JP4708932B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a copying machine, a printer, a facsimile machine, or the like equipped with an image heating apparatus.

  Examples of the image heating device include a fixing device that fixes an unfixed image on the recording material, and a gloss increasing device that increases the gloss of the image by heating the image fixed on the recording material. .

  Conventionally, in the image forming apparatus as described above, as a fixing method for fixing an unfixed toner image on a recording material, the recording material is obtained by heating and melting the unfixed toner image of the recording material in view of safety and good fixability. In general, a heat fixing method for fixing to the surface is used.

  In recent years, a belt heating type heating apparatus has been put into practical use from the viewpoint of quick start and energy saving. That is, a heat-resistant resin belt (hereinafter referred to as a fixing belt) as an image heating member is sandwiched between, for example, a ceramic heater as a heating body and a pressure roller as a pressure member, and a pressure nip portion (hereinafter referred to as a fixing belt). A fixing nip portion). Then, a recording material on which an unfixed toner image is formed and supported is introduced between the fixing belt and the pressure roller in the fixing nip portion, and is nipped and conveyed together with the fixing belt. As a result, the unfixed toner image is fixed on the recording material surface with the pressure of the fixing nip portion while applying heat from the ceramic heater through the fixing belt.

  This belt heating type heating apparatus does not require energization of the heater in standby, and after the image forming apparatus receives the print signal, the recording material reaches the heating apparatus even if the heater is energized. It is possible to make it heatable. Therefore, from the viewpoint of energy saving, the belt heating type heating device is an excellent heat fixing device that does not waste energy.

  Furthermore, a fixing method has been proposed in which a pressure member is disposed through a belt so as to face the fixing roller.

  Regardless of which fixing method is used, when the recording material is fixed in the fixing region, the surface of the heating roller passing through the sheet passing region has a substantially uniform temperature distribution.

  However, when a small size recording material having a width smaller than the maximum width size recording material that can be passed through the apparatus is continuously fixed in the fixing region, the temperature of the non-sheet passing region passing surface of the heating roller is excessively increased. This is because, when a small-size recording material is continuously passed, heat is partially stored in the non-sheet passing area where the recording material does not pass, as much as there is no heat removal by the recording material.

  This phenomenon is called the temperature rise at the end of the fixing device or the temperature rise at the non-sheet passing portion. If the temperature rise at the end of the fixing device becomes high, the temperature rise limits of the fixing member components and the pressure roller are exceeded. Lead to damage of the parts.

  In order to prevent such a temperature rise in the non-sheet passing portion, conventionally, when a small size recording material is fed, so-called throughput reduction control is performed to suppress the temperature rise in the non-sheet passing portion by reducing the fixing rotation speed. ing. However, this throughput reduction control results in reduced productivity.

  In order to prevent a decrease in productivity, as in Patent Documents 1 and 2, a blower fan is provided in the fixing device, and the temperature rise is suppressed by blowing air to the heating roller and pressure roller of the non-sheet passing portion. In addition, a configuration for achieving compatibility between the temperature rise of the non-sheet passing portion and the productivity is known.

  In the technique of Patent Document 1, cooling air is blown from the cooling fan disposed in the fixing device to the non-sheet passing area side. In addition, an element for detecting the temperature of the fixing region is provided when small-size paper is passed, and ON / OFF control of the blower fan is performed based on the signal value.

In the technique of Patent Document 2, when cooling air is blown from the cooling fan to the non-sheet passing area side, the length in the width direction of the blowing port is adjusted according to the width of the recording material to be used. Further, the temperature rise of the non-sheet passing portion is prevented even for paper of different sizes.
Japanese Patent Application Laid-Open No. 60-136779 JP 2003-076209 A

  In Patent Documents 1 and 2, since a blower fan is used to improve productivity reduction due to throughput reduction control, fixing is performed at a normal fixing speed when a small-size recording material is continuously fed during the blower fan operation. Operation is performed.

  However, when the cooling area of the fixing member by the blower fan and the recording material width that is actually passed through are different, for example, when the B5R width is passed when cooling the non-sheet passing portion of the A4R width, The fixing member surface outside the A4R end is cooled by a blower fan. However, from the B5R end to the A4R end, since the actual sheet passing is the B5R width, the temperature rises as a non-sheet passing part, but that part is not cooled by the blower fan, and the blower fan is operating. No throughput down control is performed. As a result, the temperature of the surface of the fixing member is excessively increased, which may eventually lead to destruction of the fixing device.

  The discrepancy between the cooling area of the blower fan and the size of the recording material for the actual paper as described above occurs when the recording material size set by the user and recognized by the apparatus is different from the recording material size actually used. .

  In recent years, copying machines and the like are not provided with a detection member for automatically recognizing the recording material size on the main body for cost reduction, and many users set the recording material size to be used.

  In a device that uses a cooling means such as a blower fan to prevent the temperature rise of the non-sheet passing portion and does not include a detection member for automatically recognizing the recording material size, the set recording material size and actual sheet passing It is necessary to ensure safety to prevent device destruction due to size mismatch.

  In the prior art described in Patent Document 1, the blower fan is turned on and off based on the signal value of the element that detects the temperature of the fixing region, and the fixing device is cooled by the blower fan. However, the temperature detecting element is used for the ON / OFF operation of the blower fan when the recording material size for which the blower fan is operated, but the temperature detection unit detects the temperature of the temperature rising portion when the blower area and the sheet pass area do not match. Not arranged to be able to. Therefore, it is not possible to ensure the safety of the fixing device when the recording material is set incorrectly by the user.

