JP2018091927A - Driving device, fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device that is applied to a fixing device, the driving device capable of smoothly transmitting a rotational driving force even when using a transmission gear formed of a water-absorbing resin while preventing the occurrence of backlash of the transmission gear.SOLUTION: A driving device 100 transmits a rotational driving force output from a motor to a magnetic flux shielding member included in a fixing device. The driving device 100 includes a housing, a large-diameter gear 107, and a drying member 108. The large-diameter gear 107 is provided inside the housing, formed of a water-absorbing resin, and transmits the rotational driving force to the magnetic flux shielding member. The drying member 108 dries air inside the housing.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a driving device used in a fixing device including a heating device such as an induction heating device that heats a fixing member, and more particularly, to a driving device having a transmission gear made of a water-absorbing resin.

  The electrophotographic image forming apparatus includes a fixing device that fixes the toner image transferred to the printing paper on the printing paper. As the fixing device, one using a fixing belt made of a flexible cylindrical film member is known (see Patent Document 1). In this type of fixing device, the fixing belt is rotatably supported, and the fixing belt is rotated by applying a rotational driving force thereto. Then, the fixing belt is heated by an induction heating type heating device arranged to face the outer peripheral surface of the fixing belt.

  Further, as a fixing device including an induction heating type heating device, a fixing device including a magnetic flux shielding member that can move according to the paper size is known (see Patent Document 2). In this fixing device, a magnetic flux shielding member is disposed at a predetermined position when fixing on a small size sheet, and the magnetic flux acting on the non-sheet passing area of the fixing member is blocked to suppress the heat generation in the non-sheet passing area of the fixing member. To do.

  Further, the conventional fixing device is provided with a driving device for operating a fixing member, a magnetic flux shielding member, and the like. The driving device includes a gear for changing the rotational driving force from a driving source such as a motor to a predetermined rotational speed, a gear for changing the transmission path of the rotational driving force, and the like.

JP 2015-200122 A JP 2014-109690 A

  By the way, conventionally, the gear of the driving device may be made of a water-absorbing resin such as nylon. The water absorbent resin has a property of expanding when it absorbs water. Therefore, when the gear is made of water-absorbing resin, it is necessary to design the inner diameter of the gear or the rotation shaft of the gear to a size that takes into account expansion after water absorption. In particular, in the fixing device, moisture contained in the printing paper evaporates due to heating during fixing, and the water vapor is absorbed by a gear inside the driving device, so that it is highly necessary to consider the expansion. However, when the inner diameter of the gear is increased in consideration of the expansion or the diameter of the rotation shaft of the gear is decreased, the bearing portion is loosened, and the play causes poor transmission such as tooth skipping or abnormal noise. There is a fear.

  An object of the present invention is to allow a rotational drive force to be smoothly transmitted without providing play in a transmission gear even when a transmission gear made of water-absorbing resin is used in a drive device applied to a fixing device. A driving device, a fixing device including the driving device, and an image forming apparatus including the fixing device are provided.

  A driving device according to one aspect of the present invention is a driving device that transmits a rotational driving force output from a driving source to a driving member included in a fixing device. The drive device includes a housing, a transmission gear, and a drying unit. The transmission gear is provided inside the housing and is made of a water absorbent resin, and transmits the rotational driving force to the driving member. The drying unit dries air inside the casing.

  A fixing device according to another aspect of the present invention includes a driving device, a driving member, a fixing member, and a heating device. The driving device supplies a rotational driving force output from a driving source. The driving member is driven by receiving the rotational driving force supplied from the driving device. The fixing member is heated during a fixing operation. The heating device heats the fixing member. The drive device includes a housing, a transmission gear, and a drying unit. The transmission gear is provided inside the housing and is made of a water absorbent resin, and transmits the rotational driving force to the driving member. The drying unit dries air inside the casing.

  An image forming apparatus according to another aspect of the present invention includes the fixing device, and forms an image on a printing paper using toner that can be fixed by the fixing device.

