JP2014059443A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of dramatically improving cooling efficiency of a rotating body even when an image forming apparatus is configured to operate at a high speed while the contact area between cooling means and the rotating body is sufficiently ensured without imposing a large load on the rotating body.SOLUTION: A fixing device 16 of the present invention includes: a rotating body 18 that forms a nip part 22 for heating a toner image on a recording material; and cooling means 20 for cooling the rotating body 18. The cooling means 20 brings powder into contact with the rotating body 18 to cool the rotating body 18.

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, a rotating body (for example, a fixing roller) having a heater therein and another rotating body (for example, a pressure roller) are arranged in pressure contact with each other. A nip portion is formed. Then, the toner image on 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 that uses 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. In the region where the first size recording material 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 the second size recording material having a width larger than that of the first size recording material passes outside the first size passing region (hereinafter referred to as “first size non-passing region”), heat is applied. Will not be taken away. 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 area is excessively raised, the high temperature offset that causes the toner on the recording material to adhere to the rotating member and stain the image. Such a problem 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, in this method, 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 is increased by the contact between the cooling roller and the rotating body, there is a problem that the surface of the rotating body is rubbed and the deterioration of the rotating body is promoted.

  Moreover, in order to improve cooling efficiency using the method of patent document 1, it is necessary to earn the contact area of a cooling roller and a rotary body. However, in particular, when the rotating body is a rigid body, the contact between the cooling roller and the rotating body is almost a line contact, so it is difficult to increase the contact area and increase the cooling efficiency. Even if the rotating body has an elastic layer, it is necessary to press the rotating body with an appropriate load in order to secure a sufficient contact area, and accordingly the deterioration of the rotating body is accelerated. . For this reason, there is a problem that it is difficult to cope with high speed and high durability of the image forming apparatus.

  The present invention has been made in view of the above-described problems of the prior art, and even when the image forming apparatus is speeded up by sufficiently securing the contact area between the cooling unit and the rotating body without applying a large load to the rotating body. The object is to dramatically improve the cooling efficiency of the rotating body.

  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 powder into contact therewith.

  By comprising in this way, when powder contacts a rotary body, it becomes possible to absorb the heat of a rotary body and to reduce the temperature of a rotary body efficiently. In addition, since the contact area between the cooling means and the rotating body can be sufficiently secured without applying a large load to the rotating body, the cooling efficiency of the rotating body can be dramatically improved even when the image forming apparatus is speeded up. Can be improved.

  The cooling means may include a powder container that stores the powder, and a transport member that transports the powder from the powder container to the rotating body.

  By comprising in this way, it becomes possible to make a powder contact a rotary body with a simple structure, and to cool a rotary body.

  The powder may include a magnetic material, and at least a part of the transport member may be made of a magnetic material.

  By comprising in this way, the powder hold | maintained by the magnetic force on the surface of the conveyance member becomes a magnetic brush, and will lightly contact a rotary body. Therefore, it becomes possible to cool the rotating body without applying a large load to the rotating body.

  A resin layer may be provided on the surface of the powder.

  By comprising in this way, when a powder contacts the surface of a rotary body, it can prevent that a powder damages the surface of a rotary body.

  The transport member is a transport roller including a rotatable sleeve made of a non-magnetic material and a magnet as the magnetic body contained in the sleeve, and the magnet has a magnetic pole of the same polarity. A powder peeling part to be sandwiched may be provided.

  By comprising in this way, the powder conveyed from the powder container to the rotating body by the conveying roller can be peeled off from the conveying roller after being brought into contact with the rotating body, and collected again in the powder container. Therefore, it is possible to always prevent only the same powder from coming into contact with the rotating body, and accordingly, the cooling efficiency of the rotating body can be increased.

  The powder container is provided with a transport port for the powder, and the magnet is opposed to the first position for retracting the powder stripping portion from the transport port and the powder stripping portion facing the transport port. The second position to be rotated may be provided so as to be rotatable.

