JP5120915B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein.

2. Description of the Related Art Conventionally, an on-demand fixing device having a short rise time is widely known as an image forming apparatus such as a copying machine or a printer (see, for example, Patent Document 1).
An on-demand fixing device includes a fixing film (endless film) as a fixing member, a pressure roller (pressure member), a heater (heating means) such as a ceramic heater, and the like. The heater is installed inside the fixing film, contacts the pressure roller through the fixing film to form a nip portion, and heats the fixing film. The toner image on the recording medium conveyed toward the nip portion is fixed on the recording medium by receiving heat and pressure at the nip portion.

  On the other hand, in Patent Document 2 and the like, an induction heating plate that is heated by electromagnetic induction opposite to an exciting coil is installed inside a fixing film (film material) and brought into contact with a pressure roller through the fixing film. A technique for forming a nip portion and heating a fixing film is disclosed.

JP 2002-6656 A JP-A-9-185984

The conventional on-demand fixing device described above has poor exchangeability (maintenance) of heating means such as a heater.
This will be described in detail below.
Since the life of the heater is finite, the heater is often replaced and maintained in the fixing device. However, since the heater is in pressure contact with the pressure roller via the fixing film, it is difficult to pull out the heater in a state of pressure in the width direction (longitudinal direction) as it is.
In order to solve such a problem, a method of providing a mechanism for releasing the pressure between the heater (fixing film) and the pressure roller is also conceivable. That is, after operating the pressure release mechanism to release the pressure between the heater and the pressure roller, the heater can be removed from the apparatus. However, in that case, an extra cost and space for installing the pressure release mechanism are required.

  In particular, the conventional on-demand fixing device is in a state in which the pressure by the pressure member is always applied to the heater, and the heater is easily damaged during jam processing or transportation. In addition, the above problem cannot be ignored.

  Further, in the technique described in Patent Document 2 and the like described above, the exciting coil for electromagnetically heating the induction heating plate does not have a function of forming a nip portion, and the pressure by the pressure member directly acts on the exciting coil. Although not, no measures for directly solving the above-described problem are disclosed.

  The present invention has been made to solve the above-described problems, and provides a fixing device and an image forming apparatus in which the startup time of the apparatus is short, the structure is relatively simple, and the heating means is highly replaceable. There is to do.

According to a first aspect of the present invention, a fixing device heats and melts a toner image, contacts an endless fixing film having flexibility, and a pressure member via the fixing film. A contact member fixed inside the fixing film to form a nip portion, a heating means for heating the contact member, and holding the heating means, both ends of which are supported by the side plate of the apparatus. A holding member that is formed in a circular shape so as to face the inner peripheral surface of the fixing film at a position excluding the nip portion, and is screwed to a width direction end of the holding member. , the heating means and a second holding member having holes formed to be engaged is, the heating means is held in the holder member by the second holding member, the second holding with respect to the holding member Part Wherein the de-one in which the contact member is inserted and removed from the apparatus of the contact with the said pressure member via the fixing film.

A fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the contact member is held by the holding member.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect of the present invention, the heating means is an infrared heater that reflects infrared rays emitted from the infrared heater. And a reflection member that increases the heating efficiency of the contact member, and the reflection member is held by the holding member .

According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the reflecting member is installed on the opposite side of the side where the infrared heater faces the contact member. There is .

  According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, the reflecting member has a reflectance with respect to infrared rays at a central portion in the width direction and a reflectance with respect to infrared rays at an end portion in the width direction. They are formed differently.

  According to a sixth aspect of the present invention, in the fixing device according to the fourth aspect of the present invention, the reflecting member is formed such that the size at the center in the width direction is different from the size at the end in the width direction. Is.

  The fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the third to sixth aspects, wherein the contact member absorbs infrared rays on a side facing the infrared heater. A member is provided.

  A fixing device according to an eighth aspect of the present invention is the fixing device according to any one of the third to seventh aspects, wherein the heating means is a carbon heater.

  According to a ninth aspect of the present invention, there is provided the fixing device according to the eighth aspect, wherein the carbon heater has a direction in which the amount of radiant heat generated in a direction facing the contact member is orthogonal to the direction. It is formed so as to be larger than the amount of heat of radiant heat emitted to the.

