a second heat generation part 712a which is disposed in nearly parallel to the first heat generation part 711a and is longer than the first heat generation part 711a. A first temperature detection sensor 74 is disposed in the vicinity of the first heat generation part 711a in the longitudinal direction of the heat roller 71. A second temperature detection sensor 75 and a third temperature detection sensor 76 are disposed in the vicinity of a position, where the first heat generation part 711a is not disposed, in the longitudinal direction of the heat roller 71. When all of the first, second and third temperature detection sensors 74, 75 and 76 detect the temperature equal to or less than the predetermined threshold, a temperature controller 77 for the heat roller has an operation control part 772 configured to control the first and second heat generation parts 711a and 712a so that the second heat generation part 712a may generate the heat and the first heat generation part 711a may not generate the heat in the standby period for fixing operation. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device having a heating member having two heat generating portions having different lengths and fixing an image on a sheet, and an image forming apparatus provided with the fixing device. .

  In general, some electrophotographic image forming apparatuses include an image forming unit, a fixing device, a paper transport unit, and a discharge unit.

  In this image forming apparatus, an image is formed on a sheet by an image forming unit, and the sheet on which the image is formed is conveyed to a fixing device by a sheet conveying unit. The image is fixed on the sheet by the fixing device. The sheet on which the image is fixed is conveyed to the discharge unit by the sheet conveying unit. The sheet conveyed by the sheet conveying unit is discharged from the discharge unit to the outside of the image forming apparatus.

  Here, the fixing device includes a heating roller that heats the image on the paper and a pressure roller that presses the image on the paper.

  In this fixing device, when the image is fixed on the paper, the paper on which the image is formed is passed between the heating roller and the pressure roller. At this time, the developer image on the sheet is melted by the heating roller and the image is pressed between the pressure roller and the heating roller. When the paper passes between the heating roller and the pressure roller, the temperature of the paper is lower than the temperature of the heating roller, so the temperature of the part of the heating roller that is in contact with the paper is higher than the temperature of the part that is not in contact. Lower. If the temperature of the portion corresponding to the paper passing portion of the heating roller is lowered, there is a possibility that the developer image cannot be sufficiently melted in the next fixing operation.

  In order to solve such problems, a heating roller having a heating part extending in the entire longitudinal direction of the heating roller and a short heating part disposed in the vicinity of the central part in the longitudinal direction of the heating roller through which almost all paper passes. A fixing device having the above-described configuration has been considered (see Patent Document 1).

  In such a fixing device, in order to control the temperature of the two heat generating portions, a temperature detection sensor disposed in a portion where the two heat generating portions overlap in the longitudinal direction and a portion where the two heat generating portions do not overlap. It has a temperature detection sensor.

JP 2002-251100 A

  The conventional apparatus has two temperature detection sensors. However, if one of the temperature sensors fails, the temperature cannot be controlled. At this time, the temperature of the heating roller cannot be controlled, and the temperature of the heating roller may increase excessively. If the temperature of the heating roller rises too much, the pressure roller arranged to face the heating roller may melt.

  Thus, in order to prevent temperature control from being disabled when one of the sensors fails, two temperature detection sensors are arranged in the overlapping portion of the two heat generating portions in the longitudinal direction, and the two heat generating portions overlap. It is conceivable to arrange two temperature detection sensors in a portion where they do not match. However, in such an arrangement, a total of four temperature detection sensors are required, and a cost and a space for arranging the four temperature detection sensors are further required.

  An object of the present invention is to prevent the heating roller from becoming too hot and to prevent the cost from increasing.

  A fixing device according to a first aspect of the present invention is a fixing device that is used in an image forming apparatus and fixes an image on a sheet, and includes a heating member, a pressure member, a first temperature detection sensor, a second temperature detection sensor, and a second temperature detection sensor. A three-temperature detection sensor and a control unit are provided. The heating member includes a first heat generating portion extending in one direction and a second heat generating portion that is disposed substantially parallel to the first heat generating portion and is longer than the first heat generating portion. The pressurizing member is disposed so as to face the heating member, and pressurizes the image on the paper with the heating member. The first temperature detection sensor is disposed in the vicinity of the first heat generating portion in the longitudinal direction of the heating member. The 2nd temperature detection sensor and the 3rd temperature detection sensor are arranged near the position where the 1st exothermic part is not arranged in the longitudinal direction of a heating member. The control unit causes the second heat generating unit to generate heat when waiting for the fixing operation when all of the first temperature detecting sensor, the second temperature detecting sensor, and the third temperature detecting sensor detect a temperature equal to or lower than a predetermined threshold. In addition, there is an operation control means for controlling the first heat generating part and the second heat generating part so that the first heat generating part does not generate heat.

