JP5409157B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device (fixing device) mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  As a fixing device (fixing device) mounted on an electrophotographic copying machine or printer, having a fixing roller, a heater for heating the fixing roller, and a pressure roller that forms a nip portion in contact with the fixing roller It has been known. The recording material carrying the unfixed toner image is heated while being nipped and conveyed at the nip portion, whereby the toner image on the recording material is heated and fixed to the recording material. Among the fixing devices, from the viewpoint of improving productivity and image quality, belt-type fixing devices in which one or both of the fixing roller and the pressure roller are replaced with a belt have become mainstream. In the belt-type fixing device, the belt is stretched around a plurality of rollers. In the fixing device, a fixing inlet guide is provided on the upstream side of the nip portion in the recording material conveyance direction, and a recording material carrying a toner image is introduced into the nip portion by the fixing inlet guide.

JP 2004-341346 A

  The rollers and belts used in the above-mentioned fixing device are parts that are regularly replaced by a service person because their durable lives are determined. Therefore, in the fixing device, in addition to the above-described improvements in productivity and image quality, it is desired to improve the workability of parts replacement by service personnel. For example, in the case of a belt-type fixing device, a serviceman replaces one unit having a belt and a plurality of rollers around the belt with a new unit. In order to stably introduce the recording material into the fixing nip portion, it is preferable that the tip of the fixing inlet guide on the nip portion side is close to the nip portion. However, if the front end of the fixing inlet guide is close to the nip portion, the path drawn when the pressure unit is replaced when the pressure unit having a roller or belt is replaced with a new pressure unit is fixed. It crossed the guide, preventing the replacement of the pressure unit. In particular, in the case of a belt-type fixing device, this tendency is remarkable because the space occupied by the belt tends to expand in the recording material conveyance direction. SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus capable of satisfying both the stabilization of introduction of a recording material into a nip portion by a guide and the replacement of a pressure unit without interfering with the guide.

In order to achieve the above object, an image heating apparatus according to the present invention includes a heating unit having a heating rotator, and a pressure unit having a pressure rotator that contacts the heating rotator to form a nip portion. In the image heating apparatus that heats the recording material carrying the image at the nip portion while nipping and conveying, a frame that removably supports the pressure unit, and a guide for introducing the recording material into the nip portion. Yes , the downstream end of the guide in the recording material conveyance direction overlaps the upstream end of the pressure rotation body in the recording material conveyance direction in the projection area of the pressure rotator as viewed from the direction in which the pressure unit is removed. recording material introducing position, the guide of the recording material conveyance direction downstream in the projection region of the SL before the pressurizing unit when detached from the frame pressurizing rotator when introducing the recording material to the nip Te A guide end portion is supported to be displaceable in the frame in two positions, a retracted position retracted from said projection area so as not to overlap with the recording material conveying direction upstream side end portion of the pressure rotating body, And a detection member that detects that the guide introduces the recording material into the nip portion and detects that the guide is displaced to the retracted position .

  According to the present invention, it is possible to provide an image heating apparatus that can achieve both the stabilization of the introduction of the recording material into the nip portion by the guide and the replacement of the pressure unit without interfering with the guide.

1 is a schematic configuration diagram of an example of an image forming apparatus. FIG. (A) is a front view of the fixing device viewed from the upstream side in the recording material conveyance direction, and (b) is an enlarged sectional view taken along line AA in (a). (A) is the side view which looked at the fixing entrance guide unit from the longitudinal direction one end part side. FIG. 4B is a cross-sectional view of the fixing entrance guide unit taken along line AA in FIG. FIG. 6C is a cross-sectional view of the fixing entrance guide unit showing the relationship between the fixing sensor flag and the photosensor. FIG. 6D is a cross-sectional view of the fixing inlet guide unit representing the fixing inlet guide at the recording material introduction position. FIG. 6E is a cross-sectional view of the fixing inlet guide unit showing the fixing inlet guide in the retracted position. FIG. 4 is an explanatory diagram when the fixing device is attached to and detached from the image forming apparatus main body. 3A is a cross-sectional view of the pressure unit and the fixing inlet guide unit along line AA in FIG. 3A before removing the pressure unit, and the pressure unit and the fixing inlet guide unit are shown in FIG. The top view seen from the top. FIG. 3B is a cross-sectional view of the pressure unit and the fixing inlet guide unit along line AA in FIG. 3A when the pressure unit is removed, and FIG. 3A shows the pressure unit and the fixing inlet guide unit. The top view seen from the top. FIG. 4C is a cross-sectional view of the pressure unit and the fixing inlet guide unit along line AA in FIG. 3A after the pressure unit is removed.

