JP2022067935A - Fixing device - Google Patents

Abstract

To provide a fixing device that can prevent a situation in which: unevenness in the quantity of air from a cooling fan causes unevenness in temperature in the longitudinal direction of a fixing film, which causes low temperature offset and hot offset.SOLUTION: The shapes of openings Lb and Rb are changed in a longitudinal direction according to the quantity of air from a cooling fan to make uniform the quantity of air flowing to a fixing film in the longitudinal direction and prevent unevenness in temperature in the longitudinal direction of the fixing film, thereby preventing an image defect.SELECTED DRAWING: Figure 10

Description

The present invention relates to a fixing device for fixing a toner image on a recording material. This fixing device can be used, for example, in an image forming means such as a copying machine, a printer, a facsimile, and a multifunction device having a plurality of these functions.

In the image forming apparatus as described above, an unfixed toner image is formed on a sheet-shaped recording material (paper) by an image forming means, and then the toner image is fixed as a fixed image by the fixing means.
Although various methods have been proposed for the fixing means, a thermal pressure fixing method fixing device for heating and pressurizing the toner image to fix the toner image is generally used. This fixing device combines a heating rotating body (fixing roller, fixing film, etc.) heated by a heating means and a pressure rotating body (pressurizing roller, pressure belt, etc.) that presses against the heating rotating body to form a fixing nip portion. Have.

Then, by rotating both rotating bodies and introducing a recording material having an unfixed toner image supported on the fixing nip portion and sandwiching and transporting the toner image, the toner image is transferred to the recording material surface by the heat and nip pressure of the heating rotating body. It is used for thermal pressure fixing.

In such a fixing device, when a small-sized recording material having a width smaller than the maximum size recording material having a maximum width that can be passed through the device is continuously passed through and fixed, the heated rotating body is used. The temperature of the surface of the non-paper area (outside the recording material transport area) rises excessively. This is because when the small-sized recording material is continuously passed through the paper, heat is partially stored in the non-paper-passing area where the recording material of the fixing nip portion does not pass because the heat is not taken away by the recording material.

This phenomenon is referred to as a temperature rise at the end of the fixing device or a temperature rise at the non-passing portion, and if the temperature rise at the end is excessive, it leads to the occurrence of fixing failure and thermal deterioration of the device components.

Patent Documents 1 and 2, for example, have proposed a configuration in which the non-paper-passing area of the fixing device is cooled by cooling air in order to suppress the temperature rise at the end of the small-sized recording material during continuous paper-passing.

In the technique described in Patent Document 1, cooling air is selectively blown from a cooling fan arranged in a fixing device to the non-paper area side.

The technique described in Patent Document 2 has a fan for blowing air to a non-passing portion of the fixing device to cool the cooling fan, and the air blowing area of the cooling fan is moved according to the width of the recording material by moving the shutter. Adjustable image forming apparatus is disclosed. The cooling fan is controlled according to the detection temperature of the temperature detecting member provided in the area where air can be blown in the non-passing portion of the fixing film or the heater.

Japanese Unexamined Patent Publication No. 4-51179 Japanese Unexamined Patent Publication No. 2013-134421

FIG. 1 is a diagram showing a cooling configuration for cooling a fixing film using an axial fan. There is an opening for cooling both ends of the fixing film, and both ends of the fixing film are cooled by blowing air through this opening with an axial flow fan. Here, FIGS. 2 (a) and 2 (b) show the amount of air blown to both ends of the fixing film at the measurement position shown in FIG. The air from the axial fan is sent to the opening through the duct, but since it is rectified and not the wind, the air volume at the opening differs in length. As a result, the air volume on the center side of the fixing film is large and easy to cool in the opening on the front side, and the air volume on the back side of the fixing film is large and easy to cool in the opening on the back side. Therefore, as shown in FIG. 3, when looking at the longitudinal temperature distribution when 100 sheets of A4R are passed, cooling unevenness occurs in the non-passing area at the front and back, and the temperature is low on the front side of the passing area. Low temperature offset due to, hot offset due to high temperature in the back side of the paper passing area occurs.