  As described above, if the recording material is set incorrectly, the actual image size is different from the recording material size, so an image with a missing edge may be discharged, and the printing operation is immediately performed. It may be desirable to stop it.

  Further, it is desirable for the user to complete the image forming operation without stopping the printing operation even when the air blowing area and the paper passing size do not match as described above.

  The prior art described in Patent Document 2 describes a technique corresponding to cooling by a blower fan and different recording material sizes by an opening width adjusting mechanism. Such an opening width adjusting mechanism leads to an increase in the cost of the apparatus, and it becomes a complicated and expensive apparatus to cope with a plurality of sizes up to the minimum width paper such as a postcard.

  Therefore, many do not provide the opening adjustment mechanism. Normally, it does not support postcard sizes that are used less frequently, and is provided with a fixed opening that matches the size of the most frequently used recording material.

  The fixed opening width device has the same problem as the fixing device provided with the opening width adjusting mechanism, and it is necessary to ensure the safety when the recording material is set incorrectly and to complete the image forming operation.

  The present invention has been proposed in view of the above-described circumstances. In an image forming apparatus having a cooling unit that cools a non-sheet passing portion generated in an image heating member when a small size recording material is passed, An object of the present invention is to ensure the safety of the apparatus when the area and the recording material size to be passed are different. It is also intended to complete the printing operation.

In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording material, and an image heating unit that heats an image on the recording material at a nip portion. A first detection unit disposed in a sheet passing region of a recording material having a minimum size capable of passing in the width direction orthogonal to the recording material conveyance direction, and detecting the temperature of the image heating unit; and the first detection unit Control means for controlling the temperature of the image forming means in accordance with the output of the image forming apparatus, second detection means for detecting the temperature of the end of the image heating means in the width direction, and from the first detection means in the width direction. An image forming apparatus comprising: a third detection unit configured to detect a temperature of the image heating unit provided at a distance position shorter than the distance position of the second detection unit from the first detection unit as a distance position; Of the second detection means Adjusting a cooling means for cooling the end region of said image heating means in response to a force, a cooling range by the cooling means in the end region of said image heating means according to the width of the recording material that has been set by the operation means When the temperature detected by the third detection means reaches a predetermined temperature when the third detection means does not exist in the cooling range by the cooling means in a state where the cooling operation by the adjustment means and the cooling means is performed, an image is displayed. And a stop means for stopping the forming operation.

Still another typical configuration of the image forming apparatus according to the present invention for achieving the above object includes an image forming means for forming an image on a recording material, and an image for heating an image on the recording material at a nip portion. A heating unit; a first detection unit that is disposed in a sheet passing region of a recording material of a minimum size that can be passed in a width direction orthogonal to a conveyance direction of the recording material; and that detects a temperature of the image heating unit; Control means for controlling the temperature of the image forming means in accordance with the output of the first detection means; second detection means for detecting the temperature of the end of the image heating means in the width direction; and the first detection in the width direction. An image forming apparatus comprising: a third detection unit that is provided at a distance position shorter than the distance position from the first detection unit to the second detection unit as a distance position from the unit, and detects a temperature of the image heating unit. The second test Cooling means for cooling the end region of said image heating means in response to the output means, the cooling range by the cooling means in the end region of said image heating means according to the width of the recording material that has been set by the operation means The temperature detected by the third detecting means reaches a predetermined temperature when the adjusting means for adjusting and the third detecting means are not in the cooling range by the cooling means in the state of performing the cooling operation by the cooling means. Then, there is provided means for reducing the number of recording materials passing through the nip portion per unit time.

  According to the image forming apparatus of the present invention described above, the temperature rise of the non-sheet passing portion when passing a small size recording material is excessive when the recording material size recognized by the apparatus is different from the recording material size to be passed. This prevents damage to the device due to temperature rise and prevents printing that does not match the recording material size. In addition, the printing operation can be completed.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, although an Example is an example of the best embodiment in this invention, this invention is not limited only to the various structure demonstrated in an Example. That is, the various configurations described in the embodiments can be replaced with other known configurations within the scope of the idea of the present invention.

(1) Image Forming Unit FIG. 4 is a schematic longitudinal sectional view showing a schematic configuration of an electrophotographic full color printer which is an example of an image forming apparatus according to the present invention. First, an outline of an image forming unit that is an image forming unit that forms an image on a recording material will be described.

  This printer forms an image on a recording material and outputs it in accordance with input image information from an external host device 200 that is communicably connected to a control circuit unit (control board: CPU) 100. be able to.

  The external host device 200 is a computer, an image reader, or the like. The control circuit unit 100 exchanges signals with the external host device 200. It also exchanges signals with various image forming devices and manages image forming sequence control.

  Reference numeral 8 denotes an endless and flexible intermediate transfer belt (hereinafter abbreviated as a belt), which is stretched between the secondary transfer counter roller 9 and the tension roller 10 so that the roller 9 is driven. Is rotated at a predetermined speed in the counterclockwise direction of the arrow. Reference numeral 11 denotes a secondary transfer roller, which is in pressure contact with the secondary transfer counter roller 9 via a belt 8. A contact portion between the belt 8 and the secondary transfer roller 11 is a secondary transfer portion.

