JP6136833B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In Patent Document 1, an object is to provide a fixing device capable of protecting a thermistor from charges accumulated on a fixing roller. Then, in the fixing device described in Patent Document 1, charges accumulated on the surface of the fixing roller are discharged to a lightning rod facing the surface of the fixing roller in close proximity. Further, the shortest distance from the tip of the lightning rod to the fixing roller is configured to be shorter than the shortest distance from the exposed portion of the thermistor probe (portion not covered by the insulating cover) to the fixing roller. Thereby, the electric charge accumulated on the surface of the fixing roller is surely discharged to the lightning rod without being discharged to the exposed portion of the probe.

JP 2005-338628 A

  An object of this invention is to suppress the damage of the detection part accompanying the electrostatic discharge from a user.

First aspect of the present invention, a rotating member rotatable, and an outer peripheral member conductivity than the rotary member is provided on the outer periphery of the lower and the rotary member, a fixing member for fixing the toner on the recording material the detecting means for detecting a state of the outer member, the rotating member and the first discharge member electrically connected, to ground provided et al is in a position spaced from the first discharge member, the second by the discharge 1 a discharge member second discharge member Ru receive charge from, said a rotary member at between said first discharge member, the anode is electrically connected to the rotating member side, the cathode is the first discharge member side a diode connected to a constant deposition apparatus Ru comprising a.
According to a second aspect of the invention, one end is electrically connected between the first discharge member and the diode, a fixing device 請 Motomeko 1 wherein Ru comprising a resistive element and the other end is grounded.
According to a third aspect of the present invention, the detecting means is provided in contact with the outer peripheral member, measures the temperature of the outer peripheral member, and sends a temperature-related signal to the control board connected via the signal line. a fixing device 請 Motomeko 1 or 2, wherein Ru comprising a.
According to a fourth aspect of the present invention, the first discharge member includes a first corner portion projecting toward the second discharge member, and the second discharge member is the first corner portion of the first discharge member. a second corner portion protruding toward, wherein the first discharge member and the second discharge member, any one of claims 請 Motomeko 1 to 3 is arranged in a direction in which each side intersect each other The fixing device.
According to a fifth aspect, a rotating member rotatable, and an outer peripheral member conductivity than the rotary member is provided on the outer periphery of the lower and the rotary member, a fixing member for fixing the toner on the recording material a detection means for detecting a state of the peripheral member, the rotating member and is electrically connected, when the predetermined voltage is applied to the rotary member, the current from the rotating member side by the air discharge a discharge means for flowing to the ground, in between the discharge means and the rotary member, the anode is connected to the rotating member side, and a diode cathode is connected to the discharge means side, a constant deposition apparatus Ru provided with is there.
According to a sixth aspect of the present invention, there is provided a toner image forming portion for forming a toner image on a recording material, a rotatable rotating member, and an outer peripheral member having lower conductivity than the rotating member and provided on the outer periphery of the rotating member. A fixing member for fixing the toner image formed by the toner image forming unit to the recording material, a detecting means for detecting the state of the outer peripheral member, and a first discharge electrically connected to the rotating member. and member, wherein the grounded provided et al is in a position spaced apart from the first discharge member, between the second discharge member Ru receive charge from the first discharge member by discharge, and the rotary member and the first discharge member at the anode is connected to the rotating member side, and a diode cathode is connected to the first discharge member, which is images forming apparatus Ru comprising a.

According to the first aspect of the present invention, it is possible to suppress damage to the detection means due to electrostatic discharge from the user.
According to the second aspect of the present invention, the rotating member can be set to a predetermined potential.
According to invention of Claim 3, it can suppress that the control board connected via a temperature sensor and a signal line receives the damage accompanying electrostatic discharge.
According to the fourth aspect of the present invention, the discharge start voltage can be easily adjusted.
According to the fifth aspect of the present invention, it is possible to suppress damage to the detection means due to electrostatic discharge from the user.
According to the sixth aspect of the present invention, it is possible to suppress damage to the detection means due to electrostatic discharge from the user.

1 is a schematic configuration diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. 1 is a schematic configuration diagram of a fixing device to which an embodiment of the present invention is applied. 1 is a perspective view of a fixing device to which an embodiment of the present invention is applied. FIG. 2 is a schematic configuration diagram around a biasing unit of a fixing device to which an exemplary embodiment of the present invention is applied. (A) is a schematic block diagram of the release lever, and (b) is a diagram for explaining the arrangement of the release lever. It is a figure explaining operation | movement of a cancellation | release lever. It is a figure for demonstrating the circuit of a grounding mechanism. It is a figure for demonstrating the structural example of a grounding mechanism. It is a figure for demonstrating in detail the structure of a discharge terminal pair. It is a figure for demonstrating the structure of the 2nd supporting member holding a grounding mechanism. (A) is a figure for demonstrating the structure of a temperature sensor, (b) is a figure for demonstrating arrangement | positioning of the temperature sensor provided in the fixing roll. (A) is a figure for demonstrating the structure of the temperature sensor of a comparative example, (b) is a figure for demonstrating arrangement | positioning of the temperature sensor of a comparative example. (A) is a figure explaining the relationship between the shape of a discharge terminal pair, and the ease of discharge, (b) is a figure which shows the measurement result of the relationship between the shape of a discharge terminal pair and the maximum discharge distance. It is a figure for demonstrating the grounding mechanism of a modification. It is a figure for demonstrating the structural example of the grounding mechanism of a modification.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Image forming apparatus 1>
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus 1 to which the exemplary embodiment is applied.
An image forming apparatus 1 shown in FIG. 1 is a so-called tandem color printer. The image forming apparatus 1 includes an image forming unit 10 that forms an image corresponding to image data of each color. The image forming apparatus 1 has a control board (not shown) and is connected to a control unit 5 that controls the operation of the entire image forming apparatus 1 and an external device such as a personal computer (PC) 80 or an image reading device 90. An image processing unit 6 that performs predetermined image processing on image data received from these, and a user interface 7 that receives an instruction given by a user operation are provided. Further, the image forming apparatus 1 includes a power supply unit 8 that supplies power to each unit. Furthermore, the image forming apparatus 1 includes a sheet stacking unit 40 that stacks sheets (recording materials) supplied to the image forming unit 10, and a paper discharge stacking unit 46 that stacks sheets on which images are formed by the image forming unit 10. And.