  With this configuration, it is possible to easily switch whether or not to cool the rotating body simply by rotating the magnet.

  The cooling means may include a powder circulation member provided in the powder container for circulating the powder.

  By configuring in this way, it becomes possible to increase the circulation efficiency of the powder in the powder container, and along with this, the soaking effect of the rotating body can be expected.

  At least a part of the powder circulation member may be made of a hollow high heat conductive material, and the hollow portion may be connected to the outside air.

  With this configuration, the powder that has absorbed the heat of the rotating body is circulated by the powder circulation member, and at the same time, the temperature of the powder can be lowered by heat transfer from the powder circulation member. Along with this, an improvement in the cooling efficiency of the rotating body can be expected.

  The cooling means may include air blowing means for blowing outside air into the hollow portion.

  By comprising in this way, a powder circulation member can be cooled efficiently and the cooling effect of the powder by the heat transfer from a powder circulation member can be improved further.

  At least a part of the powder container may be made of a high heat conductive material, and a heat radiator may be in contact with a portion made of the high heat conductive material.

  By comprising in this way, a powder container can be cooled efficiently and the temperature of the powder in a powder container can also be lowered | hung by the heat transfer from a powder container in connection with this. Therefore, improvement of the cooling efficiency of the rotating body by powder can be expected.

  The cooling unit may include a blowing unit that blows outside air to the radiator.

  By comprising in this way, a powder container can be cooled efficiently and the cooling effect of the powder by the heat transfer from a powder container can be heightened further.

  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 powder passes, and the powder may be brought into contact with the first size non-passing region.

  By comprising in this way, only the 1st size non-passing area | region which needs cooling can be cooled efficiently, and it can prevent that the temperature of a 1st size passing area | region falls unnecessarily. Therefore, it is possible to prevent unnecessary power consumption.

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

  According to the present invention, a sufficient contact area between the cooling means and the rotating body is ensured without applying a large load to the rotating body, and the cooling efficiency of the rotating body is dramatically improved even when the image forming apparatus is speeded up. It becomes possible.

1 is a schematic diagram illustrating an outline of a printer according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a state where a magnet is in a first position in the fixing device of the printer according to the first embodiment of the present invention. FIG. 3 is a plan view showing a cooling unit in the fixing device of the printer according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a state where the magnet is in a second position in the fixing device of the printer according to the first embodiment of the present invention. 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. FIG. 6 is a plan view illustrating a cooling unit in a fixing device of a printer according to a second embodiment of the present invention.

<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 portion of the printer main body 2 from below to above. That is, the printer 1 of this embodiment is a vertical conveyance. A paper feed 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 transport path 13, a reverse path 17 for duplex 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 conveyance 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 transport 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. Note that an arrow Fr in FIG. 3 indicates the front side (front side) of the fixing device 16.

  As shown in FIG. 2, the fixing device 16 includes a heating roller 18 as a rotating body, a pressure roller 19 disposed on the right side of the heating roller 18, and a cooling unit disposed on the lower left side of the heating roller 18. 20. Hereinafter, these will be described in order.

  First, the heating roller 18 will be described. The heating roller 18 has a long shape in the front-rear direction (in the drawing, the depth direction in the drawing). That is, in this embodiment, the front-rear direction is the longitudinal direction of the heating roller 18. The heating roller 18 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 that covers the elastic layer. And a release layer.

  The heating roller 18 is rotatably accommodated in a box-shaped fixing frame (not shown). A heater 21 configured by, for example, a halogen heater or a ceramic heater is accommodated in the internal space of the heating roller 18.

  Next, the pressure roller 19 will be described. The pressure roller 19 has a shape that is long in the front-rear direction, similar to the heating roller 18. The pressure roller 19 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 such as PFA covering the elastic layer. And a release layer made of resin.

