JP2007256633A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus whose downtime is reduced by detecting the temperature abnormality of a fixing device when recording material is multiply fed so that the fault of the fixing device by heat damage may be prevented in advance, and preventing the erroneous detection of fault from being judged as the occurrence of fault immediately even if the fault of the fixing device is erroneously detected. <P>SOLUTION: The image forming apparatus has a control mode as follows: when detecting the abnormality of the fixing device based on temperature information from a temperature detection means for detecting the temperature of the area of the paper passing part of the fixing device in which the recording material is introduced and temperature information from a temperature detection means for detecting the temperature of the area of the paper non-passing part thereof, the operation of the apparatus is stopped after the recording material is conveyed until it passes through the fixing device; and when judging that the recording material is multiply fed in a recording material supply part, if the recording material is multiply fed for the first time, a display means is informed that it is multiple feed jamming, and if the abnormality of the fixing device is consecutively detected twice after jamming disposal, it is judged as the fault of the fixing device, and the display means is informed of the fault of a heating device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile machine, or a multi-function machine thereof.

  In an image forming apparatus such as an electrophotographic method, an unfixed toner image is formed and supported on a recording material by a transfer method or a direct method in an image forming unit, and the recording material is introduced into the fixing unit and unfixed toner The image is fixed on the recording material as a permanently fixed image.

  As the fixing unit, a heating device represented by a heat roller system using a halogen lamp or a film heating system using a ceramic heater is used, and the recording material is nipped and conveyed while simultaneously applying heat and pressure. As a result, a method of fixing an unfixed toner image on the recording material surface is common.

  Further, if the image forming apparatus supports up to A3 size recording materials, in addition to A3 size recording materials, the widths of B4, A4 horizontal, vertical, A5 horizontal, vertical, B5 horizontal, vertical are narrower than that. In general, recording materials of various sizes such as western envelopes and postcards can be passed.

In the heating apparatus as described above, when continuously passing a recording material having a width smaller than the recording material having the maximum sheet passing width, the temperature gradually increases in a region where the recording material does not pass. The temperature of the paper passing section is increased. Therefore, the temperature detection means is provided at the end of the heating device in the longitudinal direction in the heating device, and the control temperature of the heating means is set so that the temperature of the end that becomes the non-sheet passing portion of the heating means is equal to or lower than the allowable temperature. In addition, control is performed to change the conveyance time interval of the recording material (Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 03-18883 JP 2001-282036 A

  By the way, when a double feed occurs in the feeding of the recording material from the paper feeding unit, based on the double feed detection signal by the double feed detection means without waiting for the double fed recording material to come out to the heating device, Immediately stopping the conveyance of the recording material, the user is prompted to remove the double-fed recording material. However, when the recording material is removed, the heating device may be damaged and destroyed.

  In addition, due to the double feeding of the recording material, an extreme temperature difference may occur between the temperature of the paper passing portion and the temperature of the non-paper passing portion of the heating device. In the case of control, there is a possibility of erroneously detecting a failure of the heating device.

  Therefore, the object of the present invention is to minimize the stress applied to the heating device during the removal processing of the double-fed recording material and the thermal stress on the heating device due to the double feeding of the recording material, and the failure of the heating device. The purpose is to prevent unnecessary services and reduce unnecessary service response due to false detection.

A typical configuration of the image forming apparatus according to the present invention for achieving the above object is as follows:
A recording material feeding unit for feeding the recording material;
Image forming means for forming an unfixed image on a recording material fed from the recording material feeding unit;
A first fixing member and a second fixing member that forms a nip portion in contact with the first fixing member, and a recording material introduced from the image forming unit is nipped and conveyed by the nip portion to perform recording. A heating device for heating and fixing an unfixed image on the material;
Control means for executing device control;
Display means for notifying when an abnormal state occurs in the device;
In an image forming apparatus having
The control means includes temperature information from a temperature detecting means for detecting the temperature of the paper passing portion area of the heating device into which the recording material is introduced, and temperature information from a temperature detecting means for detecting the temperature of the non-paper passing area. When an abnormality of the heating device is detected, the recording material is transported until the recording material passes through the heating device, and then the operation of the device is stopped. When it is determined, when the double feed occurs for the first time, it is notified to the display means as a double feed jam. The display means has a control mode for notifying that the heating device has failed.