  According to the present invention, even when a transmission gear made of water-absorbing resin is used in a driving device applied to a fixing device, it is possible to smoothly transmit a rotational driving force without providing play in the transmission gear. is there.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the fixing device according to the embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration of a magnetic flux shielding member included in the fixing device. FIG. 4 is a schematic diagram illustrating a configuration of a blower and a heating device provided in the fixing device. FIG. 5 is a perspective view showing the configuration of the drive device according to the embodiment of the present invention. FIG. 6 is a perspective view showing the configuration of the drive device according to the embodiment of the present invention. FIG. 7 is a perspective view showing an internal configuration of the driving device.

  Embodiments of the present invention will be described below with reference to the drawings as appropriate. In addition, the following embodiment is only an example which actualized this invention, and does not limit the technical scope of this invention.

[Image forming apparatus 10]
FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus 10 (an example of the image forming apparatus of the present invention) according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 is a so-called tandem color image forming apparatus, and includes a plurality of image forming units 1 to 4, an intermediate transfer belt 5, a resist detection sensor 6, and a driving roller 7A. A driven roller 7B, a secondary transfer device 15, a fixing device 16 (an example of the fixing device of the present invention), a control unit 8, a paper feed tray 17, and a paper discharge tray 18. A specific example of the image forming apparatus 10 according to the embodiment of the present invention is, for example, a printer, a copier, a facsimile machine, or a multifunction machine having these functions. Further, the image forming apparatus is not limited to a color image forming apparatus, and may be a monochrome image forming apparatus.

  The image forming units 1 to 4 form toner images of different colors on the plurality of photosensitive drums 11 to 14 arranged in parallel, and sequentially superimpose the toner images on the running (moving) intermediate transfer belt 5. And an electrophotographic image forming unit for transferring the image. In the example shown in FIG. 1, in order from the downstream side in the moving direction (arrow 19 direction) of the intermediate transfer belt 5, an image forming unit 1 for black, an image forming unit 2 for yellow, an image forming unit 3 for cyan, The magenta image forming units 4 are arranged in a line in that order.

  Each of the image forming units 1 to 4 includes photosensitive drums 11 to 14 that carry toner images, charging devices 21 to 24 that charge the surfaces of the photosensitive drums 11 to 14, and surfaces of the charged photosensitive drums 11 to 14. Exposure devices 31 to 34 for forming an electrostatic latent image by exposing light and scanning the light, developing devices 41 to 44 for developing the electrostatic latent images on the photosensitive drums 11 to 14 with toner, and the photosensitive drum 11 ˜14 are provided with primary transfer devices 51 to 54 for transferring the toner images on the intermediate transfer belt 5 to the intermediate transfer belt 5. Although not shown in FIG. 1, each of the image forming units 1 to 4 also includes a cleaning device that removes the residual toner images on the photosensitive drums 11 to 14.

  The intermediate transfer belt 5 is an endless belt made of a material such as rubber or urethane. The intermediate transfer belt 5 is supported by a driving roller 7A and a driven roller 7B so as to be rotationally driven. The driving roller 7A is disposed at a position close to the fixing device 16 (right side in FIG. 1), and the driven roller 7B is disposed at a position away from the fixing device 16 (left side in FIG. 1). The surface of the drive roller 7A is formed of a material such as rubber or urethane in order to increase the frictional force with the intermediate transfer belt 5. By being supported by the driving roller 7 </ b> A and the driven roller 7 </ b> B, the intermediate transfer belt 5 can move while the surface thereof is in contact with the surfaces of the photosensitive drums 11 to 14. Then, when the surface of the intermediate transfer belt 5 passes between the photosensitive drums 11 to 14 and the primary transfer devices 51 to 54, the toner images are sequentially superimposed and transferred from the photosensitive drums 11 to 14. .

  The secondary transfer device 15 transfers the toner image transferred to the intermediate transfer belt 5 onto the printing paper conveyed from the paper feed tray 17. The printing paper on which the toner image is transferred is conveyed to the fixing device 16 by a conveyance unit (not shown).