  The pressure roller 19 is rotatably accommodated in a fixing frame (not shown) together with the heating roller 18. The pressure roller 19 is in pressure contact with the heating roller 18 by an urging force of an urging means (not shown), and a nip portion 22 is formed between the heating roller 18 and the pressure roller 19. Then, the sheet on which the toner image is formed passes through the nip portion 22 so that the toner image on the sheet is heated and pressurized and fixed on the sheet. The pressure roller 19 is configured to be driven to rotate in the opposite direction to the heating roller 18 as the heating roller 18 rotates.

  Next, the cooling means 20 will be described. As shown in FIG. 2 and FIG. 3, the cooling means 20 includes a box-shaped powder container 23 having an upper surface opened, and a first powder circulation member accommodated in the left side portion of the powder container 23. A mixer 24, a second mixer 25 as a powder circulation member housed in the right side portion of the powder container 23, a transport roller 26 as a transport member disposed above the second mixer 25, and the powder container 23 And a pair of front and rear fans 27 as air blowing means disposed on the left side of the.

  The powder container 23 has a long shape in the front-rear direction (see FIG. 3). The powder container 23 contains a powder 28 (see FIG. 2). The powder 28 is composed of magnetic powder and a resin layer that covers the magnetic powder. The magnetic powder is made of, for example, a magnetic material such as iron or ferrite. The resin layer is provided on the surface of the powder 28. The resin layer is made of, for example, a fluorine-based resin such as PVDF (polyvinylidene fluoride) or PTFE (polytetrafluoroethylene).

  The powder container 23 is provided with a transport port 31 for the powder 28 between the upper end portion of the right side wall 30 and the transport roller 26. A pair of front and rear partition walls 32 is provided at the center in the left-right direction of the powder container 23, and the internal space of the powder container 23 is partitioned by the partition walls 32 on the left and right. The leading end side (upper end side) of each partition wall 32 is inclined leftward (in the direction away from the heating roller 18) toward the upper side. Between the front end wall 33 of the powder container 23 and the front partition wall 32, between the front partition wall 32 and the rear partition wall 32, and between the rear partition wall 32 and the rear end wall 34 of the powder container 23. A flow interval 35 of the powder 28 is formed between them.

  A heat radiator 37 is fixed to the outer surface (left surface) of the left side wall 36 (the wall on the first mixer 24 side) of the powder container 23. The heat radiating body 37 includes a substrate portion 38 that contacts the outer surface of the left side wall 36 of the powder container 23, and a plurality of fins 40 that protrude leftward from the substrate portion 38. Each fin 40 is provided at intervals in the vertical direction. The portion of the powder container 23 that is in contact with the substrate portion 38 of the heat radiating body 37 is made of a high thermal conductive material such as aluminum or stainless steel (SUS). The other part of the powder container 23 is made of, for example, resin.

  The first mixer 24 is provided in a rotatable state in the space on the left side of the partition wall 32 in the powder container 23. The first mixer 24 includes a rotation shaft 41 extending in the front-rear direction and a spiral fin 42 provided around the rotation shaft 41. Both front and rear ends of the rotating shaft 41 are pivotally supported by the front end wall 33 and the rear end wall 34 of the powder container 23, respectively. The spiral fin 42 is divided into two at the center in the longitudinal direction (center in the front-rear direction), and is provided at a position in the front-rear direction corresponding to each partition wall 32 of the powder container 23.

  The second mixer 25 is provided in a rotatable state in the space on the right side of the partition wall 32 in the powder container 23. Since the configuration of the second mixer 25 is the same as the configuration of the first mixer 24, description thereof is omitted.

  The conveyance roller 26 includes a cylindrical sleeve 43, a magnet (magnetic body) 44 included in the sleeve 43, and a support shaft 45 provided inside the magnet 44.

  The sleeve 43 is made of a nonmagnetic material such as aluminum or nonmagnetic stainless steel (SUS). The sleeve 43 is provided over the entire area of the heating roller 18 in the longitudinal direction. The sleeve 43 is attached to the outer periphery of the magnet 44 in a rotatable state.