  In this fixing device, the temperature of the heating member is raised by using both the first heat generating part and the second heat generating part during a fixing operation. At this time, the temperature of the heating member is detected by the first temperature detection sensor, the second temperature detection sensor, and the third temperature detection sensor. On the other hand, at the time of waiting for the fixing operation, the second heat generating portion is caused to generate heat and the first heat generating portion is not caused to generate heat. At this time, the temperature of the heating member is detected by the second temperature detection sensor and the third temperature detection sensor. Here, the threshold is set to a high temperature that cannot increase in a normal state. For this reason, when the temperature detection sensor detects a temperature equal to or higher than the threshold value, it can be considered that an abnormality has occurred in the temperature detection sensor.

  Here, during the fixing operation, the temperature of the heating member rises by setting or controlling by the user so that the heat generation operation is terminated when the temperature of either the second temperature detection sensor or the third temperature detection sensor exceeds a predetermined threshold value. It can be prevented from doing too much. Here, since the temperature of the portion in contact with the paper is lowered by the paper, the temperature does not rise excessively even if the temperature is not detected. In addition, since the first heat generating unit is controlled not to generate heat during standby for the fixing operation, the heat generating operation is performed when the temperatures detected by the second temperature detecting sensor and the third temperature detecting sensor are equal to or higher than a predetermined threshold. It is possible to prevent the temperature of the heating member from rising too much above a predetermined threshold, for example, by setting so as to be terminated or by the user shutting off power. As described above, it is possible to prevent the temperature from excessively rising even during the fixing operation using the three temperature detection sensors or during the standby of the fixing operation. Furthermore, compared with the case where four temperature detection sensors are used, it can prevent that cost becomes high and can prevent that the space which arrange | positions a temperature detection sensor becomes large. That is, an increase in the size of the apparatus can be prevented. For this reason, it is possible to prevent the pressure member from melting due to the temperature of the heating member rising excessively.

  A fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the control unit includes a determination unit and a stop unit. The determination unit determines whether any one of the first temperature detection sensor, the second temperature detection sensor, and the third temperature detection sensor has detected a temperature equal to or higher than a predetermined threshold value. The stopping unit is configured to detect the first heat generating unit and the second heat generating unit when the determining unit determines that any one of the first temperature detecting sensor, the second temperature detecting sensor, and the temperature third detecting sensor has a temperature equal to or higher than a predetermined threshold. Stop heating the part.

  In this fixing device, it is determined whether the detected temperatures of the first temperature detection sensor, the second temperature detection sensor, and the third temperature detection sensor are equal to or higher than a predetermined threshold value, and any one or more temperature detection sensors are set to the predetermined threshold value. When the above temperature is detected, the heat generating operation of the first heat generating unit and the second heat generating unit is stopped.

  Here, since the heating operation is stopped when at least one of the three temperature detection sensors detects a predetermined temperature or higher, the heating member can be prevented from reaching a temperature equal to or higher than a predetermined threshold.

  A fixing device according to a third aspect is the fixing device according to the first or second aspect, wherein the operation control unit causes the first heat generating unit and the second heat generating unit to generate heat during the fixing operation so that the first heat generating unit and the second heat generating unit generate heat. Control the heat generating part.

  Here, when the operation of fixing the image on the sheet is performed, the temperature of the heating member can be raised in a short period of time by causing the first heat generating portion and the second heat generating portion to generate heat. In addition, the first heat generating portion and the second heat generating portion are parallel to each other at the location where the first heat generating portion is disposed, and the heating member is heated by both the first heat generating portion and the second heat generating portion. However, the temperature of the heating member can be prevented from becoming too high due to contact with the paper. On the other hand, the temperature of the portion where the first heat generating portion and the second heat generating portion are parallel to each other is likely to decrease because of contact with the paper, but since the heat is generated using two heat generating members, the temperature is excessively decreased. Can be prevented. Therefore, it becomes easy to fix the image on the sheet.