(1) Description of the entire image forming apparatus: FIG. 1 is a schematic diagram of an example of an image forming apparatus in which the image heating apparatus according to the present invention is mounted as a fixing device. This image forming apparatus is a multi-function printer (multifunction printer) having a copier function, a printer function, and a facsimile function. The image forming apparatus according to the first exemplary embodiment has an image forming unit Py for forming toner images of four colors of yellow, magenta, cyan, and black inside an image forming apparatus main body 100 that constitutes a housing of the image forming apparatus. , Pm, Pc, Pb are arranged in series. A tandem method is employed in which a series of processes of charging, exposure, development, and primary transfer are performed in parallel for each color by the image forming portions Py, Pm, Pc, and Pb. Reference numeral 160 denotes a document feeder, and 161 is a reader scanner unit that reads an image of a document fed from the document feeder 160. In the first embodiment, only the printer function of the image forming apparatus will be described in order to simplify the description.
The image forming apparatus according to the first exemplary embodiment starts an image forming operation according to a predetermined image forming sequence in response to a print command output from an external apparatus (not shown) such as a host computer. That is, the image forming units Py, Pm, Pc, and Pb are sequentially driven, and a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image carrier is moved to a predetermined peripheral speed (process speed) in an arrow direction. ). The intermediate transfer belt 5 spanned between the driving roller 6a, the driven roller 6b, and the tension roller 6c so as to straddle the photosensitive drums 1 of the respective image forming portions Py, Pm, Pc, Pb is driven by the driving roller 6a. And rotated at a peripheral speed corresponding to the rotational peripheral speed. First, in the first color yellow image forming portion Py, the outer peripheral surface (surface) of the photosensitive drum 1 is uniformly charged by the charger 2 to a predetermined polarity and potential. Next, the exposure device 3 scans and exposes the charged surface of the surface of the photosensitive drum 1 with laser light corresponding to the image information from the external device. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 1. The latent image is developed by the developing device 4 using yellow toner (developer), and a yellow toner image (developed image) is formed on the surface of the photosensitive drum 1. The same steps of charging, exposure, and development are also performed in the second color magenta image forming portion Pm, the third color cyan image forming portion Pc, and the fourth color black image forming portion Pb. Each color toner image formed on the surface of the photosensitive drum 1 in each of the image forming portions Py, Pm, Pc, and Pb is intermediated by a primary transfer roller 7 disposed opposite to the photosensitive drum 1 with the intermediate transfer belt 5 interposed therebetween. The images are sequentially transferred onto the outer peripheral surface (front surface) of the transfer belt 5. On the other hand, the recording material P is fed from the feeding cassette 10 by the feeding roller 11 to the registration roller 13 through the sheet path 12. Next, the recording material P is conveyed by the registration roller 13 to the secondary transfer nip portion between the intermediate transfer belt 5 and the secondary transfer roller (transfer member) 14. The recording material P is nipped and conveyed by the intermediate transfer belt 5 and the secondary transfer roller 14, and the full-color toner image on the surface of the intermediate transfer belt 5 is transferred onto the surface of the recording material P by the secondary transfer roller 14 in the conveyance process. Is done. The recording material P carrying a full-color unfixed toner image is introduced into the fixing device 15. The recording material P is nipped and conveyed at a fixing nip portion described later, whereby an unfixed toner image is heated and fixed on the recording material P. In the single-sided image forming mode, the recording material P exiting the fixing device 15 is discharged to a discharge tray 16 outside the image forming device. In the duplex printing mode, the recording material P that has exited the fixing device 15 is introduced into the switchback sheet 17 of the recirculation conveyance mechanism by a flapper (not shown). Then, the recording material P is pulled out from the switchback sheet 17 and introduced into the re-conveying path 18. The recording material P passes through the sheet path 12 and the registration roller 13 from the re-conveying path 18 and is turned into the secondary transfer nip portion in a state where the front and back are reversed It is re-introduced at the transport timing. As a result, the secondary transfer of the toner image on the surface of the intermediate transfer belt 5 is performed on the second surface of the recording material P. The recording material P is reintroduced into the fixing device 15, and the toner image is heated and fixed at the fixing nip portion and discharged to the discharge tray 16. Note that the order and configuration of the image forming units Py, Pm, Pc, and Pk are not limited to this. In a monochrome image forming apparatus, only a black image forming unit exists.

  (2) Description of fixing device: In the following description, regarding the fixing device and the members constituting the fixing device, the longitudinal direction is a direction perpendicular to the recording material conveyance direction on the surface of the recording material. The short side direction is a direction parallel to the recording material conveyance direction on the surface of the recording material. The width is a dimension in the short direction. FIG. 2 is an exploded perspective view of the fixing device. 3A is a front view of the fixing device as viewed from the upstream side in the recording material conveyance direction, and FIG. 3B is an enlarged cross-sectional view taken along line AA in FIG. FIG. 4A is a side view of the fixing entrance guide unit as viewed from one end in the longitudinal direction. FIG. 4B is a cross-sectional view of the fixing inlet guide unit taken along line AA in FIG. FIG. 6C is a cross-sectional view of the fixing entrance guide unit showing the relationship between the fixing sensor flag and the photosensor. FIG. 6D is a cross-sectional view of the fixing inlet guide unit representing the fixing inlet guide at the recording material introduction position. FIG. 6E is a cross-sectional view of the fixing inlet guide unit representing the fixing inlet guide in the retracted position.

(2-1) Description of Entire Fixing Device The fixing device 15 shown in the first embodiment includes a pressure unit 20, a fixing unit (heating unit) 40, a fixing inlet guide unit 50, a pressure unit 20, and a fixing unit. 40 and a fixing frame (frame) 60 that supports the fixing inlet guide unit 50. The fixing frame 60 includes a bottom plate portion 61, a support frame portion 62 a provided on one end side in the longitudinal direction of the bottom plate portion 61 (left side in FIG. 2), and the other end portion in the longitudinal direction of the bottom plate portion 61 (see FIG. 2). And a support frame portion 62b provided on the right side). The support frame portion (hereinafter referred to as the left support frame portion) 62a and the support frame portion (hereinafter referred to as the right support frame portion) 62b are opposed to each other in the longitudinal direction of the bottom plate portion 61, and from the bottom plate portion 61, respectively. A pair of support plates 62a1 and 62b1 projecting upward is provided. Of the pair of support plates 62a1 of the left support frame portion 62a and the pair of support plates 62b1 of the right support frame portion 62b, the outer support plates 62a1 and 62b1 are arranged along the longitudinal direction of the bottom plate portion 61. Both end portions in the longitudinal direction of 65 (FIG. 3B) are rotatably supported. Pressure cams 66a and 66b are eccentrically attached to the cam shaft 65 so as to be positioned between the pair of support plates 62a1 of the left support frame portion 62a and between the pair of support plates 62b1 of the right support frame portion 62b. is there.

