JP2017015808A - Fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide a fixation device which surely performs rotation detection of a fixation member even when using a lubricant, prevents the fixation member in the non-rotation state from being rapidly heated and prevents the image quality from deteriorating.SOLUTION: A fixation device 12 includes: an endless fixation member 38 which is rotatable; a nip formation member 49 which is arranged on the inner side of the fixation member; a facing rotor 30 which forms a nip portion SN between the fixation member and itself by being brought into contact with the nip formation member via the fixation member; a heat source 50 which heats the fixation member in the nip portion; a lubricant 60 which is applied to the inner surface of the fixation member; a rotation detection unit 69 which detects the rotation of the fixation member. The fixation device 12 fixes an unfixed image carried on a recording material P conveyed to the nip portion SN. The rotation detection unit includes: ring-shaped elastic members 39, 43, 45 installed on the outer peripheral surface of the fixation member on the outer side in the axial direction with respect to the heat source; a drive transmission member 70 which is brought into contact with the ring-shaped elastic members; and detection means 71, 74 which detect the drive transmission member.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a thermal fixing device in an electrophotographic image forming apparatus, and an image forming apparatus such as a copying machine, a printer, and a facsimile equipped with the fixing device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed on an image carrier based on image information, the toner image is transferred onto a recording material such as paper or an OHP sheet, and the toner image is carried. The recorded material is passed through a fixing device, and the toner image is fixed on the recording material by heat and pressure.

  As a fixing device for realizing energy saving, a technique for heating a thin belt or film by a resistance heater in which a resistance heating element is formed on a ceramic or glass substrate has been proposed. Hereinafter, a film heating type fixing device will be described as a conventional configuration of an energy saving fixing device.

"Film heat fixing with plate heater"
There is known a configuration in which a plate-like heating body that contacts a thin cylindrical heat-resistant film and a pressure roller are used to hold the film and a recording material in close contact with each other, thereby giving thermal energy to the recording material (Patent Document 1). Since the film is as thin as about 100 μm, it is only necessary to raise the temperature of the plate-like heating body having a substantially small heat capacity for start-up, so that the start-up time can be shortened and the preheating power can be reduced.

  Patent Document 2 discloses a configuration in which an insulating layer (ceramics, glass) and a resistance heating element are sequentially formed on a metal substrate, and a thin cylindrical heat-resistant film is heated via the metal substrate. In the configuration in which a thin film is directly heated by a plate-like heating body, the film temperature of the non-sheet passing portion is likely to overheat, and the heat resistance and wear of the film are problems. However, by heating the film via the metal substrate, the film temperature is soaked in the longitudinal direction in the metal member, so that it is possible to prevent an excessive increase in the film temperature of the non-sheet passing portion.

  As described in the above-mentioned document, a method for realizing energy saving by heating a thin film using a resistance heater in which a resistance heating element is formed on a ceramic substrate such as alumina or aluminum nitride is widely known. This is because the heat source itself has a low heat capacity, and it can be rapidly heated by directly heating only the nip portion of the film through which the recording material passes.

  However, most of the heating elements need to be provided with an insulating member such as glass on the fixing belt contact surface side of the heating element in order to maintain electrical insulation with the fixing belt. Insulating members such as glass are often used as the insulating member, but since the friction coefficient of the glass itself is not low, friction resistance is generated between the fixing belt and it is difficult to rotate the fixing belt without slipping. was. In order to improve the slidability, it is possible to interpose a member such as a fluororesin between the fixing belt, but since the thermal resistance is large, the member inhibits heat transfer from the heating element and warms up time. There was a problem for energy saving, such as the delay of. For this reason, heat-resistant lubricant is applied directly to the inner surface of the fixing belt and the heating element to reduce the coefficient of friction and improve wear resistance. However, lubricant and its leakage prevention measures are essential. It is.

