JP2014071142A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to cool a rotating body without causing rotation failure or wear of the rotating body, while being compatible with a high-speed image forming apparatus.SOLUTION: A fixing apparatus 16 includes: a rotating body 21 having a nip part 29 for heating a toner image on a recording material S; and cooling means 22 for cooling the rotating body 21. The cooling means 22 cools the rotating body 21 by bringing cooling liquid into contact with the rotating body 21.

Description

  The present invention relates to a fixing device that fixes a toner image on a recording material and an image forming apparatus including the fixing device.

  Conventionally, in a fixing device provided in an electrophotographic image forming apparatus (for example, a printer, a copier, etc.), a rotating body (for example, a fixing roller) having a heater therein and another rotating body (for example, a pressure roller) ) Is press-contacted to form a nip portion. The toner image transferred onto the recording material (for example, paper) is heated and pressed at the nip portion, so that the toner image is permanently fixed on the recording material. For the purpose of improving energy consumption efficiency and fixing property, there is also a fixing device using an IH coil for induction heating of a metal member as a heat source instead of using the heater as a heat source.

  In any of these types of fixing devices, toner images are fixed on recording materials having various widths at the nip portion in accordance with user needs. For example, when a recording material having a narrow width with respect to the heat generation area of the rotating body (for example, a recording material of the minimum size, hereinafter referred to as “first size recording material”) is used, the outer peripheral surface of the rotating body. Among them, in the region through which the recording material of the first size passes (hereinafter referred to as “first size passage region”), the heat of the rotating body is taken away. On the other hand, in a region where a recording material of a second size having a width larger than that of the recording material of the first size passes outside the first size passage region (hereinafter referred to as “first size non-passing region”). The heat of the rotating body is not lost. For this reason, the first size non-passing region is excessively heated with respect to the first size passing region.

  Thus, when the first size non-passing region is excessively heated, the deterioration of the rotating body is accelerated. Further, when the toner image is fixed to the recording material of the second size after the temperature of the first size non-passing region is excessively heated, the toner on the recording material adheres to the rotating body and stains the image. An “offset” occurs in the first size non-passing region.

  In order to solve these problems, Patent Document 1 discloses that a cooling roller (see “rollers 14a and 14b”) in which a fluid flows is brought into contact with a rotating body (see “pressure roller 13”). A technique for depriving the heat of the passage area and preventing the first size non-passage area from being excessively heated is disclosed.

JP 2006-206881 A

  However, the above prior art has the following problems. First, in the configuration in which the cooling roller is brought into contact with the rotating body, the cooling area cannot be changed according to various sizes of the recording material because the range in which the cooling roller takes heat from the rotating body is constant. There is. Moreover, since the cooling roller and the rotating body are in contact with each other, rotation failure of the rotating body may occur. Further, when the torque increases due to the contact between the cooling roller and the rotating body, wear of the rotating body is promoted. In particular, when the rotator is rotated at a high speed, the rotator becomes extremely worn, and thus there is a problem that it is difficult to cope with the increase in the speed of the image forming apparatus.

  The present invention has been made in view of the above-described problems of the prior art, and can fix a rotating body without causing rotation failure or wear of the rotating body, and can also cope with a high speed image forming apparatus. The purpose is to provide.

  The present invention is a fixing device including a rotating body that forms a nip portion for heating a toner image on a recording material, and a cooling unit that cools the rotating body, and the cooling unit includes the rotating body. The rotating body is cooled by bringing a coolant into contact therewith.

  By comprising in this way, a rotary body can be cooled, without making a rotary body and the member which comprises a cooling means contact. For this reason, it is possible to prevent rotation failure and wear of the rotating body due to contact between the rotating body and the members constituting the cooling means, and accordingly, it is possible to obtain a good output image. In addition, even when the rotating body is rotated at a high speed, the rotating body is not worn, and therefore, it is possible to cope with an increase in the speed of the image forming apparatus.

  The cooling means may include a tank that stores the cooling liquid, and a spray mechanism that sprays the cooling liquid discharged from the tank toward the rotating body.

  By comprising in this way, it becomes possible to spray a cooling liquid toward a rotary body with a simple structure, and to cool a rotary body.

  The cooling means may include a duct connected to the tank, and a blowing means for guiding water vapor generated when the recording material passes through the nip portion to the duct.

  With this configuration, the water vapor generated when the recording material passes through the nip portion can be collected in the tank and used as a cooling liquid. Therefore, it is not necessary to supply the cooling liquid to the tank from the outside of the image forming apparatus.

  The spray mechanism may include a nozzle that sprays the coolant in a mist toward the rotating body.

  Thus, it becomes possible to cool a rotary body uniformly by spraying a cooling fluid in the shape of a mist toward a rotary body. Therefore, it is possible to prevent a problem that only a part of the rotating body is rapidly cooled.

  The particle size of the coolant sprayed from the nozzle toward the rotating body may be 1 mm or less.

  By adopting such a configuration, the rotating body can be cooled more uniformly.

  A first size passing area through which the first size recording material passes, and a second size recording material having a width larger than the first size recording material outside the first size passing area are provided on the outer peripheral surface of the rotating body. And a first size non-passing region through which the coolant passes, and the spray mechanism may spray the coolant toward the first size non-passing region.