  The pressure unit 20 includes a long endless pressure belt (pressure rotator) 23 disposed along the longitudinal direction of the bottom plate portion 61 of the fixing frame 60. The pressure belt 23 has a pressure frame 21a on one end side in the longitudinal direction (left side in FIG. 2) and a pressure frame 21b on the other end side in the longitudinal direction (right side in FIG. 2). The pressure frame (hereinafter referred to as the left pressure frame) 21a is fitted between a pair of support plates 62a1 of the left support frame portion 62a of the fixing frame 60 so as to be movable up and down, and the lower surface of the left pressure frame 21a It is in contact with the outer peripheral surface of the pressure cam 66a. Similarly, the pressure frame (hereinafter referred to as the right pressure frame) 21b is fitted between the pair of support plates 62a1 of the right support frame portion 62b of the fixing frame 60 so as to be movable up and down, and the right pressure frame 21b. Is in contact with the outer peripheral surface of the pressure cam 66b. The pressurizing unit 20 has rotation center portions 22a and 22b at the other ends in the short direction (downstream end in the recording material conveyance direction) of the left pressurizing frame 21a and the right pressurizing frame 21b, respectively. And provided in the vicinity of the upper part of the pair of support plates 62a1 of the hole 22a1 of the rotation center portion 22a of the left pressurizing frame 21a and the other end portion in the short side direction (the downstream end portion in the recording material conveyance direction) of the left support frame portion 62a. The holes 68a are aligned so as to communicate with each other. Further, it is provided in the vicinity of the upper portion of the pair of support plates 62b1 at the hole 22b1 of the rotation center portion 22b of the right pressure frame 21b and one end portion in the short direction (upstream end portion in the recording material conveyance direction) of the right support frame portion 62b. The holes 68b are aligned so as to communicate with each other. Then, a rotation pin 64a is inserted into the hole 22a1 of the rotation center portion 22a of the left pressure frame 21a and the hole 68a of the pair of support plates 62a1, and a pair of holes 22b1 of the rotation center portion 22b of the right pressure frame 21b are paired. A rotation pin 64b is inserted into the hole 68b of the support plate 62b1. Thereby, the rotation center part 22a of the left pressure frame 21a is rotatably supported by the pair of support plates 62a1 via the rotation pins 64a, and the rotation center part 22b of the right pressure frame 21b is a pair of support plates. 62b1 is rotatably supported via a rotation pin 64b. Accordingly, the pressure unit 20 can be rotated clockwise and counterclockwise around the rotation pins 64a and 64b with respect to the left support frame portion 62a and the right support frame portion 62b of the fixing frame 60.

  The fixing inlet guide unit 50 includes a fixing inlet guide support member 51 fixed to a support member 63 provided at one end portion in the short side direction (upstream end portion in the recording material conveyance direction) of the bottom plate portion 61 of the fixing frame 60. Have. The fixing inlet guide support member 51 is a long member disposed along the longitudinal direction of the pressure belt 23 between the left pressure frame 21 a and the right pressure frame 21 b of the pressure unit 20. A plurality of support portions 51 a (FIG. 2) are provided along the longitudinal direction of the fixing entrance guide support member 51 on the surface of the fixing entrance guide support member 51 on one end side in the short direction. Then, one end portion in the short direction (upstream end portion in the recording material conveyance direction) of the long fixing inlet guide (guide) 52 arranged along the longitudinal direction of the pressure belt 23 of the pressure unit 20 by the plurality of support portions 51a. ) Is rotatably supported. The fixing inlet guide 52 and the fixing inlet guide support member 51 are connected to each other at two predetermined locations in the longitudinal direction by an inlet guide biasing spring 53 (FIG. 2). The inlet guide biasing spring 53 biases the fixing inlet guide 52 so as to rotate toward the lower pressure belt 23 with the support portion 51a as a fulcrum. On the back surface of the fixing entrance guide 52, a protrusion 52a (FIG. 4A) is provided at a predetermined location. The protrusion 52 a is brought into contact with a protrusion 51 b provided on the other end side in the short side direction of the fixing inlet guide support member 51 to stop the fixing inlet guide 52 at a predetermined position above the pressure belt 23. (FIG. 4A). The position at which the fixing inlet guide 52 stops is a recording material introduction position when the fixing inlet guide 52 introduces the recording material P into a fixing nip portion N which will be described later (FIG. 4D). The fixing inlet guide 52 has the other end in the short direction (downstream end in the recording material conveyance direction) 52o of the fixing inlet guide 52 at the recording material introduction position. It overlaps with a predetermined width W (FIG. 3 (b)) on the upstream end in the conveying direction) 23i. In this way, by adopting a configuration in which the other end 52o in the short direction of the fixing inlet guide 52 and the one end 23i in the short direction of the pressure belt 23 are overlapped, the other end 52o in the short direction of the fixing inlet guide 52 is formed. It is possible to approach the fixing nip portion N. Thus, there is an advantage that the recording material P can be stably introduced into the fixing nip N by the fixing inlet guide 52.