  According to the present invention, when a jam occurs due to double feeding, the recording material conveyance is stopped immediately after passing through the heating device without immediately stopping the recording material conveyance, so that the stress when removing jammed paper is stopped. The damage to the heating device due to can be reduced. In addition, notifying the failure only when the heating device really fails leads to a reduction in downtime of the image forming apparatus, thereby improving usability.

(1) Image Forming Unit FIG. 1 is a schematic configuration diagram of an image forming apparatus A in the present embodiment. This image forming apparatus A is a laser beam printer (hereinafter referred to as a printer) using a transfer type electrophotographic process, and supports image formation up to A3 size (vertical feed).

  B is a host device such as a personal computer or image reader as control means for creating image information to be printed. A print request signal / image information is input from the host device B to a control circuit unit (CPU) C as a control means for executing device control of the printer A. The control circuit C develops the input image information and starts image forming sequence control of the printer A.

  That is, a drum-type electrophotographic photosensitive member (hereinafter referred to as a drum) 1 as an image carrier is rotationally driven in a clockwise direction indicated by an arrow at a predetermined speed. Further, the laser scanner 3 as an exposure apparatus is driven. The drum 1 is uniformly charged to a predetermined polarity and potential by the charger 2 during the rotation process. The drum charging surface is subjected to scanning exposure by a laser beam 3a which is modulated and output from the laser scanner 3 in accordance with the above-described development processing image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the drum 1. The electrostatic latent image is developed as a toner image by the developing device 4.

  On the other hand, at a predetermined control timing, one sheet of recording material (paper, sheet) P is separated and fed from the cassette paper feeding unit 7 or the multi-tray paper feeding unit (MP tray: multi-purpose tray) 8, and the conveyance path 9 is conveyed to the position of the registration roller pair 10. The registration roller pair 10 corrects the skew of the recording material P by temporarily receiving the leading end of the recording material P at the nip portion in the rotation stop control state. The registration roller pair 10 is rotationally driven at a predetermined control timing, and feeds the recording material P to a transfer nip T that is a contact portion between the drum 1 and the transfer roller 5.

  S 1 is a top sensor disposed on the recording material outlet side of the registration roller pair 10, detects the leading edge of the recording material P sent out from the registration roller pair 10, and inputs the detection signal to the control circuit unit C. The control circuit C adjusts the image writing timing for the drum 1 based on the recording material leading edge detection signal input from the top sensor S1.

  While the recording material P is nipped and conveyed through the transfer nip T, a transfer bias having a polarity opposite to the charging polarity of the toner is applied to the transfer roller 5. Thus, the toner image on the drum surface is sequentially electrostatically transferred onto the surface of the recording material P. The drum surface after the transfer of the toner image to the recording material P is cleaned by the transfer device 6 after removal of transfer residual toner, paper dust, and the like, and is repeatedly used for image formation.

  The recording material P that has received the transfer of the toner image at the transfer nip T is introduced into the fixing device 12 that is a heating device through the conveyance path 11 and receives the heat fixing of the toner image. When the face-up discharge is selected, the recording material P that has exited the fixing device 12 is guided to the conveyance path 14 side by the flapper 13 and discharged onto the FU tray 16 by the discharge roller 15. When the face-down paper discharge is selected, the recording material P that has exited the fixing device 12 is guided to the reverse conveyance path 17 side by the flapper 13, and the FD trait 20 by the relay roller 18 and the paper discharge roller 19. Is discharged. S2 is a fixing paper discharge sensor disposed on the recording material outlet side of the fixing device 12, and detects the passage of the leading edge and the trailing edge of the recording material P passing through the fixing device 12, and the detection signal is input to the control circuit section C. .

  In the printer A of the present embodiment, the cassette sheet feeding unit 7 is equipped with the first to third three sheet feeding cassettes 71 to 73 and is selectively used. In each sheet feeding cassette, recording materials P having different sizes are stacked and stored. The pickup roller 74 of the paper feed cassette in which the recording material P of the selected designated size is stored is driven, and the recording material P is separated and fed from the paper feed cassette. From the cassette paper feeding unit 7, regular plain paper is mainly fed as the recording material P.