<Image forming unit 10>
The image forming unit 10 includes four image forming units 11 (specifically, 11Y, 11M, 11C, and 11K) arranged in parallel at a predetermined interval. In addition, the image forming unit 10 applies a bias voltage to a conveying belt 18 that conveys a sheet, a driving roll 19 that rotates the conveying belt 18, in order to multiplex-transfer the color toner images formed by the image forming units 11. The image forming unit 11 includes a transfer roll 21 that transfers the color toner images formed on the image forming units 11 to a sheet, and a fixing device 100 that fixes the transferred color toner images on the sheet.
In addition, the image forming unit 10 includes a pickup roller 68 that sequentially feeds the sheets stacked on the sheet stacking unit 40, and a conveyance roll 69 that conveys the sheet fed by the pickup roller 68. Further, the image forming unit 10 includes an exit sensor 70 that detects passage of a sheet on which the toner image is fixed in the fixing device 100.

  An image forming unit 11, which is an example of a toner image forming unit, uniformly forms a photosensitive drum 12 that forms an electrostatic latent image and holds a toner image, and a surface of the photosensitive drum 12 at a predetermined potential. A charging device 13 for charging, an LED print head (LPH) 14 for exposing the photosensitive drum 12 charged by the charging device 13 based on image data, and an electrostatic latent image formed on the photosensitive drum 12 A developing device 20 that develops using a developer and a cleaner 16 that cleans the surface of the photosensitive drum 12 after transfer are provided. The image forming units 11Y, 11M, 11C, and 11K are configured in substantially the same manner except for the toner stored in the developing device 20. Each of the image forming units 11Y, 11M, 11C, and 11K forms toner images of yellow (Y), magenta (M), cyan (C), and black (K).

<Operation of Image Forming Apparatus 1>
In the image forming apparatus 1 according to the present embodiment, the image data input from the PC 80 or the image reading apparatus 90 is subjected to predetermined image processing by the image processing unit 6, and then each image data is received via an interface (not shown). The image is sent to the image forming unit 11. For example, in the image forming unit 11K that forms a black (K) toner image, the photosensitive drum 12 is uniformly charged at a predetermined potential by the charger 13 while rotating in the arrow A direction, and image processing is performed. Based on the image data transmitted from the unit 6, scanning exposure is performed by the LPH 14. Thereby, an electrostatic latent image related to a black (K) color image is formed on the photosensitive drum 12. The electrostatic latent image formed on the photosensitive drum 12 is developed by the developing device 20, and a black (K) toner image is formed on the photosensitive drum 12. Similarly, in the image forming units 11Y, 11M, and 11C, yellow (Y), magenta (M), and cyan (C) toner images are formed, respectively.

  On the other hand, the paper stacked on the paper stacking unit 40 is sent out by the pickup roller 68. The sheet fed by the pickup roller 68 is superimposed on the toner images of the respective colors formed by the image forming units 11 while being conveyed by the conveying belt 18 moving in the arrow B direction. The sheet on which the superimposed toner image is electrostatically transferred is peeled off from the conveyance belt 18 and conveyed to the fixing device 100. The toner image on the sheet is fixed on the sheet by being subjected to a fixing process by heat and pressure by the fixing device 100. The sheet on which the fixed image is formed is further transported by the transport roll 69, detected by the exit sensor 70, and then stacked on the paper discharge stacking unit 46.

<Configuration of Fixing Device 100>
FIG. 2 is a schematic configuration diagram of the fixing device 100 to which the embodiment of the present invention is applied. FIG. 3 is a perspective view of the fixing device 100 to which the embodiment of the present invention is applied. FIG. 4 is a schematic configuration diagram around the urging unit 130 of the fixing device 100 to which the exemplary embodiment of the present invention is applied. 2 shows a schematic configuration diagram in section II in FIG. 3, and FIG. 4 shows a schematic configuration diagram in section IV in FIG.

  The fixing device 100 according to the present embodiment is detachably provided to the image forming apparatus 1. As shown in FIG. 2, the fixing device 100 includes a fixing roll 101 for fixing a toner image formed on a sheet, a pressure belt 103 disposed so as to face the fixing roll 101, and each functional member. , An urging portion 130 (see FIG. 4) that urges the pressure belt 103 against the fixing roll 101 to form a nip portion N, and a pressure contact force (nip pressure) of the nip portion N. ) And a grounding mechanism 170 (see FIG. 7) for grounding the fixing roll 101 and its peripheral members.

  In the illustrated example, the fixing device 100 includes a fixing inlet guide 111 that guides the sheet to the nip portion N on the upstream side in the sheet conveyance direction from the nip portion N, and the nip portion N on the downstream side in the sheet conveyance direction from the nip portion N. And a fixing exit guide 113 for guiding the sheet conveyed from the sheet to a conveyance roll 69 (see FIG. 1). In other words, the fixing inlet guide 111 is a metal plate member made of, for example, aluminum. Further, the fixing outlet guide 113 is made of, for example, resin, and is provided so as to be rotatable about the rotation shaft 113a (see arrow D) in the illustrated example.

  In the following description, the depth direction in FIG. 2 (the direction along the axial direction of the fixing roll 101) is the Y direction, the horizontal direction orthogonal to the Y direction (the left-right direction in the figure) is the X direction, and the X direction and the Y direction are The perpendicular direction (vertical direction in the figure) orthogonal to the Z direction. In FIG. 2, a direction toward the right side in the X direction is defined as + X direction, a direction toward the back side in the Y direction is defined as + Y direction, and a direction toward the top side in the Z direction is defined as + Z direction.

<Fixing roll 101>
As shown in FIG. 2, a fixing roll 101, which is an example of a fixing member, has a conductivity lower than that of a cylindrical cored bar 101a around a metal cylindrical cored bar (rotating member) 101a made of, for example, aluminum. This is a cylindrical roll formed by laminating a so-called insulating member, for example, a heat-resistant elastic body layer 101b made of rubber and a release layer 101c made of, for example, fluorine rubber. In this cylindrical roll, both ends of the cylindrical metal core 101a are supported by metal bearings 115 (see FIG. 7), and rotate around the rotation shaft 101e. The heat-resistant elastic layer 101b and the release layer 101c may be referred to as an insulating coating (outer peripheral member) 101d.