  Reference numerals 1Y, 1M, 1C, and 1Bk denote first to fourth image forming units, which are arranged below the belt 8 in a line at a predetermined interval along the belt moving direction. Each image forming unit is a laser exposure type electrophotographic process mechanism, and is a drum-type electrophotographic photosensitive member (hereinafter abbreviated as a drum) as an image carrier that is rotated at a predetermined speed in a clockwise direction indicated by an arrow. ) 2. Around each drum 2, a primary charger 3, a developing device 4, a transfer roller 5 as a transfer means, and a drum cleaner device 6 are arranged. Each transfer roller 5 is disposed on the inner side of the belt 8 and is brought into pressure contact with the corresponding drum 2 through a downward belt portion of the belt 8. A contact portion between each drum 2 and the belt 8 is a primary transfer portion. Reference numeral 7 denotes a laser exposure device for the drum 2 of each image forming unit, which includes laser light emitting means, a polygon mirror, a reflection mirror, and the like that emit light corresponding to time-series electric digital pixel signals of given image information.

  The control circuit unit 100 causes each image forming unit to perform an image forming operation based on the color separation image signal input from the external host device 200. As a result, yellow, magenta, cyan, and black color toner images are formed at predetermined control timings on the surfaces of the rotating drum 2 in the first to fourth image forming units 1Y, 1M, 1C, and 1Bk. Is done. The electrophotographic image forming principle and process for forming a toner image on the drum 2 are well-known and will not be described.

  The toner image formed on the surface of the drum 2 of each image forming unit is rotationally driven at the primary transfer unit in the rotational direction and forward direction of each drum 2 and at a speed corresponding to the rotational speed of each drum 2. The images are successively superimposed and transferred onto the outer surface of the belt 8. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the belt 8 by superimposing the four toner images.

  On the other hand, at a predetermined paper feed timing, paper feed of a paper feed cassette at a selected level among the upper and lower multistage cassette paper feed units 13A, 13B, and 13C in which recording materials P of various sizes of large and small are loaded and accommodated. The roller 14 is driven. As a result, one sheet of recording material P stacked and stored in the paper feed cassette at that level is separated and fed, and conveyed to the registration roller 16 through the vertical conveyance path 15. When manual paper feed is selected, the paper feed roller 18 is driven. As a result, one sheet of recording material stacked and set on the manual feed tray (multi-purpose tray) 17 is separated and fed and conveyed to the registration roller 16 through the vertical conveyance path 15.

The registration roller 16 feeds the recording material P so that the leading edge of the recording material P reaches the secondary transfer portion in accordance with the timing when the leading edge of the full-color toner image on the rotating belt 8 reaches the secondary transfer portion. Transport timing. As a result, the full-color toner images on the belt 8 are secondarily transferred sequentially onto the surface of the recording material P at the secondary transfer portion. The recording material that has exited the secondary transfer portion is separated from the surface of the belt 8, guided by the longitudinal guide 19, and introduced into the fixing device (fixing device) 20. The fixing device 20, toner image of plural colors described above is established as a solid Chakuzo the recording material surface is melted and mixed. The recording material that has exited the fixing device 20 passes through a transport path 21 as a full-color image formed product and is sent out onto a paper discharge tray 23 by a paper discharge roller 22.

  The surface of the belt 8 after separation of the recording material in the secondary transfer portion is cleaned by removing residual deposits such as secondary transfer residual toner by the belt cleaning device 12 and repeatedly used for image formation.

  In the mono black print mode, only the fourth image forming unit Bk that forms a black toner image is controlled in image forming operation. When the duplex printing mode is selected, the recording material printed on the first side is sent out onto the paper discharge tray 23 by the paper discharge roller 22 and immediately before the rear end portion passes through the paper discharge roller 22. Thus, the rotation of the paper discharge roller 22 is converted to reverse rotation. As a result, the recording material is switched back and introduced into the re-transport path 24. Then, the paper is turned upside down and conveyed to the registration roller 16 again. Thereafter, similarly to the first side printing, the sheet is conveyed to the secondary transfer unit and the fixing device 20 and is sent out on the paper discharge tray 23 as a double-sided printed image formed product.

(2) Fixing device 20
In the following description, the longitudinal direction of the fixing device or a member constituting the fixing device is a direction parallel to the direction orthogonal to the recording material conveyance direction in the recording material conveyance path surface. Regarding the fixing device, the front is the surface on the recording material introduction side, and the left and right are the left or right when the device is viewed from the front. The 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.

  FIG. 3 is a schematic cross-sectional view showing a schematic configuration of a fixing device 20 as an image heating device in the present embodiment. The fixing device 20 is roughly composed of a belt (film) heating type fixing mechanism 20A and a blower cooling mechanism (cooling means) 20B. FIG. 5 is a schematic front view of the fixing mechanism section 20A, and FIG. 6 is a schematic front sectional view thereof.

(2-1) Fixing mechanism 20A
First, an outline of the fixing mechanism 20A will be described. The fixing mechanism portion 20A is basically an on-demand fixing device of a belt heating type / pressure rotating body driving type (tensionless type) disclosed in Japanese Patent Application Laid-Open Nos. 4-44075 to 44083, 4-204980 to 204984, and the like. .

  Reference numeral 31 denotes a belt assembly as a first fixing member (heating member), and 32 denotes an elastic pressure roller as a second fixing member (pressure member). Is formed.

