JP2007292861A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device designed so as to securely prevent toner from clinging to a non-contact temperature sensor, and to provide an image forming apparatus. <P>SOLUTION: The fixing device 90 has a fixing roller 91 and a pressure roller 92 rotated in firm contact with each other, and a heater 93 for heating the fixing roller 91. The fixing device 90 passes a recording medium P holding thereon an unfixed image containing toner T, through a nip part N formed by the firm contact of the fixing roller 91 and a pressure roller 92. The fixing device then applies heat and pressure to the recording medium P, thereby fixing the unfixed image to the recording medium P. Here, the fixing device 90 is provided with the non-contact temperature sensor 94 disposed near the fixing roller 91 and is used to detect the surface temperature of the fixing roller 91, without contacting the surface. A gas is caused to flow between the non-contact temperature sensor 94 and fixing roller 91, thereby preventing the toner, floating in space, from sticking to the temperature sensor 94. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Image forming apparatuses such as printers, copiers, and facsimiles that employ an electrophotographic method form an image made of toner on a recording medium such as paper by a process of exposure, development, transfer, and fixing (for example, Patent Documents). 1). Such an image forming apparatus includes a fixing device that fixes the toner image on the recording medium by heating and pressurizing the toner image formed of toner onto a recording medium such as paper that is carried in an unfixed state. It has been.

  Such a fixing device generally has a columnar or cylindrical fixing roller and a pressure roller that are pressed against each other and a halogen heater that heats the fixing roller. By passing a recording medium through a nip formed by the pressure contact between the fixing roller and the pressure roller, the recording medium is heated and pressurized to record a toner image formed on the recording medium. Fix to media.

Further, such a fixing device is provided with a temperature sensor for detecting the surface temperature of the fixing roller, and the driving of the heater is controlled based on the detection of the surface temperature by the temperature sensor.
As such a temperature sensor, there are a contact temperature sensor such as a thermistor and a non-contact temperature sensor such as an infrared sensor. Among these, since the non-contact temperature sensor does not contact the surface of the heating roller, the durability of the heating roller can be improved. Moreover, durability of the temperature sensor can be improved.
However, there is a problem in that the toner floating in the fixing device adheres to the non-contact temperature sensor due to the influence of the air flow generated by the rotation of the fixing roller, and the sensitivity of the non-contact temperature sensor is lowered.

JP 2002-139552 A

  An object of the present invention is to provide a fixing device and an image forming apparatus that reliably prevent toner from adhering to a non-contact temperature sensor.

Such an object is achieved by the present invention described below.
The fixing device of the present invention includes a fixing member and a pressure member that are pressed against each other and a heater that heats the fixing member, and a nip formed by the pressure contact between the fixing member and the pressure member. A fixing device for fixing the unfixed image to the recording medium by passing a recording medium carrying an unfixed image containing toner and heating and pressurizing the recording medium;
A non-contact temperature sensor provided in the vicinity of the fixing member for detecting the surface temperature of the fixing member in a non-contact manner;
It is configured to prevent the toner floating in the space from adhering to the non-contact temperature sensor by flowing gas through the space between the non-contact temperature sensor and the fixing member. Features.
Thereby, it is possible to effectively prevent the toner floating in the cover member from adhering to the non-contact temperature sensor.

In the fixing device of the present invention, it is preferable that the gas is circulated from the vicinity of the non-contact temperature sensor toward the fixing member.
Thereby, it is possible to effectively prevent the toner floating in the cover member from adhering to the non-contact temperature sensor.
In the fixing device of the present invention, it is preferable that the gas is circulated from the vicinity of the non-contact temperature sensor toward the downstream side of the nip portion in the conveyance direction of the recording medium.
Thereby, it is possible to effectively prevent the toner floating in the cover member from adhering to the non-contact temperature sensor.

The fixing device of the present invention includes a fixing member and a pressure member that are pressed against each other and a heater that heats the fixing member, and a nip formed by the pressure contact between the fixing member and the pressure member. A fixing device for fixing the unfixed image to the recording medium by passing the recording medium carrying the unfixed image containing toner and heating and pressurizing the recording medium,
A cover member disposed so as to cover at least a part of the outer periphery of the fixing member and having an opening;
A non-contact temperature sensor provided in the vicinity of the opening and detecting the surface temperature of the fixing member in a non-contact manner;
By introducing and circulating gas from the opening to a space defined by the inner wall of the cover member and the outer peripheral surface of the fixing member, the toner floating in the space adheres to the non-contact temperature sensor. It is constituted so that it may prevent.
Thereby, it is possible to effectively prevent the toner floating in the cover member from adhering to the non-contact temperature sensor.

In the fixing device of the present invention, it is preferable that the gas is circulated from the opening to the nip portion toward the downstream side in the conveyance direction of the recording medium.
Thereby, it is possible to effectively prevent the toner floating in the cover member from adhering to the non-contact temperature sensor.
In the fixing device of the present invention, it is preferable that a duct is provided outside the cover member and communicates with the opening, and gas is introduced into the opening via the duct.
Thereby, a gas flow path can be formed.