[Fixing device 16]
As shown in FIG. 2, the fixing device 16 includes a heating roller 71, a fixing roller 72, a fixing belt 75 (an example of the fixing member of the present invention), and an induction heating device 76 (an example of the heating device of the present invention). And a temperature sensor 78 and a pressure roller 80. The fixing device 16 includes a cooling fan 90 (an example of a blower according to the present invention) provided in the vicinity of the induction heating device 76. The fixing device 16 includes a driving device 100.

  The heating roller 71 is a rotating body that generates heat by induction heating using magnetic flux from the induction heating device 76. The heating roller 71 is made of, for example, a magnetic metal such as iron or stainless steel, and a release layer made of, for example, PFA is formed on the surface thereof. The heating roller 71 has a rotation shaft 71 </ b> A at the center, and the rotation shaft 71 </ b> A is rotatably supported by the housing 16 </ b> A of the fixing device 16. Thereby, the heating roller 71 becomes rotatable.

  The fixing roller 72 is a rotating body provided at a position parallel to the heating roller 71 and spaced apart from the heating roller 71. The fixing roller 72 has a rotation shaft 72A at the center, and the rotation shaft 72A is rotatably supported by the housing 16A of the fixing device 16 or the like. As a result, the fixing roller 72 can be rotated. The fixing roller 72 is connected to a motor (not shown) that is driven and controlled by the control unit 8. When the motor is driven to rotate, the rotational driving force is transmitted to rotate in a predetermined direction. In the present embodiment, the fixing roller 72 is driven to rotate counterclockwise in FIG. The outer peripheral surface of the fixing roller 72 is covered with an elastic member such as elastic silicon or porous rubber.

  The fixing belt 75 is heated during a fixing process at the time of image formation, and is stretched around the heating roller 71 and the fixing roller 72. The fixing belt 75 is an endless belt that is rotated by being driven by rotation of the fixing roller 72. The fixing belt 75 is disposed to face the induction heating device 76. When the fixing belt 75 is stretched around the heating roller 71 or the like, heat is transmitted to the fixing belt 75 from the heating roller 71 that generates heat by induction heating using magnetic flux from the induction heating device 76. The fixing belt 75 may be a belt member made of a ferromagnetic material that is induction-heated by the induction heating device 76 in the same manner as the heating roller 71.

  The induction heating device 76 is a device that heats the heating roller 71 by an induction heating method using electromagnetic induction. The induction heating device 76 indirectly heats the fixing belt 75 by heating the heating roller 71. The induction heating device 76 is provided at a position facing the circumferential surface of the heating roller 71, and covers the circumferential surface of the heating roller 71 with a gap between the circumferential surface of the heating roller 71. The outer surface of the heating roller 71 is heated by heat generated by induction heating using magnetic flux from the induction heating device 76. Details of the induction heating device 76 will be described later.

  A temperature sensor 78 is provided around the fixing belt 75. The temperature sensor 78 detects the temperature of the central portion of the fixing belt 75 and is provided in the housing 16 </ b> A of the fixing device 16 provided below the fixing roller 72. The temperature sensor 78 is provided upstream of the fixing roller 72 in the rotation direction of the fixing belt 75 and downstream of the heating roller 71 in the rotation direction of the fixing belt 75. The temperature sensor 78 is disposed in the vicinity of the fixing belt 75.

  As shown in FIG. 1, the pressure roller 80 is disposed to face the fixing roller 72. The pressure roller 80 is pressed against the fixing roller 72 by a spring or the like. As a result, a nip portion 97 is formed between the pressure roller 80 and the fixing roller 72.

  In the fixing device 16, the printing paper is conveyed so as to pass through the nip portion 97 from the bottom to the top. A separation blade 98 is provided on the downstream side of the nip portion 97 in the paper transport direction. The separation blade 98 is a member that prevents the printing paper from sticking to the fixing belt 75. At the timing when the leading edge of the printing paper passes through the nip portion 97, the printing paper is peeled off from the fixing belt 75 by the separation blade 98.