  In the belt assembly 31, reference numeral 33 denotes a cylindrical and flexible fixing belt (fixing film, thin roller: hereinafter abbreviated as a belt) as an image heating member for heating an image on a recording material at a nip portion N. . Reference numeral 34 denotes a belt guide member (hereinafter abbreviated as a guide member) having heat resistance and rigidity having a substantially semicircular arc shape in cross section. Reference numeral 35 denotes a ceramic heater (hereinafter abbreviated as a heater) as a heating source, which is disposed on the outer surface of the guide member 34 by being fitted into a concave groove portion provided along the length of the member. The belt 33 is loosely fitted to the guide member 34 to which the heater 35 is attached. Reference numeral 36 denotes a rigid pressure stay (hereinafter abbreviated as a stay) having a U-shaped cross section, which is disposed inside the guide member 34. Reference numeral 37 denotes an end holder that is fitted to the outward projecting arm portions 36 a at both left and right ends of the stay 36, and 37 a is a flange portion that is integral with the end holder 37.

  The pressure roller 32 is obtained by reducing the hardness by providing an elastic layer 32b such as silicone rubber on a cored bar 32a. In order to improve surface properties, a fluororesin layer 32c such as PTFE, PFA, FEP may be further provided on the outer periphery. The pressure roller 32 is disposed as a pressure rotating member with both ends of a core metal 32a rotatably supported by bearings between left and right side plates of an apparatus chassis (not shown) via a bearing member.

  The belt assembly 31 is arranged in parallel with the pressure roller 32 with the heater 35 facing the pressure roller 32, and the pressure spring 40 is interposed between the left and right end holders 37 and the left and right fixed spring receiving members 39. Is shrunk. Thereby, the stay 36, the guide member 34, and the heater 35 are pressed and urged toward the pressure roller 32 side. The pressing urging force is set to a predetermined value, and the heater 35 is pressed against the pressure roller 32 against the elasticity of the elastic layer 32b with the belt 33 interposed therebetween, and between the belt 33 and the pressure roller 32. A fixing nip portion N having a predetermined width is formed in the recording material conveyance direction.

The belt 33 in this embodiment has a three-layer composite structure of a base layer 33a, an elastic layer 33b, and a release layer 33c in order from the inner surface side to the outer surface side, as shown in the schematic diagram of the layer configuration in FIG. For the base layer 33a, a heat resistant belt having a belt film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more can be used in order to reduce the heat capacity and improve the quick start property. For example, a belt made of polyimide, polyimide amide, PEEK, PES, PPS, PTFE, PFA, FEP or the like can be used. In this example, a cylindrical polyimide belt having a diameter of 25 mm was used. The elastic layer 33b has a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 4.18605 × 10 ⁻¹ W / m · ° C. (1 × 10 ⁻³ [cal / cm.sec.deg]), and a thickness of 200 μm. Silicone rubber was used. As the release layer 203, a PFA coating layer having a thickness of 20 μm was used. As the release layer 33c, a PFA coating layer having a thickness of 20 μm was used. A PFA tube may be used. The PFA coat is excellent in that the thickness can be reduced and the material has a greater effect of enveloping the toner than the PFA tube. On the other hand, since the mechanical and electrical strength of the PFA tube is superior to that of the PFA coat, it can be used properly depending on the case.

  The heater 35 in this embodiment is a back surface heating type using aluminum nitride or the like as a heater substrate, and is a horizontally long low heat capacity having a direction perpendicular to the moving direction of the fixing belt 33 and the recording material P as a longitudinal direction. It is a linear heating element. FIG. 8 is a schematic cross-sectional view of the heater 35 and a control system diagram. The heater 35 has a heater substrate 35a made of aluminum nitride or the like. An electric resistance material such as Ag / Pd (silver / palladium) provided along the length is provided on the back side (the side opposite to the fixing belt facing side) of the heater substrate 35a, for example, about 10 μm, and the width is 1 to 5 mm. The energizing heat generating layer 35b is provided by coating by screen printing or the like. Further, a protective layer 35c made of glass or fluororesin is provided thereon. In the present embodiment, a sliding member (lubricating member) 35d is provided on the surface side (belt facing surface side) of the heater substrate 35a.

  The heater 35 is fixedly supported by exposing the surface of the heater substrate on which the sliding member 35d is provided in a groove formed along the longitudinal direction of the guide at the substantially central portion of the outer surface of the guide member 34. In the fixing nip portion N, the surface of the sliding member 35d of the heater 35 and the inner surface of the belt 33 slide in contact with each other. The belt 33 that is a rotating image heating member is heated by the heater 35.

  By energizing between the longitudinal ends of the energization heat generation layer 35b of the heater 35, the energization heat generation layer 35b generates heat, and the heater 35 rapidly rises in temperature over the effective heat generation width A in the heater longitudinal direction. The heater temperature is detected by a first temperature detecting means TH1 such as a thermistor (hereinafter referred to as a first thermistor) TH1 disposed in contact with the outer surface of the heater protective layer 35c, and its output (signal value related to temperature) is detected. The data is input to the control circuit unit 100 via the A / D converter. Based on the input detected temperature information, the control circuit unit 100 controls energization of the energized heat generation layer 35b from the power source (power supply unit, heater drive circuit unit) 101 so as to maintain the heater temperature at a predetermined temperature. That is, the temperature of the belt 33, which is an image heating member heated by the heater 35, is controlled to a predetermined fixing temperature according to the output of the first thermistor TH1.

  In this embodiment, a proportional control method is used as a temperature control method, and a method is used in which electric power proportional to the deviation between the heater temperature set value and the temperature measured by the first thermistor TH1 is applied to the heater 35. .