An object of the present invention is to provide a fixing device in which the amount of air flowing through the fixing film becomes uniform and image defects due to uneven cooling can be prevented.

In order to achieve the above object, the present invention comprises a fixing member, a pressure member, an opening for cooling a predetermined region of the fixing member 33, and a blower cooling means for blowing air toward the opening. In a fixing device having a shutter that opens and closes the opening, the shape of the opening is different in length.

By reducing the opening amount of the cooling FAN where the air volume is large and increasing the opening amount of the cooling FAN where the air volume is small, the air volume flowing to the fixing film becomes uniform and image defects due to cooling unevenness can be prevented.

It is a figure which shows the cooling structure using an axial flow. It is a figure which shows the longitudinal air volume distribution which is blown to a fixing film. It is a figure which shows the longitudinal temperature distribution of a fixing film. It is a cross-sectional model diagram of the image forming apparatus in an Example. It is a cross-sectional model view of the fixing device in an Example. It is an exploded perspective model figure of the fixing mechanism part and the blast cooling mechanism part of the fixing device. It is a front model view of a part of the fixing mechanism part notched. It is a block diagram of a fixing device control system. It is an exploded perspective model view of the blast cooling mechanism part in Example 1. FIG. It is operation explanatory drawing of the shutter plate in Example 1. FIG. It is a figure which shows the longitudinal temperature distribution of the fixing film in an Example. It is a figure which shows the longitudinal air volume distribution which is blown to the fixing film in an Example. It is an exploded perspective model view of the blast cooling mechanism part in Example 2. FIG. It is operation explanatory drawing of the shutter plate in Example 2. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(1) Image Forming Unit FIG. 4 is a schematic vertical cross-sectional view showing a schematic configuration of an electrophotographic full-color printer which is an example of an image forming apparatus equipped with an image heating device according to the present invention as a fixing device. First, the outline of the image forming unit will be described.

This printer operates in image formation according to the input image information from the external host device 200 communicably connected to the control circuit unit (control means: CPU) 100, forms a full-color image on the recording material, and outputs the image. 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-making devices and controls image-drawing sequences.

Reference numeral 8 is an endless and flexible intermediate transfer belt (hereinafter abbreviated as a belt), which is stretched between the secondary transfer facing roller 9 and the tension roller 10 to drive the roller 9. Is driven to rotate at a predetermined speed in the counterclockwise direction of the arrow. Reference numeral 11 denotes a secondary transfer roller, which is pressed against the above-mentioned secondary transfer facing roller 9 via a belt 8. The contact portion between the belt 8 and the secondary transfer roller 11 is the secondary transfer portion.

1Y, 1M, 1C, and 1Bk are the first to fourth image forming portions, and are arranged in a row under the belt 8 at predetermined intervals along the belt moving direction. Each image forming unit is a laser exposure type electrophotographic process mechanism, and each is a drum-type electrophotographic photosensitive member (hereinafter, abbreviated as drum) as an image carrier that is rotationally driven at a predetermined speed in the clockwise direction of the arrow. ) Has 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 around each drum 2. Each transfer roller 5 is arranged inside the belt 8 and is pressed against the corresponding drum 2 via the downward belt portion of the belt 8. The contact portion between each drum 2 and the belt 8 is the primary transfer portion. Reference numeral 7 is a laser exposure apparatus for the drum 2 of each image forming unit, and is composed of a laser emitting means, a polygon mirror, a reflection mirror, and the like that emit light corresponding to the time-series electric digital pixel signal of the given image information.

The control circuit unit 100 causes each image forming unit to perform an image forming operation based on the color color separation image signal input from the external host device 200. As a result, yellow, magenta, cyan, and black color toner images are formed on the surfaces of the rotating drum 2 in the first to fourth image forming units 1Y, 1M, 1C, and 1Bk at predetermined control timings. Will be done. Since the principle and process of electrophotographic image formation for forming a toner image on the drum 2 are known, the description thereof will be omitted.