  A fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the second heat generating member generates heat so that the temperature of the end portion is higher than the temperature of the substantially central portion in the longitudinal direction.

  Here, the heating member easily dissipates heat from both ends in the longitudinal direction, and the temperature at the end of the second heat generating member is higher than the temperature at the center in the longitudinal direction, so the temperature tends to be uniform in the longitudinal direction.

  A fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the operation control unit is configured to cause the first heat generating unit and the second heat generating unit to generate heat during warm-up. And the second heat generating unit is controlled.

  Here, since both the first heat generating part and the second heat generating part are controlled to generate heat during warm-up, the temperature of the heating member is increased compared to the case where the temperature of the heating member is increased by one heat generating part. It is possible to shorten the time required to make it happen.

  A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the first heat generating portion is disposed at a substantially central portion of the heating member. The second heat generating part is located in substantially the entire region in the longitudinal direction of the heating member. The second temperature detection sensor and the third temperature detection sensor are respectively disposed in the vicinity of both ends in the longitudinal direction of the heating member.

  Here, since the second temperature detection sensor and the third temperature detection sensor are respectively disposed at both ends in the longitudinal direction of the heating member, when one of them is jammed or the like and the paper is moved in contact with the temperature detection sensor Even so, the temperature of the heating member can be detected.

  An image forming apparatus according to a seventh aspect is capable of fixing an image formed on the paper based on the image information, and an image formed by the image forming unit on the paper. And the fixing device described.

  In the present invention, it is possible to prevent the heating roller from becoming too hot and to prevent the cost from increasing.

1 is an overall schematic cross-sectional view of a multifunction machine according to an embodiment of the present invention. The elements on larger scale of a fixing device. The block diagram which shows the temperature control apparatus of a heating roller. The flowchart which shows heating roller temperature control operation | movement. The figure which shows arrangement | positioning of the temperature detection sensor of other embodiment.

[overall structure]
Hereinafter, a multifunction machine 1 as an image forming apparatus according to the present invention will be described with reference to FIG. Here, FIG. 1 shows an overall outline of the multifunction machine 1 according to the present invention. The multifunction device 1 is connected to an external computer or the like, and can form an image on a sheet based on image information read from a document or image information sent from a computer.

  The multifunction device 1 has various functions such as a function of copying a document and a function of transmitting image information of the document. As shown in FIG. 1, the multifunction device 1 includes a document reading unit 2, an image forming unit 3, a transfer unit 4, a sheet storage unit 5, a sheet transport unit 6, a fixing device 7, and a discharge unit 8. It has. The configuration of each functional unit will be described below. The fixing device 7 will be described in detail later.

{Original reading unit}
The document reading unit 2 is a part for reading image information of a document. The document reading unit 2 is disposed at the top of the multifunction device 1.

{Image forming part}
The image forming unit 3 is a part for forming an image on a sheet based on image information. The image forming unit 3 is disposed below the document reading unit 2. Further, the image forming unit 3 includes four image forming units 30. The four image forming units 30 are arranged in a line. Each of the four image forming units 30 includes a photosensitive drum 31, a charging device 32, a laser unit 33, a developing device 34, a toner storage unit 35, a charge eliminating device 36, and a drum cleaning device 37. doing. The four image forming units 30 can form yellow, magenta, cyan, and black toner images in order from the left side of FIG. The image forming units 30 have the same configuration. Therefore, the yellow image forming unit 30 will be described, and the description of the other image forming units 30 will be omitted.

  The photosensitive drum 31 is a member capable of carrying an electrostatic latent image on the surface. Further, the photosensitive drum 31 is rotatable around a rotation axis extending perpendicularly to the paper surface of FIG. The photosensitive drum 31 is disposed so as to contact a transfer belt 41 described later.

  The charging device 32 is a device for uniformly charging the surface of the photosensitive drum 31. The charging device 32 is disposed below the photosensitive drum 31.