  In addition, the fixing roll 101 includes a halogen lamp 105 as a heat generation source on the inside and a temperature sensor 112 provided in contact with the outer peripheral surface of an insulating coating 101d (release layer 101c) which is an example of a detection unit. Further, the fixing roll 101 is provided in connection with a drive motor (not shown).

<Pressure belt 103>
As shown in FIG. 2, the pressure belt 103 holds the pressure pad 107, the pressure pad 107 disposed inside the pressure belt body 104, and the pressure pad 107 inside the pressure belt body 104. A pad holder 108 and a belt guide member 109 that supports the pressure belt main body 104 from the inside are provided.

The pressure belt main body 104 is formed of a seamless endless belt whose original shape is formed in a cylindrical shape so that a defect due to the seam does not occur in the formed image. The pressure belt main body 104 is constituted by a single layer formed by blending, for example, a fluororesin and a reinforcing filler.
The pressing pad 107 is made of an elastic body such as silicone rubber or fluorine rubber, for example. The pressing pad 107 includes a low friction sheet (not shown) on the surface in contact with the pressing belt body 104 in order to reduce sliding resistance between the inner peripheral surface of the pressing belt body 104 and the pressing pad 107.

The pad holder 108 is formed of, for example, a metal plate member. The pad holder 108 holds the pressing pad 107 in a position where the pressing pad 107 faces the fixing roll 101 through the pressing belt main body 104 inside the pressing belt main body 104.
The belt guide member 109 is formed of, for example, a resin member, and rotatably supports the pressure belt main body 104 from the inside of the pressure belt main body 104.

  The pressure belt 103 is arranged so that the pressure belt main body 104 is pressed against the fixing roll 101 via an urging portion 130 (see FIG. 4) as will be described later. When the pressure belt main body 104 is pressed against the fixing roll 101, the pressing pad 107 of the pressure belt main body 104 is pressed against the fixing roll 101 via the pressure belt main body 104.

<Operation of Fixing Roll 101 and Pressure Belt 103>
In such a configuration, the fixing roll 101 is rotated by being driven by a drive motor (not shown) (see arrow C), and the pressure belt 103 is also rotated following the rotation. The sheet on which the toner image is electrostatically transferred by the image forming unit 10 (see FIG. 1) is conveyed to the nip N while being guided by the fixing inlet guide 111. When the toner image on the paper passes through the nip portion N, the toner image is fixed on the paper by the pressure acting on the nip portion N and the heat supplied from the fixing roll 101. Then, the sheet on which the image is fixed is conveyed to the conveying roll 69 while pushing up the fixing outlet guide 113 (see the fixing outlet guide 113 indicated by a broken line in the drawing).

<Case 110>
As shown in FIG. 3, the casing 110 has a substantially rectangular parallelepiped shape whose longitudinal direction is along the Y direction. Functional members such as the fixing roll 101 and the pressure belt 103 described above are disposed inside the casing 110. It should be noted that biasing portions 130 (see FIG. 4) are respectively provided inside both ends of the housing 110 in the Y direction. In addition, release levers 150 are respectively provided outside both ends of the housing 110 in the Y direction.

<Biasing unit 130>
As shown in FIG. 4, the urging unit 130 is provided at the end of the pressure belt 103 in the Y direction. In the illustrated example, the urging portion 130 holds a claw portion 106 that is a part of the pressure belt 103 and provided at the end of the pressure belt 103.

The urging unit 130 includes a lever nip 131 that holds the pressure belt 103 and that can be moved forward and backward with respect to the fixing roll 101, and a spring 133 that urges the lever nip 131.
The lever nip 131 is a metal plate member made of, for example, aluminum. The lever nip 131 includes a rotation shaft 131a, a holder groove 131b into which the claw portion 106 of the pressure belt 103 is inserted, a spring protrusion 131c that is a protrusion on which one end of the spring 133 is hung, and a rotation shaft of the release lever 150. And a release lever hole 131d that rotatably supports 150a (described later).

Here, the spring protrusion 131c of the lever nip 131 receives the elastic force of the spring 133 and is biased in the −X direction. The biased lever nip 131 rotates around the rotation shaft 131a (see arrow E), and presses the claw portion 106 of the pressure belt 103 inserted in the holder groove 131b toward the fixing roll 101 side. As a result, the urging unit 130 presses the pressure belt 103 against the fixing roll 101.
In the illustrated example, the release lever hole 131 d of the lever nip 131 is located on the outer peripheral side of the fixing device 100.

<Release lever 150>
5A is a schematic configuration diagram of the release lever 150, and FIG. 5B is a diagram illustrating the arrangement of the release lever 150. FIG. FIG. 6 is a view for explaining the operation of the release lever 150.
As shown in FIG. 5A, the release lever 150 includes a rotation shaft 150a, a release lever main body 150b provided to be rotatable around the rotation shaft 150a, and a cam 150c provided around the rotation shaft 150a. Is provided. The cam 150c includes a base circle 150c1 and a cam crest 150c2.

  Here, the rotation shaft 150 a of the release lever 150 is rotatably supported by the release lever hole 131 d of the lever nip 131. Further, the cam 150 c of the release lever 150 is disposed so as to abut against the abutted portion 110 a provided in the housing 110. As the release lever 150 rotates about the rotation shaft 150a, the region of the cam 150c that contacts the abutted portion 110a changes.

  More specifically, as shown in FIG. 5 (b), the cam 150c is in the normal position (see the release lever 150 indicated by the solid line) where the release lever 150 is disposed so that the release lever main body 150b is along the Z direction. Base circle 150c1 contacts the abutted portion 110a. Further, in the standing position where the release lever main body 150b is arranged along the X direction and the release lever 150 is raised (see the broken release lever 150), the cam crest 150c2 of the cam 150c is the abutted portion. 110a is contacted.

  When the user operates the release lever 150 configured as described above, the posture of the release lever 150 is switched between the normal position and the standing position. Then, as shown in FIG. 5B, the position of the rotation shaft 150 a is changed by switching the posture of the release lever 150. As a result, the posture of the lever nip 131 that supports the rotating shaft 150a changes, and the nip pressure at the nip portion changes.