  The pressure roller 32 is rotationally driven in a counterclockwise direction indicated by an arrow by a motor (driving means) M1. A rotational force acts on the belt 33 by a frictional force in the fixing nip portion N between the pressure roller 32 and the outer surface of the belt 33 due to the rotational driving of the pressure roller 32. As a result, the belt 33 rotates around the guide member 34 in the counterclockwise direction indicated by the arrow while the inner surface of the belt 33 is in close contact with the heater 35 in the fixing nip portion N and slides (pressure roller driving method). The belt 33 rotates at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 32. The left and right flange portions 37a serve to receive the belt end on the shift side and restrict the shift when the rotating belt 33 moves to the left or right along the length of the guide member 34. In order to reduce the mutual sliding frictional force between the heater 35 and the inner surface of the belt 33 in the fixing nip portion N, a sliding member 35d is disposed on the heater surface of the fixing nip portion N, and heat resistance is provided between the inner surface of the belt 33. Use a lubricant such as grease.

  Based on the print start signal, the rotation of the pressure roller 32 is started and the heater 35 starts to heat up. In a state in which the rotational peripheral speed of the belt 33 becomes steady and the temperature of the heater 35, that is, the temperature of the belt 33 rises to a predetermined level, the recording material P carrying the toner image t in the fixing nip portion N faces the toner image carrying surface side. It is introduced on the 33rd side. The recording material P is in close contact with the heater 35 via the belt 33 at the fixing nip portion N, and moves and passes through the fixing nip portion N together with the belt 33. In the moving and passing process, heat is applied to the recording material P by the belt 33 heated by the heater 35 and the toner image t is heated and fixed on the surface of the recording material P. The recording material P that has passed through the fixing nip N is separated from the surface of the belt 33 and discharged and conveyed.

  In this embodiment, the recording material P is conveyed by so-called central reference conveyance centering on the recording material. In other words, the recording material of any width, which can be used in the apparatus, passes through the central portion in the longitudinal direction of the fixing belt 33 in the width direction central portion of the recording material. S is the reference line (virtual line) of the center of the recording material.

  W1 is the sheet passing width (maximum sheet passing width) of the maximum width recording material that can be passed through the apparatus. In the present embodiment, the maximum sheet passing width W1 is A4 size width 297 mm (A4 lateral feed). The effective heating area width A in the heater longitudinal direction is slightly larger than the maximum sheet passing width W1. W3 is the sheet passing width (minimum sheet passing width) of the minimum width recording material that can be passed through the apparatus. In this embodiment, the minimum sheet passing width W3 is a postcard size width of 100 mm (postcard vertical feed). W2 is the sheet passing width of the recording material having a width between the maximum width recording material and the minimum width recording material. In this embodiment, the sheet passing width W2 is A5 size width 210 mm (A5 horizontal feed). Hereinafter, a recording material having a width size corresponding to the maximum sheet passing width W1 is referred to as a maximum size recording material, and a recording material having a width smaller than the recording material is referred to as a small size recording material.

  a is a difference width portion ((W1-W2) / 2) between the maximum sheet passing width W1 and the sheet passing width W2, and b is a difference width portion ((W1-W3) / 2) between the maximum sheet passing width W1 and the minimum sheet passing width W3. It is. That is, it is a non-sheet passing portion that occurs when a recording material of A5 length or postcard length that is a small size recording material is passed. In this embodiment, since the recording material passing is based on the center, the non-sheet passing portions a and b are generated at the left and right sides of the sheet passing width W2 and the left and right sides of the sheet passing width W3, respectively. The width of the non-sheet passing portion varies depending on the size of the small size recording material used for sheet passing.

  The first thermistor TH1 is disposed so as to detect the heater temperature (= the temperature at which the belt 33 passes) of the portion substantially corresponding to the recording material center paper passing reference line S.

  TH2 is a second temperature detection means (hereinafter referred to as a second thermistor) such as a thermistor, and detects the temperature outside the recording material conveyance area of the belt 33 when the recording material to be fed is a recording material having a predetermined width. . The second thermistor TH2 is disposed at the free end of a leaf spring-shaped elastic support member 38 whose base is fixed to the guide member 34. The second thermistor TH2 is elastically brought into contact with the inner surface of the base layer 33a of the belt 33 by the elasticity of the elastic support member 38. The second thermistor TH2 is disposed so as to be located closer to the belt end portion of 144.1 mm from the recording material center paper passing reference line S. The position of the second thermistor TH22 is inside A4 (148.5 mm) and outside LTR (139.7 mm) in the central reference transport.

  TH3 is a third temperature detecting means such as a thermistor (hereinafter referred to as a third thermistor). When the recording material to be fed is a recording material having a predetermined width, the temperature near the end of the recording material conveyance area of the belt 33 is indicated. To detect. The third thermistor TH3 is also disposed at the free end of a leaf spring-shaped elastic support member 38 whose base is fixed to the guide member 34. The third thermistor TH3 is elastically brought into contact with the inner surface of the base layer 33a of the belt 33 by the elasticity of the elastic support member 38. The third thermistor TH3 is disposed at a position closer to the end of the belt 103 mm from the recording material center sheet passing reference line S.

  The outputs (signal values relating to temperature) of the first to third thermistors TH1, TH2, and TH3 are all input to the control circuit unit 100 via the A / D converter.