  With this configuration, it is possible to efficiently cool only the first size non-passing region, and it is possible to prevent the temperature of the first size passing region from being unnecessarily lowered.

  The spray mechanism may include a spray port that is opened toward the first size non-passing region, and a shutter that changes an opening width of the spray port in the width direction of the recording material.

  With this configuration, it is possible to change the opening width of the spray port in accordance with the first size non-passing region that changes for each size of the recording material. Therefore, it is possible to cope with recording materials of various sizes with a single fixing device, and it is possible to improve productivity.

  The spray mechanism may be disposed on the downstream side of the nip portion in the recording material conveyance direction, and may be positioned on the opposite side of the rotating body via the recording material conveyance path.

  With this configuration, the rotating body can be cooled over the first size recording material when the first size recording material is conveyed along the conveyance path. Therefore, the cooling liquid can be sprayed only on the first size non-passing area, and the temperature of the first size passing area can be prevented from being unnecessarily lowered due to the cooling liquid spraying on the first size passing area. It becomes. Further, since the recording material can be cooled by the cooling liquid sprayed on the recording material, the recording materials discharged to the tray can be prevented from sticking to each other.

  After stopping the contact of the coolant with the rotating body, the rotating body may be rotated for a predetermined time.

  By comprising in this way, it becomes possible to vaporize the cooling liquid adhering to a rotary body more rapidly.

  The cooling means may be provided in the vicinity of the rotating body with an interval from the rotating body.

  By comprising in this way, abrasion of the rotary body by contact with the member which comprises a cooling means can be prevented reliably.

  The rotating body may be a pressure roller.

  With this configuration, when adopting a configuration in which the temperature of the fixing roller is detected by the temperature detection means, the influence of the cooling liquid on the temperature detection is reduced, and the temperature of the fixing roller is detected more accurately. Is possible.

  The rotating body may be a fixing roller.

  With this configuration, it is possible to intensively cool the fixing roller that is particularly likely to increase in temperature.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, it is possible to provide a fixing device that can cool a rotating body without causing rotation failure or wear of the rotating body, and can cope with a high speed image forming apparatus.

1 is a schematic diagram illustrating an outline of a printer according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device of a printer according to a first embodiment of the present invention. It is AA sectional drawing of FIG. 1 is a block diagram illustrating a configuration of a printer according to a first embodiment of the present invention. It is sectional drawing which shows the fixing device of the printer which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the fixing device of the printer which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the fixing device of the printer which concerns on the 3rd Embodiment of this invention. In the fixing device of the printer according to the third embodiment of the present invention, (a) is a bottom view showing a state in which the shutter closes the spray port, and (b) is a shutter having a width corresponding to the A4 size. It is a bottom view which shows the state which opened the spray outlet, (c) is a bottom view which shows the state which the shutter opened only the width | variety corresponding to A5 size.

<First Embodiment>
First, the overall configuration of a printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating an outline of a printer according to a first embodiment of the present invention. Hereinafter, the front side in FIG. 1 is defined as the front side (front side) of the printer 1.

  The printer 1 includes a box-shaped printer main body 2, and a paper feed cassette 3 for storing paper (not shown) as a recording material is provided at a lower portion of the printer main body 2. Is provided with a paper discharge tray 4.

  An exposure unit 5 composed of a laser scanning unit (LSU) is arranged at the upper right part of the printer main body 2, and an image forming unit 6 is provided at the left part of the printer main body 2. The image forming unit 6 is rotatably provided with a photosensitive drum 7 serving as an image carrier. Around the photosensitive drum 7, a charger 8 and a developing unit 10 connected to a toner container 9 are provided. The transfer roller 11 and the cleaning device 12 are arranged along the rotation direction of the photosensitive drum 7 (see arrow X in FIG. 1).

  A paper transport path 13 is provided on the left side of the printer main body 2 from below to above. That is, the printer 1 of this embodiment is a vertical conveyance. A paper feeding unit 14 is provided at the upstream end of the conveyance path 13, and a transfer unit 15 configured by the photosensitive drum 7 and the transfer roller 11 is provided at a middle portion of the conveyance path 13, and a downstream part of the conveyance path 13. Is provided with a fixing device 16. On the left side of the conveyance path 13, a reverse path 17 for double-sided printing is provided.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing device 16 is executed. Then, when image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 7 is charged by the charger 8, exposure corresponding to image data is performed on the photosensitive drum 7 by laser light from the exposure device 5 (see arrow P in FIG. 1). Then, an electrostatic latent image is formed on the surface of the photosensitive drum 7. Next, the developing unit 10 develops the electrostatic latent image into a toner image with the toner supplied from the toner container 9.

  On the other hand, the sheet taken out from the sheet cassette 3 by the sheet feeding unit 14 is conveyed to the transfer unit 15 in synchronization with the above-described image forming operation, and the toner image on the photosensitive drum 7 is transferred to the sheet by the transfer unit 15. Is transcribed. The sheet on which the toner image has been transferred is conveyed downstream in the conveying path 13 and enters the fixing device 16 where the toner image is fixed on the sheet. The sheet on which the toner image is fixed is discharged from the downstream end of the conveyance path 13 to the discharge tray 4. The toner remaining on the photosensitive drum 7 is collected by the cleaning device 12.