  The fixing unit 40 includes a long endless fixing belt (heating rotator) 43 (FIG. 3B) disposed along the longitudinal direction of the pressure belt 23 of the pressure unit 20, and the longitudinal direction of the fixing belt 43. And a long heating member 46 arranged along the line. The fixing unit 40 has a long fixing unit cover 47 arranged along the longitudinal direction of the fixing belt 43 on the other end side in the short side direction of the heating member 46 (downstream side in the recording material conveyance direction). The fixing unit cover 47 has a fixing frame 41a on one end in the longitudinal direction (left side in FIG. 2) and a fixing frame 41b on the other end in the longitudinal direction (right side in FIG. 2). One end in the short direction (the upstream end in the recording material conveyance direction) of the left fixing frame (hereinafter referred to as the left fixing frame) 41a and the right fixing frame (hereinafter referred to as the right fixing frame) 41b includes: Pins 42 a and 42 b that are slidable in the longitudinal direction of the heating member 46 are provided. Similarly, pins 42c and 42d that are slidable in the longitudinal direction of the heating member 46 are also provided on the other side of the left fixing frame 41a and the right fixing frame 41b in the short side direction (downstream side end in the recording material conveyance direction). is there. Then, the pins 42a and 42b are locked in the holes 69a and 69b provided on the upper side of the one end side in the short direction in the outer support plates 62a1 and 62b1 of the left support frame portion 62a and the right support frame portion 62b of the fixing frame 60. I am letting. Then, the pins 42c and 42d are engaged with the holes 69c and 69d provided on the upper side of the other end side in the short direction in the outer support plates 62a1 and 62b1 of the left support frame portion 62a and the right support frame portion 62b of the fixing frame 60. It is stopped. Therefore, the fixing unit 40 is placed on the left support frame 62a and the right support frame 62b above the pressure unit rotatably supported by the left support frame 62a and the right support frame 62b of the fixing frame 60. It is fixedly supported by pins 42a to 42d.

  (2-2) Description of Pressure Unit: In the pressure unit 20, the pressure belt 23 is stretched between both the pressure roller 24 and the pressure tension roller 25. As the pressure belt 23, a belt that is heated by a halogen heater 29 described later via a pressure roller 24 and has heat resistance is used. In the first embodiment, a predetermined endless metal layer having a thermal conductivity of, for example, a thickness of 75 μm, a width of 380 mm, and a circumferential length of 200 mm is used as the base layer of the pressure belt 23. On the outer peripheral surface of the metal layer, silicon rubber having a thickness of, for example, 400 μm is coated as an elastic layer, and on the outer peripheral surface of the silicon rubber, a PFA tube is covered as a release layer. The pressure roller 24 is an elongated stainless steel (SUS) hollow roller formed to have an outer diameter φ20 and an inner diameter φ18, for example, and the other end side in the short direction of the left pressure frame 21a and the right pressure frame 21b. Is arranged. The both ends in the longitudinal direction of the pressure roller 24 are rotatably supported by the left pressure frame 21a and the right pressure frame 21b. The pressure tension roller 25 is a stainless steel hollow roller having an outer diameter of about 20 mm and an inner diameter of about 18 as with the pressure roller 24, for example, and functions as a roller that applies an appropriate tension to the pressure belt 23. Then, both ends in the longitudinal direction of the pressure tension roller 25 are connected to one end side in the short direction (downstream in the recording material conveyance direction) of the left pressure frame 21a and the right pressure frame 21b (FIG. 2) via bearings (not shown). It is supported so that it can be displaced. The bearings are biased by tension biasing springs 28a and 28b (FIG. 2) toward the other end side in the short side direction (upstream side in the recording material conveyance direction) of the left pressure frame 21a and the right pressure frame 21b. . As a result, the pressure tension roller 25 constantly pressurizes the inner surface of the pressure belt 23 with an optimum tension, for example, about 100N. Inside the pressure roller 24, a halogen lamp (hereinafter referred to as a heater) 29 is provided as a heating element. The heater 29 is supported by a left pressurizing frame 21a and a right pressurizing frame 21b at caps (not shown) provided at both longitudinal ends of the heater 29. The pressure roller 24 is heated from the inside by the radiant heat of the heater 29, and the pressure belt 23 is heated by utilizing the heat conduction of the pressure roller 24. The heating element is not limited to a halogen lamp, and any other heating element may be used as long as it can be used as a heat source.

  Inside the pressure belt 23, a pressure pad 27 is provided in the vicinity of the pressure roller 24 and an oil application roller 26 is provided in the vicinity of the pressure tension roller 25. The oil application roller 26 is disposed between the pressure tension roller 25 and the pressure pad 27 so as to be in contact with the inner peripheral surface (inner surface) of the pressure belt 23. The oil application roller 26 has a heat-resistant aramid felt impregnated with heat-resistant silicone oil having a viscosity of about 1000 CS. Silicone oil is supplied to the inner surface of the pressure belt 23 from a sheet-like oil application control film made of a porous PTFE layer provided on the surface layer of the heat-resistant aramid felt. The pressure pad 27 is positioned at the recording material inlet side of the fixing nip portion N formed between the pressure belt 23 and the fixing belt 43, that is, at the upstream side of the pressure roller 24 of the fixing nip portion N in the recording material conveyance direction. It is provided inside the corresponding pressure belt 23. The pressure pad 27 is formed of, for example, silicon rubber, and is provided on a long pressure pad support member 30 disposed along the longitudinal direction of the pressure roller 24. Then, both end portions in the longitudinal direction of the pressure pad support member 30 are supported by the second support members 31a and 31b (FIG. 2). Of the second support members 31a and 31b, the second support member 31a is swingably supported on the other side in the short direction of the left pressure frame 21a, and the second support member 31b is supported by the right pressure frame 21b. It is supported at the other end in the short direction so as to be swingable. A pressurizing screw 32a is inserted from above into one end of the second support member 31a on the left pressurizing frame 21a side (downstream end in the recording material conveyance direction), and a pressurizing spring is applied to the pressurizing screw 32a. 33a is mounted in a reduced size. The tip of the pressure adjusting screw 32a is screwed into the left pressure frame 21a. Similarly, the pressure adjusting screw 32b is inserted from above into the one end in the short direction (downstream end in the recording material conveyance direction) of the second support member 31b on the right pressurizing frame 21b side, and applied to the pressure adjusting screw 32b. The pressure spring 33b is contracted and attached. The tip of the pressure adjusting screw 32b is screwed into the right pressurizing frame 21b. The amount of compression of the pressure springs 33a and 33b is adjusted by appropriately adjusting the screwing amounts of the two pressure adjusting screws 32a and 32b, and the pressure applied to the inner surface of the pressure belt 23 by the pressure pad 27 is optimized. I have to. In the first embodiment, the pressure pad 27 is urged toward the inner surface of the pressure belt 23 with a set pressure of about 400 N, for example.