[Induction heating device 76]
The induction heating device 76 is a device that heats the fixing belt 75 by an induction heating method using electromagnetic induction. As shown in FIG. 2, the induction heating device 76 is disposed so as to face the facing portion 75A of the fixing belt 75, and generates a magnetic flux toward the facing portion 75A, thereby generating Joule heat in the facing portion 75A. Generate and heat. In other words, the facing portion 75 </ b> A of the fixing belt 75 generates Joule heat under the influence of the magnetic field lines from the induction heating device 76 and self-heats.

  The induction heating device 76 includes a center core 81 (an example of the magnetic core of the present invention), an arch core 82, a side core 83, a bobbin 84, an induction coil 85 (an example of the induction coil of the present invention), and a magnetic flux shielding member. 86 (an example of a driving member of the present invention) and a housing 76A (an example of a casing of the present invention) that accommodates them.

  The induction coil 85 is excited to heat the heating roller 71 and generate a magnetic flux for heating the fixing belt 75. The induction coil 85 has a configuration in which coil wires are wound in an elliptical shape several times so as to be folded at both ends of the fixing belt 75 in the longitudinal direction D1 (see FIG. 4). Here, the longitudinal direction D1 is a direction perpendicular to the paper surface in FIG. 2 and coincides with the axial direction of the heating roller 71, the fixing roller 72, and the pressure roller 80. The induction coil 85 is wound so as to be long in the longitudinal direction D1 of the fixing belt 75 so that the entire region in the longitudinal direction D1 of the facing portion 75A of the fixing belt 75 can be heated uniformly.

  The arch core 82 and the bobbin 84 each extend in the longitudinal direction D1 of the fixing belt 75, and the cross-sectional shapes thereof are formed in a substantially arc shape. The bobbin 84 is disposed on the fixing belt 75 side and supports the induction coil 85. That is, the induction coil 85 is held on the bobbin 84.

  The arch core 82 is provided on the side opposite to the fixing belt 75 (left side in FIG. 2). The arch core 82 covers the bobbin 84 so as to cover the induction coil 85. The arch core 82 guides the magnetic flux generated by exciting the induction coil 85 to the fixing belt 75 side, and is made of a magnetic metal.

  The side core 83 is made of a magnetic metal and is provided at both ends of the bobbin 84. The side core 83 extends in the longitudinal direction D 1 of the bobbin 84.

  The center core 81 is disposed at the center of the bobbin 84 and at the central opening of the winding of the induction coil 85. The center core 81 extends in the longitudinal direction D1 in the opening portion of the induction coil 85. The center core 81 guides the magnetic flux generated by exciting the induction coil 85 to the fixing belt 75 side, and is made of a magnetic metal. The center core 81 and the arch core 82 and the side core 83 form a magnetic path that is a path of magnetic flux from the induction coil 85. In other words, the center core 81, the arch core 82, the side core 83, and the induction coil 85 constitute a magnetic circuit.

  The magnetic flux shielding member 86 is attached to the housing 76A. As shown in FIG. 3, the magnetic flux shielding member 86 has a rotating body 88 formed in a long cylindrical shape in the longitudinal direction D <b> 1 of the fixing belt 75. The rotating body 88 is provided so as to surround the periphery of the center core 81 (see FIG. 2). The rotating body 88 is supported by the housing 76A so as to be rotatable around the center core 81. The rotating body 88 is formed of a flexible magnetic member made of a heat resistant resin such as a polyimide resin containing ferrite powder. When the induction coil 85 is excited and the center core 81 generates a magnetic flux, the magnetic flux passes through the rotating body 88 and further passes through the fixing belt 75 and reaches the heating roller 71. A connecting shaft 124 of the driving device 100 described later is connected to one end of the rotating body 88. For this reason, when the rotational driving force is supplied from the driving device 100 via the connecting shaft 124, the magnetic flux shielding member 86 is rotationally driven to a predetermined position.