  According to a tenth aspect of the present invention, in the fixing device according to any one of the first to ninth aspects, the surface of the contact member facing the pressure member is a flat shape. It is formed as follows.

The fixing device according to an eleventh aspect of the present invention is the fixing device according to any one of the first to tenth aspects, wherein the contact member has a surface on which the fixing film is slidably contacted with a fluororesin. It is a thing.

  The fixing device according to a twelfth aspect of the present invention is the fixing device according to any one of the first to eleventh aspects, wherein the contact member has a thickness at a center portion in a width direction and a thickness at an end portion in the width direction. Are formed differently.

  The fixing device according to a thirteenth aspect of the present invention is the fixing device according to any one of the first to twelfth aspects, wherein the abutting member has a length in the conveyance direction of the recording medium of the nip portion. It is formed so as to be longer than the nip amount.

  According to a fifteenth aspect of the present invention, in the fixing device according to any one of the first to thirteenth aspects, the pressing member is rotatably installed at a fixed position in the apparatus, and The contact member is urged toward the pressure member.

According to a fifteenth aspect of the present invention, there is provided the fixing device according to any one of the first to fourteenth aspects, wherein the heating means is disposed apart from the abutting member. It is.

The fixing device according to a sixteenth aspect of the present invention is the fixing device according to any one of the first to fifteenth aspects, wherein the fixing film has a frictional force with the pressure member driven in a predetermined direction. It is driven by.

According to a seventeenth aspect of the present invention, there is provided a fixing device according to any one of the first to sixteenth aspects, further comprising detection means for detecting a driving speed of the fixing film.

The fixing device according to an eighteenth aspect of the present invention is the fixing device according to the seventeenth aspect of the present invention, further comprising variable means for varying the driving speed of the fixing film, and the variable means based on the detection result of the detection means. Is to control.

The fixing device according to the nineteenth aspect of the present invention is the fixing device according to the seventeenth or eighteenth aspect of the present invention, wherein the fixing device is supplied to the heating unit when the value detected by the detecting unit is a predetermined value or less. The power to be cut off is cut off.

The fixing device according to the invention of claim 20 wherein, together with the heating and melting bets toner image, a fixing film of endless flexible, contact with the pressure member via the fixing film A contact member fixed inside the fixing film to form a nip portion, a heating means for heating the contact member, and an inner peripheral surface of the fixing film at a position excluding the nip portion. The guide film is formed in a circular shape to guide the fixing film, and both ends of the fixing film are screwed to the width direction end of the guide member, and the end of the heating unit. The heating means is directly held by the holder without coming into contact with the guide member, and the contact is achieved by attaching and detaching the holder to and from the guide member. It is intended to be inserted and removed from the apparatus in a state in which member is in contact with the pressure member via the fixing film.

An image forming apparatus according to a twenty-first aspect includes the fixing device according to any one of the first to twentieth aspects.

  The present invention is configured such that the heating means can be inserted into and removed from the apparatus in a state where the contact member heated by the heating means and forming the nip portion is in contact with the pressure member via the fixing member. In addition, it is possible to provide a fixing device and an image forming apparatus that have a relatively simple start-up time, a relatively simple configuration, and high exchangeability of the heating means.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a copying machine as an image forming apparatus, 2 an original reading unit that optically reads image information of an original D, and 3 an exposure light L based on image information read by the original reading unit 2. Is exposed to the photosensitive drum 5, 4 is an image forming unit for forming a toner image (image) on the photosensitive drum 5, and 7 is a toner image formed on the photosensitive drum 5 on the recording medium P. A transfer unit 10 for transferring, a document transport unit for transporting the set document D to the document reading unit 2, 12 to 14 a paper feed unit storing a recording medium P such as transfer paper, and 20 on the recording medium P A fixing device for fixing an unfixed image, 21 is a fixing film as a fixing member installed in the fixing device 20, and 31 is a pressure roller as a pressure member installed in the fixing device 20.

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, the document D is conveyed from the document table in the direction of the arrow in the drawing by the conveyance roller of the document conveyance unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 3 toward the photosensitive drum 5 of the image forming unit 4.