  That is, as shown in FIG. 6, when the release lever 150 is in the normal position (see the solid release lever 150) and the lever nip 131 is disposed at the position P <b> 1 close to the fixing roll 101, Thus, the pressure belt 103 is urged, and a predetermined nip pressure is generated in the nip portion N. On the other hand, in a state where the release lever 150 is in the upright position (see the broken release lever 150) and the lever nip 131 is disposed at the position P0 that is further away from the fixing roll 101 than the position P1, the fixing roll 101 and the pressure belt 103 are used. Are separated from each other, and no nip pressure is generated in the nip portion N.

  When an image is formed on a sheet in the image forming apparatus 1 (see FIG. 1), the release lever 150 is in the normal position, and the sheet passing through the nip portion N is pressed with a predetermined nip pressure. On the other hand, for example, when a paper jam (jamming) occurs in the fixing device 100, the release lever 150 is raised by the user's operation to be in the standing position. As a result, the nip pressure in the nip portion N is released, and the paper is easily removed.

<Circuit of the grounding mechanism 170>
FIG. 7 is a diagram for explaining a circuit of the grounding mechanism 170.
The grounding mechanism 170 includes a resistor (resistive element) 174 whose one end 174a is grounded. The grounding mechanism 170 includes a diode 172 having one end 172 a connected to the other end 174 b of the resistor 174 and the other end 172 b connected to the bearing 115 of the fixing roll 101. Furthermore, the grounding mechanism 170 includes a discharge terminal pair 180 in which one end 180 a is grounded and the other end 180 b is connected to the other end 174 b of the resistor 174. That is, in the grounding mechanism 170, the resistor 174 and the discharge terminal pair 180 are connected in parallel.

  The discharge terminal pair 180, which is an example of a discharge means, includes a first discharge terminal (first discharge member) 181 and a second discharge terminal (second discharge member) 183 made of, for example, stainless steel. The first discharge terminal 181 and the second discharge terminal 183 are provided to face each other at a separated position. The discharge terminal pair 180 normally does not pass current because the first discharge terminal 181 and the second discharge terminal 183 are separated from each other, but a voltage exceeding a predetermined voltage (discharge start voltage) is applied. And a current is caused to flow. In other words, the discharge terminal pair 180 functions as a so-called lightning rod, and transfers charges between the first discharge terminal 181 and the second discharge terminal 183 by air discharge.

  Although not described above, in the illustrated example, the bearing 115 of the fixing roll 101 is provided on a bearing inner ring 115a that holds a cylindrical cored bar 101a on the inner periphery, and on the outer periphery of the bearing inner ring 115a. And a bearing outer ring 115b to which the other end 172b of the diode 172 is connected. The bearing 115 includes a conducting member 115c that is an annular plate-like member provided coaxially with the bearing inner ring 115a and the bearing outer ring 115b and in contact with the bearing inner ring 115a and the bearing outer ring 115b. The conducting member 115c is made of, for example, a metal made of stainless steel, and electrically connects the bearing inner ring 115a and the bearing outer ring 115b. As a result, the bearing 115 electrically connects the diode 172 and the cylindrical cored bar 101a.

In the illustrated grounding mechanism 170, the fixing inlet guide 111 and the lever nip 131, the other end 174b of the resistor 174, the other end 180b of the discharge terminal pair 180, and the one end 172a of the diode 172 are electrically connected to each other. Connected.
Therefore, in the illustrated example, the fixing inlet guide 111, the lever nip 131, the bearing 115 of the fixing roll 101, and the cylindrical cored bar 101a of the fixing roll 101 have the same potential.

  Now, the grounding mechanism 170 grounds the fixing roll 101 and its peripheral members. Specifically, the grounding mechanism 170 electrically connects the fixing roll 101, the fixing inlet guide 111, and the lever nip 131 to the ground wire 110 e included in the image forming apparatus 1.

  Here, the resistor 174 and the diode 172 induce a charge having the same polarity as that of the toner to the insulating film 101 d of the fixing roll 101. In the illustrated example, the other end 172 b on the anode side of the diode 172 is connected to the bearing 115 of the fixing roll 101, and the one end 172 a on the cathode side of the diode 172 is connected to the resistor 174. With this configuration, the insulating coating 101d of the fixing roll 101 accumulates negative charges, and transfer of negatively charged toner onto the surface of the insulating coating 101d is suppressed.

In the grounding mechanism 170, since the diode 172 is provided, the potential of the surface of the insulating coating 101d can be stabilized.
Further, the grounding mechanism 170 has a configuration in which a predetermined potential difference is generated between the potential of the fixing inlet guide 111 and the ground potential by providing a resistor 174 whose one end 174a is grounded.

Here, depending on the arrangement of the transfer roll 21 and the fixing entrance guide 111, the leading edge of the sheet transferred by the transfer roll 21 (see FIG. 1) may be conveyed to the fixing entrance guide 111. May be disposed at a position straddling the transfer roll 21 and the fixing entrance guide 111. That is, the sheet may come into contact with both the transfer roll 21 and the fixing entrance guide 111 at the same time. For example, when the moisture content of the sheet is high, the charge for applying the transfer bias of the transfer roll 21 can flow to the ground via the sheet and the fixing inlet guide 111. In this case, a transfer failure in the transfer roll 21 may occur.
However, in the present embodiment, the resistor 174 is provided and a predetermined potential difference is generated between the potential of the fixing inlet guide 111 and the ground potential, thereby preventing the charge of the transfer roll 21 from flowing to the ground. Transfer defects in the transfer roll 21 are suppressed.

<Electrostatic discharge>
In the configuration as described above, when the user operates the release lever 150, electrostatic discharge may occur when the user brings his hand close to the bearing 115 of the fixing roll 101, the fixing inlet guide 111 or the lever nip 131. .
Here, unlike this embodiment, assuming that the grounding mechanism 170 does not include the discharge terminal pair 180, for example, when static electricity is applied to the lever nip 131, the overcurrent due to static electricity causes the resistor 174 from the lever nip 131. It can flow to the ground via the diode 172 and the bearing 115 and can flow to the cylindrical metal core 101a.