  When paper feeding from the multi-tray paper feeding unit 8 is selected and designated, the multi-tray pickup roller 81 is driven, and the recording material P set on the multi-tray is separated and fed one sheet. From the multi-tray, as the recording material P, special paper such as narrow postcards and envelopes, regular or irregular thick letters, and OHP sheets are fed. Of course, regular plain paper can also be fed.

  Here, the width or the sheet passing width of the recording material is a recording material dimension in a direction orthogonal to the recording material conveyance direction on the recording material surface. In this printer A, the standard for passing the recording material P of various width sizes is that the feeding / conveying from the cassette feeding unit 7 and the feeding / conveying from the multi-tray feeding unit 8 are centered on the recording material width. Central standard.

  FIG. 2 is a plan view of the multi-tray paper feeding unit 8. Reference numerals 82 and 82 denote a pair of recording material side surface regulating plates (side guides: hereinafter referred to as paper regulating plates) arranged in parallel on the left and right sides on the multi-tray. The paper restricting plates 82 and 82 can slide in the recording material width direction on the multi-tray. When one of the paper restricting plates 82 is moved in the paper width direction, an interlocking mechanism (not shown) such as a rack and pinion mechanism is provided. Accordingly, the other paper restricting plate 82 moves in the opposite direction by the same distance. Accordingly, the interval between the paper regulating plates 82 and 82 can be adjusted to be wider or narrower with the recording material width center reference. The recording material P is placed on the tray, and the paper regulating plates 82 and 82 are moved in accordance with the width of the recording material P. As a result, the left and right side surfaces of the recording material P are regulated between the inner surfaces of the left and right paper regulating plates 82 and 82, and the recording material P is set in a state substantially coincident with the conveyance center (central paper passing reference line: virtual line) O. Is done.

  FIG. 2A shows a state in which the interval between the paper regulating plates 82 and 82 is widened to the maximum interval. In this example, the maximum interval is set to 320 mm, and the maximum width is 320 mm. Recording material can be passed. (B) shows a state in which the interval between the paper regulating plates 82 and 82 is narrowed to the minimum interval. In this example, the minimum interval is set to 76 mm, and a recording material having a minimum width of 76 mm is passed. I can make paper. In other words, in this example, recording materials of various sizes in the width range of 320 mm to 76 mm can be passed with the central reference at the center of the recording material width.

(2) Fixing device 12
FIG. 3 is an enlarged schematic cross-sectional view of the main part of the fixing device 12 in this embodiment. FIG. 4 is a partially enlarged view thereof. The fixing device 12 of the present embodiment is a pressure roller driving type / film heating type heating device described in JP-A-4-44075.

  Reference numeral 21 denotes a heater unit as a first fixing member, and reference numeral 22 denotes an elastic pressure roller as a second fixing member. The heater unit 21 and the pressure roller 22 are arranged in parallel in the vertical direction and are brought into pressure contact with a predetermined pressure to form a pressure contact portion (hereinafter referred to as a fixing nip portion) N.

  In the heater unit 21, reference numeral 23 denotes a film guide member having a substantially semicircular cross-sectional shape, which is a heat-resistant resin molding member such as PPS or liquid crystal polymer. The guide member 23 is a horizontally long member having a longitudinal direction in the drawing as a longitudinal direction, and a heating body (hereinafter referred to as a heater) 24 as a heating means is fitted into and held in a groove portion provided on the lower surface of the guide member 23 along the longitudinal direction. It is. The configuration of the heater 24 in this embodiment will be described in detail later. Reference numeral 25 denotes a cylindrical film material (fixing rotating body: hereinafter referred to as a fixing film) as a flexible member having heat resistance. The fixing film 25 is loosely fitted to the assembly of the guide member 23 and the heater 24 described above. For example, the fixing film 25 is formed of a cylindrical metal sleeve or a heat-resistant resin sleeve on the outer peripheral surface of which a silicon rubber layer is formed as an elastic layer, and a fluororesin layer made of PTEFE / PFA is formed as a release layer. It has sex.

  The pressure roller 22 is formed by forming an elastic layer 22b made of silicon rubber, fluorine rubber or the like and a release layer 22c on a cored bar 22a made of aluminum, iron or the like.