The above toner images formed on the surface of the drum 2 of each image forming unit are rotationally driven by the primary transfer unit in the forward direction with the rotation direction of each drum 2 and at a speed corresponding to the rotation speed of each drum 2. It is sequentially superimposed and transferred to 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 above four toner images.

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

The resist roller 16 sets the recording material P so that the tip of the recording material P reaches the secondary transfer portion at the timing when the tip of the full-color toner image on the rotating belt 8 reaches the secondary transfer portion. Timing transfer. As a result, in the secondary transfer unit, the full-color toner images on the belt 8 are collectively transferred to the surface of the recording material P in sequence. The recording material leaving the secondary transfer section is separated from the surface of the belt 8 and guided by the vertical guide 19 to be introduced into the fixing device 20. By this fixing device 20, the toner images of the above-mentioned plurality of colors are melt-mixed and fixed as a fixed image on the surface of the recording material. The recording material leaving the fixing device 20 is sent out onto the paper ejection tray 23 by the paper ejection roller 22 through the transport path 21 as a full-color image forming product.

The surface of the belt 8 after the recording material is separated by the secondary transfer unit is cleaned by removing residual deposits such as the secondary transfer residual toner by the belt cleaning device 12, and is repeatedly subjected to image drawing.

In the mono-black print mode, only the fourth image forming unit Bk that forms the black toner image is controlled to form an image. When the double-sided printing mode is selected, the recording material printed on the first side is sent out onto the paper ejection tray 23 by the paper ejection roller 22, and the rear end portion is immediately before passing through the paper ejection roller 22. The rotation of the paper ejection roller 22 is converted into reverse rotation. As a result, the recording material is switched back and introduced into the retransport path 24. Then, it is turned upside down and conveyed to the resist roller 16 again. After that, as in the case of printing on the first side, the image is conveyed to the secondary transfer unit and the fixing device 20, and is sent out onto the output tray 23 as a double-sided print image forming product.

(2) Fixing device 20
In the following description, the longitudinal direction of the fixing device or the members constituting the fixing device is a direction parallel to the direction orthogonal to the recording material transporting direction in the recording material transporting road 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 the dimension of the recording material in the direction orthogonal to the recording material transport direction on the recording material surface.

FIG. 5 is an enlarged cross-sectional schematic view of the fixing device 20 portion in FIG. The fixing device 20 is roughly divided into a belt heating type fixing mechanism unit 20A and a blast cooling mechanism unit 20B.

(2-1) Fixing mechanism unit 20A
First, the outline of the fixing mechanism unit 20A will be described mainly with reference to FIGS. 5 to 8. FIG. 6 is an exploded perspective view of the fixing mechanism section 20A and the blower cooling mechanism section 20B, FIG. 7 is a front schematic view of the fixing film assembly of the fixing mechanism section 20A and the pressure roller, and FIG. 8 is a block diagram of the control system of the fixing device. Is.

The fixing mechanism unit 20A is basically an on-demand fixing device of a film heating method / pressure rotating body drive method (tensionless type) disclosed in JP-A-4-44075 to 44083, 4-204980 to 204984, etc. be.

31 is a fixing film assembly, and 32 is an elastic pressure roller as a pressure rotating body. The fixing nip portion N is formed by pressure welding of both the fixing film assembly 31 and the pressure roller 32.

In the fixing film assembly 31, 33 is a fixing film having a cylindrical shape (endless belt shape, sleeve shape) as a heating rotating body and having flexibility. Reference numeral 34 is a belt guide member (hereinafter, abbreviated as a guide member) having heat resistance and rigidity having a substantially semicircular gutter shape in cross section. Reference numeral 35 denotes a ceramic heater (hereinafter abbreviated as a heater) as a heating source (heating body), which is fitted and fixed to the outer surface of the guide member 34 in a concave groove portion provided along the length of the member. It is done. The fixing film 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 stay) having a U-shaped cross section, which is arranged inside the guide member 34. Reference numeral 37 is an end holder fitted to the outward protruding arm portions 36a at both left and right ends of the stay 36, and 37a is a flange portion integrated with the end holder 37.