  On the other hand, in the structure of the heating element, since the heat source is arranged in the nip portion, the portion to be heated is limited (nip portion). Therefore, when the device malfunctions, for example, when the heat source becomes uncontrollable when the fixing belt is not rotating, or when the safety device has poor responsiveness, only the nip portion is heated rapidly, so the fixing belt There was a risk of melting and breakage. As a countermeasure against this, there is a method of providing a safety device inside the nip. However, because the heat generation point is inside the nip, the safety device must be placed inside the fixing belt. There was an increase in time and power consumption.

  Therefore, by providing a rotation detection mechanism that detects the rotation of the fixing belt and a circuit that supplies power to the heat source only when the fixing belt rotates, a safety device (such as a thermostat) can be placed on the surface other than the nip portion of the fixing belt. There is also a method for detecting the abnormality. As a rotation detection method, a method of detecting rotation by a member that rotates following a fixing sleeve (Patent Document 3), or a method of detecting a rotation and speed by an optical sensor provided with a reflection member on a fixing belt (Patent Document 4). Has been proposed.

  According to Patent Document 3, in a fixing device using a thin-film fixing sleeve that generally has a very small heat capacity, when heating is continuously performed with the fixing sleeve stopped, a part of the heated circumferential direction is quickly obtained. The heat resistance temperature of the fixing sleeve will be exceeded (generally within a few seconds). For this reason, the fixing sleeve needs to be always rotated when heated, and when the rotation is stopped or slowed down due to an abnormality, heating needs to be stopped immediately. Therefore, it is necessary to detect the rotation of the fixing sleeve or the fixing roller.

However, when the lubricant and the rotation detection mechanism are used in combination, there are the following new problems.
-The end face of the endless fixing belt cannot be sealed, and the lubricant applied to the inside from the end face may flow out to the outside for reasons such as centrifugal force and pressure deviation. When the lubricant that has flowed out adheres to the surface of the fixing belt, the following problems occur.

-In a rotation detection mechanism that includes a mechanism for contact driven rotation, if the lubricant adheres to the driven rotation member, the driven rotation member slips, and even if the fixing belt rotates, the rotation detection mechanism stops and the fixing belt rotates. Otherwise, there is a risk of false detection.
In addition, in the method of detecting the reflection member of the fixing belt using an optical sensor, there is a risk of erroneous detection if the lubricant adheres to the reflection member.
Further, when the lubricant that has flowed out from the end surface of the fixing belt enters the surface and flows out to the image range, the lubricant adheres to the recording material, which not only disturbs the image but also deteriorates the quality of the printed matter.

  In view of the above problems, the present invention reliably detects rotation of a fixing member even when a lubricant is used, and the fixing member in a non-rotating state is not rapidly heated and does not deteriorate image quality. It aims at realizing at low cost.

  In order to solve this problem, a rotatable endless fixing member, a nip forming member disposed inside the fixing member, and the fixing member in contact with the nip forming member via the fixing member; An opposing rotating body that forms a nip portion therebetween, a heat source that heats the fixing member at the nip portion, a lubricant applied to the inner surface of the fixing member, and a rotation detection portion that detects the rotation of the fixing member The rotation detecting unit is installed on the outer peripheral surface of the fixing member axially outside the heat source in a fixing device that fixes an unfixed image carried on the recording material conveyed to the nip portion. A fixing device comprising: a ring-shaped elastic member; a drive transmission member in contact with the ring-shaped elastic member; and a detection unit that detects the drive transmission member is proposed.

  Even when the lubricant is used, the rotation of the fixing member can be reliably detected, and the fixing member in the non-rotating state is not heated rapidly. Further, since the ring-shaped elastic member is integrated with the outer peripheral surface of the fixing belt by adhesion or the like, it is possible to prevent the lubricant that has flowed out from the inside of the fixing member from diffusing to the image region side on the surface of the fixing member. Furthermore, the degree of freedom of the shape of the fixing member is not hindered by forming the ring-shaped elastic member from an elastic body. Further, by configuring the ring-shaped elastic member with an elastic body, the contact surface is enlarged with the drive transmission member, tackiness and adhesiveness can be improved, and the driving force can be reliably transmitted.