  Next, the configuration of the fixing device 16 will be described with reference to FIGS. 2 and 3. Hereinafter, when the paper size is referred to as B5, A4, A3, etc., the vertical size of the paper is used as a reference. Note that an arrow Fr in FIG. 3 indicates the front side (front side) of the fixing device 16.

  As shown in FIGS. 2 and 3, the fixing device 16 includes a fixing roller 20, a pressure roller 21 as a rotating body arranged on the left side of the fixing roller 20, and an upper left side of the pressure roller 21. A pair of conveyance guides 23 provided above the fixing roller 20 and the pressure roller 21, and a pair of conveyance rollers 24 provided further above the pair of conveyance guides 23. Yes. Hereinafter, these will be described in order.

  First, the fixing roller 20 will be described. The fixing roller 20 has a long shape in the front-rear direction. The fixing roller 20 includes, for example, a cylindrical core material made of a metal such as aluminum or iron, an elastic layer made of silicon rubber or the like provided around the core material, and a fluorine resin such as PFA covering the elastic layer. And a release layer. The fixing roller 20 is rotatably accommodated in a box-shaped fixing frame (not shown). Inside the fixing roller 20, a heater 25 constituted by, for example, a halogen heater or a ceramic heater is accommodated.

  As shown in FIG. 3, the first size paper (for example, B5 size or A4 size paper) passes through a portion (center image area) extending from the front to the rear of the outer peripheral surface 26 of the fixing roller 20. A first size passage region L1 is formed. A first thermistor 27 is provided in the first size passage region L 1 of the fixing roller 20. The first thermistor 27 is a non-contact type temperature detection unit that is disposed at a predetermined distance from the outer peripheral surface 26 of the fixing roller 20.

  On the outer peripheral surface 26 of the fixing roller 20, a second size paper (for example, an A3 size paper) having a front and rear width larger than that of the first size paper is provided on both front and rear sides of the first size passage region L1 (outside the first size passage region L1). A first size non-passing region L2 through which a sheet (paper) passes is formed. A second thermistor 28 is provided in the first size non-passing region L <b> 2 on the rear side of the fixing roller 20. The second thermistor 28 is contact-type temperature detection means that contacts the outer peripheral surface 26 of the fixing roller 20.

  Next, the pressure roller 21 will be described. Similar to the fixing roller 20, the pressure roller 21 has a shape that is long in the front-rear direction. The pressure roller 21 includes, for example, a cylindrical core material made of a metal such as aluminum or iron, an elastic layer made of silicon rubber or the like provided around the core material, and fluorine such as PFA that covers the elastic layer. And a release layer made of resin.

  The pressure roller 21 is rotatably accommodated in a fixing frame (not shown) together with the fixing roller 20. The pressure roller 21 is in pressure contact with the fixing roller 20 by an urging force of an urging means (not shown), and is configured to be driven and rotated in the opposite direction to the fixing roller 20 as the fixing roller 20 rotates. ing. A nip portion 29 is formed between the fixing roller 20 and the pressure roller 21. The nip portion 29 conveys the paper on which the toner image is formed, and heats and presses the toner image on the paper. It is fixed on the paper. 2 and FIG. 3 indicate the first size paper passing through the nip portion 29.

  A first size passage region M1 through which a first size paper (for example, a B5 size paper or an A4 size paper) passes is formed in a portion extending from the front portion to the rear portion of the outer peripheral surface 30 of the pressure roller 21. On the outer peripheral surface 30 of the pressure roller 21, a second size paper (for example, A3 size) having a front and rear width larger than that of the first size paper on both front and rear sides of the first size passage region M1 (outside the first size passage region M1) The first size non-passing area M2 is formed.

  Next, the cooling means 22 will be described. As shown in FIG. 2, the cooling unit 22 is disposed in the vicinity of the fixing roller 20 and the pressure roller 21. The cooling unit 22 is provided at a predetermined interval from the fixing roller 20 and the pressure roller 21. In other words, the cooling unit 22 is not in contact with the fixing roller 20 and the pressure roller 21.

  The cooling means 22 includes a tank 31 disposed on the left side of the pressure roller 21, eight spraying mechanisms 32 disposed below the tank 31, a duct 33 disposed above the tank 31, And a fan 34 as air blowing means disposed on the right side of the duct 33 with the conveyance path 13 interposed therebetween.

  As shown in FIG. 2, the tank 31 has a box shape with an upper surface opened. The tank 31 contains water as a coolant. A discharge opening 35 communicating with outside air is provided on the left side of the upper surface side of the tank 31. As shown in FIG. 3, the tank 31 is provided at the center in the front-rear direction of the fixing roller 20 and the pressure roller 21. A connecting pipe 36 is connected to the bottom of the tank 31. The connecting pipe 36 extends in the front-rear direction. Four branch portions 37 are provided at the front end portion and the rear end portion of the connection pipe 36, respectively.

  Each spray mechanism 32 includes a pump 38 connected to each branch portion 37 of the connection pipe 36 and a nozzle 40 protruding rightward from the pump 38. The nozzles 40 of the four blowing mechanisms 32 on the front side face the first size non-passing region M2 on the front side of the pressure roller 21. The nozzles 40 of the four spray mechanisms 32 on the rear side face the first size non-passing region M <b> 2 on the rear side of the pressure roller 21.