  The laser unit 33 is a device for irradiating the surface of the photosensitive drum 31 with laser light based on image information. The laser unit 33 is disposed below the photosensitive drum 31.

  The developing device 34 is a device capable of supplying a developer to the electrostatic latent image carried on the photosensitive drum 31. Further, each developing device 34 is arranged on the upper side of each laser unit 33. Further, the developing device 34 includes a developing container 341, a developing roller 342, and a supply roller 343.

  The developing container 341 is a container that can store a developer of a color corresponding to each photosensitive drum 31 therein.

  The developing roller 342 is a member for supplying a developer to the photosensitive drum 31. The developing roller 342 is supported by the developing container 341. Further, the developing roller 342 is disposed so as to face the photosensitive drum 31.

  The supply roller 343 is a member for supplying the developer inside the developing container 341 to the developing roller 342. Further, the supply roller 343 is rotatably supported by the developing container 341. Further, the supply roller 343 is disposed in parallel with the developing roller 342.

  The toner storage portion 35 is a portion for storing toner that can be supplied to the developing device 34. The toner storage unit 35 includes a toner container 351 that can store toner corresponding to the color of each developing device 34. The toner container 351 is connected to the developing device 34 by a supply path (not shown).

  The static eliminator 36 is a device for removing charges on the surface of the photosensitive drum 31. The static eliminator 36 is disposed below the photosensitive drum 31.

  The drum cleaning device 37 is a device for cleaning the developer remaining on the photosensitive drum 31 without being used for the developing operation. The drum cleaning device 37 includes a blade member 371 that contacts the surface of the photosensitive drum 31, and a waste developer storage container 372 that can store toner scraped off by the blade member 371.

{Transcription part}
The transfer unit 4 includes a transfer belt 41, four primary transfer rollers 42, a secondary transfer roller 43, and a belt cleaning device 44.

  The transfer belt 41 is a member for transferring the toner image formed by the image forming unit 3 to a sheet. The transfer belt 41 is a member to which a toner image is primarily transferred from the photosensitive drum 31. Further, the transfer belt 41 is disposed on the upper side of the photosensitive drum 31.

  The primary transfer roller 42 is a member for transferring the toner image on the photosensitive drum 31 onto the transfer belt 41. The primary transfer roller 42 is disposed so as to face the photosensitive drum 31 with the transfer belt 41 interposed therebetween. Further, each primary transfer roller 42 is connected to a voltage application device (not shown). Each primary transfer roller 42 is arranged in parallel with the direction in which the photosensitive drums 31 are arranged.

  The secondary transfer roller 43 is a member for transferring the toner image primarily transferred from the photosensitive drum 31 to the transfer belt 41 onto a sheet. The secondary transfer roller 43 is disposed so as to face the transfer belt 41 with the paper transport path of the paper transport unit 6 interposed therebetween.

  The belt cleaning device 44 is a device for cleaning toner, paper dust, dust and the like on the transfer belt 41. The belt cleaning device 44 is disposed on the left side of the transfer belt member 41 in FIG.

{Paper storage}
The paper storage unit 5 is a part for storing paper. The paper storage unit 5 is disposed at the lower part of the multifunction machine 1. Further, the paper storage unit 5 has a plurality of paper feed cassettes 51. Each paper cassette 51 stores different types (sizes, etc.) of paper. A plurality of paper feed cassettes 51 are stacked.

{Paper transport section}
The paper transport unit 6 is a part for transporting paper to each functional unit. The paper transport unit 6 has a paper transport path for transporting paper in the order of the paper storage unit 5, the image forming unit 4, the fixing device 7, and the discharge unit 8. The paper transport unit 6 includes a paper transport guide pair 61 and a plurality of paper transport roller pairs 62.

  The paper transport guide pair 61 is a member for guiding the paper transport direction. The paper transport guide pair 61 has plate-like members arranged so as to face each other. A sheet can pass between these plate-like members.

  The paper transport roller pair 62 is a member for transporting paper in the paper transport direction. The pair of paper transport rollers 62 has two rollers arranged to face each other. The sheet can pass between the two rollers.