  When the magnetic flux shielding member 86 is moved to a later-described shielding position defined between the non-fixing area of the fixing belt 75 and the center core 81, the magnetic flux shielding member 86 travels from the center core 81 to the heating roller 71 through the non-fixing area. It has a shielding part 87 that shields the magnetic path of the magnetic flux. Here, the non-fixing area includes the fixing belt 75 and the pressure roller when a small size sheet having a size in the width direction smaller than the maximum size printing sheet that can be fixed by the fixing device 16 is conveyed to the fixing device 16. 80 is a region where the sheet 80 is in direct contact and is not fixed to the small size paper. In other words, the non-fixing area is an area outside the fixing belt 75 in the width direction with respect to the small size sheet.

  As shown in FIG. 3, the shielding portion 87 is provided on the surface of the rotating body 88, and specifically, provided on the surface of each end portion of the rotating body 88. The shielding part 87 is formed in a sheet shape from a non-magnetic material having good conductivity such as copper or aluminum. The shielding part 87 is provided so as to cover a part of the outer peripheral surface at both ends of the rotating body 88. In the present embodiment, the magnetic flux shielding member 86 has a shielding position where the shielding portion 87 is disposed between the non-fixing area of the fixing belt 75 and the center core 81, and a retreating position away from the shielding position (FIG. 2). The position is supported so as to be rotatable. The magnetic flux shielding member 86 receives the rotational driving force supplied from the driving device 100 and rotates between the shielding position and the retracted position. When the fixing process is performed on the small size paper, the control unit 8 controls the motor 104 of the driving device 100 to move the magnetic flux shielding member 86 to the shielding position. Further, when the fixing process is performed on the maximum size printing paper larger than the small size paper, the control unit 8 controls the motor 104 to move the magnetic flux shielding member 86 to the retracted position.

  When the magnetic flux shielding member 86 is moved to the shielding position, the shielding part 87 shields the magnetic path between the center core 81 and the heating roller 71. As described above, since the shielding part 87 is made of a nonmagnetic material, when the magnetic flux shielding member 86 is disposed at the shielding position, when the magnetic flux generated from the center core 81 penetrates the shielding part 87, An induced current is generated in the shielding part 87, and a magnetic flux in a direction opposite to the magnetic flux of the center core 81 is generated. With this reverse magnetic flux, the magnetic flux from the center core 81 toward the heating roller 71 is canceled in the unfixed region, and the magnetic path between the center core 81 and the heating roller 71 is shielded. Thereby, the unfixed area is not heated.

  In FIG. 2, a shield frame 76B is integrally attached to the housing 76A on the left side of the housing 76A. The shield frame 76 </ b> B faces the induction heating device 76 on the side opposite to the fixing belt 75 and extends in the longitudinal direction D <b> 1 of the fixing belt 75. The shield frame 76 </ b> B prevents the magnetic flux generated by the induction heating device 76 from leaking out of the fixing device 16. A cooling fan 90 is provided on the back side (left side) of the shield frame 76B. The cooling fan 90 cools the induction heating device 76 by blowing air toward the induction heating device 76, and is attached to a main body frame (not shown) of the image forming apparatus 10. In the present embodiment, as shown in FIG. 3, three cooling fans 90 are arranged at equal intervals in the central portion of the shield frame 76B in the longitudinal direction D1.

  An air passage 92 is formed between the cooling fan 90 and the shield frame 76B through which the cooling air (air flow) blown out from the cooling fan 90 can flow. The air path 92 is a space formed between the cooling fan 90 and the shield frame 76B, and is a space long in the longitudinal direction D1. The cooling fan 73 is a blower fan that generates an air flow for cooling the induction heating device 76, and is, for example, an axial fan. By driving the cooling fan 90, the cooling air is blown out to the air passage 92, and the cooling air is blown toward the shield frame 76B. Thereby, the induction heating device 76 is cooled.