The fixing film 33 is a composite layer structure in which a heat-resistant resin film or a metal form is usually used as a base layer, and an elastic layer, a release layer, or the like is added to the base layer, and the fixing film 33 is thin and flexible. It is a member with high thermal conductivity and low heat capacity as a whole.

The ceramic heater 35 is a horizontally long, thin linear heating body having a low heat capacity whose length is perpendicular to the moving direction of the fixing film 33 and the recording material P. The basic configuration is a heater substrate made of a ceramic material such as aluminized aluminum or alumina, and an energized heat generating layer such as silver-palladium formed on the substrate surface. Since various types of ceramic heaters are known, detailed description thereof will be omitted.

The pressure roller 32 is formed by providing an elastic layer 32b such as silicone rubber on the core metal 32a to reduce the hardness. In order to improve the surface properties, the outer periphery is further covered with a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin (PFA), and a tetrafluoroethylene / hexafluoropropylene copolymer resin ( A fluororesin layer 32c such as FEP) may be provided. The pressure roller 32 is arranged so that the left and right ends of the core metal 32a are rotatably held between the left and right side plates 38L and 38R of the apparatus frame 38 via a bearing member 39.

The fixing film assembly 31 is arranged in parallel with the pressure roller 32 so as to face the heater 35 side. Then, the left and right end holders 37 are respectively urged in the axial direction of the pressurizing roller 32 with a predetermined force F by a pressurizing mechanism (not shown). As a result, the surface of the heater 35 is pressed against the pressure roller 32 via the fixing film 33 against the elasticity of the elastic layer 32b, and the fixing nip having a predetermined width in the recording material transport direction, which is necessary for heating and fixing. Part N is formed. The pressurizing mechanism has a pressure releasing mechanism, and has a configuration in which the pressurizing is released at the time of jam processing or the like, and the recording material P sandwiched between the fixing nip portions N can be easily removed.

Reference numerals 40 and 41 are an entrance guide and a fixing paper ejection roller assembled to the apparatus frame 38. The entrance guide 40 serves to guide the recording material P so that the recording material P that has passed through the secondary transfer nip portion and is guided by the vertical guide 19 and has entered the fixing device 20 is accurately guided by the fixing nip portion N. Fulfill.

G is a drive gear fixed to one end of the core metal 32a of the pressure roller 32. By transmitting the rotational force of the fixing motor M1 to the gear G via a power transmission mechanism (not shown), the pressurizing roller 32 is rotationally driven in the clockwise direction of the arrow in FIG. Due to the rotational drive of the pressure roller 32, a rotational force acts on the fixing film 33 due to the frictional force between the pressure roller 32 and the outer surface of the fixing film 33 at the fixing nip portion N. As a result, the fixing film 33 rotates the outer circumference of the guide member 34 in the counterclockwise direction of the arrow while the inner surface thereof slides in close contact with the heater 35 at the fixing nip portion N (pressurized roller drive method). The fixing film 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 and regulate the movement of the belt end portion on the side when the rotating fixing film 33 moves to the left or right along the length of the guide member 34. Grease (lubricant) is applied to the inner surface of the fixing film 33 to ensure the slidability of the fixing film 33 with respect to the heater 35 and the guide member 34.

The recording material P introduced into the fixing nip portion N is sandwiched and conveyed by the rotation of the pressure roller 32 and the fixing film 33. In this embodiment, the recording material P is transported by the so-called central reference transport centered on the recording material. That is, the central portion in the width direction of the recording material passes through the central portion in the longitudinal direction of the fixing film 33 for recording materials of any width that can be used for passing paper through the apparatus. S is the recording material central paper passage reference line (virtual line).