On the other hand, in the image forming unit 4, the photosensitive drum 5 is rotated in the clockwise direction in the drawing, and image information is transferred onto the photosensitive drum 5 through a predetermined image forming process (charging process, exposure process, development process). An image (toner image) corresponding to is formed.
Thereafter, the image formed on the photosensitive drum 5 is transferred by the transfer unit 7 onto the recording medium P conveyed by the registration roller.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 12, 13, and 14 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 12 is selected). To do.)
Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 12 is transported toward the position of the transport path K.

  Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller. Then, the recording medium P that has reached the position of the registration roller is conveyed toward the transfer unit 7 at the same timing in order to align with the image formed on the photosensitive drum 5.

After the transfer process, the recording medium P passes through the position of the transfer unit 7 and then reaches the fixing device 20 through the conveyance path. The recording medium P that has reached the fixing device 20 is fed between the fixing film 21 and the pressure roller 31, and the image is fixed by the heat received from the fixing film 21 and the pressure received from both members 21, 31. The The recording medium P on which the image is fixed is delivered from between the fixing film 21 and the pressure roller 31 (a nip portion), and then discharged from the image forming apparatus main body 1.
Thus, a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram showing the fixing device 20. FIG. 3 is a view of a part of the fixing device 20 as viewed in the width direction. FIG. 4 is a diagram illustrating a state in which the infrared heater 25 as a heating unit is inserted into and removed from the fixing device 20. FIG. 5 is a partially enlarged view showing the vicinity of the nip portion of the fixing device 20. FIG. 6 is a view of the heating plate 22 as the contact member as viewed in the width direction. FIG. 7 is a view of the reflection plate 23 as a reflection member as viewed in the width direction.

  As shown in FIG. 2, the fixing device 20 includes a fixing film 21 as a fixing member, a heating plate 22 as an abutting member, a reflecting plate 23 as a reflecting member, a holding member 24, an infrared heater 25 as a heating means, a heating member. It comprises a pressure roller 31 as a pressure member, an optical sensor 40 as detection means, guide plates 35 and 37, and the like.

Here, the fixing film 21 as a fixing member is a thin and flexible endless film, and rotates in the arrow direction (clockwise) in FIG. As a material of the fixing film 21, polyimide, polyamide, fluororesin, metal, or the like can be used. In order to ensure releasability (peelability) with respect to the toner T (toner image), PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide is provided on the surface layer of the fixing film 21. , PES (polyether sulfide), and the like can also be formed. By using the fixing film 21 having a low heat capacity as the fixing member, an on-demand fixing device with an extremely short rise time can be provided.
Inside the fixing film 21 (inner peripheral surface side), an infrared heater 25 (heating means), a heating plate 22, a reflection plate 23, a holding member 24, and the like are fixed. The fixing film 21 is pressed by the heating plate 22 to form a nip portion with the pressure roller 31.

The heating plate 22 as a contact member is a metal plate (or a plate material made of ceramic or polyimide resin) having a thickness of about 0.1 mm, and is heated by the infrared heater 25 (heating by radiant heat). At the same time, a desired nip portion is formed by contacting the pressure roller 31 via the fixing film 21.
In the first embodiment, the opposing surface of the heating plate 22 (the surface facing the pressure roller 31) is formed in a planar shape. As a result, the shape of the nip portion is substantially parallel to the image surface of the recording medium P, and the adhesion between the fixing film 21 and the recording medium P is improved, so that the fixing property is improved and the nip portion passes through the nip portion. The problem of curling or wrinkling on the recording medium P is also reduced. Further, since the curvature of the fixing film 21 on the exit side of the nip portion is increased, the recording medium P sent from the nip portion can be easily separated from the fixing film 21.
Further, the heating plate 22 in the first embodiment has a surface on which the fixing film 21 is slidably contacted with a fluororesin. As a result, it is possible to reduce wear on the inner peripheral surface of the fixing film 21 that is in sliding contact with the heating plate 22 fixedly supported by the fixing device 20.