  As shown in FIG. 4, a guide portion 93 is provided on one side of the longitudinal direction D1 of the air passage 92, and a guide portion 94 (an example of the guide portion of the present invention) is provided on the other side of the longitudinal direction D1. Is provided. The guide portions 93 and 94 form air passages 92A and 92B in which the wind blown from the cooling fan 90 and deflected against the side surface of the shield frame 76B of the induction heating device 76 is directed outward in the longitudinal direction D1. Specifically, the air passages 92A and 92B are formed by the guide portions 93 and 94 and the side surface of the shield frame 76B. That is, the guide portions 93 and 94 further guide the wind deflected to the outside in the longitudinal direction D1 by hitting the side surface of the shield frame 76B toward the outside in the longitudinal direction D1. In the present embodiment, the guide portion 94 guides the wind deflected to the outside in the longitudinal direction D1 by hitting the side surface of the shield frame 76B toward a slit 131 formed on the bottom surface 114 of the driving device 100 described later.

  When the image forming operation is started in the image forming apparatus 10, the induction heating device 76 heats the heating roller 71 by the control signal output from the control unit 8 (see FIG. 1), and the fixing belt 75 is indirectly heated by the heat. Heat up. Further, the heating roller 71, the fixing roller 72, the pressure roller 80, and the fixing belt 75 are respectively rotated by a motor (not shown). At this time, the cooling fan 90 is driven to blow cooling air. Then, the cooling air hits the shield frame 76B, and the shield frame 76B is cooled, whereby the induction heating device 76 is cooled. At this time, the air is guided by the guide portions 93 and 94 to the portion of the shield frame 76B where the air flow from the cooling fan 90 is not directly applied (both ends in the longitudinal direction D1 of the shield frame 76B). .

[Drive device 100]
As shown in FIG. 4, the driving device 100 is attached to the housing 16 </ b> A of the fixing device 16. The driving device 100 is provided at one end of the fixing device 16 in the longitudinal direction D1. In the present embodiment, the driving device 100 is provided at an end portion on the near side in FIG. The driving device 100 supplies a rotational driving force to the magnetic flux shielding member 86 and transmits a force for moving the magnetic flux shielding member 86 to the retracted position or the shielding position. As shown in FIG. 5, the driving device 100 includes a motor 104 (an example of a driving source of the present invention), an output gear 106 (see FIG. 7) of the motor 104, and a large-diameter gear 107 (the transmission gear of the present invention). An example), a drying member 108 (see FIG. 7, an example of the drying unit of the present invention), and a housing 102 (an example of the housing of the present invention) that accommodates these members.

  The housing 102 includes a box-shaped main body case 111 having a bottom plate 114 (see FIG. 7), and a plate-shaped frame 112 attached to the main body case 111 so as to cover the opening of the main body case 111. The main body case 111 is formed of a synthetic resin having heat resistance. The frame 112 is for supporting the motor 104 and is formed of sheet metal. The main body case 111 has a side wall 115 erected vertically from the outer peripheral end of the bottom plate 114. The bottom plate 114 is fixed to the housing 16A of the fixing device 16 with screws or the like.

  As shown in FIG. 6, a gear accommodating portion 116 is provided on the bottom plate 114 of the housing 102. Between the bottom plate 114 and the large-diameter gear 107, a small-diameter gear (not shown) integrally formed coaxially with the large-diameter gear 107 and an intermediate gear (not shown) connected to the small-diameter gear are provided. It has been. The small diameter gear and the intermediate gear are accommodated in a gear accommodating portion 116. The intermediate gear is integrally formed with a connecting shaft 124 extending from the center thereof. The connecting shaft 124 extends through the gear housing 116 to the outside, that is, the fixing device 16 side. A connecting portion 125 that is connected to the end portion of the magnetic flux shielding member 86 is provided at the distal end portion of the connecting shaft 124.