The fixing device of the present invention preferably has a heating means for heating the gas in the duct so as to alleviate a temperature difference between the gas in the duct and the surface of the fixing member.
As a result, the heated gas flows from the vicinity of the non-contact temperature sensor toward the downstream side in the recording medium conveyance direction of the nip portion, thereby preventing a partial decrease in the surface temperature of the fixing member. Can do.

In the fixing device according to the aspect of the invention, it is preferable that the heating unit heats the gas in the duct using heat generated from the heater.
Thereby, it is not necessary to use a new heat source, and a reduction in manufacturing cost and power consumption can be achieved.
In the fixing device according to the aspect of the invention, it is preferable that the heating unit includes a heat radiating member that transmits heat generated from the heater and dissipates heat in the duct.
Thereby, the gas in a duct can be efficiently heated using the heat emitted from the heater.

In the fixing device of the present invention, it is preferable that the heat radiating member is formed integrally with the cover member.
Thereby, since the number of parts can be reduced, the design can be simplified and the manufacturing cost can be reduced.
In the fixing device of the present invention, it is preferable that the heat radiating member has a plurality of protrusions protruding into the duct.
Thereby, the contact area of a heat radiating member and gas can be enlarged, and gas can be heated more efficiently. As a result, a partial temperature drop on the surface of the fixing member can be prevented.

In the fixing device of the present invention, it is preferable that the non-contact temperature sensor has a thermopile.
Thereby, the temperature measurement error due to the displacement of the attachment position of the non-contact temperature sensor is less likely to occur, and the reliability of temperature detection can be improved. Further, the temperature detection response is also excellent, and the surface temperature of the fixing member can be detected more reliably.

In the fixing device according to the aspect of the invention, it is preferable that the non-contact temperature sensor is configured to perform temperature detection without being affected by the temperature of the gas.
Thereby, the temperature change of non-contact temperature sensor itself can be suppressed, and the reliability of a non-contact temperature sensor improves.
In the fixing device according to the aspect of the invention, it is preferable that the non-contact temperature sensor is disposed outside the cover member and detects the surface temperature of the fixing member through the opening.
Thereby, the temperature change of non-contact temperature sensor itself can be suppressed, and the reliability of a non-contact temperature sensor improves.
An image forming apparatus of the present invention is an image forming apparatus that forms an image on a recording medium by a series of image forming processes including exposure, charging, transfer, and fixing, and includes the fixing device of the present invention.
Thereby, an image forming apparatus excellent in fixing characteristics can be provided.

Preferred embodiments of a fixing device and an image forming apparatus having the same according to the present invention will be described below with reference to the accompanying drawings.
<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS.
1 is a schematic cross-sectional view of an overall configuration showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a schematic longitudinal cross-sectional view of the image forming apparatus shown in FIG. 1, and FIG. 4 is a schematic cross-sectional view showing a preferred embodiment of a fixing device provided in the image forming apparatus shown in FIG. 4, FIG. 4 is a schematic cross-sectional view of a non-contact temperature sensor, and FIG. 5 is a positional relationship between an exhaust duct and the fixing device. FIG. 6 is a schematic sectional view of the fixing device.

≪Image forming device≫
Prior to the fixing device of the present invention, an image forming apparatus including the fixing device of the present invention will be briefly described.
An image forming apparatus 10 according to this embodiment shown in FIG. 1 forms an image on a recording medium such as paper or an OHP sheet by a series of image forming processes including exposure, development, transfer, and fixing. As shown in FIG. 1, the image forming apparatus 10 has a photosensitive member 20 that carries an electrostatic latent image and rotates in the direction of the arrow in the figure. An exposure unit 40, a developing unit 50, a primary transfer roller 60, and a cleaning unit 75 are provided. In addition, the image forming apparatus 10 is provided with a paper feed tray 82 for storing a recording medium P such as paper at the bottom in FIG. The next transfer roller 80 and the fixing device 90 are sequentially arranged along the conveyance direction of the recording medium P. Further, in the image forming apparatus 10, when an image is formed on both sides of a recording medium, the recording medium P fixed on one side by the fixing device 90 is reversed and returned to the secondary transfer roller 80. The conveyance part 88 is provided.

Further, as shown in FIG. 1, an exhaust port 111 and an intake port 112 are formed in the main body case 11. Further, inside the main body case 11, a duct 97 that circulates gas from the intake port 112 to the fixing device 90 and an exhaust duct 13 that circulates gas from the fixing device 90 to the exhaust port 111 are disposed.
A fan 14 is disposed in the exhaust duct 13. By generating an air flow with the fan 14, the gas outside the main body case 11 is introduced into the fixing device 90 from the intake port 112 through the duct 97 and then exhausted from the exhaust port 111 through the exhaust duct 13.

Hereinafter, each part which comprises the image forming apparatus 10 as mentioned above is demonstrated sequentially.
The photoconductor 20 has a cylindrical conductive substrate (not shown) and a photosensitive layer (not shown) formed on the outer peripheral surface thereof, and can rotate around the axis in the direction of the arrow in FIG. It has become.
The charging unit 30 is a device for uniformly charging the surface of the photoconductor 20 by corona charging or the like.

The exposure unit 40 receives image information from a host computer such as a personal computer (not shown) and irradiates a laser on the uniformly charged photoreceptor 20 to form an electrostatic latent image. It is a device to do.
The developing unit 50 includes four developing devices, a black developing device 51, a magenta developing device 52, a cyan developing device 53, and a yellow developing device 54. These developing devices are converted into latent images on the photosensitive member 20. It is an apparatus that visualizes the latent image as a toner image, selectively used correspondingly. The black developing device 51 uses black (K) toner, the magenta developing device 52 uses magenta (M) toner, the cyan developing device 53 uses cyan (C) toner, and the yellow developing device 54 uses yellow (Y) toner.

  The YMCK developing unit 50 in the present embodiment is rotatable so that the above-described four developing devices 51, 52, 53, 54 are selectively opposed to the photoconductor 20. Specifically, in this YMCK developing unit 50, four developing devices 51, 52, 53, and 54 are respectively held by four holding portions 55a, 55b, 55c, and 55d of a holding body 55 that can rotate around a shaft 50a. The four developing devices 51, 52, 53, and 54 are selectively opposed to the photoconductor 20 while maintaining the relative positional relationship by the rotation of the holding body 55.

The intermediate transfer member 61 has an endless belt-like intermediate transfer belt 70, and this intermediate transfer belt 70 is stretched by a primary transfer roller 60, a driven roller 72, and a drive roller 71, and is rotated by the rotation of the drive roller 71. 1 is driven to rotate in the direction of the arrow shown in FIG.
The primary transfer roller 60 is a device for transferring a single color toner image formed on the photoconductor 20 to the intermediate transfer belt 70.

  On the intermediate transfer belt 70, a toner image of at least one of black, magenta, cyan, and yellow is carried. For example, when a full-color image is formed, four color toner images of black, magenta, cyan, and yellow are sequentially formed. The toner images are transferred to form a full-color toner image. In the present embodiment, the drive roller 71 also functions as a backup roller for the secondary transfer roller 80 described later. Further, the primary transfer roller 60, the driving roller 71, and the driven roller 72 are supported by the base body 73.

The secondary transfer roller 80 is a device for transferring a single-color or full-color toner image formed on the intermediate transfer belt 70 to a recording medium P such as paper, film, or cloth.
The fixing device 90 is a device for fusing the toner image to the recording medium P and fixing it as a permanent image by heating and pressing the recording medium P that has received the transfer of the toner image. The fixing device 90 includes the roller unit of the present invention. The fixing device 90 will be described in detail later.

The cleaning unit 75 has a rubber cleaning blade 76 that contacts the surface of the photoconductor 20 between the primary transfer roller 60 and the charging unit 30, and the toner image is transferred onto the intermediate transfer belt 70 by the primary transfer roller 60. Then, the toner remaining on the photoreceptor 20 is scraped off and removed by the cleaning blade 76.
The conveyance unit 88 reverses the front and back of the conveyance roller pair 88A and 88B for nipping and conveying the recording medium P fixed on one surface by the fixing device 90 and the conveyance medium pair 88A and 88B. And a conveyance path 88 </ b> C for guiding the registration roller 86. As a result, when an image is formed on both sides of the recording medium, the recording medium P fixed on one side by the fixing device 90 is reversed and returned to the secondary transfer roller 80.

Next, the operation of the image forming apparatus 10 configured as described above will be described.
First, in response to a command from a host computer (not shown), the photosensitive member 20, the developing roller (not shown) provided in the developing unit 50, and the intermediate transfer belt 70 start to rotate. The photoreceptor 20 is sequentially charged by the charging unit 30 while rotating.
The charged area of the photoconductor 20 reaches the exposure position as the photoconductor 20 rotates, and the exposure unit 40 forms a latent image corresponding to the image information of the first color, for example, yellow Y, in the area. .

The latent image formed on the photoconductor 20 reaches the development position as the photoconductor 20 rotates, and is developed with yellow toner by the yellow developing device 54. As a result, a yellow toner image is formed on the photoreceptor 20. At this time, in the YMCK developing unit 50, the yellow developing device 54 faces the photoconductor 20 at the developing position.
The yellow toner image formed on the photoconductor 20 reaches the primary transfer position (that is, the portion where the photoconductor 20 and the primary transfer roller 60 face each other) as the photoconductor 20 rotates. Transfer (primary transfer) is performed on the transfer belt 70. At this time, a primary transfer voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 60. During this time, the secondary transfer roller 80 is separated from the intermediate transfer belt 70.

The same processing as described above is repeatedly executed for the second color, the third color, and the fourth color, so that the toner images of the respective colors corresponding to the respective image signals are transferred onto the intermediate transfer belt 70 in an overlapping manner. The As a result, a full-color toner image is formed on the intermediate transfer belt 70.
On the other hand, the recording medium P is conveyed from the paper feed tray 82 to the secondary transfer roller 80 by the paper feed roller 84 and the registration roller 86.

  The full-color toner image formed on the intermediate transfer belt 70 reaches the secondary transfer position (that is, the portion where the secondary transfer roller 80 and the driving roller 71 face each other) as the intermediate transfer belt 70 rotates, and the secondary transfer. The image is transferred (secondary transfer) to the recording medium P by the roller 80. At this time, the secondary transfer roller 80 is pressed against the intermediate transfer belt 70 and a secondary transfer voltage (secondary transfer bias) is applied.

The full-color toner image transferred to the recording medium P is heated and pressurized by the fixing device 90 and fused to the recording medium P. Thereafter, the recording medium P is discharged to the outside of the image forming apparatus 10 by the discharge roller pair 87.
On the other hand, after the primary transfer position has elapsed, the toner adhering to the surface of the photoconductor 20 is scraped off by the cleaning blade 76 of the cleaning unit 75 to prepare for charging for forming the next latent image. The toner that has been scraped off is collected by a residual toner collecting section in the cleaning unit 75.

  In the case of forming an image on both sides of the recording medium, the recording medium P fixed on one side by the fixing device 90 is once sandwiched between the discharge roller pair 87, and then the discharge roller pair 87 is driven in reverse. By driving the conveyance roller pair 88A, 88B, the recording medium P is turned upside down through the conveyance path 88C and returned to the secondary transfer roller 80, and an image is printed on the other surface of the recording medium P by the same operation as described above. Form.

≪Fixing device≫
Here, the fixing device 90 will be described in detail with reference to FIGS.
As shown in FIG. 3, the fixing device 90 includes a pair of a fixing roller 91 and a pressure roller 92 that are pressed against each other, a heater 93 for heating the fixing roller 91, and the temperature of the fixing roller 91 in a non-contact manner. A non-contact temperature sensor 94 to be detected; a separating member 95 for separating the recording medium after fixing from the fixing roller 91; and a cover member 96 that covers a part of each peripheral surface of the fixing roller 91 and the pressure roller 92; have.

In such a fixing device 90, a recording medium carrying an unfixed image is conveyed to the nip portion N from below in FIG. 3 with respect to the nip portion N formed by pressure contact between the fixing roller 91 and the pressure roller 92. Then, the unfixed image is fixed on the recording medium by heating and pressurizing the recording medium. In the present embodiment, the recording medium conveyed to the nip portion N carries an unfixed image on the fixing roller 91 side.
The fixing roller 91 has a cylindrical shape and is rotatable around its axis.

Further, as shown in FIG. 3, the fixing roller 91 includes a cylindrical metal base (core metal) 911, an elastic layer 912 that covers the outer peripheral surface of the base, and a release layer that covers the outer peripheral surface of the elastic layer. 913.
In such an internal space of the fixing roller 91, a heater 93 such as a halogen heater is disposed. Thereby, the fixing roller 91 is heated, and the recording medium passing through the nip portion N can be heated.

The pressure roller 92 has a cylindrical shape or a columnar shape, is rotatable about its axis, and is in pressure contact with the fixing roller 91.
The pressure roller 92 includes a cylindrical metal base (core) 921, an elastic layer 922 that covers the outer peripheral surface of the base, and a release layer 923 that covers the outer peripheral surface of the elastic layer. Yes.
Such a fixing roller 91 and a pressure roller 92 are rotatably supported by a cover member 96.

As shown in FIG. 4, the non-contact temperature sensor 94 for detecting the surface temperature of the fixing roller 91 includes a substrate 941, a thermopile 942 provided on one surface of the substrate 941, and a thermopile 942. It has a light guide tube 943 attached to the substrate so as to surround, and a light collecting lens 944 that seals the opening at the tip of the light guide tube 943.
When such a non-contact temperature sensor 94 receives infrared rays emitted from the fixing roller 91, it generates a thermoelectromotive force according to the amount of energy and can detect the absolute amount (temperature) of the energy. Thereby, a temperature measurement error due to a displacement of the attachment position of the non-contact temperature sensor 94 is hardly generated, and the temperature detection responsiveness is excellent. Thereby, the non-contact temperature sensor 94 can exhibit excellent reliability, and can detect the surface temperature of the fixing roller 91 more accurately.

Based on the surface temperature of the fixing roller 91 detected by the non-contact temperature sensor 94, the driving of the heater 93 described above is controlled by a control means (not shown) so that the outer surface of the fixing roller 91 becomes the target temperature. As a result, the fixing device 90 can exhibit excellent fixing characteristics.
The non-contact temperature sensor 94 is not particularly limited as long as it can detect the surface temperature of the fixing roller 91 in a non-contact manner. For example, a non-contact type thermistor may be used. Further, even a sensor having a thermopile is not limited to the present embodiment. For example, instead of the light collecting lens 944, a light transmissive glass plate or a plastic plate may be used. May be omitted and an opening may be provided.

  As shown in FIG. 3, the cover member 96 that rotatably supports the fixing roller 91 and the pressure roller 92 fixes the recording medium P and a recording medium inlet 961 for carrying the recording medium P into the nip portion N. And a recording medium discharge port 962 for discharging from the apparatus 90. Further, the cover member 96 has an opening 963, and a non-contact temperature sensor 94 is disposed in the vicinity of the opening 963 so that the fixing roller 91 and the light collecting lens 944 face each other.

Further, a space 98 is defined by the inner wall of the cover member 96 and the outer peripheral surface of the fixing roller 91.
Such a cover member 96 is preferably detachable from the duct 97. Thereby, the cover member 96 can be easily removed from the main body case 11. As a result, maintenance such as replacement of the fixing roller 91 is facilitated.

  As shown in FIG. 3, the space 98 is defined by the inner wall surface of the cover member 96 and the outer peripheral surface of the fixing roller 91, and is formed so that gas is introduced from the opening 963 and discharged from the recording medium discharge port 962. Yes. As a result, gas can be circulated in the space between the non-contact temperature sensor 94 and the fixing roller 91, and the toner floating in the cover member 96 and the toner adhering to the fixing roller 91 are generated by the heat generated by the heater 93. Thus, it is possible to effectively prevent the vaporized material or the like (hereinafter also simply referred to as “floating toner” or the like) vaporized due to the adhesion of the light collecting lens 944. As a result, the reliability of the non-contact temperature sensor 94 is improved, and the fixing device 90 can exhibit excellent fixing characteristics. Further, the life of the non-contact temperature sensor 94 can be extended.

  Further, since the gas flowing through the space 98 is configured to be discharged from the recording medium discharge port 962, the exhaust duct 13 formed so as to cover the upper side of the recording medium discharge port 962 is connected to the inside of the cover member 96. It is possible to circulate toner that floats on the surface. That is, toner or the like floating in the cover member 96 can be removed from the cover member 96. Thereby, it is possible to more effectively prevent toner or the like floating in the cover member 96 from adhering to the surface of the light collecting lens 944.

Further, the gas flows from the opening 963 (near the non-contact temperature sensor 94) toward the downstream side of the nip portion N in the recording medium conveyance direction, whereby the gas flows to the upstream side of the nip portion N in the recording medium conveyance direction. This can prevent the unfixed image carried on the recording medium conveyed to the nip portion N from being disturbed by the air current. As a result, the fixing device 90 can prevent image unevenness from occurring.
Such a gas flow can be generated by the fan 14 provided in the exhaust duct 13 as described above. As a result, the gas is introduced into the space 98 from the opening 963 and discharged from the recording medium discharge port 962. As a result, it is possible to prevent the toner floating in the cover member 96 from adhering to the surface of the light collecting lens 944.
If the gas can be circulated from the vicinity of the non-contact temperature sensor 94 toward the downstream side in the recording medium conveyance direction of the nip portion N, the arrangement position of the fan 14 and the shape of the exhaust duct 13 are the same as those in the present embodiment. It is not limited.

The aforementioned duct 97 is connected to the opening 963 of the cover member 96 as described above, as shown in FIG.
Specifically, as shown in FIG. 3, the duct 97 has a tip 971 on the downstream side in the gas flow direction so that the cross-sectional area of the flow path in the duct 97 gradually decreases from the upstream side to the downstream side in the gas flow direction. Is formed. Thereby, the flow velocity of the gas flowing from the opening 963 to the space 98 can be increased. In other words, the flow velocity of the gas flowing through the space between the non-contact temperature sensor 94 and the fixing roller 91 can be increased. Thereby, it is possible to effectively prevent toner floating in the cover member 96 from adhering to the surface of the light collecting lens 944.

  Further, the duct 97 is formed so that the front end portion 971 faces the downstream side of the nip portion N in the recording medium conveyance direction. Thereby, the gas can be circulated from the vicinity of the non-contact temperature sensor 94 toward the downstream side of the nip portion N in the recording medium conveyance direction. As a result, it is possible to effectively prevent toner floating in the cover member 96 from adhering to the light collecting lens 944. Further, by forming the leading end portion 971 in this way, the recording medium conveyance of the nip portion N can be performed more smoothly from the opening 963 (in the vicinity of the non-contact temperature sensor 94) without opposing the gas flow generated by the fan 14. Gas can be circulated downstream in the direction.

On the other hand, the opening on the upstream side in the gas flow direction of the duct 97 is arranged so as to be connected to the air inlet 112 formed in the main body case 11. Thereby, the gas (air) outside the main body case 11 can be circulated through the duct 97. That is, it is possible to prevent the gas including the toner floating in the main body case 11 from flowing through the duct 97.
Thus, by having the duct 97 installed outside the cover member 96 and arranged to communicate with the opening 963, a gas flow path can be formed, and the space 98 can be efficiently formed from the opening 963. It is possible to circulate gas. Further, since the duct 97 is provided so as to communicate the opening 963 and the intake port 112, it is possible to prevent an unnecessary air flow from being generated inside the main body case 11, and the image forming apparatus 10 is stable. Driving can be performed.