  As shown in FIG. 2, the exhaust side end portion (left end portion in the present embodiment) of the duct 33 is connected to the tank 31 and covers from the left side portion to the right end portion of the upper surface of the tank 31. An end portion on the intake side (right end portion in the present embodiment) of the duct 33 faces the sheet conveyance path 13. The inner peripheral surface 41 of the duct 33 is inclined downward toward the exhaust side (left side in the present embodiment). Similar to the tank 31, the duct 33 is provided at the center in the front-rear direction of the fixing roller 20 and the pressure roller 21 (see FIG. 3).

  As shown in FIG. 2, the fan 34 is disposed on the upper right side of the fixing roller 20. The fan 34 is disposed on the opposite side of the duct 33 with the sheet conveyance path 13 interposed therebetween. Similar to the tank 31 and the duct 33, the fan 34 is provided in the center in the front-rear direction of the fixing roller 20 and the pressure roller 21 (see FIG. 3).

  Next, the pair of conveyance guides 23 will be described. As shown in FIG. 2, the pair of conveyance guides 23 are arranged on both the left and right sides of the sheet conveyance path 13. The pair of conveyance guides 23 are provided along the sheet conveyance path 13 so that the sheet having passed through the fixing nip 29 can be guided by the pair of conveyance guides 23. The pair of conveyance guides 23 are inclined so as to approach the sheet conveyance path 13 toward the downstream side (the upper side in the present embodiment). The pair of conveyance guides 23 are provided with a plurality of holes 39 for forming an air path from the fan 34 to the duct 33.

  Next, the pair of transport rollers 24 will be described. The pair of transport rollers 24 are arranged on both the left and right sides of the sheet transport path 13. A conveyance nip 42 is formed between the pair of conveyance rollers 24 along the sheet conveyance path 13.

  Next, the control system of the printer 1 will be described with reference to FIG.

  The printer 1 is provided with a control unit 43. The control unit 43 is connected to a storage unit 44 configured by a storage device such as a ROM or a RAM, and the control unit 43 controls each unit of the printer 1 based on a control program and control data stored in the storage unit 44. It is comprised so that control may be performed.

  The controller 43 is connected to the first thermistor 27 provided in the first size passage region L1 of the fixing roller 20, and the temperature of the first size passage region L1 of the fixing roller 20 detected by the first thermistor 27. Is output to the control unit 43. The control unit 43 is connected to the second thermistor 28 provided in the first size non-passing area L2 on the rear side of the fixing roller 20, and the first size non-detection of the fixing roller 20 detected by the second thermistor 28 is connected. The temperature of the passage region L <b> 2 is output to the control unit 43.

  The control unit 43 is connected to a pump 38 provided in the spray mechanism 32 of the cooling means 22. The pump 38 is configured to operate based on an operation command signal from the control unit 43.

  The control unit 43 is connected to the voltage supply unit 45, and the voltage supply unit 45 is connected to the heater 25 in the fixing roller 20. When a voltage is applied from the voltage supply unit 45 to the heater 25 based on a signal from the control unit 43, the heater 25 is energized to generate heat and the fixing roller 20 is heated.

  The control unit 43 is connected to the fan 34 of the cooling means 22. And it is comprised so that the fan 34 may drive based on the signal from the control part 43. FIG.

  The control unit 43 is connected to a driving unit 46 configured by a motor or the like, and the driving unit 46 is connected to the fixing roller 20. The drive unit 46 is configured to rotate the fixing roller 20 based on a drive command signal from the control unit 43.

  In the configuration as described above, when the toner image is fixed on the sheet, the voltage supply unit 45 applies a voltage to the heater 25 based on a signal from the control unit 43. With this voltage, the heater 25 is energized to generate heat, and the fixing roller 20 is heated.

  In addition, the first thermistor 27 detects the temperature of the first size passage region L 1 of the fixing roller 20 and outputs it to the control unit 43. The controller 43 controls the voltage applied from the voltage supply unit 45 to the heater 25 based on the temperature of the first size passage region L1 of the fixing roller 20 output from the first thermistor 27. As a result, the fixing roller 20 is maintained at a temperature at which the toner image can be fixed to the paper.

  By the way, when the toner image is fixed on the second size paper (the size suitable for the heating width of the heater 25), heat is taken away from the entire area of the fixing roller 20 by the second size paper. The 20 first size non-passing region L2 is not excessively heated with respect to the first size passing region L1. On the other hand, when the toner image is continuously fixed on the first size paper, heat is taken away in the first size passage region L1 of the fixing roller 20, whereas the first size of the fixing roller 20 is not. Heat is not taken away in the passage region L2. Therefore, when the number of continuous sheets increases, the first size non-passing area L2 of the fixing roller 20 is excessively heated with respect to the first size passing area L1. Such a phenomenon also occurs in the first size passing area M1 and the first size non-passing area M2 of the pressure roller 21.

  As described above, when the first size non-passing region L2 of the fixing roller 20 is excessively heated and the temperature of the first size non-passing region L2 of the fixing roller 20 detected by the second thermistor 28 reaches a predetermined temperature. The control unit 43 operates the pumps 38 provided in the spray mechanisms 32 of the cooling unit 22. The pumps 38 may be operated at the same time by operating the pumps 38 of all eight spraying mechanisms 32, or a part of the eight pumps 38 depending on the size of the paper on which continuous paper is being passed. Only the pump 38 of the spray mechanism 32 may be selectively operated.