  The magnet 44 is provided over the entire area of the heating roller 18 in the longitudinal direction. The magnet 44 is provided such that three N poles and two S poles are alternately arranged in the circumferential direction. The magnet 44 is provided with a powder peeling portion 46 sandwiched between N poles (magnetic poles of the same polarity) at both ends in the circumferential direction. The magnet 44 opposes the powder peeling unit 46 to the first position (see FIG. 2) where the powder peeling unit 46 is retracted downward from the conveyance port 31 of the powder container 23, and the conveyance port 31 of the powder container 23. It is possible to rotate between the second position (see FIG. 4). Both front and rear ends of the support shaft 45 are respectively supported by the front end wall 33 and the rear end wall 34 of the powder container 23.

  The pair of front and rear fans 27 are provided so as to face the heat radiating body 37 of the powder container 23 so that the outside air can be blown to the heat radiating body 37. Each fan 27 is provided at a position in the front-rear direction corresponding to a pair of front and rear partition walls 32 provided in the powder container 23.

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

  The printer 1 is provided with a control unit 47. The control unit 47 is connected to a storage unit 48 configured by a storage device such as a ROM or a RAM. The control unit 47 controls each unit of the printer 1 based on a control program and control data stored in the storage unit 48. It is comprised so that control may be performed.

  The controller 47 is connected to a temperature sensor 50 provided in the powder container 23, and a temperature detection signal is output from the temperature sensor 50 to the controller 47. For example, the temperature sensor 50 is disposed around the heating roller 18.

  The control unit 47 is connected to the heater 21 in the heating roller 18, and is configured so that the heater 21 is energized to generate heat based on a signal from the control unit 47 and the heating roller 18 is heated.

  The control unit 47 is connected to first driving means 52 configured by a motor or the like, and the first driving means 52 is connected to the heating roller 18. And the 1st drive means 52 is comprised so that the heating roller 18 may be rotated based on the drive command signal from the control part 47. FIG.

  The control unit 47 is connected to second drive means 53 configured by a motor or the like, and the second drive means 53 is connected to the first mixer 24, the second mixer 25, and the sleeve 43 of the transport roller 26. . The second drive unit 53 is configured to rotate the first mixer 24, the second mixer 25, and the sleeve 43 of the transport roller 26 based on a drive command signal from the control unit 47.

  The control unit 47 is connected to third driving means 54 configured by a motor or the like, and the third driving means 54 is connected to the magnet 44 of the transport roller 26. And based on the drive command signal from the control part 47, the 3rd drive means 54 is comprised so that the magnet 44 may be rotated between a 1st position and a 2nd position.

  In the configuration as described above, for example, when a toner image is fixed on a first size paper, the magnet 44 is disposed at the first position as shown in FIG. In this state, as indicated by an arrow a in FIG. 2, the sleeve 43 of the transport roller 26 is rotated counterclockwise when viewed from the front. As the sleeve 43 rotates, the powder 28 is pumped up by the magnetic force acting between the N pole on the lower right of the magnet 44 and the powder 28. The pumped powder 28 is conveyed from the powder container 23 to the heating roller 18 by the sleeve 43 of the conveying roller 26 and contacts the heating roller 18. By this contact, the powder 28 absorbs the heat of the heating roller 18. The powder 28 that has absorbed the heat of the heating roller 18 is further conveyed by the sleeve 43, passes through the lower left N pole of the magnet 44, and moves to the powder peeling unit 46. Since the powder peeling portion 46 has a repulsive magnetic field sandwiched between the N poles, the powder 28 peels from the sleeve 43 at the powder peeling portion 46.

  Further, in conjunction with the rotation of the sleeve 43, the first and second mixers 24 and 25 are rotated. Along with this, the first and second mixers 24 and 25 convey the powder 28 separated from the sleeve 43 in the axial direction (front-rear direction) of the rotary shaft 41 while stirring. Along with this, the powder 28 circulates in the powder container 23 as shown by a one-dot chain line arrow in FIG. The powder 28 circulated in the powder container 23 is pumped up again and conveyed from the powder container 23 to the heating roller 18 by the sleeve 43 of the conveying roller 26.