  Then, the heater unit 21 and the pressure roller 22 are brought into a pressurized state by a pressure mechanism (not shown) against the elasticity of the elastic layer 22b of the pressure roller 22. As a result, the heater 24 and the pressure roller 22 are pressed against each other with the fixing film 25 interposed therebetween to form a fixing nip portion N having a predetermined width (with respect to the recording material conveyance direction) necessary for heat fixing.

  The pressure roller 22 is rotationally driven by the driving means M at a predetermined peripheral speed in the counterclockwise direction of the arrow, which is the recording material conveyance direction. As the pressure roller 22 is driven to rotate, a rotational force acts on the cylindrical fixing film 25 by a frictional force at the fixing nip N between the pressure roller 22 and the outer surface of the fixing film 25. As a result, the fixing film 25 rotates around the guide member 23, and in the fixing nip portion N, the inner surface of the fixing film is in close contact with the downward surface of the heater 24 and slides in the clockwise direction of the arrow. Sliding grease (not shown) is applied between the inner surface of the fixing film 25 and the guide member 13 to keep the fixing film 25 slidable. Further, the rotation stability of the fixing film 25 is maintained by the guide member 23.

  The fixing film 25 is rotated by the rotational driving of the pressure roller 22, and the heater 24 is heated to a predetermined target temperature by energizing the heater 24 as will be described later. In this state, the recording material P carrying the unfixed toner image t is introduced between the fixing film 25 and the pressure roller 22 in the fixing nip N, and the toner image carrying surface is brought into close contact with the outer surface of the fixing film 25. The fixing nip N is nipped and conveyed together with the fixing film 25. As a result, the heat of the heater 24 is applied to the recording material P through the fixing film 25, and the unfixed toner image t is fixed to the surface of the recording material P by the pressure applied by the fixing nip N. The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 25 and is discharged and conveyed.

In this embodiment, the heater 24 is a ceramic heater. FIG. 5 is a diagram illustrating the configuration of the heater 24 used. This heater 24 is
1) Substrate (insulating substrate) 24a made of highly insulating ceramics such as horizontally long alumina, aluminum nitride, silicon carbide and the like whose longitudinal direction is perpendicular to the recording material conveyance direction on the conveyance path surface of the recording material P
2) Formed on the surface side of the ceramic substrate 24a along the longitudinal direction by screen printing or the like, for example, applied to a linear or narrow strip having a thickness of about 10 μm and a width of about 1 to 5 mm and fired, for example, Ag / Pd (Silver palladium: silver alloy), RuO ₂ , Ta ₂ N, etc. energization heating element (heating resistor) 24b
3) Electrode portions 24c and 24c formed of Ag / Pt (silver / platinum) or the like, which are electrically connected to both ends in the longitudinal direction of the energization heating element 24b.
4) An insulating protective layer, such as a thin glass coat or a fluororesin coat, which is provided so as to cover the energization heating element 24b and which can electrically insulate the energization heating element and withstand the friction with the fixing film 25. 24d
5) Thermistors TH1 to TH4 as first to fourth temperature detecting means provided on the back side of the ceramic substrate 24a, and a thermo switch TSW as a safety element.
Etc.

  In this embodiment, the longitudinal width L of the energization heating element 24b is 320 mm. The longitudinal width L of the energization heating element 24 b is an effective heat generation area of the heater 24. The center in the longitudinal direction of the effective heat generation area of the heater 24 corresponds to the conveyance center O of the recording material.

  Here, in the following description, in order to define the positions of the first to fourth thermistors TH1 to TH4 and the thermo switch TSW in the heater longitudinal direction, as shown in FIG. The heater position is set to ± 0 mm position. The position to the right of the ± 0 mm position is the plus (+) side position, and the position to the left is the minus (−) side position.

  The first thermistor TH1 is installed at a heater position of +20 mm as a central temperature detecting means for detecting a heater temperature at or near the recording material conveyance center. The thermo switch TSW is installed at a heater position of -20 mm. In the apparatus of the present embodiment, the width of the recording material having the minimum width that can be conveyed is 76 mm as described above, and the sheet passing area A of the recording material is a heater position range of +38 mm to −38 mm. The first thermistor TH and the thermo switch TSW are installed in the heater position range corresponding to the sheet passing area A of the recording material having the minimum width. That is, if the first thermistor TH and the thermo switch TSW pass the recording material at an appropriate position, that is, a predetermined central paper passing reference, the recording material of any width that can be conveyed always enters the paper passing area. Installed in the heater position.