  Here, an insulating coating 101d is disposed around the cylindrical metal core 101a, and current normally flows from the cylindrical metal core 101a to the temperature sensor 112 provided in contact with the outer peripheral surface of the insulating coating 101d. It is suppressed. That is, the insulating coating 101d is configured to protect the temperature sensor 112.

However, when the cylindrical cored bar 101a is excessively charged due to an electrostatic overcurrent, a current flows through the insulating coating 101d. In addition, when a scratch 211 (see FIG. 12A) or a fine hole is formed in the insulating coating 101d and the insulating property of the insulating coating 101d is lost at least in part, the current passing through the insulating coating 101d Will increase.
The current passing through the insulating coating 101d flows to the control unit 5 through the temperature sensor 112 and the wiring cable 114 (described later). This may cause problems such as malfunction or damage of the temperature sensor 112 and the control unit 5 in some cases. To explain further, even if a protective circuit is provided in the control unit 5, if an excessive voltage is applied like static electricity from the human body, the protective function by the protective circuit may be insufficient.

  On the other hand, in the present embodiment, grounding mechanism 170 includes discharge terminal pair 180. This discharge terminal pair 180 reduces the current flowing to the cylindrical metal core 101a by flowing a current due to the occurrence of electrostatic discharge to the ground, and as a result, an overcurrent flows to the temperature sensor 112 and the control unit 5. Is suppressed.

<Configuration Example of Grounding Mechanism 170>
FIG. 8 is a diagram for explaining a configuration example of the grounding mechanism 170.
Next, a specific configuration example of the grounding mechanism 170 that realizes the circuit shown in FIG. 7 will be described with reference to FIG.
The grounding mechanism 170 in the illustrated configuration example is supported and fixed to the housing 110 by a first support member 110c and a second support member 110b (see FIG. 10) provided in the housing 110, respectively. Here, the first support member 110 c is a metal plate-like member made of, for example, aluminum, and electrically connects the lever nip 131 and the fixing inlet guide 111. The second support member 110b will be described later.

  In addition, the grounding mechanism 170 includes the diode 172, the resistor 174, and the discharge terminal pair 180 as described above, and also includes a bearing side member 171, a lever nip side member 173, and a ground side, each of which is a metal plate member made of aluminum, for example. A member 175 is provided. The bearing side member 171, the lever nip side member 173, and the ground side member 175 are provided at positions separated from each other, and the diode 172, the resistor 174, or the discharge terminal pair 180 is disposed therebetween.

  The bearing-side member 171 is in contact with the base 171a, the bearing 115 of the fixing roll 101 and electrically connected to the bearing 115, and the entire bearing-side member 171 is elastically deformed. A bent portion 171c serving as a fulcrum, and a second connection portion 171d connected to the other end 172b of the diode 172.

  The lever nip side member 173 includes a base portion 173a, a small piece portion 173f provided continuously with the base portion 173a, a first connection portion 173b provided on the small piece portion 173f and connected to one end 172a of the diode 172, and a lever nip side member 173. A bent portion 173c serving as a fulcrum when the whole is elastically deformed and a second connection portion 173d connected to the other end 174b of the resistor 174 are provided. The lever nip side member 173 includes a fixing hole 173e fixed to the first support member 110c via a bolt (not shown), and a first discharge terminal 181 (details will be described later) provided in the small piece portion 173f. Is provided.

  The ground side member 175 is continuous with the base portion 175a, the first connection portion 175b connected to one end 174a of the resistor 174, the bent portion 175c serving as a fulcrum when the entire ground side member 175 is elastically deformed, and the base portion 175a. Provided with a small piece portion 175d and a second discharge terminal 183 (details will be described later) provided on the small piece portion 175d. Here, the bent portion 175c is connected to a ground wire 110e (see FIG. 7) provided in the image forming apparatus 1.

Here, the bearing side member 171, the lever nip side member 173, and the ground side member 175 in the illustrated example can be easily formed by bending a metal plate punched into each shape.
Further, the bearing side member 171, the lever nip side member 173, and the ground side member 175 are provided with bent portions 171c, 173c, and 175c, respectively, and can be elastically deformed. This facilitates the work of disposing the diode 172 or the resistor 174 between the respective members.

  Furthermore, the base portion 175a of the ground side member 175, the base portion 171a of the bearing side member 171 and the base portion 173a of the lever nip side member 173 are arranged in this order in the Z direction, and are in a so-called three-layer positional relationship. Thus, by arranging the ground side member 175, the bearing side member 171 and the lever nip side member 173 at positions where they overlap each other, the dimensions of the grounding mechanism 170 in the X direction and the Y direction are suppressed.

<Discharge terminal pair 180>
FIG. 9 is a diagram for explaining the configuration of the discharge terminal pair 180 in detail. FIG. 9 is an enlarged view of a region surrounded by a square in FIG.
Next, the configuration of the discharge terminal pair 180 will be described in detail with reference to FIG.
First, the discharge terminal pair 180 includes the first discharge terminal 181 provided on the small piece portion 173f of the lever nip side member 173 and the second discharge terminal 183 provided on the small piece portion 175d of the ground side member 175 as described above. Prepare.

The first discharge terminal 181 is provided on one side of the lever nip side member 173 facing the second discharge terminal 183 and protrudes toward the second discharge terminal 183 (+ Y direction). More specifically, the first discharge terminal 181 is a so-called cusp-shaped plate-like member that has a narrower width as it approaches the second discharge terminal 183 and has an acute corner (first corner) 181a at its tip. is there.
Similarly, the second discharge terminal 183 is provided on one side of the ground-side member 175 facing the first discharge terminal 181 and protrudes toward the first discharge terminal 181 (−Y direction). More specifically, the second discharge terminal 183 becomes narrower as it gets closer to the first discharge terminal 181, and a so-called pointed plate-like plate having a corner (second corner) 183 a forming an acute angle at its tip. It is a member.
In addition, the 1st discharge terminal 181 and the 2nd discharge terminal 183 are mutually spaced apart, and the distance between the corner | angular part 181a and the corner | angular part 183a shall be about 0.1 mm-1 mm, for example.