It is a figure which shows the schematic cross-sectional schematic diagram of an image forming apparatus. FIG. 2 is a schematic cross-sectional schematic diagram of a fixing device according to an embodiment. It is a schematic enlarged view of the nip vicinity. 3 is a partial cross-sectional view of a belt in a state where a ring-shaped elastic member 39 is attached to a fixing belt 38. FIG. FIG. 4 is a partial cross-sectional view in the longitudinal direction of a fixing device using a fixing belt with a ring-shaped elastic member 39 attached thereto. 3 is a schematic side view of an encoder 71 and a transmissive photosensor 74. FIG. It is a figure which shows the shape of a ring-shaped elastic member. It is a figure which shows the shape of a ring-shaped elastic member. FIG. 6 is a view showing an example of a ring-shaped elastic member 43 that is deformed along with the deformation of the fixing belt 38. FIG. 6 is a partial cross-sectional view of a belt in a state where a ring-shaped elastic member 45 according to another embodiment is attached to a fixing belt.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional schematic diagram of an image forming apparatus. As shown in FIG. 1, a printer as an example of an image forming apparatus according to the present embodiment includes a paper feeding unit 4, a registration roller pair 6, a photosensitive drum 8 as an image carrier, a transfer unit 10, It has a fixing device 12 and the like.

  The paper feeding means 4 feeds the paper P as a recording material stored in a stacked state and the paper P stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16 and the like. The paper P delivered by the paper supply roller 16 is temporarily stopped by the registration roller pair 6 to correct the posture deviation. Thereafter, the sheet P is registered at a timing synchronized with the rotation of the photosensitive drum 8, that is, at a timing at which the leading end of the toner image formed on the photosensitive drum 8 coincides with a predetermined position at the leading end of the sheet P in the transport direction. It is sent to the transfer site N by the roller pair 6.

  Around the photosensitive drum 8, a charging roller 18, a mirror 20 constituting a part of an exposure unit, a developing unit 22 including a developing roller 22a, a transfer unit 10, and a cleaning blade 24a are provided in the order of rotation indicated by arrows. The cleaning means 24 and the like are arranged.

  Between the charging roller 18 and the developing means 22, exposure light Lb is irradiated to the exposure unit 26 on the photosensitive drum 8 via the mirror 20 and scanned.

  The image forming operation in the printer is performed in the same manner as in the past. That is, when the photosensitive drum 8 starts to rotate, the surface of the photosensitive drum 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated and scanned on the exposure unit 26 based on the image information to create an image to be created. An electrostatic latent image corresponding to is formed.

The electrostatic latent image is moved to the developing means 22 by the rotation of the photosensitive drum 8, where toner is supplied to be visualized to form a toner image.
The toner image formed on the photosensitive drum 8 is transferred onto the paper P that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer means 10.
The paper P carrying the toner image is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged and stacked on the paper discharge tray.

Residual toner remaining on the photosensitive drum 8 without being transferred at the transfer portion N reaches the cleaning means 24 as the photosensitive drum 8 rotates, and is scraped off by the cleaning blade 24 a while passing through the cleaning means 24. To be cleaned.
Thereafter, the residual potential on the photosensitive drum 8 is removed by the charge eliminating means, and is prepared for the next image forming step.

<Fixing device>
FIG. 2 is a schematic cross-sectional schematic diagram of the fixing device according to the embodiment.
The fixing device includes a fixing belt 38 that is a rotatable endless fixing member, a nip forming member 49 disposed inside the fixing belt, and a fixing belt that contacts the nip forming member 49 via the fixing belt. The pressure roller 30 as the counter rotating body that forms the nip portion SN is provided between the pressure roller 30 and the pressure roller 30. Further, the fixing device has a heater 50 as a heat source for heating the fixing member at the nip portion and a fluid lubricant on the inner surface of the fixing member, and is undetermined carried on the recording material P conveyed to the nip portion SN. Fix the ringtone image.
The heater 50, the insulating layer 51, the heat transfer member 52, the holder 53, and the like constitute a nip forming member 49.