  When the pump 38 is operated in this way, the water in the tank 31 is discharged to the connecting pipe 36 and supplied from the connecting pipe 36 to each blowing mechanism 32. Thus, the water supplied to each spray mechanism 32 is sprayed in the form of a mist from the nozzle 40 of each spray mechanism 32 toward the first size non-passage region M2 of the pressure roller 21 (arrows in FIGS. 2 and 3). a)). In the present embodiment, the shape of the nozzle 40, the pressure of the pump 38, and the like are adjusted so that the water particle size at this time is 1 mm or less.

  Thus, a part of the water sprayed toward the first size non-passage area M2 of the pressure roller 21 contacts the outer peripheral surface 30 of the pressure roller 21 and evaporates by the heat of the pressure roller 21, The first size non-passing area M2 of the pressure roller 21 is cooled by the heat of vaporization. Along with this, the first size non-passing region L2 of the fixing roller 20 that contacts the first size non-passing region M2 of the pressure roller 21 is also cooled.

  Further, another part of the water sprayed toward the first size non-passing region M2 of the pressure roller 21 comes into contact with the first size non-passing region M2 of the pressure roller 21 in a liquid state, and then pressed. The roller 21 moves from the first size non-passing region M2 to the first size non-passing region L2 of the fixing roller 20. Then, the first size non-passing region L2 of the fixing roller 20 contacts and evaporates, and the heat of vaporization cools the first size non-passing region L2 of the fixing roller 20.

  When the first size non-passing region L2 of the fixing roller 20 is cooled in this way, the temperature of the first size non-passing region L2 of the fixing roller 20 detected by the second thermistor 28 is stored in the storage unit 44. Below the set temperature. Along with this, the control unit 43 stops the operation of the pump 38 of the cooling means 22, and the spraying of water from the nozzle 40 to the first size non-passing region M <b> 2 of the pressure roller 21 is also stopped.

  The control unit 43 rotates the fixing roller 20 and the pressure roller 21 by the driving unit 46 for a certain period of time even after the spraying of water from the nozzle 40 to the first size non-passage region M2 of the pressure roller 21 is stopped. . By this rotation, all the water adhering to the fixing roller 20 and the pressure roller 21 is vaporized and discharged outside the printer 1. As a result, the fixing roller 20 and the pressure roller 21 are restored to the initial state (the dried state).

  In the present embodiment, as described above, since the pressure roller 21 is cooled by bringing water into contact with the pressure roller 21, members constituting the pressure roller 21 and the cooling means 22 (for example, the tank 31 and the spraying) The pressure roller 21 can be cooled without contacting the mechanism 32). Therefore, it is possible to prevent the rotation failure and wear of the pressure roller 21 due to the contact between the pressure roller 21 and the members constituting the cooling means 22, and accordingly, it is possible to obtain a good output image. . Further, even when the pressure roller 21 is rotated at a high speed, the pressure roller 21 is not worn, so that the printer 1 can be adapted to increase the speed.

  Further, since the cooling means 22 includes the tank 31 and the spray mechanism 32, it is possible to cool the pressure roller 21 by spraying water toward the pressure roller 21 with a simple configuration.

  In addition, since the spray mechanism 32 includes the nozzle 40 that sprays water toward the pressure roller 21 in the form of a mist, the pressure roller 21 can be uniformly cooled. Therefore, it is possible to prevent a problem that only a part of the pressure roller 21 is rapidly cooled. Especially in this embodiment, since the particle size of the water sprayed toward the pressure roller 21 from the nozzle 40 is 1 mm or less, the pressure roller 21 can be cooled more uniformly.

  In addition, since the spray mechanism 32 is configured to spray water toward the first size non-passing region M2 of the pressure roller 21, only the first size non-passing region M2 can be efficiently cooled, and the first size. It is possible to prevent the temperature of the passage region M1 from being unnecessarily lowered. Such an effect is also exhibited in the first size passing area L1 and the first size non-passing area L2 of the fixing roller 20.

  Further, even after the spraying of water from the nozzle 40 to the first size non-passage region M2 of the pressure roller 21 is stopped, the fixing roller 20 and the pressure roller 21 are rotated by the driving unit 46 for a certain time. Therefore, it is possible to vaporize water adhering to the fixing roller 20 and the pressure roller 21 more quickly.

  The cooling unit 22 is provided in the vicinity of the fixing roller 20 and the pressure roller 21 with a predetermined distance from the fixing roller 20 and the pressure roller 21. Therefore, wear of the fixing roller 20 and the pressure roller 21 due to contact with members constituting the cooling unit 22 can be reliably prevented.

  Further, the temperature of the fixing roller 20 is detected by the first and second thermistors 27 and 28 by blowing water from the nozzle 40 toward the pressure roller 21 as compared with the case of blowing water toward the fixing roller 20. The effect of water on water can be reduced. Therefore, the temperature of the fixing roller 20 can be detected more accurately.