The infrared heater 25 as a heating means is a carbon heater or a halogen heater, and both ends thereof are fixed to the side plate of the fixing device 20 via the holding member 24. Then, the heating plate 22 is heated by the infrared heater 25 whose output is controlled by the power supply unit of the apparatus body 1, and the fixing film 21 is further heated by the heating plate 22, so that the toner image T on the recording medium P is heated from the surface. Is added. The output control of the infrared heater 25 is performed based on the detection result of the film surface temperature by a temperature sensor (not shown) facing the surface of the fixing film 21. Moreover, the temperature (fixing temperature) of the fixing film 21 can be set to a desired temperature by such output control of the infrared heater 25.
Here, the infrared heater 25 (heating means) is installed so that it can be inserted into and removed from the fixing device 20 in a state where the heating plate 22 is in contact with the pressure roller 31 via the fixing film 21. This will be described in detail later with reference to FIG.

When a carbon heater is used as the infrared heater 25, the degree of freedom of on / off control is increased as compared with the case where a halogen heater is used. Specifically, even if the control for turning off the energization is repeated before the duty of the heater 25 reaches 100%, the output decrease with time is reduced without disconnection.
Further, when a carbon heater is used, its shape is optimized, and the amount of radiant heat generated in the direction facing the heating plate 22 (the vertical direction in FIG. 2) is orthogonal to that direction (FIG. 2). It is preferable that it be formed so as to be larger than the amount of radiant heat generated in the right and left direction. Thereby, since the heat generated from the heater 25 can be concentrated on the heating plate 22, the heating efficiency of the heating plate 22 is increased.

The reflection plate 23 as a reflection member is disposed on the opposite side of the infrared heater 25 from the side facing the heating plate 22 (above the infrared heater 25 in FIG. 2). The reflection plate 23 is a mirror finish on aluminum, and reflects the infrared rays emitted from the infrared heater 25. Since most of the infrared light reflected by the reflecting plate 23 enters the heating plate 22, the heating efficiency of the heating plate 22 is increased.
In the first embodiment, the reflecting plate 23 is installed at a position separated from the infrared heater 25, but on a part of the glass tube of the infrared heater 25 (the side opposite to the side facing the heating plate 22). Gold plating or aluminum vapor deposition may be applied. Also in this case, since the gold plating or aluminum vapor deposition applied to the glass functions as a reflecting member, the heating efficiency of the heating plate 22 is increased.
In addition, an absorbing member that absorbs infrared rays can be provided on the opposing surface of the heating plate 22 (the side facing the infrared heater 25). Specifically, black coating can be applied to the facing surface of the heating plate 22. Thereby, the infrared absorption rate in the heating plate 22 is improved, and the heating efficiency of the heating plate 22 is increased.

Referring to FIG. 3, holding member 24 integrally holds heating plate 22, infrared heater 25, and reflecting plate 23. The holding member 24 is made of a heat resistant resin material, and both ends thereof are respectively supported by the side plates of the fixing device 20.
In particular, the infrared heater 25 is held by the holding member 24 via a holder 27 as a second holding member. Specifically, holders 27 are screwed to both ends of the holding member 24 in the width direction. The holder 27 is provided with a hole that engages with the end of the infrared heater 25. Then, by removing the holder 27 from the holding member 24, only the infrared heater 25 can be detached from the holding member 24 (fixing device 20).

In addition, compression springs 28 are respectively installed at both ends of the holding member 24 in the width direction. As a result, the heating plate 22 as the contact member is biased toward the pressure roller 31 to form a desired nip portion. The pressure roller 31 is rotatably installed on a side plate (fixed position) of the fixing device 20 via a bearing. The pressure roller 31 is rotationally driven in a predetermined direction by a drive motor (not shown), and the fixing film 21 is driven in the direction of the arrow in FIG.
With the configuration described above, the drive mechanism and the pressure mechanism in the fixing device 20 can be simplified.

  Further, referring to FIG. 2, the holding member 24 is formed so as to guide the fixing film 21. That is, the holding member 24 is formed in a circular shape so that the circular posture of the flexible fixing film 21 can be maintained to some extent. Thereby, deterioration and breakage due to deformation of the fixing film 21 can be reduced.