{Discharge unit}
The discharge unit 8 is a part for discharging the sheet to the outside of the multifunction device 1. As shown in FIG. 1, the discharge unit 8 is disposed downstream of the fixing device 7 in the sheet conveyance direction. The discharge unit 8 has a discharge roller 81. The discharge unit 8 is disposed below the document reading unit 3. The discharge unit 8 further includes a recess 82 that is recessed rightward from the left side surface of the multifunction device 1 in FIG. Then, the sheet is discharged into the recess 82.

[Fixing device]
The fixing device 7 is a part for fixing an image on a sheet. As shown in FIG. 3, the fixing device 7 includes a fixing unit 78 and a heating roller temperature control device 77.

  As shown in FIG. 2, which is a partially enlarged view of the fixing unit 78, the fixing unit 78 includes a heating roller 71, a pressure roller 72, a frame 73 (see FIG. 1), a first temperature detection sensor 74, 2 temperature detection sensor 75 and 3rd temperature detection sensor 76 are provided.

  The heating roller 71 is a member for melting the toner image. The heating roller 71 is a member that extends in one direction, specifically, a direction orthogonal to the paper surface of FIG. Further, the heating roller 71 is rotatably supported by the frame 73. The heating roller 71 has a first heat generating member 711 and a second heat generating member 712 inside.

  The first heat generating member 711 is a member that extends in the axial direction of the heating roller 71. Further, the first heat generating member 711 has a first heat generating portion 711 a located at a substantially central portion in the axial direction of the heating roller 71. The first heat generating portion 711 a is about half the length of the heating roller 71. For this reason, both ends of the first heat generating portion 711 a are located inside the both ends of the heating roller 71. The first heat generating portion 711a is formed by a conductive wire wound in a coil shape. Here, the heat generating portion means a portion that generates heat to heat the entire roller, for example, a portion in which a conducting wire is wound in a coil shape like the first heat generating portion 711a in FIG. 2 to generate heat. It does not mean a place with only a straight conducting wire.

  The second heat generating member 712 is a member that extends in the axial direction of the heating roller 71. Further, the second heat generating member 712 is disposed substantially parallel to the first heat generating member 711. Further, the second heat generating member 712 has a second heat generating portion 712 a that extends almost in the entire axial direction of the heating roller 71. Accordingly, a part of the second heat generating portion 712a is disposed substantially parallel to the first heat generating portion 711a. The second heat generating portion 712a is formed by a conducting wire wound in a coil shape. And both ends of the second heat generating part 712a are higher in density than the central part in the longitudinal direction. For this reason, when the second heat generating portion 712a generates heat, the amount of heat generated at both ends is greater than the amount of heat generated at the central portion.

  The frame 73 is a member for supporting the heating roller 71 and the pressure roller 72. The frame 73 is made of sheet metal. Further, the frame 73 includes a first frame 73 a that can support the heating roller 71 and a second frame 73 b that supports the pressure roller 72. The first frame 73a and the second frame 73b are connected to each other by an elastic member (not shown). The pressure roller 72 is elastically pressed against the heating roller 71 by the elastic force of the elastic member (not shown). Further, a cover (not shown) is provided outside the frame 73 so as not to let the heat of the heating roller 71 escape. Further, the frame 73 is supported by a frame member (not shown) of the multifunction machine 1.

  The first temperature detection sensor 74 is heated by the first heat generating part 711a and the second heat generating part 712a of the heating roller 71 (the part where the first heat generating part 711a and the second heat generating part 712a are substantially parallel). ) Is a member for detecting the temperature in the vicinity. The first temperature detection sensor 74 is disposed in the vicinity of the first heat generating portion 711a. Further, the first temperature detection sensor 74 is located in the vicinity of the substantially central portion of the heating roller 71 in the axial direction. Further, the first temperature detection sensor 74 is supported by the frame 73. The first temperature detection sensor 74 is a sensor that can detect the temperature without contact. Here, the vicinity means a place where the temperature rises as the temperature of the heat generating part in the vicinity increases.

  The second temperature detection sensor 75 is a member for detecting the temperature near the end of the heating roller 71. For this reason, the 2nd temperature detection sensor 75 detects the temperature of the location currently heated only by the 2nd heat generating part 712a. The second temperature detection sensor 75 is supported by the frame 73. Further, the second temperature detection sensor 75 is a sensor that can detect the temperature in a non-contact manner, similarly to the first temperature detection sensor 74.