  (2-3) Description of Fixing Unit: In the fixing unit 40, the fixing belt 43 is stretched over both the fixing roller 44 and the fixing tension roller 45. As the fixing belt 43, a belt that generates heat by a magnetic flux generated from a coil 46 b included in an electromagnetic induction heating member 46 described later and has heat resistance is used. In the first embodiment, an endless magnetic metal layer such as a nickel metal layer or a stainless steel layer having a thickness of 75 μm, a width of 380 mm, and a circumferential length of 200 mm is used as the base layer of the fixing belt 43. On the outer peripheral surface of the magnetic metal layer, for example, 400 μm thick silicon rubber is coated as an elastic layer, and on the outer peripheral surface of the silicon rubber, a PFA tube is coated as a release layer. The electromagnetic induction heating member 46 (FIG. 2) includes a magnetic core 46a disposed along the longitudinal direction of the fixing belt 43 on the side of the pressure tension roller 45, and the magnetic core 46a. And a coil 46b wound in the longitudinal direction. The magnetic core 46a and the coil 46b are supported by the heat resistant holder 46c so as to face the surface of the fixing belt 43. The other end in the short direction (recording material discharge side) of the heat-resistant holder 46c is one end in the short direction (recording) of the long fixing unit cover 47 arranged along the longitudinal direction of the fixing belt 43 on the fixing roller 44 side. It is supported on the downstream side in the material conveyance direction (FIG. 3B).

  The fixing roller 44 is formed, for example, by integrally forming heat-resistant silicon rubber as an elastic layer on the outer peripheral surface of an elongated stainless steel roller having an outer diameter of φ18. The fixing roller 44 is disposed on the other end side in the lateral direction of the left fixing frame 41a and the right fixing frame 41b. Both ends of the fixing roller 44 in the longitudinal direction are rotatably supported by the left fixing frame 41a and the right fixing frame 41b. The fixing tension roller 45 is a stainless steel hollow roller having an outer diameter φ20 and an inner diameter φ18, for example. Then, both ends in the longitudinal direction of the fixing tension roller 45 are supported on one end side in the short direction of the left pressure frame 21a and the right pressure frame 21b via bearings (not shown). The fixing tension roller 45 applies, for example, a tension set to 120 N to the inner peripheral surface (inner surface) of the 45 fixing belt 43 in order to keep the tension of the fixing belt 43 optimal at all times.

  Inside the fixing belt 43, for example, a fixing pad stay 48 made of stainless steel is provided in the vicinity of the fixing roller 44. The fixing pad stay 48 is arranged in a state of being urged so as to contact the inner surface of the fixing belt 43 at a position facing the pressure pad 27 of the pressure unit 20.

  (2-4) Description of Fixing Entrance Guide Unit: In the fixing entrance guide unit 50, the fixing entrance guide 52 has an opening 52 b (FIG. 2) substantially at the center in the longitudinal direction of the fixing entrance guide 52. An elongated bar-shaped fixing entrance sensor flag (detection member) 54 is disposed in the opening 52b (FIG. 4B). The fixing inlet sensor flag 54 is rotatably supported by a fixing inlet guide support member 51 by a shaft 55 at a boss portion 54a provided at the tip of a portion below the opening 52b of the fixing inlet guide 52 ( FIG. 4 (b)). The fixing inlet sensor flag 54 is provided with a sensor flag biasing spring (not shown) so that a portion above the opening 52b of the fixing inlet guide 52 protrudes from the surface of the fixing inlet guide 52 with a predetermined angle by a predetermined amount. It is held by power. The fixing inlet guide support member 51 includes a light emitting portion 56 a and a light receiving portion (not shown) arranged to face each other so as to sandwich the boss portion 54 a of the fixing inlet sensor flag 54 in the longitudinal direction of the fixing inlet guide support member 51. A photosensor 56 is provided (FIG. 4C). A first light shielding member 57a and a second light shielding member 57b are provided on the outer peripheral surface of the boss portion 54a of the fixing entrance sensor flag 54 (FIG. 4C).

  (2-5) Description of Fixing Device Attachment / Removal Operation: The fixing device 15 shown in the first embodiment is detachably attached to the image forming apparatus main body 100. FIG. 5 is an explanatory diagram when the fixing device is attached to and detached from the image forming apparatus main body.