  Referring to FIG. 2, a pressure roller 31 as a pressure member is obtained by forming an elastic layer 33 on a cored bar 32. The elastic layer 33 of the pressure roller 31 is formed of a material such as fluorine rubber, silicone rubber, or foamable silicone rubber. Note that a thin release layer (tube) made of PFA or the like may be provided on the surface layer of the elastic layer 33. The pressure roller 31 is pressed against the fixing film 21 to form a desired nip portion between both members. Further, the pressure roller 31 is rotationally driven in an arrow direction (counterclockwise direction) in FIG. 2 by a drive mechanism (not shown).

  A guide plate 35 (inlet guide plate) for guiding the recording medium P conveyed toward the nip portion is disposed on the entrance side of the contact portion (a nip portion) between the fixing film 21 and the pressure roller 31. It is installed. Further, a guide plate 37 (exit guide plate) for guiding the recording medium P fed from the nip portion is disposed on the outlet side of the nip portion. Both guide plates 35 and 37 are fixed to the frame (housing) of the fixing device 20.

The fixing device 20 configured as described above operates as follows.
When the power switch of the apparatus main body 1 is turned on, power is supplied to the infrared heater 25, and the rotational driving of the pressure roller 31 in the direction of the arrow in FIG. Thereby, the fixing film 21 is also driven (rotated) in the direction of the arrow in FIG. 2 by the frictional force with the pressure roller 31.
Thereafter, the recording medium P is fed from the paper feeding units 12 to 14, and an unfixed image is carried on the recording medium P by the image forming unit 4. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 while being guided by the guide plate 35, and the nip portion between the fixing film 21 and the pressure roller 31 in a pressure contact state. To be sent to.
The toner image T is fixed on the surface of the recording medium P by the heating by the fixing film 21 heated by the heating plate 22 and the pressing force of the heating plate 22 (fixing film 21) and the pressure roller 31. Thereafter, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

Hereinafter, with reference to FIG. 4, the characteristic configuration and operation of the fixing device 20 according to the first embodiment will be described in detail.
In the first embodiment, the heating plate 22 is in contact with the pressure roller 31 via the fixing film 21, and the fixing device 20 is not released without releasing the pressure of the members 21, 22, 31. The infrared heater 25 can be inserted and removed. Specifically, when the holder 27 (second holding member) is attached to and detached from the holding member 24, the infrared heater 25 is inserted into and removed from the fixing device 20.
More specifically, when the infrared heater 25 is taken out of the fixing device 20 in order to perform maintenance of the infrared heater 25, first, screw fastening is released and one holder 27 is taken out from the holding member 24 (FIG. 4). This is the movement in the direction of the broken double arrow.) Thereafter, the infrared heater 25 is pulled out from the side from which the holder 27 is taken out (the movement in the direction of the white arrow in FIG. 4 and the movement to the right in FIG. 4). When a new infrared heater 25 (or a repaired infrared heater 25) is attached to the fixing device 20, an operation opposite to the above-described extraction operation is performed.
As described above, the fixing device 20 according to the first embodiment has a very high rise time, and without providing a mechanism for releasing the pressure between the heating plate 22 (fixing film 21) and the pressure roller 31. With a relatively simple configuration, the replaceability and maintainability of the infrared heater 25 with a relatively high replacement frequency can be improved.

  In the first embodiment, referring to FIG. 2, an infrared heater 25 as a heating unit is installed separately from the heating plate 22 (contact member). That is, the infrared heater 25 is installed with a certain gap from the heating plate 22. Thereby, even when the fixing device 20 is transported in a state where the heating plate 22 is in pressure contact with the pressure roller 31 via the fixing film 21, the infrared heater 25 receives vibration directly from the heating plate 22 or the like. Therefore, damage to the infrared heater 25 can be suppressed. Further, even when the jammed recording medium P is taken out at the position of the fixing device 20 with the heating plate 22 pressed against the pressure roller 31 through the fixing film 21 (when jammed), etc. Since the impact that the infrared heater 25 receives directly from the nip portion by the jam processing operation can be reduced, the damage of the infrared heater 25 can be suppressed.