  By the way, when the sheet passes through the nip portion 29, moisture in the sheet is released as water vapor (see the two-dot chain line in FIG. 2). In the present embodiment, this water vapor is used for cooling the fixing roller 20 and the pressure roller 21. This point will be described below.

  When the toner image is fixed on the sheet, the fan 34 is driven by a signal from the control unit 43. When the fan 34 is driven in this manner, outside air is taken in by the fan 34 and cooling air is blown from the fan 34 toward the duct 33 as indicated by a dotted line in FIG. The cooling air passes through a plurality of holes 39 provided in the pair of conveyance guides 23 and travels toward the duct 33 to guide the water vapor generated from the nip portion 29 to the duct 33 while cooling. A part of the water vapor guided to the duct 33 by the cooling air is liquefied and contacts the inner peripheral surface 41 of the duct 33 to cause condensation (see arrow b in FIG. 2). Thereafter, it flows down into the tank 31. Further, another part of the water vapor led to the duct 33 by the cooling air comes into contact with the water in the tank 31 as the water vapor, and is cooled and liquefied by this contact and absorbed by the water in the tank 31. The The water vapor collected in the tank 31 in this way is used for cooling the pressure roller 21. A part of the water vapor is discharged out of the printer 1 through the discharge opening 35 as a gas.

  In the present embodiment, as described above, the water vapor generated when the paper passes through the nip portion 29 can be collected in the tank 31 and used as water for cooling the pressure roller 21. Therefore, it is not necessary to supply water to the tank 31 from the outside of the printer 1.

  Further, water vapor generated when the paper passes through the nip portion 29 is collected in the tank 31, so that dew condensation on members (for example, the conveyance guide 23 and the conveyance roller 24) disposed in the vicinity of the conveyance path 13 of the paper is prevented. Can be prevented. For this reason, it is possible to prevent the condensed moisture from reattaching to the sheet and causing a defective image or the like.

  In the present embodiment, a case where the control unit 43 stops the pump 38 of the cooling unit 22 when the temperature of the first size non-passing region L2 of the fixing roller 20 detected by the second thermistor 28 is lower than the set temperature. explained. On the other hand, in another different embodiment, the first size non-passing region of the fixing roller 20 is detected even after the temperature of the first size non-passing region L2 of the fixing roller 20 detected by the second thermistor 28 is lower than the set temperature. The driving of the pump 38 may be continued under the control of the control unit 43 so that L2 becomes equal to or lower than a predetermined temperature. In this case, for example, the duty ratio of the pump 38 may be determined by taking in a difference between the set temperature and the detected temperature and a temperature transition and performing feedback control.

  In the present embodiment, a non-contact type first thermistor 27 is disposed in the first size passage region L 1 of the fixing roller 20, and a contact type second thermistor 28 is disposed in the first size passage region L 2 of the fixing roller 20. Explained when to do. On the other hand, in other different embodiments, temperature detecting means such as a thermistor may be disposed only in the first size non-passing region L2 of the fixing roller 20. In this case, the cooling means 22 may be driven after a predetermined time set for each size has elapsed or after a predetermined time has elapsed since the duty ratio of the heater 25 falls below a certain value. With this configuration, only the first size non-passing region L2 is cooled at the timing when the temperature difference between the first size passing region L1 and the first size non-passing region L2 becomes large, and the first size passing region L2 is cooled. The temperature difference between L1 and the first size non-passing region L2 can be reduced. Along with this, the output of the heater 25 can be recovered, and the temperature of the first size passage region L1 can be prevented from decreasing more than necessary.

  In the present embodiment, the case where the water is made into a mist using the pump 38 and the nozzle 40 has been described. However, in another different embodiment, the coolant is mist-like by ultrasonically vibrating the coolant such as water. It is also good.

  In the present embodiment, the case where the heater 25 is used as the heat source has been described. However, in another different embodiment, another heat source such as an IH coil may be used.

  In this embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine. It is also possible.

<Second Embodiment>
Next, a fixing device 51 according to a second embodiment of the present invention will be described with reference to FIGS. In addition, since it is the same as that of 1st Embodiment about structures other than the cooling means 52, the same number as 1st Embodiment is attached | subjected on drawing, and description is abbreviate | omitted. An arrow Fr in FIG. 6 indicates the front side (front side) of the fixing device 51.

  As shown in FIGS. 5 and 6, the cooling means 52 includes a tank 53 disposed above the pressure roller 21 and a spray mechanism 54 connected to the tank 53. In FIG. 6, the tank 53 is not shown.

  In the tank 53, water as a coolant is accommodated. This water may be collected water vapor generated when the paper passes through the nip portion 29 (see the first embodiment), or a water supply portion (not shown) provided in the printer main body 2. ).

  The spray mechanism 54 is disposed on the downstream side (upper side in the present embodiment) of the nip portion 29 in the sheet conveyance direction, and is positioned on the opposite side of the fixing roller 20 as a rotating body via the sheet conveyance path 13. ing. The spray mechanism 54 includes a pump 55 and a nozzle 56 connected to the pump 55. As shown in FIG. 6, the nozzle 56 has a shape that is long in the front-rear direction, and extends from the front end side to the rear end side of the fixing roller 20 and the pressure roller 21. A number of spray holes (not shown) are arranged in the nozzle 56 from the front end side to the rear end side.