  Here, the 1st discharge terminal 181 is comprised as a part of lever nip side member 173, for example, is formed by providing the notch 173g and 173h in the small piece part 173f. Similarly, the 2nd discharge terminal 183 is comprised as a part of ground side member 175, for example, is formed by providing the notch 175g in the small piece part 175d.

  Further, the small piece portion 173f of the lever nip side member 173 includes a surface whose normal line extends along the X direction, and the small piece portion 175d of the ground side member 175 includes a surface whose normal line extends along the Z direction. That is, in the illustrated example, the small piece portion 173f and the small piece portion 175d are arranged in directions that intersect (orthogonal) each other. By configuring in this way, the first discharge terminal 181 and the second discharge terminal 183 can be arranged even when there are restrictions on the layout such as when there are other members around the small piece portion 173f and the small piece portion 175d. It is.

  In addition, the first discharge terminal 181 and the second discharge terminal 183, which are each a plate member having a pointed shape, are opposed to the corner portion 181a of the first discharge terminal 181 and the corner portion 183a of the second discharge terminal 183, respectively. Are arranged in directions that intersect (orthogonal) each other. As a result, in the first discharge terminal 181 and the second discharge terminal 183, the areas facing each other other than the corners 181a and 183a are suppressed, and the corners 181a and 183a are more likely to be discharged.

<Second support member 110b>
FIG. 10 is a view for explaining the configuration of the second support member 110 b that holds the grounding mechanism 170.
Next, the second support member 110b will be described with reference to FIG. The second support member 110b is a substantially rectangular parallelepiped member made of resin or the like, and the outer peripheral surface is formed with irregularities corresponding to the constituent members of the grounding mechanism 170.

  For example, the second support member 110b includes a groove portion 110f for fitting and fixing the resistor 174 and a recess portion 110g for fitting and fixing the ground side member 175. Since the grounding mechanism 170 holds the ground side member 175 and the lever nip side member 173, it can be regarded as a positioning portion that determines the positions of the first discharge terminal 181 and the second discharge terminal 183.

  Also, as shown in FIG. 10, the main body of the resistor 174 held by the second support member 110b is located behind the second support member 110b when viewed from the axially central side of the fixing roll 101. The main body of the diode 172 (see FIG. 9) is located behind the lever nip side member 173. This limits user access to the diode 172 and resistor 174, further improving safety.

<Temperature sensor 112>
FIG. 11A is a diagram for explaining the configuration of the temperature sensor 112, and FIG. 11B is a diagram for explaining the arrangement of the temperature sensor 112 provided on the fixing roll 101.
As shown in FIG. 11A, in the illustrated example, the temperature sensor 112 is configured as a thermistor and is connected to the control unit 5 (see FIG. 1) via a wiring cable (signal line) 114. And a pair of probes 112b extending in a direction along the base 112a and a cover member 112c made of a so-called insulating member that covers the main part of the probe 112b. The probe 112b includes an exposed portion 112d that is not covered by the cover member 112c and exposed to the outside.

  As shown in FIG. 11B, when the temperature sensor 112 is disposed on the fixing roll 101, the cover member 112 c is in contact with the insulating coating 101 d of the fixing roll 101. The temperature sensor 112 detects a change in the resistance value of the probe 112b covered with the cover member 112c, thereby measuring the temperature of the insulating coating 101d and sending a signal related to the temperature via the wiring cable 114 to the control unit. 5 (see FIG. 1).

<Operation of Grounding Mechanism 170>
Next, the operation of the grounding mechanism 170 will be described with reference to FIGS. 4 and 7 to 11.
As described above, when the user operates the release lever 150, for example, when static electricity is applied to the lever nip 131, an overcurrent due to static electricity flows to the lever nip side member 173 via the lever nip 131 and the first support member 110c. . The current flowing to the lever nip side member 173 flows to the ground via the resistor 174 and the ground side member 175, and at the same time, the first discharge terminal 181 of the lever nip side member 173 and the second discharge terminal 183 of the ground side member 175. The air flows to the ground via the ground side member 175 while performing the air discharge between them.

  As a result, current flows from the lever nip side member 173 to the cylindrical cored bar 101a via the diode 172, the bearing side member 171 and the bearing 115, and the cylindrical cored bar 101a is prevented from being excessively charged. . More specifically, a current flows through the insulating coating 101d, and further, a current is suppressed from flowing to the control unit 5 via the exposed portion 112d, the base portion 112a, and the wiring cable 114 of the temperature sensor 112.

  Assuming a configuration in which the discharge terminal pair 180 is not provided unlike the illustrated example, the lever nip side member is configured in a configuration in which the discharge terminal pair 180 is not provided and a configuration in which the discharge terminal pair 180 is provided as in the illustrated example. 173 and the ground side member 175 are different in shape. On the other hand, the number of parts in both configurations is the same. Therefore, this embodiment can be regarded as a configuration in which the discharge terminal pair 180 is provided without increasing the number of parts of the grounding mechanism 170 and the safety of the fixing device 100 can be improved.

<Comparative example>
FIG. 12A is a diagram for explaining the configuration of the temperature sensor 212 of the comparative example, and FIG. 12B is a diagram for explaining the arrangement of the temperature sensor 212 of the comparative example.
Next, referring to FIG. 12, as a comparative example different from the present embodiment, unlike the above-described grounding mechanism 170, the temperature sensor 212 itself has a function of removing charges accumulated in the insulating film 101 d of the fixing roll 101. The configuration will be described.

  As shown in FIG. 12A, the temperature sensor 212 is configured as a thermistor similar to the temperature sensor 112, and has a base 212a connected to the control unit 5 via the wiring cable 214 and a pair of bases 212a extending from the base 212a. A probe 212b and a cover member 212c covering the probe 212b are provided. The probe 212b includes an exposed portion 212d that is not covered by the cover member 212c and exposed to the outside.

  The temperature sensor 212 includes a charge removal member 212e that is provided opposite to the insulating coating 101d of the fixing roll 101 and removes the electric charge of the insulating coating 101d. The charge removal member 212 e is a metal plate-like member made of, for example, aluminum, and includes a protruding piece 212 f that protrudes toward the fixing roll 101 on one side facing the fixing roll 101. The protruding piece 212f is fixed to the base 212a via a bolt 212h and grounded by a ground wire (not shown).