  However, the fixing device may be a system in which the fixing belt 38 is heated by a halogen heater, or a structure in which a sheet heating element is provided in the nip inside the halogen heater. The heat source may be a heat source of a different method such as an induction heating method or an external radiation heating method.

  Here, since the lubricant is applied to the inner surface of the fixing belt 38, the lubricant is interposed between the nip forming member 49 and the fixing belt 38, but a sliding sheet is further provided on the outer surface of the nip forming member 49. It may be provided.

  Although the shape of the nip portion is flat in FIG. 2, it may be a concave shape or other shapes. When the nip portion has a concave shape, the discharge direction of the front end of the recording material is closer to the pressure roller 30 and the separation property is improved, so that the occurrence of jam is suppressed.

Belt Configuration The fixing belt 38 is configured by an endless belt or a film using a metal material such as nickel or SUS or a resin material such as polyimide. The surface layer of the belt has a release layer such as a PFA or PTFE layer, and has a release property so that toner does not adhere. There may be an elastic layer formed of a silicone rubber layer or the like between the belt substrate and the PFA or PTFE layer. When there is no silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and the image has a crusty skin shape. There arises a problem that the gloss unevenness (zudder skin image) remains. In order to improve this, it is necessary to provide a silicone rubber layer of 100 [μm] or more. Due to the deformation of the silicone rubber layer, fine irregularities are absorbed and the skin image is improved.

  In this embodiment, the fixing belt 38 has a thin film substrate made of nickel (Ni) having an outer diameter of 30 mm and a thickness of 10 to 70 μm, and an elastic layer coated on the surface of the substrate. The elastic layer is formed of a heat-resistant elastic body such as silicone rubber or fluororubber, and has a thickness of 50 to 150 μm. The outermost layer of the fixing belt 38 is a layer of a fluorine resin such as PFA or PTFE and has a thickness of 5 to 50 μm in order to enhance durability and ensure releasability from the toner. It is formed.

-Pressure roller The pressure roller 30 has the metal core 30a and the elastic layer 30b on it, and has the mold release layer 30c (PFA or PTFE layer) on the surface in order to acquire mold release property. The pressure roller 30 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus via a gear. The pressure roller 30 is pressed against the fixing belt 38 by a spring or the like, and has a predetermined nip width when the elastic layer 30b is crushed and deformed. The pressure roller 30 may be a hollow roller, and the pressure roller 30 may have a heat source such as a halogen heater. The elastic layer 30b may be solid rubber, but if there is no heater inside the pressure roller 30, sponge rubber may be used. Sponge rubber is more desirable because it increases heat insulation and makes it difficult for the fixing belt to lose heat.

In this embodiment, the pressure roller 30 is formed of a hollow iron cored bar 30a, an elastic layer 30b formed on the surface of the cored bar 30a, and a release layer 30c. The outer diameter of the pressure roller is 30 mm. It is.
The elastic layer 30b is made of silicone rubber and has a thickness of 5 mm. On the surface of the elastic layer 30b, it is desirable to form a fluororesin layer having a thickness of about 40 μm as the release layer 30c in order to improve the release property.

FIG. 3 is a schematic enlarged view of the vicinity of the nip portion. The heater 50 is disposed in the nip portion and heats the fixing belt 38 from the inner surface. A heat transfer member 52 may be provided between the fixing belt 38 and the heater holder 53. By configuring the heat transfer member with a high heat conductive material such as copper or aluminum to improve the heat transfer property in the longitudinal direction of the heater 50, the temperature deviation in the longitudinal direction of the fixing belt 38 can be reduced.

  The heater 50 is a heating element in which a resistance heating element 50a is formed on a glass plate substrate 50b. The resistance heating element 50a is formed on the substrate by screen printing, and is electrically insulated from the outside by further forming an insulating layer 51 such as glass on the resistance heating element 50a.