  When the toner image is fixed on the first size paper (see the arrow S in FIGS. 5 and 6), the first size paper passes through the nip 29 when the toner image is fixed on the first size paper. Then, the pump 55 is driven. When the pump 55 is thus operated, the water in the tank 53 is supplied to the spray mechanism 54, and passes through the first size paper from the spray holes of the nozzle 56 of the spray mechanism 54 toward the entire area of the fixing roller 20. Sprayed in the form of a mist (see arrow c in FIGS. 5 and 6). In the present embodiment, the shape of the nozzle 56, the pressure of the pump 55, and the like are adjusted so that the water particle size at this time is 1 mm or less.

  The water sprayed from the nozzle 56 toward the first size passage region L1 of the fixing roller 20 contacts the back surface of the first size paper passing through the conveyance path 13 and cools the first size paper. Further, the water sprayed from the nozzle 56 toward the first size non-passing area L2 of the fixing roller 20 contacts the first size non-passing area L2 of the fixing roller 20 without contacting the first size paper, It evaporates by the heat of the fixing roller 20, and the first size non-passing area L2 of the fixing roller 20 is cooled by the heat of vaporization.

  In the present embodiment, as described above, the fixing roller 20 can be cooled over the first size sheet. Therefore, it is possible to cool the paper with the water sprayed from the nozzle 56, and it is possible to prevent the paper discharged to the paper discharge tray 4 from sticking to each other.

  In addition, the paper after passing through the nip portion 29 is heated by the fixing roller 20 to evaporate moisture, thereby reducing the water content and increasing the temperature. If double-sided printing is performed on the high-temperature paper, the high-temperature paper is conveyed to the image forming unit 6, and accordingly, the developing unit 10 and the photosensitive drum 7 are excessively moved. There is a risk that the temperature will rise. When the temperature of the developing unit 10 is excessively increased in this way, toner condensation occurs in the developing unit 10 and the sleeve provided in the developing unit 10 is clogged, causing white streaks on the image. There is a fear. In addition, there is a possibility that the toner unit may be locked due to melting of the developing unit 10 or the rotating portion of the photosensitive drum 7. Further, the resistance of the sheet becomes extremely high in the transfer portion 15, and the toner in the portion where the current is concentrated may be scattered, and this portion may become a white spot on the image. However, in this embodiment, since moisture is supplied from the back side of the paper, the temperature of the paper can be lowered and the moisture content of the paper can be appropriately recovered, causing various problems as described above. Can be prevented.

  Further, the first size passage region L1 of the fixing roller 20 is blocked by the paper. Therefore, water can be sprayed only on the first size non-passing region L2 of the fixing roller 20, and water is sprayed on the first size passing region L1, and the temperature of the first size passing region L1 is unnecessarily lowered. It becomes possible to prevent. Further, the widths of the first size passing area L1 and the first size non-passing area L2 are automatically adjusted by the first size paper. Therefore, the fixing roller 20 can be maintained at an appropriate temperature regardless of the paper size.

  In addition, since the fixing roller 20 is configured to spray water, it is possible to intensively cool the fixing roller 20 that is particularly easily heated.

<Third Embodiment>
Next, a fixing device 61 according to a third embodiment of the present invention will be described with reference to FIGS. Since the configuration other than the cooling unit 62 is the same as that of the first embodiment, the description thereof is omitted.

  As shown in FIG. 7, the cooling means 62 includes a tank 63 disposed above the fixing roller 20 and the pressure roller 21, and a spray mechanism 64 connected to the tank 63. Water as a coolant is accommodated in the tank 63.

  The spray mechanism 64 includes a pump 66 connected to the tank 63, a nozzle 67 connected to the pump 66, a spray duct 71 connected to the nozzle 67, and a spray fan 72 provided at the upper end of the spray duct 71. And a shutter 73 provided at the lower end of the duct 71 for spraying.

  The blowing duct 71 is widened in a tapered shape downward. An introduction port 74 is provided at the center in the front-rear direction of the upper end of the blowing duct 71 (the end portion on the side away from the fixing roller 20). The portion from the upper part to the lower end part of the blowing duct 71 branches into a pair of front and rear branch duct parts 75, and the lower end part (the end part on the side close to the fixing roller 20) of each branch duct part 75 includes A spray port 76 is provided. The spray port 76 is opened toward the first size non-passing region L <b> 2 of the fixing roller 20. The spray port 76 has a rectangular shape (see FIG. 8).

  As shown in FIG. 7, the shutter 73 includes a covering plate 77 extending in the front-rear direction, a connecting plate 78 bent upward from both front and rear end portions of the covering plate 77, and a rotation provided at the upper end of the connecting plate 78. And a shaft 79.

  As shown in FIG. 8, inclined portions 81 are provided on both front and rear sides of the left edge portion 80 of the cover plate 77. The front inclined portion 81 is inclined rightward (downward in the drawing) toward the front (rightward in the drawing). The rear inclined portion 81 is inclined rightward (downward in the drawing) toward the rear (leftward in the drawing).

  The rotation shaft 79 is rotatably supported by a fixing frame (not shown), and the shutter 73 is configured to rotate about the rotation shaft 79. As shown in FIG. 8, the shutter 73 can change the opening width of the spray port 76 in the paper width direction (the front-rear direction in the present embodiment).