TH1 and TH2 are two thermistors, a main and a sub, as first and second temperature detecting means. The main thermistor TH1 is arranged in contact with the back surface of the heater at a position substantially at the center of the heater 35 in the longitudinal direction so as to detect the temperature of the heater portion that serves as a paper-passing portion for recording materials of any width. be. The sub-thermistor TH2 detects the temperature of the fixing film portion corresponding to the non-passing portion when the recording material having a width smaller than the maximum width recording material that can be passed through the device is passed through the fixing film. It is arranged so as to be in elastic contact with the inner surface of 33. Specifically, the sub-thermistor TH2 is supported by a free end portion of a leaf spring-shaped elastic support member 42 whose base is fixed to the guide member 34. The sub-thermistor TH2 is arranged so as to be elastically contacted with the inner surface of the fixing film 33 by the elasticity of the elastic support member 42.

The heater 35 is energized from the heater drive circuit 92 (FIG. 8) as a power supply unit to the energized heat generating layer provided on the surface of the heater substrate, so that the energized heat generating layer generates heat and the heater 35 generates heat. The temperature rises rapidly over the entire effective heat generation width in the longitudinal direction of the heater. The heater temperature is detected by the main thermistor TH1, and electrical information regarding the heater temperature is input to the control circuit unit 100 via the A / D converter 81. Further, the temperature of the fixing film 33 is detected by the sub-thermistor TH2, and electrical information regarding the fixing film temperature is input to the control circuit unit 100 via the A / D converter 82. The control circuit unit 100 determines the temperature control content of the fixing heater 35 based on the outputs of the main thermistor TH1 and the sub thermistor TH2, and controls the energization from the heater drive circuit 92 to the fixing heater 35. That is, the temperature control of the fixing heater 35 is controlled so that the heater temperature detected by the main thermistor TH1 is maintained at a predetermined fixing temperature.

Then, the control circuit unit 100 controls the fixing motor drive circuit 91 based on the print signal from the external host device 200 or another control signal, and starts the rotational drive of the pressurizing roller 32. Further, the heater drive circuit 92 is controlled to start the heat-up of the heater 35. In a state where the rotation speed of the fixing film 33 becomes steady and the temperature of the heater 35 rises to a predetermined level, the recording material P carrying the unfixed toner image t on the fixing nip portion N from the image forming portion side is along the entrance guide 40. Be guided and introduced. The toner image supporting surface side of the recording material P faces the fixing film 33. The recording material P comes into close contact with the heater 35 at the fixing nip portion N via the fixing film 33, and moves and passes through the fixing nip portion N together with the belt 33. In the process of passing through the movement, heat is applied to the recording material P by the fixing film 33 heated by the heater 35, and the toner image t is heated and fixed on the recording material P surface. The recording material P that has passed through the fixing nip portion N is separated from the surface of the fixing film 33 and discharged and conveyed.

(2-2) Blower cooling mechanism unit 20B
Next, the blast cooling mechanism unit 20B will be described mainly with reference to FIGS. 9 to 11. The blower cooling mechanism section 20B cools the temperature rise of the non-passage section of the fixing mechanism section 20A, which occurs when a recording material having a width smaller than the maximum width recording material that can be passed through the device is continuously passed through the device. It is a cooling means to be used. FIG. 9 is an exploded perspective view of the blower cooling mechanism unit 20B. The opening Lb has a shape in which the opening area narrows from the center toward the end, and the opening Rb has a shape in which the opening area widens from the center toward the end.

FIG. 10 is an operation explanatory diagram of the shutter plate. The blower cooling mechanism portion 20B has a left side duct 51L in which a blower port La is formed facing the left side portion in the longitudinal direction of the fixing film 33, and a left side cooling fan 52L for blowing cooling air to the duct 51L. Further, it has a right side duct 51R in which an air outlet Ra is formed facing the right side portion in the longitudinal direction of the fixing film 33, and a right side cooling fan 52R for blowing cooling air to the duct 51R. Further, it has a shutter mechanism 53 as an opening width adjusting mechanism for adjusting the opening width of the blower port La of the left duct 51L and the blower port Ra of the right side duct 51R.

The cooling fans 51L and 52R employ axial-flow fans, which are lower in cost than sirocco fans and cross-flow fans.