  The third temperature detection sensor 76 is a member for detecting the temperature in the vicinity of the end of the heating roller 71 on the side where the second temperature detection sensor 75 is not disposed. For this reason, the 3rd temperature detection sensor 76 detects the temperature of the location currently heated only by the 2nd heat generating part 712a. The third temperature detection sensor 76 is supported by the frame 73. Further, the second temperature detection sensor 75 is a sensor that can detect the temperature in a non-contact manner, similarly to the first temperature detection sensor 74.

  The heating roller temperature control device 77 is a device for controlling the temperature of the heating roller 71. Further, the temperature control device 77 for the heating roller is a device that specifically switches ON / OFF of the power source of the first heat generating member 711 and ON / OFF of the power source of the second heat generating member 712, respectively. Further, the temperature control device 77 of the heating roller is connected to each functional unit such as the fixing unit 78 and the image forming unit 3. FIG. 3 is a block diagram of the temperature control device 77 for the heating roller. The heating roller temperature control device 77 will be described below with reference to the block diagram of FIG.

  The heating roller temperature control device 77 includes a storage unit 771 and a CPU. Further, in the temperature control device 77 for the heating roller, the CPU executes control as an operation control unit 772, a determination unit 773, and a stop unit 774 by executing a program. Further, the heating roller temperature control device 77 is a device capable of controlling the operation of each functional unit by executing a program.

  The storage unit 771 is a part capable of storing various programs. In addition, the storage unit 771 stores temperature threshold values detected by the first temperature detection sensor 74, the second temperature detection sensor 75, and the third temperature detection sensor 76. Specifically, the threshold is set to 250 degrees.

  The operation control unit 772 is a part that switches between ON / OFF of the power source of the first heat generating member 711 and ON / OFF of the power source of the second heat generating member 712. The operation control unit 772 controls (ON / OFF) a power source (not shown) so that both the first heat generating member 711 and the second heat generating member 712 generate heat during warm-up. Further, a power source (not shown) is controlled so that the first heat generating member 771 and the second heat generating member 712 generate heat during the fixing operation. Further, the power source is controlled so that the first heat generating member 711 does not generate heat and the second heat generating member 712 generates heat within a predetermined temperature range when waiting for the printing operation, that is, when waiting for the fixing operation.

  The determination unit 773 uses the threshold values at which the temperature detected by the first temperature detection sensor 74, the temperature detected by the second temperature detection sensor 75, and the temperature detected by the third temperature detection sensor 76 are stored in the storage unit 71. This is the part that determines whether or not the number has been exceeded.

  When the determination unit 773 determines that the temperatures detected by the first temperature detection sensor 74, the second temperature detection sensor 75, and the third temperature detection sensor 76 exceed the threshold value, the stop unit 774 detects the first heating member. 711 and the second heat generating member 712 are parts for stopping the power supply so as not to generate heat.

[Operation]
Next, the operation of the multifunction device 1 will be described.

  When image information of an original is read by the original reading unit 2 or image information is sent from a computer connected to the outside of the multifunction machine 1, an electrostatic latent image is formed on the photosensitive drum 31 based on the image information. . Specifically, the surface of the photosensitive drum 31 is charged by the charging device 32, and laser light is irradiated from the laser unit 33 to the photosensitive drum 31 based on the image information. When the electrostatic latent image is formed on the photosensitive drum 31 in this way, the developer is supplied from the developing roller 342 of the developing device 34 to the electrostatic latent image. When the developer is supplied from the developing device 34 to the electrostatic latent image, a toner image is formed on the photosensitive drum 31.

  Then, the toner image on each photosensitive drum 31 is transferred to the transfer belt 41. Then, the toner image on the transfer belt 41 is transferred to a sheet. The sheet on which the toner image is transferred is conveyed to the fixing device 7 by the sheet conveying unit 6. After the toner image is fixed on the paper by the fixing device 7, the toner image is conveyed to the discharge unit 8. The sheet conveyed to the discharge unit 8 is discharged out of the multifunction machine 1.

[Temperature control operation of heating roller]
A flowchart showing the temperature control operation of the heating roller is shown in FIG. The temperature control operation of the heating roller will be described with reference to FIG.