  Further, when the toner image is fixed on the first size paper as described above, the fan 27 is operated. As a result, as indicated by white arrows in FIGS. 2 and 3, the outside air drawn into the printer 1 is blown to the radiator 37 and the powder container 23 is cooled. Along with this, the powder 28 accommodated in the powder container 23 is also cooled.

  In order to increase the cooling efficiency of the heating roller 18, the rotational speed of the sleeve 43 and the first and second mixers 24, 25 is increased by the second driving means 53. Conversely, when it is desired to reduce the cooling efficiency of the heating roller 18, the rotational speed of the sleeve 43 and the first and second mixers 24, 25 is decreased by the second driving means 53. Thus, the cooling efficiency of the heating roller 18 can be changed by changing the rotational speed of the sleeve 43 and the first and second mixers 24 and 25.

  On the other hand, when the heating roller 18 does not need to be cooled, for example, when a toner image is fixed on a second size sheet or during standby, the magnet 44 is moved to the first position as shown in FIG. To the second position in a counterclockwise direction. Along with this, the powder peeling portion 46 of the magnet 44 faces the transport port 31 of the powder container 23. When the powder peeling part 46 faces the transport port 31 in this way, the powder peeling part 46 has a repulsive magnetic field sandwiched between the N poles, so that the pumping of the powder 28 by the sleeve 43 of the transport roller 26 is stopped. To do. In the present embodiment, when the heating roller 18 does not need to be cooled, the first and second mixers 24 and 25 and the fan 27 are stopped.

  When the toner image is fixed on the second size paper and then the toner image is fixed again on the first size paper, such as when the heating roller 18 needs to be cooled again, The magnet 44 may be rotated clockwise from the position 2 to the first position.

  In the present embodiment, the powder 28 is brought into contact with the heating roller 18 as described above. By adopting such a configuration, it is possible to absorb the heat of the heating roller 18 when the powder 28 comes into contact with the heating roller 18 and to efficiently lower the temperature of the heating roller 18. In addition, since it is possible to ensure a sufficient contact area between the cooling means 20 and the heating roller 18 without applying a large load to the heating roller 18, the cooling efficiency of the heating roller 18 can be improved even when the printer 1 is speeded up. Can be dramatically improved.

  The cooling unit 20 includes a powder container 23 that stores the powder 28, and a transport roller 26 that transports the powder 28 from the powder container 23 to the heating roller 18. Therefore, the powder 28 can be brought into contact with the heating roller 18 with a simple configuration, and the heating roller 18 can be cooled.

  Further, since the powder 28 includes a magnetic material (magnetic powder) and a part of the transport roller 26 is configured by the magnet 44, the powder 28 held by the magnetic force on the surface of the sleeve 43 becomes a magnetic brush. Thus, the heating roller 18 is lightly contacted. Therefore, it is possible to cool the heating roller 18 without applying a large load to the heating roller 18.

  Further, since the resin layer is provided on the surface of the powder 28, it is possible to prevent the powder 28 from damaging the surface of the heating roller 18 when the powder 28 contacts the surface of the heating roller 18. In the present embodiment, the resin layer is formed of a resin (fluorine resin) having good toner releasability. Therefore, even when the toner adheres to the surface of the heating roller 18, The toner becomes difficult to adhere.

  Further, since the transport roller 26 includes a rotatable sleeve 43 made of a nonmagnetic material and a magnet 44 included in the sleeve 43, the heating roller 18 is moved from the powder container 23 by the rotation of the sleeve 43. The powder 28 can be easily conveyed to the heat roller and brought into contact with the heating roller 18.

  Moreover, since the powder peeling part 46 is provided in the magnet 44 of the conveyance roller 26, the powder 28 conveyed from the powder container 23 to the heating roller 18 by the conveyance roller 26 was brought into contact with the heating roller 18. Later, it can be peeled off from the sleeve 43 of the transport roller 26 and collected again in the powder container 23. Therefore, it is possible to always prevent only the same powder 28 from coming into contact with the heating roller 18, and accordingly, the cooling efficiency of the heating roller 18 can be increased.