The shutter mechanism 53 includes a shutter frame 54, openings Lb / Rb provided on the left side portion and the right side portion in the longitudinal direction of the frame, a pair of left and right movable shutter plates 55L / 55R, a shutter motor M2, and a shutter plate position detecting means. It has 55a, 55b, PH, etc. The shapes and sizes of the left and right openings Lb and Rb correspond to the shapes and sizes of the air outlets La and Ra of the left and right ducts 51L and 51R, respectively. The left and right ducts 51L and 51R are arranged by fixing the air outlets La and Ra to the left and right openings Lb and Rb of the substrate 54 and fixing them to the substrate 54, respectively.

The pair of left and right movable shutter plates 55L / 55R are arranged on the surface opposite to the side where the ducts 51L / 51R of the substrate 54 are fixedly arranged. The left shutter plate 55L moves so as to adjust the opening width of the left opening Lb, that is, the air outlet La of the left duct 51L. The right shutter plate 55R moves so as to adjust the opening width of the right opening Rb, that is, the air outlet Ra of the right duct 51R. The left and right shutter plates 55L and 55R are connected by a rack-pinion mechanism (not shown). Then, the pinion is driven to rotate in the forward and reverse directions by the shutter motor (pulse motor) M2, so that the pinions move in conjunction with each other so as to adjust the opening widths of the air outlets La and Ra of the left and right ducts 51L and 51R in the same manner.

In FIG. 10, in order to avoid complication, the ventilation cooling mechanism unit 20B shows only the ducts 51L / 51R on the left and right sides, the cooling fans 52L / 52R, and the shutter plates 55L / 55R.

Here, regarding the recording material, the maximum width recording material that can be passed through the fixing device is large size paper, the minimum width recording material is small size paper, and the width recording material between the large size paper and the small size paper is used. Use medium size paper.

FIG. 10A shows a state in which small-sized paper is passed through, where Q is a paper-passing area for small-sized paper and R is a non-passing area generated on both the left and right sides of the paper-passing area Q. The air outlets La of the left and right ducts 51L and 51R face the left and right non-paper areas R and R, respectively. Further, the widths of the air outlets La and Ra of the left and right ducts 51L and 51R correspond to the widths of the left and right non-paper areas R and R, respectively. The left and right shutter plates 55L and 55R are moved to positions where the air outlets La and Ra of the left and right ducts 51L and 51R are fully opened, respectively. Therefore, the left and right non-passing areas R and R of the fixing film 33 generated when the small size paper is passed are cooled by the cooling air blown from the blower ports La and Ra in the fully opened state of the left and right ducts 51L and 51R, respectively. , The temperature rise of the non-passing part during continuous passing of small size paper is prevented.

FIG. 10B shows a state in which medium-sized paper is passed, where Q is a paper-passing area for medium-sized paper and R is a non-paper area generated on both the left and right sides of the paper-passing area Q. The left and right shutter plates 55L and 55R are moved to positions where the opening widths of the air outlets La and Ra of the left and right ducts 51L and 51R are narrowed according to the width of the medium-sized paper, respectively. Therefore, the left and right non-passing areas R and R of the fixing film 33 generated when the medium-sized paper is passed are affected by the cooling air blown from the air outlets La and Ra whose opening widths of the left and right ducts 51L and 51R are adjusted, respectively. It is cooled to prevent the temperature rise of the non-passing portion during continuous passing of medium-sized paper.

FIG. 10C shows a state when a large-sized paper is passed through. In this case, the temperature rise of the non-passing portion does not occur in the fixing film 33, so that the left and right shutter plates 55L and 55R are respectively. The left and right ducts 51L / 51R are moved to the positions where the air outlets La / Ra are fully closed. Therefore, the fixing film 33 is not cooled by the cooling air. In the case of this large-sized paper passing paper, the control may be performed to keep the cooling fans 52L / 52R in the stopped state. Further, in this case, the control of moving the left and right shutter plates 55L / 55R to the fully closed position with respect to the air outlets La / Ra of the left and right ducts 51L / 51R, respectively, may be omitted.