  When the power is turned on, a warm-up operation is performed (S1). At this time, power is supplied to both the first heat generating member 711 and the second heat generating member 712. And if the 1st temperature detection sensor 74, the 2nd temperature detection sensor 75, and the 3rd temperature detection sensor 76 detect 200 degrees, the power supply of the 1st exothermic member 711 will be intercepted so that a predetermined temperature range may be maintained, The second heat generating member 712 is repeatedly supplied and shut off.

  It is determined whether a print command has been issued (S2). If no print command has been issued (NO in S2), a standby state is entered (S6). When a print command is issued (YES in S2), both the first heat generating member 711 and the second heat generating member 712 are caused to generate heat (S3). Then, it is determined whether or not the temperatures detected by the three temperature detection sensors 74, 75, and 76 exceed a threshold value (250 degrees) (S4). When it is determined that any one of the three temperature detection sensors 74, 75, 76 exceeds the threshold (YES in S4), the power supply to the first heat generating member 711 and the second heat generating member 712 is cut off. (S8). If it is determined that all three temperature detection sensors 74, 75, 76 do not exceed the threshold (NO in S4), the first heating member is maintained so as to maintain a predetermined temperature range during the printing operation. The supply and interruption of power to 711 and the second heat generating member 712 are repeated.

  When the printing operation (one job) is completed, it is determined again whether a printing command has been issued (S5). When a print command is issued (YES in S5), both the first heat generating member 711 and the second heat generating member 712 are heated (power to maintain the temperature of the heating roller 71 within a predetermined temperature range). The operation from step 3 is repeated. If a print command has not been issued (NO in S5), a standby state is entered (S6). At this time, the power supply of the first heat generating member 711 is interrupted, and the power supply and the power supply of the second heat generating member 712 are repeated so that the temperature of the heating roller 71 falls within a predetermined temperature range. Thereafter, it is determined whether or not the temperatures detected by the three temperature detection sensors 74, 75, and 76 exceed a threshold value (S7). If it is determined that any one of the three temperature detection sensors 74, 75, 76 exceeds the threshold (YES in S7), the power supply to the second heat generating member 712 is shut off (S8). If it is determined that all three temperature detection sensors 74, 75, 76 do not exceed the threshold (NO in S7), the predetermined temperature range is maintained until the next print command is issued. The supply and interruption of power to the first heat generating member 711 and the second heat generating member 712 are repeated (S6).

[effect]
When the printing operation is performed, for example, even when the first temperature detection sensor 74 cannot detect the temperature normally, the sheet is located at the position where the first heat generating member 711 and the second heat generating member 712 overlap in the longitudinal direction. Since the temperature of the contact portion and the contacted portion decreases, the temperature of the heating roller 71 can be prevented from becoming too high. Further, for example, even when one of the second temperature detection sensor 75 and the third temperature detection sensor 76 cannot normally detect the temperature, the other of the second temperature detection sensor 75 or the third temperature detection sensor 76 is the threshold value. When the above temperature is detected, the power supply is shut off so that the first heat generating member 711 and the second heat generating member 712 do not generate heat. For this reason, it can prevent that the temperature of the heating roller 71 becomes too high. Therefore, it is possible to prevent the pressure roller 72 from melting due to the temperature of the heating roller 71 becoming too high.

  Further, at the time of waiting for the printing operation, for example, even when the first temperature detection sensor 74 cannot detect the temperature normally, the temperature of the central portion of the heating roller 71 is not extreme because the first heat generating member 711 does not generate heat. It becomes lower than the temperature of the part. For this reason, when the second temperature detection sensor 76 and the third temperature detection sensor 77 detect a temperature equal to or higher than a predetermined threshold, the temperature of the heating roller 76 is increased by cutting off the power supply to the second heat generating member 712. It can be prevented from becoming too much. Even if one of the second temperature detection sensor 75 and the third temperature detection sensor 76 cannot normally detect the temperature, the other of the second temperature detection sensor 75 or the third temperature detection sensor 76 is not less than the threshold value. When the temperature is detected, the power supply is shut off so that the second heat generating member 712 does not generate heat. For this reason, it can prevent that the temperature of the heating roller 71 becomes too high. Therefore, it is possible to prevent the pressure roller 72 from melting due to the temperature of the heating roller 71 becoming too high.