  The heater 50 is supported by a heater holder 53. The heater holder 53 is easily heated by the heat of the heater, and has a heat resistance such as LCP (Liquid Crystal Polymer), PPS (Poniphenylene Sulfide), PAI (Polyamideimide), PI (Polyimide), and PEEK (Polyether Ether Ketone). It is made of high resin. Heat insulation can be improved by forming the heater holder 53 with a resin having a lower thermal conductivity. Further, as shown in FIG. 2, the heater holder 53 does not come into contact with the heater 50 immediately below the resistance heating element 50a, but comes in contact with two places avoiding the resistance heating element 50a. Thereby, the amount of heat flowing from the heater 50 to the heater holder 53 can be further reduced, and heat can be efficiently transferred to the heat transfer member on the high heat conduction side and the fixing belt 38.

  The heater holder 53 is supported by the stay 61. The stay 61 is supported by both side plates, receives the pressing force of the pressure roller 30, and forms a nip portion SN.

  Although the heat transfer member 52 is in sliding contact with the fixing belt 38, a low friction coating is formed on the contact surface side with the fixing belt 38 in order to reduce torque and belt wear. As a material for the coating layer, DLC (diamond-like carbon), PTFE or the like having a low friction coefficient is suitable. Considering the heat transfer performance of the heat transfer member 52 and the fixing belt 38, it is preferable that the coating layer is thin, and it is preferably about 2 to 50 μm.

  When the heat transfer member 52 is disposed on the side opposite to the nip surface, the insulating layer 51 is slid in contact with the fixing belt 38. At this time, the heater 50 may be coated in the same manner as described above, or only the insulating layer 51 of glass may be used, and it is desirable to use a lubricant as a sliding aid for extending the life.

Sensor and Heating Control As shown in FIG. 2, the fixing device has a thermistor 34 as temperature detecting means for detecting the temperature of the fixing belt 38 downstream of the nip portion SN. The temperature of the fixing belt 38 is controlled to a desired temperature by controlling the power supplied to the heater 50 by the heating control means in accordance with the detected temperature detected. The heating control means means a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

FIG. 4 is a partial cross-sectional view of the belt with the ring-shaped elastic member 39 attached to the fixing belt 38.
The ring-shaped elastic member 39 is made of heat-resistant rubber, such as silicone rubber or fluororubber, and is attached near the end of the fixing belt 38 and outside the maximum image range in the belt axial direction. The inner peripheral diameter of the ring-shaped elastic member 39 and the outer peripheral diameter of the fixing belt 38 are formed substantially the same, and these are fixed with a heat-resistant adhesive or the like. It is desirable to use a silicone adhesive or the like as the heat-resistant adhesive so that the ring-shaped elastic member 39 follows the deformation during rotation of the thin fixing belt 38 and does not peel off.

  The ring-shaped elastic member 39 is disposed about 1 to 5 mm from the end surface of the fixing belt 38. This is because when the ring-shaped elastic member 39 protrudes from the fixing belt 38, it comes into contact with the belt end surface protection ring 44 (see FIG. 5) and becomes resistance during rotation, and the belt end surface protection ring 44 does not rotate.

  The belt end face protection ring 44 is rotated by the rotation of the fixing belt 38, and the fixing belt 38 moves in the axial direction when the parallelism with the pressure roller 30 is shifted. Therefore, if the fixing belt 38 moves to the left in FIG. 5 without the belt end face protection ring 44, the fixing belt 38 is pressed against the belt support member 40.

  Since the thickness of the fixing belt base material is as thin as 10 to 70 μm, the strength is weak, and the fixing belt 38 may be damaged due to local contact or catching with the belt support member 40. Therefore, the belt end face protection ring 44 is provided so that the rotating fixing belt 38 and the fixed belt support member 40 do not come into direct contact with each other.

  In FIG. 4, the heater 50 is held in a heater holder 53, and a lubricant 60 (fluorine-based grease, silicone oil) is applied between the fixing belt 38 and the heater 50, and the friction resistance between the heater 50 and the fixing belt 38. Is reduced. The heater 50 extends in the axial direction of the fixing belt 38 so as to cover the maximum sheet passing width.