The left and right shutter plates 55L and 55R are controlled to move to positions corresponding to the width of the recording material used for passing paper. As a result, the air outlets La and Ra of the left and right ducts 51L and 51R are adjusted to the optimum opening width for the width of the recording material through which the paper is passed, and the air is cooled with the optimum non-paper width. Specifically, the bent edge portions 55a (FIGS. 5 and 9) of one of the left and right shutter plates 55L and 55R have a plurality of edge portions 55b determined for recording materials of various width sizes. Is provided.

Further, a photo sensor PH for detecting the edge portion 55b is fixedly provided on the shutter frame 54. The edge portion detection information of the photo sensor PH is input to the control circuit unit 100 via the A / D converter 83. The control circuit unit 100 controls the shutter motor M2 to rotate forward or backward so that the edge portion 55b corresponding to the width size information of the recording material used, which is input from the external host device 200 or the like, is detected by the photosensor PH. , Move the left and right shutter plates 55L / 55R. Then, the drive of the shutter motor M2 is stopped when the edge portion 55b corresponding to the width size information of the recording material used for paper passing is detected by the photo sensor PH. As a result, the left and right shutter plates 55L and 55R are moved to positions corresponding to the width of the recording material used for passing paper.

Next, the operation of the left and right cooling fans 52L / 52R in the fixing device of this embodiment will be described. When medium-sized and small-sized paper having a width smaller than that of the above-mentioned large-sized paper is continuously fixed at the time of image formation, the temperature of the non-passing area R (FIG. 10) rises. At this time, the sub-thermistor TH2 as the second temperature detecting means detects the inner surface temperature of the fixing film portion corresponding to the non-passing area R. When the control circuit unit (execution means) 100 detects a certain temperature predetermined by the sub thermistor TH2, the control circuit unit (execution means) 100 controls the shutter motor drive circuit 93, and the shutter motor M2 sets the left and right shutter plates 55L / 55R to the width of the recording material. Move to the corresponding position. Further, the cooling fan drive circuit 94 (FIG. 8) is controlled to start the operation of the left and right cooling fans 52L / 52R. As a result, the temperature rise in the non-passing area is suppressed. Then, when the detection temperature of the sub-thermistor TH2 drops to a predetermined temperature by being cooled by the cooling air of the cooling fan, the operation of the cooling fans 52L / 52R is stopped.

The temperature range of ON-OFF control based on the detection temperature of TH2 of the sub-thermistors of the cooling fans 52L and 52R is controlled to be changed according to the operating condition of the cooling fan.

The ON-OFF control temperature range of the cooling fans 52L / 52R in this embodiment is controlled as follows, for example, when 100 sheets of B4 size paper (medium size paper) are continuously passed. That is, when the number of sheets to be passed is 0 to 30, when the operation start temperature of the cooling fans 52L / 52R reaches 200 ° C., the stop temperature of the cooling fan is the detection temperature of the sub thermistor. Perform when the temperature reaches 190 ° C. When the number of sheets is 31 to 60, the operating temperature of the cooling fan is similarly set at 205 ° C. for the start and 195 ° C. for the stop. After that, the start temperature and the stop temperature of the cooling fan are raised by 5 ° C. every 30 sheets.

Here, FIG. 11 shows the longitudinal temperature distribution when 100 sheets of A4R in this embodiment are passed. The solid line is the longitudinal temperature distribution of this example, and the broken line is the longitudinal temperature distribution when the shape of the opening of the comparative example is the same in the longitudinal direction. In the comparative example, since the air volume flowing through the fixing film 33 is non-uniform at the openings Lb and Rb, the longitudinal temperature distribution has temperature unevenness at a position close to the non-paper-passing region in the paper-passing region. In this embodiment, by changing the shape of the openings Lb and Rb in the longitudinal direction and changing the opening height, the occurrence of temperature unevenness in the paper-passing area is suppressed.