  When the toner image is fixed on the second size paper (for example, A3 size paper), the cover plate of the shutter 73 is configured as shown in FIG. 77 closes the blowing port 76 provided in each branch duct part 75 of the blowing duct 71. Further, the blowing fan 72 is stopped.

  On the other hand, when the toner image is fixed on the first size paper (for example, A4 size paper) having the front and rear width d1, and the first size non-passing area L2 of the fixing roller 20 is excessively heated. As shown in FIG. 8B, the shutter 73 is rotated about the rotation shaft 79 to open the spray port 76 by a predetermined opening width. At the same time, the blowing fan 72 is driven. Cooling air from the blowing fan 72 is blown from the blowing port 76 to the first size non-passing region L <b> 2 of the fixing roller 20.

  If the first size non-passing region L2 of the fixing roller 20 does not fall below the predetermined temperature even when the cooling air is blown in this way, the pump 66 is operated while the driving of the blowing fan 72 is continued. When the pump 66 is operated in this way, the water in the tank 63 is supplied to the spray mechanism 64 and is sprayed from the nozzle 67 of the spray mechanism 64 into the spray duct 71 through the introduction port 74. The water thus blown into the blowing duct 71 is guided to each branch duct portion 75 by the cooling air from the blowing fan 72 as shown by a two-dot chain line in FIG. The air is sprayed from the 75 spray ports 76 to the first size non-passing region L <b> 2 of the fixing roller 20. As a result, the first size non-passing region L2 of the fixing roller 20 is cooled.

  Further, the toner image is fixed on the first size paper (for example, A5 size paper) whose front-rear width is d2 smaller than d1, and the first size non-passing area L2 of the fixing roller 20 is excessively heated. In this case, as shown in FIG. 8C, the shutter 73 is further rotated around the rotation shaft 79 to further increase the opening width of the spray port 76. Then, water is sprayed onto the first size non-passing region L2 of the fixing roller 20 in the same procedure as that for fixing the toner image on the first size paper having the front-rear width d1.

  In the present embodiment, as described above, the opening width of the spray port 76 can be changed in accordance with the first size non-passing region L2 that changes for each paper size. Therefore, a single fixing device 61 can handle various sizes of paper, and productivity can be improved.

  In the present embodiment, the rotary shutter 73 is used. However, in another different embodiment, a slide shutter may be used.

1 Printer (image forming device)
13 Conveying path 16 Fixing device 20 Fixing roller (rotating body)
21 Pressure roller (rotating body)
22 Cooling means 26 Outer peripheral surface (fixing roller)
29 Nip part 30 Outer peripheral surface (Pressure roller)
31 Tank 32 Spraying Mechanism 33 Duct 34 Fan 38 Pump 40 Nozzle 51 Fixing Device 52 Cooling Means 53 Tank 54 Spraying Mechanism 55 Pump 56 Nozzle 61 Fixing Device 62 Cooling Means 63 Tank 64 Spraying Mechanism 66 Pump 67 Nozzle 73 Shutter 76 Spraying Port L1 1 size passing area (fixing roller)
L2 1st size non-passing area (fixing roller)
M1 1st size passage area (pressure roller)
M2 first size non-passing area (pressure roller)

Claims (13)

A fixing device comprising: a rotating body that forms a nip portion for heating a toner image on a recording material; and a cooling unit that cools the rotating body,
The fixing device, wherein the cooling unit cools the rotating body by bringing a coolant into contact with the rotating body. The cooling means is
A tank containing the coolant;
The fixing device according to claim 1, further comprising: a spraying mechanism that sprays the coolant discharged from the tank toward the rotating body. The cooling means is
A duct connected to the tank;
The fixing device according to claim 2, further comprising a blowing unit that guides water vapor generated when the recording material passes through the nip portion to the duct.   The fixing device according to claim 2, wherein the spray mechanism includes a nozzle that sprays the coolant in a mist toward the rotating body.   The fixing device according to claim 4, wherein a particle diameter of the coolant sprayed from the nozzle toward the rotating body is 1 mm or less. A first size passing area through which the first size recording material passes, and a second size recording material having a width larger than the first size recording material outside the first size passing area are provided on the outer peripheral surface of the rotating body. A first size non-passing region through which is passed,
The fixing device according to claim 2, wherein the spray mechanism sprays the coolant toward the first size non-passing region. The spray mechanism is
A spray opening opened toward the first size non-passing region;
The fixing device according to claim 6, further comprising: a shutter that changes an opening width of the spray port in a width direction of the recording material.   The spray mechanism is disposed on the downstream side of the nip portion in the conveyance direction of the recording material, and is positioned on the opposite side of the rotating body via the conveyance path of the recording material. Item 8. The fixing device according to any one of Items 2 to 7.   The fixing device according to claim 1, wherein after the contact of the coolant with the rotating body is stopped, the rotating body is rotated for a predetermined time.   The fixing device according to claim 1, wherein the cooling unit is provided in the vicinity of the rotating body with an interval from the rotating body.   The fixing device according to claim 1, wherein the rotating body is a pressure roller.   The fixing device according to claim 1, wherein the rotating body is a fixing roller.   An image forming apparatus comprising the fixing device according to claim 1.

Images