  The second and third thermistors TH2 and TH3 serve as end temperature detecting means for detecting the heater temperature in the vicinity of both longitudinal ends of the effective heat generation area L (+160 mm to −160 mm) of the heater 24, respectively. , -120 mm heater position.

  The fourth thermistor TH4 is a heater closer to the recording material conveyance center O side than the second or third thermistors TH2 and TH3, which are end temperature detection means, outside the sheet passing area A of the minimum width recording material that can be conveyed. As an intermediate temperature detecting means for detecting temperature, it is installed at a heater position of +60 mm.

  Electrical information (resistance value) regarding the heater temperature at each thermistor position, which is detected by each of the first to fourth thermistors TH1 to TH4, is input to the control circuit unit C (DC line).

  The thermo switch TSW is connected in series to a power supply circuit (AC line) for the energization heating element 24b of the heater 24.

  The power of the AC power supply unit 100 is supplied to the energization heating element 24b of the heater 24 via the triac 101 and the thermo switch TSW controlled by the control circuit unit C. As a result, the energization heating element 24b generates heat over its entire length, and the effective heat generation area L of the heater 24 rises rapidly and steeply. The control circuit unit C controls the triac 101 so that the detected temperature of the first thermistor TH1 becomes a predetermined target temperature (180 ° C. in this embodiment), thereby controlling the power supplied from the AC power supply unit 100 to the energization heating element 24b. It is supposed to be.

  As control of the power supplied to the energization heating element 24b, the phase range provided for energization to the energization heating element 24b is detected by the first thermistor TH1 for each half-wave period of the alternating current output from the AC power supply unit 100. Phase control of changing according to temperature is adopted. Alternatively, wave number control or the like is adopted in which the energization from the AC power supply unit 100 to either the conduction or the interruption is switched according to the detected temperature of the first thermistor TH1 every half wave period. .

  Even if the thermo switch TSW causes a situation where the energization heating element 24b is continuously energized uncontrolled due to a failure of the control circuit portion C or the like (heater runaway of the heater), the heater 24 is overheated. It serves to cut off the power supply to the energization heating element 24b by urgently sensing the temperature. In the present embodiment, when the excessive temperature rise of the heater 24 reaches 250 ° C., the AC line is cut off to stop energization of the energization heating element 24b.

  If the recording material is fed at an appropriate position, that is, a predetermined center passing standard, the first thermistor TH1 and the thermo switch TSW are within the sheet passing area of the recording material regardless of the width of the recording material that can be conveyed. to go into. Each of the second to fourth thermistors TH2 to TH4 detects the temperature of the heater portion that has become a non-sheet passing portion according to the width of the recording material being passed. The detected temperature information of the thermistors TH2 to TH4 is input to the control circuit unit C.

  The temperature distribution graph (a) along the heater length in FIG. 6 is an example of the temperature distribution in the sheet passing area A and the non-sheet passing area of the heater 24 when a transportable recording material having a minimum width of 76 mm is passed. is there. Naturally, the temperature of the sheet passing area A is controlled to 180 ° C. However, the temperature of the non-sheet passing portion is increased simultaneously with the heat generation of the heater 24, and the temperature of the fourth thermistor TH4 is detected at about 230 ° C., the temperature of the second thermistor TH2 is 225 ° C., and the temperature of the third thermistor TH3 is Then, about 215 ° C. is detected for heat radiation from the heater end. Note that the non-sheet passing portion region temperature varies depending on the sheet passing interval and the temperature control temperature. As described above, the temperature information detected by the first to fourth thermistors TH1 to TH4 and input to the control circuit unit C is set in advance as a reference temperature and stored in the control circuit unit C. If the temperature is within a certain temperature or temperature range, the job can be completed.