FIG. 5 is a partial sectional view in the longitudinal direction of the fixing device using the fixing belt 38 to which the ring-shaped elastic member 39 is attached.
The rotation detector 69 detects the rotation of the fixing belt 38. The rotation detection unit 69 rotates the ring-shaped elastic member 39 installed on the outer circumferential surface of the fixing belt axially outside the heater 50, the driven roller 70 that contacts the ring-shaped elastic member 39 as a drive transmission member, and the driven roller 70. An encoder 71 is provided as detection means that rotates with the rotation. The rotation detection unit 69 includes a transmissive photosensor 74 as detection means for detecting the encoder 71. The driven roller 70 contacts the outer peripheral surface of the ring-shaped elastic member 39 and rotates in conjunction with the rotation of the fixing belt 38 and the elastic member 39. The driven roller 70 is fixed to one end of the rotation detection shaft 72, and the encoder 71 is fixed to the other end of the rotation detection shaft 72. Accordingly, the encoder 71 rotates as the fixing belt 38 rotates. The rotation detection shaft 72 is rotatably supported by a bearing 73 and is fixed to the side plate 42. The metal core 30 a of the pressure roller 30 is rotatably fixed to the side plate 42 by a bearing 41.

  As described above, as a means for detecting the rotation state of the fixing belt 38, the ring-shaped elastic member 39 is provided at the end portion of the outer peripheral surface of the fixing belt, and the driven roller 70 is brought into contact with and driven by the ring-shaped elastic member. Detect. Then, electric power is supplied from the power source to the heater 50 only when the fixing belt 38 rotates. The surface of the fixing belt made of a fluororesin having a high toner releasability has good slipperiness, and slipping is likely to occur when a driven roller or the like is brought into direct contact with the fixing belt 38. Therefore, the slipperiness is lowered and the drive can be transmitted. Since the ring-shaped elastic member 39 is integrated with the outer circumferential surface of the fixing belt by adhesion or the like outside the heater 50 in the axial direction, the ring-shaped elastic member 39 has the lubricant 60 that has flowed out from the inside of the fixing belt. Prevents diffusion to the image area side of the surface. The ring-shaped elastic member 39 functions as a lubricant diffusion preventing wall.

  Further, the fixing belt 38 does not rotate while maintaining a perfect circle, and is often used with a smaller radius of curvature on the nip outlet side in order to improve the separation property from the recording material. Therefore, forming the ring-shaped elastic member with an elastic body does not hinder the degree of freedom of the shape of the fixing belt. In addition, since the ring-shaped elastic member 39 is made of an elastic body, the contact surface can be enlarged between the driven roller 70 and the tackiness and adhesiveness can be improved, so that the driving force can be reliably transmitted. .

  The lubricant 60 applied to the inner surface of the fixing belt 38 tends to flow due to a decrease in viscosity due to rotational driving, pressure deviation at the nip portion, heating, and the like. The lubricant 60 that has flowed to the end face side of the fixing belt 38 flows out from the end face of the fixing belt 38.

FIG. 6 is a schematic side view of the encoder 71 and the transmissive photosensor 74.
As shown in the figure, the encoder 71 has blades, and the transmissive photosensor has a detection unit including a light emitting unit that emits detection light and a light receiving unit that receives the detection light. The blade is sandwiched between the light emitting unit and the light receiving unit and is in a state of entering the detection unit. Therefore, the blades periodically block the optical path of the transmissive photosensor 74 as the encoder rotates. As the fixing belt 38 rotates, the blades rotate, and the detection light is detected by the light receiving unit every time the space between the blades (space part) passes through the detection unit. Detected. When the transmission photosensor 74 detects this rotation, it sends an electrical signal to the control means.

7 and 8 are diagrams showing the shape of the ring-shaped elastic member.
In the example of FIG. 7, the ring-shaped elastic member 39 is configured as a circular ring. As can be seen from FIGS. 4 and 5, the ring-shaped elastic member 39 covers the outer peripheral surface of the fixing belt in the vicinity of the end surface of the fixing belt 38 and on the inner side in the axial direction from the end surface. By disposing the installation position of the ring-shaped elastic member on the inner side of the end surface of the fixing belt, contact between the ring-shaped elastic member 39 and the belt support member 40 that supports the fixing belt and restricts in the axial direction is prevented. As a result, the rotational resistance and driving torque of the fixing belt 38 are not increased.