  As described above, the control circuit unit 100 controls energization from the power source 101 to the energized heat generating layer 35b based on the detected temperature information input from the first thermistor TH1 so as to maintain the heater temperature at a predetermined temperature. That is, the temperature of the belt 33, which is an image heating member heated by the heater 35, is controlled to a predetermined fixing temperature according to the output of the first thermistor TH1.

  The first thermistor TH1 may be disposed in elastic contact with the inner surface of the base layer of the belt portion corresponding to the paper passing portion W3. Conversely, the second and third thermistors TH2 and TH3 may be disposed so as to detect the heater temperature corresponding to the non-sheet passing portion.

(2-2) Blower cooling mechanism 20B
The blower cooling mechanism unit 20B is a cooling unit that cools the temperature rise of the non-sheet passing portion of the belt 33, which is generated when a small size recording material is continuously passed (small size job) by blowing. That is, it is a cooling means for cooling the outside of the recording material conveyance area (non-sheet passing portion) of the belt 33 as the image heating member when the width of the recording material to be passed is set to be a predetermined width. FIG. 9 is a schematic external perspective view of the blower cooling mechanism 20B. FIG. 10 is an enlarged sectional view taken along line (10)-(10) in FIG.

  With reference to FIG.3, FIG.9, FIG.10, the ventilation cooling mechanism part 20B in a present Example is demonstrated. The blower cooling mechanism 20B includes a blower (cooling) fan (hereinafter abbreviated as a fan) 41, a blower duct 42 that guides the wind generated by the fan 41, and a portion of the blower duct 42 that faces the fixing mechanism 20A. It has an air outlet (duct opening) 43 arranged. In addition, it has a shutter (shielding plate) 44 that adjusts the opening width of the blower opening 43 to a width suitable for the width of the recording material to be passed, and an opening width adjustment mechanism (shutter driving device) 45 that drives the shutter. .

  The fan 41, the air duct 42, the air outlet 43, and the shutter 44 are arranged symmetrically on the left and right portions in the longitudinal direction of the belt 33. Reference numeral 49 denotes an intake channel portion disposed on the intake side of the fan 41. A centrifugal fan such as a sirocco fan can be used as the fan 41.

  The left and right shutters 44 are supported so as to be slidable in the left-right direction along the plate surface of the support plate 46 that forms the air blowing port 43 and extends in the left-right direction. The left and right shutters 44 are connected to each other by rack teeth 47 and a pinion gear 48, and the pinion gear 48 is driven forward or reversely by a motor (pulse motor) M2. As a result, the left and right shutters 44 are interlocked to open and close in a symmetrical relationship with respect to the corresponding air blowing ports 43. The support plate 46, the rack teeth 47, the pinion gear 48, and the motor M2 constitute a shutter drive device 45.

  The left and right blowing ports 44 are provided from a position slightly closer to the center to the maximum sheet passing width W1 than the non-sheet passing portion b generated when the minimum width recording material is passed. The left and right shutters 44 are arranged in such a direction as to close the air blowing port 44 by a predetermined amount from the longitudinal center of the support plate 46 to the outside.

  The control circuit unit 100 receives the width information W (FIG. 8) of the recording material to be passed based on the input of the used recording material size by the user. Then, the control circuit unit 100 controls the shutter driving device 45 based on the information. That is, by driving the motor M2 to rotate the pinion gear 48 and moving the shutter 44 by the rack teeth 47, the air blowing port 54 can be opened by a predetermined amount.

  When the width information of the recording material is the maximum size recording material (A4 side), the control circuit unit 100 controls the opening width adjusting mechanism 45 to move the shutter 44 to the fully closed position where the air blowing port 43 is completely closed. To do. In the case of a small size recording material of a postcard size, the shutter 44 is moved to a fully opened position where the air blowing port 43 is completely opened. Further, when the recording material is a small size of A5 landscape size, the shutter 44 is moved to a position where the blower opening 43 is opened by a portion corresponding to the non-sheet passing portion a.

  When the small-size recording material to be passed is LTR-R, EXE, K8, LTR, etc., the control circuit unit 100 opens the blower opening by an amount corresponding to the non-sheet passing portion that occurs in those cases. The shutter 44 is moved to the position.

  That is, the shutter 44 can adjust the opening width of the air blowing port 43 in accordance with the input width information W of the recording material.

  Here, the minimum, maximum, and total recording material sizes in the present embodiment are specification sheets guaranteed by the image forming apparatus main body, and are not irregular-size sheets that are uniquely used by the user.

  Position information of the shutter 44 is detected by a sensor 51 disposed on the support plate 46 at a flag 50 disposed at a predetermined position of the shutter 44. Specifically, the home position is determined at the shutter position where the air blowing port 43 is fully closed, and the opening amount is detected from the rotation amount of the motor M2.

  An opening width detection sensor that directly detects the current position of the shutter 44 is provided, and shutter position information from the sensor is fed back to the control circuit, so that the shutter 44 has an appropriate opening width corresponding to the width of the recording material to be passed. It is also possible to control movement to the position. As the shutter stop position, the position corresponding to the length in the width direction of the small size recording material can be accurately determined by detecting the edge position of the shutter with a sensor. Accordingly, the cooling air can be blown only to the non-sheet passing area of all the small size recording materials.