(3) Fixing Device Protection Control Mode During Recording Material Heavy Running FIG. 7 is a control flow diagram of fixing device protection control during recording material heavy running. In the following, a first thermistor is provided in a heater portion which becomes a common sheet passing portion area in the case of a recording material having a large and small width that can be conveyed, and controls the temperature of the sheet passing portion area of the heater to a predetermined temperature TH1 is a main thermistor. In addition, the second to fourth thermistors TH2 to TH4 that detect the temperature of the heater portion that becomes the non-sheet-passing portion area according to the width of the recording material being passed are sub-thermistors.

  1) In the image forming apparatus configured as described above, the recording material P is double-fed from the multi-tray paper feeding unit 8 or the cassette paper feeding unit 7, and the double-fed recording material enters the fixing nip N of the fixing device 12. Then, the temperature drop in the sheet passing area in the fixing device 12 becomes extremely severe. This is because in the case of a recording material in a double feed state, a larger amount of heat is taken in the sheet passing area of the fixing device 12 than when a single recording material is used. As a result, the temperature of the paper passing area of the heater is reduced to a predetermined temperature control temperature (fixing temperature) in this embodiment, which is much lower than 180 ° C., and the temperature difference between the paper passing area and the non-paper passing area increases. .

  The control circuit unit C recognizes this large temperature difference state from the difference between the input temperature information from the main thermistor and the input temperature information from the sub-thermistor corresponding to the non-sheet passing region. Then, the control circuit unit C supplies power supplied from the AC power supply unit 100 to the energization heating element 24b in order to quickly recover the temperature of the sheet passing portion region of the heater to a predetermined temperature control temperature and to secure the fixing property. Increase or continuously energize to drive the heater 24 (steps A40 to A42). This failure detection threshold value is set to a temperature close to the upper limit temperature allowable as the non-sheet passing portion temperature increase temperature.

  In addition, even if a special recording material with a large heat capacity such as cardboard, postcard, or OHP sheet is passed, the temperature of the paper passing area will decrease, but during heavy running, the temperature will drop more than expected when passing the special recording material. A difference occurs. Thus, the control circuit C discriminates when the recording material is overrun and when the special recording material is passed.

  2) By driving the heater, the temperature of the paper passing area of the heater is restored to a predetermined temperature control temperature, while the temperature of the non-paper passing area where heat is not consumed for heating the recording material becomes abnormally high. The temperature reaches even 240 ° C. set in the present embodiment as the failure detection threshold as shown in the temperature distribution graph (b) along the heater length in FIG. 6 (steps A43 to A44).

  3) The temperature rise information of the non-sheet passing area is input to the control circuit C from the sub-thermistor corresponding to the non-sheet passing area. The control circuit unit C compares the input temperature information of the non-sheet passing unit region with the set failure detection threshold value 240 ° C. (step A45).

  4) Then, if the input temperature information of the non-sheet passing portion area does not reach the failure detection threshold 240 ° C., the control circuit portion C determines that the failure condition is not met, The printing operation of the printer A is continued under normal fixing device temperature control (step A46).

  The “failure condition” described in step A46 specifically means that “the fixing device may have failed due to thermal runaway”. Then, if the detected temperature of the sub-thermistor that detects the temperature of the non-sheet passing portion region of the heater 24 does not reach “240 ° C. as a failure detection threshold” in step A46, Judge that there is no failure (thermal runaway failure). Further, if the control circuit unit C has reached “240 ° C. as a failure detection threshold value”, the control circuit unit C determines that there is a possibility that the fixing device has failed (thermal runaway failure). Further, if the fixing device is truly broken (thermal runaway failure), the main thermistor TH1 and the heater 24 non-sheet passing portion are not limited to the sub-thermistor detecting the temperature of the non-sheet passing portion region of the heater 24. The detection temperature of the sub-thermistor corresponding to the region has also reached “240 ° C. as a failure detection threshold”.

  5) Further, when the temperature information of the non-sheet passing portion area to be input is equal to or higher than the failure detection threshold 240 ° C., the control circuit portion C determines that the failure condition is met and sets the failure state detection counter to 1 (Step A47). This is stored as a software counter value on the program.

  6) Then, if the result of addition is a value indicating a plurality of times, such as 2, that is, when it occurs continuously (step A48), the control circuit unit C determines that a fixing device failure has actually occurred. Then, the control circuit unit C stops the printing operation of the printer A and notifies the display unit 103 of the printer A and / or the host device B of the fixing unit failure (step A49). In the above description, “when continuously generated” refers to the case where the failure detection threshold 240 ° C. is continuously detected by the sub-thermistor detecting the temperature of the non-sheet passing portion region of the heater 24. When the fuser failure notification is made, the user calls a service man.