  In the example of FIG. 8, the ring-shaped elastic member is configured as a spur gear-type ring-shaped elastic member 43 having teeth on the outer peripheral surface of a circular ring. In this case, the ring-shaped elastic member 43 and the driven roller 70 mesh with each other by providing the same tooth portion on the outer peripheral surface of the driven roller 70. Therefore, even if the lubricant adheres to the ring-shaped elastic member 43 or the tackiness / adhesiveness decreases due to aging, the drive can be reliably transmitted to the driven roller 70 without slipping. By making the shape of the ring-shaped elastic member a spur gear type, the drive can be mechanically transmitted to the drive transmission member regardless of the slipperiness.

FIG. 9 is a diagram illustrating an example of the ring-shaped elastic member 43 that is deformed along with the deformation of the fixing belt 38.
As can be seen from FIG. 2, the cross-sectional shape of the fixing belt 38 is not a perfect circle. When such a fixing belt 38 is provided with a circular ring-shaped elastic member 39 and a driven roller 70, the contact width (nip width) between the ring-shaped elastic member 39 and the driven roller 70 is wide at a portion having a larger arc diameter. The contact width is narrow at the portion where the arc diameter is small, and the drive transmission is poor. If the spur gear type ring-shaped elastic member 43 and the spur gear type driven roller 70 are engaged with each other, the position of the driven roller 70 can be set regardless of the arc diameter.

FIG. 10 is a partial cross-sectional view of a belt in a state where a ring-shaped elastic member 45 according to another embodiment is attached to the fixing belt 38.
In the present embodiment, the end surface side of the ring-shaped elastic member 45 is inclined toward the end surface side of the fixing belt and the belt end surface protection ring 44 side. Thereby, even when the lubricant 60 adheres to the side surface of the ring-shaped elastic member 45, the lubricant 60 can be prevented from adhering to the image range side of the surface of the fixing belt. A belt support member 40 as a support member supports both ends of the fixing belt 38. The belt end surface protection ring 44 as a rotating member is a thin plate-like member that extends radially outward from the end surface of the fixing belt 38 in the axial direction, and is provided on the belt support member 40 to synchronize with the rotation of the fixing belt. Rotate. The belt end surface protection ring 44 prevents the fixing belt end surface from being damaged due to contact with or being caught by the belt support member 40.

  However, since there is no heater 50 near the end surface of the fixing belt and the temperature is lower than the sheet passing range, the viscosity of the lubricant 60 tends to increase. If the lubricant 60 having increased viscosity adheres to the belt end face protection ring 44, the belt end face protection ring 44 may not rotate smoothly, and as a result, damage such as cracks may occur on the fixing belt end face. Therefore, the end surface side of the ring-shaped elastic member 45 is inclined toward the end surface side of the fixing belt, protrudes outward in the axial direction from the fixing belt 38, and is in contact with the belt end surface protection ring 44. A part of the ring-shaped elastic member 45 is brought into contact with the belt end surface protection ring 44 to assist the rotation of the protection ring, thereby preventing the fixing belt end surface from being damaged.

It is preferable that a gap 63 for confining the lubricant is formed between the ring-shaped elastic member 45 and the belt end surface protection ring 44. As shown in FIG. 10, the lubricant 60 that has flowed out from the inside of the fixing belt in the axial direction enters the gap portion 63 and is sealed by the ring-shaped elastic member 45 and the belt end surface protection ring 44.
The ring-shaped elastic member 45 is bonded and integrated with the fixing belt 38 slightly on the inner side in the axial direction and on the center side with respect to the end face of the fixing belt 38.