In the first embodiment, referring to FIG. 5, the length M of the heating plate 22 (contact member) in the conveyance direction of the recording medium is set to be longer than the nip amount N of the nip portion. (M> N).
As a result, on the outlet side of the nip portion (area A in FIG. 5), the fixing film 21 is deformed into a convex shape toward the pressure roller 31 according to the shape of the pressure roller 31. Therefore, the recording medium P after the fixing process is sent in a direction (in the direction of arrow Y11 in FIG. 5) to be separated from the fixing film 21. That is, it is possible to improve the conveyance separation at the time of sending out the nip portion.

Moreover, in this Embodiment 1, with reference to FIG. 6, the heating plate 22 (contact member) is thickness t1 in the width direction center part (it is the thickness of the direction facing the infrared heater 25). It is formed so that the thickness t2 at both ends in the width direction is different. Specifically, the thickness t1 at the center in the width direction is formed to be thicker than the thickness t2 at both ends in the width direction (t1> t2).
Thereby, since the heating efficiency of the width direction both ends in the heating plate 22 becomes higher than the heating efficiency of the width direction center portion, heat is dissipated from both ends of the heating plate 22 and the temperature at both ends decreases. Can be deterred. That is, the temperature distribution in the width direction of the heating plate 22 is made uniform, and the occurrence of uneven fixing is reduced.

  In the first embodiment, the thickness t2 at both ends is made thinner than the thickness t1 at the center in consideration of heat dissipation from both ends of the heating plate 22. On the other hand, when the nip amount at the center portion is smaller than the nip amounts at both ends, the fixing property at the center portion is deteriorated, or many small size papers having a small size in the width direction are passed. In the case where the temperature at both ends excessively increases, the thickness t1 at the center is made thinner than the thickness t2 at both ends so that the heating efficiency at the center is higher than that at both ends. Can do.

Moreover, in this Embodiment 1, with reference to FIG. 7, the size (it is an area of the opposing surface which opposes the infrared heater 25) and width | variety in the reflecting plate 23 (reflecting member) in the width direction center part 23a. It is formed so that the size 23b at both ends in the direction is different. Specifically, the width direction central portion 25a is formed to be smaller than the width direction end portions 23b.
Thereby, the amount of infrared rays reflected by the reflecting plate 23 at both ends 23b in the width direction is larger than that at the center portion 25a in the width direction. Therefore, the heating efficiency of the both ends of the heating plate 22 in the width direction is higher than the heating efficiency of the center portion in the width direction, and heat is dissipated from both ends of the heating plate 22 to suppress the problem that the temperatures at both ends are lowered. be able to. That is, the temperature distribution in the width direction of the heating plate 22 is made uniform, and the occurrence of uneven fixing is reduced.

In the first embodiment, the amount of infrared light reflected by the reflection plate 23 at both ends in the width direction is larger than that at the center portion in the width direction depending on the area of the opposing surface of the reflection plate 23. On the other hand, the reflection amount of infrared rays by the reflection plates 23 at both ends in the width direction can be reduced even by forming the reflectivity for infrared rays at both ends in the width direction of the reflection plate 23 to be higher than that at the center in the width direction. It can be made more than the thing of the width direction center part. In this case, the same effect as described above can be obtained. In addition, the difference in the reflectance in the reflecting plate 23 can be set by using materials having different reflectances or adjusting the degree of mirror finish.
In the first embodiment, in consideration of heat dissipation from both ends of the heating plate 22, the reflecting plates 23b at both ends are made larger than the reflecting plate 23a at the center. On the other hand, when the nip amount at the center portion is smaller than the nip amounts at both ends, the fixing property at the center portion is deteriorated, or many small size papers having a small size in the width direction are passed. In the case where the temperature at both ends excessively increases, the central reflector 23a is made larger than the reflectors 23b at both ends so that the heating efficiency at the center is higher than those at both ends. Can do.

Furthermore, in the first embodiment, with reference to FIG. 2, an optical sensor 40 as a detecting unit is disposed at a position facing the outer peripheral surface of the fixing film 21. The optical sensor 40 optically detects a marker formed on the fixing film 21 (for example, a white marker formed on the black fixing film 21), and rotates the rotation speed (driving) of the fixing film 21. Speed). An encoder or the like can also be used as the detection means.
On the other hand, the drive motor that drives the pressure roller 31 is configured so that the rotation speed of the pressure roller 31 can be varied. Therefore, this drive motor also functions as a variable means for changing the drive speed of the fixing film 21.
Then, based on the detection result detected by the optical sensor 40, the drive motor as the variable means is controlled so that the rotation speed of the fixing film 21 is stabilized. As a result, fluctuations in the rotational speed of the fixing film 21 can be reduced, so that the fixability of the output image and the transportability of the recording medium P are stabilized.