  7) Further, the control circuit unit C urges the user to remove the recording material P that has been double-fed as a jam once, as a result of the addition, if it does not occur continuously and does not fail. In this case, if the conveyance of the recording material P is stopped before the recording material P passes through the fixing device 12, there is a possibility that the fixing device 12 is damaged when the recording material is removed. For this reason, the control circuit unit C stops the printing operation of the printer A after confirming that the recording material P has passed through the fixing device 12 based on the recording material leading and trailing edge detection signal from the fixing paper discharge sensor S2. Then, the jam is notified to the display unit 103 of the printer A and / or the host device B (step A50).

  8) When the printing operation of the printer A is normally started after the user performs the predetermined jam processing, the control circuit unit C determines that the previous failure state detection is an abnormal temperature rise due to heavy running of the recording material. The failure state detection counter is reset (step A51). Note that the control circuit unit C does not reset the counter until the recording material printed after the jam processing is normally discharged. Normal printing is determined by the fact that the recording material has been discharged in the same manner as normal printing. “Normally printed” is synonymous with a case where no fixing device failure is detected in the printing after the jam processing.

  By performing the control as described above, it is possible to prevent the fixing unit from being damaged due to the heavy running of the recording material.

  That is, even if the recording material is fed in heavy running from the multi-tray paper feeding unit 8 or the cassette paper feeding unit 7 and introduced into the heating device, it is detected instantaneously to prevent the heating device from being broken. Corresponding to many recording material sizes, more recording material sizes can be passed with the highest throughput.

(4) Others 1) The fixing device 12 is not limited to a film heating type heating device as in the above-described embodiment. A heating device such as a heat roller may be used. The heating source of the fixing member is not limited to the ceramic heater. A halogen heater, an infrared lamp, an electromagnetic induction heater, a high-frequency heater, or the like can also be used.

  2) The sheet passing / conveyance of the recording material is not limited to the center reference, and can be a one-side reference.

1 is a schematic configuration diagram of an image forming apparatus in an embodiment. It is a top view of a multitray, (a) has shown the state where the space | interval of a paper control board was extended to the maximum space | interval, (b) has shown the state by which the space | interval of the paper control plate was narrowed to the minimum space | interval. FIG. 2 is an enlarged cross-sectional model view of a main part of a fixing device in the present embodiment. FIG. 4 is a partially enlarged view of FIG. 3. It is a structure explanatory view of a heater. It is explanatory drawing of the temperature distribution of the paper passing part area | region of a heater, and a non-paper passing part area | region. FIG. 6 is a control flow diagram of fixing device protection control during recording material heavy running.

Explanation of symbols

A ... Image forming apparatus, B ... Host device, C ... Control circuit section, 1-6 ... Image forming section, 7 ... Cassette feeding section, 8 ... Multi-tray, 12 ... Fixing unit, 16 ... FU tray, 20 ... FD tray, 24 ... Heater, TH1 to TH4 ... First to fourth temperature detection means (thermistor), TSW ... Safety element (thermo switch)

Claims (1)

A recording material feeding unit for feeding the recording material;
Image forming means for forming an unfixed image on a recording material fed from the recording material feeding unit;
A first fixing member and a second fixing member that forms a nip portion in contact with the first fixing member, and a recording material introduced from the image forming unit is nipped and conveyed by the nip portion to perform recording. A heating device for heating and fixing an unfixed image on the material;
Control means for executing device control;
Display means for notifying when an abnormal state occurs in the device;
In an image forming apparatus having
The control means includes temperature information from a temperature detecting means for detecting the temperature of the paper passing portion area of the heating device into which the recording material is introduced, and temperature information from a temperature detecting means for detecting the temperature of the non-paper passing area. When an abnormality of the heating device is detected, the recording material is transported until the recording material passes through the heating device, and then the operation of the device is stopped. When it is determined, when the double feed occurs for the first time, it is notified to the display means as a double feed jam. An image forming apparatus having a control mode for notifying the display means of a failure of a heating device.