  The magnet 44 is rotatably provided between a first position where the powder peeling unit 46 is retracted from the conveyance port 31 and a second position where the powder peeling unit 46 is opposed to the conveyance port 31. ing. If the magnet 44 is rotated to the first position, the heating roller 18 can be cooled by the powder 28. On the other hand, if the magnet 44 is rotated to the second position, the pumping of the powder 28 can be stopped. In this way, it is possible to easily switch whether or not the heating roller 18 is cooled only by rotating the magnet 44.

  In addition, since the cooling means 20 includes the first and second mixers 24 and 25, the circulation efficiency of the powder 28 in the powder container 23 can be increased. A heat effect can be expected. Further, in the present embodiment, in particular, the powder 28 that has been heated to contact with the heating roller 18 in the first size non-passing region is moved to the first size passing region, and then again transferred to the heating roller 18 in the first size passing region. It can be contacted. Therefore, the amount of heat of the powder 28 that has absorbed heat in the first size non-passing region can be supplied to the first size passing region, and the heating roller 18 can be more evenly heated.

  Further, a part of the powder container 23 is made of a high heat conductive material, and a radiator 37 is in contact with the portion made of the high heat conductive material. Therefore, the powder container 23 can be efficiently cooled, and along with this, the temperature of the powder 28 in the powder container 23 can be lowered by the heat transfer from the powder container 23, and the powder The improvement of the cooling efficiency of the heating roller 18 by 28 can be expected. Further, since the cooling means 20 is provided with a fan 27 that blows outside air to the heat radiating body 37, the powder container 23 is efficiently cooled, and the cooling effect of the powder 28 by heat transfer from the powder container 23 is achieved. Can be further enhanced.

  In the present embodiment, the case where the transport member is configured by the transport roller 26 has been described. However, in another different embodiment, the transport member may be configured by a transport belt, a transport plate, or the like. That is, the shape of the conveying member is not limited to the roller.

  In the present embodiment, the case where the powder 28 is transported from the powder container 23 to the heating roller 18 using the transport roller 26 has been described. However, in another different embodiment, a rotating body such as the heating roller 18 is used as the powder. You may insert directly in the container 23. FIG.

  Although the case where the heating roller 18 is cooled by the cooling unit 20 has been described in the present embodiment, the pressure roller 19 may be cooled by the cooling unit 20 in other different embodiments. When the belt type fixing device 16 is used, the heating belt may be cooled by the cooling means 20.

  In the present embodiment, a case has been described in which only a part of the powder container 23 is configured by a high thermal conductive material. However, in another different embodiment, the entire powder container 23 may be configured by a high thermal conductive material.

  In the present embodiment, when the heating roller 18 does not need to be cooled (for example, when a toner image is fixed on a second size sheet or during standby), the first and second mixers 24 and 25 and the fan 27 are connected. It was stopped. On the other hand, in other different embodiments, even when the heating roller 18 does not need to be cooled, the driving of the first and second mixers 24 and 25 and the fan 27 is controlled based on the detection signal from the temperature sensor 50. Also good.

  In this embodiment, the case where the resin layer of the powder 28 is made of a fluororesin has been described. However, in another different embodiment, for example, the resin layer of the powder 28 is made of another resin such as a polyimide resin. May be.

  In the present embodiment, the case where the heater 21 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 16 according to a second embodiment of the present invention will be described with reference to FIGS. Since the configuration other than the cooling unit 20 is the same as that of the first embodiment, the description thereof is omitted. An arrow Fr in FIG. 7 indicates the front side (front side) of the fixing device 16. L1 in FIG. 7 indicates a first size passing area, and L2 in FIG. 7 indicates a first size non-passing area.