(2-3) Control Sequence FIG. 1 is a control sequence diagram according to the first embodiment. When a small size recording material having a width smaller than the maximum size recording material is continuously fixed at the time of image formation, the temperature of the non-sheet passing portion rises. The second thermistor TH2 detects the temperature of the belt inner surface of the non-sheet passing portion. When the second thermistor TH2 detects the predetermined temperature T1, the control circuit unit 100 controls the opening width adjusting mechanism 45 to open the shutter 44 to the opening width corresponding to the set recording material size. Then, the operation of the blower fan 41 is started (blowing fan ON). This suppresses the temperature rise in the non-sheet passing area. Then, the non-sheet passing area is cooled by the cooling air of the blower fan 41, and when the temperature of the second thermistor TH2 is lowered to a predetermined temperature, the operation of the blower fan 41 is stopped.

  In an apparatus in which the recording material width automatic detection is not performed, the user arbitrarily sets the recording material size, and the shutter 44 is adjusted to an opening width corresponding to the non-sheet passing portion width generated by the set recording material size. . At this time, for example, when the user sets a postcard (recording material width, 50 mm from the center) in the paper feeding unit and sets the recording material of A5 (recording material width, 105 mm from the center) to the main body, the shutter 44 is set. It operates up to the opening width corresponding to the A5 paper. However, since the postcard is actually passed, the fixing belt portion from the A5 end to the postcard end is not exposed to the wind from the blower fan 41, and a temperature raising portion is generated. Then, the temperature of the belt portion of the third thermistor TH3 (103 mm from the center) increases. When the detected temperature of the third thermistor TH3 reaches the predetermined temperature T0, it is determined that the recording material is erroneously set, and the image forming operation is stopped.

  In addition, when a large-size sheet is passed, when the recording material is erroneously set, the detected temperature of the second thermistor is the same as in the case of small-size sheet passing in the conventional fixing device configuration in which the blower fan 41 does not operate. When T2 is reached, it is determined that the recording material is erroneously set, and the image forming operation is stopped.

  The control circuit unit 100 stops the image forming operation and displays on the display means 102 such as a liquid crystal display or / and 201 (FIG. 8) that the recording material is erroneously set. The display unit 102 is a display unit provided on the image forming apparatus side. The display unit 201 is a display unit provided on the external host device 200 side.

  As described above, since the image forming operation is stopped when the recording material is erroneously set, it is possible to ensure the safety of the apparatus when the cooling area due to the erroneous recording material setting and the size of the recording material to be passed are different.

  FIG. 2 is another control sequence diagram. Here, the throughput reduction control in FIG. 2 is a control for reducing the number of recording materials passing through the fixing nip N per unit time. This control includes a control for decreasing the discharge speed of the recording material of the fixing device and a control for increasing the space between the recording materials passed through the fixing device.

  When a small size paper having a width smaller than the maximum size paper is continuously fixed during image formation, the temperature of the non-sheet passing portion rises. The second thermistor TH2 detects the temperature of the inner surface of the fixing belt 33. When the second thermistor TH2 detects the predetermined temperature T1, the control circuit unit 100 controls the opening width adjusting mechanism 45 to open the shutter 44 to the opening width corresponding to the set paper size. The operation of the blower fan 41 is started (blowing fan ON). This suppresses the temperature rise in the non-sheet passing area. Then, the non-sheet passing area is cooled by the cooling air of the blower fan 41, and when the temperature of the second thermistor TH2 is lowered to a predetermined temperature, the operation of the blower fan 41 is stopped.

  Next, throughput reduction control when a sheet is erroneously set will be described. The normal throughput reduction control is performed when the second thermistor TH2 arranged for detecting the fixing belt temperature in the non-sheet passing portion reaches a predetermined temperature T2 during continuous passage of small size paper. Through throughput reduction control and maintaining the temperature of the second thermistor TH2 at a predetermined temperature T2 or less, an abnormal fixing image such as hot offset is prevented.

  In the fixing device of the present embodiment, since the temperature rise of the non-sheet passing portion by the blower fan 41 is prevented, the above-described throughput down control is performed during normal blower fan operation, and productivity is not reduced. .

  In an apparatus in which automatic detection of the paper width is not performed, the user arbitrarily sets the paper size, and the shutter 44 is adjusted to an opening width corresponding to the non-sheet passing portion width generated in the set paper size. At this time, for example, when the user sets a postcard (paper width, 50 mm from the center) in the paper supply unit and sets A5 (paper width, 105 mm from the center) paper, the shutter 44 is set to the set A5 paper. It operates to the opening width corresponding to. However, since the postcard is actually passed, the fixing belt portion from the A5 end to the postcard end is not exposed to the wind from the blower fan 41, and a temperature raising portion is generated.

  Then, the temperature of the fixing belt portion of the third thermistor TH3 (103 mm from the center) rises. When the detected temperature of the third thermistor TH3 reaches a predetermined temperature T0, it is determined that the sheet is erroneously set, and throughput reduction control is performed.

  Accordingly, it is possible to prevent an excessive temperature rise due to erroneous sheet setting, and it is possible to complete image formation without stopping the printing operation.

  As in the case of small-size paper passing in the conventional fixing device configuration in which the blower fan 41 does not operate when passing large-size paper, when a wrong paper setting occurs, the detection temperature T2 of the second thermistor is set. When it reaches, throughput down control is performed.

  The second thermistor TH2 is used for ON / OFF control of the blower fan 41, and the third thermistor TH3 is used for throughput reduction control when the paper is set incorrectly, when a small-size sheet is passed through which the blower fan 41 operates. It is done.