  Further, when the value detected by the optical sensor 40 serving as the detecting means is equal to or less than a predetermined value, there is a possibility that slip occurs in the rotational driving of the fixing film 21 and local overheating occurs in the fixing film 21. As a certain thing, the electric power supplied to the infrared heater 25 is interrupted | blocked. Thereby, even when an abnormality occurs in the driving operation, the thermal damage of the fixing film 21 can be suppressed.

  As described above, in the first embodiment, the heating plate 22 (contact member) that is heated by the infrared heater 25 (heating means) to form the nip portion is pressed through the fixing film 21 (fixing member). The infrared heater 25 can be inserted into and removed from the fixing device 20 while being in contact with the roller 31 (pressure member). Thereby, the start-up time of the fixing device 20 is short, and the replaceability and maintenance performance of the infrared heater 25 can be improved with a relatively simple configuration.

  In the first embodiment, the present invention is applied to a fixing device using a pressure roller as a pressure member. However, the present invention is applied to a fixing device using a pressure belt or a pressure pad as a pressure member. The present invention can also be applied. In this case, the same effect as that of the first embodiment can be obtained.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a configuration diagram illustrating the fixing device according to the second embodiment, and corresponds to FIG. 2 according to the first embodiment. The fixing device according to the second embodiment is the same as that of the first embodiment, in which the heating means 25 is spaced from the contact member 22 in that the heating means 25 is close to the contact member 22. It is different from the one.

As shown in FIG. 8, the fixing device 20 according to the second embodiment also has a fixing film 21, a heating plate 22, a reflecting plate 23, a holding member 24, an infrared heater 25, an additional heater, as in the first embodiment. It is composed of a pressure roller 31 and the like.
Here, in the second embodiment, an infrared heater 25 as a heating unit is installed in proximity to the heating plate 22 (contact member). Thus, since the infrared heater 25 is installed with almost no gap with respect to the heating plate 22, the heating efficiency of the heating plate 22 is improved. Even in such a case, compared to the case where the heater 25 is a member that directly forms the nip portion (a conventional on-demand fixing device), the vibration that the heater 25 receives during transportation. And the impact received during jam processing can be reduced.

  Also, the fixing device 20 in the second embodiment is similar to that in the first embodiment, with the heating plate 22 in contact with the pressure roller 31 via the fixing film 21, the members 21, The infrared heater 25 can be inserted into and removed from the fixing device 20 without releasing the pressures 22 and 31. Specifically, when the holder 27 (second holding member) is attached to and detached from the holding member 24, the infrared heater 25 is inserted into and removed from the fixing device 20. However, in the second embodiment, since the infrared heater 25 is provided close to the heating plate 22, the insertion / removal operation of the infrared heater 25 is performed so as to slide on the surface of the heating plate 22.

  As described above, also in the second embodiment, as in the first embodiment, the heating plate 22 (contact member) that is heated by the infrared heater 25 (heating means) to form the nip portion is the fixing film 21. The infrared heater 25 can be inserted into and removed from the fixing device 20 in a state of being in contact with the pressure roller 31 (pressure member) via the (fixing member). Thereby, the start-up time of the fixing device 20 is short, and the replaceability and maintenance performance of the infrared heater 25 can be improved with a relatively simple configuration.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram illustrating a fixing device installed in the image forming apparatus of FIG. 1. FIG. 3 is a view of a part of the fixing device of FIG. 2 as viewed in the width direction. It is a figure which shows the state by which a heating means is inserted / removed. FIG. 3 is a partially enlarged view showing the vicinity of a nip portion of the fixing device of FIG. 2. It is the figure which looked at the contact member in the width direction. It is the figure which looked at the reflective member in the width direction. It is a block diagram which shows the fixing device in Embodiment 2 of this invention.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing film (fixing member),
22 heating plate (contact member),
23 reflector (reflecting member),
24 holding member,
25 Infrared heater (heating means),
27 holder (second holding member),
28 compression springs,
31 Pressure roller (pressure member),
40 Optical sensor (detection means), P recording medium.