  As shown in FIG. 6 and FIG. 7, the cooling means 20 includes a box-shaped powder container 23 whose upper surface is opened, and a first powder circulation member accommodated in the left side portion of the powder container 23. A mixer 24, a second mixer 25 as a powder circulation member accommodated in the right side portion of the powder container 23, a transport roller 26 disposed above the second mixer 25, and disposed in front of the powder container 23 And a fan 27 as an air blowing means.

  A heat radiating body 37 (see the first embodiment) is not fixed to the powder container 23. In the powder container 23, each partition wall 32 is provided only in the first size non-passing region. The front end wall 33 and the rear end wall 34 of the powder container 23 are each provided with a pair of left and right openings 61. Since the other configuration of the powder container 23 is the same as that of the first embodiment, the description thereof is omitted.

  The first mixer 24 is accommodated in a rotatable state in a space on the left side of the partition wall 32 in the powder container 23. The first mixer 24 includes a rotation shaft 41 extending in the front-rear direction and a spiral fin 42 provided around the rotation shaft 41. Both front and rear ends of the rotating shaft 41 are pivotally supported by the front end wall 33 and the rear end wall 34 of the powder container 23, respectively. The rotating shaft 41 is formed of a hollow high heat conductive material such as aluminum or stainless steel (SUS). The rotary shaft 41 is provided with a hollow portion 60 from the front end portion to the rear end portion along the axial direction (front-rear direction). Both front and rear end portions of the hollow portion 60 are connected to the outside air through openings 61 provided in the front end wall 33 and the rear end wall 34 of the powder container 23.

  The spiral fin 42 is divided into two at the longitudinal center (front-rear direction center). The spiral fins 42 are provided at the front-rear direction positions corresponding to the partition walls 32 of the powder container 23. In other words, the spiral fins 42 are provided only in the first size non-passing region, like the partition walls 32. The spiral fins 42 may be formed of a high heat conductive material similarly to the rotating shaft 41, or may be formed of a material other than the high heat conductive material.

  The second mixer 25 is accommodated in a rotatable state in the space on the right side of the partition wall 32 in the powder container 23. Since the configuration of the second mixer 25 is the same as the configuration of the first mixer 24, description thereof is omitted.

  The transport roller 26 includes a cylindrical sleeve 43, a magnet 44 included in the sleeve 43, and a support shaft 45 provided inside the magnet 44. The sleeve 43 and the magnet 44 are divided into two at the longitudinal center (front-rear direction center). The sleeve 43 and the magnet 44 are provided at positions in the front-rear direction corresponding to the partition walls 32 of the powder container 23. That is, the sleeve 43 and the magnet 44 are provided only in the first size non-passing region, as with each partition wall 32. Since other configurations of the sleeve 43 and the magnet 44 and the configuration of the support shaft 45 are the same as those in the first embodiment, the description thereof is omitted.

  The fan 27 is provided so as to oppose the front end wall 33 of the powder container 23, and is formed in the hollow portion 60 of the first and second mixers 24 and 25 through the opening 61 provided in the front end wall 33. It is designed to blow outside air.

  In the configuration as described above, for example, when fixing a first size sheet, the sleeve 43 of the transport roller 26 is rotated counterclockwise in front view as shown by an arrow b in FIG. . When the sleeve 43 is rotated in this manner, the powder 28 is conveyed from the powder container 23 to the heating roller 18 by the sleeve 43 and contacts the heating roller 18 as in the first embodiment. The powder 28 that has absorbed the heat of the heating roller 18 by this contact passes through the N pole on the lower left of the magnet 44 and moves to the powder peeling portion 46, and is then peeled off from the sleeve 43 at the powder peeling portion 46.

  Further, the first mixer 24 and the second mixer 25 are rotated in conjunction with the rotation of the sleeve 43. Along with this, the powder 28 accommodated in the powder container 23 circulates in the powder container 23 as shown by a one-dot chain line arrow in FIG.