  In the configuration of the present embodiment, as shown in FIG. 11, the air blowing / cooling mechanism portion 2B is not provided with the opening width adjusting mechanism 45 as in the first embodiment, and the opening width of the duct opening portion 43 is, for example, non-horizontal It corresponds to the width of the paper passing section. The opening width of the duct at this time is not limited to the A5 side, and it is necessary to set the reuse frequency of the main body to a small size.

Also in the present embodiment, the first to third three thermistors TH1 to TH3 are provided as in FIGS. 5 and 6 of the first embodiment. Also in this embodiment, the first thermistor TH1 is used for temperature control of the heater 35 (= belt 33). The second thermistor TH <b> 2 is used for ON / OFF control of the blower fan 41 when small-size paper is passed through which the blower fan 41 operates. The second and third thermistors TH2 and TH3 are used for control when a sheet is erroneously set.

  Detection of erroneous sheet setting, control after detection, and effects at that time are the same as in the first embodiment.

  The second thermistor TH2 and the third thermistor TH3 may be arranged on the opposite sides of the first thermistor TH1, as shown in FIG. That is, the third thermistor TH3 may be arranged so as to detect the temperature of the belt 33 at a distance position shorter than the distance position from the first thermistor TH1 to the second thermistor TH2.

  In the above description, the fan 41 is configured to cool the fixing member. However, the same effect can be obtained when the pressure member is cooled.

  The cooling means is not limited to fan cooling.

  In the above description, the heating member (fixing member) is a thin roller type having a low heat capacity. However, the heating member (fixing member) is not particularly limited to this, and a belt-type fixing member can provide the same effect.

  The image heating means 20A is not limited to the film heating type heating device of the embodiment, but may be a heat roller type heating device or other configuration heating device. An electromagnetic induction heating apparatus can also be used.

  Further, the same effect can be obtained even if the image heating means 20A has a configuration in which the recording material is passed on the one-side conveyance basis.

Control sequence diagram according to the first embodiment (part 1) Control sequence diagram according to the first embodiment (part 2) Schematic cross-sectional view showing a schematic configuration of a fixing device (image heating device) of Example 1 A schematic longitudinal sectional view of an example of an image forming apparatus equipped with the fixing device Front schematic view of the fixing mechanism of the fixing device Longitudinal front view of the fixing mechanism Model diagram of fixing belt layer structure Cross section model of heater and block diagram of control system External perspective schematic view of the blower cooling mechanism FIG. 9 is an enlarged cross-sectional view taken along line (10)-(10). The external appearance perspective schematic diagram of the ventilation cooling mechanism part without an opening width adjustment mechanism in Example 2 The figure which showed the other example of arrangement | positioning of 2nd and 3rd thermistors TH2 and TH3

Explanation of symbols

  20.. Fixing device (image heating device), 20 A... Fixing mechanism (image heating means), 20 B... Blow cooling mechanism (cooling means), TH 1, first temperature detecting means, TH 2, second Temperature detection means, TH3..Third temperature detection means, 100..control circuit section

Claims (6)

An image forming means for forming an image on the recording material, an image heating means for heating the image on the recording material at the nip portion, and a recording material having a minimum size capable of passing in the width direction orthogonal to the recording material conveyance direction. A first detection unit that is disposed in the sheet passing area and detects the temperature of the image heating unit; a control unit that controls the temperature of the image forming unit in accordance with an output of the first detection unit; A second detection means for detecting the temperature of the end of the image heating means, and a distance position shorter than the distance position of the second detection means from the first detection means as a distance position from the first detection means in the width direction; An image forming apparatus comprising: a third detection unit configured to detect a temperature of the image heating unit;
A cooling means for cooling an end region of the image heating means according to the output of the second detection means;
Adjusting means for adjusting the cooling range by the cooling means in the end region of the image heating means according to the width of the recording material set by the operating means;
The image forming operation is stopped when the temperature detected by the third detecting unit reaches a predetermined temperature when the third detecting unit is not in the cooling range by the cooling unit while the cooling unit is performing the cooling operation. Stop means to cause,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the cooling unit includes a cooling fan. A shutter for adjusting the amount of air blown from the cooling means to the image heating means, and an adjusting means for adjusting the opening width of the shutter in accordance with the width of the recording material set by the operation means. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image forming means for forming an image on the recording material, an image heating means for heating the image on the recording material at the nip portion, and a recording material having a minimum size capable of passing in the width direction orthogonal to the recording material conveyance direction. A first detection unit that is disposed in the sheet passing area and detects the temperature of the image heating unit; a control unit that controls the temperature of the image forming unit in accordance with an output of the first detection unit; A second detection means for detecting the temperature of the end of the image heating means, and a distance position shorter than the distance position of the second detection means from the first detection means as a distance position from the first detection means in the width direction; An image forming apparatus comprising: a third detection unit configured to detect a temperature of the image heating unit;
A cooling means for cooling an end region of the image heating means according to the output of the second detection means;
Adjusting means for adjusting the cooling range by the cooling means in the end region of the image heating means according to the width of the recording material set by the operating means;
When the temperature detected by the third detection means reaches a predetermined temperature when the third detection means does not exist in the cooling range by the cooling means in a state where the cooling operation is performed by the cooling means, Means for reducing the number of recording materials passing through the nip,
An image forming apparatus comprising:   The image forming apparatus according to claim 4, wherein the cooling unit includes a cooling fan. A shutter for adjusting the amount of air blown from the cooling means to the image heating means, and an adjusting means for adjusting the opening width of the shutter in accordance with the width of the recording material set by the operation means. The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus.