JP2011048134A - Fixing device and image forming apparatus - Google Patents

Abstract

Fixing in which the start-up time of the apparatus is short, the rotation of the fixing member can be detected and the rotation speed of the fixing member can be stabilized without increasing the size and cost of the apparatus with a relatively simple configuration. An apparatus and an image forming apparatus are provided.
An endless fixing member having a plurality of through-holes formed at equal intervals along the rotation direction, an infrared heater facing the inner peripheral surface of the fixing member, and an outer peripheral surface of the infrared heater. A reflection plate 25 that covers a part, and detection means 50 that detects light emitted from the infrared heater 23 and passing through a plurality of through holes formed in the fixing member 21. Then, the rotation speed of the fixing member 21 is obtained from the light detection interval detected by the detection means 50.
[Selection] Figure 2

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, and in particular, fixing members such as a fixing film and a fixing belt using an infrared heater. The present invention relates to a fixing device and an image forming apparatus that are locally heated.

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).
The fixing device disclosed in Patent Document 1 includes a fixing film as a fixing member, a pressure roller (pressure rotator), a heating plate (contact member), an infrared heater, a reflecting plate, and the like. The heating plate contacts the pressure roller through the fixing film to form a nip portion, and is heated by an infrared heater installed on the inner peripheral surface side of the fixing film to heat the fixing film at the position of the nip portion. . 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.
Here, in order to improve the heating efficiency of the fixing film (or heating plate) by the infrared heater, a reflection plate is installed so as to cover a part of the outer peripheral surface of the infrared heater in the width direction. That is, a part of the fixing film (or heating plate) is locally irradiated by light directly irradiated by the infrared heater and light irradiated after being emitted from the infrared heater and reflected by the reflecting plate. To be heated.
The pressure roller is rotationally driven by a drive motor, and the fixing film is driven and rotated by frictional resistance with the pressure roller at the position of the nip portion.

  On the other hand, in Patent Document 2 and the like, for the purpose of detecting an abnormality of a fan motor installed in the vicinity of the fixing device, it is emitted from a fixing heater installed in the fixing device, passes through the fan motor, and becomes a photo sensor. A technique for detecting incident light is disclosed.

In the above-described conventional on-demand type fixing device, the rotating fixing film is locally heated by an infrared heater, so that the device has an abnormality such as when the fixing film slips. When the rotation of the fixing film stops, the fixing film is heated by overheating because part of the fixing film is intensively heated by an infrared heater that is controlled as if no abnormality has occurred in the device. There was a possibility of damage.
Also, when the outer diameter of the pressure roller changes due to thermal expansion, the linear velocity of the fixing film (or pressure roller) at the nip changes, and the conveyance speed of the recording medium passing through the nip May change, or a fixing failure may occur on the fixed image.

  The present invention has been made to solve the above-described problems. The start-up time of the apparatus is short, and the fixing member does not rotate with a relatively simple configuration without increasing the size and cost of the apparatus. Another object of the present invention is to provide a fixing device and an image forming apparatus in which the rotation speed of the fixing member can be stabilized.

  In the fixing device according to the first aspect of the present invention, the toner image is heated and melted and fixed on the recording medium by rotating in a predetermined direction, and a plurality of through holes are provided at equal intervals along the rotation direction. The formed endless fixing member, a pressure rotator that forms a nip portion that is pressed against the fixing member to convey the recording medium, and heats the fixing member so as to face the inner peripheral surface of the fixing member. An infrared heater that is disposed so as to cover a part of the outer peripheral surface of the infrared heater over the width direction, and a reflector that reflects the light emitted from the infrared heater and irradiates the fixing member; Detecting means for detecting light emitted from the infrared heater and passing through the plurality of through-holes formed in the fixing member while facing the infrared heater via a fixing member. From the detection interval of light detected by the step is intended to determine the rotational speed of the fixing member.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the pressure rotator is rotationally driven by a driving source capable of changing a driving speed, and the fixing member is The drive source is driven to rotate by frictional resistance with the pressure rotator, the rotation speed of the fixing member is obtained from the light detection interval detected by the detection means, and the rotation speed becomes a predetermined value. The speed is variably controlled.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the rotation speed of the fixing member is obtained from the light detection interval detected by the detection means. When the rotational speed becomes a predetermined value or less, the energization to the infrared heater is stopped.

  The fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the infrared heater is always energized while the fixing member is rotating. It is controlled as follows.

  The fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the plurality of through holes are formed in a non-sheet passing region of the fixing member. Is.

  The fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the fixing member is a flexible fixing film, wherein the fixing film is a fixing film. A contact member fixed to the inner peripheral surface side of the fixing film to form the nip portion in contact with the pressure rotator via the infrared heater and the reflection plate; The fixing film is disposed on the inner peripheral surface side of the fixing film and upstream of the nip portion in the rotation direction of the fixing film.

  An image forming apparatus according to a seventh aspect of the present invention includes the fixing device according to any one of the first to sixth aspects.

  In the present application, the “sheet passing area” is defined as a range in the width direction (a direction perpendicular to the sheet passing direction) of the maximum size recording medium that can be passed by the image forming apparatus. The “non-sheet passing area” is defined as an area outside the range of the “sheet passing area”.

  In the present invention, light emitted from an infrared heater and passed through a plurality of through holes formed in the fixing member is detected, and the rotation speed of the fixing member is obtained from the detection interval of these lights. This makes it possible to detect the rotation failure of the fixing member and stabilize the rotation speed of the fixing member without increasing the size and cost of the device with a relatively simple configuration with a short startup time of the device. An apparatus and an image forming apparatus can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment 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 when viewed in the width direction. It is a figure which shows the state by which an infrared heater is inserted / removed. It is a perspective view which shows a fixing film. It is a figure which shows the various forms of a reflecting plate.

Embodiment.
Hereinafter, embodiments 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.

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 rotator 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 has been 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 view showing the fixing device 20 and a cross-sectional view 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 23 is inserted into and removed from the fixing device 20. FIG. 5 is a cross-sectional view showing a fixing film 21 as a fixing member.

  As shown in FIG. 2, the fixing device 20 includes a fixing film 21 as a fixing member, a pressure plate 22 as a contact member, an infrared heater 23, a reflection plate 25, a holding member 24, and a pressure roller as a pressure rotator. 31, a temperature sensor 40 (thermopile), a light detection sensor 50 (photosensor) 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-like member, and rotates in the direction of an arrow (clockwise) in FIG. As a material of the fixing film 21, polyimide, polyamide, fluororesin, metal, or the like can be used. In order to secure releasability (peelability) with respect to toner T (toner image), PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide is provided on the surface layer of 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 23 (heating means), a pressure plate 22, a reflection plate 25, a holding member 24, and the like are fixed. The fixing film 21 is pressed by the pressure plate 22 held by the holding member 24 to form a nip portion with the pressure roller 31.

The pressure plate 22 as a contact member is a metal plate (or a plate made of ceramic or polyimide resin) and is held by a holding member 24 and is in contact with the pressure roller 31 via the fixing film 21. A desired nip portion is formed.
In the present embodiment, the opposing surface of the pressure 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 pressure plate 22 in the present embodiment is coated with a fluororesin on the surface where the fixing film 21 is in sliding contact. 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 pressure plate 22 fixedly supported by the fixing device 20.

  The infrared heater 23 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 fixing film 21 is heated by the infrared heater 23 whose output is controlled by the power supply unit 63 (control unit 61) of the apparatus main body 1, and heat is applied to the toner image T on the recording medium P from the surface of the fixing film 21. . The output control of the infrared heater 23 is performed based on the detection result of the film surface temperature by the temperature sensor 40 (thermopile) facing the surface of the fixing film 21. In addition, the temperature of the fixing film 21 (fixing temperature) can be set to a desired temperature by such output control of the infrared heater 23.

The reflection plate 25 is disposed on the side opposite to the side facing the fixing film 21 with respect to the infrared heater 23 (the left side of the infrared heater 23 in FIG. 2).
Specifically, the reflecting plate 25 is formed in a semi-cylindrical shape, and a part of the outer peripheral surface of the infrared heater 23 (the side not facing the inner peripheral surface of the fixing film 21) extends in the width direction (the paper surface of FIG. 2). In the vertical direction). The reflection plate 25 is formed by applying gold plating or aluminum vapor deposition on a glass substrate and reflecting the infrared rays emitted from the infrared heater 23 on the reflection surface. Since most of the infrared rays (light) reflected by the reflecting plate 25 are irradiated to the fixing film 21, the heating efficiency of the fixing film 21 is improved.

Here, in the fixing device 20 in the present embodiment, the infrared heater 23 (and the reflection plate 25) is on the inner peripheral surface side of the fixing film 21 and on the upstream side with respect to the nip portion (the rotation of the fixing film 21). It is disposed on the upstream side in the direction). In the case where the fixing film 21 is locally heated at the position of the nip portion, the fixing temperature becomes higher and the glossiness of the image does not increase as it goes downstream in the nip portion. When the fixing film 21 is locally heated on the upstream side of the nip portion as in the present embodiment, the cooling efficiency with respect to the toner increases as it proceeds downstream in the nip portion, so that the glossiness of the image can be improved. .
In the present embodiment, an absorbing member that absorbs infrared rays may be provided on the inner peripheral surface (the side facing the infrared heater 23) of the fixing film 21. Specifically, black coating can be applied to the inner peripheral surface of the fixing film 21. Thereby, the infrared absorption rate in the fixing film 21 is improved, and the heating efficiency of the fixing film 21 is increased.

With reference to FIG. 3, the holding member 24 integrally holds the pressure plate 22, the infrared heater 23, and the reflection plate 25. 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 23 is held by the holding member 24 via the holder 27. 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 23. Then, as shown in FIG. 4, by removing the holder 27 from the holding member 24, only the infrared heater 23 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 pressure 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 62 as a drive source, and the fixing film 21 is driven (driven) in the arrow direction of FIG. 2 by the frictional force with the pressure roller 31. Become. With such a configuration, the driving 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 rotating body is formed by forming an elastic layer 33 on a core metal 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 the arrow direction (counterclockwise direction) in FIG. 2 by a drive motor 61 as a drive source.
The drive motor 61 (drive source) in the present embodiment is a variable speed drive motor that can vary the drive speed.

  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 (energized) to the infrared heater 23 from the power supply unit 63 controlled by the control unit 61, and a drive motor 62 (drive source) controlled by the control unit 61 is provided. ) Starts to rotate 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.
Then, the toner on the surface of the recording medium P is heated by the fixing film 21 heated by the infrared heater 23 at a position upstream of the nip portion and the pressing force of the pressure plate 22 (fixing film 21) and the pressure roller 31. The image T is fixed. Thereafter, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

Hereinafter, the characteristic configuration and operation of the fixing device 20 in the present embodiment will be described in detail.
With reference to FIGS. 3 to 5, a plurality of through holes 21 a are formed in the fixing film 21 as a fixing member at equal intervals along the rotation direction. That is, a plurality of through holes 21 a having the same hole diameter are formed in the circumferential direction of the fixing film 21 at the same pitch interval.
The plurality of through holes 21a are formed in the non-sheet passing region N in the fixing film 21, as shown in FIG. Here, the non-sheet passing area N is a “sheet passing area” that is a range in the width direction (a direction perpendicular to the sheet passing direction) of the maximum size recording medium P that can be passed by the image forming apparatus 1. It is an area outside the range of “M”. Therefore, the through hole 21a formed in the fixing film 21 does not affect the recording medium P conveyed to the paper passing area M of the nip portion. That is, since the through hole 21a of the fixing film 21 is formed in the non-sheet passing region N, the image quality such as the fixing property of the fixed image and the transportability of the recording medium P are not deteriorated.

  Further, referring to FIG. 2 and FIG. 3, a light detection sensor 50 (photo sensor) as a detection means is installed at a position facing the infrared heater 23 through the fixing film 21. The light detection sensor 50 (detection means) is for detecting light (infrared rays) emitted from the infrared heater 23 and passing through the plurality of through holes 21 a formed in the fixing film 21. Then, the rotation speed of the fixing film 21 is obtained from the detection interval of light (infrared rays) detected by the light detection sensor 50 (detection means).

Specifically, when the light detection sensor 50 detects light (infrared rays) incident on the light detection sensor 50 that has been emitted from the infrared heater 23 and passed through the through hole 21 a, the information is sent to the control unit 61. Then, the calculation unit of the control unit 61 divides the pitch (distance) between the adjacent through holes 21a by the detection interval (time) of the light that has passed through each of the adjacent through holes 21a. Linear velocity) is calculated. The rotational speed (linear speed) of the fixing film 21 obtained by the control unit 61 is obtained by averaging a plurality of calculation results (a plurality of data collected within a predetermined time) calculated as described above. can do.
Here, in order to ensure the detection of the rotational speed (linear speed) of the fixing film 21, the infrared heater 23 is always energized (turned on) while the fixing film 21 is rotating. Is controlled. This is because if the infrared heater 23 is controlled to be turned on / off, the amount of data that could not be detected by the light detection sensor 50 when the power to the infrared heater 23 was turned off was detected as the rotation speed detection error of the fixing film 21. Because it becomes. Even when the infrared heater 23 is controlled to be turned on / off, an infrared ray is calculated by performing an arithmetic process so that data that cannot be detected by the light detection sensor 50 can be canceled when the energization of the infrared heater 23 is turned off. The rotational speed of the fixing film 21 can be detected with high accuracy almost the same as when the heater 23 is always turned on.

Then, as described above, after the rotation speed of the fixing film 21 is obtained from the light detection interval detected by the light detection sensor 50 (detection means), the result is fed back so that the rotation speed of the fixing film 21 is predetermined. The drive speed of the variable speed drive motor 62 is variably controlled so as to be a value (or within a predetermined range).
By performing such control, the linear velocity of the fixing film 21 (or the pressure roller 31) in the nip portion changes even when the outer diameter of the pressure roller 31 is varied due to thermal expansion. Will be suppressed. That is, since the rotation speed of the fixing film 21 is feedback-controlled, the linear speed of the fixing film 21 (or the pressure roller 31) in the nip portion is substantially constant, and the conveyance speed of the recording medium P that passes through the nip portion. Can be eliminated, and fixing defects can occur on fixed images.

  In the present embodiment, after the rotation speed of the fixing film 21 is obtained from the light detection interval detected by the light detection sensor 50 (detection means), the result (rotation speed) becomes a predetermined value or less. In addition, the power supply to the infrared heater 23 is controlled to stop. Specifically, when the calculated rotation speed of the fixing film 21 is zero (or a numerical value close thereto) during normal operation, slipping or the like occurs in the fixing film 21 and the fixing film 21 is in a rotation stopped state (or Therefore, a part of the fixing film 21 (at a position facing the infrared heater 23) is intensively heated and the fixing film 21 is thermally damaged due to excessive temperature rise. In order to prevent such a problem, the energization from the power source 63 to the infrared heater 23 is interrupted. Thereby, it is possible to provide the fixing device 20 with higher safety.

Here, in the present embodiment, as shown in FIG. 6A, the cross-sectional shape of the reflecting plate 25 is formed in a substantially arc shape. By arranging the infrared heater 23 at the focal position, the reflection efficiency of the reflector 25 (the degree to which the light of the infrared heater 23 is efficiently irradiated onto the fixing film 21) can be increased. The broken line arrow in the figure is the optical path of the reflected light.
In addition, the cross-sectional shape of the reflecting plate 25 is not limited to that of the present embodiment, and for example, it can be as shown in FIGS. In particular, when a heater having a light distribution is used, a reflector 25 having an intersection angle of 90 degrees as shown in FIG. 6C is used, and the perpendicular of the light distribution direction of the heater 23 is a bisector of the angle. By arrange | positioning so that it may become, the reflected light from the reflector 25 can be equalize | homogenized.

  As described above, in the present embodiment, light emitted from the infrared heater 23 and passing through the plurality of through holes 21a formed in the fixing film 21 (fixing member) is detected, and the light of these lights is detected. The rotation speed of the fixing film 21 is obtained from the detection interval. Thereby, the start-up time of the fixing device 20 is short, and the fixing device 20 can detect rotation failure of the fixing film 21 with a relatively simple configuration without increasing the size and cost, and the rotation speed of the fixing film 21. Can be stabilized.

  In the present embodiment, the present invention is applied to a fixing device using a pressure roller as a pressure rotator and a fixing film as a fixing member. However, a pressure belt or the like is used as the pressure rotator. The present invention can also be applied to a conventional fixing device and a fixing device using a fixing belt as a fixing member. Also in this case, the same effect as in the present embodiment can be obtained.

  In the present embodiment, the present invention is applied to the fixing device 20 installed in the monochrome image forming apparatus 1. However, the present invention is naturally applied to the fixing device installed in the color image forming apparatus. Can be applied.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing film (fixing member),
21a through hole,
22 pressure plate (contact member),
23 Infrared heater,
25 reflector,
31 Pressure roller (pressure rotating body),
40 temperature sensor,
50 light detection sensor (detection means),
62 Drive motor (drive source), P recording medium.

JP 2008-129092 A JP 2006-106464 A

Claims (7)

An endless fixing member that rotates in a predetermined direction and heats and melts the toner image to be fixed on the recording medium, and has a plurality of through holes formed at equal intervals along the rotation direction;
A pressure rotator that forms a nip portion in which a recording medium is conveyed in pressure contact with the fixing member;
An infrared heater that heats the fixing member facing the inner peripheral surface of the fixing member;
A reflector that is disposed so as to cover a part of the outer peripheral surface of the infrared heater over the width direction, reflects the light emitted from the infrared heater, and irradiates the fixing member;
Detecting means for detecting light emitted from the infrared heater and passing through the plurality of through holes formed in the fixing member while facing the infrared heater via the fixing member;
With
A fixing device characterized in that a rotation speed of the fixing member is obtained from a light detection interval detected by the detecting means. The pressure rotator is rotationally driven by a drive source capable of varying a driving speed, and the fixing member is driven to rotate by frictional resistance with the pressure rotator,
The drive speed of the drive source is variably controlled so that the rotation speed of the fixing member is obtained from the light detection interval detected by the detection means, and the rotation speed becomes a predetermined value. The fixing device according to 1.   The rotation speed of the fixing member is obtained from the light detection interval detected by the detection means, and control is performed to stop energization of the infrared heater when the rotation speed becomes a predetermined value or less. The fixing device according to claim 1 or 2.   4. The fixing device according to claim 1, wherein the infrared heater is controlled so as to be always energized while the fixing member is rotating. 5.   The fixing device according to claim 1, wherein the plurality of through holes are formed in a non-sheet passing region of the fixing member. The fixing member is a fixing film having flexibility,
A contact member fixed on the inner peripheral surface side of the fixing film to form the nip portion by contacting the pressure rotator through the fixing film;
The infrared heater and the reflection plate are disposed on the inner peripheral surface side of the fixing film and upstream of the nip portion in the rotation direction of the fixing film. The fixing device according to claim 5.   An image forming apparatus comprising the fixing device according to claim 1.

Images