  Further, when the toner image is fixed on the first size paper as described above, the fan 27 is operated. As a result, as indicated by white arrows in FIGS. 6 and 7, the outside air drawn into the printer 1 is blown into the hollow portions 60 of the first and second mixers 24 and 25, and each of the first and second The mixers 24 and 25 are cooled. Along with this, the powder 28 accommodated in the powder container 23 is also cooled.

  In the present embodiment, as described above, the rotation shafts 41 of the first and second mixers 24 and 25 are made of a hollow high heat conductive material, and the hollow portion 60 of the rotation shaft 41 is connected to the outside air. Therefore, the powder 28 that has absorbed the heat of the heating roller 18 is circulated by the first and second mixers 24 and 25, and at the same time, the temperature of the powder 28 is lowered by the heat transfer from the first and second mixers 24 and 25. It becomes possible. Along with this, an improvement in the cooling efficiency of the heating roller 18 can be expected. In addition, since the cooling unit 20 is provided with the fan 27 that blows outside air to the hollow portion 60, the first and second mixers 24 and 25 can be efficiently cooled, and the first and second mixers 24, The cooling effect of the powder 28 due to heat transfer from 25 can be further enhanced. Further, the powder 28 can be sufficiently cooled without fixing the heat radiating body 37 (see the first embodiment) to the powder container 23, and the fixing device 16 can be downsized. .

  Further, since the spiral fins 42 of the first and second mixers 24 and 25 and the sleeve 43 and the magnet 44 of the transport roller 26 are arranged only in the first size non-passing region, the first size that needs to be cooled. Only the non-passing region can be efficiently cooled. Therefore, it is possible to prevent the temperature of the first size passage region from being unnecessarily lowered, and it is possible to prevent excessive power consumption.

  In this embodiment, the case where the cooling air passes through both the first and second mixers 24 and 25 has been described. However, in another different embodiment, only one of the first and second mixers 24 and 25 is used. You may comprise so that cooling air may pass.

1 Printer (image forming device)
16 Fixing device 18 Heating roller (rotating body)
20 Cooling means 22 Nip part 23 Powder container 24 First mixer (powder circulation member)
25 Second mixer (powder circulation member)
26 Conveying roller (conveying member)
27 Cooling fan (air blowing means)
28 Powder 31 Transport Port 37 Heat Dissipator 43 Sleeve 44 Magnet 46 Powder Stripping Part 60 Hollow Part

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 powder into contact with the rotating body. The cooling means is
A powder container containing the powder;
The fixing device according to claim 1, further comprising: a conveying member that conveys the powder from the powder container to the rotating body. The powder includes a magnetic material,
The fixing device according to claim 2, wherein at least a part of the conveying member is made of a magnetic material.   The fixing device according to claim 3, wherein a resin layer is provided on a surface of the powder. The conveying member is
A rotatable sleeve made of a non-magnetic material;
A transfer roller provided with a magnet as the magnetic body included in the sleeve,
The fixing device according to claim 3, wherein the magnet is provided with a powder peeling portion sandwiched between magnetic poles having the same polarity. The powder container is provided with a transport port for the powder,
The magnet is rotatably provided between a first position where the powder peeling unit is retracted from the conveyance port and a second position where the powder peeling unit is opposed to the conveyance port. The fixing device according to claim 5.   The fixing device according to claim 2, wherein the cooling unit includes a powder circulation member that is provided in the powder container and circulates the powder.   The fixing device according to claim 7, wherein at least a part of the powder circulation member is made of a hollow high thermal conductive material, and the hollow portion is connected to the outside air.   The fixing device according to claim 8, wherein the cooling unit includes a blowing unit that blows outside air into the hollow portion.   10. The powder container according to claim 2, wherein at least a part of the powder container is made of a high heat conductive material, and a heat radiator is in contact with a portion made of the high heat conductive material. The fixing device described.   The fixing device according to claim 10, wherein the cooling unit includes a blowing unit that blows outside air to the radiator. 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 1, wherein the powder is brought into contact with the first size non-passing region.   An image forming apparatus comprising the fixing device according to claim 1.

Images