  When the fixing device 15 is mounted on the image forming apparatus main body 100, first, a predetermined opening / closing cover (not shown) of the image forming apparatus main body 100 is opened. Next, the fixing device 15 is set to a predetermined support mechanism (not shown) provided in the image forming apparatus main body 100 from the other end in the longitudinal direction of the fixing device 15 (left side in FIG. 3A). The fixing device 15 is pushed in the longitudinal direction and stored in the image forming apparatus main body 100. Then, a cam gear 67 (FIG. 2) provided at the other longitudinal end of the cam shaft 65 of the fixing frame 60 meshes with a main body drive cam gear (not shown) on the image forming apparatus main body 100 side, and the image forming apparatus main body 100 side. The cam shaft 65 can be rotated by a cam motor (not shown). A driving gear 49 (FIG. 2) provided at one end portion of the fixing roller 44 in the longitudinal direction of the fixing unit 40 meshes with a main body driving gear (not shown) on the image forming apparatus main body 100 side, and on the image forming apparatus main body 100 side. The fixing roller 44 can be rotated by a fixing motor (not shown). Further, a heater power supply terminal (not shown) disposed at a predetermined position of the pressurizing unit 20 is in electrical contact with a heater main body power supply terminal (not shown) on the image forming apparatus main body 100 side. Power can be supplied to the heater 29 from a main body energization control circuit (not shown) on the main body 100 side. Further, a coil power supply terminal disposed at a predetermined position of the fixing unit 40 is in electrical contact with a coil main body power supply terminal (not shown) on the image forming apparatus main body 100 side, and is heated by the main body energization control circuit. Power can be supplied to the coil 46b of the member 46. Then, by closing the opening / closing cover, the mounting of the fixing device 15 to the image forming apparatus main body 100 is completed. Finally, by performing a predetermined operation, the cam motor is driven to rotate forward to rotate the cam shaft 65 by a predetermined amount, and the left pressure frame 21a and the right pressure frame of the pressure unit 20 on the outer peripheral surfaces of the pressure cams 66a and 66b. The lower surface of the one end portion side of 21b is pushed up. As a result, the pressurizing unit 20 rotates a predetermined amount in the counterclockwise direction around the rotation pins 64a and 64b of the rotation center portions 22a and 22b. As the pressure unit 20 rotates, the pressure roller 24 presses the pressure belt 23 to the fixing roller 44 via the fixing belt 43, and the pressure pad 27 moves the pressure belt 23 to the fixing belt 43. Through the pressure pad stay 48. As a result, the surface of the pressure belt 23 is pressed against the pressure pad stay 48 via the fixing belt 43 by the pressure pad 27 from the position where the pressure roller 24 presses the fixing roller 44 via the fixing belt 43. The surface of the fixing belt 43 is brought into contact with the pressure state until the position reaches the position. As a result, a fixing nip N having a predetermined width is formed between the surface of the pressure belt 23 and the surface of the fixing belt 43 (FIG. 3B).

  When the fixing device 15 is removed from the image forming apparatus main body 100, first, a predetermined operation is performed to drive the cam motor in the reverse direction to rotate the cam shaft 65 by a predetermined amount. As a result, the pressure unit 20 rotates in a state in which the lower surfaces of the left pressure frame 21a and the right pressure frame 21b of the pressure unit 20 on one end side in the short direction and the outer peripheral surfaces of the pressure cams 66a and 66b are in contact with each other. The pins 64a and 64b are rotated clockwise by a predetermined amount and returned to their original positions. Next, the opening / closing cover of the image forming apparatus main body 100 is opened. Then, the fixing device 15 is pulled out from the inside of the image forming apparatus main body 100 in the longitudinal direction from one end portion side in the longitudinal direction of the fixing device 15 (right side in FIG. 3A). Thereby, the removal of the fixing device 15 from the image forming apparatus main body 100 is completed.

  (2-6) Description of Heat Fixing Operation of Fixing Device: In the fixing device 15 of the first embodiment, the fixing roller 44 is moved as shown in FIG. It is rotated at a predetermined peripheral speed in the direction of the arrow shown in (b). When the fixing roller 44 rotates, the rotation of the fixing roller 44 is transmitted to the fixing belt 43 at the fixing nip portion P, and the fixing belt 43 rotates around the fixing roller 44 and the fixing tension roller 45 in the direction of the arrow as the fixing roller 44 rotates. Move around. The rotation of the fixing belt 43 is transmitted to the fixing tension roller 45, and the fixing tension roller 45 is driven to rotate in the direction of the arrow as the fixing belt 43 rotates. Further, the rotation of the fixing belt 43 is transmitted to the surface of the pressure belt 23 at the fixing nip portion N, and the pressure belt 23 moves around the pressure roller 24 and the pressure tension roller 25 as the fixing belt 43 rotates. 43 and moves in the direction of the arrow at the same speed. The rotation of the pressure belt 23 is transmitted to the pressure roller 24 and the pressure tension roller 25, and the pressure roller 24 and the pressure tension roller 25 are driven to rotate in the direction of the arrow as the pressure belt 23 rotates.

  The heater 29 and the coil 46b of the heating member 46 are energized with an alternating current by the main body energization control circuit before or after the rotation of the fixing roller 44 or simultaneously. When an alternating current is passed through the coil 46 b, a magnetic line of force is generated around the coil and an eddy current is generated in the magnetic metal layer of the fixing belt 43. This eddy current changes to Joule heat due to the resistance of the magnetic metal layer, causing the magnetic metal layer to generate heat. As a result, the fixing belt 43 that is rotating is heated. The temperature of the fixing belt 43 is detected by a temperature detection element (not shown) disposed in the vicinity of the fixing belt 43. The main body energization control circuit controls the power supplied to the coil 46b based on the output signal from the temperature detecting element so as to maintain the fixing belt 43 at a predetermined temperature (target temperature). In the first embodiment, the predetermined temperature of the fixing belt 43 is maintained at about 180 ° C. Further, when an alternating current is applied to the heater 29, the heater 29 generates heat, the heater 29 heats the pressure roller 24 that is rotating, and the pressure roller 24 heats the pressure belt 23 that is rotating. The temperature of the pressure belt 23 is detected by a temperature detection element (not shown) disposed in the vicinity of the pressure belt 23. The main body energization control circuit controls the power supplied to the heater 29 based on the output signal from the temperature detection element so as to maintain the pressure belt 23 at a predetermined temperature (target temperature). In the first embodiment, the predetermined temperature of the pressure belt 23 is maintained at about 100 ° C.