  The lubricant 60 applied to the inner surface of the fixing belt 38 tends to flow due to a decrease in viscosity due to rotational driving, pressure deviation at the nip portion, heating, and the like. The lubricant 60 that has flowed to the end face side of the fixing belt 38 flows out from the end face of the fixing belt 38. The low-viscosity lubricant 60 falls to the bottom due to its own weight, but when the high-viscosity lubricant 60 is used, the lubricant may adhere to the surface of the fixing belt 38 without dropping.

  For example, if the ring-shaped elastic member 39 is not provided in the fixing device of FIG. 4 and the driven roller 70 is in direct contact with the fixing belt 38, if the lubricant 60 flows out and adheres to the driven roller 70, the driven roller 70 slips. There is a fear. Even if the ring-shaped elastic member 39 is present, the lubricant flows out to the outer peripheral side of the fixing belt 38 due to the centrifugal force generated by the rotation of the fixing belt 38 and adheres to the contact surface of the ring-shaped elastic member 39 with the driven roller 70. Resulting in.

  Therefore, as shown in FIG. 10, by forming the ring-shaped elastic member 45 as an inclined surface, it is possible to prevent the lubricant 60 from flowing out in close contact with the belt end surface protection ring 44.

As described above, according to the present invention, problems caused by the heating of the fixing belt rapidly when not rotating are eliminated.
For this purpose, the fixing device according to the embodiment of the present invention includes a rotation detection unit including a ring-shaped elastic member integrated with the outer peripheral surface of the fixing belt and a drive transmission member that contacts and transmits rotation.

The fixing device preferably has the following configuration so that slippage does not occur even when the lubricant in the fixing belt adheres to the surface of the fixing belt and erroneous detection is not caused.
-The ring-shaped elastic member is provided with a tooth portion to reliably transmit the drive to the drive transmission member.
-Preventing the lubricant from wrapping around by inclining the end face of the ring-shaped elastic member.
The rotation of the rotating member is assisted by bringing the ring-shaped elastic member into contact with the rotating member that protects the end surface of the fixing belt. As a result, it is possible to prevent the fixing belt end face from being damaged due to the rotation member becoming defective in rotation due to adhesion of the lubricant.

12 Fixing device 30 Pressure roller (opposite rotating body)
38 Fixing belt (fixing member)
39, 43, 45 Ring-shaped elastic member 49 Nip forming member 50 Heater (heat source)
60 Lubricant 69 Rotation detector 74 Transmission type photo sensor (detection means)
P Recording material SN Nip part

Japanese Patent Laid-Open No. 06-95540 Japanese Patent Laid-Open No. 08-272240 Japanese Patent No. 5560791 Japanese Patent No. 4532687

Claims (7)

A rotatable endless fixing member;
A nip forming member disposed inside the fixing member;
An opposing rotating body that contacts the nip forming member via the fixing member and forms a nip portion with the fixing member;
A heat source for heating the fixing member at the nip portion;
A lubricant applied to the inner surface of the fixing member;
A rotation detector for detecting rotation of the fixing member;
In a fixing device for fixing an unfixed image carried on a recording material conveyed to the nip portion,
The rotation detection unit includes a ring-shaped elastic member installed on an outer peripheral surface of the fixing member that is axially outer than the heat source, a drive transmission member that contacts the ring-shaped elastic member, and a detection that detects the drive transmission member. And a fixing device.   The fixing device according to claim 1, wherein the ring-shaped elastic member and the drive transmission member have tooth portions that mesh with each other on their outer peripheral surfaces.   3. The fixing device according to claim 1, wherein an installation position of the ring-shaped elastic member is an inner side in an axial direction from an end surface of the fixing member.   The fixing device according to claim 1, wherein an end surface side of the ring-shaped elastic member is inclined toward an end surface side of the fixing member. A support member for supporting both ends of the fixing member;
A thin plate-like rotating member provided on the support member and rotating in synchronization with the rotation of the fixing member;
The fixing device according to claim 1, wherein an end surface side of the ring-shaped elastic member is in contact with the rotating member.   The fixing device according to claim 5, wherein a gap for confining a lubricant is formed between the ring-shaped elastic member and the rotating member. An image forming apparatus comprising the fixing device according to claim 1.

Images