Furthermore, it is preferable to provide a filter in the duct 97 (not shown). Thereby, the dust etc. which the gas which distribute | circulates the inside of the duct 97 contains can be removed more reliably, and the gas which does not contain the suspended | floating matter can be more circulated toward the space 98 from the opening 963.
Note that the shape of the duct 97 is not limited to this embodiment, and for example, the duct 97 may not have a portion where the cross-sectional area gradually decreases, such as the tip portion 971. The duct 97 may be the image forming apparatus 10. This can be omitted depending on the arrangement of internal devices.

  As described above, the fixing device 90 according to the present embodiment causes the gas to flow from the opening 963 (in the vicinity of the non-contact temperature sensor 94) toward the downstream side in the recording medium conveyance direction of the nip portion N, thereby covering the cover member. The toner floating in 96 is prevented from adhering to the surface of the light collecting lens 944. Thereby, the reliability of the non-contact temperature sensor 94 is improved, and the fixing device 90 can exhibit excellent fixing characteristics.

  However, if the gas outside the main body case 11 is introduced into the space 98 at the same temperature, the surface temperature of the fixing roller 91 becomes higher than the temperature of the gas flowing through the space 98. Among them, there is a possibility that the surface temperature of the portion in contact with the airflow is partially lowered to cause unevenness in the surface temperature, resulting in a problem that the fixing characteristics of the fixing device 90 deteriorate.

  Therefore, the fixing device 90 according to the present embodiment has a heating unit that preheats the gas introduced into the space 98, thereby reducing the temperature difference between the gas and the surface of the fixing roller 91. A partial temperature drop on the surface of the fixing roller 91 can be prevented. As a result, the fixing device 90 can achieve both the excellent reliability of the non-contact temperature sensor 94 and the uniformity of the surface temperature of the fixing roller 91. Therefore, the fixing device 90 can exhibit excellent fixing characteristics for many years.

  Such a heating means is configured to heat the gas flowing through the duct 97. As a result, the heated gas flows through the space 98 from the opening 963 (in the vicinity of the non-contact temperature sensor 94) toward the downstream side of the nip portion N in the recording medium conveyance direction. The temperature difference between the temperature and the surface temperature of the fixing roller 91 can be reduced. As a result, a partial decrease in the surface temperature of the fixing roller 91 can be suppressed, and the fixing device 90 can exhibit excellent fixing characteristics.

In the present embodiment, the heating means is configured to heat the gas flowing through the duct 97 using heat generated from the heater 93. Thereby, it is not necessary to use a new heat source, and a reduction in manufacturing cost and power consumption can be achieved.
Specifically, the cover member 96 has a heat radiating member 99 that heats the gas flowing through the duct 97. Here, the heat radiating member 99 is formed integrally with the cover member 96 as shown in FIG. Thereby, since the number of parts can be reduced, the design can be simplified and the manufacturing cost can be reduced. In addition, the heat radiating member 99 and the cover member 96 may be formed separately.

  As shown in FIG. 3, the heat dissipating member 99 is disposed so as to cover a part of the fixing roller 91 in which the heater 93 is built, and through the gas (air) between the fixing roller 91 and the heat dissipating member 99, Heat generated from the heater 93 can be received. By releasing the heat thus received into the duct 97, the gas is heated. Thereby, the gas in the duct 97 can be efficiently heated using the heat generated from the heater 93. In addition, since the configuration can be simplified, the manufacturing cost can be reduced.

  A duct 97 is formed along the heat dissipating member 99. Thereby, since the gas in the duct 97 flows along the heat radiating member 99, the gas in the duct 97 can be effectively heated by the heat received from the heater 93. As a result, the temperature difference between the temperature of the gas flowing in the space 98 and the surface temperature of the fixing roller 91 can be relaxed, and a partial temperature drop (temperature unevenness) on the surface of the fixing roller 91 can be prevented. Therefore, the fixing device 90 can achieve both the excellent reliability of the non-contact temperature sensor 94 and the uniformity of the surface temperature of the fixing roller 91. As a result, the fixing device 90 can exhibit excellent fixing characteristics for many years.

  The constituent material of the heat dissipating member 99 is not particularly limited, but it is preferable that the constituent member is composed mainly of a material having excellent thermal conductivity. Thereby, the heat radiating member 99 can receive more heat and further warm the gas in the duct 97. As a result, a partial temperature drop on the surface of the fixing roller 91 can be prevented, and the fixing device 90 can exhibit excellent fixing characteristics.

The material having such excellent thermal conductivity is not particularly limited. For example, a metal such as Mg, Al, Fe, Ni, Cu, Ti, Zn, Ag, or Au (a simple metal), or these metals. And alloys containing these metals, oxides and nitrides containing these metals, and the like.
Among these, as the high thermal conductivity material, metal materials such as aluminum, copper, titanium, and stainless steel, and ceramic materials such as aluminum nitride and silicon nitride are preferable.

  In the present embodiment, the heat radiating member 99 receives heat generated from the heater 93 through the gas between the fixing roller 91. However, if the heat generated from the heater 93 can be received, For example, the heat radiating member 99 may receive heat generated from the heater 93 by being disposed so that the heat radiating member 99 and the fixing roller 91 are in contact with each other.