  In a state where the fixing belt 43 and the pressure belt 23 are rotated and the fixing belt 43 and the pressure belt 23 are maintained at a predetermined temperature, the recording material P carrying the unfixed toner image t changes the toner image carrying surface. It is conveyed upward and onto the fixing entrance guide 52 (FIG. 3B). The recording material P pushes down the fixing inlet sensor flag 54 at the front end of the recording material P against the biasing force of the above-described sensor flag biasing spring, and the fixing inlet sensor flag 54 rotates downward with the shaft 55 as a fulcrum. Then, it enters into the opening 52b of the fixing entrance guide 52 (FIG. 4D). The first light shielding member 57a rotates about the shaft 55 together with the fixing entrance sensor flag 54, and the first light shielding member 57a shields the light beam emitted from the light emitting portion 56a of the photosensor 56 to the light receiving portion. (FIG. 4 (d)). The photosensor 56 outputs a predetermined signal to a control circuit (not shown), and the control circuit counts the number of recording materials based on the output signal from the photosensor 56. The recording material P conveyed onto the fixing inlet guide 52 is introduced into the fixing nip N by the fixing inlet guide 52. The recording material P is sandwiched between the surface of the fixing belt 43 and the surface of the pressure belt 23 and is transported (clamped and transported) to that state. In the conveying process, heat is applied to the toner image t from the fixing belt 43 and the pressure belt 23 and nip pressure is applied from the fixing nip portion N. The toner image t is formed on the recording material P by the heat and nip pressure. Heat-fixed on the surface. Then, the recording material P is heated and fixed, and the toner image is separated from the surface of the fixing belt 43 and discharged from the fixing nip portion N.

  (2-7) Explanation when the pressure unit is replaced: FIG. 6A shows a cross section of the pressure unit and the fixing inlet guide unit along the line AA in FIG. 3A before the pressure unit is removed. FIG. 4 is a top view of the pressure unit and the fixing inlet guide unit as viewed from above in FIG. FIG. 3B is a cross-sectional view of the pressure unit and the fixing inlet guide unit along line AA in FIG. 3A when the pressure unit is removed, and the pressure unit and the fixing inlet guide unit shown in FIG. It is the top view seen from the top. FIG. 4C is a cross-sectional view of the pressure unit and the fixing inlet guide unit taken along line AA of FIG. 3A after the pressure unit is removed.

  When the pressure unit 20 of the fixing device 15 attached to the image forming apparatus main body 100 is replaced, first, the power of the image forming apparatus is turned off, and then the open / close cover of the image forming apparatus main body 100 is closed as described above. The fixing device 15 is opened and taken out from the image forming apparatus main body 100. Then, the fixing unit 40 is removed from the fixing frame 60 of the fixing device 15. In order to remove the fixing unit 40, the pins 42a to 42d locked in the holes 69a to 69d of the support plates 62a1 and 62b1 of the left support frame 62a and the right support frame 62b of the fixing frame 60 are used with a predetermined tool. Then, it is slid in the longitudinal direction and separated from the holes 69a to 69d. The fixing unit 40 has a handle 47a (FIG. 2) provided on the fixing unit cover 47 of the fixing unit 40, and the fixing unit 40 has the left support frame 62a and the right support frame 62b of the fixing frame 60 shown in FIG. 6A. Are pulled up along the inner surfaces of the pair of support plates 62a1 and 62b1. As a result, the fixing unit 40 can be detached from the fixing frame 60.

  Next, the pressure unit 20 is removed from the fixing frame 60. When the pressure unit 20 is removed, the rotary pins 64a and 64b are inserted into the holes 68a and 68b of the pair of support plates 62a1 and 62b1 of the left support frame 62a and the right support frame 62b of the fixing frame 60 with a predetermined tool. Use and pull out. In this state, the pressure unit 20 can be removed from the fixing frame 60. The removal direction (removal direction) of the pressure unit 20 is along the inner surfaces of the pair of support plates 62a1 and 62b1 of the left support frame portion 62a and the right support frame portion 62b of the fixing frame 60, similarly to the removal direction of the fixing unit 40. Direction. However, when the fixing inlet guide 52 is at the recording material introduction position, the short side of the fixing inlet guide 52 in the projection area of the pressure belt 23 (shaded portion in FIG. 6A) viewed from the direction in which the pressure unit 20 is removed. The other end portion 52o in the direction overlaps the one end portion 23i in the short direction of the pressure belt 23. Therefore, when the pressure unit 20 is pulled up in the direction in which the pressure unit 20 is removed, the other end 52o in the short direction of the fixing inlet guide 52 physically interferes (collises) with the one end 23i in the short direction of the pressure belt 23. The surface of the pressure belt 23 is damaged. Damage to the surface of the pressure belt 23 is undesirable because it may be transferred to the toner image being heated and fixed on the recording material carrying surface by the nip pressure at the fixing nip portion N, and glossy streaks may occur. In order to prevent this, the fixing inlet guide 52 is manually rotated from the recording material introduction position in the arrow direction shown in FIG. 6B against the biasing force of the inlet guide biasing spring 53. The fixing inlet guide 52 rotated in the direction of the arrow stops when one end portion 52 i in the short direction of the fixing inlet guide 52 comes into contact with a stopper portion 51 c provided at one end portion in the short direction of the fixing inlet guide support member 51. (FIG. 4 (e)). The position at which the fixing inlet guide 52 stops is retracted so that the other end portion 52o in the short direction of the fixing inlet guide 52 does not overlap the one end portion 23i in the short direction of the pressure belt 23 along the projection locus of the pressure belt 23. The retracted position (FIG. 4E). Since the inlet guide biasing spring 53 is disposed in a toggle manner, when the fixing inlet guide 52 is rotated from the recording material introduction position to the retracted position, the biasing direction of the inlet guide biasing spring 53 changes during the rotation. Then, the fixing inlet guide 52 is urged to stand in the retracted position. In the first embodiment, the angle difference between the recording material introduction position and the retraction position of the fixing inlet guide 52 is 70 °. In FIG. 4 (e), the fixing inlet guide 52 is rotated about 35 ° counterclockwise. The urging direction of the guide urging spring 53 is switched. In the process in which the fixing inlet guide 52 is rotated to the retracted position, the fixing inlet sensor flag 54 comes into contact with a holding portion 52 c (FIG. 4B) provided on the back side of the fixing inlet guide 52. The fixing inlet sensor flag 54 is held by the holding portion 52c (FIG. 4B) of the fixing inlet guide 52 and rotates to the retracted position of the fixing inlet guide 52 together with the fixing inlet guide 52 with the shaft 54 as a fulcrum (FIG. 4). (E)). The second light shielding member 57b rotates with the shaft 55 as a fulcrum together with the fixing entrance sensor flag 54. Then, the second light shielding member 57b stops at a position where the light emitted from the light emitting portion 56a of the photosensor 56 is shielded (FIG. 4E). Then, the pressure unit 20 is held by hand and pulled up along the inner surfaces of the pair of support plates 62a1 and 62b1 of the left support frame portion 62a and the right support frame portion 62b of the fixing frame 60 shown in FIG. Thereby, the pressure unit 20 can be removed from the fixing frame 60 (FIG. 6C). In this way, by allowing the fixing inlet guide 52 to stand by in the standing state at the retracted position (FIGS. 6B and 6C), from the locus drawn by the pressure unit 20 when the pressure unit 20 is removed from the fixing frame 60. The fixing entrance guide 52 can be retracted.