  Here, as shown in FIG. 12B, the tip 212 g of the protruding piece 212 f is disposed at a position away from the insulating coating 101 d of the fixing roll 101. More specifically, the distance F from the tip 212g of the protrusion 212f to the insulating coating 101d is smaller than the distance G from the exposed portion 212d of the probe 212b to the insulating coating 101d.

  The protrusions 212f flow to the ground while discharging the charges accumulated on the insulating film 101d of the fixing roll 101 to the tips 212g of the protrusions 212f. Further, as described above, the protruding piece 212f is provided at a position where the distance F from the tip 212g to the insulating coating 101d is smaller than the distance G from the exposed portion 212d of the probe 212b to the insulating coating 101d. The electric charge of 101d is suppressed from being discharged to the exposed portion 212d of the probe 212b.

Here, for example, as shown in FIG. 12A, it is assumed that a scratch 211 is formed on the insulating coating 101d. The position of the scratch 211 is smaller in the distance K to the exposed portion 212d of the probe 212b than in the distance J to the tip 212g of the protruding piece 212f. In this case, as described above, when an overcurrent due to static electricity flows to the cylindrical cored bar 101a provided inside the insulating coating 101d, the exposed portion 212d of the probe 212b and the cylindrical core through the scratch 211 of the insulating coating 101d. Discharge occurs between the gold 101a. That is, an overcurrent path that bypasses the protruding piece 212f is formed. As a result, an overcurrent flows to the control unit 5 (see FIG. 1) via the wiring cable 214 and damages the temperature sensor 212 or the control unit 5 (see FIG. 1).
Alternatively, although a detailed description is omitted, even when, for example, a plurality of fine holes (not shown) are opened in the insulating coating 101d, an overcurrent path that bypasses the protruding piece 212f is formed, and the temperature sensor 212 and the control are controlled. Part 5 can be damaged.

  On the other hand, in the above-described embodiment, unlike the comparative example, even if the insulating coating 101d is damaged at any location, or the insulating coating 101d is largely peeled off from the cylindrical metal core 101a, the discharge is performed. By flowing current to the ground via the terminal pair 180, it is possible to suppress overcurrent from flowing into the cylindrical cored bar 101a, and as a result, damage to the temperature sensor 112 and the control unit 5 (see FIG. 1) can be avoided.

<Measurement results>
FIG. 13A is a diagram for explaining the relationship between the shape of the discharge terminal pair 180 and the ease of discharge, and FIG. 13B shows the measurement result of the relationship between the shape of the discharge terminal pair 180 and the maximum discharge distance. FIG. Note that the maximum discharge distance in FIG. 13 (b) means that when a predetermined voltage is applied for discharge, discharge is possible between the first discharge terminal 181 and the second discharge terminal 183, and the first discharge is performed. This is the distance between the first discharge terminal 181 and the second discharge terminal 183 when the terminal 181 and the second discharge terminal 183 are farthest from each other. In addition, “large” in FIG. 13B means that the maximum discharge distance is relatively large, “small” means that the maximum discharge distance is relatively small, and “medium” means the intermediate distance. Indicates that

In the above description, the apex shape has been described as the first discharge terminal 181 of the discharge terminal pair 180. However, any other shape can be used as long as air discharge can be performed between the first discharge terminal 181 and the second discharge terminal 183. May be.
For example, as shown in FIG. 13A, the width (length in the left-right direction in the drawing) of the tip 281a facing the second discharge terminal 183 is longer than the corner 181a forming the acute angle of the first discharge terminal 181. The rectangular first discharge terminal 281 and the first discharge terminal having a rectangular parallelepiped shape in which the thickness of the tip 381a (the length in the depth direction in the drawing) is larger than the tip 281a and the area of the portion facing the second discharge terminal 183 is large. 381 may be used. In addition, as shown to Fig.13 (a), a rectangular parallelepiped shape, a rectangular shape, and a cusp shape have the relationship which is more difficult to discharge in this order.

Further, the tip of the corner portion 181a of the first discharge terminal 181 may be round, or a trapezoidal shape or a thin line shape whose tip width is narrower than the root width may be used. Or you may form the corner | angular part 181a of the 1st discharge terminal 181 with other members, such as a screw.
Further, although the other shape of the first discharge terminal 181 has been described here, the second discharge terminal 183 may similarly have other shapes such as a rectangular shape and a rectangular parallelepiped shape.
Further, the first discharge terminal 181 and the second discharge terminal 183 may have shapes corresponding to each other (the same shape) or different shapes.

  Now, as shown in FIG. 13B, when the maximum discharge distance is measured while changing the shape of the discharge terminal pair 180, the maximum discharge according to the shape of the first discharge terminal 181 and the second discharge terminal 183. It was confirmed that the distance changed. For example, when the first discharge terminal 181 and the second discharge terminal 183 are both sharp, the maximum discharge distance is large, and when both the first discharge terminal 181 and the second discharge terminal 183 are rectangular parallelepiped, the maximum discharge distance is small. confirmed.

Here, when the maximum discharge distance of the discharge terminal pair 180 is large, it is easy to discharge, and the discharge start voltage becomes small. On the other hand, when the maximum discharge distance of the discharge terminal pair 180 is small, it is difficult to discharge, and the discharge start voltage increases.
From this, the discharge start voltage of the discharge terminal pair 180 can be adjusted by changing the shapes of the first discharge terminal 181 and the second discharge terminal 183.

  In general, when the distance between the first discharge terminal 181 and the second discharge terminal 183 is small, the discharge start voltage decreases, and conversely, when the distance between the first discharge terminal 181 and the second discharge terminal 183 is large. Increases the discharge start voltage. Therefore, the discharge start voltage of the discharge terminal pair 180 can be adjusted by changing the distance between the first discharge terminal 181 and the second discharge terminal 183.

  Note that if the first discharge terminal 181 and the second discharge terminal 183 are both pointed, the maximum discharge distance is increased. In other words, the distance between the first discharge terminal 181 and the second discharge terminal 183 that can be discharged is wider than other shapes. Therefore, when both the first discharge terminal 181 and the second discharge terminal 183 have a cusp shape, adjustment of the discharge start voltage of the discharge terminal pair 180 becomes easier.