  Here, the non-contact temperature sensor 94 is configured to detect the temperature of the surface of the fixing roller 91 without being affected by the temperature of the heated gas flowing through the duct 97 and the space 98. Thereby, the temperature change of non-contact temperature sensor 94 itself can be suppressed, and the reliability of non-contact temperature sensor 94 improves. As a result, the fixing device 90 can exhibit excellent fixing characteristics.

  Specifically, as shown in FIG. 3, the non-contact temperature sensor 94 is disposed outside the duct 97 and outside the space 98. In other words, the non-contact temperature sensor is disposed so as not to contact a heated gas stream flowing from the duct 97 to the space 98. Thereby, the temperature of the surface of the fixing roller 91 can be detected without being affected by the temperature of the heated gas flowing from the duct 97 to the space 98. As a result, the temperature change of the non-contact temperature sensor 94 itself can be suppressed, the reliability of the non-contact temperature sensor 94 is improved, and the fixing device 90 can exhibit excellent fixing characteristics.

  However, if the non-contact temperature sensor 94 can detect the temperature of the surface of the fixing roller 91 without being affected by the temperature of the heated gas flowing through the duct 97 and the space 98, the present invention is limited to this embodiment. For example, the non-contact temperature sensor 94 is also heated by circulating from the duct 97 to the space 98 by covering the non-contact temperature sensor 94 with a heat insulating material or the like while allowing infrared light from the light collecting lens 944 to enter. It is possible to detect the temperature of the surface of the fixing roller 91 without being affected by the temperature of the gas that has been generated.

  Further, the non-contact temperature sensor 94 is disposed so that the surface temperature of the fixing roller 91 can be detected from the outside of the cover member 96 through the opening 963. This prevents the toner floating in the cover member 96 or the toner adhering to the surface of the fixing roller 91 from adhering to the surface of the light collecting lens 944 due to vaporization caused by heat generated from the heater 93. Can do. As a result, the reliability of the non-contact temperature sensor 94 is improved, and the fixing device 90 can exhibit excellent fixing characteristics. Further, the life of the non-contact temperature sensor 94 can be extended.

Further, as shown in FIG. 6, the non-contact temperature sensor 94 detects the surface temperature in the vicinity of the center in the axial direction of the fixing roller 91 (that is, the sheet passing region in the present embodiment). As long as the surface temperature of the fixing roller 91 can be detected, the position where the non-contact temperature sensor 94 is disposed, the surface temperature detection portion of the fixing roller 91, and the like are not particularly limited.
The cover member 96 is preferably disposed so as to be detachable from the non-contact temperature sensor 94. For example, since the non-contact temperature sensor 94 is disposed in the main body case 11, when replacing the fixing device 90, the non-contact temperature sensor 94 can be removed to reuse the non-contact temperature sensor 94, or the non-contact temperature sensor 94 can be removed simultaneously. Costs can be reduced because they do not need to be replaced.

  In the present embodiment, the opening 963 detects the surface temperature of the fixing roller 91 by the non-contact temperature sensor 94 and gas flows in the space between the non-contact temperature sensor 94 and the fixing roller 91. However, the present invention is not limited to this, and the opening for detecting the surface temperature of the fixing roller 91 by the non-contact temperature sensor 94 and the gas for the non-contact temperature sensor 94 and the fixing roller 91 are described. And an opening for circulating in the space between them may be formed separately.

Second Embodiment
A second embodiment of the present invention will be described with reference to FIG. Hereinafter, the second embodiment will be described with a focus on differences from the first embodiment described above, and description of similar matters will be omitted.
FIG. 7 is a diagram for explaining the shape of the heat dissipation member of the present embodiment.
The fixing device 90A of the present embodiment is the same as the fixing device of the first embodiment except that the shape of the heat dissipation member 99A is different.

The heat dissipating member 99A according to the present embodiment has a plurality of protrusions 991A protruding from the wall surface toward the inside of the duct 97A. Thereby, the contact area of 99 A of heat radiating members and gas can be enlarged, and gas can be heated more efficiently. As a result, a partial temperature drop on the surface of the fixing roller 91 can be prevented.
Furthermore, the protrusion 991A extends in the gas flow direction. Thereby, a surface area with gas can be enlarged and gas can be heated more efficiently. Further, the protrusion 991A also functions as a rectifying plate, and allows gas to flow through the duct 97A more smoothly.
Also in the second embodiment as described above, the same effect as that of the first embodiment described above can be obtained.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to this.
For example, each unit constituting the image forming apparatus of the present invention can be replaced with any one that exhibits the same function, or other configurations can be added.
In the above-described embodiments, the fixing member using the fixing roller has been described. However, the present invention is not limited to this. For example, a fixing belt may be used.
Similarly, in the above-described embodiment, a description has been given of a case where a pressure roller is used as a pressure member. However, the present invention is not limited to this, and may be a pressure belt, for example.