  FIG. 7 is a perspective view showing a state where the frame 112 is removed from the housing 102 of the driving apparatus 100. As shown in FIG. 7, a large-diameter gear 107 for transmitting the rotational driving force of the motor 104 to the magnetic flux shielding member 86 is provided inside the housing 102. The large-diameter gear 107 is made of a water-absorbing resin, specifically made of nylon resin. The large-diameter gear 107 is rotatably supported by the main body case 111. The large-diameter gear 107 has teeth 121 on the outer peripheral portion and a cylindrical bearing portion 122 on the central portion. A shaft 118 is erected substantially at the center of the bottom plate 114. The shaft portion 118 is formed integrally with the main body case 111. By attaching the bearing portion 122 to the shaft portion 118, the large diameter gear 107 is rotatably supported by the main body case 111.

  The motor 104 is fixed to the outer surface of the frame 112. An output shaft of the motor 104 extends through the frame 112 into the housing 102. An output gear 106 made of metal is fixed to the output shaft of the motor 104. The output gear 106 is connected to the teeth 121 of the large diameter gear 107. Thus, when the motor 104 is rotationally driven, the rotational driving force is applied to the magnetic flux shielding member 86 via the output gear 106, the large diameter gear 107, the small diameter gear, the intermediate gear, the connecting shaft 124, and the connecting portion 125. introduce.

  In the driving device 100 of the fixing device 16 configured as described above, when the large-diameter gear 107 made of a water absorbent resin such as nylon is used, the water absorbent resin expands when it absorbs moisture. Therefore, the large-diameter gear 107 needs to be designed to have a size that takes into account expansion after water absorption. For example, it is necessary to design the clearance between the shaft portion 118 and the bearing portion 122 so that the bearing portion 122 expands due to water absorption. In particular, in the driving device 100 provided in the vicinity of the fixing device 16, the moisture contained in the printing paper evaporates due to heating during the fixing process, and the water vapor enters the housing 102 of the driving device 100, resulting in a large amount. Since it is easy to be absorbed by the diameter gear 107, it is highly necessary to design in consideration of expansion. However, when the inner diameter of the bearing portion 122 of the large-diameter gear 107 is increased in consideration of the expansion, the bearing portion 122 is loose. For this reason, during the period from when the image forming apparatus 10 starts the image forming operation until the large diameter gear 107 absorbs water and expands, a transmission failure such as tooth skipping occurs due to the backlash of the large diameter gear 107. Sound may be produced. For this reason, in the driving apparatus 100 of the present embodiment, the drying member 108 is provided inside as described above.

  The drying member 108 is attached to the inside of the housing 102 of the driving apparatus 100, specifically, to the main body case 111. The drying member 108 is for drying the air inside the housing 102. The drying member 108 is a member in which a desiccant such as silica gel is accommodated and sealed in a sheet-like accommodation case formed of a material having air permeability such as a nonwoven fabric. Such a drying member 108 has higher water absorption than a water-absorbing resin such as nylon, and therefore absorbs water vapor before it is absorbed by the large-diameter gear 107 even when water vapor enters the inside of the housing 102. can do.

  As shown in FIG. 7, the drying member 108 is affixed to the inner surface of the bottom plate 114, and is disposed between the bottom plate 114, the output gear 106, and the large-diameter gear 20. The amount of the desiccant in the drying member 108 is determined according to the flow of airflow including water vapor around the fixing device 16 and the position of the driving device 100.

  As described above, since the drying member 108 is provided inside the housing 102, even when the large-diameter gear 107 made of water-absorbing resin is used in the driving device 100, the backlash considering the expansion due to water absorption is taken into consideration. Need not be provided on the large-diameter gear 107. As a result, it is possible to prevent transmission failure such as tooth skipping due to looseness of the large-diameter gear 107 and generation of abnormal noise, and to smoothly transmit the rotational driving force to the magnetic flux shielding member 86.