  For this reason, it is possible to prevent the temperature of the heating roller 71 from becoming too high by using the three temperature detection sensors 74, 75, and 76, at any time during warm-up, printing operation, and standby. For this reason, compared with the case where four or more temperature detection sensors are used, cost can be reduced and the space for arranging the temperature detection sensors can be reduced, and thus the apparatus can be downsized.

  The numerical values, the arrangement, the structure, and the like used in the above embodiment are examples and are not limited to these. Accordingly, modifications can be made as appropriate without departing from the scope of the present invention.

[Other Embodiments]
(A) In the said embodiment, although the 3rd temperature detection sensor was arrange | positioned at the edge part of the side by which the 2nd temperature detection sensor of a heating roller is not arrange | positioned, this invention is not restricted to this, As shown in FIG. In addition, the third temperature detection sensor may be disposed in the vicinity of the side end portion where the second temperature detection sensor is disposed.

  (B) In the above embodiment, the both ends of the second heat generating member are configured to have a higher temperature than the central portion during heat generation. However, the present invention is not limited to this, and the temperature is uniform in the longitudinal direction. A heat generating member may be used.

  (C) In the above embodiment, the multifunction peripheral has been described. However, the present invention is not limited to this, and may be a copying machine, a printer, or the like.

  (D) Further, in the above embodiment, the case where the heating member and the pressure member are rollers has been described. However, the present invention is not limited to this, and other members such as a belt and a pad may be used.

1 MFP (image forming device)
3 Image forming unit 7 Fixing device 71 Heating roller (heating member)
72 Pressure roller (Pressure member)
74 1st temperature detection sensor 75 2nd temperature detection sensor 76 3rd temperature detection sensor 77 Temperature control apparatus (control part) of a heating roller
711a First heat generating unit 712a Second heat generating unit 772 Operation control unit (operation control means)
773 Judgment part (judgment means)
774 Stop part (stop means)

Claims (5)

A fixing device that is used in an image forming apparatus and fixes an image on paper,
A heating member having a first heat generating portion extending in one direction and a second heat generating portion disposed substantially parallel to the first heat generating portion and longer than the first heat generating portion;
A pressure member that is disposed so as to face the heating member and pressurizes an image of a sheet with the heating member;
A first temperature detection sensor disposed in the vicinity of the first heat generating portion in the longitudinal direction of the heating member;
A second temperature detection sensor and a third temperature detection sensor arranged in the vicinity of a position where the first heat generating portion is not arranged in the longitudinal direction of the heating member;
When all of the first temperature detection sensor, the second temperature detection sensor, and the third temperature detection sensor detect a temperature that is equal to or lower than a predetermined threshold, the second heat generating unit is caused to generate heat during standby for a fixing operation. And a control unit having operation control means for controlling the first heat generating unit and the second heat generating unit so that the first heat generating unit does not generate heat .
The controller is
Determination means for determining whether any one of the first temperature detection sensor, the second temperature detection sensor, or the third temperature detection sensor has detected a temperature equal to or higher than a predetermined threshold;
When the determination means determines that any one of the first temperature detection sensor, the second temperature detection sensor, or the temperature third detection sensor has a temperature equal to or higher than a predetermined threshold, the first heat generating unit and the first 2 stop means for stopping the heat generation of the heat generating part,
The fixing device , wherein the second temperature detection sensor and the third temperature detection sensor are respectively disposed on one side in the longitudinal direction of the heating member . The fixing device according to claim 1, wherein the operation control unit controls the first heat generating unit and the second heat generating unit so that the first heat generating unit and the second heat generating unit generate heat during a fixing operation . 3. The fixing device according to claim 1, wherein the second heat generating portion generates heat so that a temperature at an end portion is higher than a temperature at a substantially central portion in a longitudinal direction . The operation control unit controls the first heat generation unit and the second heat generation unit so that the first heat generation unit and the second heat generation unit generate heat during warm-up. Fixing device. An image forming unit capable of forming an image on paper based on image information;
5. The fixing device according to claim 1, wherein the image formed by the image forming unit can be fixed on a sheet,
An image forming apparatus .

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