1 is a schematic cross-sectional view of an overall configuration showing an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic longitudinal sectional view of the image forming apparatus shown in FIG. 1. FIG. 2 is a schematic cross-sectional view illustrating a preferred embodiment of a fixing device provided in the image forming apparatus illustrated in FIG. 1. It is typical sectional drawing of a non-contact temperature sensor. It is a schematic diagram which shows the positional relationship of an exhaust duct and a fixing device. FIG. 3 is a schematic cross-sectional view of a fixing device. It is a figure for demonstrating the shape of the heat radiating member concerning 2nd Embodiment of this invention.

Explanation of symbols

  10. Image forming device 11 Main body case 111 ... Exhaust port 112 ... Intake port 13 ... Exhaust duct 14 ... Fan 20 ... Photoconductor 30 ... Charge unit 40 ... ... Exposure unit 50 ... Development unit 50a ... Axis 51 ... Black development device 52 ... Magenta development device 53 ... Cyan development device 54 ... Yellow development device 55 ... Holding body 55a ... 55d ... Holding section 60 ... Primary transfer roller 61 ... Intermediate transfer body 70 ... Intermediate transfer belt 71 ... Drive roller 72 ... Follower roller 73 ... Substrate 75 ... Cleaning Unit 76 ... Cleaning blade 80 ... Secondary transfer roller 82 ... Paper feed tray 84 ... Paper feed roller 86 ... Registration roller 87 ... Discharge roller pair 88 ... Conveyance section 88A, 88B ... Conveyance roller pair 88C ... Conveyance path 90, 90A ... Fixing device 91 ... Fixing roller 92 ... Pressure rollers 911, 921 ... Base (core) 912, 922 ... Elastic layer 913, 923 ... Release layer 93 ... Heater 94 ... Non-contact temperature sensor 941 ... Base 942 ... Thermopile 943 ... ································································································································· ··· Duct 971 · · · Tip 98 · · · Space 99, 99A · · · Heat dissipation member 991A · · · Projection N · · · Nip portion P · · · Recording medium T · · · Toner (developer)

Claims (15)

A fixing member and a pressure member that rotate in pressure contact with each other, and a heater that heats the fixing member, and an unfixed image including toner is formed in a nip formed by the pressure contact between the fixing member and the pressure member. A fixing device for fixing the unfixed image to the recording medium by passing the recording medium carried thereon and heating and pressurizing the recording medium;
A non-contact temperature sensor provided in the vicinity of the fixing member for detecting the surface temperature of the fixing member in a non-contact manner;
It is configured to prevent the toner floating in the space from adhering to the non-contact temperature sensor by flowing gas through the space between the non-contact temperature sensor and the fixing member. A fixing device characterized.   The fixing device according to claim 1, wherein the gas is circulated from the vicinity of the non-contact temperature sensor toward the fixing member.   The fixing device according to claim 1, wherein the gas is circulated from a vicinity of the non-contact temperature sensor toward a downstream side of the nip portion in a conveyance direction of the recording medium. The unfixed image including a fixing member and a pressure member that rotate in pressure contact with each other, and a heater that heats the fixing member, and including toner in a nip portion formed by pressure contact between the fixing member and the pressure member. A fixing device for fixing the unfixed image to the recording medium by passing the recording medium carrying the image and heating and pressurizing the recording medium,
A cover member disposed so as to cover at least a part of the outer periphery of the fixing member and having an opening;
A non-contact temperature sensor provided in the vicinity of the opening and detecting the surface temperature of the fixing member in a non-contact manner;
By introducing and circulating gas from the opening to a space defined by the inner wall of the cover member and the outer peripheral surface of the fixing member, the toner floating in the space adheres to the non-contact temperature sensor. A fixing device configured to prevent the occurrence of the fixing.   The fixing device according to claim 4, wherein the gas is circulated from the opening portion toward the downstream side in the conveyance direction of the recording medium with respect to the nip portion.   The fixing device according to claim 4, further comprising a duct that is installed outside the cover member and communicates with the opening, and gas is introduced into the opening through the duct.   The fixing device according to claim 6, further comprising a heating unit that heats the gas in the duct so as to reduce a temperature difference between the gas in the duct and the surface of the fixing member.   The fixing device according to claim 7, wherein the heating unit heats the gas in the duct using heat generated from the heater.   The fixing device according to claim 8, wherein the heating unit includes a heat radiating member that transfers heat generated from the heater and dissipates heat in the duct.   The fixing device according to claim 9, wherein the heat radiating member is formed integrally with the cover member.   The fixing device according to claim 9, wherein the heat dissipating member has a plurality of protrusions protruding into the duct.   The fixing device according to claim 1, wherein the non-contact temperature sensor has a thermopile.   The fixing device according to claim 1, wherein the non-contact temperature sensor is configured to perform temperature detection without being affected by the temperature of the gas.   The fixing device according to claim 4, wherein the non-contact temperature sensor is disposed outside the cover member and detects a surface temperature of the fixing member through the opening. 15. An image forming apparatus for forming an image on a recording medium by a series of image forming processes including exposure, charging, transfer, and fixing, the image forming apparatus comprising the fixing device according to claim 1. Forming equipment.

Images