<Modification>
FIG. 14 is a view for explaining a grounding mechanism 270 of a modified example. FIG. 15 is a diagram for explaining a configuration example of a grounding mechanism 270 of a modified example. In the following description, a configuration different from the grounding mechanism 170 of the above-described embodiment will be mainly described, and the same members as those of the grounding mechanism 170 of the above-described embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. To do.

It has been described that the grounding mechanism 170 of the embodiment described above includes the diode 172. However, as shown in FIG. 14, the grounding mechanism 270 may be configured without the diode 172.
Specifically, the grounding mechanism 270 includes a resistor 174 and a discharge terminal pair 180. One end 174 a of the resistor 174 is grounded, and the other end 174 b is connected to the bearing 115 of the fixing roll 101. The discharge terminal pair 180 is connected in parallel with the resistor 174.

  In the illustrated example, the fixing inlet guide 111, the lever nip 131, the other end 174b of the resistor 174, the other end 180b of the discharge terminal pair 180, and the bearing 115 of the fixing roll 101 are electrically connected to each other. The Since the bearing 115 and the cylindrical cored bar 101a are electrically connected, the fixing inlet guide 111, the lever nip 131, the bearing 115 of the fixing roll 101, and the cylindrical cored bar 101a of the fixing roll 101 are connected. Are at the same potential.

Now, a specific configuration example of the grounding mechanism 270 that realizes the circuit shown in FIG. 14 will be described with reference to FIG.
First, as shown in FIG. 15, the grounding mechanism 270 includes a lever nip side member 273 and a ground side member 175, but does not include the bearing side member 171 in the above-described embodiment. Further, the lever nip side member 273 includes a bearing connection portion 173g connected to the bearing 115 of the fixing roll 101, but does not include the first connection portion 173b connected to the diode 172 in the above-described embodiment.
Since the lever nip side member 273 includes the bearing connecting portion 173g, the fixing inlet guide 111, the lever nip 131, the bearing 115 of the fixing roll 101, and the cylindrical cored bar 101a of the fixing roll 101 have the same potential.

  Since the grounding mechanism 270 does not include the diode 172 and the bearing side member 171 in the grounding mechanism 170 described above, the grounding mechanism 270 has a simpler configuration than the grounding mechanism 170. The grounding mechanism 270 can ground the fixing roll 101 and its peripheral members while avoiding damage to the temperature sensor 112 and the control unit 5 (see FIG. 1).

  In the above description, the fixing device 100 is described as including the temperature sensor 112, but the image forming apparatus 1 may include the temperature sensor 112 instead of the fixing device 100. That is, even when the fixing device 100 that does not include the temperature sensor 112 is attached to the image forming apparatus 1, the temperature sensor 112 provided on the image forming apparatus 1 side may come into contact with the fixing roll 101. Good.

  In the above description, it has been described that the overcurrent flowing through the temperature sensor 112 provided in contact with the fixing roll 101 is suppressed. However, the temperature sensor 112 is positioned away from the fixing roll 112. Of course, a non-contact temperature sensor provided opposite to the above may be used. Alternatively, the temperature sensor 112 may be another sensor such as an infrared sensor that detects the passage of a sheet as long as the sensor is provided in contact with or opposed to the outer peripheral surface of the fixing roll 101.

  In the above description, it has been described that the conducting member 115c conducts the bearing inner ring 115a and the bearing outer ring 115b. However, as long as the bearing 115 has a function of electrically connecting the diode 172 and the cylindrical cored bar 101a, it is of course possible to have another configuration not including the conducting member 115c.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 5 ... Control part, 100 ... Fixing device, 101 ... Fixing roll, 103 ... Pressure belt, 112 ... Temperature sensor, 115 ... Bearing, 131 ... Lever nip, 150 ... Release lever, 170 ... Grounding mechanism, 180 ... discharge terminal pair

Claims (6)

A rotatable rotary member, a fixing member to which the and lower conductivity than the rotating member and an outer peripheral member that is provided on the outer periphery of the rotary member, thereby fixing the toner on the recording material,
Detecting means for detecting the state of the outer peripheral member;
A first discharge member electrically connected to the rotating member;
The grounded provided et al is in a position spaced apart from the first discharge member, and a second discharge member Ru receive charge from the first discharge member by discharge,
Between the rotating member and the first discharge member, an anode is electrically connected to the rotating member side, and a cathode is connected to the first discharging member side;
Ru with a constant Chakusochi. One end electrically connected between the first discharge member and the diode, the fixing device of 請 Motomeko 1, wherein the other end Ru comprises a resistive element is grounded. The detection means, the addition to measuring the temperature of the provided the outer peripheral member in contact with the outer peripheral member, 請 Motomeko 1 Ru provided with a temperature sensor to send a signal related to the temperature to a control board connected via a signal line or 3. The fixing device according to 2. The first discharge member includes a first corner protruding toward the second discharge member,
The second discharge member includes a second corner portion protruding toward the first corner portion of the first discharge member ,
Wherein the first discharge member and the second discharge member, the fixing device according to any one of 請 Motomeko 1 to 3 is arranged in a direction in which each side intersect each other. A rotatable rotary member, a fixing member to which the and lower conductivity than the rotating member and an outer peripheral member that is provided on the outer periphery of the rotary member, thereby fixing the toner on the recording material,
Detecting means for detecting the state of the outer peripheral member;
The rotating member and is electrically connected, when the predetermined voltage is applied to the rotary member, and discharge means for the gaseous discharge current flows from the rotary member side to the ground,
Between the rotating member and the discharging unit, an anode is connected to the rotating member side, and a cathode is connected to the discharging unit side;
Ru with a constant Chakusochi. A toner image forming unit for forming a toner image on a recording material;
A rotatable rotary member, and a peripheral member of conductivity than the rotary member is provided on the outer periphery of the lower and the rotary member, thereby fixing the toner image formed by the toner image forming unit on the recording material fixing Members,
Detecting means for detecting the state of the outer peripheral member;
A first discharge member electrically connected to the rotating member;
The grounded provided et al is in a position spaced apart from the first discharge member, and a second discharge member Ru receive charge from the first discharge member by discharge,
Between the rotating member and the first discharge member, an anode is connected to the rotating member side, and a cathode is connected to the first discharging member side;
Images forming apparatus Ru comprising a.

Images