Claims (21)

An endless fixing film having a flexibility while heating and melting the toner image;
A contact member fixed inside the fixing film to form a nip portion by contacting the pressure member through the fixing film;
Heating means for heating the contact member;
While holding the heating means, both ends thereof are supported by the side plates of the apparatus, and are formed in a circular shape so as to face the inner peripheral surface of the fixing film at a position excluding the nip portion, and guide the fixing film. Members,
A second holding member that is screwed to an end of the holding member in the width direction and has a hole that engages with the heating unit;
With
Said heating means, said second held by the holding member via the holding member, abuts the abutment member said pressure member via the fixing film by attachment and detachment of the second holding member with respect to the holding member A fixing device, wherein the fixing device is inserted into and removed from the device in a state where the operation is performed .   The fixing device according to claim 1, wherein the contact member is held by the holding member. The heating means is an infrared heater,
A reflection member that reflects the infrared rays emitted from the infrared heater and increases the heating efficiency of the contact member;
The fixing device according to claim 1, wherein the reflecting member is held by the holding member.   The fixing device according to claim 3, wherein the reflection member is installed on a side opposite to a side where the infrared heater faces the contact member.   The fixing device according to claim 4, wherein the reflection member is formed so that a reflectance with respect to infrared rays at a central portion in the width direction is different from a reflectance with respect to infrared rays at an end portion in the width direction.   The fixing device according to claim 4, wherein the reflection member is formed so that a size at a central portion in the width direction is different from a size at an end portion in the width direction.   The fixing device according to claim 3, wherein the contact member includes an absorbing member that absorbs infrared rays on a side facing the infrared heater.   The fixing device according to claim 3, wherein the heating unit is a carbon heater.   9. The carbon heater is formed such that the amount of radiant heat generated in a direction facing the contact member is larger than the amount of radiant heat generated in a direction orthogonal to the direction. The fixing device described.   The fixing device according to claim 1, wherein the contact member is formed so that a surface facing the pressure member has a planar shape.   The fixing device according to claim 1, wherein the contact member is coated with a fluororesin on a surface on which the fixing film is slidably contacted.   The fixing device according to claim 1, wherein the contact member is formed such that a thickness at a central portion in the width direction is different from a thickness at an end portion in the width direction.   The fixing device according to claim 1, wherein the contact member is formed so that a length in a conveyance direction of the recording medium is longer than a nip amount of the nip portion. . The pressure member is rotatably installed at a fixed position in the apparatus,
The fixing device according to claim 1, wherein the contact member is biased toward the pressure member.   The fixing device according to claim 1, wherein the heating unit is disposed apart from the contact member. The fixing device according to claim 1, wherein the fixing film is driven by a frictional force with the pressure member that is driven in a predetermined direction. The fixing device according to claim 1, further comprising a detecting unit that detects a driving speed of the fixing film. Comprising variable means for varying the driving speed of the fixing film;
The fixing device according to claim 17, wherein the variable unit is controlled based on a detection result of the detection unit. 19. The fixing device according to claim 17, wherein when the value detected by the detection unit is equal to or less than a predetermined value, the power supplied to the heating unit is cut off. With heating and melting bets toner image, a fixing film of endless flexible,
A contact member fixed inside the fixing film to form a nip portion by contacting the pressure member through the fixing film;
Heating means for heating the contact member;
A guide member that is formed in a circular shape so as to face the inner peripheral surface of the fixing film at a position excluding the nip portion, guides the fixing film, and has both ends supported by side plates of the apparatus;
A screw fastened to the widthwise end of the guide member, and a holder formed with a hole to engage the end of the heating means;
With
The heating means is directly held by the holder without contacting the guide member, and the contact member is in contact with the pressure member through the fixing film by attaching or detaching the holder to or from the guide member. A fixing device which is inserted into and removed from the device. 21. An image forming apparatus comprising the fixing device according to claim 1.

Images