  Further, as shown in FIG. 6, the driving device 100 has three slits 131 (an example of the through hole of the present invention) formed in the bottom plate 114 of the main body case 111. The slit 131 is an example of the drying unit of the present invention. The slit 131 passes through the bottom plate 114, so that air outside the housing 102 can flow into the housing 102 through the slit 131. The slit 131 is formed at a position corresponding to the air path 94A. For this reason, the wind blown from the cooling fan 90 and deflected by hitting the side surface of the shield frame 76B of the induction heating device 76 is directed to the housing 102 of the driving device 100 through the air passage 94A and into the housing 102 through the slit 131. Inflow. Thus, since the air flow blown from the cooling fan 90 flows into the housing 102, the large-diameter gear 107 is prevented from expanding due to water vapor. In particular, since the wind deflected against the side surface of the shield frame 76B is heated by heat exchange with the shield frame 76B, the heated warm air flows into the housing 102, thereby drying the air in the housing 102. be able to.

  In the driving apparatus 100 of the present embodiment, as shown in FIG. 7, the drying member 108 is attached to the inner surface of the bottom plate 114 of the main body case 111 at a position where three slits 131 are formed. For this reason, even if the desiccant absorbs the water vapor in the housing 102, the desiccant can be dried when the air flow flowing in from the slit 131 passes through the drying member 108. For this reason, even if the desiccant becomes unable to absorb water vapor, the cooling fan 90 is driven so that the desiccant can absorb water vapor again, and the air flow flowing from the slit 131 and the drying member Both 108 can promote drying in the housing 102.

  In the above-described embodiment, the configuration in which the drying member 108 is provided inside the housing 102 and the configuration in which the slit 131 is formed in the bottom plate 114 of the main body case 111 are illustrated as an example of the drying unit of the present invention. In the present invention, any one of the drying member 108 and the slit 131 may be provided in the driving device 100.

8: Control unit 10: Image forming device 16: Fixing device 90: Cooling fan 92: Air passage 93, 94: Guide portion 93A, 94A: Air passage 100: Drive device 102: Housing 108: Drying member 131: Slit

Claims (10)

A driving device for transmitting a rotational driving force output from a driving source to a driving member provided in the fixing device,
A housing,
A transmission gear that is provided inside the housing and is made of a water-absorbing resin, and that transmits the rotational driving force to the driving member;
And a drying unit that dries air inside the housing.   The drive unit according to claim 1, wherein the drying unit includes a desiccant that is provided inside the housing and has higher water absorption than the water-absorbent resin.   The drive device according to claim 1, wherein the water absorbent resin is a nylon resin. A driving device for supplying a rotational driving force output from a driving source;
A driving member that receives the rotational driving force supplied from the driving device and drives the driving member;
A fixing member that is heated during the fixing process;
A heating device for heating the fixing member,
The driving device includes:
A housing,
A transmission gear that is provided inside the housing and is made of a water-absorbing resin, and that transmits the rotational driving force to the driving member;
A fixing unit that dries air inside the housing.   The fixing device according to claim 4, wherein the drying unit includes a desiccant that is provided inside the housing and has higher water absorption than the water-absorbent resin. A blower for blowing air toward the heating device;
A guide portion that forms an air path toward the drive device by the wind that is blown from the blower and deflected by hitting a side surface of the heating device;
5. The fixing device according to claim 4, wherein the drying unit includes a through hole formed on a side wall of the casing and guides the wind striking the side wall through the air passage to the inside of the casing.   The drying unit is provided inside the housing and includes a desiccant having higher water absorption than the water absorbent resin, and the desiccant is an inner surface of a side wall of the housing that is struck by air passing through the air path. The fixing device according to claim 6, wherein the fixing device is attached at a position where the through hole is formed.   The fixing device according to claim 4, wherein the water absorbent resin is a nylon resin. The heating device is
An induction coil provided facing the fixing member and generating a magnetic flux for heating the fixing member;
A magnetic core that forms a magnetic path that passes through the induction coil and the fixing member and guides a magnetic flux to the fixing member, and
The driving member is moved to a shielding position defined between a non-fixing region of the fixing member and the magnetic core during a fixing process on a printing paper having a size smaller than the maximum sized printing paper. The fixing device according to claim 4, wherein the fixing device is a magnetic flux shielding member.   An image forming apparatus comprising the fixing device according to claim 4, wherein the image forming device forms an image on a printing paper using toner that can be fixed by the fixing device.

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