  After the pressure unit 20 is removed, a new pressure unit (not shown) having the same configuration as the pressure unit 20 is attached to the fixing frame 60. In order to attach a new pressure unit, a new pressure unit is first held by hand, and a pair of support plates 62a1, 62a1 of the left support frame portion 62a and the right support frame portion 62b of the fixing frame 60 shown in FIG. Lower along the inner surface of 62b1. Then, the hole at the center of rotation of the left pressure frame in the new pressure unit and the hole 68a of the left support frame 62a of the fixing frame 60 are made to communicate with each other. Further, the hole of the rotation center portion 22b of the right pressure frame 21b and the hole 68b of the right support frame portion 62b of the fixing frame 60 are made to communicate with each other. Then, the rotation pin 64a is inserted into the hole at the rotation center portion of the left pressure frame and the hole 68a of the left support frame portion 62a, and the hole at the rotation center portion 22b of the right pressure frame 21b and the hole of the right support frame portion 62b. The rotation pin 64 b is inserted into the hole 68 b and the pressure unit 20 is attached to the fixing frame 60.

  After the pressure unit 20 is attached to the fixing frame 60, the fixing unit 40 is attached to the fixing frame 60. At this time, the fixing unit 40 may be replaced with a new fixing unit (not shown) having the same configuration as the fixing unit 40 as necessary. In the first embodiment, a case where the fixing unit 40 is used as it is and attached to the fixing frame 60 will be described. First, the holding unit 47a of the fixing unit 40 is held, and the fixing unit 40 is moved along the inner surfaces of the pair of support plates 62a1 and 62b1 of the left support frame 62a and the right support frame 62b of the fixing frame 60 shown in FIG. Lower. Then, the pins 42a to 42d on one end side in the short side direction and the other end side in the short side direction of the left fixing frame 41a and the right fixing frame 41b are slid into the holes 69a to 69d of the fixing frame 60 using the predetermined tool. Stop. As a result, the fixing unit 40 is attached to the fixing frame 60. Then, the fixing device 15 having the new pressure unit and the fixing unit 40 attached to the fixing frame 60 is mounted on the image forming apparatus main body 100 as described above. Then, the image forming apparatus is turned on. Then, since the second light blocking member 57b stops at a position where the light emitted from the light emitting portion 56a of the photosensor 56 is blocked, the photosensor 56 outputs a predetermined signal to the control circuit. Based on the output signal from the photosensor 56, the control circuit performs a display on the operation display unit for prompting the jam processing. Therefore, when the pressure unit 20 is replaced with a new pressure unit, even if the fixed entrance guide 52 is forgotten to be returned to the recording material introduction position and the image forming apparatus is operated in the retracted position, the jam will occur when the power is turned on. Will be detected and jam processing will be prompted. When performing the jam processing, it is necessary to take out the fixing device 15 from the image forming apparatus main body 100. At this time, the position of the fixing inlet guide 52 can be confirmed. Therefore, when the fixing inlet guide 52 is forgotten to be returned to the recording material introduction position, the fixing inlet guide 52 may be returned to the recording material introduction position. Thereby, it is possible to prevent forgetting to return the fixing inlet guide 52 to the recording material introduction position.

[Other examples]
In the first exemplary embodiment, the fixing inlet guide is rotatably supported by the fixing frame so as to be displaceable at two positions, that is, a recording material introduction position and a retracted position. The fixing frame may be slidably supported so as to be displaceable at two positions.

20: pressure unit, 23: pressure belt, 40: fixing unit, 43: fixing belt, 52: fixing inlet guide, 54: fixing inlet sensor flag, 60: fixing frame, N: fixing nip, P: recording material , T: toner image

Claims (3)

A heating unit having a heating rotator, a pressure unit having a pressure rotator that contacts the heating rotator to form a nip portion, and a recording material carrying an image at the nip portion is heated while being nipped and conveyed. In the image heating device,
A frame that removably supports the pressure unit;
A guide for introducing the recording material into the nip portion, and a downstream end portion of the guide in the recording material conveyance direction in the projection region of the pressure rotating body viewed from the direction in which the pressure unit is removed. recording material introducing position and the front pressurizing unit when detached from the frame SL pressure rotating body when not overlap with the recording material conveyance direction upstream end portion of the rotating body to introduce the recording material into the nip In the projection area, the downstream end of the guide in the recording material conveyance direction is retracted from the projection area so that it does not overlap the upstream end of the pressure rotator in the recording material conveyance direction. A guide supported by the frame in a displaceable manner;
A detection member for detecting that the guide introduces the recording material into the nip portion, and detecting that the guide is displaced to the retracted position;
An image heating apparatus comprising:   The image heating apparatus according to claim 1, wherein the detection member is provided in the guide. 3. The image heating according to claim 1, wherein the heating unit is detachably supported on the frame, and a removal direction of the heating unit is the same as a removal direction of the pressure unit. 4. apparatus.