The reason for this will be described with reference to FIGS. 12 (a) and 12 (b). 12 (a) shows the air volume distribution flowing from the front opening Rb at the position of FIG. 1 to the fixing film 33, and FIG. 12 (b) shows the air volume distribution flowing from the back opening Lb at the position of FIG. 1 to the fixing film 33. Is. In the comparative example, the opening Lb / Rb has uneven air volume in the longitudinal direction, whereas in this embodiment, the shape of the opening Lb / Rb is changed in the longitudinal direction, so that the opening height is changed in the longitudinal direction. The air volume is uniform. The opening height of the openings Lb / Rb at the position where the air volume of the cooling fan is strong is lowered, and the opening height of the openings Lb / Rb at the position where the air volume of the cooling fan is weak is increased. Therefore, the fixing film 33 can be cooled uniformly, and the temperature unevenness in the paper-passing area can be improved.

FIG. 13 is an exploded perspective view of the blower cooling mechanism unit 20B in this embodiment. 14 (a), (b), and (c) are explanatory views of the operation of the shutter plate when passing small size, medium size, and large size paper. In this embodiment, the shapes of the left and right openings Lb / Rb are different. In Example 1, the openings Lb / Rb are longitudinal and the opening heights are different, whereas in this embodiment, the openings Lb / Rb are different. It is configured to be the same as that of the first embodiment except that the opening density is different in the longitudinal direction. Therefore, overlapping description will be omitted for the configuration common to the first embodiment.

Here, FIG. 11 shows the longitudinal temperature distribution when 100 sheets of A4R in this embodiment are passed. The solid line is the longitudinal temperature distribution of this example, and the broken line is the longitudinal temperature distribution when the shape of the opening of the comparative example is the same in the longitudinal direction. In the comparative example, since the air volume flowing through the fixing film 33 is non-uniform at the openings Lb and Rb, the longitudinal temperature distribution has temperature unevenness at a position close to the non-paper-passing region in the paper-passing region. In this embodiment, the occurrence of temperature unevenness in the paper-passing area was suppressed by changing the opening density in the longitudinal direction of the openings Lb and Rb.

The reason for this will be described with reference to FIGS. 12 (a) and 12 (b). 12 (a) shows the air volume distribution flowing from the front opening Rb at the position of FIG. 1 to the fixing film 33, and FIG. 12 (b) shows the air volume distribution flowing from the back opening Lb at the position of FIG. 1 to the fixing film 33. Is. In the comparative example, there is unevenness in the air volume in the longitudinal direction in the openings Lb / Rb, whereas in this embodiment, the opening density is changed in the longitudinal direction in the shape of the openings Lb / Rb, so that the air volume in the longitudinal direction is changed. Is uniform. The opening densities of the openings Lb and Rb at the position where the air volume of the cooling fan is strong are sparse, and the opening densities of the openings Lb and Rb at the position where the air volume of the cooling fan is weak are made dense. Therefore, the fixing film 33 can be cooled uniformly, and the temperature unevenness in the paper-passing area can be improved.

1) The fixing mechanism unit 20A is not limited to the belt heating method and the pressure rotating body drive method of the above embodiment, but may be a thermal roller method or another method. It can also be an electromagnetic induction heating type device.

33 Fixing film 32 Pressurizing roller Lb / Rb Opening 52L / 52R Blower cooling means 53L / 53R Shutter 100 Fixing device

Claims (3)

It has a fixing member, a pressure member, an opening for cooling a predetermined area of the fixing member 33, a blower cooling means for blowing air toward the opening, and a shutter for opening and closing the opening. A fixing device characterized in that the shape of the opening differs in length in the fixing device. The fixing according to claim 1, wherein the opening has a low opening height in a region where the air volume of the blower cooling means is large, and a high opening height in a region where the air volume of the blower cooling means is low. Device. The fixing device according to claim 1, wherein the opening has a low opening density in a region where the air volume of the blower cooling means is large, and a high opening density in a region where the air volume of the blower cooling means is low.

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